Meteor Showers

Gary W. Kronk

Meteor Showers

An Annotated Catalog Second Edition

The Patrick Moore The Patrick Moore Practical Astronomy Series

For further volumes: http://www.springer.com/series/3192

Meteor Showers

An Annotated Catalog

Gary W. Kronk

Second Edition Gary W. Kronk Hillsboro , MO , USA

ISSN 1431-9756 ISBN 978-1-4614-7896-6 ISBN 978-1-4614-7897-3 (eBook) DOI 10.1007/978-1-4614-7897-3 Springer New York Heidelberg Dordrecht London

Library of Congress Control Number: 2013948919

© Springer Science+Business Media New York 1988, 2014 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifi cally the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfi lms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied speci fi cally for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher’s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a speci fi c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.

Printed on acid-free paper

Springer is part of Springer Science+Business Media (www.springer.com) This book is dedicated to my wife and best friend, Kathy.

About the Author

Gary W. Kronk received his Bachelor of Science in Journalism from Southern Illinois University in Edwardsville. He is employed at Laclede Gas in St. Louis, where he is a Senior User Support Specialist and occasionally teaches classes on software programs. Observing, researching, and writing about comets has been an activity the author has participated in for most of his life, with over 3,000 observations of over 210 comets. He is the author of seven books and has published in Sky & Telescope , Astronomy , Icarus , The Journal of the Association of Lunar and Planetary Observers, and more. His books include Comets: A Descriptive Catalog (Enslow Publishers, 1984), Meteor Showers (Enslow, 1988), and a six-volume series titled “Cometography” with Cambridge University Press, whose ﬁ fth volume was published in 2010. In 2004, the International Astronomical Union’s Minor Planet Center announced that minor planet number 48300 was being given the name “Kronk” in honor of the author’s extensive research for his Cometography series.

vii

Preface

This book contains both historical and current data on what the author believes to be the most active meteor showers in the sky. Data from the majority of the visual, photographic, video, and radar studies have been utilized. The author began his research in the late 1970s with in-depth investigations into the observations of several major meteor showers, such as the Perseids, Geminids, Orionids, and Eta Aquarids. This ultimately took the author in a new direction that led to the creation of a preliminary list of over 600 potential meteor showers. Using photographic and radar data, the author determined the orbit of each potential meteor stream. When such data was not available, the author calculated parabolic orbits for the streams. The next stage was to establish the probable daily movement of each meteor stream’s radiant across the sky (also known as the radiant ephemeris). Dozens of radiant lists published during the nineteenth and twentieth centuries, as well as lists of photographic and radar meteor orbits were then compared to each preliminary radiant ephemeris of each potential meteor shower. Finally, the “D-criterion” was applied to the potential matches, which ultimately determined the history of each stream, the actual duration, the actual radiant ephemeris, and the orbit. This analysis ﬁ rst began on a CDC Cyber 90 mainframe at Southern Illinois University in Edwardsville (Illinois, USA) in 1980. Work continued on an Atari 800 home computer (48 K RAM) in 1982 and a Macintosh (512 K and 1 M RAM) from 1985 to 1987. To update the ﬁ rst edition of this book, some of this same analysis was repeated during the last 2 years using an Apple iMac computer with an 8 GB RAM running both Apple OS X and Microsoft Windows 7.

ix x Preface

The meteor showers chosen to be included in this book are here for one or more of the following four reasons: 1. They are among the strongest showers. 2. They have been known for a long time. 3. They have had support from at least two very reliable and methodical surveys. 4. They are particularly interesting. Obviously, the fi nal decision on what stayed and what was taken out was purely the decision of the author and, admittedly, some weak meteor showers that met some of these criteria were left out because of lack of space. This book is divided into 12 chapters, with each chapter covering a month of the year. Meteor showers are included in the month that they reach maximum and are listed alphabetically according to their constellation name. For each meteor shower, the author has presented what may be the fi rst observations, additional observations, and the orbit. For well-observed meteor showers, the author has also included the duration of activity, date of peak activity, average radiant position, and many additional details. There are a couple of showers that have a maximum which can fall on either the last day of one month or the fi rst day of the next month (the Delta Aquariids are one example), but the author has dealt with this by placing the shower in the chapter containing the earliest date of maximum. For the fi rst edition of this book, the author adopted either the most commonly used name or, on occasion, the most appropriate name for each shower. Since the writing of that edition, the International Astronomical Union has adopted new names for some meteor showers. Subsequently, some meteor showers in the fi rst edition have been renamed in this edition. Although the month, day, and year are given in the discussion of every meteor shower, the actual time is rarely given, except in the case of unusual events, such as outbursts of meteors. When the time is provided, it is handled in one of two ways throughout this book: local time or universal time. Both of these times are mostly used in the case of outbursts. The local time is usually only used during the eighteenth, nineteenth, and early twentieth centuries. It is the time the observer records by looking at a timepiece of some type. Outbursts are usually events of very short duration, so the author chose to just use the local time to give the reader a better sense of the situation. For example, the discussion of the 1833 outburst of the Leonids mostly discusses the observations along the east coast of the United States, because this is where the bulk of the observations were made at the peak. Throughout the text, the local time is identi fi ed as times that are followed by “a.m.” or “p.m.” Universal time was adopted by the International Astronomical Union in 1935 and became the standard for astronomical observations. It is the result of taking the local time and adding or subtracting the number of hours between the time zone of the observer and the Greenwich meridian. Observations in universal time are listed in two different ways throughout the book, depending on the situation. If you read that an observer saw 30 meteors on “2005 August 12 from 20:05 to 21:05,” this is Preface xi simply indicating the hour and minutes in universal time (always in the 24-h for- mat) that 30 meteors were seen. If you read a date such as “1999 November 18.01,” this is the result of the hours and minutes in universal time being divided by 24 h to get the decimal day. These two methods of displaying universal time exist in this book because that is the way they were reported. Another important piece of information when dealing with observations is the number of meteors seen. The most common way to express this number is “meteors per hour,” also called the “hourly rate.” These two phrases are used throughout the book and provide the reader with a sense of what was actually seen. For analysis purposes, astronomers use a formula to convert the hourly rate to the “zenithal hourly rate,” which is abbreviated as ZHR. This value allows astronomers to compare the observations from a wide variety of people, as the formula considers the sky conditions at each location, the altitude of the radiant at the time of the observation, the amount of unobstructed sky (i.e., free of trees and buildings), observer perception, and other factors. Although it would be desirable to have just converted all observations in the book to ZHRs, observer accounts do not always provide all of the necessary information to calculate this value. In fact, the equation to determine the ZHR of an observation has evolved over the years, and older ZHRs mentioned in the book may not be 100 % comparable to later ZHRs. Once again, the information necessary to convert old reported ZHRs to newer values was not available. So, in short, it was thought best not to alter the published values. Speaking of not wanting to alter published values, this also goes for the published positions of radiants. Although it was briefl y considered to convert all positions to equinox 2000, the author realized that few, if any, visually established radiants would be considered as precise, and this makes up the bulk of the observations presented in this book. The conversion of low precision data is never a good idea, so the radiants are listed as they were published. There are some Greek letters that are used in this book that need some explanation for people who are not regular observers of meteor showers. They are as follows: α and δ : Right ascension and Declination. These always go together and represent the coordinates of a meteor shower radiant. Although the standard way to indicate α has always been in hours and minutes in every other aspect of astronomy, meteor astronomy adopted to display it in degrees long ago and this has never changed. Occasionally, these two characters might appear in the book as part of a star name. λ: Solar longitude. This measure is in degrees. It is a handier way to demonstrate when events happen in meteor astronomy. Because of leap years, a meteor shower like the Perseids might occur on August 13 in 1 year and August 12 in the next year; however, the solar longitude will be 140.0¡ in both years. The solar longitude makes it possible to determine the future date of a meteor shower’s peak.

Hillsboro, MO, USA Gary W. Kronk

Acknowledgments

I wish to express my gratitude and appreciation to those people around the world who helped me in some way during the writing of both the ﬁ rst and second editions of this book in the last four decades. Thanks go Rainer Arlt (Germany), Jack Baggaley (New Zealand), Hans Betlem (the Netherlands), Peter G. Brown (Canada), Marc de Lignie (the Netherlands), Jack D. Drummond (United States), Ichiro Hasegawa (Japan), Dmitrij Lupishko (Ukraine), Robert Lunsford (United States), Alastair McBeath (United Kingdom), Sirko Molau (Germany), Katsuhito Ohtsuka (Japan), Andrew A. Pearce (Australia), Ian Reid (Australia), Jürgen Rendtel (Germany), Paul Roggemans (Belgium), Jonathan D. Shanklin (United Kingdom), Christian Steyaert (Belgium), Richard Taibi (United States), István Tepliczky (Hungary), Alexandra K. Terentjeva (Russian Federation), Josep M. Trigo-Rodríguez (Spain), Gareth Williams (United States), Jeff Wood (Australia), and Joel Younger (Australia) for sharing observations, participating in a variety of discussions, helping with calculations, and/or sending me papers they had written. Thanks go to Zdenek Sekanina (Jet Propulsion Laboratory, California, USA) and Carl Murray (Queen Mary College, England) for helping me to acquire the 39,145 radio meteor orbits determined by Sekanina during the Radio Meteor Project which formed an important base as I wrote the ﬁ rst edition of this book during the early 1980s. Thanks go to the librarians who went above and beyond what was asked of them. Sybil Csigi (University of Pennsylvania, USA) sent most of the American Meteor Society publications published between 1930 and 1968. Betty Eickhoff (Washington University, Missouri, USA) allowed me special privileges in the use of the university’s physics library. All of the librarians at Linda Hall Library in Kansas City (Missouri, USA) were amazing ever since I began traveling there in the late 1970s.

xiii xiv Acknowledgments

Thanks go to those individuals who helped translate some of the more difﬁ cult documents I had to deal with. These include Cathy Schaewe and Mary Teissier du Cros for French translations, Maik Meyer for German translations, and Pavel Nikiforovitch for Russian translations. Special thanks go to Ruth Armes and Pete Simpson (Southern Illinois University, Edwardsville) for their initial encouragement in getting the ﬁ rst edition of this book published. My greatest appreciation has to go to my wife, Kathy. She was patient and yet encouraging as I worked on this second edition. She also acted as an editor, catching my silly mistakes as a result of long nights of writing. I can’t begin to thank her for all she does every single day. Contents

1 Introduction ...... 1 2 January Meteor Showers...... 15 Zeta Aurigids ...... 15 January Boötids ...... 16 Lambda Boötids ...... 18 Delta Cancrids: Antihelion ...... 19 Canum Venaticids ...... 21 Eta Carinids ...... 22 Theta Coronae Borealids ...... 22 Xi Coronae Borealids ...... 24 January Draconids ...... 24 Rho Geminids: Antihelion ...... 25 Alpha Hydrids ...... 27 Alpha Leonids: Antihelion ...... 27 January Leonids ...... 29 Quadrantids ...... 30 Daytime Xi Sagittariids ...... 38 January Xi Ursae Majorids ...... 39 Gamma Ursae Minorids ...... 40 Gamma Velids ...... 40 3 February Meteor Showers ...... 45 Alpha Antliids ...... 45 Aurigids ...... 46 Daytime Capricornids-Sagittariids ...... 48 Daytime Chi Capricornids ...... 49

xv xvi Contents

Alpha Centaurids ...... 50 February Eta Draconids ...... 51 Delta Leonids: Antihelion ...... 51 4 March Meteor Showers ...... 55 Daytime Kappa Aquariids ...... 55 March Eta Draconids ...... 56 x Herculids ...... 58 Kappa Leonids ...... 58 Delta Mensids ...... 60 Gamma Normids ...... 61 5 April Meteor Showers ...... 65 April Rho Cygnids ...... 65 Tau Draconids ...... 66 Lyrids ...... 67 Delta Pavonids ...... 75 Daytime April Piscids ...... 76 Pi Puppids ...... 78 April Ursids ...... 80 Virginid Complex: Antihelion ...... 81 6 May Meteor Showers ...... 89 Eta Aquariids ...... 89 Epsilon Aquilids...... 94 Daytime Epsilon Arietids ...... 95 Daytime May Arietids ...... 96 Daytime Omicron Cetids ...... 97 Eta Lyrids ...... 99 Daytime May Piscids ...... 100 7 June Meteor Showers...... 105 June Aquilids ...... 105 Daytime Arietids ...... 106 June Boötids (“Pons-Winneckids”) ...... 109 Corvids ...... 114 Gamma Draconids ...... 116 Tau Herculids ...... 117 June Lyrids ...... 121 Epsilon Perseids ...... 124 Daytime Zeta Perseids ...... 124 Sagittariids ...... 126 Scorpiid-Sagittariid Complex: Antihelion ...... 127 June Scutids ...... 133 Daytime Beta Taurids...... 134 Daytime Lambda Taurids ...... 136 Contents xvii

8 July Meteor Showers ...... 141 c Andromedids ...... 141 Delta Aquariids ...... 142 Cassiopeiids ...... 150 Zeta Cassiopeiids ...... 156 July Gamma Draconids ...... 157 Beta Equuleids ...... 158 Alpha Lacertids ...... 159 Alpha Lyrids ...... 160 Daytime Xi Orionids ...... 161 Epsilon Pegasids ...... 162 July Pegasids ...... 162 July Phoenicids ...... 163 Phi Piscids ...... 165 Piscis Austrinids...... 165 9 August Meteor Showers ...... 171 Iota Aquariids: Antihelion ...... 171 Alpha Capricornids ...... 177 Kappa Cygnids ...... 183 August Eridanids ...... 186 Daytime Gamma Leonids ...... 188 Perseids ...... 188 10 September Meteor Showers ...... 207 Gamma Aquariids ...... 207 Alpha Aurigids ...... 209 Daytime Zeta Cancrids ...... 211 Eta Draconids ...... 212 Daytime Kappa Leonids ...... 212 September Perseids ...... 213 Piscids: Antihelion ...... 216 Gamma Piscids ...... 218 Daytime Sextantids ...... 220 Alpha Triangulids ...... 222 11 October Meteor Showers ...... 227 October Arietids ...... 227 Delta Aurigids ...... 229 Eta Cetids ...... 232 October Cetids ...... 233 October Cygnids ...... 235 Draconids (“Giacobinids”) ...... 236 Epsilon Geminids ...... 241 Orionids ...... 244 October Ursae Majorids ...... 251 xviii Contents

12 November Meteor Showers ...... 257 Andromedids (“Bielids”) ...... 257 November Theta Aurigids ...... 266 Omicron Eridanids ...... 267 Leonids ...... 269 Alpha Monocerotids ...... 284 Alpha Pegasids ...... 288 Taurids ...... 290 Chi Taurids ...... 298 13 December Meteor Showers ...... 305 Delta Arietids ...... 305 11 Canis Minorids ...... 307 Coma Berenicids ...... 309 December Alpha Draconids ...... 312 December Kappa Draconids ...... 312 Geminids ...... 313 Sigma Hydrids ...... 324 December Monocerotids ...... 326 Chi Orionids ...... 329 Phoenicids ...... 334 Alpha Puppids ...... 337 Sigma Serpentids ...... 338 Psi Ursae Majorids ...... 339 Ursids ...... 339 December Chi Virginids and December Sigma Virginids ...... 344

Glossary ...... 351

Index ...... 355 Chapter 1

Introduction

Few astronomers occupy themselves with the observation and investigation of meteors, and yet it is an attractive ﬁ eld of work offering inviting prospects of new discoveries W. F. Denning 1

The attempt to understand the nature of meteors extends back thousands of years; however, the lack of knowledge of what lay beyond Earth, not to mention science in general, initially brought about some fanciful ideas. A few of these follow: • The Chinese believed meteors were messengers from heaven—their brightness and speed determining the importance of the message.2 Some cultures, such as the Jacalteca Maya (Guatemala), note that if a meteor “falls near a house, it is regarded as a sign of sickness. If it bursts over a house, someone will die.” 3 • People in the Lower Congo (Africa) believed that meteors were spirits that had left their graves. It is said, “Mothers will not allow their children outside the house when there are many shooting stars to be seen, lest one should enter one of them.”4 The Northern Gê (Brazil) said meteors, “which luminously descend at night, are evil demons who assume human or animal shape on earth.” 5 The Luiseño (California, USA) believed a meteor was “Takwish,” which they described as “an animate being that carries people off and devours them.”6 • The Puyallup-Nisqually (Washington, USA) believed meteors were “traveling star people.” 7 The Takuna of the Amazon River region (South America) believed meteors were stars “chasing after their sweethearts.”8 The Kiwai Papuans of British New Guinea also believed meteors were stars shifting their places, with some saying, “the star is hurrying to a girl.”9

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 1 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_1, © Springer Science+Business Media New York 2014 2 1 Introduction

• One of the less glamorous theories developed by some southern California tribes was that meteors were feces from stars.10 Besides the verbal stories, various cultures began keeping records of what they saw. Throughout the southwestern region of the United States of America, rock etchings, called petroglyphs, depict a wide range of topics, from people and ani- mals, to astronomical objects. A number of petroglyphs exist which undoubtedly represent meteors. Meanwhile, the earliest recording of a meteor in text form comes from ancient China, where the text Zhushu jinian states, “during the night, stars fell like rain” sometime during the sixteenth and seventeenth centuries BC.11 Perhaps the earliest attempt to explain meteors in a scienti fi c fashion came from Aristotle around 340 BC. In his Meteorologica , he explained that the phenomena in the atmosphere mostly occur as the result of “exhalations that arise from the earth when it is heated by the sun ….” This not only included meteors, but also lightning, aurorae, rainbows, the Milky Way, and comets. He noted two ways that meteors were formed: Sometimes then the exhalation produces these phenomena when ignited by the heavenly motion. But sometimes heat is ejected by pressure when the air contracts owing to cold; and then they take a course more like that of a projectile than of a fi re.12 Aristotle’s statement would prove to be wrong; however, since there was still no real understanding of the realm beyond Earth, it would take over 2000 years for anyone to realize this. Seneca discussed meteors in books 1 and 2 of Naturales Quaestiones (62 AD), but did not drift far from Aristotle’s beliefs. He noted, Then the extenuated fi res make a slender path and draw it out in the sky. So, no night is without spectacles of this kind; for to produce them there is no need of great atmospheric movement. Finally—let me say it brie fl y—they are produced by the same cause as lightning bolts are, but by less force.13 Sailors think it is a sign of storm when many stars fl y across the sky. But if they are a sign of winds they belong in the region where winds come from, that is, in the atmosphere, which is right between the moon and earth.14 However, Seneca did address the question of whether or not meteors were actually stars, when he wrote, Yet it is the stupidest thing to suppose that stars actually fall, or jump across, or that anything is taken or rubbed away from them. If this were so, the stars would have perished. Yet every night very many seem to fall and to be carried off in different directions. Still, each star is found in its usual place and its size remains constant.15 This idea of meteors being an indicator of wind was reiterated by other Roman and Greek authors, as well as in other cultures. In his book Natural Selection (77 AD), Pliny the Elder wrote, “Stars also appear to rush about, and never without good reason; for this heralds the onset of fi erce winds from the same region.” Ptolemy wrote in his book Tetrabiblos (second century AD), “Appearances, resembling shooting or falling stars, when presented in one part only, threaten a movement of wind from that part; when in various and opposite parts, they portend the approach of all kinds of tempestuous weather, together with thunder and lightning.”16 1 Introduction 3

The Naskapi tribe of the Labrador Peninsula believed a meteor was a weather sign, “meaning the wind will blow in the direction designated.”17 Pliny the Elder did make a statement that rose above the superstitious beliefs. Noting that people believed the appearance of a meteor in 349 BC heralded King Philip’s attack upon the Greek coastal city Olynthus, he wrote the following: I am of the opinion that these things happen, as indeed is the case with other phenomena, at fi xed times and as a result of the power of Nature and not, as the majority of people think, from other causes invented by the ingenuity of men’s intellect. To be sure, these meteors did foretell great misfortunes, yet I think they happened because of natural phenomena and because they were going to happen anyway.18 During the fi rst half of the third century, the Greek biographer Diogenes Laërtius wrote his Lives and Opinions of Eminent Philosophers. In Book VII, under the Life of Zeno, section 81, he wrote, “And that comets, and bearded stars, and meteors, are fi res which have an existence when the density of the air is borne upwards to the regions of the aether.”19 Mention of the word “aether” makes this an interesting statement. This word has its roots in Greek mythology. In his book Works and Days (700 BC), Hesiod wrote that Cronos (sometimes Zeus or Jove, depending on the translation), “…sits above and dwells in the aether…”.20 Theognis wrote his Maxims (sixth century BC), “But when the sun indeed just now cheers on his solid-hoofed steeds in aether…”.21 Finally, among the anonymously written “Homeric Hymns” is hymn number 8 “To Ares”, written sometime between the seventh and fourth centuries BC, which, in describing the god Ares, states, “… who whirl your fi ery sphere among the planets in their sevenfold courses through the aether wherein your blazing steeds ever bear you above the third fi rmament of heaven.”22 All of these comments refer to the aether as the region of the gods and the region where the planets move, or, basically, space. Aristotle and others also used the term to represent the region beyond Earth. Why is this important to the ancient concept of meteors? Because Diogenes Laërtius could be the fi rst person to ever suggest that meteors exist beyond Earth’s atmosphere! Science saw little advancement during the Middle Ages. Aristotelian views of atmospheric and astronomical science remained largely unchanged, and very few people even questioned those views. In the last half of the seventeenth century, mathematicians began to examine the accounts of bright fi reballs in more detail, one of the most important results being the determination of the height. Geminiano Montanari (1676), a professor of mathematics at Bologna, gathered the accounts of the great meteor seen over Italy on 1676 March 31. After presenting the latitudes and longitudes of the cities from where observations were reported, as well as the meteor’s reported altitude from each location, he concluded that the “fl ame of which we speak passed over Italy at a height no less than 34 Italian miles from the earth’s surface and no more than 40 miles”. 23 This estimate equals a range of 55–64 km, which fi ts fairly well with our present knowledge, even though the trigonometric method Montanari used relied on rough accounts from inexperienced observers. Montanari also stated that the fi reball could not have been traveling any slower than 160 miles per minute. 4 1 Introduction

John Wallis (1677), a professor of geometry at Oxford, wrote about “an unusual Meteor” that was seen at dusk on 1676 September 20. He said that when it suddenly appeared it cast a light “equal to that of noon-day.” It moved swiftly and remained visible for “less than half a minute.” He added, “It seems surprising that it was seen in most parts of England, and at or near the same time: which argues, that either it was higher than the observers imagined, or else that it had a very swift motion.” Wallis then added a very interesting comment, “This made me conjecture that it might be some small comet, whose linea trajectoria passed very near our earth, or upon it.”24 By Wallis’ time, comets had been removed from the ancient idea of atmospheric phenomena and were known to orbit the sun. Edmond Halley (1714) wrote about “several extraordinary Meteors,” beginning with that discussed by Wallis. He suggested the 1676 meteor was an example of “some sort of vapours” that rose to a great height and noted that Wallis “could not get so particular an account as was requisite to determine its height, yet from the distant places it was seen in, it could not but be a great many miles high.” Halley was able to look at the accounts of two other fi reballs to determine heights using the latitudes and longitudes of cities from which observations were reported, as well as the reported angular altitude of the fi reballs. He said the fi reball seen over Germany on 1686 July 19 was at least 30 miles (>48 km) high, while the fi reball seen over England on 1708 July 31 was between 40 and 50 miles (64–81 km) high.25 Halley also reiterated the details of the fi reball that Montanari wrote about and was impressed by its velocity through the atmosphere, wondering “what sort of substance it must be, that could be so impelled and ignited at the same time: there being no Vulcano or other Spiraculum of subterraneous Fire in the N.E. parts of the World, that we ever yet heard of, from whence it might be projected.” So, despite Halley having stated that Wallis’ meteor was “some sort of vapours,” he expressed the following idea concerning Montanari’s fi reball: I have much considered this Appearance, and think it one of the hardest things to account for, that I have yet met with in the Phenomena of Meteors , and am induced to think that it must be some Collection of Matter form’d in the Aether, as it were by some fortuitous Concourse of Atoms, and that the Earth met with it as it past along in its Orb, then but newly formed, and before it had conceived any great Impetus of Descent towards the Sun. Sadly, this important step in the right direction was short lived. Halley (1719) investigated an “Extraordinary Meteor” that was seen over England on 1719 March 19. After coming to the conclusion that the meteor was 69 miles above the ground, Halley determined the distance from fi rst appearance to extinction to have been a length of more than 160 miles. After noting that the amount of time it remained visible varied among the witnesses, he wrote, “we may modestly com- pute it to have run above 300 such Miles in a Minute, which is a Swiftness wholly incredible ….” Halley came up with a very terrestrial way of explaining this meteor. He fi rst noted “the unusual and continued Heats of the last Summer in these Parts of the World, may be suppos’d to have excited an extraordinary Quantity of Vapour of all Sorts ….” He then added the following: 1 Introduction 5

…the matter of the Meteor might have been raised from a large Tract of the Earth’s Surface, and ascend far above the reputed Limits of the Atmosphere; where being disingag’d from all other Particles, by that Principle of Nature that congregates Homogenea visible in so many Instances, its Atoms might in Length and Time coalesce and run themselves into a narrower Compass, might lie like a Train of Gunpowder in the Aether, till catching Fire by some internal Ferment, as we fi nd the Damps in Mines frequently do, the Flame would be communicated to its continued Parts, and so run on like a Train fi r’d.26 John Pringle (1759) was examining the details of a meteor seen over Italy in 1719 and came across Halley’s paper quoted above. Pringle pointed out eight dif fi culties with Halley’s hypothesis of 1719 and then wrote, “Of all the hypotheses that have come to my knowledge on this subject, a hint of Dr. Halley’s (in a paper presented to the Society several years before the above-mentioned), seems best to agree with the late meteor; viz. that such bodies may be formed independent of any vapours from the earth.”27 He continued: If it is then probable, that these balls of fi re come from regions far beyond the reach of our vapours; if they approach often so near to the earth, and so seldom or never touch it; if they are moved with so much celerity, as in that respect to have the character of celestial bodies; if they are seen fl ying in all directions, and consequently have a motion of their own, independent of that of our globe; … surely we are not to consider them as indifferent to us, much less as fortuitous masses, or trains of terrestrial exhalations in the aethereal regions; but rather as bodies of a nobler origin, possibly revolving about some center, formed and regulated by the Creator for wise and bene fi cent purposes, even with regard to our atmosphere; which, during their combustion, they may supply with some subtile and salutary matter, or remove from it such parts as begin to be super fl uous, or noxious to the inhabitants of the earth.28 Interestingly, Pringle challenged Halley on another aspect of meteors. He said that Halley thought the bright meteors came to the ground, but noted the following: … if these meteors had really fallen, there must have been long ago so strong evidence of the fact, as to leave no room to doubt of it at present. Their descent, under the horizon, is suffi cient to make the common observers believe they see them come to the ground, whilst an explosion, high up in the air, coming late to their ears, passes for the crashing noise of the fall. Not that I call in question the possibility of their touching the earth….29 Thomas Clap, a professor at Yale College, wrote a dissertation titled Conjectures upon the Nature and Motions of Meteors, which Are Above the Atmosphere , which was published posthumously in 1781. In discussing large meteors that were occasionally seen crossing the sky, which “frequently exceed the light of the moon, and in some instances that of the sun, so as to make a shadow in the clearest sunshine,” Clap suggested that their brightness was caused by friction as they moved through the atmosphere at speeds of up to 500 miles a minute. He compared the meteor’s passage through the atmosphere to a cannonball being shot out of a cannon and wrote, “if a mere fl ame, smoke, or powder, or any thing not strongly cemented together, was shot out of a cannon at a velocity of 500 miles a minute, it would immediately dissipate or dissolve.” Continuing with the comparison to a cannonball, Clap suggested these meteors could be “as solid as iron.” He continued, “It is beyond the power of any laws of nature, already known, to give such a heavy body 6 1 Introduction such a prodigious velocity, above 20 times so great as that of a cannon ball.” Clap concluded, “it is evident that the earth must be the attractive central body, round which they revolve, as the secondary planets revolve around the primary, or rather as comets revolve round the sun in long ellipses, near to a parabola.” He referred to them as “Terrestrial Comets.”30 Nevil Maskelyne took an interest in meteors in 1783. He published a brief trea- tise on November 6 that was titled, “Plan for observing the Meteors called Fire- balls.” In response to the fi ve fi reballs that had appeared between 1783 August 18 and October 29, he wrote the following: For want of a series of proper observations, little progress has been made towards account- ing for their phaenomena. It is therefore to be wished that all persons who may happen to see a meteor, would attend to the following particulars, and set down their remarks as soon as they can after they see it, while the impression made by the meteor is full and fresh in their memory.31 Among the information requested was the place of observation, precise time of the appearance, the altitudes and bearings of the meteor, brightness, color, duration, existence of train, and the existence of a burst. Maskelyne wrote a letter to Angelo Giovanni de Cesaris, an astronomer at Milan Observatory (Italy), on December 12, encouraging him “to observe more keenly the phenomena called fi re-balls. In all probability they will turn out to be comets.”32 A new theory was put forth in 1785. In an analysis of a meteor that was seen over Great Britain at 9:16 p.m. on 1783 August 18, Charles Brian Blagden looked at the observations of this “luminous ball.” He said it “rose in the N. N. W. nearly round, became elliptical, and gradually assumed a tail as it ascended.” Observers said it “apparently divided into a great number, or cluster of balls, some larger than others, and all carrying a tail or leaving a train behind ….” The meteor gave off a “prodigious light, which illuminated all objects to a surprising degree ….” It fi nally disappeared toward the southeast. Blagden determined that the meteor traversed about a thousand miles in “about half a minute.” It was noted that “some time after the meteor … had disappeared” many observers heard a sound like the “discharge of one or more large cannon at a distance.” Blagden also noted that many people reporting hearing a “hissing, whizzing, or crackling” sound as the object passed overhead. Since his calculations reveal the object was over 50 miles high, such sounds are “somewhat irreconcileable [sic] to all we know,” but added “the testi- mony in support of it is, however, so considerable on the occasion of this as well as former meteors, that I cannot venture to reject it, however improbable it may be thought, but would leave it as a point to be cleared up by future observers.”33 Blagden then looked at how the various proposed theories would explain an object of this nature. He said the idea of “burning bodies projected with such a velocity” should be abandoned “from want of any known power to raise them to that great height …” He said Halley’s idea of a “train of in fl ammable vapours” has numerous unexplained aspects, such as how such vapors are raised to such a height and how they move in such a straight line. Blagden said a third hypothesis of meteors being “permanent solid bodies, not raised from the earth, but revolving around it in very eccentric orbits” has “many strong objections.” Some of these objections included 1 Introduction 7 meteors not “looking like solid bodies, but rather like a fi ne luminous matter” and that “a body falling from infi nite space towards the earth, could have acquired … a velocity of only seven miles in a second; whereas those meteors seem to move at least three times faster.” Blagden fi nally concluded “that the only agent in nature capable of producing such phenomena, is electricity.” He said this explains the “luminous matter” appearance, the great speed, and the hissing sound.34 Antoine Laurent Lavoisier de fi ned what meteors probably were in his second chapter of Traite Élémentaire de Chimie (1789). While discussing the formation and constitution of Earth’s atmosphere, he wrote the following: Phenomena that accompany fi ery meteors lead me to believe that there is thus at the top of the atmosphere a layer of fl ammable fl uid, and that is the point of contact of the two layers of air that operate the phenomena of the aurora borealis & other fi ery meteors.35 Despite all of these theories, as well as others not discussed here, none caused debate as much as that published by Ernst Florens Friedrich Chladni in 1794. After investigating the Pallas meteorite (found in Siberia in 1749) and the Tucuman meteorite (found in Argentina in 1783), Chladni began studying eyewitness accounts of fi reballs that he had accumulated during 3 weeks at the library in Göttingen, Germany, including 18 reports of stone or iron falling from the sky extending as far back as Pliny the Elder. He then addressed how some of the prevalent theories of meteors and fi reballs failed to explain all of the details observed during these events. He arrived at several conclusions. First, masses of stone and iron do fall from the sky. Second, the fi reballs began glowing as they moved through the atmosphere because of friction. Third, the chemistry of these masses, especially the iron ones, was similar to each other, yet different from similar material found on Earth. Fourth, the objects originated from space and they either never coalesced into larger bodies or were fragments from planets. Five, the objects were drawn into our atmosphere by the gravitational pull of our planet. Chladni concluded, “I have given an explanation, which, however romantic it may seem, agrees better, in my opinion, with the facts hitherto observed than any other, and is contrary to no laws of nature hitherto known.”36 Chladni believed that what was needed to help confi rm his ideas were careful observations, including observers from different locations being able to use trigo- nometry to accurately determine the heights of meteors. Heinrich Wilhelm Brandes and Johann Friedrich Benzenberg (University of Göttingen) stepped up to Chladni’s challenge with a little encouragement from a friend of Chladni’s, Georg Christoph Lichtenberg. They began their experiment on 1798 September 11 and made additional observations on September 13 and October 6; however, their initial results were not good. The baseline of about 9 km was only good enough to establish that the meteors were more than 10 km high. So, beginning on October 9 they increased the baseline to nearly 16 km. The result was 17 additional simultaneously observed meteors, with beginning heights of 50–171 km.37 [It should be noted that the original estimates were given in “geographical miles,” of which there are two defi nitions: a length covering one minute of arc along the equator (1855.4 m) and a length covering four minutes of arc (7421.5 m). Since the longer length was adopted in Germany, this was used by the Author to determine the distances given above.] 8 1 Introduction

Interestingly, Benzenberg and Brandes noted that two meteors rose in the atmosphere, one going straight up. Although we now know that there was apparently an error in someone’s plotting, this knowledge caused Chladni (1803) to revise part of his theory. He stated that fi reballs have a cosmic origin, but shooting stars “are an event in our atmosphere, by its nature, we have no idea, but they deserve attention and scrutiny in the future.”38 Chladni (1818) dismissed the Benzenberg and Brandes observations of rising meteors, stating that conclusions should not have been based on 22 observations, but on 200.39 An interesting article appears in an 1821 issue of the Philosophical Magazine and Journal . John Farey discussed something that he noticed in the meteorological observations of William Burney in the year 1820. Burney saw a total of 131 meteors during the year, 80 of which were seen in August. Farey wrote, “The singular fact, of the month of August having furnished so very disproportioned a number of these observations, is accompanied by the mention that 35 of these were observed in 1 h, which preceded midnight on the 9th of August last ….” He added that some of the meteors were said to have left “sparkling trains” that lasted several seconds. Farey asked Burney to “commence a series of more minute observations on Shooting Stars and Meteors” in order to answer questions about these objects. Farey listed nine questions that he hoped would be answered, some requiring more than one observer separated by some distances. He ultimately hoped to learn the heights of the meteors, as well as what accounted for the disparaging number of meteors from month to month.40 Despite the requests of Maskelyne and Farey, there appears little evidence that anyone began to systematically study meteors. The study of meteors seemed to need a catalyst of some type to get people to start paying attention, and this came on the morning of 1833 November 13. As will be seen when reading about the Leonid meteor shower later in this book, the sky was fi lled with meteors on that morning. Among the thousands of eyewitnesses were several scientists. Perhaps the biggest discovery was the fact that the meteors all seemed to be radiating from a speci fi c area of the sky. Denison Olmsted (1834), a professor of mathematics at Yale College, concluded that the radiation point came about because the meteors had approached Earth in nearly parallel lines and that the apparent scattering across the sky was due entirely to the effect of perspective. Remembering reports of a fairly strong shower of meteors in November of 1832, Olmsted conjectured that a cloud of particles was responsible in this part of Earth’s orbit.41 Subsequently, in November 1834, another shower was observed, admittedly more comparable to the weaker 1832 display than that of 1833, but it did confi rm the existence of an annual meteor shower. The change in intensity was correctly theorized as due to a periodicity of some kind. Following the announcement of the discovery of the annual Perseid meteor shower in 1836, Adolf Erman (1839) published his analysis of observations made of this meteor shower on 1839 August 9, 10, and 11. He determined very precise radiant positions and then calculated fi ve orbits–four with orbital periods of less than 1 year and one parabolic.42 This was the fi rst time anyone had calculated an orbit for a meteor stream, and many writers have referred to it as the “ring theory.” As strange as it may seem, this same paper of Erman’s went on to discuss how both 1 Introduction 9 the Perseid and Leonid rings passed between the Earth and the Sun on February 7 and May 12, respectively, and that cold spells were the result. The next advancement in the understanding of meteor showers did not come until 1861, when Daniel Kirkwood (1861) published an article titled “Cometary Astronomy” in the Danville Quarterly Review. In discussing six published instances of split comets, from ancient times up to 1846 January, when periodic comet 3D/ Biela was observed as two separate comets, Kirkwood wrote the following: In view of these facts it seems highly probable, if not absolutely certain, that the process of division has taken place in several instances besides that of Biela’s comet. May not the force, whatever it is, that has produced one separation, again divide the parts? And may not this action continue until the fragments become invisible? According to the theory now generally received, the periodic phenomena of shooting stars are produced by the intersections of the orbits of such nebulous bodies with the earth’s annual path. Now there is reason to believe that these meteoric rings are very elliptical, and in this respect wholly dissimilar to the rings of vapor which, according to the nebular hypothesis, were succes- sively abandoned at the solar equator; in other words, that the matter of which they are composed moves in cometary rather than planetary orbits. May not our periodic meteors be the debris of ancient but now disintegrated comets, whose matter has become distrib- uted around their orbits? 43 This theory was con fi rmed in 1866, when Giovanni Virginio Schiaparelli wrote a letter to Angelo Secchi stating that the August meteors were produced by the periodic comet Swift-Tuttle. This comet had been discovered in 1862 and, although its then accepted orbital period of nearly 120 years was much greater than that accepted for the Perseid orbit, the similarity in the orbital elements was too close for mere coincidence. Interestingly, in this same letter, Schiaparelli also used the name “Perseids” for the fi rst time and set a precedent for naming meteor streams. 44 With the origins of meteors generally established, observers began to search the sky in the hopes of isolating other active meteor showers. Visual observations have, of course, been the most common method for well over a century. Professional and amateur astronomers such as William Frederick Denning, Ronald Alexander McIntosh, Cuno Hoffmeister, and Charles Pollard Olivier were not only proli fi c observers, but they also encouraged others to observe. Denning (1899) produced a massive catalog in an 1899 issue of the Memoirs of the Royal Astronomical Society , in which he collected over 4,000 radiants from the lists of observers and isolated 278 active meteor showers.45 The primary problem with this particular work was the theory applied to establish the active showers. Denning was a strong believer in the existence of stationary radiants—radiants which remained at the same position for months at a time. Although no one can deny that Denning was an excellent observer, his belief in the impossible stationary radiant theory plagued his statistical studies of active meteor showers well into the third decade of the twentieth century, despite mathematical proof being put forth by several astronomers around the turn of the century. Subsequently, many of his “established” annual showers were simply collections of sporadic, one-time-only radiants, which occurred sometime within any particular 5–9 month period. One of the largest of the twentieth century attempts to isolate active meteor showers was a list of 320 Southern Hemisphere radiants produced by McIntosh in 10 1 Introduction

1935. 46 The list’s main fault was that it was not selective, and many of the radiants were based on only one or two nights of observations—making the probability of the inclusion of sporadic radiants quite high. Both Hoffmeister and Olivier did not try to produce lists of possible annual radiants. They both did recognize the well-established showers and even discovered a few new annual displays, but their contribution was to produce published works of observations, which later researchers looked at as a goldmine of information when trying to fi nd a past history for newly recognized radiants. From its beginnings on 1885 November 27, when Ladislaus Weinek (Prague Observatory, Czech Republic) photographed a meteor from the Andromedid meteor shower,47 meteor photography has greatly progressed, as better cameras and faster fi lm became available. The fi rst survey was conducted by William Lewis Elkin (Yale University Observatory, Connecticut, USA) on 1893 August 9 and 10. A camera with a 6-in. lens was set up at the observatory, while another camera with a 4-in. lens was set up ten miles away. Meteors were only recorded on the 9th— three with the observatory camera and one with the remote camera. Fortunately, one of the meteors was recorded by both cameras. The meteor’s displacement between the two locations was six degrees.48 Because of the success, Elkin conducted another survey during the Leonid meteor shower of 1898 November 14–15. The two camera stations recorded a total of 16 meteor trails (8 Leonids and 8 sporadics). One Leonid was recorded from both stations, which Elkin said revealed a beginning height of 111.2 km and an end height of 98.6 km. 49 Harvard College Observatory (Massachusetts, USA) operated camera stations in Massachusetts and New Mexico in the United States from 1936 to 1951, which ultimately resulted in the calculation of 144 meteor orbits.50 This was a precursor to the very successful Harvard Meteor Project of 1952–1954, which exclusively operated in New Mexico and resulted in the calculation of 2,529 meteor orbits.51 Both of the Harvard surveys were cited in numerous papers published in the years that followed, providing an excellent base for better de fi ning known meteor showers and discovering new ones, not to mention solidifying associations to known comets. Other photographic surveys were conducted in Europe, the United States, Canada, and the former Soviet Union as the twentieth century progressed. By the late 1980s and early 1990s, groups of amateur astronomers were working together to produce high-quality photographic surveys of their own. Following the determination of the 2,529 photographic meteor orbits during the Harvard Meteor Project, astronomers were faced with a new problem: with data that was more accurate than the purely visual observations of the last century, how could it be analyzed to precisely determine radiants and orbits of meteor streams? Richard Boynton Southworth and Gerald Stanley Hawkins (1963) took a random sample of 360 of the meteors from the Harvard Meteor Project and developed a mathematical formula to compare all variables in the orbital elements, which would produce a factor they called the “D-criterion,” to indicate the level of probability that two or more orbits were related to one another. They determined the likely ranges of the “D-criterion,” which would indicate whether or not meteors were associated with each other.52 The “D-criterion” has been widely used by researchers up to the present time. There were a few published modifi cations to this technique 1 Introduction 11 during the 1970s and 1980s; however, the only modi fi cation that is still in use is that published by Jack D. Drummond (1979), 53 which many people prefer over the Southworth-Hawkins formula. Another observing technique had its beginnings in the early twentieth century, when scientists were using radio waves to study Earth’s atmosphere. It was discovered that radiation from the sun ionized a portion of the atmosphere during the day, which reached a peak around noon and reached a minimum during the nighttime hours. This portion of the atmosphere is now known as the ionosphere. But something else was also discovered: sudden bursts of electron density at night. Although many ideas were put forward, it was Hantaro Nagaoka (1929) who made the earliest suggestion that the cause of the bursts were meteors.54 As with the 1833 visual observations and the 1898 photographic observations, it was the Leonid meteor stream that provided the impetus for an advance in meteor astronomy. During 1931, John Peter Schafer and William McHenry Goodall (1932) monitored the ionization patterns in the atmosphere around the time of the expected peak of the Leonid meteors. Unfortunately, the experiment was marred by magnetic disturbances on the night of November 16/17 and the results were inconclusive.55 So, during the expected Leonid peak of 1932, Schafer and Goodall again monitored radio waves for ionization patterns in the atmosphere. Albert Melvin Skellett (1935) also participated and noted that they obtained a visual correlation between the appearance of meteors overhead and sudden increases in ionization on the nights of November 14/15 and 15/16.56 An important advancement in using the radio-echo technique for studying meteors began in 1944 October, when James Stanley Hey and Gordon S. Stewart (1946) fully con fi rmed “that the majority of scatter echoes must be of meteoric origin and are due to refl exions from meteor trains or streaks….” 57 From 1946 October 7–11, Hey, Sydney John Parsons, and Stewart (1947) observed the Draconid meteor shower using equipment that directed 5-m wavelength beams directed vertically upwards, with receivers picking up the ionization trails. Hey, Parsons, and Stewart reported a minor peak on October 9.94 and a major peak on October 10.17. At the time of the major peak, nearly 300 meteors per hour were being detected. 58 From these beginnings, the technique of picking up the echoes of meteors in the atmosphere using radio grew. By the 1960s, even more sensitive radio-echo surveys were being conducted in the former Soviet Union, Australia, Canada, and the United States. These surveys were able to detect meteors much fainter than what photography or the naked eye could see. The result was that more meteors could be observed, which meant more accurate determinations of the radiants, radiant movements, velocities, and orbits of meteor streams. In addition, with this information available for a wider range of particle sizes, a better understanding of stream dynamics could be acquired—for instance, the separation of small and large particles over time. Radar studies of meteor activity have fi nally provided the catalyst for con fi rming whether many minor meteor streams actually exist. Right at the dawn of radar meteor studies, Olivier wrote the following: 12 1 Introduction

I confess that the more I work on meteors the less confi dence I have in tables of minor radiants. Perhaps the true solution of the question will be to accept as real only those which can be detected with certainty every year, or at recurrent returns after the same number of years have elapsed. Meantime, however, I believe that the publication of lists, carefully derived, lays the foundation for future selection of those radiants which will stand the test and are thus justi fi ed.59 With the birth of radar studies, researchers now had a very solid foundation with which they could build upon. This data has greatly increased our present knowledge of meteor astronomy. Numerous comet-meteor and asteroid-meteor associations have been revealed, which not only tell us something about meteor stream evolution, but also how comets age and eventually become asteroid-like bodies. Several meteor showers are now known to possess two or more simultaneously active radiants, because their meteor streams contain multiple fi laments or ringlets of material due to continual planetary perturbations, especially from Jupiter. The understanding of how these ringlets form and are altered by perturbations became the basis for a very signi fi cant series of papers at the close of the twentieth century. David J. Asher and Robert H. McNaught created a model for the evolution of the Leonid meteor stream. It explained why signifi cant outbursts occurred during some returns of periodic comet 55P/Tempel-Tuttle (the Leonids’ parent comet), but not others during the period of 1833–1969. It also predicted what might happen during the period of 1999–2006, when enhanced displays were expected because of the comet’s return to perihelion in 1998. 60 Asher also presented a paper describing his model at the Leonid MAC Workshop held at the NASA Ames Research Center (California, USA) from 1999 April 12–15. Asher explained how the fi reball-rich Leonid outburst of 1998 November was caused by the dust released by comet Tempel-Tuttle during its return in 1333, and how the famous Leonid outburst of 1966 November was caused by dust released by this comet in 1899. Asher predicted that the 1899 trail would next be closest to Earth on 1999 November 18.09 and that an outburst would occur over Europe, the Middle East, and Africa.61 Professional and amateur astronomers around the world watched for the predicted Leonid outburst on the night of 1999 November 17/18. Some traveled to regions of the world that were predicted to see a possible meteor storm. NASA and the United States Air Force even funded a mission to have two aircraft loaded with cameras and scientists fl y over the Mediterranean Sea on the night of the outburst. What observers in the Europe/Africa region saw was the fi rst nearly perfect prediction of an outburst from a meteor stream. Predictions had been made in the past, but the mechanism had not been precisely known, resulting in some coming true and others not. The outburst occurred within 5 min of the prediction; however, instead of the predicted rate of 1,200–1,500 meteors per hour, the observed rate was nearly 3,600 meteors per hour. During the next few years, the predicted times of outbursts continued to be quite accurate, while models predicting the rate improved. The model has now been used to predict higher than normal rates of activity for other meteor showers, including the Perseids and Ursids. The successful creation of a model for the evolution of a meteor stream was the culmination of nearly 170 years of meteor shower research that began on the night of 1833 November 12/13 during a strong outburst of the Leonid meteor shower. 1 Introduction 13

This wake-up call literally began the study of meteor showers. Interestingly enough, the Leonids have played an important role in our continued advancement in this fi eld, as they were the subject of the fi rst photographic survey in 1898 and they were the subject of the 1932 radio wave test when ionization patterns in the atmosphere were found to coincide with the appearance of visual meteors. As can be seen from the history presented above, as well as in the pages that follow, everything that has been learned about meteor showers is a result of observations made by both amateur and professional astronomers. Without both of these groups, the study of meteor showers would not be as advanced as it is today. Few other fi elds of science can claim a comparable level of success from the cooperation between amateurs and professionals.

1. W. F. Denning, The Observatory , 46 (1923 Aug.), p. 251. 2. Ho Peng Yoke, The Astronomical Chapters of the Chin Shu. Paris: Mouton & Co. (1966), pp. 136–8. 3. La Farge, Oliver II, and Byers, Douglas, The Year Bearer’s People. New Orleans: The Department of Middle American Research (1931), p. 129. 4. Weeks, Rev. John H., “Notes on Some Customs of the Lower Congo People,” Folklore , 20 (1909 Dec.), p. 476 5. Folk Literature of the Gê Indians (volume 1). Edited by J. Wilbert and K. Simoneau, Los Angeles: UCLA Latin American Center Publications (1978), p. 125. 6. P. S. Sparkman, “The culture of the Luiseño Indians.” American Archaeology and Ethnology, 8 (1908 Aug. 7), p. 220. 7. M. W. Smith, The Puyallup-Nisqually . New York: AMS Press (1940), pp. 133–4. 8. C. Nimuendajú, The Tukuna. Berkeley: University of California Press (1952), p. 144. 9. G. Landtman, The Kiwai Papuans of British New Guinea . London: MacMillan and Co., Limited (1927), p. 51. 10. T. Hudson, Archaeoastronomy and the Roots of Science . Edited by E. C. Krupp, Colorado: Westview Press, Inc. (1984), pp. 39–41. 11. D. W. Pankenier, Z. Xu, and Y. Jiang, Archaeoastronomy in East Asia . Amherst (New York): Cambria Press (2008), p. 306. 12. Aristotle, Meteorologica (340 BC), translated by H. D. P. Lee, Cambridge (Massachusetts): Harvard University Press (1952), pp. 29–33. 13. Seneca, Naturales Quaestiones (62AD), translated by T. H. Corcoran. Cambridge (Massachusetts): Harvard University Press: Macmillan and Co., Ltd (1971), p. 17. 14. Seneca, Naturales Quaestiones (62AD), translated by T. H. Corcoran. Cambridge (Massachusetts): Harvard University Press: Macmillan and Co., Ltd (1971), p. 21. 15. Seneca, N aturales Quaestiones (62AD, translated by T. H. Corcoran. Cambridge (Massachusetts): Harvard University Press: Macmillan and Co., Ltd (1971), pp. 19–21. 16. Ptolemy, Tetrabiblos (2nd century AD), translated by J. M. Ashmand. London: David and Dickson (1822), pp. 102–3. 17. F. G. Speck, Naskapi: The Savage Hunters of the Labrador Peninsula. Norman: University of Oklahoma Press (1935), pp. 65–6. 18. Pliny the Elder, Natural History (77 AD), translated by J. F. Healy. New York: Penguin Books (1991), pp. 21–3. 19. Diogenes Laërtius, Lives and Opinions of Eminent Philosophers (3rd century AD), translated by C. D. Yonge. London: George Bell and Sons (1901), p. 315. 20. Hesiod, Works and Days (700 BC): Hesiod, the Homeric Hymns and Homerica, translated by H. G. Evelyn-White, London: William Heinemann (1920), p. 3. 21. Theognis, The Maxims (6th century BC): The Works of Hesiod, Callimachus, and Theognis, translated by J. Banks, London: George Bell and Sons (1879), p. 271. 22. Anonymous, Homeric Hymns (7th to 4th century BC): Hesiod, the Homeric Hymns and Homerica , translated by H. G. Evelyn-White, London: William Heinemann (1920), p. 433. 14 1 Introduction

23. G. Montanari, La ﬁ amma volante gran meteora veduta sopra l’Italia la sera de 31 Marzo M. DC. LXXVI . Bologna: Manolessi (1676), p. 17. 24. J. Wallis, Philosophical Transactions of the Royal Society of London , 12 (1677), p. 863. 25. E. Halley, Philosophical Transactions of the Royal Society of London, 29 (1714 Oct.–Dec.), pp. 159–64. 26. E. Halley, Philosophical Transactions of the Royal Society of London , 30 (1719 Mar.–May), pp. 989–90. 27. J. Pringle, Philosophical Transactions of the Royal Society of London , 51 (1760), p. 271. 28. J. Pringle, Philosophical Transactions of the Royal Society of London , 51 (1760), p. 273. 29. J. Pringle, Philosophical Transactions of the Royal Society of London , 51 (1760), p. 272. 30. T. Clap, Conjectures upon the Nature and Motions of Meteors, which Are Above the Atmosphere . Norwich (Connecticut): John Trumbull (1781), pp. 10–11. 31. N. Maskelyne, The London Magazine , 1 (1783 Dec.), pp. 498–9. 32. N. Maskelyne, Memorie della Società Italiana , 3 (1786), p. 345. 33. C. B. Blagden, The Scots Magazine , 47 (1785 May), pp. 212–15. 34. C. Blagden, The Scots Magazine , 47 (1785 May), pp. 265–6. 35. A. Lavoisier, Traite Élémentaire de Chimie , Volume 1. Paris: Cuchet (1789), p. 32. 36. E. F. F. Chladni, Ueber den Ursprung der von Pallas gefundenen und anderer ihr aehnlicher Eisenmassen , Riga: Hartknoch, (1794), 63pp. 37. J. F. Benzenberg and H. W. Brandes, Versuche die Entfernung: die Geschwindigkeit und die Bahnen der Sternschnuppen zu bestimmen . Hamburg: Friedrich Perthes (1800), pp. ??. 38. E. F. F. Chladni, Annalen der Physik , 15 (1803), pp. 324–5. 39. E. F. F. Chladni, Annalen der Physik , 58 (1818), p. 293. 40. J. Farey, The Philosophical Magazine and Journal , 57 (1821 May), pp. 346–51 41. D. Olmsted, American Journal of Science and Arts , 26 (1934 Jul.), p. 165. 42. A. Erman, Astronomische Nachrichten , 17 (1839 Oct. 31), pp. 3–16. 43. D. Kirkwood, Davville Quarterly Review , 1 (1861 Dec.), pp. 636–7. 44. G. V. Schiaparelli, Bullettino Meteorologico dell’Osservatorio del Collegio Romano , 5 (1866 Nov.), pp. 127–33. 45. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), pp. 203–94. 46. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society, 95 (1935 Jun.), pp. 709–18. 47. L. Weinek, Astronomische Beobachtungen an der K. K. Sternwarte zu Prag, 2 (1890), pp. 44–50. 48. W. L. Elkin, Astronomical Journal , 13 (1893 Sep. 20), p. 132. 49. W. L. Elkin, Astrophysical Journal , 10 (1899), pp. 25–8. 50. F. L. Whipple, Astronomical Journal , 59 (1954 Jul.), pp. 201–17. 51. R. E. McCrosky and A. Posen, Smithsonian Contribution to Astrophysics , 4 (1961), pp. 15–84. 52. R. B. Southworth and G. S. Hawkins, Smithsonian Contribution to Astrophysics , 7 (1963), pp. 261–85. 53. J. D. Drummond, Proceedings of the Southwest Regional Conference for Astronomy and Astrophysics , 5 (1980), pp. 83–6. 54. H. Nagaoka, Proceedings of the Imperial Academy of Tokyo , 5 (1929), pp. 233–6. 55. J. P. Schafer and W. M. Goodall, Proceedings of the Institute of Radio Engineers , 20 (1932 Dec.), pp.1941–5. 56. A. M. Skellett, Proceedings of the Institute of Radio Engineers , 23 (1935 Feb.), pp. 132–49. 57. J. S. Hey and G. S. Stewart, Nature , 158 (1946 Oct. 5), pp. 481–2. 58. J. S. Hey, S. J. Parsons, and G. S. Stewart, Monthly Notices of the Royal Astronomical Society, 107 (1947), p. 177. 59. C. P. Olivier, Popular Astronomy , 49 (1941), p. 550. 60. R. H. McNaught and D. J. Asher, WGN, Journal of the International Meteor Organization , 27 (1999 Apr.), pp. 85–102. 61. D. Asher, “Modeling of the Leonid meteor shower,” The Leonid MAC Workshop, NASA Ames Research Center, CA, 1999 April 12–15. Edited by P. Jenniskens. Meteoritics & Planetary Science (1999). Chapter 2

January Meteor Showers

Zeta Aurigids

The slow moving meteors of the Zeta Aurigid meteor stream seem to have mostly eluded observers during the last century and a half and they were not truly discovered until the radar surveys went into operation during the 1970s. This indicates that the bulk of the stream is mostly composed of very tiny particles, and that few visual meteors are seen. Z. Sekanina (1973) discovered this meteor shower while analyzing the data collected during the 1961–1965 session of the Radio Meteor Project. Activity was detected during December 14-January 14 and the nodal passage occurred on December 30.9 (l = 278.9°), when the radiant was located at a = 77.5°, d = +39.3° and the geocentric velocity was 14.2 km/s.1 Sekanina (1976) con fi rmed the stream during the 1968–1969 session of this project; however, although a similar duration of December 14-January 16 was noted, the nodal passage occurred on January 13.9 ( l = 293.2°), when the radiant was located at a = 83.8°, d = +58.0° and the geocentric velocity was 11.9 km/s.2 Although the latter survey certainly con fi rms the results of the former, it does not confi rm the time of maximum nor the radiant position; however, the second session of the Radio Meteor Project did not operate during the crucial period of 1968 December 21–1969 January 12. As a result, the period of maximum activity was missed. It seems likely that this gap not only reduced the number of meteors being observed, but also in fl uenced the shower’s apparent distribution of meteor activity. Meteors from this stream were rarely detected prior to Sekanina’s surveys and are absent from most of the nineteenth century radiant catalogs; however,

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 15 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_2, © Springer Science+Business Media New York 2014 16 2 January Meteor Showers

W. F. Denning published a catalog of radiant points in 1899 that basically covered the previous four decades of observations and revealed some trace of the Zeta Aurigids. He noted a fi reball seen by A. S. Herschel and several other people on 1863 December 27 that came from a radiant of a = 75°, d = +30°. A bright meteor seen by many people on 1886 December 28 was analyzed by Denning and found to come from a radiant of a = 77°, d = +30°. In addition, Denning plotted fi ve meteors in 1885–1886 on December 24–31, which indicated a radiant of a = 77°, d = +32°.3 Denning published a radiant catalog in 1916, which included another fi reball from this radiant. This fi reball was seen on 1913 January 2.82 and came from a radiant of a = 75°, d = +30° with a velocity of 24 km/s.4 Astronomers participating in the Arizona Expedition for the Study of Meteors reported two radiants at the beginning of 1932. One was detected on January 1 at a = 82°, d = +36°, while the other was detected on January 4–5 at a = 72°, d = +35°.5 Visual observations made since the 1960s Radio Meteor Project have continued to rarely reveal activity from the Zeta Aurigid stream; however, since 1993, the International Meteor Organization (IMO) has been compiling a database of meteors detected using video cameras which has shown the stream still produces activity. As of 2012, this video meteor database now includes over a million meteors, many of which were fainter than naked-eye visibility. Analysis by the IMO reveals activity around December 31 (actual l = 278°–280°) from a radiant at a = 80.5°, d = +38.5°. Based on 85 video meteors, the velocity is given as 20.0 km/s. The radiant is evident again on January 1 (actual l = 279°–281°). For this date, 57 video meteors indicate a radiant at a = 81.6°, d = +39.5° and a velocity of 19.0 km/s. A possible parent for this meteor shower was announced in 1989.6 Not long after the discovery of minor planet 5731 Zeus (1988 VP4), a similarity of its orbit was noted to the two orbits determined for the Zeta Aurigids by Sekanina. These orbits are given below. The radio meteor orbits are provided below. The orbit labeled “1961–1965” is from Sekanina (1973), while the orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “5731” is that of minor planet 5731 Zeus (1988 VP4).

w W (2000) i q e a 1961–1965 235.8 279.7 6.7 0.816 0.602 2.05 1968–1969 221.0 293.9 11.1 0.901 0.513 1.85 5731 216.97 281.71 11.43 0.784 0.654 2.26

January Boötids

From 1957 January 16–19, C. D. Watkins and E. Doylerush (Jodrell Bank Experimental Station, Lower Withington, Cheshire, England) detected activity from a radiant roughly given as a = 225°, d = +25°; however, the large radiant January Boötids 17

diameter of 10°–15° caused the researchers to reevaluate the data and they subsequently arrived at an average radiant of a = 233°, d = +37°. Maximum was stated to have occurred on January 17 (l = 297°), when the hourly rate reached 25. There seemed to be evidence that the daily motion was roughly 2° eastward.7 The stream was again detected at Jodrell Bank in 1958. On this occasion, however, radio meteors were only detected on January 18 (l = 297.6°). The hourly rate reached 9, while the radiant appeared only 5° across. The radiant was determined to be a = 237°, d = +34°. 8 While analyzing all observations obtained in 1957 and 1958, G. C. Evans concluded that the January Boötids have a duration extending from solar longitude 290°–304°, or roughly from January 11 to 25. Interestingly, from 1958 January 15 to 16, eight radar stations in the USSR detected an unusual increase in meteoric activity.9 Although no radiant was determined, the activity seems to add some additional support to Jodrell Bank’s 1958 observation. The Radio Meteor Project detected this stream from 1969 January 14 to 15. Z. Sekanina (1976) said 15 meteors came from a radiant of a = 225.8°, d = +44.2°, with an average geocentric velocity of 29.4 km/s. The orbit indicated a nodal passage on January 14.9 (l = 294.2°). Sekanina indicated that no meteors were detected on January 13 or during January 16–17 and the radar was shut down during January 1–12 and January 18–26. 2 Sekanina (1973) did not recognize this stream in data collected during the fi rst session of the Radio Meteor Project of 1961–1965. As with the 1968–1969 session, the fi rst session did not operate continuously. Looking at the original data for the 19,327 orbits determined during the fi rst session, it can be seen that the peak times indicated by the Jodrell Bank data were only fully covered in 1962 and 1963. The radar was shut down from 1964 January 18 to 26 and from 1965 January 14 to 25. The radar was also shut down from the early days of January through the 13th in every year except 1965. Another factor is that the radar did not always operate 24 h per day and was shut down during periods important to the detection of this stream. In other words, there was very poor coverage of the key activity periods for this stream during the 1961–1965 session. A quick look reveals that meteors matching the orbits below were indeed detected during this fi rst session, with two excellent examples appearing on 1962 January 15 and 17. The strongest evidence of visual meteors from this stream was a single meteor photographed on 1953 January 13 during the Harvard Meteor Project. It attained a magnitude of −0.3 and came from a radiant at a = 223.0°, d = +43.9°. The geocentric velocity of 27.3 km/s and the orbit are very similar to the results of the Radio Meteor Project.10 The orbit labeled “1953” is from L. G. Jacchia and F. L. Whipple (1961). The orbit labeled “1968–1969” is from Sekanina (1976).

w W (2000) i q e a 1953 349.1 293.6 56.3 0.690 0.177 0.84 1968–1969 346.4 294.9 59.9 0.836 0.090 0.92 18 2 January Meteor Showers

Lambda Boötids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) announced the discovery of 13 new meteor showers after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired from 2002 to 2006. The Lambda Boötids were said to span the period of January 6–18 (l = 285°–297°), with its maximum coming on January 16 ( l = 295.5°) from a radiant at a = 219.6°, d = +43.2°. The geocentric velocity was given as 41.75 km/s, while the radiant’s daily motion was determined as +0.88° in a and −0.69° in d . 11 Complete details were published in the journal Icarus during 2008.12 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as January 1–18 (l = 280°–297°). The date of maximum was given as January 17 ( l = 296°), at which time the radiant was at a = 221.5°, d = +42.4°. The geocentric velocity was determined as 40.7 km/s. The radiant’s daily motion was determined as +1.04° in a and −0.76° in d . 13 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. Stream number 12 is called the “Lambda Boötids” and is based on 272 meteors. The duration is given as January 16–23 ( l = 296°–303°), while maximum occurs on January 21 (l = 301°) from a radiant at a = 226.7°, d = +42.0°. The radiant drift was determined as +1.1° in a and −1.4° in d per day. 14 There is evidence that the stream produces meteors that can be seen visually. G. V. Schiaparelli analyzed the observations of meteors made in Italy from 1868 to 1870. He noted, “Many small meteors Jan. 19 (no trace on the 18th), 1869.” He said the radiant was at a = 220°, d = +40°. 15 W. F. Denning (1978) plotted the meteor paths that had been observed in 1872 by the Italian Meteoric Association. Seven meteors seen during January 1–15 came from an average radiant at a = 221°, d = +43°. 16 On 1877 January 9, Denning plotted six meteors from a = 221°, d = +42°. He described them as swift. 17 The next record of this shower is located in C. Hoffmeister’s book Meteorströme and was made on 1937 January 10 (l = 288.9°), when A. Teichgraeber noted a radiant at a = 225°, d = +45°. 18 The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 354 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 2,743 meteor orbits.

w W (2000) i q e a 2002–2006 208.8 295.5 79.0 0.952 0.3680 1.5 2002–2008 203.90 296.0 78.3 0.9647 0.291 1.36 Delta Cancrids: Antihelion 19

Delta Cancrids: Antihelion

The discovery of this meteor stream is attributed to B. A. Lindblad (1971). He examined the photographic meteor orbits obtained during the Harvard Meteor Project of 1952–1954 and found seven meteors that came from an average radiant of a = 126°, d = +20° during January 13–21, which exhibited an average geocentric velocity of 28 km/s.19 Support for Lindblad’s fi ndings came in 1973 and 1976, when Z. Sekanina published the results of the two sessions of the Radio Meteor Project conducted at Havana, Illinois (USA), during the 1960s. The fi rst session covered the period of 1961–1965 and detected 27 meteors from December 28-January 30 from an average radiant of a = 123.7°, d = +20.9°. The date of the nodal passage was given as January 13 (l = 292.2°), while the geocentric velocity was 25.8 km/s.20 The second session covered the period of 1968–1969 and detected 37 meteors from December 14-February 14 from an average radiant of a = 129.8°, d = +19.8°. The nodal passage came on January 17 ( l = 296.4°) and the geocentric velocity was given as 26.4 km/s. 2 Visual observations sporadically appear in the literature of the last 150 or so years. In the nineteenth century, the fi rst report came from the Italian Meteoric Association when, from 1872 January 1 to 15, seven meteors were detected from an average radiant of a = 130°, d = +24°.21 Additional detections in that century include a fi reball spotted on 1879 January 12, from a radiant of a = 133°, d = +19°. 22 and seven meteors spotted by H. Corder (England) from 1897 January 23 to 24 from a radiant of a = 126°, d = +19°. 23 In the twentieth century, two probable radiants were published in C. Hoffmeister’s Meteorströme (1948) that are quite close to the time of maximum. Fourteen meteors came from a radiant at a = 129°, d = +24° on 1915 January 20 ( l = 301°), 24 and three meteors came from a radiant at a = 122°, d = +21° on 1937 January 12 (l = 292.5°).25 Interestingly, there is no trace of this stream among the thousands of radiants reported by the American Meteor Society during early to mid twentieth century. Following the publication of Lindblad’s paper, A. F. Cook (1973) included the Delta Cancrids in his paper “A Working List of Meteor Streams” in 1973.26 The fi rst apparent con fi rmations of visual activity from this stream were published in the newsletter Meteor News that was published by long-time American Meteor Society members K. and W. Simmons. They noted that B. Gates (Albuquerque, New Mexico, USA) plotted two meteors that he saw using 7 × 50 binoculars during 3 h and 46 min on 1974 January 19. These indicated a radiant at a = 128.25°, d = +18.6°. 27 On the nights of 1975 January 16/17 and January 17/18, N. W. McLeod, III, (Florida, USA) saw 12 meteors from the radiant during seven total hours of observing. He noted the meteors were “Geminid-like, fairly slow and bright.” 28 Several observations were published in Meteor News in 1977. On January 15/16, J. West and G. Shearer observed in Bryan, Texas (USA) and saw seven Delta Cancrids in 2 h 17 min, while P. Jones (St. Augustine, Florida, USA) saw two in 2 h. On January 21/22, McLeod reported observations of six meteors in 4 h, while 20 2 January Meteor Showers

F. Martinez (Florida) saw four in the same period. The same two observers also observed on January 22/23, with the former seeing one meteor in 3 h, while the latter saw none in 3 h and 38 min.29 An analysis by Gates using the available observations of 1974, 1975, and 1977, reveals probable activity levels of 2–3 per hour on the night of maximum.30 Additional reports were published in the 1980s and into the early 1990s, but hourly rates rarely exceeded one, and it seems that most observers just lost interest. An excellent example is long-time meteor observer R. Taibi (Maryland, USA). He saw one Delta Cancrid in 1 h of observing on 1986 January 17 and then failed to see any meteors from this stream during sessions of 1.0–1.5 h on 1991 January 14, 1992 January 6, and 1992 January 12. He said he just ignored the Delta Cancrids thereafter.31 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by video cameras from 1993 to 2012. Two separate sets of data are given for the “Northern Delta Cancrids,” representing two very similar, most likely related streams. The fi rst stream is composed of a total of 12 radiants, based on 502 meteors. The earliest detection was on January 8 ( l = 287°) and the last was on January 18 (l = 298°). The maximum occurred on January 14 ( l = 294°) from a radiant of a = 126.4°, d = +16.0°. The radiant drift was given as −0.7° in a and −0.9° in d. The second stream is composed of a total of 10 radiants, based on 392 meteors. The earliest detection was on January 19 ( l = 299°) and the last was on January 28 ( l = 308°). The maximum occurred on January 20 ( l = 300°) from a radiant of a = 135.3°, d = +17.5°. The radiant drift was given as −0.2° in a and −0.3° in d . Although the second stream begins just as the fi rst is ending, it actually begins with the radiant shifted several degrees to the east. It should be noted that this radiant sits in the antihelion location of the sky in January, meaning that an in fl ux of sporadic meteors from this region are likely contaminating the Delta Cancrid data. Nevertheless, there is a surprising consis- tency in the determined radiant and orbit during different surveys. Several orbits have been calculated for this meteor stream. The orbit labeled “1952–1954” is that determined by Lindblad. The orbit labeled “1961–1965” was determined by Sekanina (1973). The orbit labeled “1968–1969” was determined by Sekanina (1976).

w W (2000) i q e a 1952–1954 281.6 298.1 0.3 0.448 0.800 2.27 1961–1965 287.6 293.2 1.2 0.425 0.777 1.90 1968–1969 291.1 297.3 1.5 0.397 0.783 1.83

A radar survey was conducted at Adelaide University (South Australia, Australia) in 1961. C. S. Nilsson (1964) analyzed the data and found six meteors from a possible southern branch of this stream, which has a radiant about 5° south of the main radiant. The orbit is labeled “1961.” Although there is no trace of this branch among the various lists of visual meteor radiants, some of the photographic meteors noted by Lindblad may be from this branch. Canum Venaticids 21

w W (2000) i q e a 1961 116.8 120.1 4.9 0.371 0.77 1.61

Canum Venaticids

Z. Sekanina (1973) discovered this stream while analyzing the data gathered during the 1961–1965 session of the Radio Meteor Project. It was called the “Canids.” The duration was given as January 14–30, while the nodal crossing came on January 24.2 (l = 303.7°) when the radiant was at a = 111.8°, d = +9.7°. The geocentric velocity was determined as 17.1 km/s.20 The 1968–1969 session of the Radio Meteor Project revealed a nodal passage on January 15.5, (l = 294.8°) when the radiant was at a = 105.5°, d = +20.2°; however, the radio equipment did not operate during January 18–26, so the date might be somewhat biased. The geocentric velocity was determined as19.8 km/s.32 The orbit labeled “1961–1965” is based on nine meteors, while the orbit labeled “1968–1969” is based on 11 meteors.

w W (2000) i q e a 1961–1965 66.0 124.4 6.1 0.751 0.666 2.25 1968–1969 70.4 115.3 1.4 0.700 0.770 3.05

By examining the raw meteor orbits used by Sekanina, it can be noted that the orbit determined from the 1961 to 1965 data included several meteors with inclinations above 10° [subsequently lowering the average declination]. Only one such meteor orbit was present in the data from the 1968 to 1969 survey. By combining all of the meteors from both radar sessions, a new average orbit was determined and several new members were located that had been previously missed. The orbit that follows is based on 18 radar meteor orbits.

w W (2000) i q e a 70.7 123.1 4.5 0.727 0.656 2.11

The average radiant is a = 113.4°, d = +12.6°, while the daily motion is +0.97° in a and −0.35° in d . Visual observations are rare or nonexistent, and no other radar survey has detected this stream. 22 2 January Meteor Showers

Eta Carinids

C. S. Nilsson (1962) discovered this meteor stream while analyzing radio-echo observations made at Adelaide Observatory (South Australia, Australia) in 1961. Three meteor orbits indicated a nodal passage on January 19, when the radiant was at a = 156°, d = −65.33 The Eta Carinids were again noted when radio observations were made at Adelaide Observatory in 1969. G. Gartrell and W. G. Elford (1975) said the equipment operated only from January 21–23, but noted three meteors from an average radiant at a = 160°, d = −63°. The authors noted a similarity between this stream and other streams detected in December and February and suggested they made up a family of high-inclination, low-eccentricity streams.34 Although no indication was found of visual activity among the numerous visual radiant lists from the nineteenth century through the ﬁ rst half of the twentieth century, observers in the Southern Hemisphere have successfully observed meteors from this radiant. Most notably, M. Buhagiar (Perth, Western Australia, Australia) published a list of observations he made from 1969 to 1980 and reported weak activity from this stream during January 14–28. He said maximum came on January 21, when the radiant was at a = 163°, d = −57°. The maximum hourly rate was only one.35 Members of the Western Australian Meteor Section (WAMS) obtained an excellent set of observations of this shower in 1979. Meteors were observed during January 14–27, from an average radiant at a = 160°, d = −58°. Meteors were most numerous on the night of January 25/26, when the ZHR was about 2. Under skies with visual limiting magnitudes ranging from 5.0 to 6.5, observers detected 16 meteors and determined the average meteor magnitude as 3.75 (the brightest meteors were of magnitude 2). None of the meteors left trains, and all seemed white in color. The shower was again observed from 1980 January 19–27. On this occasion, a maximum ZHR was about three meteors was noted on January 21, from an average radiant at a = 160°, d = −59°. Although observed in 1982, the shower was virtually nonexistent during the interval of 1983–1986.36 The orbit labeled “1961” is from Nilsson (1962). The orbit labeled “1969” is from Gartrell and Elford (1975).

w W (2000) i q e a 1961 0 120 70 0.98 0.59 2.38 1969 7 123 74.3 0.98 0.64 2.94

Theta Coronae Borealids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) communicated the discovery of 13 new meteor showers using the Canadian Meteor Orbit Radar (CMOR) from 2002 to 2006. Theta Coronae Borealids 23

The Theta Coronae Borealids were said to span the period of January 14–24 ( l = 293°–303°), with its maximum coming on January 17 (l = 296.5°) from a radiant at a = 232.3°, d = +35.8°. The geocentric velocity was given as 38.7 km/s, while the radiant’s daily motion was determined as +0.70° in a and −0.06° in d .11 Complete details were published in the journal Icarus in 2008. 12 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was a little longer than indicated in the earlier paper, running from January 8–25 ( l = 287°– 304°), the radiant was located at a = 233.6°, d = +34.4°, and the geocentric velocity was determined as 37.7 km/s. Perhaps the largest difference from the previous results was the radiant’s daily motion, which was determined as +0.3° in a and +0.16° in d .13 There are some large differences between the orbits published in these two papers. The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 1,123 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 3,560 meteor orbits.

w W (2000) i q e a 2002–2006 112.2 296.5 77.1 0.884 0.2080 1.1 2002–2008 98.20 296.0 76.0 0.8601 0.172 1.04

The International Meteor Organization has a website containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. The Theta Coronae Borealids are based on 189 meteors. The duration is given as January 14–19 ( l = 294°–299°), while maximum occurs on January 16 ( l = 296°) from a radiant at a = 235.0°, d = +50.5°. The radiant drift was determined as +0.3° in a and +2.3° in d per day.37 Sparse visual evidence for this meteor shower extends back into the nineteenth century, with the earliest observation being that of G. Zezioli (Bergamo, Italy). Based on his observations spanning 1867–1869, he detected a radiant at a = 232°, d = +36° on January 18.38 G. V. Schiaparelli (1872) mentioned this observation again, commenting that it was, “A splendidly well-de ﬁ ned meteor shower. Jan. 18 (traces on Jan. 19), 1869.” 39 This seems to be the only deﬁ nite visual observation until Alexander Stewart Herschel reported seeing meteors from a radiant of a = 226°, d = +35° during 1901 January 24–25. He called this shower the “Theta Coronids.” 40 Among thousands of radiants determined by members of the American Meteor Society for over half a century, it seems that A. Pearlmutter (Forest Hills, New York, USA) detected activity on 1951 January 5.3 (l = 284.1°), with 11 meteors indicating a radiant at a = 235°, d = +29°. 41 24 2 January Meteor Showers

Xi Coronae Borealids

w W (2000) i q e a 2002–2006 123.1 294.5 79.4 0.805 0.6884 2.6 2002–2008 123.70 295.0 79.3 0.8007 0.718 2.84

January Draconids

The evidence supporting this stream’s existence is scant, but what makes it most interesting is that the available observations seem to point to a fairly short-duration shower—meaning that it could be easily missed. The greatest support for this stream appeared during Z. Sekanina’s 1969 session of the Radio Meteor Project. A total of 32 meteors were detected from January 13 to 17 from an average radiant of a = 245.9°, d = +62.4°.2 The orbit was as follows: Rho Geminids: Antihelion 25

w W (2000) i q e a 185.8 296.0 44.9 0.979 0.449 1.78

Possible visual observations are rare, possibly due to the short duration. In the nineteenth century, G. Zezioli (Bergamo, Italy) plotted several meteors from 1867 to 1869 January 16, which G. V. Schiaparelli derived a radiant of a = 244°, d = +64°,43 while W. F. Denning’s investigation of the records of the Italian Meteoric Association revealed six meteors plotted from a = 241°, d = +63°, during 1872 January 1–15.21 In the twentieth century, visual observations were also scarce. R. Kingman (Bristol, England) plotted six meteors from a = 245°, d = +64°, from 1928 January 16–24. In C. Hoffmeister’s Meteorströme , a radiant designated 2877 was observed on 1937 January 13 (l = 293°), from a position of a = 236°, d = +59°. Among all of the photographic lists, only two meteors appear to be associated with this stream. Designated 6112 and 10081, they were detected on 1953 January 13 (l = 294°) and 1954 January 13 (l = 294°), respectively, and indicate an average radiant of a = 236°, d = +59°. Although the orbit is very similar to that determined by radar, the orbital inclination is about 15° greater.

w W (2000) i q e a 187.5 293.7 60.5 0.98 0.73 3.63

Rho Geminids: Antihelion

This meteor shower is near the eastern edge of the large “antihelion” radiant, which basically rises in the east as the sun is setting. The antihelion meteors are generally moving in low inclination, direct orbits around the sun and intercept Earth’s atmosphere at a perpendicular angle. These meteors are generally referred to as sporadic, with photographic and radar surveys detecting a variety of unrelated orbits. This is what makes the Rho Geminids a dif fi cult meteor stream to study. This meteor shower was discovered by R. B. Southworth and G. S. Hawkins (1963). In their analysis of 359 meteors photographed during the Harvard Meteor Program of 1952–1954, they identi fi ed four meteors as belonging to this stream, which were detected from January 15–28 from an average radiant at a = 109.4°, d = +32.3°.44 B. A. Lindblad (1971) confi rmed the stream, when he conducted a computerized stream search using 865 precise meteor orbits from the Harvard Meteor Project. He found six meteors over the period of January 15–27 and gave the average radiant as a = 110°, d = +29°.45 Z. Sekanina (1973, 1976) recognized this stream in both sessions of the Radio Meteor Project. From 1961 to 1965, a total of 13 meteors were noted during 26 2 January Meteor Showers

December 28-January 16. The apparent nodal passage came on January 7.9 ( l = 287.0°) and the radiant was at a = 108.8°, d = +31.5°. The geocentric velocity was determined as 21.8 km/s.20 Despite the fact that photographic data plainly showed activity to January 27, the radar was not in operation at the appropriate time to detect these meteors from January 17 to 25. During the 1968–1969 survey, Sekanina noted 25 meteors over the period of January 13–28. The nodal passage came on January 20.8, when the radiant was at a = 125.1°, d = +24.9°. The geocentric velocity was determined as 20.9 km/s.2 On this occasion the radar did not operate from December 21-January 12, and, although Sekanina named this stream the “January Cancrids,” it seems identical to the Rho Geminids, as can be seen in the “Orbit” section below. Dozens of papers providing lists of visually observed meteor radiants were searched. The earliest detection was apparently made by members of the Italian Meteoric Association from 1872 January 1 to 15, when eight meteors were plotted from an average radiant of a = 109°, d = +34°.21 The British Astronomical Association reported that H. Corder and W. F. Denning spotted quick meteors from a radiant of a = 107°, d = +25° on 1894 January 1–2. However, while these could provide con ﬁ rmation of the stream’s early activity, the fact that it is missing from so many other lists indicates that these radiants might have been produced by chance alignments. This meteor radiant is present in two prominent visual surveys in the ﬁ rst half of the twentieth century. C. Hoffmeister’s Meteorströme reveals that a radiant at a = 109°, d = +30° was detected on 1921 January 14.5 (l = 293.8°), while another radiant was detected at a = 109°, d = +29° on 1931 January 10 (l = 289.3°).46 E. Öpik’s analysis of the Arizona Expedition for the Study of Meteors revealed a radiant at a = 107°, d = +30° on 1933 January 15/16.47 The analysis of the raw orbital data obtained from both sessions of the Radio Meteor Project reveals the stream’s daily motion to be +1.1° in a and −0.2° in d . Although the radiants and orbits of the photographic and radar data are very similar—certainly indicating an association—there seems to be an indication that two distinct populations of meteors exist. Concerning the population of radar meteors, it is interesting that a trend seems to exist which involves a slow decrease in the semimajor axis during the shower’s period of activity. There also seems to be an association with the Delta Cancrids. The International Meteor Organization’s video meteor network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras from 1993 to 2012. The Rho Geminids are present on three nights. On January 5 (l = 284.0), 97 meteors indicated a radiant at a = 111.7°, d = +27.0°. On January 6 (l = 285.0), 70 meteors indicated a radiant at a = 111.0°, d = +27.0°. Two radiants were detected on January 7 ( l = 286.0), when 62 meteors indicated a radiant at a = 115.0°, d = +28.0° and 49 meteors indicated a radiant at a = 105.6°, d = +30.5°. 48 The orbit labeled “1952–1954” is from Lindblad (1971). The orbit labeled 1961–1965 is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). Alpha Leonids: Antihelion 27

w W (2000) i q e a 1952–1954 243.3 302.2 3.5 0.77 0.710 2.66 1961–1965 266.2 287.8 6.4 0.594 0.734 2.23 1968–1969 271.3 301.0 3.7 0.576 0.684 1.82

Alpha Hydrids

w W (2000) i q e a 2002–2006 116.9 105.5 58.5 0.282 0.9677 8.7 2002–2008 115.64 106.0 57.0 0.2910 0.966 8.62

Alpha Leonids: Antihelion

The strongest evidence for this stream’s existence comes from the two sessions of the Radio Meteor Project conducted at Havana, Illinois (USA) in the 1960s. Z. Sekanina (1973) analyzed the data from the 1961 to 1965 session and noted a 28 2 January Meteor Showers

duration of December 28 to February 13. The date of the nodal passage came on January 23.5 (l = 302.9°) from a radiant at a = 152.9°, d = +12.0°. The geocentric velocity was determined as 33.1 km/s.20 Sekanina (1976) found the stream again while analyzing the data from the 1968 to 1969 session. The duration was given as January 13 to February 13, while the nodal passage occurred on January 31.1 ( l = 310.7°), when the radiant was at a = 158.6°, d = +6.4°. The geocentric velocity was determined as 27.2 km/s.51 It should be noted that the equipment did not operate from 1968 December 21 to 1969 January 12, so an earlier extension to the duration could have been missed. The equipment was also shut down from 1969 February 14 to 24, so later activity would also have been missed. Although there are no convincing visual observations of the Alpha Leonids, a meteor of magnitude 1.6 was photographed on 1953 February 18, during the Harvard Meteor Project. Richard Eugene McCrosky and Annette Posen included the meteor in their list of 2,529 photographic meteor orbits. Designated trail “6488”, the radiant was given as a = 176°, d = −4° and the geocentric velocity was 27.3 km/s. There are other meteors present in the data acquired by the Harvard Meteor Project that might be Alpha Leonids (with the earliest being detected on January 16); however, further studies of this radiant are necessary before the true extent of its orbit is known.52 This meteor shower is within the Antihelion region of the sky when near its peak during the last week of January. The International Meteor Organization’s video meteor network created a website titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the Alpha Leonids are present within this sample. Using the solar longitudes representing the nodal passages of the stream in the two sessions of the Radio Meteor Project, there are radiants quite close to those determined by Sekanina. Under l = 303, a radiant at a = 152.5°, d = +6.5° was delineated by 52 meteors. Under l = 310°, a radiant at a = 164.5°, d = +11.0° was delineated by 34 meteors.48 The orbit labeled “1953” is the photographic meteor from McCrosky and Posen (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976).

w W (2000) i q e a 1953 145 150 9 0.19 0.80 0.95 1961–1965 325.4 303.8 1.8 0.142 0.898 1.40 1968–1969 143.3 131.3 3.7 0.198 0.801 0.99

The stream’s low orbital inclination has apparently made it dif ﬁ cult to ﬁ rmly establish the its ascending node, thus, although the shape of the orbital plane is well established, the w and W are differing by nearly 180°. January Leonids 29

January Leonids

This meteor stream was discovered amongst more than 2.5 million meteoroids detected by the Canadian Meteor Orbit Radar (CMOR) during 2002–2006.53 A total of 138 meteors indicated a duration of January 1–5 ( l = 280°–284°), with maximum occurring on January 3 (l = 282.5°) from a radiant at a = 148.3°, d = +23.9°. The radiant drift was determined as +0.66° in a and −0.14° in d , while the geocentric velocity was determined as 52.7 km/s. The following orbit was provided:

w W (2000) i q e a 333.9 282.5 105.3 0.053 0.994 8.7

A couple of years later, the expanded results for the CMOR were published, which now included over three million orbits up to 2008.13 A total of 1,160 meteor orbits were included, which indicated a duration of December 31-January 8 ( l = 279°–287°), with maximum occurring on January 3 (l = 282°) from a radiant at a = 148.2°, d = +23.7°. The radiant drift was determined as +0.7° in a and −0.13° in d , while the geocentric velocity was determined as 52.3 km/s. The following orbit was given:

w W (2000) i q e a 334.71 282.0 107.9 0.0517 0.990 5.34

A search through dozens of nineteenth and twentieth century papers, which provided lists of visual radiants, revealed only one radiant that might be the January Leonids. American Meteor Society radiant number 4465 was a radiant detected by G. Bream (Gardners, Pennsylvania, USA) on 1962 January 4.3 (l = 283.5°). He plotted three meteors and determined the radiant as a = 151.0°, d = +27.5°.54 It could be that this is simply a chance alignment. Meanwhile, amateur astronomers have been successfully detecting meteors from this stream using sensitive video cameras since the ﬁ rst half of the 1990s. Searches through the list of video meteor orbits of the Dutch and Japanese have revealed a few members, but the Million Meteors database of the International Meteor Organization has captured 256 meteors that pinpointed eight radiants spanning December 31-January 3 (l = 279°–282°). Maximum occurs on January 2 ( l = 281°) from a radiant at a = 147.0°, d = +24.1°.55 30 2 January Meteor Showers

Quadrantids

Duration: December 28 to January 9 (l = 277°–289°) Maximum: January 3 (l = 283.16°) Radiant: a = 230°, d = +49° ZHR: 120

Radiant Drift: a = +1.0°, d = −0.2° V G : 29 km/s

This is one of the major annual meteor showers, with maximum hourly rates exceeding 100; however, it exhibits such a sharp rise to maximum, that the peak is only visible to a small part of the world each year.

Discovery

The fi rst documented observation of the Quadrantids seems to have occurred on the morning of 1825 January 2. In the February 1825 issue of Antologia , A. Brucalassi (Tuscany, Italy) provided details of a brilliant meteor that he observed. He added that the night was “quiet, but very cold, the sky was clear, and … after the appearance of the meteor you saw roam many of the so-called shooting stars, as in the warm evenings’ summer.”56 Three observations were made in the 1830s. L. F. Wartmann (Mornex, Switzerland) said that E. Reynier (Les Planchettes, Switzerland) reported the “appearance of extraordinary shooting stars” at 3 a.m. (local time) on 1838 January 2. Wartmann added that he saw “a similar phenomenon” from 4 a.m. (local time) until daybreak on 1835 January 2.57 Although Wartmann seemed to have linked his observation to that made by Reynier 3 years later, no mention of a possible annual display was mentioned. A. Bravais (Bossekop, Norway) observed the aurora borealis on the night of 1839 January 2/3 and wrote that it was “remarkable for us by the number of shooting stars.”58 Two individuals independently came to the conclusion that an annual meteor shower occurred during the fi rst days of January. First, E. C. Herrick (New Haven, Connecticut, USA) wrote a letter to the American Journal of Science and Arts on 1838 December 24 and made a suggestion about the existence of this meteor shower, when he included the date of January 2 among “other seasons in the year at which meteors may possibly be found unusually numerous.”59 L. A. J. Quetelet (Brussels Observatory, Belgium) gave a presentation to the Brussels Royal Academy of Sciences on 1839 June 8, discussing the observations of Wartmann and Reynier and suggesting this period was “deserving of attention” and that the phenomenon occurred “in the last part of the night.”60 Despite these statements, observations of this newly discovered meteor shower were not plentiful. During the 1840 February 1 session of the Brussels Royal Academy of Sciences, Quetelet presented a note from F. Duprez (Ghent, Belgium), which said that meteors “appeared in greater numbers than usual on the night of [1840] January 2–3.” Duprez observed from 4:00 to 6:00 a.m., reporting 27 meteors Quadrantids 31 in the fi rst hour and 23 in the second. He added, “These meteors are observed by a very pronounced parallelism in their direction,” which he said inticated “a common origin.” Duprez said he sometimes saw two meteors from the same point in the sky at the same time.61 Following the observation of Duprez, Wartmann wrote, “Among the remarkable nights where meteors appear periodically in large numbers [is] that of January 2–3 ….” He said the meteors are most plentiful “from midnight till daybreak.” Wartmann added that he thought he was the fi rst to mention this, 62 but, as noted earlier, he said nothing speci fi c about a possible annual shower. The next observations of this meteor shower came in early January 1848. A. Colla (Parma, Italy) saw “a special appearance of shooting stars” on the night of January 2/3.63 E. Heis (Aachen, Germany) saw “Many falling stars” around 6:00 a.m. on January 2.64 E. J. Lowe (Nottingham, Nottinghamshire, England) reported “several small falling stars” were seen after 6:00 p.m. on January 4.65

Observations

Up until 1863, little else was known about this meteor shower, other than a large number of meteors were sometimes seen during the fi rst days of January, but this changed when S. Masterman (Weld, Maine, USA) saw “eight very luminous excur- sions” before daybreak on 1863 January 2. He said the meteors came from a = 238.0°, d = +46.4°. Masterman noted that moonlight and the cold temperature made it “uncomfortable being out in the open air for any considerable time [and] made it unfavorable for observing for meteors.”66 In the Report for the Annual Meeting of the British Association for the Advancement of Science (1865), observations are given by Lowe, R. P. Greg (Prestwitch, Greater Manchester, England), and A. S. Herschel (Hawkhurst, Kent, England) for 1864 January 2. During 7:30–8:30 p.m., Lowe noted “very many meteors” were seen. From 10:00 p.m. to 1:00 a.m., Greg saw 50 meteors in “all parts of the sky.” He said one of the radiant points was in the head of Boötes. From 10:00 p.m. to midnight, Herschel saw 50 meteors in all parts of the sky. He noted a “very de fi nite” radiant was located “at c Quadrantis Muralis.” Greg used the plots of meteors seen on this night by Herschel, himself, and others to determine the radiant as a = 234.0°, d = +50.9° (1864). 67 The fi rst person to analyze this meteor shower was D. Kirkwood (1873), who read his paper titled “On the Meteors of January 2nd” before the American Philosophical Society on 1873 November 21. He tabulated the known observations and even included a meteor shower from 848 December 2. Concerning this observation from over a millennium ago, Kirkwood wrote, “Modern observations of this shower have not been suf fi cient to determine the rate of its nodal motion: it may be worthy of remark, however, that a progressive movement equal to that of the meteors of November 14th [Leonids] , would bring the display of December 2nd, A.D. 848, forward to the epoch of January 2nd.” With respect to the other listed displays, 32 2 January Meteor Showers

Kirkwood noted the 1825 display, a group of displays between 1835 and 1840, and another group between 1862 and 1865. Not being aware of the displays in the years between these groups, Kirkwood said there was an indication of a 13-year period, which he determined would indicate this meteor stream has an aphelion distance of 10.06 AU. Kirkwood then noted that E. Weiss had shown that comet C/1860 U1 had its ascending node “very near the point passed by the earth about the 3d of January” and suggested this as the possible source of the meteors.68 The orbit of this comet is fairly uncertain, as it was based on observations spanning only 3 days.69 T. W. Backhouse (1884) analyzed this meteor shower using his personal observations made from 1859 to 1883. He said the meteor shower began at a solar longitude of 280.1°, reached maximum at a solar longitude of 281.9°, and ended at a solar longitude of 283.9°. He determined that the peak “zenithal horary number” reached 51, at which time the radiant was at a = 233°, d = +49°. 70 W. E. Besley (1900) summarized some of the details about the Quadrantids in the 1900 January issue of The Observatory . He listed numerous observations spanning 1835 through 1897, showing that the rates fl uctuated from year to year, with the lowest rates being 4 per hour and the highest rates being 60 per hour. Besley added, “It has been assumed that the returns of the Quadrantids are governed by a 13-year period, but the amount of evidence in favour of this theory does not seem to be satisfactory.”71 Very high rates of meteors were observed on 1909 January 2 by P. M. Ryves (Zaragoza, Spain). He indicated that from 4:50 to 6:00 a.m. (local time), he counted 210 meteors, noting three brighter than Venus and fi ve between magnitude 0 and 1. Ryves added that he had never seen the Perseid display this strong.72 W. J. Fisher (1930) of Harvard College Observatory (Massachusetts, USA) provided a very comprehensive list of observations of the Quadrantids that spanned the period of 1835–1927. He noted that the fi ve highest hourly rates of meteors reported for the Quadrantids were in 1864 (60), 1879 (>42), 1897 (64), 1909 (180), and 1922 (50). Fisher wrote, “These dates correspond to a mean cycle of 14.6 years, which may perhaps be also the period of the Quadrantid stream.”73 On the night of 1929 January 2/3, photographic telescopes were in use at Harvard College Observatory, mostly conducting regular program work. As it turned out, three meteors were photographed on four different 8 × 10 in. plates. Noting that these might have been the fi rst Quadrantids ever photographed, Fisher and M. Olmsted made a careful reduction of the meteor trails. Two of the trails were “so nearly parallel that they determine an intersection very poorly.” Fortunately, the third trail made “a very good intersection with the other two….” Although this third trail was photographed when the radiant was near the northern horizon, and may have suffered “the effects of zenith attraction and diurnal aberration,” Fisher and Olmsted determined the radiant as a = 231.8°, d = +48.3°. 74 Astronomers at the Jodrell Bank Experimental Station (Lower Withington, Cheshire, England) made the fi rst radio-echo observations of the Quadrantids. The results were discussed by G. S. Hawkins and M. Almond (1952). They noted that activity had been detected from this meteor shower in every year from 1947 to 1951. The weighted mean radiant position was given as a = 231.2°, d = +9.0° and Quadrantids 33 the radiant diameter ranged from 4° to 12°. During the 1950–1951 appearance, the Quadrantid radiant moved from a = 224°, d = +52° on 1950 December 28 to a = 226°, d = +61° by 1951 January 7. The shower peaked on January 3, when hourly rates reached 90, and the radiant was then at a = 233°, d = +52°.75 Investigating 122 observations of this shower made between 1864 and 1953, J. P. M. Prentice (1953) states that while the normal ZHR of the Quadrantids was 45, the numbers could actually fl uctuate quite a bit, citing very strong returns in 1909 (ZHR = 202) and 1922 (ZHR = 79), while very weak returns were noted in 1901 (ZHR = 17), 1927 (ZHR = 20) and 1940 (ZHR = 21). One fi gure Prentice did fi nd more consistent was solar longitude at maximum, which he determined as 282.9° 76; however, it should be stressed that this represents only visual observations. During the Jodrell Bank observations noted earlier, the average time of maximum occurred when Earth was at a heliocentric longitude of 282.5°. 77 This difference between the times of the maximum of visual and radio-echo meteors illustrates the dispersion due to the Poynting-Robertson effect. According to K. B. Hindley (1971), the dispersion factor amounts to 68 min of time per magnitude, 78 thus allow- ing the radar maximum to occur 6.3 h before the visual maximum. Hindley (1972) uncovered additional details about the Quadrantids. He used observations acquired by members of the British Astronomical Association (BAA) made during the period 1965–1971 and noted rates were higher than half the maximum rate for only 16 h.79 Hindley (1971) used an IBM360/65 computer at the University of Liverpool to analyze telescopic observations of the Quadrantids. The computer revealed a normal radiant diameter of 8°, which contracts to less than a degree at the time of maximum, indicating the stream is made up of both a diffuse and compact component.78 Unfortunately, the Quadrantids have not been consistently studied by visual observers. Cold weather prevalent in northern latitudes has frequently been cited as the main reason behind this. Another factor is the very short period of maximum activity, which frequently causes even the most diligent of observers to miss the peak only because they are in the wrong longitude. A fi nal factor is related to the general faintness of this shower’s meteors, thus requiring exceptional observing conditions for the main activity of the shower to be noted. Examination of the photographic and radio-echo data reveals the average Quadrantid radiant to be at a = 229.5°, d = 49.4°, but it should be pointed out that this is strictly an average . As mentioned earlier, the shower does not exhibit a sharply de fi ned radiant. In 1953, G. E. D. Alcock and Prentice pointed out that “it has always been dif fi cult to determine the radiant of the Quadrantid shower.” To correct this, they carried out a program in 1952 to obtain duplicate observations of radiants. On January 3, they established the existence of 13 active radiants, thus demonstrating the complexity of the region.80 Other studies have shown that the region is even more complex, since the same radiants are not necessarily active from year to year. The earliest mention of this was in 1918, when W. F. Denning and F. Wilson noted their surprise to fi nd the main radiant in 1918 January to be about 8° north of the normal radiant. They stated that a more northern radiant had been suspected in January of 1916 and 1917, “but 34 2 January Meteor Showers

Quadrantids 160

140

120

100 Z H 80 R 60

0 253 263 273 283 293 303 313 Solar Longitude

This represents a decade of observations of the Quadrantid meteor shower. The observations were made by members of the International Meteor Organization during the 2000s. The solar longitude basically represents 60 days, illustrating the short duration and very sudden rise and fall of activity at maximum the data at the time were regarded as insuf ﬁ cient.” Independent con ﬁ rmations of the 1918 radiant came from several observers in England and it was noted that a weak shower actually did occur from the normal radiant as well.81 This apparent change in active radiants from year to year is probably a by-product of the perturbations experienced by the stream courtesy of Jupiter.

Past and Future Evolution

The planet Jupiter frequently appears in literature concerning the Quadrantids. In addition to the radiant changes mentioned above, it has been linked to the initial appearance of the shower in the early nineteenth century and to the occasional irregularity in hourly rates. Also considered a result of perturbations is the slow retrogression of the ascending node, an occurrence which attracted four studies between 1958 and 1972. The subsequent calculated rates of the nodal retrogression were 0.31°/century,82 0.41°/century, 83 0.54°/century, 84 and 0.6°/century.85 S. E. Hamid and M. N. Youssef (1963) published one of the fi rst studies of the long-term gravitational effects of Jupiter on this stream.84 They took six doubly photographed meteors from 1954 and applied the secular perturbations of Jupiter during the last 5,000 years. They noted that both the present inclination of 72° and the perihelion distance of about 1 AU were at their lowest values of 13° and 0.1 AU, respectively, 1,500 years ago. About 4,000 years ago, these values were very similar to what they are today, with the inclination being 76° and the perihelion distance being about 1 AU. As a study of why the meteor stream is composed of at least two Quadrantids 35 branches, the authors examined the change in the stream’s distance from Jupiter over the last 5,000 years. Prior to today’s distance of only 0.3 AU, the stream was found to have been farthest from Jupiter 1,500 years ago and only 0.2 AU away about 4,000 years ago. The authors speculated that the stream’s parent comet was captured by Jupiter about 4,000 years ago, and shortly thereafter it developed meteors along its path. “Because an appreciable number of these meteors, which now form the Quadrantids, did not suffer another close approach to Jupiter, the shower is observed to be compact.” Later in 1963, as a by-product of this study, Hamid and Whipple suggested a possible common origin for the Quadrantids and the Delta Aquariids, as 1,300– 1,400 years ago the orbital planes and perihelion distances were very similar.86 They also added, “the physical characteristics of the meteoroids belonging to the two streams appear to be similar, as judged by their light curves.” I. P. Williams, C. D. Murray, and D. W. Hughes (1979) essentially repeated the Hamid-Youssef study, but they used a stream model and ten “test” meteoroids scattered about the orbit. Their study basically con fi rmed the earlier study back to 1,500 years ago, but found the inclination and perihelion distance to closely re fl ect today’s values only 3,000 years ago. The study also indicated that, “casual observations of the original meteoroids at any time in the interval 200–1,000 year before the present would not have revealed them to be members of the same stream. 1,690 and 1,300 year ago they started off with similar orbits; these then separated, only coming together again in the last 200–150 year.” The authors added that the parent comet probably underwent two major disruptions—one 1,300 years ago and the other 1,690 years ago. The future of the Quadrantid stream was also examined in the 1979 study. The authors noted that the inclination would remain near 72° and that the perihelion distance eventually will exceed 1 AU. Therefore, the authors predict Earth will no longer encounter the stream by the year 2,400.87 A much younger Quadrantid stream was described by P. Jenniskens, H. Betlem, M. C. de Lignie, M. Langbroek, and M. van Vliet (1997). In reducing the orbits for 35 doubly-observed photographic meteors and 29 doubly-observed video meteors that were obtained by the Dutch Meteor Society, the authors produced “the fi rst large set of precisely reduced orbits of Quadrantid meteoroids.” One of the most striking results was the stream structure. Previous studies revealed a large dispersion of the semimajor axis, but this one revealed a small dispersion, with “most orbits … confi ned between the 2:1 and 2:3 resonances with Jupiter at a = 2.62 and a = 3.49 AU, respectively.” They also said the photographic data indicated the orbits were clustered around inclinations of 71.2° and 72.8° and noted, “Because there is no instrumental reason for this, we believe this to be a true stream structure.” They added that when only the best orbits were averaged, there is a trend involving the inclination and semimajor axis, such that orbits with an inclination of 72.8° are at the 2:3 resonance, those at 71.9° are at the 3:5 resonance, and those at 71.4° are at the 2:1 resonance. Finally, another discovery was a systematic difference between the mass of the meteors and the radiant location. The fainter video meteors originate from a radiant 0.5° higher in a and 0.4° lower in d than the radiant of the brighter photographic meteors. Jenniskens et al. concluded 36 2 January Meteor Showers that “the main peak represents an ‘outburst’ component, much like other near- comet type outbursts, while the background component is the classical ‘annual’ stream.” They added, “These observations are not consistent with models that assume that the ‘outburst’ dust was ejected from a parent body more than about 500 years ago. Hence, an origin from comet 96P/Machholz 1, which is now in a much different orbit, is excluded. Rather, the parent may hide as an asteroidal object in a high inclination orbit.”88 Jenniskens (2004) revisited the evolution of the Quadrantid stream shortly after the discovery of minor planet 2003 EH1. He integrated the orbit of this minor planet back to 1,600 and then created a range of orbits with a variety of progres- sively higher semimajor axis. These were then integrated forward and revealed “a progressive scatter as a function of time since ejection but, overall, follow the evolution of 2003 EH1, as required for this object to be associated with the stream.” Jenniskens then compared the resulting orbits with the photographic observations mentioned in his 1997 paper and wrote, “I con fi rm that the estimated time of release of the particles is a few 100 years prior to 1600 c.e .” 89 P. A. Wiegert and P. G. Brown (2004) examined the idea of a much younger Quadrantid stream a few months later. They integrated the orbit of minor planet 2003 EH1 backwards to 1491 and then simulated outbursts. Each outburst was simulated using 16 sets of 500 hypothetical meteors, with each set representing a different ejection velocity. The outburst material was then integrated forward. Wiegert and Brown said that if 2003 EH1 was related to comet C/1490 Y1, Earth would have encountered the meteor stream in the early 1600s. If the release occurred about 400 years ago, as suggested by Jenniskens, Earth would have began encountering the highest velocity meteors by the late 1600s, the lowest velocity meteors by 1800, and all other meteors in between during the 1700s. They then noted that a release in 1800 “produces meteors at the Earth in 20–30 years at all ejection speeds.” Since no trace of the Quadrantids exists prior to the early 1800s, Wiegert and Brown said the core of the stream is only about 200 years old.90

Associations

For years, no parent to the Quadrantids was recognized. The potential link to the Delta Aquariids was a possible indication that a parent no longer existed or had been perturbed into a different orbit by Jupiter. The ﬁ rst association to be suggested for this meteor stream was C/1860 D1 (Liais) by K. D. Pokrovsky and P. G. Shaine in 1919. The paper was mentioned by Fisher, who quoted them as saying, “it is a fact that the coordinates of the radiants of this stream are very nearly those of the radiant of comet 1860 I [C/1860 D1], of Liais, remarkable, like Biela’s comet, because of its division into two parts. It is reasonable that such a comet could father a stream of shooting stars.” Pokrovsky and Shaine Quadrantids 37 admitted that the predicted period of meteor activity for comet Liais was a month off from the observed peak of the Quadrantids, but noted, “one cannot always expect an exact coincidence in time and place of cometary and meteoric radiants.”91 I. Hasegawa (1979) wrote a paper titled “Orbits of Ancient and Medieval Comets,” where he calculated new orbits for 38 comets. He wrote, “It seems that Comet 1491 I [i.e., C/1490 Y1 ] may be the parent comet of Quadrantid meteors.” He said the improved orbit of the comet did not lie that far from Hamid and Youssef’s projected orbit for the Quadrantids in 1550.92 An interesting paper published by P. B. Babadzhanov and Y. V. Obrubov (1987) analyzed the long-term motion of the Quadrantids and found that eight theoretical meteor showers could exist. Six of these were linked to known meteor showers: Quadrantids, Ursids, Northern Delta Aquariids, Southern Delta Aquariids, Daytime Arietids, and the Alpha Cetids. 93 [The Alpha Cetids are not discussed in this book, because of weak evidence.] B. A. McIntosh (1990) mentioned a new potential comet association to the Quadrantids: comet 96P/Machholz. He noted that the long-term motion of this comet was remarkably similar to that reported for the Quadrantids by Hamid and Youssef, except for a distinct shift in time, which indicated the comet and meteor stream did not go through these orbital changes together. McIntosh also said that the longitude of perihelion of the comet was close to all of the streams mentioned by Babadzhanov and Obrubov, noting that the Delta Aquariids and Daytime Arietids experienced a similar orbital evolution in their past. He added that the ancient comet C/1490 Y1 could “possibly be included in this Jupiter-controlled complex.” McIntosh concluded that comet 96P was not necessarily the parent body, but that it and the Quadrantids were likely members of a large family of interplanetary bodies.94 The link between the Quadrantids and comet 96P was the subject of several additional papers published by other authors from 1991 to 1993. Williams and S. J. Collander-Brown (1998) suggested another association. They noted the strong similarity of the inclination, perihelion distance, and eccentricity of minor planet 5496 (1973 NA) to that determined for the Quadrantids indicates “some connection.” This Apollo-type minor planet is moving in a comet-like orbit and, based on observations of other astronomers, the authors believe 5496 “may be a dormant comet.” The authors noted, “that there are signi ﬁ cant differences between the values of the two orbital elements W and w for the Quadrantids and 5496.” They added, “These were the two orbital elements that are capable of very rapid changes. Hence the differences now may simply indicate that in the recent past either the orbit of the Quadrantids, or more likely, the orbit of 5496 has undergone such a rapid change.” Williams and Collander-Brown said the orbit evolution of 5496 was very similar to that of the Quadrantids.95

A few months after the discovery of minor planet 2003 EH1 [ now known by the of ﬁ cial number 196256] on 2003 March 6, Jenniskens (2003) suggested it was “a very strong candidate for the parent of the Quadrantid stream.” He added that the current theoretical radiant and time of maximum were “at the center of the Quadrantid radiants measured by photographic means.”96 38 2 January Meteor Showers

Orbit

Several orbits have been calculated for the Quadrantids over the years. W. Wenz (1908) determined the radiant from plots of meteors on January 3 and 4.97 The orbit labeled “1908” is his parabolic orbit. The orbit labeled “1951” is that calculated by Hawkins and Almond (1951). The orbit labeled “Photo” is based on 25 meteors photographed from 1936 to 1976 and published by F. L. Whipple (1954), 98 R. E. McCrosky and A. Posen (1961),99 P. B. Babadzhanov and E. N. Kramer (1967),100 and G. A. Harvey and E. F. Tedesco (1977).101 The orbit labeled “1961–1965” was determined by Z. Sekanina (1970) during the Radio Meteor Project.102 The orbit labeled “1995” was determined by de Lignie and K. Jobse (1995). 103 The orbit labeled “2002–2008” was determined by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) using 6,614 meteor orbits acquired by the Canadian Meteor Orbit Radar.104

w W (2000) i q e a 1908 170.7 283.9 70.0 0.97 1.0 ϱ 1951 166 283.2 67 0.97 0.44 1.7 Photo 160.5 283.3 71.4 0.975 0.614 2.53 1961–1965 168.1 283.0 70.3 0.974 0.682 3.06 1995 169.8 284.0 71.3 0.977 0.668 3.0 2002–2008 168.14 283.0 72.4 0.9746 0.709 3.35

Several bodies have been suggested as associated with the Quadrantids.

w W (2000) i q e a C/1860 D1 209.76 326.02 79.68 1.1989 1.0 ϱ C/1490 Y1 129.84 295.89 51.65 0.7376 1.0 ϱ 96P 14.757 94.323 58.308 0.1238 0.9592 3.034 5496 118.079 101.078 68.007 0.8845 0.6366 2.434

2003 EH 1 171.341 282.961 70.876 1.1894 0.6191 3.123

Daytime Xi Sagittariids

Z. Sekanina (1976) discovered this daytime stream during the 1968–1969 session of the Radio Meteor Project. This survey revealed the nodal passage on January 25.4 (l = 304.9°), as which time the radiant was at a = 283.2°, d = −21.9°. The geocentric velocity was determined as 24.4 km/s. Although the radio equipment did not January Xi Ursae Majorids 39 operate from January 18 to 26, meteors from this stream were detected before and after this period, so that the duration was given as January 15–31.2 J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy (2009) analyzed data acquired in 2006 and 2007 by the interferometric meteor radar facilities in Davis Station, Antarctica and Darwin, Australia. This meteor stream was detected from January 2 to 11. At the time of peak activity on January 7 ( l = 286.7°), the radiant was at a = 281.7°, d = −19.5°. They gave the name of the stream as “Chi Sagittariids.”105, 106 Analyzing data collected by the Canadian Meteor Orbit Radar (CMOR) from 2002 to 2008, P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 896 meteor orbits from this stream. They noted a duration of December 30 ( l = 278°) to January 17 ( l = 296°) and said the shower peaked on January 9 ( l = 288°), when the radiant was at a = 282.3°, d = −16.3°. The geocentric velocity was 25.3 km/s, while the daily motion of the radiant was determined as +0.77° in a and +0.12° in d . 104 The orbit labeled “1968–1969” is from Sekanina (1976), while the orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1968–1969 66.0 124.4 6.1 0.751 0.666 2.25 2002–2008 79.31 288.0 6.0 0.4708 0.784 2.18

January Xi Ursae Majorids

The discovery of this meteor shower was announced in 2009 by the Japanese video meteor network SonotaCo. During a survey spanning 2007–2008, they detected 12 meteors from a radiant at a = 169.0°, d = +33.0°. The radiant was active from January 17–27 (l = 296.8°–306.3°), with the peak occurring on January 21 ( l = 300.6°). The geocentric velocity was given as 40.2 km/s, while the radiant drift was determined as −0.13° in a and +0.01° in d per day. They referred to it as the “Xi Ursae Majorids.”107 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by the cameras of the Video Meteor Network from 1993 to 2012. Stream number 10 is called the “January Xi Ursae- Majorids” and is based on 209 meteors. The duration is given as January 15–20 ( l = 295°–300°), while maximum occurs on January 19 (l = 299°) from a radiant at a = 169.2°, d = +32.0°. The radiant drift was determined as +0.9° in a and −1.0° in d per day.108 [Vinf = 46.0 km/s]. A search through lists of visual radiants reveals only a few apparent observations of this meteor shower in the past. R. P. Greg (1865) compiled a list of radiants after looking through the catalogs of meteors published in the 1845–1863 issues of the 40 2 January Meteor Showers

Report for the Annual Meeting of the British Association for the Advancement of Science . He noted that 15 plotted meteors indicated a radiant at a = 173°, d = +32° that was active during January 5–25.109 G. W. Ridley (Alameda, California, USA) said 4–5 of his plotted meteors on 1931 January 16.9 indicated a radiant at a = 172.4°, d = +33.1°, while four plotted meteors on 1931 January 17.9 indicated a radiant at a = 172.8°, d = +31.5°.110

w W (2000) i q e a 1993–2012 290.6 300.3 77.5 0.359 0.886 3.15

Gamma Ursae Minorids

This meteor shower was ﬁ rst recognized by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system during 2002–2008, they detected 694 meteors from this stream. These meteors indicated a duration from January 15 to 25 (l = 294°–304°), with maximum occurring on January 20 (l = 299°) from a radiant at a = 231.8°, d = +66.8°. The geocentric velocity was 31.8 km/s, while the radiant drift was determined as +0.7° in a and −0.57° in d per day.104 The International Meteor Organization has a website containing an analysis of more than one million meteors detected by video cameras from 1993 to 2012. Stream number 13 is based on 254 meteors. The duration is given as January 17–24 ( l = 297°–304°), while maximum occurs on January 20 (l = 300°) from a radiant at a = 226.9°, d = +68.0°. The radiant drift was determined as +0.2° in a and −0.6° in d per day.108 The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 2002–2008 199.54 299.0 51.1 0.9593 0.772 4.20

Gamma Velids

Although C. Hoffmeister seems to have determined the ﬁ rst radiant for this shower on 1938 January 12 ( a = 132°, d = −47°), this stream was basically ignored until 1979, when members of the Western Australia Meteor Section (WAMS) began systematic observations of it. Gamma Velids 41

In 1978 and 1979, WAMS continuously observed the skies from December 19-January 7. The fi rst Gamma Velids were noted on January 1/2, and their numbers reached a ZHR of about 8 on January 6/7. The mean radiant position was given as a = 125°, d = −49°. Based on 27 observed meteors, it was concluded that the average meteor magnitude was 2.89, while 3.7 % of the meteors left trains. Concerning colors, it was estimated that 10 % of the meteors were orange, 10 % were yellow, 20 % were blue, and 60 % were white. More extensive observations in 1979 and 1980 revealed the Gamma Velid shower was active during January 1–17, with the mean radiant being a = 125°, d = −48°. A maximum near seven was reached on January 3.36 Based on analysis of observations of the WAMS obtained from 1982 to 1986, it can be concluded that a relatively fl at maximum of 5–9 meteors per hour occurred during January 5–8. It was also apparent that the rise to maximum was fairly rapid, while the later decline was much slower. The following parabolic orbit was computed using the average radiant of a = 125°, d = −48° and an average maximum activity date of January 7. The Southern Hemisphere radar surveys, which were conducted at Adelaide Observatory in 1961 and 1969, did not operate during the fi rst half of January.

w W (2000) i q e a 34.1 107.2 64.1 0.898 1.0 ϱ

1. Z. Sekanina, Icarus , 18 (1973), pp. 257, 260. 2. Z. Sekanina, Icarus , 27 (1976), pp. 274, 291. 3. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 244. 4. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 76 (1916 Jan.), p. 224. 5. E. Öpik, Harvard College Observatory Circular , No. 388 (1934 Apr. 29), p. 35. 6. G. W. Kronk, WGN, Journal of the International Meteor Organization , 17 (1989 Feb.), pp. 8–10. 7. G. C. Evans, Jodrell Bank Annals , 1 (1960 Nov.), pp. 281, 292–3. 8. G. C. Evans, Jodrell Bank Annals , 1 (1960 Nov.), p. 281. 9. N. A. Routledge, Nature , 183 (1959 Apr. 18), p. 1088. 10. L. G. Jacchia and F. L. Whipple, Smithsonian Contributions to Astrophysics, 4 (1961), pp. 100–1. 11. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Central Bureau Electronic Telegram, No. 1142 (2007 Nov. 17). 12. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 332. 13. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2. 14. http://www.imonet.org/showers/shw041.html 15. G. V. Schiaparelli, Report of the Annual Meeting of the British Association for the Advancement of Science , 41 (1872), p. 46. 16. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 37 (1878 Mar.), p. 318. 17. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), p. 418. 18. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 249. 19. B. A. Lindblad, Smithsonian Contribution to Astrophysics , 12 (1971), p. 21. 20. Z. Sekanina, Icarus , 18 (1973), pp. 255, 258. 21. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 318. 42 2 January Meteor Showers

22. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 252. 23. H. Corder, Memoirs of the British Astronomical Association , 7 (1899), p. 8. 24. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 205. 25. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 249. 26. A. F. Cook, Evolutionary and Physical Properties of Meteoroids . eds. Hemenway, Curtis L., Millman, Peter M., and Cook, Allan F., Washington, D.C.: NASA (1973), p. 184. 27. B. Gates, Meteor News , No. 20 (1974 Mar.), p. 3. 28. N. W. McLeod, III , Meteor News , No. 26 (1975 Jun.), p. 7; MN , No. 27 (1975 Aug.), p. 5. 29. N. McLeod, III, F. Martinez, J. West, G. Shearer, and P. Jones, Meteor News , No. 36 (1977 Jun.), p. 13. 30. B. Gates, Meteor News , No. 39 (1978 Jan.), p. 3. 31. R. Taibi, Personal Communication (2012 Feb. 1). 32. Z. Sekanina, Icarus , 27 (1976), p. 274. 33. C. S. Nilsson, Ph.D. Thesis, University of Adelaide (1962). 34. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), pp. 609–10. 35. M. Buhagiar, WAMS Bulletin , No. 160 (1980). 36. J. Wood, Personal Communication (1986 Oct. 15). 37. http://www.imonet.org/showers/shw009.html 38. G. Zezioli, Report of the Annual Meeting of the British Association for the Advancement of Science , 40 (1871), p. 98. 39. G. V. Schiaparelli, Report of the Annual Meeting of the British Association for the Advancement of Science , 41 (1872), p. 46. 40. A. S. Herschel, Memoirs of the British Astronomical Association , 11 (1903), p. 13. 41. A. Pearlmutter, Popular Astronomy , 59 (1951 Mar.), p. 159. 42. http://www.imonet.org/showers/shw008.html 43. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 266. 44. R. B. Southworth and G. S. Hawkins, Smithsonian Contributions to Astrophysics , 7 (1963), p. 269. 45. B. A. Lindblad, Smithsonian Contribution to Astrophysics , 12 (1971), p. 8. 46. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 208, 214. 47. E. J. Öpik, Harvard College Observatory Circular , No. 388 (1934), p. 37. 48. http://www.imonet.org/radiants/ 49. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 330. 50. http://www.imonet.org/showers/shw255.html 51. Z. Sekanina, Icarus , 27 (1976), pp. 275, 291. 52. R. E. McCrosky and A. Posen, Smithsonian Contribution to Astrophysics , 4 (1961), p. 39. 53. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 331. 54. G. Bream, Flower Observatory Reprint , No. 143 (1963), p. 9. 55. http://www.imonet.org/showers/shw002.html 56. A. Brucalassi, Antologia , 17 (1825 Feb.), p. 135. 57. L. F. Wartmann and E. Reynier, Correspondance mathématique et physique de ’observatoire de Bruxelles , 11 (1839), p. 351. 58. A. Bravais, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles, 8 pt. 1 (1841), pp. 44–5. 59. E. C. Herrick , American Journal of Science and Arts, 35 (1839 Jan.), p. 366. 60. A. Quetelet, “Catalogue des principales apparitions d’étoiles ﬁ lantes,” Nouveaux Mémoires de l’académie royale des sciences et belles-lettres de Bruxelles , 12 (1839), p. 26. 61. A. Quetelet and F. Duprez, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 7 pt. 1 (1840), pp. 94–5. 62. L. F. Wartmann, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 8 pt. 2 (1841), p. 226. 63. A. Colla, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles, 15 pt. 1 (1848), p. 258. Gamma Velids 43

64. E. Heis, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles, 16 pt. 1 (1849), p. 3. 65. E. J. Lowe, Report of the Annual Meeting of the British Association for the Advancement of Science , 18 (1849), pp. 4, 9. 66. S. Masterman, American Journal of Science and Arts , 2nd series, 35 (1863), pp. 149–50. 67. E. J. Lowe, R. P. Greg, and A. S. Herschel, Report of the Annual Meeting of the British Association for the Advancement of Science , 34 (1865), pp. 28–31. 68. D. Kirkwood, Proceedings of the American Philosophical Society , 13 (1873), pp. 501–2. 69. G. W. Kronk, Cometography , volume 2. United Kingdom: Cambridge University Press (2003), pp. 288–9 70. T. W. Backhouse, The Astronomical Register , 22 (1884 Jan.), pp. 16–18. 71. W. E. Besley, The Observatory , 23 (1900 Jan.), pp. 52–5. 72. P. M. Ryves, The Observatory , 32 (1909 May), p. 211. 73. W. J. Fisher, Harvard College Observatory Circular , No. 346 (1930 Jan.), pp. 1–11. 74. W. J. Fisher and M. Olmsted, Harvard College Observatory Circular , No. 347 (1930 Jan.). 75. G. S. Hawkins and M. Almond, Monthly Notices of the Royal Astronomical Society , 112 (1952), pp. 221, 225. 76. J. P. M. Prentice, Journal of the British Astronomical Association , 63 (1953 Apr.), pp. 179, 182–4. 77. G. S. Hawkins and M. Almond, Monthly Notices of the Royal Astronomical Society , 112 (1952), p. 225. 78. K. B. Hindley, Journal of the British Astronomical Association , 82 (1971), p. 63. 79. K. B. Hindley, Sky and Telescope , 43 (1972 Mar.), pp. 162–4. 80. G. E. D. Alcock and J. P. M. Prentice, Journal of the British Astronomical Association, 63 (1953 Apr.), pp. 186–7. 81. W. F. Denning and F. Wilson, Monthly Notices of the Royal Astronomical Society, 78 (1918 Jan.), pp. 198–9. 82. K. B. Hindley, Journal of the British Astronomical Association , 80 (1970), p. 479. 83. D. W. Hughes, The Observatory , 92 (1972 Apr.), pp. 41–3. 84. S. E. Hamid and M. N. Youssef, Smithsonian Contribution to Astrophysics, 7 (1963), pp. 309–11. 85. G. S. Hawkins and R. B. Southworth, Smithsonian Contribution to Astrophysics, 3 (1958), pp. 1–5. 86. S. E. Hamid and F. L. Whipple, The Astronomical Journal , 68 (1963 Oct.), p. 537. 87. I. P. Williams, C. D. Murray, and D. W. Hughes, Monthly Notices of the Royal Astronomical Society, 189 (1979), pp. 483–92. 88. P. Jenniskens, H. Betlam, M. C. de Lignie, M. Langbroek, and M. van Vliet, Astronomy & Astrophysics , 327 (1997), pp. 1242–52. 89. P. Jenniskens, The Astronomical Journal , 127 (2004 May), pp. 3018–22. 90. P. A. Wiegert and P. G. Brown, Earth, Moon, and Planets , 95 (2004 Dec.), pp. 81–8. 91. W. J. Fisher, Harvard College Observatory Circular , No. 346 (1930 Jan.), p. 11. 92. I. Hasegawa, Publications of the Astronomical Society of Japan , 31 (1979), p. 263. 93. P. B. Babadzhanov and Y. V. Obrubov, Interplanetary Matter. Edited by Z. Ceplecha and P. Pecina, Prague: Astronomical Institute of the Czechoslovak Academy of Sciences (1987), pp. 141–50. 94. B. A. McIntosh, Icarus , 86 (1990 Jul.), 299–304. 95. I. P. Williams and S. J. Collander-Brown, Monthly Notices of the Royal Astronomical Society , 294 (1998), pp. 127–38. 96. P. Jenniskens, International Astronomical Union Circular , No. 8252 (2003 Dec. 8). 97. W. Wenz, Bulletin de la Société Astronomique de France , 22 (1908), pp. 365–6. 98. F. L. Whipple, The Astronomical Journal , 59 (1954 Jul.), p. 204. 99. R. E. McCrosky and A. Posen, Smithsonian Contributions to Astrophysics , 4 (1961), p. 34. 100. P. B. Babadzhanov and E. N. Kramer, Smithsonian Contributions to Astrophysics , 11 (1967), p. 69. 44 2 January Meteor Showers

101. G. A. Harvey and E. F. Tedesco, The Astronomical Journal , 82 (1977 Jun.), p. 446. 102. Z. Sekanina, Icarus , 13 (1970), pp. 476–7. 103. M. de Lignie and K. Jobse, WGN, Journal of the International Meteor Organization , 24 (1996 Feb.–Apr.), p. 22. 104. P. Brown, D. K. Wong, R. J. Weryk, and P. Wiegert, Icarus , 207 (2010), pp. 71–2. 105. J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy, Monthly Notices of the Royal Astronomical Society , 398 (2009), pp. 353–4. 106. J. P. Younger, Personal Communication (2013 Jan.–Feb.). 107. SonotaCo, WGN, Journal of the International Meteor Organization , 37 (2009), p. 59. 108. http://www.imonet.org/showers/shw013.html 109. R. P. Greg, Proceedings of the British Meteorological Society , 2 (1865 Jan.), p. 305. 110. G. W. Ridley, Popular Astronomy , 40 (1932 Jun.–Jul.), p. 360. Chapter 3

February Meteor Showers

Alpha Antliids

D. P. Galligan and W. J. Baggaley (2002) announced the discovery of this stream when they analyzed data acquired by the Advanced Meteor Orbit Radar (AMOR) located in Christchurch, New Zealand. They found a meteor stream composed of 327 meteors, which they identiﬁ ed as “Peak 1.” Maximum activity occurred on February 2 ( l = 313.1°) from a radiant at a = 162.1°, d = −13.3°. The radiant drift was given as a = +0.68°, d = −0.16, while the geocentric velocity was given as 42.7 km/s.1 S. Molau and J. Kac (2009) presented details of the Video Meteor Network. They noted that an analysis of the 2008 video database “yielded a number of meteor shower candidates, which are unknown in the IMO shower list. The candidate with least scatter is a possible weak shower from February 2 to 7 (l = 313°–318°), based on just 66 shower members. On February 4, the average radiant lies at a = 162°, d = −14°. The mean meteor shower velocity is 45 km/s.”2 Analyzing data from the Canadian Meteor Orbit Radar (CMOR), P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 1,228 meteor orbits from this stream. They determined the duration as January 16–February 21 (l = 295°– 332°) and found that the maximum came on February 2 (l = 312°) from a radiant at a = 160.7°, d = −12.3°. The geocentric velocity was 43.2 km/s, while the daily motion of the radiant was +0.745° in a and −0.36° in d . 3 No visual counterpart to this stream has been found in any of the usual radiant lists of the last 150 years, and no trace is present in the radio meteor surveys of the 1960s.

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 45 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_3, © Springer Science+Business Media New York 2014 46 3 February Meteor Showers

The orbit labeled “AMOR” is from Galligan and Baggaley (2002). The orbit labeled “CMOR” is from Brown et al. (2010).

w W (2000) i q e a AMOR 141.9 133.1 64.3 0.143 0.920 2.4 CMOR 141.99 132.0 64.3 0.1367 0.929 1.94

Aurigids

During an analysis of “Epochs and Positions” of meteor radiants published in the Report of the Annual Meeting of the British Association for the Advancement of Science during the period of 1845–1863, R. P. Greg (1865) found 13 meteors observed during February 9–17 that indicated a radiant at a = 76°, d = +40°.4 A few years later, G. Zezioli (Bergamo, Italy) was watching for meteors on the night of 1868 February 16. He registered the paths of several meteors, which G. V. Schiaparelli said indicated a radiant at a = 74°, d = +48°. 5 W. F. Denning brought attention to an active radiant in Auriga on several occasions. Although he thought of this as a stationary radiant that was seemingly active from August into April, he speci fi cally wrote, “The shower is also a conspicuous one, and often yields brilliant fi reballs between about February 5–15.” He mentioned the observations above and added, “From Zezioli’s and a number of other meteor-paths observed in Italy in 1869–1872 I found a good radiant at 74° + 43° (22 meteors) for February 5–10.”6 Denning reiterated his enthusiasm for the Aurigids in 1903, while brie fl y discussing a bright meteor that he saw on the evening of 1903 February 18. He stated it lasted about 2 s and came from the direction of the stars Zeta and Eta Aurigae. Denning wrote, “One of the best meteoric showers visible in February has a radiant near this point, 5° S.S.W. of a Aurigae….” He considered the shower’s duration to be from February 7 to 23, and gave a radiant derived from his own observations as a = 75°, d = +41°. He said, “It often furnishes bright meteors in the evenings....”.7 In 1912, Denning further elaborated on his Aurigid observations, saying that his radiant of a = 75°, d = +41°, was derived from seven bright meteors plotted between 1876 and 1903. The meteors were described as slow and left trains.8 In a separate article written in 1912, Denning mentioned two fi reballs that had been seen by several people during the previous 15 years that calculations revealed were part of this meteor shower. The fi rst meteor was seen on 1901 February 13.95 and was as bright as Venus. The resulting radiant was determined as a = 72°, d = +41°. The second meteor was seen on 1910 February 17.76 by 12 observers. It was described as three times brighter than Venus and came from a radiant at a = 72°, d = +43°.9 This shower seems curiously absent from the radiant lists of numerous observers, including Denning, during the next few decades, except for a couple of fi reballs. Aurigids 47

Denning reported a fi reball that was seen on 1920 February 17.87 by F. Wilson (Totteridge, England) and S. B. Mattey (Plumstead, England). It was described as brighter than Jupiter. Denning said it came from the same radiant as previous fi reballs and gave the mean radiant as a = 72°, d = +43°.10 C. P. Olivier analyzed the fi reball of 1935 February 27.97. Observations were reported by 16 observers in the states of Pennsylvania and New Jersey in the United States. Even though twilight was still bright enough to prevent stars from being seen, Venus was nearby and served as a reference point. Olivier wrote, “The fi reball itself was considerably brighter than Venus; and the duration of the train was certainly 12 min or more.” The radiant was determined as a = 79.5°, d = +45.7°.11 V. Znojil conducted the fi rst visual study of this shower from 1962 to 1967. In 1962, observations were made from Mt. Klet (Czech Republic) on February 7/8 and 10/11. Two groups of observers applied different observing methods: one used no optical aid and observed with a limiting magnitude of 6.0, while the other group used 8 cm binoculars, which gave a limiting magnitude of 10.8. The naked-eye observers detected hourly rates of 1.5 ± 0.5 on the 7/8 and 1.1 ± 0.4 on the 10/11. The average meteor magnitude was noted as 2.9 on the fi rst date and 4.9 on the second. The binocular observations revealed 11 members, with the average Aurigid magnitude being 9.0. In 1967, observations were made from Brno (Czech Republic) on February 4/5, 6/7, 8/9 and 10/11. Only binoculars were used. The results were that seven Aurigids were detected and the average magnitude was 8.3. Znojil’s analysis of the Aurigid observations of 1962 and 1967 primarily discussed the apparent lack of small particles within the stream. He pointed out that the ratio of Aurigid meteors to sporadics changed markedly between visual and binocular observations, yet the change was always consistent. For instance, visual observations on 1962 February 7/8, revealed 21 Aurigids and 127 sporadics, and the February 10/11 visual observations revealed 24 Aurigids and 131 sporadics. On the other hand, binocular observations made on 2 days in 1962 revealed 11 Aurigids and 279 sporadics, while for the 4 days in 1967 they revealed 7 Aurigids and 234 sporadics. Znojil concluded that the small particles of this stream came about as a result of “fragmentation and cosmic erosion.” He added that there was a possibility that the small particles were coming from a radiant that “is slightly displaced from the normally given position....”.12 Following the publication of Znojil’s results, there was a burst of interest for a little over a decade. From 1970 February 8 to 14, B. Gates (Albuquerque, New Mexico, USA) acquired counted 11 Aurigids, which revealed hourly rates of only 0.6, while M. Hale (New York) and R. Hill (North Carolina) counted 33 Aurigids from 1972 February 5 to 17, which revealed an hourly rate of only 0.2. Gates described the meteors as being “very slow” and generally yellow. He also speci fi cally pointed out the very low activity in the early 70s.13 In contrast to these low hourly rates, the Western Australia Meteor Section obtained a ZHR of about seven during 1980 February 2–7. The date of maximum was given as February 4, while the radiant was a = 79°, d = +39°. 14 No visual observations were reported during the next few decades; however, an examination of the International Meteor Organization Video Meteor Network’s 48 3 February Meteor Showers

“Million Meteors” database reveals that the Aurigids still exist. On about February 5 ( l = 315°), a radiant at a = 74.0°, d = +47.5° was delineated by 23 meteors. On about February 7 ( l = 317°), a radiant at a = 70.6°, d = +35.5° was delineated by 24 meteors. On about February 12 ( l = 322°), a radiant at a = 78.5°, d = +46.0° was delineated by 22 meteors. Finally, on about February 17 (l = 327°), a radiant at a = 73.9°, d = +39.5° was delineated by 24 meteors.15 The Prairie Network ﬁ reball survey photographed a magnitude −9.1 meteor on 1970 February 1 ( l = 311°). The radiant was determined as a = 62.1°, d = +37.6° and the following orbit was determined.16

w W (2000) i q e a 193.4 312 3.3 0.976 0.52 2.00

Daytime Capricornids-Sagittariids

Duration : January 13–February 14 (l = 292°–325°) Maximum : February 1 (l = 312.5°) Radiant : a = 299°, d = −15° ZHR : Medium

Radiant Drift : a = UNK, d = UNK V G : 27 km/s

The complete history of this daylight stream is contained in the details accumulated during the two sessions of the Radio Meteor Project during the 1960s. Z. Sekanina conducted the surveys and was able to isolate this stream in the two sets of data. During the 1961–1965 session, 26 meteors were detected during the period of January 13–February 28. They indicated a nodal passage was February 2.7 (l = 313.3°) from an average radiant of a = 299.0°, d = −15.2°. The geocentric velocity was determined as 29.4 km/s. Sekanina showed that a good probability existed that this stream was a twin branch of his Scorpiid-Sagittariid stream of June (see the Theta Ophiuchids of June), with the D-criterion being given as 0.149. He also suggested a possible relationship to the Apollo asteroid Adonis, with the D-criterion being 0.318. 17 The 1968–1969 survey revealed 29 meteors during the period of January 15–February 14. The nodal passage came on January 29.6 (l = 309.1°), at which time the average radiant was a = 298.9°, d = −14.2°. The geocentric velocity was determined as 25.1 km/s. The resulting orbit made the identiﬁ cation with the June stream seem more plausible (D-criterion of 0.119) and the suspected identi ﬁ cation with Adonis was also strengthened (D-criterion of 0.199).18 Orbits for this stream were determined from data accumulated from each session of the Radio Meteor Project. The orbit labeled “1961–1965” is from Sekanina (1973), while the orbit labeled “1968–1969” is from Sekanina (1976). Daytime Chi Capricornids 49

w W (2000) i q e a 1961–1965 60.0 314.0 6.8 0.314 0.842 1.991 1968–1969 69.8 309.8 6.2 0.415 0.758 1.712

Daytime Chi Capricornids

Duration: January 29–February 28 (l = 308°–339°) Maximum: February 13 (l = 324.7°) Radiant: a = 315°, d = −24° ZHR: Low

Radiant Drift: a = UNK, d = UNK V G : 27 km/s

This is another daytime stream found by Z. Sekanina (1973) during the 1961–1965 session of the Radio Meteor Project. His analysis revealed 15 meteors during January 29–February 28. The nodal passage occurred on February 13.6 (l = 324.4°), at which time the radiant was at a = 314.3°, d = −23.7°. The stream’s geocentric velocity was determined to be 26.8 km/s. Sekanina suggested that this stream was associated with the Apollo asteroid 2,101 Adonis and added that it might be the twin branch of the Sigma Capricornids of July.19 Sekanina’s orbit is as follows:

w W (2000) i q e a 242.5 145.1 6.8 0.355 0.789 1.684

This stream was confi rmed in 1969 by the radio meteor system at the University of Adelaide (South Australia, Australia). G. Gartrell and W. G. Elford (1975) detected three meteors during February 10–17 from a radiant at a = 316°, d = −21°. They suggested a possible association with the periodic comet 45P/Honda-Mrkos- Pajdusakova and added that B. G. Marsden and Sekanina’s 1971 discovery of strong nongravitational forces in fl uencing this comet’s motion should not rule out “the possibility of related meteor streams with signi fi cantly different orbits....”.20 The orbit determined by Gartrell and Elford is as follows:

w W (2000) i q e a 246 145 4.5 0.36 0.82 2.083 50 3 February Meteor Showers

The following are the orbits of the suggested associations: Adonis, 45P, and the Sigma Capricornids. For 45P, the orbit from the 1969 apparition is given.

w W (2000) i q e a Adonis 43.21 349.88 1.33 0.4423 0.7640 1.8742 45P 184.14 233.83 13.17 0.5587 0.8143 3.0083 Sigma CAP 290.5 107.4 2.1 0.431 0.758 1.782

Alpha Centaurids

Duration: January 28 to February 21 (l = 307°–332°) Maximum: February 8 (l = 319.2°) Radiant: a = 215°, d = −59° ZHR: 6

Radiant Drift: a = UNK°, d = UNK° V G : UNK km/s

This stream was ﬁ rst detected by radar at Adelaide Observatory (South Australia, Australia) in 1969. The analysis by G. Gartrell and W. G. Elford (1975) revealed only two meteors during February 10–17 from a radiant at a = 223°, d = −61°, with the date of nodal passage being determined as February 15 (l = 326°).21 M. Buhagiar (Western Australia, Australia) published his “Southern Hemisphere Meteor Stream List” in 1980. This contained 488 radiants compiled from his personal observations spanning 1969–1980. Buhagiar listed two radiants, which he called the “Beta Centaurids,” which reached maximum on February 7. Radiant 290 was active during February 6–8 from a = 206°, d = −57°, while radiant 299 was active during February 5–9 from a = 214°, d = −64°. Meteor rates ranged from 3 to 10 per hour.22 In 1979, members of the Western Australia Meteor Section (WAMS) managed to observe the “Alpha Centaurids” during February 2–18. At maximum on February 7, the radiant was at a = 216°, d = −59° when meteors fell at a rate of 2 per hour. In 1980, the same group observed members of this stream during February 2–24. They noted that maximum came on February 8 from a = 209°, d = −58° and meteors fell at a rate of 11–14 per hour—amounting to a ZHR of about 28.14 J. Wood (1989) published the results of visual observations made during 1988 February. He said this radiant was active during February 8–13. The peak occurred on the night of February 8/9, when the ZHR reached about 8. They noted that 27.8 % of the meteors left a train. 23 Wood (2013) said observations continued to be reported to him into the 1990s, but rates never exceeded 3 per hour.24 A search through dozens of visual lists of meteor radiants published since the 1860 s revealed that a couple of previous observations do exist. J. Warren (Cape Town, South Africa) observed meteors from a radiant at a = 220°, d = −60° on 1921 February 9 and 11.25 C. Hoffmeister was also observing from South Africa, when he saw several meteors on 1938 February 1 (l = 311.5°) from a radiant at a = 210°, d = −57°. 26 Delta Leonids: Antihelion 51

The orbit labeled “1969” is from Gartrell and Elford (1975). The orbit labeled “Visual” was calculated using the visual radiants given above.

w W (2000) i q e a 1969 344 147 105.0 0.97 0.61 2.50 Alpha 344.6 140.2 107.9 0.968 1.0 ϱ

February Eta Draconids

This meteor shower was discovered during an analysis of data collected by the Cameras for Allsky Meteor Surveillance (CAMS) network, a NASA-sponsored multi-station video camera network. P. Jenniskens and P. S. Gural identiﬁ ed 5 meteor orbits that were detected on 2011 February 4 (l = 315.1°). The radiant was determined as a = 239.92°, d = +62.49° and the geocentric velocity was given as 35.58 km/s. The magnitudes of the meteors were all between +1.9 and +2.6.27 The International Meteor Organization’s video meteor network has created a website titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the February Eta Draconids are present within this sample, as 70 meteors came from a radiant at a = 238.2°, d = +61.0° on February 4 (l = 314°), 70 meteors came from a radiant at a = 241.3°, d = +61.0° on February 5 ( l = 315°), 59 meteors came from a radiant at a = 239.6°, d = +60.5° on February 6 ( l = 316°), and 61 meteors came from a radiant at a = 240.3°, d = +61.0° on February 7 ( l = 317°). 15 The orbit labeled “2011” is from Jenniskens and Gural (2012).

w W (2000) i q e a 2011 194.09 315.07 55.20 0.971 1.004 −250

Delta Leonids: Antihelion

Duration: February 9–March 12 (l = 319°–352°) Maximum: February 24 (l = 335°) Radiant: a = 168°, d = +16° ZHR: 2

Radiant Drift: a = +0.93°, d = −0.38° V G : 22 km/s

Credit for the discovery of this meteor shower goes to B. A. Lindblad (Lund Observatory, Sweden). He took 2401 photographic meteor orbits from the Harvard 52 3 February Meteor Showers

Meteor Project of 1952–1954 and analyzed the data using a computer. The result was 24 meteors from a stream he called the “Delta Leonids.” The period of visibility was given as February 5–March 19, and the average radiant position was a = 159°, d = +19°. The geocentric velocity was given as 23 km/s.28 Con ﬁ rmation came quickly when Z. Sekanina (1973) published the results of the ﬁ rst session of the Radio Meteor Project, which was a program that used radio equipment at Havana, Illinois (USA). This session ran from 1961 to 1965. Eight meteors were detected from the Delta Leonids. These indicated the duration as February 9–March 12. The date of nodal passage was given as February 19.9 ( l = 330.7°), while the average radiant position was at a = 154.3°, d = +18.3°. The geocentric velocity was determined as 20.6 km/s.29 The second session of the Radio Meteor Project operated from 1968 to 1969. Sekanina (1976) detected a stream that he called the “Delta Leonids,” but the orbit’s argument of perihelion and ascending node were about 180° off. In addition, the duration was given as January 13–February 24, the date of the nodal passage was February 2.3 (l = 313.8°), and the radiant position was a = 135.2°, d = +7.5°. 30 When compared to the Delta Leonid radiant ephemeris, this stream lies about 15° to the south and could very well be a southern branch. No trace of this southern branch appears in visual and photographic records, which implies that it may be a possible telescopic shower. Research was done to look through the radiant lists of the nineteenth and twentieth centuries for previous observations of this shower. The earliest trace seems to be a meteor six times the brightness of Venus which was observed by 16 observers on 1910 February 28.8. The radiant was determined as a = 155°, d = +16°. 31 A year later, during 1911 February 19–March 1, W. F. Denning (Bristol, England) plotted seven meteors from a radiant at a = 155°, d = +14°. The meteors were described as slow, with trains.32 Additional visual observations belonging to this meteor shower were obtained in 1924 and 1930. In the former year, J. P. M. Prentice (England) plotted several meteors from a = 155°, d = +13° during February 25–28.33 In 1930, two independent observations were made from opposite sides of the Atlantic. On February 19, C. Hoffmeister (Germany) detected a radiant at a = 149°, d = +18°,34 while observations by B. S. Whitney (USA) during February 20–21 revealed a radiant at a = 154°, d = +21°. 35 Observations by members of the Western Australia Meteor Section (WAMS) have supplied some of the most valuable information on the Delta Leonids. J. Wood, director of the WAMS, analyzed observations from the late 1970s and early 1980s and concluded that maximum occurs on February 26, from a = 158°, d = +17°. He gives the duration as February 1–March 13.36 In 1979, Delta Leonids were observed during February 22–March 3. A maximum ZHR of about three came on February 25. The radiant position was then given as a = 159°, d = +19°. The average magnitude of seven observed meteors was 2.86. In 1980, activity was observed during February 15–March 9. A maximum ZHR of about three came on February 22, at which time the radiant was at a = 159°, d = +18°.14 Delta Leonids: Antihelion 53

Compared to other currently active meteor streams, the Delta Leonids appear to possess a fairly short history. K. Fox (1985) investigated the past and future orbits of 53 meteor streams. He found that the Delta Leonid orbit does not come in contact with Earth’s orbit 1,000 years in the past or future.37 Thus, this stream is only a temporary feature as far as Earth is concerned. D. I. Olsson-Steel and B. A. Lindblad (1987) suggested that minor planet 1987 SY “might be the parent of the delta Leonid meteor shower….” They pointed out that the orbit was closest to Earth on February 18 and that the theoretical radiant and velocity were very close to that of the Delta Leonids.38 The Delta Leonids are also known for producing ﬁ reballs. A. K. Terentjeva (1989) analyzed the details of 554 ﬁ reballs that had been photographed by networks in the United States and Canada from 1963 to 1984. Stream number 12 has a duration of February 6–March 23, while the average radiant was at a = 159°, d = +7°. 39 During 2009 February, 17 members of the International Meteor Organization’s Video Meteor Network captured 3,611 total meteors using 28 video cameras. S. Molau and J. Kac (2009) analyzed the data. They said the automated meteor shower search software failed to detect the Delta Leonids; however, they did note, “A closer inspection of the radiants at individual solar longitudes reveals that the d -Leonids seem to be at least partly active.” An included table revealed the earliest activity came on February 23 ( l = 334°), when 18 meteors emanated from an average radiant at a = 161.6°, d = +13.0°. The highest activity came on February 24 ( l = 335°) and February 27 (l = 338°), when 25 meteors came from radiants at a = 162.0°, d = +13.5° and a = 166.0°, d = +12.0°. Activity was last detected on March 2 (l = 341°), when 18 meteors emanated from an average radiant at a = 167.3°, d = +14.5°. 40 The Video Meteor Network also created a website called “Million Meteors in the IMO Video Meteor Database.” They analyzed the paths of over a million meteors detected by the video camera network from 1993 to 2012. A total of 910 Delta Leonids were detected during the period of February 11–March 4 (l = 332– 343°). Maximum activity came on February 28 ( l = 339°) from a radiant at a = 171.6°, d = +9.0°. The radiant’s daily motion was determined as +1.1° in a and −0.3° in d .41 After taking the radio meteors and the photographic meteors and determined the radiant’s daily motion as +0.93° in a and −0.38° in d . The orbit labeled “1952–1954” is from Lindblad (1971). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1963–1984” is from Terentjeva (1989).

w W (2000) i q e a 1952–1954 259.0 338.8 6.2 0.643 0.747 2.618 1961–1965 266.4 331.4 4.8 0.612 0.687 1.954 1963–1984 262.8 342.4 3.2 0.663 0.613 1.737 54 3 February Meteor Showers

1. D. P. Galligan and W. J. Baggaley, Dust in the Solar System and Other Planetary Systems . Edited by S.F. Green, I.P. Williams, J.A.M. McDonnell and N. McBride. Oxford: Pergamon, (2002), pp. 54, 58 2. S. Molau and J. Kac, WGN, Journal of the International Meteor Organization, 37 (2009 Apr.), pp. 75–6. 3. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2. 4. R. P. Greg, Proceedings of the British Meteorological Society , 2 (1865), p. 305. 5. G. V. Schiaparelli, Memoirs of the Royal Astronomical Society , 40 (1871), p. 98. 6. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 61 (1901 Apr.), p. 420. 7. W. F. Denning, The Observatory , 26 (1903 Mar.), pp. 137–8. 8. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912 May), p. 633. 9. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912 Mar.), p. 426. 10. W. F. Denning, The Observatory , 43 (1920 Apr.), pp. 166–7. 11. C. P. Olivier, Monthly Weather Review , 63 (1935 May), pp. 158–9. 12. V. Znojil, Bulletin of the Astronomical Institutes of Czechoslovakia , 19 (1968), pp. 301–6. 13. B. Gates, Meteor News , No. 39 (1978 Jan.), p. 3. 14. J. Wood, Personal Communication (1986 Oct. 15). 15. http://www.imonet.org/radiants/ 16. R. E. McCrosky, C.-Y. Shao, and A. Posen, Center for Astrophysics Preprint Series, No. 665 (1976), p. 12. 17. Z. Sekanina, Icarus , 18 (1973), pp. 255, 258. 18. Z. Sekanina, Icarus , 27 (1976), pp. 274, 291. 19. Z. Sekanina, Icarus , 18 (1973), pp. 258, 264, 279. 20. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), pp. 596, 613. 21. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), p. 619. 22. M. Buhagiar, WAMS Bulletin , No. 160 (1981). 23. J. Wood, WGN, Journal of the International Meteor Organization , 17 (1989), p. 79. 24. J. Wood, Personal Communication (2013 Mar. 22). 25. J. Warren, Memoirs of the British Astronomical Association , 24 (1924), p. 81. 26. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 246. 27. P. Jenniskens and P. S. Gural, WGN, Journal of the International Meteor Organization, 39 (2011 Aug.), pp. 93–7. 28. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 20–1. 29. Z. Sekanina, Icarus , 18 (1973), p. 258. 30. Z. Sekanina, Icarus , 27 (1976), p. 275. 31. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912), p. 428. 32. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912), p. 634. 33. W. F. Denning, The Observatory , 47 (1924 Mar.), p. 98. 34. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 227. 35. C. P. Olivier, Flower Observatory Reprint , No. 8 (1931), p. 14. 36. J. Wood, Personal Communication, (1985 Oct. 24). 37. K. Fox, Asteroids, Comets, Meteors II . eds. Rickman, H., and Lagerkvist, C.-I., Uppsala: University of Uppsala (1986), pp. 522–4. 38. D. I. Olsson-Steel and B. A. Lindblad, International Astronomical Union Circular , No. 4472 (1987 Oct. 19) 39. A. K. Terentjeva, WGN, Journal of the International Meteor Organization, 17 (1989 Dec.), p. 242. 40. S. Molau and J. Kac, WGN, Journal of the International Meteor Organization, 37 (2009 Apr.), p. 75. 41. http://www.imonet.org/showers/shw031.html Chapter 4

March Meteor Showers

Daytime Kappa Aquariids

This daytime meteor shower was ﬁ rst detected during 1961 by radio-echo equipment at the University of Adelaide (South Australia, Australia). C. S. Nilsson (1964) analyzed the data and said the equipment operated during March 11–16. During March 12–16, three meteors were detected from a radiant at a = 339.5°, d = −7.6°, which he designated “61.3.2”. The geocentric velocity was determined as 29.8 km/s. Nilsson suggested the stream was closely related to the Northern Iota Aquariid stream of July and August.1 The University of Adelaide radio meteor system was used again during 1968– 1969. G. Gartrell and W. G. Elford (1975) analyzed the data and noted seven meteors were detected during 1969 March 16–22, which they designated stream “3.01”. The average position of the radiant was a = 338°, d = −8°. The authors concluded that, although there was some discrepancy between the ascending node of the March stream and that of the Northern Iota Aquariids, “The correspon- dence of the longitudes of perihelion is excellent.” They added that since the nighttime stream was apparently broad, a link with the March stream “may still be acceptable”. 2 This stream was detected during 2002–2008 by the Canadian Meteor Orbit Radar system. 3 P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) detected 1,457 meteors during the period of March 6 (l = 346°) to March 10 ( l = 350°). The peak of activity occurred on March 10 (l = 350°) from a radiant at a = 332°, d = −8.4°. The geocentric velocity was determined as 31.4 km/s. The authors suggested the stream might be associated with minor planet 2007 KG7 .

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 55 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_4, © Springer Science+Business Media New York 2014 56 4 March Meteor Showers

Orbits for these three surveys are given below. The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1969” is from Gartrell and Elford (1975). The orbit labeled “2002–2008” is from Brown et al. (2010). The orbit labeled “2007

KG7 ” is the minor planet that might be associated.

w W (2000) i q e a 1961 59.7 354.4 2.5 0.298 0.86 2.13 1969 42 0 1.8 0.18 0.89 1.70 2002–2008 50.12 350.0 4.6 0.2339 0.872 1.83

2007 KG7 318.317 66.276 4.746 0.2365 0.8673 1.78

March Eta Draconids

Observations of the March Eta Draconids seem con fi ned to the twentieth century. In C. Hoffmeister’s book, Meteorströme , fi ve radiants are listed which apparently belong to this stream. The fi rst observation was made on 1910 April 2 ( l = 12°), when 20 meteors were detected from a 2°-diameter radiant at a = 247°, d = +63°. Another observation came on 1911 April 1 (l = 11°), when 12 meteors came from a 2°-diameter radiant at a = 246°, d = +69°. The three additional radiants were detected on 1919 April 5 ( l = 15.4°) at a = 244°, d = +61°, 1931 April 7 ( l = 16.8°) at a = 253°, d = +54°, and 1936 March 23 (l = 1.6°) at a = 251°, d = +59°.4 Two members of the American Meteor Society (AMS) have also detected activity from this stream. On 1940 April 4.3, D. Faulkner (Stetson University, Florida, USA) coordinated two teams of students to observe the Eta Aquariids. The groups were located at Daytona Beach and Altoona, and every meteor was plotted. Faulkner’s evaluation of the data revealed that both stations had detected meteors from a radiant at a = 257°, d = +56°. 5 On 1951 March 31.6, P. Burt (Memphis, Tennessee, USA) plotted nine meteors from a radiant of a = 247°, d = +63°.6 Members of the Yaroslavl Society of Amateur Astronomers and the Yaroslavl division of the Astronomical and Geodetic Society of the USSR conducted a visual survey of meteor showers during 1969 March. T. L. Korovkina, V. V. Martynenko, and V. V. Frolov (1971) analyzed the results. Observers were split into two groups, with one observing at Krasnye Tkachi (Russia) during March 24–30, and the other observing at Rybinsk (Russia) during March 6–16 and 25–29. The limiting magnitude of the sky during these observations was between 5 and 5.5. The observers at the former village had set their objective as searching for radiants of minor meteor showers, and they were the successful observers of the March Eta Draconids. E. A. Malakhaev observed the fi rst possible radiant on March 26.99, when nine plotted meteors indicated a 1.0°-diameter radiant at a = 231.0°, d = +56.2°. On a scale of 1–5, the accuracy of this radiant was given as three. A similar value was also March Eta Draconids 57 assigned to a radiant detected by Malakhaev, N. V. Smirnov, and T. A. Kopycheva during March 27.98. Based on eight meteors, the position was given as a = 237.0°, d = +60.0°, while the radiant diameter was given as 2.0°. Two excellent radiants were determined during the following two nights: on March 28.91, Smirnov, Kopycheva and V. K. Karpov plotted 16 meteors (one stationary) from a 2.0°-diameter radiant at a = 241.0°, d = +61.5°, while, on March 29.88, Smirnov, Kopycheva and L. M. Afanaseva plotted 17 meteors (one stationary) from a 1.5°-diameter radiant at a = 245.5°, d = +63.5°.7 The 1969 survey was repeated on a smaller scale during 1973, with members of the Yaroslavl Amateur Astronomers Society making their observations during March 24–30 in Krasnye Tkachi. Smirnov and T. L. Korovkina (1975) analyzed the data. Overall, the 1973 observations revealed less activity from the March Eta Draconids than was detected in 1969, but two radiants were determined. N. A. Tsarev and Smirnov determined the fi rst radiant during March 25–29. Four meteors came from an area 1.0° across at a = 237.0°, d = +61.0°. Tsarev and B. M. Belyakov determined the second radiant. They plotted six meteors during March 24–28, which came from a 1.5°-diameter radiant at a = 255.0°, d = +64.5°.8 The International Meteor Organization’s video meteor network has created a website titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the March Eta Draconids are present within this sample. A radiant at a = 235.3°, d = +63.5° was delineated by 35 meteors detected on March 26 (l = 6°). A radiant at a = 250.0°, d = +63.0° was delineated by 35 meteors detected on March 27 (l = 7°). 9 A search through the various records of photographic meteor orbits has revealed no possible members of this stream; however, among Z. Sekanina’s 39,145 radio meteor orbits acquired during the Radio Meteor Project, 15 probable members were found which seem to indicate two distinct streams. The fi rst stream is based on seven meteors. The indicated duration is March 22–April 9, while the average radiant is a = 247.0°, d = +61.9°. The second stream orbit is based on eight meteors, with an indicated duration of March 24–April 8, and an average radiant of a = 250.1°, d = +54°. Sekanina had not noticed either of these streams. Here are orbits for each of these branches of the March Eta Draconids; the orbit labeled “N” represents the northern branch, while the orbit labeled “S” represents the southern branch.

w W (2000) i q e a N 196.5 9.6 38.2 0.984 0.592 2.41 S 202.6 13.8 48.0 0.967 0.736 3.66

The orbit bears a striking resemblance to the orbit of comet C/1953 T1 (Abell). J. D. Drummond (1981) computed the theoretical meteor radiants for 178 58 4 March Meteor Showers

long-period comets. Comet Abell was listed as producing a radiant at a = 254°, d = +57° on March 23 ( l = 2.3°). The closest approach between the orbits of the comet and Earth was given as 0.01 AU.10

w W (2000) i q e a C/1953 T1 194.39 3.03 53.23 0.9701 1.0007 −1412

x Herculids

S. Molau and J. Kac (2009) discovered this meteor shower during an analysis of more than 4,100 meteors recorded by the International Meteor Organization’s Video Meteor Network during 2009 March. They found 161 meteors that indicated a duration of March 10–16 ( l = 349°–355°) and a maximum on March 12/13 ( l = 352°), at which time the radiant was at a = 254°, d = +48°.11 The International Meteor Organization has a website containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. Stream number 41 is called the “x Herculids” and is based on 283 meteors. The duration is given as March 10–17 (l = 349–356°), while maximum occurs on March 13 ( l = 352°) from a radiant at a = 255.5°, d = +48.1°. The radiant drift was determined as −0.1° in a and +0.3° in d per day.12 The following two orbits were calculated using the original date and radiant supplied by Molau and Kac (2009). The ﬁ rst is a parabolic orbit, while the second is an elliptical orbit based on an assumed semimajor axis of 2.5 AU. The indicated geocentric velocities are 28 km/s and 22 km/s, respectively.

w W (2000) i q e a 185.9 352.1 64.4 0.991 1.0 ∞ 184.3 352.1 57.9 0.993 0.603 2.5

Kappa Leonids

M. J. Currie (1995) announced the discovery of this meteor shower, while observing the Virginid meteor shower with a 13 cm refractor. He was observing on 1995 March 6/7 (l = 346°),and of the 41 meteors that were observed, 15 came from a region about 4° northeast of the star Regulus. He input the meteor paths into a Kappa Leonids 59

Table 4.1 Photographic meteors from McCrosky and Posen (1961) Date l (°) a (°) d (°) 6766 1953 March 5 344 160 +15 6776 1953 March 6 345 159 +13 10208 1954 March 5 344 156 +16 10270 1954 March 6 345 163 +17

software program called RADIANT, which revealed the meteors emanated from a = 154.7°, d = +14.7°. The software also indicated the radiant was 2.2° across. Currie checked his observations from the previous night and noted that he saw 2–3 possible meteors from this radiant during 5.75 h.13 In looking through previous publications back to 1982, Currie located a paper written by A. K. Terentjeva (1994), which mentioned the Kappa Leonids as occurring on March 5 and March 6, providing two radiants: a = 158°, d = +16° and a = 161°, d = +15°. 14 Terentjeva fi rst mentioned these two radiants in a paper published during 1968.15 Each was based on only two photographic meteor orbits acquired during the Harvard Meteor Project and fi rst published by R. E. McCrosky and A. Posen. 16 The details of these four photographic meteors are displayed in Table 4.1 . Terentjeva simply created a radiant based on the two March fi ve meteors and another radiant for the March 6 meteors. This certainly does not indicate a double radiant and, at best, might indicate the daily motion of the radiant. However, based on the fact that only four low precision meteor orbits are available, it would be best to not draw any conclusions other than suggesting an average radiant of a = 160°, d = +15°. The International Meteor Organization’s Video Meteor Network created a website titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the Kappa Leonids are present within this sample. Under l = 345°, a radiant at a = 162.3°, d = +12.5° was delineated by 67 meteors. Under l = 346°, a radiant at a = 154.6°, d = +11.5° was delineated by 53 meteors.9 Further possible radiants exist before l = 345°, but they are located between this radiant and the Delta Leonids. These could be associated with either radiant or they might be antihelion meteors. After checking lists of radiants going back to the mid-nineteenth century only two close matches to the Kappa Leonid radiant were found. AMS radiant 4,030 was detected by J. W. Simpson (Webster Groves, Missouri, USA) on 1935 March 7.7 ( l = 346.5). He plotted nine meteors from a radiant at a = 154.5°, d = +11.5°. 17 AMS radiant 4,618 was detected by D. Conger (Elizabeth, West Virginia, USA) on 1963 March 2.8 ( l = 341.8). He plotted seven meteors from a radiant at a = 150.5°, d = +12.5°. 18 60 4 March Meteor Showers

The orbits of the four photographic meteors from the Harvard Meteor Project are given below. The meteor labeled “6766” was photographed on 1953 March 5.

w W (2000) i q e a 6766 252 345 3 0.74 0.59 1.80 6776 251 346 2 0.71 0.74 2.74 10208 247 345 3 0.76 0.66 2.23 10270 255 346 6 0.67 0.80 3.31

Delta Mensids

This shower was discovered during 1969 by the multi-station radar equipment at the University of Adelaide (South Australia, Australia). G. Gartrell (1972) noted two particularly interesting streams, which he designated “3.04” and “3.05”. Stream “3.04” was deﬁ ned by 11 meteors that were detected from a radiant at a = 51°, d = −81°, while stream “3.05” was de ﬁ ned by ten meteors that were detected from a radiant at a = 50°, d = −78°. Gartrell said that although stream “3.04” was “a good example of a ‘toroidal’ stream and yet there is no doubt that it is related to 3.05 which certainly is not.” Toroidal meteors move in high inclination, low eccentricity orbits. Gartrell said these two streams have orbits that are very close to comet C/1804 E1 (Pons), so close, in fact, that he considered an association as “unmistakable.”19 During further analysis of the University of Adelaide data, Gartrell and W. G. Elford (1975) said the equipment had been in operation during the period of March 16–22 and that the average date of activity of “3.04” was March 18, while the average date of activity of “3.05” was March 19. They indicated that these streams provided a very important key to meteor stream formation, when they were compared to comet C/1804 E1. As can be seen below, the orbits of all of these objects are very similar except in their values of the semimajor axes. The authors said the orbital similarities “give further evidence that the low eccentricity orbits could be the result of evolution rather than direct formation from low eccentricity comets.” They added that if the orbit of comet 1804 is parabolic as indicated, then “only 170 years have been available for 3.04 to contract from a > 10 a.u. to the present value of 2.13 a.u.”.20 No apparent records appear to exist concerning past observations of this shower; however, southern hemisphere observers have been making occasional observations of this stream since its announcement. According to J. Wood (National Association of Planetary Observers, Australia), observations made during the 1970s and 1980s indicate this shower has a duration spanning March 14–21. At maximum on March 18, 1–2 meteors per hour can be detected from an average radiant of a = 55°, d = −80°. Gamma Normids 61

The stream orbits determined by Gartrell (1972) are given below.

w W (2000) i q e a 3.04 347 179 55.3 0.98 0.53 2.13 3.05 346 179 58.3 0.98 0.87 10.00

The orbit of comet C/1804 E1 (Pons) is as follows:

w W (2000) i q e a C/1804 E1 331.946 179.534 56.452 1.0712 1.0 ϱ

Gamma Normids

Duration: March 7 to March 23 (l = 347°–1°) Maximum: March 15 (l = 355°) Radiant: a = 243°, d = −49° ZHR: 6

Radiant Drift: a = UNK°, d = UNK° V G : UNK km/s

R. A. McIntosh (Auckland, New Zealand) discovered this meteor shower on 1929 March 10.1. He plotted seven meteors which indicated a radiant of a = 241.5°, d = −43°. 21 Con fi rmation came in 1932, when M. Geddes (New Plymouth, New Zealand) plotted six meteors on March 7.1, from a = 242.7°, d = −54.7°. Geddes plotted another fi ve meteors on March 12.0—the radiant then being a = 240°, d = −52°. 22 McIntosh summarized these radiants in his 1935 paper “An Index to Southern Meteor Showers.” The duration was given as March 7–12, and the weighted average radiant was a = 241°, d = −53°. 23 It was referred to as the “Scorpiids.” This stream was virtually ignored until 1953, when radar equipment used by A. A. Weiss (University of Adelaide, South Australia, Australia) detected activity on March 15–16. Although the radiant position was estimated as a = 250°, d = −50°, Weiss said it could not “be fi xed precisely because of low activity and also because of the marked de fi ciency of large meteors in this stream.”24 He elaborated by noting that the number of radar echoes with a duration of one-half second or longer were practically no greater during the shower than on non-shower days. Weiss also indicated that the radiant’s culmination after sunrise would make visual observations dif fi cult. Curiously, C. D. Ellyett and C. S. L. Keay (1956) made an attempt to con fi rm this shower during 1956 March. The equipment was set at the same sensitivity as Weiss’ during March 8–14, and it was set at a higher sensitivity during March 15–23, but neither session revealed the shower. The authors concluded the shower “is variable in activity from year to year.”25 62 4 March Meteor Showers

The next observation of the Gamma Normids came during 1969 March 16–22, while G. Gartrell and W. G. Elford (1975) operated the radio meteor system at Adelaide. Two associations were noted which possessed radiants close to that of this stream. The ﬁ rst was based on three meteor orbits and possessed a radiant position of a = 250°, d = −43° on a mean date of March 20. The second association was considered less reliable since it was based on only two meteors. Its radiant was a = 253°, d = −41° on a mean date of March 19.26 M. Buhagiar (Perth, Western Australia) published a list in 1981, which gave details of meteor showers observed by him during 1969–1980. Radiant number 339 (called the “Beta Arids”) was given a duration of March 15–21. Maximum was said to have occurred on March 17, from a = 245°, d = −50°. The maximum hourly rate was given as 4.27 Observers of the Western Australia Meteor Section (WAMS) have contributed greatly to observations of this shower in recent years. During 1979, the Gamma Normids were observed over the period of March 16–18. Maximum came on March 17, when a ZHR of about eight was detected from a = 248°, d = −49°. In 1980, observations were made during March 14–15. At maximum on March 15, the ZHR was about nine and the radiant was a = 242°, d = −50°.28 The WAMS made very extensive observations during 1983. The earliest Gamma Normid activity came on the night of March 10/11, when the ZHR was about 1.5 ± 0.3. After another low ZHR of 1.6 ± 1.0 on March 11/12, a sharp rise to a ZHR of 9.6 ± 2.3 came on March 13/14, followed by a rate of 4.6 ± 0.6 on March 14/15. Thereafter, rates were 2.2 ± 0.8 on March 15/16, 0.5 ± 0.1 on March 17/18, and 0.7 ± 1.1 when last seen on March 18/19. Based on 63 meteors, the average magnitude was determined as 2.68, while 9.5 % had trains. For the meteors of magnitude 2 or brighter, 64 % were white, 24 % were yellow, 8 % were orange, and 4 % were blue.29 Another session by the WAMS in 1986 covered the period of March 7–22 and resulted in 273 observed Gamma Normids. Computed ZHRs were 2.57 on March 12/13, 3.49 on March 14/15, 1.96 on March 15/16, and 1.35 on March 20/21. Nearly 20 % of the meteors left a train.30 During 2005, the Liga IberoAmericana De Astronomía (LIADA) conducted a campaign to study meteor activity from this radiant. Visual observations covered the period of March 8–17 (l = 347–356°) and meteors from this stream were noted each night. The highest number of meteors seen per hour was 5 on the night of March 10/11 (l = 349.7°), with the indicated ZHR being 14 ± 6.31 The only orbits ever determined for this stream came from Gartrell and Elford (1975) using radio-echo data obtained during 1969. Although the respective radiants are very similar, the differences in semimajor axes cause some signiﬁ cant differences in the orbital elements. Orbit 3.15 is based on three meteors, while 3.46 is based on two. As mentioned earlier, the latter orbit is considered uncertain.

w W (2000) i q e a 3.15 97 181 137.4 0.66 0.43 1.18 3.46 49 181 145.4 0.85 0.72 3.13 Gamma Normids 63

1. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226, 240–1. 2. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), p. 606. 3. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2, 76. 4. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 199, 201, 206, 224, 251. 5. C. P. Olivier, Flower Observatory Reprint , No. 63 (1943), p. 43. 6. C. P. Olivier, Flower Observatory Reprint , No. 85 (1952), p. 17. 7. T. L. Korovkina, V. V. Martynenko, and V. V. Frolov, Solar System Research , 5 (1971), p. 100. 8. N. V. Smirnov and T. L. Korovkina, Solar System Research , 8 (1975), p. 98. 9 . http://www.imonet.org/radiants/ 10. J. D. Drummond, Icarus , 47 (1981), p. 505. 11. S. Molau and J. Kac, WGN, Journal of the International Meteor Organization, 37 (2009 Jun.), pp. 92. 12. http://www.imonet.org/showers/shw041.html 13. M. J. Currie, WGN, Journal of the International Meteor Organization, 23 (1995 Aug.), pp. 151–4. 14. A. K. Terentjeva, Proceedings of the International Meteor Conference, Puimichel, France, 23–26 September 1993. Edited by P. Roggemans, International Meteor Organization (1994), p. 100. 15. A. K. Terentjeva, Physics and Dynamics of Meteors. Symposium no. 33 held at Tatranska Lomnica, Czechoslovakia, 4–9 September 1967. International Astronomical Union. Symposium no. 33, Edited by L. Kresák and P. M. Millman. Dordrecht: D. Reidel (1968), pp. 410, 414. 16. R. E. McCrosky and A. Posen, Smithsonian Contribution to Astrophysics , 4 (1961), p. 40. 17. C. P. Olivier, Flower and Cook Observatory Reprint , No. 119 (1960). 18. C. P. Olivier, Flower and Cook Observatory Reprint , No. 149 (1964). 19. G. Gartell, Proceedings of the Astronomical Society of Australia , 2 (1972 Mar.), pp. 89–90. 20. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), p. 596, 613–14. 21. C. P. Olivier, Flower Observatory Reprint , No. 5, p. 21. 22. C. P. Olivier, Flow er Observatory Reprint , No. 15, pp. 43–4. 23. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), p. 714. 24. A. A. Weiss, AJP , 8 (1955), pp. 157–8. 25. C. D. Ellyett and C. S. L. Keay, AJP , 9 (1956), p. 479. 26. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), pp. 596, 619. 27. M. Buhagiar, WAMS Bulletin , No. 160 (1981). 28. J. Wood, Personal Communication (1986 Oct. 15). 29. J. Wood, WGN, Journal of the International Meteor Organization , 12 (1984 Feb.), p. 8. 30. J. Wood, WGN, Journal of the International Meteor Organization , 15 (1987 Aug.), pp. 131–2. 31. J. M. Trigo-Rodríguez, P. Balderas, R. Moyano, Viviana Bianchi, and I. Javora, WGN, Journal of the International Meteor Organization , 33 (2005), pp. 87–9. Chapter 5

April Meteor Showers

April Rho Cygnids

This is a newly discovered meteor shower that was ﬁ rst recognized by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar (CMOR) system during 2002–2008, they detected 1,006 meteors from this stream. These meteors indicated a duration of April 24-May 3 (l = 34°–43°), with maximum occurring on April 27 (l = 37°) from a radiant at a = 324.5°, d = +45.9°. The geocentric velocity was 41.8 km/s, while the radiant drift was determined as +0.61° in a and +0.36° in d per day.1 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. Stream number 64 is called the “Nu Cygnids” and is based on 1,251 meteors. The duration is given as April 11-May 8 (l = 21°–47°), while maximum occurs on April 29 (l = 38°) from a radiant at a = 321.0°, d = +45.5°. The radiant drift was determined as +1.1° in a and +0.4° in d per day.2 The only nineteenth century visual radiant identiﬁ ed was by W. F. Denning during 1887 April 18–20, when he plotted four meteors from a radiant at a = 327°, d = +48°. Denning described the meteors as slow and bright.3 This may have only been a chance alignment, as no other radiant could be found among well over 10,000 visual radiant observations published during the late nineteenth and into the twentieth century,

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 65 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_5, © Springer Science+Business Media New York 2014 66 5 April Meteor Showers

The orbit labeled “2002–2008” is from Brown et al. (2010).

ω Ω (2000) i q e a 2002–2008 125.55 37.0 69.9 0.8099 0.875 6.51

Tau Draconids

This stream was fi rst recognized in a 1973 study involving 2401 photographic meteor orbits obtained during the Harvard Meteor Project of 1952–1954. A. F. Cook, B. A. Lindblad, B. G. Marsden, R. E. McCrosky, and A. Posen identi fi ed four meteor orbits, which formed the “Delta Draconids.” Exhibiting a duration covering March 28-April 17, the average radiant position was given as a = 281°, d = +68°.4 Shortly after the above photographic data was published, Z. Sekanina (1973) published the details of the 1961–1965 session of the Radio Meteor Project, which used radio equipment run by the University of Illinois in Havana, Illinois (USA). Among the 72 minor meteor streams observed was the “Tau Draconids.” This stream was given a duration of March 24-April 12. The nodal passage came on April 1.7 (l = 11.5°), at which time the radiant position was a = 291.6°, d = +71.3°. The geocentric velocity was given as 19.1 km/s.5 Sekanina (1976) provided the analysis of the 1968–1969 session of the Radio Meteor Project. The Tau Draconids were again detected—this time with a duration extending from March 12-April 12. The date of the nodal passage was given as March 27.0 (l = 5.8°), while the average radiant was a = 286.4°, d = +69.1°. The geocentric velocity was given as 20.2 km/s.6 The fi rst visual observations of this shower were actually occurring while Sekanina’s second session of the Radio Meteor Project was in progress. On 1969 March 25.92, V. K. Leichenok, N. S. Malikov, L. M. Afanas’eva, and T. A. Kopycheva plotted more than ten meteors from a radiant of a = 280.0°, d = +73.0°. The radiant diameter was determined as 5.0°.7 As a follow-up, the Russian observers strove to con fi rm the many radiants they had found by conducting another extensive visual survey in 1973. On March 26, S. V. Safonov plotted three meteors from a 1.5°-diameter radiant at a = 272°, d = +72°. During March 27–29, N. V. Smirnov plotted six meteors from a 2.0°-diameter radiant at a = 285°, d = +71°. 8 The orbit labeled “1952–1953” is that from Cook et al. (1973). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976).

ω Ω (2000) i q e a 1952–1954 171.1 14.4 37.5 0.996 0.724 2.77 1961–1965 166.3 12.2 30.9 0.985 0.533 2.11 1968–1969 169.0 6.5 33.0 0.988 0.542 2.16 Lyrids 67

Lyrids

Duration : April 14 to April 25 (l = 26°–35°) Maximum : April 22 (l = 32.3°) Radiant : a = 272°, d = +33° ZHR : 18

Radiant Drift : a = +0.62°, d = −0.33° V G : 47 km/s

Interest in this meteor shower was very slow to develop due to the relative infancy of meteor astronomy. A very strong display was reported in numerous newspapers during April and May of 1803. One of the most quoted sources, the 1803 April 23 edition of the Virginia Gazette and General Advertiser , stated, “This electrical phenomenon was observed on Wednesday morning last [April 20], at Richmond and in its vicinity, in a manner that alarmed many, and astonished every person who beheld it.” It added, “From one until three, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets. Several of those shooting meteors were accompanied with a train of fi re that illuminated the sky for a considerable distance.” Residents in the Richmond area were somewhat lucky when a small fi re broke out, prompting the ringing of the fi re bell, which woke up everyone within earshot and provided them a chance to see the meteors. 9 The 1803 May 31 issue of the New Hampshire Gazette included a letter from an unnamed correspondent from Portsmouth, New Hampshire, who stated that he counted 167 meteors “in about 10 or 15 min” and then stopped counting because “they fell so fast.” He added that he watched from about 1 to 3 in the morning. 10 Whether this was actually an outburst of the Lyrids can only be conjectured. E. C. Herrick wrote in 1839, “The grand display of April 20, 1839 … appeared chiefl y after midnight, but where the radiant then was, no man can tell us.” 11 In a discussion about the falling stars that were seen on November 12/13 of 1799, 1831, and 1833, F. J. D. Arago (1835) noted “how important it would be … to inquire whether other trains of asteroids meet the ecliptic in the different points of that in which the earth is placed towards the 13th of November. This investigation would require to be made, for example, from 20th to 24th of April; for in 1803 … there was seen in Virginia and the Massachusetts, from one o’clock till three in the morning, falling stars in such numbers and in all directions, that it might have been supposed to be a shower of rockets.”12 No other April observations were quoted by Arago to support or deny the existence of annual activity. Although some writers have considered Arago to be the fi rst to recognize annual activity from the Lyrids, this really does not qualify as a discovery. J. F. Benzenberg (1838) followed up on Arago’s suggestion and looked for meteors on the nights of April 20–26. He noted hourly rates of only 2–3 on each night. He wrote, “there is nothing left but to assume that M. Arago was wrong….” 13 Despite Benzenberg’s negative result, Herrick came to a different conclusion in 1839. In a nearly six-page article published in the American Journal of Science and Arts, Herrick included four accounts of the meteor outburst of 1803 April 20 and told of his observations in 1839. Concerning the latter, he said that Francis Bradley 68 5 April Meteor Showers and himself observed on April 19 and saw 58 meteors, of which the majority, “if traced back, would meet in a spot somewhere between a Lyrae and g Draconis….” Herrick estimated that radiant as a = 273°, d = +45°. He added, “This meteoric shower appears to be the legitimate successor of those which occurred” on 1095 April 10 and 1122 April 12. 14 Herrick compiled a “History of the Star-Showers of Former Times” in an 1841 volume of the American Journal of Science and Arts and noted another previous appearance of this meteor shower on 1096 April 10. 15 It should be noted that L. A. J. Quetelet presented a paper at the 1839 June 8 session of the Royal Academy of Brussels, which also noted the April 1095 meteor shower, but incorrectly gave the day as the 25th. 16 Herrick and others made a few observations during the 1840s. On the night of 1841 April 19/20, before clouds moved in, a total of 15 meteors were seen during 1.5 h. Herrick wrote, “No very defi nite radiant could be determined, but it appeared that the radiant region was then east of the meridian, and about 70° or 80° in altitude.” 17 [The Author notes that, although Lyra was east of the meridian at midnight, its altitude was less than 40°, but then Herrick was making a rough estimate… meaning this could still be an observation of the Lyrids.] Herrick requested E. Loomis to look for meteors on the night of 1842 April 19/20. Loomis was in Hudson, Ohio (USA) and gathered with eight students to watch, but was met with cloudy skies. They observed again on the morning of April 21, which was clear. Watches were made that generally covered the period of 1:00 a.m. to morning twilight. About 20 meteors were seen, but Loomis wrote, “This number certainly cannot be considered very extraordinary.”18 Herrick, G. C. Murray, and E. R. Smith watched for meteors on the morning of 1849 April 20. Between 1:00 and 2:00 a.m., they counted 54 different meteors. Herrick wrote, “There was nothing remarkable in these as to brilliancy, nor was there any decided point of radiation.”19 An outburst seemed to have been seen in India on the night of 1851 April 20. In the Report of the Twenty-First Meeting of the British Association for the Advancement of Science (1852), several stories are given that were originally published in the Bombay Times. The fi rst came from a correspondent from Mazagaon, near Mumbai, and was published on April 24. Around 10:00 p.m., he noted “a display of meteors, following each other in succession, appeared from a point about 15° above the north-eastern horizon. In the space of little more than half an hour about 20 were observed; they darted across the sky in all directions.” The second came from Kolhapur and was published on May 6. The person wrote, “on looking out about half-past ten … the entire sky to the north was seen in a perfect blaze with meteors shooting from east to west. The phaenomenon lasted about 5 min, when all was again still.” A third report was from a correspondent from Kanpur and was published on May 16. This person wrote, “This evening from 8 to 10 p.m. constant meteors fl ying across, chie fl y from N. towards S., often three or four at a time. The largest I did not see. I had my face towards N., facing a white building, when suddenly the whole was a bright as you see in a vivid fl ash of sheet lightning.”20 The Lyrids were virtually ignored during the next decade, but came alive on the morning of 1863 April 21 for observers in England and Scotland. The Report of the Thirty-Third Meeting of the British Association for the Advancement of Science Lyrids 69

(1864) said observations were made from Newe (Aberdeenshire, Scotland), Weston-super-Mare (England), and Hawkhurst (England). Basically, at 3 a.m. (local time), meteors were falling at a rate of 40 per hour. On the evening of the 22nd, no meteors were seen.21 A. Walker (Castle New Strathdon) observed a meteor shower from 11:00 p.m. to midnight (local time) on 1863 April 20. He said, “Falling stars very plentiful this night.” He noted that they were directed from “Corona.”22 R. P. Greg (1865) published a catalog of recent meteor showers. He noted a “Marked star-shower” during the morning of 1863 April 21, noting reports by observers in England and Scotland, including A. S. Herschel (Hawkhurst) and W. H. Wood (Weston-super-Mare).23 The investigations of H. A. Newton (1863) into ancient meteor showers revealed additional displays in 687 B.C. March 16, 15 B.C. March 25, and A.D. 582 March 31, which he thought could represent the Lyrids. The fi rst two dates are from Chinese historical texts, while the last was taken from a European monastic history. Newton noted that if these dates were adjusted up to 1850, they would be April 19.9, April 19.6, and April 18.1, respectively, agreeing very well with the Lyrid activity dates. 24 J. B. Biot had published the Chinese observations during 1862. Modern translations have revealed that Biot made slight errors in the dates of these ancient observations. These errors were caught as our understanding of the Chinese calendar improved. D. W. Pankenier, Z. Xu, and Y. Jiang (2008) presented new translations of comet and meteor shower observations from the Chinese texts. The actual date of the earliest observation is 687 B.C. March 23, with the description reading, “at night the fi xed stars did not appear; the night was bright. During the night, stars fell like rain, together with the rain.” The next date is now dated 15 B.C. March 27, with the description reading, “after midnight, stars 1–2 zhang long and deep scarlet in color fell like rain, but did not reach the earth. This went on till cockcrow.” These new dates now move Newton’s adjusted dates to April 27 for the 687 B.C. observation and April 22 for the 15 B.C. observation.25 The European observation was published by Gregory of Tours and was translated by M. Chasles, with the date actually given as A.D. 582 March 29. The text stated, “At Soissons, we see the sky on fi re. A rain of blood falls on Paris.”26 Another possible observation was found on A.D. 581 March 20, when the Koreans reported, “stars fell like rain.” 27 Adjusting the dates in the same fashion established by Newton makes the dates April 16 of A.D. 582 and April 7 of A.D. 581. This indicates that the Korean observation might be too early to be a Lyrid. Possibly inspired by the small outburst of 1863, observations were reported by several observers in 1864 and 1865. Herschel indicated the shower was back to normal in the fi rst year, observing 23 meteors on the night of April 19/20 and determining the radiant as a = 277.5°, d = +35.5°. He said 11 of the meteors were between magnitude 1 and 3, with another nearly as bright as Jupiter. 28 The Report of the Thirty-Fifth Meeting of the British Association for the Advancement of Science revealed several British observers made observations during 1865.29 During 1866, the annual Perseid shower had been linked to periodic comet 109P/Swift-Tuttle and the Leonids were linked to the newly discovered periodic 70 5 April Meteor Showers comet 55P/Tempel-Tuttle. As 1867 began, astronomers were still busy seeking further evidence linking meteor showers to comets. E. Weiss (1867) calculated the probable close encounters between Earth and the orbits of several comets. He found that comet C/1861 G1 (Thatcher) came to within 0.002 AU of Earth’s orbit on April 20. As Weiss searched through various publications for evidence of this shower’s presence, he came across several references to observed showers around April 20.30 An independent calculation by J. G. Galle also led to the suggestion that comet Thatcher and the Lyrids were related; however, he went a step further than Weiss. Galle took the orbital period and major axis determined by T. R. Oppolzer for comet Thatcher, as well as the radiant position for the Lyrids, and calculated an orbit for the meteor stream that was extremely close to that accepted for the comet. 31 Few observations were made during the remainder of the 1860s and throughout the 1870s, with several publications documenting observing campaigns that were prepared in some years, only to be clouded out on the crucial nights. H. Corder (Writtle, Essex, England) had some success during 1876–1879, when he observed 50 meteors during the period of April 18–21 that emanated from a radiant at a = 275°, d = +36°.32 Corder next saw the Lyrids on the night of 1882 April 20, when he observed 26 meteors that emanated from a radiant at a = 268°, d = +37°, which he noted was “about 7° west of its usual place.”33 W. F. Denning (Bristol, England) was inspired by Corder’s observations and began looking for this meteor shower. The moon was full near the night of maximum during 1883, but better conditions were present in 1884, when he saw 17 Lyrids in 1 h on the night of April 19. Denning said this indicated a total hourly rate of 22. 34 Denning was met with perfect nights during 1885 April 18–20. He saw 30 total meteors during those nights, but discovered something that no one else had noted before: the position of the radiant moved eastward from one night to the next. Denning’s measurements revealed a radiant of a = 260°, d = +33.5° on the 18th, a = 267.5°, d = +33° on the 19th, and a = 274°, d = +33.5° on the 20th. This was the fi rst time radiant motion had been noted for any meteor shower, other than the Perseids.35 From the 1890s to the beginning of the 1920s, the Lyrids were fairly consistently observed, with reports indicating that hourly rates varied only a little from year to year, but then came a surprise. H. N. Russell, of Princeton University (New Jersey, USA), and his wife, Lucy, were visiting Nauplia, Greece, when at 10:00 p.m. on the night of 1922 April 21, they saw a strong maximum of the Lyrids. Professor Russell reported seeing 63 meteors “within about 50 min, with a sudden drop shortly after the hour mentioned.”36 The Lyrids were also seen in England on the same night, but the outburst had already subsided. A. G. Cook and J. P. M. Prentice (Stowmarket, Suffolk, England) plotted several meteors, with the radiant being given as a = 271°, d = +33° by Cook and a = 270°, d = +33° by Prentice. Prentice said he saw 71 meteors in about 5.5 h. Denning said Cook, Prentice, and also E. H. Collinson (Ipswich, Suffolk, England) reported numerous brilliant meteors, some equaling Jupiter and Venus in brightness. Denning added that maximum occurred on April 21.95 UT ( l = 31°).37 Cook’s observations spanned April 17–21, during which time her Lyrids 71

Table 5.1 Lyrid radiant ephemeris Date RA (°) Dec (°) Apr. 10 259 +34 Apr. 12 262 +34 Apr. 14 264 +33 Apr. 16 266 +33 Apr. 18 269 +33 Apr. 20 271 +33 Apr. 22 274 +33 Apr. 24 276 +33 Apr. 26 278 +33 Apr. 28 281 +34 Apr. 30 284 +34

meteor plots clearly indicated a moving radiant. She gave the radiant as a = 266°, d = +32° on the 17th, a = 268°, d = +33° on the 19th, a = 270°, d = +33° on the 20th, and a = 271°, d = +33° on the 21st. Prentice contributed to the plots on the last two dates, while Collinson contributed on the last date.38 Denning (1923) published a radiant ephemeris for the Lyrids (see Table 5.1 ). He said he ﬁ rst suspected the radiant moved in 1885. Denning said he had personally seen Lyrids as early as April 14 and as late as April 26. He wrote, “ Observations of the Lyrids before April 15 and after April 25 will be valuable, but the display is a brief one, and two or three nights from the maximum (April 21) the meteors are very rare, and it is essential that special efforts should be made to procure multiple observations at two stations of early or late Lyrids. Single records of paths cannot always indicate the radiant with certainty.”39 After a few more years of apparently normal activity, the Lyrids brought another surprise in 1945 and 1946. K. Komaki (Kanaya, Shizuoka, Japan) was watching for meteors on the night of 1945 April 21/22. From 3:00 to 4:07 a.m., he observed 112 meteors, most of which were Lyrids.40 Astronomers at Skalnaté Pleso Observatory (Slovakia) made visual observations of this meteor shower during 1946. All observers reported that rates began to noticeably climb after April 21.90. From April 21.92 to 21.94, A. Mrkos saw 32 Lyrids, while L. Pajdusakova saw 17. During April 21.94–21.97, four astronomers saw 12–25 Lyrids, with Mrkos reporting the higher number; however, these rates were made with the moon in the sky, so higher activity is possible. Shower rates went back to normal after April 21.97. The peak occurred at l = 31.3° and the population index was determined as r = 2.9.41 Another outburst came on 1982 April 22. Observers in the states of Florida and Colorado in the United States saw a burst of activity that amounted to 3–5 Lyrids per minute. During the hour centered on the peak, the average number of meteors was reported as 75, while for the hour preceding and following this hour, the hourly rates were less than 20.42 The Budrio (Italy) meteor radar operated 24 h per day during April 17–25. During the morning hours of April 22, “an exceptionally high 72 5 April Meteor Showers number of echoes was recorded, with a peak of 232 echoes” between 06:00 and 07:00 UT. The highest number of echoes came between 06:35 and 06:40 UT, with a peak of ten echoes per minute coming at 06:38 UT when l = 31.369°.43 The Springhill Meteor Observatory (Ottawa, Canada) also detected the Lyrid outburst. It detected a peak of 33 echoes at 6:49 UT when l = 31.380°. V. Porubcan and B. A. McIntosh noted that the peak occurred at almost the same solar longitude at Springhill as the visual observations in the United States.44

Lyrids 50 45 40 35 30 Z H 25 R 20 15 10 5 0 3 13 23 33 43 53 63 Solar Longitude

This represents a decade of observations of the Lyrid meteor shower. The observations were made by members of the International Meteor Organization during the 2000s and 2010s. The solar longitude basically represents 60 days, illustrating the activity build up starting several days prior to a maximum that rapidly escalates and declines in a matter of hours

Several observers have attempted to estimate the orbital period of this meteor stream from the visual observations above. Herrick (1841) concluded from his historical study of Lyrid activity that, “The cycle of the April shower may be about 27 years.”45 D. Kirkwood (1870) examined the outbursts spanning 687 B.C. to A.D. 1803 and determined a period of 27.0652 years. He predicted the next outburst would occur in 1884, but it did not. 46 Based on the activity observed in 1803 and 1850, Denning (1897) concluded that the Lyrids possessed an orbital period of 47 years,47 but his prediction of enhanced activity in 1897 was met by rates not exceeding 6 per hour. At a later date, Denning (1914) looked at Lyrid activity from 687 B.C. to A.D. 1901 and determined the period was about 16 years. He predicted the next outburst would occur in “1915 or 1916,” but no enhanced rates were observed.48 V. A. Malzev (1929) was able to get accurate representations to the 1803, 1863, and 1922 displays using a period of 29.70 years, but this failed to predict the outbursts of 1934 and 1946.49 V. Guth (1947) calculated a least-squares solution through seven outbursts observed between 1803 and 1946, as well as fi ve observations (assumed outbursts) Lyrids 73 between 687 B.C. and A.D. 1122. The period was determined as 11.965 years, which he noted was close to the orbital period of Jupiter. But Guth also noted that Malzev’s period, which was close to that of Saturn, was the next best period to fi tting the outburst dates. He suggested the displays were “dependent on the positions of Jupiter and Saturn.” Guth added, “If we plot on a diagramm [sic] the positions of both planets in the year corresponding to rich displays, we fi nd in the majority of events that the planets were in conjunction with the stream.”50 In a paper examining the 1969 outburst of the Leonids and the 1982 outburst of the Lyrids, Porubcan and J. Stohl (1992) came up with a new idea to explain the latter shower. Noting that the outburst occurred over 120 years after the parent comet passed perihelion, they suggested “a secondary, relatively large body loosed from the parent comet Thatcher at an earlier time, perhaps together with smaller particles that dispersed more quickly along the orbit due to their higher ejection velocities.” They suggested the large chunk separated 36 revolutions earlier or about 15,000 years ago. They continued, “The chunk could disintegrate later on, producing a dense cloud of non-ejected particles of various sizes, moving in similar orbits for longer period, since not in fl uenced by the dispension of velocities occurring at an ejection process.”51 Porubcan, Stohl, and J. Svoren (1992) took another look at the 1982 Lyrid outburst and, in particular, the Springhill meteor data. They concluded that the time taken to pass through the enhanced Lyrid activity indicated the “dense cloud” of particles had a radius of about 90,000 km. They concluded that the secondary nucleus separation from the primary nucleus happened sometime between 16 and 136 revolutions ago, with 71 revolutions the most likely, and that the breakup of the secondary nucleus probably happened “about 2 years before the time of the observed shower on the pre-perihelion arc immediately preceding the 1982 Lyrid strong burst.”52 More direct methods of determining the orbital period of the Lyrids was by photographic and radar techniques. A collection of photographic orbits published by F. L. Whipple (1952), revealed two “reliable” Lyrid meteors with periods differing by 300 years!53 B. A. Lindblad (1971) published a Lyrid stream orbit based on fi ve meteors photographed during 1952 and 1953, which had an average period of 131 years.54 Z. Sekanina (1970) published a Lyrid stream orbit based on meteors detected during the 1961–1965 session of the Radio Meteor Project, which had an average period of 9.58 years. 55 P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 1,197 meteor orbits in the data acquired by the Canadian Meteor Orbit Radar (CMOR) system during 2002–2008 and determined the Lyrid period as about 36 years.56 The Lyrids are known to exhibit a sharp peak of maximum activity—a feature generally exhibited by young meteor streams or streams not prone to serious planetary perturbations. Since the inclination of the comet’s orbit is 79.8° and since evidence exists showing activity as long ago as 687 BC, then the latter scenario seems most appropriate. Typically, the time of maximum occurs around solar longitude 31.6°, with other well-documented visual observations falling within the range of 31.4°–31.7°. The earlier mentioned study of photographic orbits by 74 5 April Meteor Showers

Lindblad gave a value of 31.6°, while the radar studies by Sekanina and CMOR gave 32.0°. All of these tend to indicate a much more pronounced peak of maximum activity than is generally present for other meteor streams. K. B. Hindley (1969) pointed out that the close agreement of the maximums of both visual and photographic meteors “indicates that there is no evidence which could be interpreted as the result of the action of dispersive forces of the Poynting- Robertson type.”57 As support for this statement, Hindley added that occasional observations extending back to 687 B.C. indicate there has been little or no motion in this stream’s orbital nodes for at least 2,600 years! K. Fox (1986) took an orbit for the Lyrids that was quite close to the photographic orbit (period = 148 years) and integrated it backward and forward for 1,000 years. He indicated that the orbit experienced an almost negligible change. For 1,000 years ago, the peak would have occurred on April 16 (l = 31.0°) from a radiant at a = 271.1°, d = +34.5°. For 1,000 years in the future, the peak would have occurred on April 21 (l = 31.7°) from a radiant at a = 272.3°, d = +34.9°.58 Lindblad and Porubcan (1992) looked at the historical activity of this meteor shower and noted that the normal maximum occurs on April 21/22 (l = 31.6); however, the outbursts have occurred 0.25 days earlier (l = 31.24–31.38). They commented, “It is evident that there exists a fi lamentary structure in the Lyrid stream consisting mainly of small particles.” They continued, “Since the Lyrid outbursts do not occur every year, there exists a longitudinal structure in the fi lament. The persistence of such structures over long time periods is dif fi cult to explain.” The conclusions were, “The fi lament could be due to small particles which were ejected from the parent comet at a different time than the main Lyrid release” or there is “the operation of some unknown mass dependent dispersive mechanism….” They ruled out the Poynting-Robertson effect, because it only “operates in the orbital plane of the stream….”59 Porubcan and L. Kornos (2008) published a paper examining the orbit and structure of the Lyrid stream. They began with 17 photographic orbits and determined the radiant’s daily motion as +0.802° in a and −0.155° in d . Upon restricting the comparison parameters, they noticed two distinct fi laments—one with a period of about 40 years and the other with a period of about 600 years. The authors noted that fi lament 1 “coincides quite well with the outburst peak preceding the annual maximum and is more in fl uenced by perturbations.” Filament 2 “is closer to the annual maximum” and is “rather stable,” as its evolution is “almost identical with the evolution of the parent comet Thatcher.”60 The average brightness of Lyrid meteors has been found to drop at maximum. Porubcan and Stohl (1983) analyze visual observations obtained by observers at Skalnate Pleso Observatory in 1945, 1946, 1947, and 1952. They noted that the abnormally strong peak in 1946, which amounted to a ZHR of 40, was characterized by an increase in the number of fainter stream members.61 A. Dubietis and R. Arlt (2000) analyzed visual observations that had been reported for the Lyrids during 1988–2000. They said the average ZHR was 18, with the average peak falling on l = 32.32°. The population index is normally r = 2.0–2.1 at maximum, although “several pro fi les” revealed a jump to 2.3–2.5 at maximum.62 Delta Pavonids 75

The orbit labeled “Photo” was calculated using six precise meteor orbits from photographic surveys conducted in the United States and Czechoslovakia. The orbit labeled “Radar” is from Sekanina (1970). The orbit labeled “CMOR” is from Brown et al. (2010). The orbits labeled “950” and “2950” are from Fox (1986) and represent the Lyrid orbit integrated 1,000 years into the past and future. The orbit labeled “C/1861 G1” is the orbit of comet Thatcher.

ω Ω (2000) i q e a Photo 214.2 32.7 79.6 0.920 0.966 26.80 Radar 215.3 32.7 76.9 0.922 0.796 4.51 CMOR 215.71 32.0 80.0 0.9149 0.916 10.85 950 215.2 31.8 78.9 0.97 27.68 2950 213.4 32.4 78.8 0.97 27.97 C/1861 G1 213.5 31.2 79.8 0.92 0.98 55.68

Delta Pavonids

The discovery of the Delta Pavonids should be attributed to M. Buhagiar (Perth, West Australia, Australia). During the period of 1969–1980, he succeeded in observing this shower in six different years. The duration of activity was determined as April 3–8, while the date of maximum was established as April 6 ( l = 17°). The average radiant position was a = 303°, d = −63°. The hourly rate was said to be variable, but did reach a high of 10.63 Buhagiar suggested an association with comet Grigg-Mellish. Comet C/1907 G1 (Grigg-Mellish) was independently discovered by J. Grigg (Thames, New Zealand) on 1907 April 8 and by J. E. Mellish (Madison, Wisconsin, USA) on April 14. It was only followed until May 14. Such a short observational arc rarely allows anything but the calculation of a parabolic orbit; however, A. Berberich and E. Weiss independently noted a similarity between the orbit of this comet and the orbit of comet C/1742 C1. Weiss (1909) assumed a period of 164 years to link these two comets, and some comet catalogs published this as the accepted orbit. A general solution was calculated by B. G. Marsden in 1975, and he concluded that the eccentricity could not be smaller than 0.99.64 The Western Australia Meteor Section (WAMS) observed the meteor shower during 1980. According to J. Wood (director of the section), meteors from this shower were detected during April 4–8. Maximum came on April 5, when the radiant was at a = 305°, d = −65°. The peak ZHR was about 2.65 The Delta Pavonids were best observed during 1986. Wood said an observing campaign was conducted spanning March 12-April 12 that involved 35 Australian meteor observers. At the end of the campaign, 884 Delta Pavonid meteors had 76 5 April Meteor Showers been recorded during 369 total man-hours. The only night meteors from this shower were not detected was March 12/13. For the most part, the majority of the observations were made during April 5–12. The ZHR was 2.4 on the night of April 5/6, increased to 4.7 by the night of April 7/8, and dropped to 0.4 by the night of April 11/12. The population index was determined as 2.61 and 12.9 % of the meteors left trains. 66 P. Jenniskens (1994) examined the available observations of this meteor shower. Based on 323 meteors seen by six observers, he determined that maximum came at l = 9° from a radiant at a = 308°, d = −63°. Starting from a parabolic orbit and assuming a shift in the node, Jenniskens gave the radiant drift as +1.6° in a and −0.2° in d per day.67 The orbit labeled “WAMS” was calculated using the position determined by WAMS on 1980 April 5. The orbit labeled “C/1907 G1” is that of comet Grigg-Mellish.

w Ω (2000) i q e a WAMS 348.0 195.0 121.0 0.990 1.0 C/1907 G1 328.76 190.42 110.06 0.924 1.0

Daytime April Piscids

Duration : April 8 to April 29 (l = 18°–39°) Maximum : April 20 (l = 30.3°) Radiant : a = 7°, d = +7° ZHR : Low

Radiant Drift : a = +0.94°, d = +0.42° V G : 29 km/s

This daylight meteor shower was discovered by C. S. Nilsson (1964) while analyzing 2,200 radio meteor orbits detected during a survey conducted at the University of Adelaide (South Australia, Australia) during 1961. Only three meteors were noted during the interval of April 13–29. The indicated date of the nodal passage was April 18/19, at which time the radiant was located at a = 6.5°, d = +4.3°. The geocentric velocity was given as 25.1 km/s. Nilsson said his stream actually did not qualify as a group, due to the excessive “scatter in the values obtained for the right ascension;” however, he noted a close agreement between the orbits of this stream and a stream detected in August, which has been identiﬁ ed here as the Northern Iota Aquariids.68 Con ﬁ rmation of this daylight meteor shower was by B. L. Kashcheyev and V. N. Lebedinets (1967) using three receiving stations operating at a wavelength of 8 m at the Kharkov Polytechnical Institute (Ukraine). During the period of 1960 April 15–25, they detected 34 meteors from a radiant of a = 7°, d = +3°, with the nodal passage occurring on April 19 ( l = 30°). The geocentric velocity was given as 31 km/s.69 Daytime April Piscids 77

It is surprising that this stream was not recognized by Z. Sekanina in either of the two sessions of the Radio Meteor Project. In an attempt to discover why, the Author searched through the 39,145 radio meteors orbits that were determined. The radio equipment at Havana, Illinois, operated during April of 1962–1965 and in 1969. Thirteen probable members of the Daytime April Piscids are present in the sample. These meteors indicate a duration of from April 8 to 26. The date of the nodal passage is determined as April 19/20 (l = 29.7°), at which time the radiant is at a = 7.4°, d = +7.2°. What is most interesting is the yearly distribution: Five meteors in 1962, 1 in 1963, 4 in 1964, 2 in 1965, and only 1 in 1969. When Sekanina’s data is compared with that obtained in the Russian and Australian surveys discussed earlier, it appears that the Russian data was based on an uncharacteristic return of this stream, with 34 meteors being detected. In fact, the 1968–1969 session of the Radio Meteor Project involved the most sensitive equipment ever used, and April was well covered. The fact that only one meteor was detected in 1969 may indicate that this daylight stream is periodic. The Canadian Meteor Orbit Radar (CMOR) detected 397 meteor orbits from this stream during 2002–2006. An analysis by P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2008) revealed a maximum on April 14 (l = 24.5°) from a radiant of a = 3.8°, d = +5.5°. The duration extended from April 6–23 (l = 16°–33°) and the geocentric velocity was determined as 28.9 km/s. The daily motion was determined as a = +0.90°, d = +0.37°. 70 A second analysis of CMOR data was published by Brown, Wong, Weryk, and P. A. Wiegert (2010). This revealed 2,608 meteor orbits from this stream. Maximum occurred on April 16 (l = 26°) from a radiant of a = 4.9°, d = +5.5°. The duration extended from April 6 to April 28 (l = 16°–38°) and the geocentric velocity was determined as 29.2 km/s. The daily motion was determined as a = +0.94°, d = +0.42°. This second analysis also suggested this stream might be associated to minor planet 2005 NZ6, as well as the Iota Aquariids.71 The orbit labeled “1960” if from Kashcheyev and Lebedinets (1967) and is based on 34 meteors. The orbit labeled “1961” is from Nilsson (1964) and is based on three meteors. The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 397 meteors. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 2608 orbits. The orbit labeled “1961–1969” is an average of 13 meteor orbits found in the data of the Radio Meteor Project.

w Ω (2000) i q e a 1960 45 30 0.5 0.22 0.82 1.32 1961 48.6 29.0 5.8 0.282 0.76 1.18 2002–2006 50.2 24.5 5.0 0.256 0.833 1.5 2002–2008 49.49 26.0 4.5 0.2493 0.837 1.53 1961–1969 49.1 30.4 4.7 0.263 0.809 1.38 78 5 April Meteor Showers

Pi Puppids

Duration: April 18 to April 25 (l = 28–35°) Maximum: April 23 (l = 33.5°) Radiant: a = 112°, d = −43° ZHR: Variable

Radiant Drift: a = UNK°, d = UNK° V G : 15 km/s

Periodic comet 26P/Grigg-Skjellerup fi rst caught the attention of meteor astronomers in 1948, when two independent predictions were published indicating this comet could produce a meteor shower. C. Hoffmeister (1948) published brief details in a table, indicating a meteor shower would occur on May 17 from a radiant at a = 113°, d = +68°. 72 S. E. Hamid (1948) published a short note that examined theoretical radiants from very short period comets, of which comet 2P/Encke and 26P/Grigg-Skjellerup were the only candidates. For the latter, he noted the possible existence of two nighttime showers (January 21 from a = 107°, d = +9° and February 9 from a = 131°, d = +26°) and two daytime showers (May 31 from a = 83.5°, d = +37° and June 21 from a = 105°, d = +15°). 73 Hamid added that the nighttime showers were apparently independently observed by E. J. Öpik and the American Meteor Society, while the daytime showers had both been detected at Jodrell Bank Experimental Station. We now know that these predictions were not accurate, but they had inspired others to look into the possibility that 26P/Grigg-Skjellerup could produce a meteor shower. J. G. Porter (1952) provided a table of “Cometary Meteor Radiants”, which indicated that comet Grigg-Skjellerup could produce a meteor shower on April 26 from a radiant at a = 109°, d = −37°. 74 G. Sitarski (1964) examined the motion of comet 26P after its approach to Jupiter in 1964. He noted that the ascending node will be 212.7° and that Earth reaches this longitude on April 23. Sitarski wrote, “If a meteor stream is associated with Comet Grigg-Skjellerup, it ought to be observed as a meteor shower.” He predicted possible meteor showers from this comet on 1967 April 23.8 from a radiant at a = 109.3°, d = −44.7°, 1972 April 23.0 from a radiant at a = 109.4°, d = −44.7°, and 1977 April 23.3 from a radiant at a = 109.6°, d = −44.3°. The geocentric velocity was expected to be 15 km/s.75 H. B. Ridley (1971) brought attention to the possible meteor shower from this comet when he noticed that Earth would make a close approach to the comet’s orbit on 1972 April 23.02. The separation between the orbits was calculated as only 0.004 AU, while the encounter was to occur only 50 days after the passage of the comet. Ridley predicted the radiant as a = 107.5°, d = −45°. 76 No observations were apparently made during Sitarski’s 1967 date, but the chances of a meteor shower were expected to be much better in 1972, when Earth would pass 0.0044 AU from the comet’s orbit, just 51 days after the comet crossed this point. Observations made during the predicted appearance of this meteor shower revealed a very poor visual display. During the period of April 16–23, 17 observers in the United States obtained average hourly rates of only 1.9, with a maximum of about 4 per hour being observed by B. Edwards (Jacksonville, Florida, USA) during a 3 h interval on April 18/19.77 Observers in Western Australia (Australia) were met with even weaker activity, as 7 observers compiled 70 h of Pi Puppids 79 searching during April 21–24. The only Pi Puppids they detected were three possible shower members during an 8 h interval on the night of April 22/23. 78 On the other hand, W. J. Baggaley (1973) made a very positive Southern Hemisphere observation using radio equipment at the University of Canterbury (New Zealand). He detected an “increase in the rate of radio-meteor echoes over the normal sporadic activity on the 4 days 1972 April 21, 22, 23 and 24....” He added that the observed activity fl ux was consistent with a radiant at a = 107.5°, d = −45°, though the rates were considered too low for an accurate radiant determination.79 Comet Grigg-Skjellerup was next expected at perihelion in 1977. Sitarski’s prediction indicated Earth would pass 0.0123 AU from the comet’s orbit just 12 days after the comet passed this point.80 Observers in the United States were not successful in observing activity, but M. Buhagiar, J. Wood, A. Saare, and G. Blencowe (Perth, Western Australia) individually observed maximum rates of 18–24 meteors per hour during a 3 h interval centered on April 23.5. Numerous meteors were plotted, which revealed a radiant of a = 112°, d = −43°, and the ZHR was calculated as 36–40. The overall duration of the activity was given as April 22–24. The meteors were typically bright (some around magnitude −3 and −4) and slow.65, 81 The Western Australia meteor observers decided to look for meteors from the Pi Puppids during 1979, at which time the comet would have been nearing its aphelion. The main reason was to check if meteors from the comet had spread completely around its orbit. Weak activity was noted during April 21–24, with a maximum ZHR of about 4 coming on April 23. The average radiant was given as a = 112°, d = −43°. 65 The comet’s next perihelion passage came on 1982 May 14. J. D. Drummond (1982) predicted another return of the Pi Puppids would occur on 1982 April 23.23, from a radiant at a = 105°, d = −45°. 82 A very strong return of the Pi Puppids was observed on the night of April 23/24. A. G. Beltran (Cochabamba, Bolivia) was the fi rst to report an observation, seeing 58 meteors during a period of 1 h 35 min. He described the meteors as being predominantly yellow. A strong return was also noted in Western Australia. Individuals reported 25–42 meteors per hour, with the ZHR reaching 22.8 on April 23.48. By April 23.56, the ZHR had dropped to 7.1. The Western Australia observers reported that 56.5 % of the meteors were yellow, while 19.6 % were orange. Trains were observed among 16.1 % of the meteors and the average magnitude of 447 meteors was 1.97. 83 It is interesting that 1 year later, the Western Australia group detected a maximum ZHR as high as 12.7 on April 23/24, and estimated the average meteor magnitude as 2.33.84 At the 1987 return of comet 26P, Wood reported, “In numerous hours of observation from all parts of Australia, only three possible G-S meteors were seen April 19–25. At predicted time of maximum, however, the radiant was below the horizon.” Nevertheless, Wood suggested that no outburst probably occurred.85 Reports by Wood for the period of 1988–1995 revealed very little activity, with the best reported rates being 1–3 per hour during 1988 April 21/22–23/24. He added that on the night of 1988 April 22/23, when the radiant was still 15° below the horizon, several fi reballs were seen.86, 87,88, 89 80 5 April Meteor Showers

No predictions or observations were reported again until 2002, when S. Messenger modeled the dust stream produced by comet 26P. He found, “A moderate change in the orbit … during the 1987 apparition led to the formation of a second, distinct dust trail….” Messenger noted that Earth would encounter small particles from this second trail during 2003 April 23/2490 ; however, no meteor shower was observed. J. Vaubaillon (2005) suggested the lack of a shower was the result of the very low entry velocity and the small size of the particles. He noted that if a display had occurred, it may have only been detected using radio equipment. On the other hand, Vaubaillon noted that if a formula created by D. W. Hughes91 was applied, the visual magnitude of the particles might have only reached 14, which is even beyond the detection of radio equipment.92 Activity has not spread completely around the orbit of comet Grigg-Skjellerup. Subsequently, none of the photographic or radio-echo surveys have ever detected meteors from the Pi Puppids. The orbit labeled “1977/1979” was calculated by the Author using the radiant determined by the Western Australia observers during 1977 and 1979, using an assumed semimajor axis of 3.00 AU. The orbit labeled “1947” is the comet’s orbit in 1947, at the time that Hoffmeister ﬁ rst suggested meteor activity, and the orbit labeled “2013” is the most recent orbit of the comet. The differences are caused by rather frequently close approaches to Jupiter.

w Ω (2000) i q e a 1977/1979 7.4 211.3 14.1 1.002 0.665 3.00 1947 356.38 216.09 17.64 0.8531 0.7043 2.89 2013 2.15 211.55 22.42 1.0859 0.6401 3.02

April Ursids

The April Ursids were observed extensively during the last third of the nineteenth century and into the twentieth century, but their current appearance seems primarily limited to occasional bright meteors and telescopic activity. The April Ursids were fi rst observed by E. Heis (Münster, Germany) during 1849–1861 April 16–30, when he determined the radiant position as a = 150°, d = +61°.93 G. Zezioli (Bergamo, Italy) detected this radiant on several occasions while plotting meteors during 1868 and 1869. According to G. V. Schiaparelli’s analysis, Zezioli observed 12 meteors from a = 142°, d = +53° on 1868 April 25 ( l = 36°), ten meteors from a = 168°, d = +47° on 1868–1869 April 14, and ten meteors from a = 163°, d = +47° on 1869 April 10 (l = 21°). 94 All of these radiants possessed D-criterions of 0.04–0.10. Although a few additional radiants were detected during the 1870 s, only occasional fi reball and stationary meteor observations were made during the next 30 years. Finally, during 1915 April 14–18 ( l = 24°–28°), W. F. Denning plotted four Virginid Complex: Antihelion 81 meteors from a = 161°, d = +58°.95 There was no success in fi nding any other visual observations. Individual meteors continue to appear from this stream. Six photographic meteors were detected in three surveys during the period of 1950–1969. The indicated duration is April 7–23 (l=, with an average radiant of a = 173.7°, d = +59.0°). Several fi reballs have also been noted, which prompted C. P. Olivier to include a radiant from this stream in his “Catalogue of Fireball Radiants.” He determined the average position as a = 167°, d = +63° and estimated the duration as 6 days, centered on April 25.96 The most convincing modern-day support for this stream’s existence comes from the 1968 to 1969 session of the Radio Meteor Project. Z. Sekanina (1976) detected a stream active over the period of March 18-May 9. The nodal passage was given as April 18.7 ( l = 28.2°), at which time the radiant position was a = 149.3°, d = +54.9°. The geocentric velocity was determined as 8.6 km/s.97 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. This radiant from this meteor stream was detected on several occasions. The best match was a radiant at a = 148.7°, d = +52.5° that was determined by 21 meteors during April 18 (l = 28.0°); however, similar radiants within 10° of right ascension are present a few days before and after this date that might also be associated. The orbit labeled “Photo” was calculated based on six photographic meteor orbits. The orbit labeled “1968–1969” is from Sekanina (1976).

w Ω (2000) i q e a Photo 188.4 26.0 10.7 1.000 0.532 2.14 1968–1969 183.5 28.9 9.4 0.993 0.473 1.87

Virginid Complex: Antihelion

This is one of the largest regions of activity each year, completely spanning the months of March and April, but also including most of February and May. Several individual radiants seem to be active each year, but research seems to be showing that few of these radiants produce long-term activity. In the 1988 edition of this book, several of these streams were addressed individually and weaker Virginid radiants left out of the book entirely. For this edition it was decided to consider the region as a whole. C. Hoffmeister called this region the “Virginid current” and added that it is one of the “Ecliptical Currents” visible during the year. He considered the “Ecliptical Currents” to be “regarded as differing in principle from the cometary currents” and said they generally appear 165° west of the Sun and were caused by currents of meteors.98 82 5 April Meteor Showers

Today, Hoffmeister’s “Ecliptical Currents” are known as “antihelion” radiants. Photography and radio surveys have helped defi ne these radiants by determining the orbits of meteors emanating from this region. According to R. Lunsford (2004), “this material orbits the sun in low-inclination, direct orbits, and encounters the Earth on its inbound or pre-perihelion portion of its orbit.” The meteors encounter Earth perpendicular to our planet’s direction of motion. Lunsford suggests that the source of antihelion meteors is probably “a combination of material produced by the Jupiter family of comets and Earth-crossing asteroids.”99 The earliest observation of meteors from the Virginid Complex occurred on 1841 April 18 (l = 29°). According to S. C. Walker, at about 8:00 p.m., C. G. Forshey (Vidalia, Louisiana, USA) saw “an unusual number of meteors in different parts of the heavens, and on tracing their paths backwards, found that they traversed the Constellation Virgo.” Walker continued, “Having commenced precise observations at half past 8, and continued them for 3 h, he saw in 2 h and a quarter, 45 min being lost in recording, 60 meteors, of which, all but fi ve, passed within 10° from the common radiant point.” Forshey determined the radiant point as a = 198°, d = −8°. According to Walker, Forshey commented that the meteors were “chie fl y without trains, and of a reddish colour, few of them of the fi rst magnitude, and the greater number of the third and inferior magnitudes.”100 The date and position of this meteor shower is quite close to what would be expected for the Alpha Virginids, which has long been recognized as one of the strongest of the showers in this region. The results of some long-term observations were published in the early 1860s, which again revealed activity from the Virginid Complex. E. Heis (1864) used observations made during 1849–1859 and created half-month epochs for meteor showers. With respect to the Virginid region, he found radiants at a = 170°, d = +11° during February 15–28, a = 178°, d = +7° during March 1–15, a = 194°, d = +5° during April 16–30, and a = 198°, d = +4° during May 1–31.101 R. P. Greg (1865) looked at the observations published in the Report of the Annual Meeting of the British Association for the Advancement of Science from 1845 to 1863 and came up with his own list of radiants. With respect to the Virginid region, he found radiants at a = 168°, d = +9° during February 10-March 17 and a = 189°, d = +4° during April 2-May 1.102 Heis’ list was part of a letter that had been sent to A. S. Herschel. Herschel noted that the radiants of April and May were near the star Delta Virginis. He said he made an independent observation of this radiant on 1864 April 10 ( l = 22°). The result of this observation was later published by Denning, where 12 meteors came from a radiant at a = 192°, d = +4°.103 The date and position of this radiant is quite close to the Gamma Virginid radiant, which is another of the strongest showers in this region. G. V. Schiaparelli (1872) published a list of “Principal Meteoric Showers” that occurred during the fi rst half of the year during 1868–1870. He noted a radiant at a = 193°, d = +11° that was on seen on 1869 April 11 (l = 22°). He described it as “Extended; unexact.”104 In R. A. McIntosh’s “An Index to Southern Meteor Showers,” which was published in the Monthly Notices of the Royal Astronomical Society in 1935, meteor Virginid Complex: Antihelion 83 observations from the New Zealand Meteor Section, as well as from a few other sources in the United States, England, and Russia, were reduced. The outcome was a list of 320 radiants that were visible from the Southern Hemisphere. Although McIntosh did not speci fi cally note the large number of radiants that were visible in March and April from the Virgo region, there are several in his list, including the Alpha and Gamma Virginids. Interestingly, McIntosh noted four radiant groups “in which stationary radiation is apparently established….” One of these groups was numbered “114” and originated from near the star Alpha Virginis. The duration was given as April 4–30, and the radiant was at a = 208.5°, d = −10°. This was among the most widely observed radiants in McIntosh’s list, as 24 observed radiants were used to establish it. McIntosh added that when additional observations are made, this “stationary” radiant will probably “be resolved into a number of minor streams all showing the motion required by theory.”105 As noted earlier, Hoffmeister discovered this region. His book Meteorströme contained 5406 visual radiants that had been observed during the period of 1908– 1938, and radiants from the Virginid region were sprinkled throughout, including the Alpha Virginids and the Gamma Virginids. R. E. McCrosky and A. Posen (1959) announced the fi nding of seven new meteor streams amongst the photographic meteors captured during the Harvard Meteor Project of 1952–1954. One of these streams was called the “Alpha Virginids,” the orbit of which was based on nine approximate orbits. The indicated duration was May 1–9 and the probable date of maximum was given as May 5, when the average radiant was at a = 215°, d = −12°. They noted that there was some uncertainty in the ascending node of the orbit because, “The members fall into two groups whose nodes differ by 180°; this is not surprising, however, in view of the very small inclination of the orbit.”106 Z. Sekanina (1973) noted that the 1961–1965 session of the Radio Meteor Project, which used radio equipment at Havana, Illinois (USA), revealed several clusters of radiants along the ecliptic. He referred to one of these as “The Virgo Cluster.” Sekanina wrote, “A smaller but still quite extensive cluster of low-population streams has been disclosed in Virgo, and to a lesser extent in Leo. The mean radiants cover an area 40° in right ascension and 20° in declination,” with the center at a = 190°, d = 0°. Sekanina added, “The core of this cluster matches Hoffmeister’s Virginids.”107 A meteor-plotting project to study the Virginids was conducted by the meteor section of the Junior Astronomical Society (JAS) during March and April of 1988–1992. A. McBeath (1992) said a total of 198 possible Virginid trails were tallied. He said that when taken as a whole, the radiants defi ned a “roughly pentago- nal shape” in the sky. McBeath added that within this zone, “there is a clear tendency for radiants to be active in the more westerly area in March, which then seems to track eastwards later on into April. This is not unexpected, of course, though not all the radiants found follow this pattern.” In order to identify the probable individual radiants or groups within this area, McBeath created three time periods: March 1–21, March 22-April 9, and April 10–30. Ten fairly distinct radiants were identi fi ed, although McBeath indicated that some could be continuations 84 5 April Meteor Showers

Table 5.2 Radiants of the Virginid Complex (equinox 2000) Hoffmeister109 McBeath 108 Sekanina110 l (°) a (°) d (°) l (°) a (°) d (°) l (°) a (°) d (°) 344.3 179.8 +0.2 341–345 168 +10 342.3 161.6 +7.0 355.7 193.4 −1.9 351–355 184 −15 347.9 184.7 +0.2 1.6 187.0 −0.8 351–359 190 −6 349.3 182.8 +13.5 9.3 210.4 −0.8 1–20 195 +12 350.4 175.8 −1.8 12.6 200.3 −11.1 4–9 175 −18 355.3 196.6 −1.3 16.6 198.6 −6.5 7–11 195 −10 1.9 181.3 +11.2 24.3 206.0 −11.1 14–19 193 −17 11.9 211.2 −8.6 32.0 217.2 −11.1 21–40 207 +10 17.5 213.7 +3.4 44.7 220.2 −18.1 27–33 188 +3 18.4 204.3 −12.0 31–35 206 −3 25.2 189.3 −2.4

of radiants in other periods. There was an interesting comment made about “Radiant area 5” [l = 4°–9°] which could be representative of the character of the overall activity within the Virginid Complex. McBeath wrote, “A weak source, which is something of an oddity, since activity was detected from a fairly compact region only in 1990.” There was no trace in both 1988 and 1989.108 Table 5.2 compares the primary active radiants as published by Hoffmeister, Sekanina, and McBeath, and reveals little similarity between these three studies. So, not only are the radiants in this region composed of several apparently related meteor streams, the distribution of meteors within each stream is apparently not homogenous, explaining why different radiants are active in different years. The evolution of the Alpha Virginid stream was examined by E. I. Kazimirchak- Polonskaya and A. K. Terentjeva (1973). Adopting the orbit of meteor number 7333 from the Harvard Meteor Project as representing the orbit of this stream, ten groups were created at various positions along the stream’s orbit and then subjected to perturbations by seven planets (Venus to Neptune) over the interval 1860–2060. Examining the three most interesting groups, the Russian study demonstrated how Jupiter’s inﬂ uence caused the stream to variously approach and move away from Earth’s orbit, as well as how the radiant moved by as much as 30° in both right ascension and declination. For group “I” of the study, it was found that the stream was within 0.085 AU of Earth’s orbit during the period of 1895–1991, with the date of maximum moving between solar longitudes 18° and 25° (April 8 and 15) and the radiant executing “looped motions over a 3° × 5° area....” Group “VI” was found to possess a very complicated motion, which caused it to approach and recede from Earth’s orbit three times during the interval examined. A diagram of the radiant at peak activity was given for each year, and it demonstrated how maximum could variously occur between solar longitudes 1.5° and 51.6° (March 22 to May 12). The authors noted that these old dates of maximum would persist—eventually causing activity to be present from this stream for a period of 51 days. Between 1860 and 2051, the radiant producing maximum activity for this group would be expected to Virginid Complex: Antihelion 85 move within an elliptical area with dimensions of 15° × 31°. For the third group, perturbations caused changes that generally lay between the two groups already discussed.111 Overall, the authors concluded, “perturbations by Jupiter represent the principal factor governing the evolution of the meteor streams belonging to its family and the evolution of their radiants. The magnitude and character of these perturbations has a strong inﬂ uence on the size of the shower radiation area and the length of time that the shower remains visible.”112 The calculated duration of the activity coincides very well with present observations of the Virginid Complex, as does the large, diffuse area. Several associations have been suggested for different observed components of the Virginid Complex. S. S. Mims (1980) suggested a relationship between the “Virginids” and a comet discovered by J. Dunlop (Paramatta, New South Wales, Australia) on 1833 September 30. The comet was only observed 15 times in 16 days, by a few observers in South Africa and Australia, so that the orbit is considered as somewhat uncertain. Nevertheless, during 1888, L. Schulhof showed that the eccentricity could be as small as 0.8. Mims pointed out that the orbits of the comet and meteor stream are close except for the longitude of perihelion, which is about 50° off. He suggested that, if the comet was indeed of short period, it may “have been perturbed (by Jupiter) before 1833....” Although realizing that several assumptions would have to be accepted to support some of his suggestions, Mims added, “it is interesting to think that we could learn much more today about a comet observed for only a short period in the early nineteenth century…”.113 Thus the suggestion in the Journal of the International Meteor Organization in 1989 that asteroid “1988 TA” might be associated with the Alpha Virginid stream, especially the May branch. In this case, all of the elements are a very close match, except for the perihelion distance, although this latter parameter is close to Sekanina’s March Virginid stream (see orbits below).114 No single orbit can represent the Virginid Complex. Sekanina (1976) analyzed the data from the 1968 to 1969 session of the Radio Meteor Project and published the largest set of orbits for then-active radiants. These are as follows:

w Ω (2000) i q e a Rho LEO 84.9 162.8 0.5 0.618 0.711 2.14 Pi VIR 303.9 348.6 2.9 0.289 0.839 1.79 N. Eta VIR 281.8 350.0 11.3 0.501 0.703 1.69 S. Eta VIR 101.8 171.1 2.6 0.499 0.706 1.70 Southern VIR 310.6 356.0 6.4 0.288 0.759 1.20 March VIR 256.4 2.6 2.4 0.853 0.238 1.12 Northern VIR 310.3 12.6 4.8 0.278 0.785 1.30 April VIR 291.5 18.2 15.3 0.434 0.711 1.50 Alpha VIR 106.6 199.2 1.5 0.477 0.691 1.54 Gamma VIR 241.2 25.5 0.5 0.829 0.517 1.72 86 5 April Meteor Showers

The possible associations are given as follows:

w Ω (2000) i q e a C/1833 S1 259.58 325.59 7.35 0.4581 1.0 ∞ 1988 TA 104.76 195.03 2.54 0.8031 0.4789 1.54

1. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 2 . http://www.imonet.org/showers/shw064.html 3. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), p. 422. 4. A. F. Cook, B. A. Lindblad, B. G. Marsden, R. E. McCrosky, and A. Posen, Smithsonian Contributions to Astrophysics , 15 (1973), pp. 1–5. 5. Z. Sekanina, Icarus , 18 (1973), pp. 255, 258. 6. Z. Sekanina, Icarus , 27 (1976), pp. 276, 292. 7. T. L. Korovkina, V. V. Martynenko, and V. V. Frolov, Solar System Research , 5 (1971), p. 100. 8. N. V. Smirnov and T. L. Korovkina, Solar System Research , 8 (1975), p. 99. 9. Virginia Gazette and General Advertiser , 17 (1803 Apr. 23), p. 3. 10. Boston Weekly Magazine , 1 (1803 June 4), p. 3. 11. E. C. Herrick, American Journal of Science and Arts , 35 (1839 Jan.), p. 366. 12. F. J. D. Arago, Annuaire pour l’an 1836, présenté par le Bureau des Longitudes. Paris (1835), p. 297. 13. J. F. Benzenberg, Astronomische Nachrichten , 15 (1838 Sep. 13), pp. 323–8. 14. E. C. Herrick, American Journal of Science and Arts , 36 (1839 Apr.–Jul.), pp. 358–63. 15. E. C. Herrick, American Journal of Science and Arts , 40 (1841 Jan.–Mar.), p. 358. 16. L. A. J. Quetelet, Nouveaux Mémoires de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 12 (1839), pp. 19–20. 17. E. C. Herrick, American Journal of Science and Arts , 42 (1842 Jan.–Mar.), p. 398. 18. E. C. Herrick and E. Loomis, American Journal of Science and Arts, 43 (1842 Apr.–Jun..), p. 214. 19. E. C. Herrick, American Journal of Science and Arts (2nd series) , 8 (1849 Nov.), p. 429. 20. Report of the Annual Meeting of the British Association for the Advancement of Science , 21 (1852), p. 48. 21. Report of the Annual Meeting of the British Association for the Advancement of Science , 33 (1864), p. 325. 22. A. Walker, Report of the Annual Meeting of the British Association for the Advancement of Science , 33 (1864), pp. 256–7. 23. R. P. Greg, Proceedings of the British Meteorological Society , 2 (1865 Jan.) p. 315. 24. H. A. Newton, American Journal of Science and Arts (2nd series) , 36 (1863 Jul.), p. 146. 25. D. W. Pankenier, Z. Xu, and Y. Jiang, Archaeoastronomy in East Asia . Amherst, New York: Cambria Press (2008), p. 306. 26. M. Chasles, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 12 (1841 Mar.), p. 501. 27. D. W. Pankenier, Zhentao Xu, and Yaotiao Jiang, Archaeoastronomy in East Asia . Amherst, New York: Cambria Press (2008), p. 313. 28. A. S. Herschel, Report of the Annual Meeting of the British Association for the Advancement of Science , 34 (1865), pp. 40–43, 98. 29. Report of the Annual Meeting of the British Association for the Advancement of Science , 35 (1866), pp. 92–5. 30. E. Weiss, Astronomische Nachrichten , 68 (1867 Mar. 9), p. 382. 31. J. G. Galle, Astronomische Nachrichten , 69 (1867 Apr. 2), p. 33. Virginid Complex: Antihelion 87

32. H. Corder, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), p. 135. 33. H. Corder, The Observatory , 5 (1882 Jun.), pp. 175–6. 34. W. F. Denning, The Observatory , 7 (1884 Aug.), p. 217. 35. W. F. Denning, Nature , 32 (1885 May 7), p. 5. 36. H. N. Russell, Popular Astronomy , 31 (1923), p. 174. 37. W. F. Denning, The Observatory , 45 (1922 Jun.), pp. 193–4. 38. A. G. Cook, Memoirs of the British Astronomical Association , 24 (1924), pp. 53–4. 39. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923), p. 46. 40. C. P. Olivier, Popular Astronomy , 54 (1946 Jun.), p. 305. 41. V. Porubcan and J. Stohl, Contributions of the Astronomical Observatory Skalnaté Pleso, 11 (1983), pp. 172–3, 178. 42. B. G. Marsden, International Astronomical Union Circular , No. 3691 (1982 Apr. 28). 43. V. Porubcan and G. Cevolani, Contributions of the Astronomical Observatory Skalnaté Pleso , 13 (1985), p. 251. 44. V. Porubcan and B. A. McIntosh, Bulletin of the Astronomical Institutes of Czechoslovakia, 38 (1987), pp. 313–16. 45. E. C. Herrick, American Journal of Science and Arts , 40 (1841 Jan.–Mar.), p. 365. 46. D. Kirkwood, Nature , 1 (1870 Apr. 28), pp. 665–6. 47. W. F. Denning, The Observatory , 20 (1897 Apr.), pp. 174–5. 48. W. F. Denning, The Observatory , 37 (1914 Apr.), p. 178. 49. V. A. Malzev, Astronomiceskij Bjulleten , No. 24 (1929 May). 50. V. Guth, Bulletin of the Astronomical Institutes of Czechoslovakia , 1 (1947), pp. 1–4. 51. V. Porubcan and J. Stohl, Asteroids, Comets, Meteors 1991. Lunar and Planetary Institute (1992), pp. 469–72. 52. V. Porubcan, J. Stohl, and J. Svoren, Contributions of the Astronomical Observatory Skalnaté Pleso , 22 (1992), pp. 25–31. 53. F. L. Whipple, The Astronomical Journal , 59 (1954 Jul.), pp. 201–17. 54. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 14–24. 55. Z. Sekanina, Icarus , 13 (1970), p. 476. 56. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2. 57. K. B. Hindley, Journal of the British Astronomical Association , 79 (1969), pp. 477–80. 58. K. Fox, Asteroids, Comets, Meteors II. eds. Rickman, H., and Lagerkvist, C.-I., Uppsala: University of Uppsala (1986), pp. 522–4. 59. B. A. Lindblad and V. Porubcan, Asteroids, Comets, Meteors 1991. Lunar and Planetary Institute (1992), pp. 367–70. 60. V. Porubcan and L. Kornos, Earth, Moon, and Planets , 102 (2008 Jun.), pp. 91–4. 61. V. Porubcan and J. Stohl, Contributions of the Astronomical Observatory Skalnaté Pleso, 11 (1983), pp. 169–84. 62. A. Dubietis and R. Arlt, WGN, Journal of the International Meteor Organization , 29 (2000), pp. 119–33. 63. M. Buhagiar, Western Australia Meteor Section Bulletin , No. 160 (1981). 64. G. W. Kronk, Cometography , volume 3. United Kingdom: Cambridge University Press (2007), pp. 106–8. 65. J. Wood, Personal Communication (1986 Oct. 15). 66. J. Wood, WGN, Journal of the International Meteor Organization , 15 (1987 Aug.), pp. 131–2. 67. P. Jenniskens, Astronomy & Astrophysics , 287 (1994), p. 1007. 68. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226–8, 241. 69. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 188. 70. P. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 330. 71. P. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 209 (2010), pp. 70, 72, 78. 72. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 100. 73. S. E. Hamid, Astronomical Journal , 54 (1948), p. 39. 74. J. G. Porter, Comets and Meteor Streams . London: Chapman & Hall LTD (1952), p. 92. 88 5 April Meteor Showers

75. G. Sitarski, Acta Astronomica , 14 (1964), pp. 32, 35–6. 76. H. B. Ridley, International Astronomical Union Circular , No. 2371 (1971 Nov. 22). 77. B. Edwards, Meteor News , No. 11 (1972 Jun.), p. 6. 78. Meteor News , No. 12 (1972 Aug.), p. 5. 79. W. J. Baggaley, The Observatory , 93 (1973 Feb.), pp. 23–6. 80. G. Sitarski, International Astronomical Union Circular , No. 3055 (1977 Mar. 30). 81. M. Buhagiar, International Astronomical Union Circular , No. 3092 (1977 Jul. 25); J. Wood, Personal Communication (1986 Oct. 15). 82. J. D. Drummond, Meteor News , No. 57 (1982 Apr.), p. 7. 83. K. Simmons, Meteor News , No. 58 (1982 Jul.), pp. 7–8. 84. J. Wood, Meteor News , No. 63 (1983 Oct.), p. 9. 85. J. Wood, WGN, Journal of the International Meteor Organization , 17 (1989 Feb.), pp. 24–5. 86. J. Wood, Meteor News , No. 85 (1989 Apr.), p. 9. 87. J. Wood, Meteor News , No. 93 (1991 Apr.), p. 4. 88. J. Wood, Meteor News , No. 99 (1992 Fall), p. 9. 89. J. Wood, Meteor News , No. 110 (1995 Fall). 90. S. Messenger, Meteoritics & Planetary Science , 37 (2002), pp. 1495, 1497, 1502. 91. D. W. Hughes, Earth, Moon, and Planets , 68 (1995), pp. 37–40. 92. J. Vaubaillon, Astronomy & Astrophysics , 431 (2005), pp. 1139–44. 93. H. A. Newton, American Journal of Science and Arts (2nd series) , 43 (1867), p. 286. 94. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), pp. 254, 258. 95. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923 Nov.), p. 51. 96. C. P. Olivier, Flower Observatory Reprint , No. 146 (1964), p. 13. 97. Z. Sekanina, Icarus , 27 (1976), pp. 277, 293. 98. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p 172. 99. R. Lunsford, WGN, Journal of the International Meteor Organization , 32 (2004 Jul.), p. 81. 100. S. C. Walker and C. B. Forshey, Proceedings of the American Philosophical Society , 2 (1841 May & Jun.), pp. 67–8. 101. E. Heis, Monthly Notices of the Royal Astronomical Society , 24 (1864 Jun.), pp. 213–14. 102. R. P. Greg, Report of the Annual Meeting of the British Association for the Advancement of Science , 34 (1865), p. 99. 103. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 260. 104. G. V. Schiaparelli, Report of the Annual Meeting of the British Association for the Advancement of Science , 41 (1872), p. 47. 105. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), pp. 711, 713. 106. R. E. McCrosky and A. Posen, The Astronomical Journal , 64 (1959 Feb.), pp. 26–7. 107. Z. Sekanina, Icarus , 18 (1973), p. 275. 108. A. McBeath, WGN, Journal of the International Meteor Organization , 20 (1992 Dec.), pp. 230–2. 109. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 138. 110. Z. Sekanina, Icarus , 27 (1976), pp. 275–7. 111. E. I. Kazimirchak-Polonskaya and A. K. Terentjeva, Soviet Astronomy , 17 (1973 Nov.–Dec.), pp. 368–76. 112. E. I. Kazimirchak-Polonskaya and A. K. Terentjeva, p. 375. 113. S. S. Mims, Meteor News , No. 48 (1980 Jan.), pp. 3–4. 114. G. W. Kronk, WGN, Journal of the International Meteor Organization , 17 (1989 Feb.), pp. 9–10. Chapter 6

May Meteor Showers

Eta Aquariids

Duration: April 20–May 20 (l = 30°–59°) Maximum: May 6 (l = 45.5°) Radiant : a = 337°, d = −1° ZHR: 55

Radiant Drift: a = +0.96°, d = +0. 37° V G : 65 km/s

This meteor shower has never been an easy target for observers in the Northern Hemisphere; nevertheless, it was the fi rst shower to be associated with the periodic comet 1P/Halley. Hints that a shower might be active at the end of April and in early May began in 1863, when H. A. Newton examined the dates of ancient showers and suggested a series of periods which deserved the attention of observers. One of those periods was April 28–30 and included observed showers observed in the years 401, 839, 927, 934, and 1009.1 The Eta Aquariids were fi rst observed in 1869 or 1870. J. F. J. Schmidt (Athens Observatory, Greece) had suggested to G. L. Tupman that he should spend some time observing meteors while cruising on the Mediterranean Sea. Tupman did just that during 1869–1871, including spending some time observing meteors during the period of midnight to dawn, which was a period rarely covered by other observers. He fi rst observed this meteor shower during one of those early morning observing sessions on 1869 April 29. He determined the radiant as a = 329°, d = −2° and considered it “fairly accurate.” He con fi rmed the radiant in 1870, when he noticed activity on April 30 from a radiant at a = 325°, d = −3° and on May 2–3 from a radiant at a = 325°, d = −2.5°. He wrote, “Fine shower, May 2.” 2 It should be noted that

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 89 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_6, © Springer Science+Business Media New York 2014 90 6 May Meteor Showers

Tupman’s list was reprinted in the Report of the Forty-Fourth Meeting of the British Association for the Advancement of Science (1875), but the 1869 observation was printed as 1871.3 There is no explanation to go with this change, and errata were not found in the Monthly Notices of the Royal Astronomical Society to indicate the original list published in 1873 contained an error. Virtually all authors reference the source with the 1871 date. Tupman’s observations were not followed up in the immediate years that followed, despite the fact that his radiant list, from which the Eta Aquariid observations were a part of, was published in other journals and added to the radiant lists of R. P. Greg, W. F. Denning, and others. Denning reported in the 1883 January issue of the Monthly Notices of the Royal Astronomical Society that Tupman was not alone in seeing this meteor shower in 1870. He said that observers in Italy published a catalog in 1882, which contained meteor paths from observations made in 1868, 1869, and 1870. Denning plotted 229 paths that were seen during April 29–May 6 and found that 45 were “Aquariads”. He determined the radiant as a = 334°, d = −9° and said activity was seen from April 29 to May 6. Denning noted that the average length of the meteors was 34.7°, which he said was “much greater than the ordinary length of meteor tracks.”4 A. S. Herschel (1876) discovered something, which at least began to generate a greater interest in this meteor shower. He calculated the theoretical radiant points of several comets, including many that were not included in an earlier list published by E. Weiss. Herschel found that the famous periodic comet 1P/Halley might produce a meteor shower in early May. Using the orbit from the comet’s appearance in 837, Herschel found the peak could occur on May 1 from a radiant at a = 334.5°, d = −16°. He also used the orbit from the comet’s latest appearance in 1835 and noted a possible peak of activity on May 4 from a radiant at a = 337°, d = 0°.5 During 1878, Herschel linked several of the theoretical radiants in his list to observed meteor showers and noted that Tupman’s radiants were very near this prediction.6 During the same month that Herschel’s 1878 paper was published, another observation of the Eta Aquariids was made. H. Corder (Writtle, Essex, England) detected activity on the morning of 1878 May 4, with three plotted meteors revealing a radiant at a = 334°, d = −1°. He noted they were remarkable for their long paths across the sky.7 Corder (1880) published a list of 95 radiants he had observed during 1876–1879. He said he generally observed during the evenings but made some morning watches. Radiant number 23 was referred to as the “Aquariads” and were seen during April to May from an average radiant of a = 334°, d = −5°. He noted, “Fine long meteors at daybreak.”8 From the few observations presented so far, it can be seen that one reason the Eta Aquariids were poorly observed was because they were only visible during the morning. But the main reason they were not well seen is because of the observer’s latitude. Tupman’s observations from the Mediterranean Sea allowed him to see the radiant reach an altitude of about 22° before twilight began, while Corder’s observations from England only allowed him to see the radiant reach an altitude of about 4° before twilight began. Corder’s location also explains his description of “long Eta Aquariids 91 meteors at daybreak,” because some of the meteors he would have seen would be what are called “Earthgrazers.” Earthgrazers are meteors that are coming from a radiant that is below or very near the horizon, so that they are moving almost parallel to our atmosphere and only grazing it. Because they are not diving down into the thicker atmosphere, Earthgrazers do not burn up as fast as regular meteors and can travel far across the sky, sometimes even skipping back into space. Denning compiled a paper of fi reball radiants that was published in the 1884 April issue of the Monthly Notices of the Royal Astronomical Society. The radiant labeled “IX” was composed of fi reballs observed during the period of April 29–May 5. The average radiant was determined as a = 335°, d = −9°, which Denning noted was near the star Theta Aquarii. He added that this was Tupman’s shower, which he said was about 11° away.9 Denning fi nally managed to observe the shower during 1886 April 30–May 6. A total of 11 plotted meteors revealed a radiant at a = 337°, d = −2.5°. From these observations, he stated that the radiant seemed 5°–7° in diameter. He added that the apparent closeness of this radiant to that predicted by Herschel placed the identity of this shower to Halley’s comet “beyond doubt.”10 Only a few observations were made of this shower during the remainder of the nineteenth century, with each observer describing the meteors as swift. Corder reported seeing this shower on 1893 April 20 from a radiant at a = 338.5°, d = −3.5°.11 W. H. Milligan (England) plotted two meteors from a radiant at a = 338.5°, d = −3.5° during 1894 May.12 Corder plotted two meteors from a radiant at a = 339°, d = −4° during 1895 May 1–4.13 T. W. Backhouse (England) plotted three meteors from a radiant at a = 337°, d = −1° during 1896 May 2–4. 14 Herschel (England) plotted four meteors on 1899 May 3–9 and determined the radiant as a = 335°, d = −1°.15 As the century came to a close, nothing new had been learned about these meteors in over two decades, with our total knowledge including a vague reference to their speed, their period of visibility, their radiant position, and their association to comet Halley. There continued to be a dearth of observations as the twentieth century began. P. M. Ryves (Stevenage, Hertfordshire, England) plotted four meteors on 1902 May 5 from a radiant at a = 336°, d = −3°.16 G. M. Knight (Hampstead, Greater London, England) plotted 22 meteors from a radiant at a = 336°, d = −3° during 1903 April 30–May 3. He referred to it as the “Gamma Aquarids.”17 It appears that the next observation of the Eta Aquariids came in 1910, when two professional astronomers accidentally noted activity. On the morning of May 4, C. P. Olivier and H. D. Curtis were working in Lick Observatory’s Crossley dome (California, USA) when they saw “quite a number of meteors … in the southeast….” Olivier remembered that the Eta Aquariids were supposed to be active at that time, so he began plotting their paths. Six meteors indicated a radiant at a = 334.0°, d = −3.4°. Olivier again looked for meteors on the morning of the 5th, but only noticed two possible Eta Aquariids; however, six more meteors were noticed on the morning of May 11, which indicated a radiant at a = 342.0°, d = −0.6°. Since the velocity of the meteors was not known, Olivier calculated parabolic orbits for the two radiants and compared them to the orbit of comet Halley. 92 6 May Meteor Showers

He wrote, “The close resemblance of the elements leaves no reasonable doubt that these meteors were intimately connected with the comet in time past and that they are now moving in nearly identical orbits.”18 Two years later, Olivier took three radiants from 1910 and three from 1911, calculated both parabolic and elliptical orbits (the latter using the known semimajor axis of comet Halley), and obtained averages. Olivier wrote, “Considering the unavoidable errors of meteor observations, the agreement between the comet’s orbit and those of the meteor is good, and the results fully con fi rm my fi rst conclusion as to the connection between the meteors and Halley’s Comet.”19 Olivier made an interesting discovery around this same time. During 1911, he became the fi rst person to note the strong similarity between the orbits of the Eta Aquariids and the Orionids.20 Fortunately, several good meteor observers appeared in the southern hemisphere during the 1920s, and the knowledge of primarily southern meteor showers increased dramatically. One of the most prolifi c observers was R. A. McIntosh (Auckland, New Zealand) and he published one of the more signi fi cant studies of the Eta Aquariids during 1929. McIntosh stated that his observations of that year showed activity during April 22 and May 13, which he said presented “a good illustration of the dispersive action of the planets during the centuries that the parent comet has been in existence.” His fi rst radiant was determined on May 3.2 ( a = 334.0°, d = −1.5°), while the last came on May 12.19 (a = 342.7°, d = +2.5°). He stated that maximum defi nitely came in early May, though bad weather prevented it from being pinpointed; however, hourly rates remained between 10 and 20 during the period of May 2–11, once again illustrating the advantage of observing from more southerly latitudes. The radiant diameter was consistently about 5° across, and McIntosh’s orbital calculations showed excellent agreement with the orbit of Halley’s Comet.21 McIntosh (1935) published his investigation of the radiant motion of the Eta Aquariids. Using observations made by M. Geddes (New Zealand) and himself during 1928–1933, he precisely determined the radiant’s daily motion as +0.96° in a and +0.37° in d . 22 He also plotted the observed activity of this stream and developed an activity curve that revealed the shower to begin with rates of 1 per hour on April 28, then rapidly rise to a fl at maximum of 10 per hour during May 3–6, and fi nally slowly decline to rates of 1 per hour by May 16.22 Beginning in 1947, the Eta Aquariids joined the ranks of the fi rst streams to be detected by radio-echo techniques. Astronomers at the Jodrell Bank Experimental Station (Lower Withington, Cheshire, England) detected meteors from this stream during May 1–10 using radio transmitters and receivers to track ionization activity in the atmosphere. J. A. Clegg, V. A. Hughes, and A. C. B. Lovell (1947) determined the average radiant as a = 339°, d = 0° and gave the maximum hourly rate as 12. 23 Little additional data was gathered about this stream by the Jodrell Bank observers during the remainder of the 1940s and 1950s. In fact, the stream was largely ignored since the radio equipment was rarely operated during the early half of May. The Springhill Meteor Observatory (Ottawa, Canada) was constructed as part of the Canadian program of the International Geophysical Year. It went into operation Eta Aquariids 93 during 1957 July and began 24 h-a-day operation in 1957 October. It fi nally shut down on 1968 January 5 after accumulating about 15 million meteor echoes. A. Hajduk (1973) analyzed roughly 240,000 echoes that had accumulated during the period of May 1–10 during 1958–1967. He noted that there was an “instability of meteor frequencies in individual returns,” which he attributed to “variations of the stream density along the orbit.” Hajduk said “no regular periodicity in the shower activity can be identi fi ed.” He did fi nd that two apparent radar maxima occurred: one on May 4 and the other on May 7. These fi gures represented all radio echoes, but a further study of only the long-duration echoes (lasting ³ 1 s) revealed the same two dates of maxima, except the decline between the two dates was not as pronounced. Also present was a further rise to maximum that came on May 10.24 Hajduk also compared the Springhill numbers on the Eta Aquariids to an earlier study he had published on the Orionids. He said the similarities between the two streams include “similar variations of the density along the stream orbit, the gradual displacement of the maxima along the solar longitude, the general particle size distribution in the streams, the width of the shower activity, and the presence of a core of larger particles.” In terms of differences between the two streams, Hajduk noted, “a larger spread of the frequencies of the Orionids, a disagreement between the peak frequencies in individual returns, and a high proportion of long-duration echoes during the Eta Aquarid period may be explained by different positions of the Earth within the stream at the two nodal passages, especially by the difference in the minimum distance from the stream’s centre.”25 B. A. McIntosh and Hajduk (1983) investigated the evolution of this stream and published the details of a proposed model of how it was produced by comet Halley. Using a 1981 study published by D. K. Yeomans and T. Kiang, which examined the orbit of comet Halley back to 1404 BC,26 McIntosh and Hajduk suggested “the meteoroids simply exist in orbits where the comet was many revolutions ago.” Further perturbations have acted to mold the stream into a shell-like shape containing numerous debris belts. These belts are considered as the explanation as to why both the Orionids and Eta Aquariids experience activity variations from 1 year to the next.27 During the 1985–1986 apparition of Halley’s Comet, several meteor organiza- tions around the world put their members on alert to check for possible increased activity in the Eta Aquariids (and the Orionids). Reports from groups in Australia, New Zealand, Bolivia, North America, and Japan indicated that no enhanced activity from this stream was present. A. Dubietis (2003) examined the long-term activity of the Eta Aquariids and Orionids. He wrote, “In general, the h -Aquarids exhibit similar structural features ( fi laments) to the Orionids. The existence of a fi lamentary structure has been justifi ed from radio…and, to some extent, from visual observations.” Examining visual observations of the Eta Aquariids spanning 1986–2001, Dubietis stated that the population index (r) is about 2.4, which is similar to the Orionids. He also pointed out that the Eta Aquariid population index reached a clear minima of 2.18 in 1992, while a clear minima was reached by the Orionids in 1993. The ZHR of the Eta Aquariids varied from 39 to 87.28 94 6 May Meteor Showers

Eta Aquariids 160

140

120

100 Z H 80 R 60

0 15 25 35 45 55 65 75 Solar Longitude

This represents a decade of observations of the Eta Aquariids meteor shower. The observations were made by members of the International Meteor Organization during the 2000s and 2010s. The solar longitude basically represents 60 days, illustrating the roughly month-long duration of the shower and the peak lasting a couple of days

The orbit labeled “1961–1965” is from Z. Sekanina (1970).29 The orbit labeled “2002–2008” is from P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). 30

w W (2000) i q e a 1961–1965 79.5 45.6 161.2 0.468 0.834 2.82 2002–2007 89.6 45.5 163.0 0.533 0.907 5.7

Epsilon Aquilids

The discovery of the Epsilon Aquilids should be credited to B. L. Kashcheyev and V. N. Lebedinets (1967). They used three receiving stations operating at a wavelength of 8 m at the Kharkov Polytechnical Institute (Ukraine) and detected 17 radio meteors from this stream during 1960 May 4–27. They determined the date of the nodal passage as May 17, at which time the radiant was located at a = 276°, d = +13°.31 This stream was again detected in 1969, during the second session of the Radio Meteor Project, which used radio equipment at Havana, Illinois (USA). Z. Sekanina (1976) detected meteors during the period of May 19–21, determining the date of the nodal passage as May 20.3 (l = 58.8°) and the radiant as a = 284.1°, d = +15.5°. The geocentric velocity was determined as 30.8 km/s. 32 It should be noted that the Daytime Epsilon Arietids 95 equipment was shut down during May 10–18, so that it is likely both the date of nodal passage and the radiant might have been altered had the radar been in operation during mid-May. This radiant was detected by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system during 2002–2008, they detected 991 meteors from this stream. These meteors indicated a duration from May 11–16 (l = 51–55°), with maximum occurring on May 15 (l = 54°) from a radiant at a = 278.7°, d = +13.4°. The geocentric velocity was 31.4 km/s, while the radiant drift was determined as +1.1° in a and +0.23° in d per day.30 The International Meteor Organization has a website containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. Weak traces of this stream do exist. At l = 55°, 10 meteors indicated a radiant at a = 289.6°, d = +14.0°, at l = 57°, 32 meteors indicated a radiant at a = 275.5°, d = +19.0°, and at l = 58°, 45 meteors indicated a radiant at a = 288.1°, d = +14.0° and 30 meteors indicated a radiant at a = 275.7°, d = +14.0°. 33 It was not possible to locate visual or photographic observations of this meteor shower. The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1960 312 56 56 0.35 0.64 0.96 1969 318.3 59.5 59.6 0.354 0.594 0.87 2002–2008 317.61 54.0 59.2 0.3356 0.624 0.89

Daytime Epsilon Arietids

Duration: April 25–May 27 (l = 35–66°) Maximum: May 9 (l = 48.7°) Radiant: a = 44°, d = +21° ZHR: Low

Radiant Drift: a = UNK°, d = UNK° V G : 21 km/s

The discovery of this daylight meteor shower should be attributed to C. S. Nilsson (1964). During the interval of 1961 May 19–27, the radio equipment at the University of Adelaide (South Australia, Australia) detected six members of this stream, which indicated a radiant of a = 58.8°, d = +23.7°. Nilsson commented that W. G. Elford had “reanalyzed the data using the stream search program of Southworth and Hawkins and suggests that the May day-time shower is due to the S. Taurid stream....” Nilsson commented that the agreement was good when the angular elements of the orbits were considered, but said the eccentricity was 96 6 May Meteor Showers

“slightly low.”34 It should be pointed out that the radio equipment did not operate during May 1–18, so it is possible that the shower could have been active sooner than indicated. The Epsilon Arietids were next detected in 1969, during the second session of the Radio Meteor Project. Z. Sekanina analyzed the data obtained by the equipment at Havana, Illinois (USA), and noted that meteors were detected during the interval of April 25–May 22. The established date of the nodal passage was given as May 8.5 ( l = 47.4°), at which time the radiant was a = 43.6°, d = +20.9°. The geocentric velocity was determined as 20.6 km/s.32 It should be noted that the radar did not operate during May 24–June 1. The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1969” is from Sekanina (1976).

w W (2000) i q e a 1961 89.6 62.9 2.7 0.604 0.71 2.08 1969 90.1 48.0 2.8 0.592 0.708 2.03

Daytime May Arietids

Duration : May 4–June 6 (l = 44–76°) Maximum : May 16 (l = 55.5°) Radiant : a = 37°, d = +18° ZHR : Low

Radiant Drift : a = +0.96°, d = +0.3° V G : 27 km/s

C. S. Nilsson (1964) was the ﬁ rst to announce this daytime stream. He found 11 meteors while analyzing data acquired by the radio equipment of the University of Adelaide (South Australia, Australia). Meteors from this stream were detected during 1961 May 19–28. The date of the nodal crossing was determined as May 23 ( l = 62.1°), at which time the radiant was at a = 46.5°, d = +19.1°. The geocentric velocity was 26.4 km/s.35 The ﬁ rst detection of this stream was by the radio equipment at the Kharkov Polytechnical Institute (Ukraine) from 1960 May 5 to 27. B. L. Kashcheyev and V. N. Lebedinets (1967) analyzed the data and found 16 meteors that indicated a nodal crossing on May 15 (l = 54°), at which time the radiant was at a = 41°, d = +23°.36 During the 1968–1969 session of the Radio Meteor Project, the radio equipment at Havana, Illinois (USA) detected 56 meteors from this stream. Z. Sekanina (1976) analyzed the data and found the duration to be May 7–June 6 (l = 47°–76°), with a nodal crossing on May 15.6 (l = 54.3°). The average radiant was at a = 36.5°, d = +17.8°, while the geocentric velocity was determined as 25.2 km/s.32 The three sets of radio observations above are now referred to as the Northern Daytime May Arietids. This stream has not been detected by the Canadian Meteor Orbit Radar (CMOR), but a stream with a very similar orbit [w and W are off by Daytime Omicron Cetids 97

180°] has been detected and its radiant is about 7° to the south. This new stream has been called the “South Daytime May Arietids.” P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) analyzed data acquired by CMOR during the period of 2002–2008 and located 3,289 meteor orbits belonging to this new stream. They found the duration as April 26–May 20 (l = 36–59°) and noted a maximum on May 15 (l = 54°) from a radiant at a = 36.3°, d = +10.8°. The geocentric velocity was 28 km/s and the radiant drift was given as +0.96° in a and +0.3° in d per day.30 The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1960 74 55 6 0.44 0.77 1.94 1961 64.9 62.7 2.9 0.391 0.75 1.56 1968–1969 60.9 54.9 3.4 0.363 0.763 1.53 2002–2008 235.01 234.0 4.4 0.2957 0.817 1.61

Daytime Omicron Cetids

Duration: April 1–June 9 (l = 11°–77°) Maximum: May 9 (l = 49°) Radiant: a = 28°, d = −3° ZHR: Medium

Radiant Drift: a = +0.91°, d = +0.46° V G : 36 km/s

Astronomers at the Jodrell Bank Experimental Station (Lower Withington, Cheshire, England) discovered the Omicron Cetids in 1950. A. Aspinall and G. S. Hawkins (1951) said meteors were detected from this radiant on four dates in May and noted that activity was “weak and intermittent in character.” The hourly rate was 18 on the 14th and the radiant <3° across and centered at a = 27.5°, d = −3.5°. On the 16th, the hourly rate was 18 and the radiant was <3° across and centered at a = 28.5°, d = +0.0°. Hourly rates rose to 22 on the 21st and the radiant increased to 10° in diameter, while it was centered at a = 29.5°, d = −5.0°. The ﬁ nal observation came on the 23rd, when hourly rates dropped back to 18 and the radiant diameter decreased to <3°. The radiant was centered at a = 34.0°, d = +1.0°. 37 M. Almond (1951) took this same date and determined the corrected radiant position as a = 29.0°, d = −3.7° and also calculated an orbit.38 The Omicron Cetids were again detected by Jodrell Bank observers during 1951 May 14–17, with activity levels of 18–25 per hour, but were missed during 1952. Since the stream had generally produced activity levels greater than those observed for the Eta Aquariids, this prompted Almond, K. Bullough, and Hawkins 98 6 May Meteor Showers

(1952) to conclude that if the stream was present it “must have been less active than in 1950 or 1951.”39 The stream was possibly observed again at Jodrell Bank on 1953 May 17. Bullough (1954) gave the radiant as a = 11°, d = −2° and the hourly rate as 8. The radiant was less than 3° across.40 No further observations were made at this radio observatory during the period 1954–1958. C. S. Nilsson (1964) analyzed the data acquired by the radio equipment at the University of Adelaide (South Australia, Australia), which had surveyed the skies of the Southern Hemisphere for meteor streams in 1961. He used the Omicron Cetids as an example of a stream with an “uneven distribution of meteoroids,” noting “the stream has not been detected in later years.” Although no trace of the Omicron Cetids were located during the period indicated by the Jodrell Bank observers, there was a radiant in Nilsson’s list, designated “61.5.8,” which has a remarkably similar orbit to that calculated by Almond (1951). Composed of only three meteors, the duration was given as May 23–28, while the date of maximum occurred on May 25 (l = 64.9°) from an average radiant at a = 35.5°, d = +1.0°. The average geocentric velocity was 35.7 km/s.41 The extended period hinted at among Nilsson’s data was confi rmed during the fi rst session of the Radio Meteor Project. Z. Sekanina (1973) analyzed the data from 1962 to 1965 and identi fi ed 11 meteors indicating a duration of May 19–June 9. The nodal passage was given as May 27.9 ( l = 66.1°) and the average radiant position was a = 20.6°, d = +1.2°. The geocentric velocity was given as 34.6 km/s. 42 During the 1969 session, Sekanina again identifi ed 11 meteors from the Omicron Cetid stream, this time with a duration of May 7–21. He gave the nodal passage as May 9.0 ( l = 47.9°) and gave the radiant position as a = 21.5°, d = −4.0°. The geocentric velocity was determined as 36.6 km/s.32 The latest detection of this meteor stream was by the Canadian Meteor Orbit Radar during 2002–2008. According to P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010), daytime meteor activity was detected during the period of April 1 (l = 11°) to May 26 (l = 65°). The date of maximum activity came on May 9 ( l = 49°) from a radiant at a = 23.4°, d = −4.3° and the geocentric velocity as 37 km/s. Although the authors named this the “Southern Daytime Omega Cetids,” it is undoubtedly the same stream detected by earlier surveys. In addition, they also found a stream that they named the “Northern Daytime Omega Cetids.” This stream has a similar period of activity and a similar orbit, except that w and W are shifted by about 180°. It also peaks on May 9 ( l = 49°), but from a radiant at a = 11.8°, d = +18.9°. 30 The orbit labeled “1950” is from Almond (1951). The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1962–1965” is from Sekanina (1973). The orbit labeled “1969” is from Sekanina (1976). The orbit labeled “2002–2008-S” is from Brown et al. (2010) for the “Southern Daytime Omega Cetids.” The orbit labeled “2002–2008-N” is from Brown et al. (2010) for the “Northern Daytime Omega Cetids.” Eta Lyrids 99

w W (2000) i q e a 1950 211 238.7 34 0.11 0.91 1.3 1961 212.5 245.6 33.8 0.127 0.91 1.41 1962–1965 200.2 246.8 36.3 0.066 0.937 1.06 1969 213.9 228.6 32.6 0.122 0.925 1.62 2002–2008S 215.17 229.0 34.8 0.1282 0.924 1.70 2002–2008 N 32.13 49.0 34.8 0.1167 0.919 1.44

Eta Lyrids

Duration : May 3–May 14 (l = 43–53°) Maximum : May 8 (l = 48.0°) Radiant : a = 287°, d = +44° ZHR : 3

Radiant Drift : a = UNK, d = UNK V G : UNK km/s

The Infrared Astronomical Satellite (IRAS) discovered a new comet on 1983 April 25.85, but a delay in sending the news to the proper authorities allowed two independent discoveries to be made. G. Araki (Yuzawa, Niigata, Japan) spotted the comet on May 3.61, while G. E. D. Alcock (Peterborough, England) found the comet on May 3.92. 43 The comet is known as C/1983 H1 (IRAS-Araki-Alcock). The comet was offi cially announced to the world on May 4 and made a very close approach to Earth on May 11 (0.03 AU). It was followed until October 4. Five days after the announcement of this comet’s discovery, J. D. Drummond announced the possibility that the comet might produce a meteor shower. He determined the date of maximum as 1983 May 10.1 and the radiant as a = 289°, d = +44°.44 A. F. Cook and P. M. Millman reported no evidence of the shower among radio meteor data acquired in Ottawa (Canada) during a 72 h period centered on May 10.08, while S. Clifton (Marshall Space Flight Center, Huntzville, Alabama, USA) reported negative results while visually and photographically monitoring the predicted radiant during May 10.0–10.4.45 On the other hand, Drummond did report seeing a minor shower from Steward Observatory (Arizona, USA). He reported ZHRs of 5.1 on May 9.47, 4.1 on May 10.32, 3.2 on May 10.40, 3.1 on May 10.44, as well as some weak activity on May 11.46 This was not the fi rst recognition of the Eta Lyrids. A. K. Terentjeva (1968) conducted an analysis of over 3,700 photographic meteor orbits that had been acquired from 1936 to 1967. Five meteors were found and the duration was given as April 21–May 10. Terentjeva divided the meteors into three groups. Group “a” had a radiant at a = 289°, d = +43° and seems identical to what was predicted for activity from comet IRAS-Araki-Alcock; however, the orbits for groups “b” and “c” were similar to “a” and were believed to be related. The radiant for group “b” was at a = 288°, d = +52°, while the radiant for group “c” was at a = 287°, d = +52°.47 K. Ohtsuka (1991) searched through 5,800 photographic meteor orbits and found fi ve meteors photographed by surveys in the United States, Tajikistan, and 100 6 May Meteor Showers

Ukraine during 1953–1964, which belonged to this meteor stream. Two of these meteors had already been noted by Terentjeva. Ohtsuka determined the radiant as a = 289.0°, d = +43.3° and the geocentric velocity as 45.3 km/s. He also discussed another observation made on the night of 1983 May 9/10. He said C. Shimoda and K. Ono (Japan) were monitoring an FM radio frequency to detect “enhanced forward-scattering echoes” from meteors. They began detecting echoes of “some meteor shower” which peaked at 80 per hour on May 9.9 (l = 48.3°). Ohtsuka added, “This rate was twice as the background rate at the same time in the previous and following day.” He suggested that the negative result of Cook and Millman “was caused by the situation that the radiant point was below or near horizon in that place.” In addition, Ohtsuka said the original orbit of IRAS-Araki-Alcock indicates an orbital period of about 1,000 years. He said if particles were ejected during the comet’s previous perihelion passage at a rate of 1–2 m per second, they would arrive 15–30 years ahead of the comet at the next perihelion passage. The ﬁ ve photographic meteors discussed by Ohtsuka arrived 19–30 years earlier. He cited observations of comet IRAS-Araki-Alcock by the Arecibo radio telescope (Puerto Rico) that estimated the ejection velocity of particles from the nucleus as 2.7 m per second.48 The orbits labeled “1968a,” “1968b,” and “1968c” are from Terentjeva (1968). The orbit labeled “1991” is from Ohtsuka (1991).

w W (2000) i q e a 1968a 192 49 76 1.00 1.06 −16.67 1968b 181 46 66 1.01 1.10 −10.10 1968c 177 38 58 1.01 0.59 2.55 1991 193.0 50.3 75.3 0.998 1.062 −16.10

Daytime May Piscids

This daylight stream seems to have fi rst been detected by observers at the Jodrell Bank Experimental Station (Lower Withington, Cheshire, England), as J. A. Clegg, V. A. Hughes, and A. C. B. Lovell listed a radiant of a = 7°, d = +20° that was detected on 1947 May 4. Although the radar was operated during May 1–30, no additional activity from this stream was noted.49 The Jodrell Bank equipment was operated again during 1948 May–August. A. Aspinall, Clegg, and Lovell (1949) noted two branches of the “Piscids” were active during May. The western-most branch was fi rst noticed on May 1 from a radiant at a = 19°, d = +20° and was last detected on May 20 at a = 34°, d = +25°. The eastern- most branch was fi rst noticed on May 2 at a = 30°, d = +20° and was last detected on May 16 at a = 36°, d = +21°. The average hourly rate was 20, “but at times the Daytime May Piscids 101 shower becomes much more active.” The authors added, “Diffuse areas of activity precede and follow the radiant, and at times well-de fi ned secondary radiants spring up to the east and west of the main centre.”50 G. S. Hawkins and M. Almond (1952) detected a radiant during 1951 that they named the “Upsilon Piscids.” The radiant was located at a = 15°, d = +28° on May 12 (l = 50.9°) and a = 17°, d = +26° on May 13 (l = 51.9°), which the authors noted “may correspond to the Piscid streams previously observed in 1947 and 1948, but there is a difference of 10° in Right Ascension of the radiant position which makes the identifi cation uncertain.” They described it as a “weak stream of diffuse radiant structure.” The hourly rate was 12–16.51 The Jodrell Bank equipment detected a meteor shower on 1955 May 12 ( l = 50.8°). T. W. Davidson (1956) found 33 meteors which indicated a radiant at a = 12°, d = +24°, that was 3° in diameter. The hourly rate was given as 8. The radiant was called the “Upsilon Piscids,” and Davidson noted it was near a radiant detected at Jodrell Bank in 1951.52 The next radar survey to detect this stream was conducted by B. L. Kashcheyev and V. N. Lebedinets (Kharkov Polytechnical Institute, Ukraine) in 1960. During the period of May 4–27, 17 meteors were observed. The date of the nodal passage was given as May 12 ( l = 52°), at which time the radiant was at a = 17°, d = +19°. 31 The 1968–1969 session of the Radio Meteor Project detected a stream that Z. Sekanina (1976) labeled the “May Piscids.” Sekanina noted that activity was detected during May 7–9, from an average radiant of a = 11.9°, d = +19.0°. The date of the nodal passage was given as May 8.4 ( l = 47.3°) and the geocentric velocity was 34.1 km/s. 32 The equipment was shut down during May 10–18, so that any extension in the duration of the shower would have been missed. The Canadian Meteor Orbit Radar (CMOR) did not detect activity in Pisces, but did detect a meteor stream that was labeled the “Northern Daytime Omega Cetids,” which seems to be the same stream detected in the surveys noted above. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 2,279 meteor orbits from this stream, noting a duration of April 6 (l = 16°)–May 23 ( l = 61°). Maximum occurred on May 9/10 ( l = 49°) from a radiant at a = 11.8°, d = +18.9°. The geocentric velocity was 36.2 km/s.53 Three orbits have been determined from radar survey data. The orbit labeled “1960” was published by Kashcheyev and Lebedinets (1967). The orbit labeled “1968–1969” is that published by Sekanina (1976). The orbit labeled “2002–2008” was published by Brown et al. (2010).

w W (2000) i q e a 1960 32 53 30 0.11 0.93 1.64 1968–1969 35.9 48.0 29.1 0.147 0.896 1.41 2002–2008 32.13 49.0 34.8 0.1167 0.919 1.44 102 6 May Meteor Showers

1. H. A. Newton, American Journal of Science and Arts (Series 2) , 36 (1863 Jul.), pp. 148–9. 2. G. L. Tupman, Monthly Notices of the Royal Astronomical Society , 33 (1873), p. 301. 3. G. L. Tupman, Report of the Annual Meeting of the British Association for the Advancement of Science , 44 (1875), p. 313. 4. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 43 (1883 Jan.), pp. 111–14. 5. A. S. Herschel, Report of the Annual Meeting of the British Association for the Advancement of Science , 45 (1876), pp. 232, 235. 6. A. S. Herschel, Monthly Notices of the Royal Astronomical Society , 38 (1878 May), p. 379. 7. H. Corder, The Observatory , 2 (1878 Jul.), p. 103. 8. H. Corder, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), pp. 132, 134. 9. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 44 (1884 Apr.), pp. 298–9. 10. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 46 (1886 May), pp. 396–8. 11. H. Corder, Memoirs of the British Astronomical Association , 3 (1895), p. 20. 12. W. H. Milligan, Memoirs of the British Astronomical Association , 4 (1896), p. 8. 13. H. Corder, Memoirs of the British Astronomical Association , 5 (1897), p. 9. 14. T. W. Backhouse, Memoirs of the British Astronomical Association , 6 (1898), p. 44. 15. A. S. Herschel, Memoirs of the British Astronomical Association , 9 (1901), p. 16. 16. P. M. Ryves, Memoirs of the British Astronomical Association , 12 (1904), p. 11. 17. G. M. Knight, Memoirs of the British Astronomical Association , 13 (1905), p. 12. 18. C. P. Olivier and H. D. Curtis, Publications of the Astronomical Society of the Paciﬁ c , 22 (1910), pp. 141–2. 19. C. P. Olivier, A stronomical Journal , 27 (1912), pp. 129–30. 20. C. P. Olivier, Transactions of the American Philosophical Society (New Series) , 22 (1911). 21. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 90 (1929 Nov.), p. 158. 22. R. A. McIntosh and M. Geddes, Monthly Notices of the Royal Astronomical Society , 95 (1935 May), p. 604. 23. J. A. Clegg, V. A. Hughes, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society, 107 (1947), pp. 373–7. 24. A. Hajduk, Bulletin of the Astronomical Institutes of Czechoslovakia , 24 (1973), p. 10. 25. A. Hajduk, Bulletin of the Astronomical Institutes of Czechoslovakia , 24 (1973), pp. 9–11. 26. D. K. Yeomans and T. Kiang, Monthly Notices of the Royal Astronomical Society , 197 (1981), pp. 633–46. 27. B. A. McIntosh and A. Hajduk, Monthly Notices of the Royal Astronomical Society , 205 (1983), p. 931. 28. A. Dubietis, WGN, Journal of the International Meteor Organization, 31 (2003 May), pp. 46–7. 29. Z. Sekanina, Icarus , 13 (1970), pp. 476–7. 30. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 31. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 188. 32. Z. Sekanina, Icarus , 27 (1976), pp. 277, 293. 33. http://www.imonet.org/radiants/ 34. N1964, pp. 226–8, 245. 35. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226, 228. 36. B. L. Kashcheyev and V. N. Lebedinets, SCoA , 11 (1967), p. 188. 37. A. Aspinall and G. S. Hawkins, Monthly Notices of the Royal Astronomical Society, 111 (1951), pp. 20–1. 38. M. Almond, Monthly Notices of the Royal Astronomical Society, 111 (1951), p. 38. 39. M. Almond, K. Bullough, and G. S. Hawkins , Jodrell Bank Annals , 1 (1952 Dec.), p. 16. 40. B1954, p. 79. 41. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226–8, 232, 237. 42. Z. Sekanina, Icarus , 18 (1973), pp. 256, 259. 43. B. G. Marsden, International Astronomical Union Circular , No. 3796 (1983 May 4). Daytime May Piscids 103

44. J. D. Drummond, International Astronomical Union Circular , No. 3801 (1983 May 9). 45. A. F. Cook, P. M. Millman, and S. Clifton, International Astronomical Union Circular , No. 3811 (1983 May 18). 46. J. D. Drummond, International Astronomical Union Circular , No. 3817 (1983 Jun. 1). 47. A. K. Terentjeva, Physics and Dynamics of Meteors. International Astronomical Union Symposium no. 33 held at Tatranska Lomnica, Czechoslovakia, 1967 Sep. 4–9. Edited by L. Kresák and P. M. Millman, Dordrecht, D. Reidel, p. 411. 48. K. Ohtsuka, Origin and Evolution of Interplanetary Dust, Astrophysics and Space Science Library, 173 (1991), pp. 315–18. 49. J. A. Clegg, V. A. Hughes, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society, 107 (1947), p. 374. 50. A. Aspinall, J. A. Clegg, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society, 109 (1949), p. 353. 51. G. S. Hawkins and M. Almond, Jodrell Bank Annals , 1 (1952 Apr.), p. 4, 9. 52. T. W. Davidson, Jodrell Bank Annals , 1 (1956 Dec.), pp. 121, 125. 53. P. Brown, D. K. Wong, R. J. Weryk, and P. Wiegert, Icarus , 207 (2010), pp. 70, 72. Chapter 7

June Meteor Showers

June Aquilids

The strongest data supporting this stream’s existence comes from three radar studies conducted during the 1960s. During 1961 June 13–19, C. S. Nilsson (1964) used the equipment at the University of Adelaide (South Australia, Australia) and detected four meteors from a = 293.9°, d = −8.4°.1 A second radar survey was conducted at Adelaide by G. Gartrell and W. G. Elford (1975) during 1969 June. Thirteen meteors were detected from an average radiant at a = 289°, d = −6° centered on June 11.2 Finally, during 1969 June 2 to July 2, Z. Sekanina said the Radio Meteor Project at Havana, Illinois (USA) detected 35 meteors. At the time of its nodal crossing on June 17.5 (l = 85.8°), the radiant was at a = 297.1°, d = −7.1°. There is no trace of this radiant in M. Buhagiar’s list of 488 radiants that he compiled from his personal observations made during 1969–1980 3 ; however, visual observations have been made. During 1988, J. M. Trigo-Rodríguez and V. Soldevilla, members of the Spanish Meteor Society, observed on the night of June 11/12. From a plot of four meteors, they determined the radiant as a = 282°, d = −5°. During 1990, Trigo-Rodríguez received observations from a group of observers on the Canary Islands. They were observing on the night of 1990 June 17 and saw 122 meteors, of which 15 % were “Lambda Aquilids.” The ZHR was 3–4 and a plot of 19 meteors indicated the radiant was at a = 295°, d = −2°. Slight activity was also reported by these observers on June 24.4 The orbit labeled “1961” was published by Nilsson (1964). The orbit labeled “1969a” was determined by Gartrell and Elford (1975). The orbit labeled “1969b” was published by Sekanina (1976).

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 105 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_7, © Springer Science+Business Media New York 2014 106 7 June Meteor Showers

w W (2000) i q e a 1961 328.9 85.0 40.1 0.113 0.93 1.61 1969a 324 81 39.5 0.15 0.90 1.85 1969b 329.5 86.5 39.3 0.114 0.916 1.35

Gartrell and Elford suggested the stream might be related to comet C/1618 W1, the orbit of which follows:

w W (2000) i q e a C/1618 W1 287.44 81.00 37.20 0.3895 1.0 ϱ

Daytime Arietids

Duration: May 22 to July 2 (l = 61–100°) Maximum: June 8 (l = 76.8°) Radiant: a = 45°, d = +24° ZHR: High

Radiant Drift: a = +0.5°, d = +0.3° V G : 39 km/s

This daylight meteor shower was discovered in 1947, when operators of the radio equipment at Jodrell Bank (England) detected activity during May 30 to June 17. Observers visually observed the meteors by monitoring a cathode-ray tube display. Although the radiant was not accurately determined, J. A. Clegg, V. A. Hughes, and A. C. B. Lovell (1947) noted a radiant within the range of a = 52–62°, d = +15°, with an hourly rate of 20–40.5 A. Aspinall, Clegg, and Lovell (1949) noted that the Daytime Arietids and the Daytime Zeta Perseids “were not delineated in the 1947 observations. In retrospect, however, it is now evident that both these radiants existed in 1947, but the records were wrongly interpreted as indicating a radiant at a = 57°, d = +15°.” The 1948 survey at Jodrell Bank used a photographic method to record the meteors. The Arietids were detected during 17 days, with the radiant moving from a = 27°, d = +20° on May 25 to a = 44°, d = +22° on June 11. The Arietids peaked on June 4, reaching an hourly rate of 60.6 The Arietids have been detected in every major radar study since 1947. The orbit was ﬁ rst determined by M. Almond during 1951. Although the average orbital inclination was found to be 18°, Almond used the “smoothed radiant positions for the ﬁ rst and last dates of observations” and found the stream’s orbit to begin with an inclination of 3° and end with a value of 34°, thus “the line of apsides swings gradually forward, and the main centre of the stream rises farther away from the ecliptic day by day.”7 The issue with the stream’s inclination has remained ever since 1951, with radar studies in Australia, the United States, and the Ukraine variously revealing values of 19–38°; however, an Australian radar survey conducted during 1969 shed some light on this issue. Daytime Arietids 107

G. Gartrell and W. G. Elford (1975) detected six associations during mid-June 1969 that exhibited radiants and velocities very close to those accepted for the Arietids. The problem that existed was that the orbital inclinations of these streams varied from 2.4° to 65.3°. They pointed out that the inclination spread noted by other workers was de fi nitely con fi rmed; however, “no evidence of the progressive increase in inclination with passage through the stream…was found in this survey.”8 This indicated that numerous ringlets of material were the reason leading to the unusual variation with the Arietid stream’s orbital inclination. The ringlets of material are also probably responsible for the large reported variations in the daily motion of the radiant. Aspinall and G. S. Hawkins (1951) produced a smoothed radiant ephemeris, based on Jodrell Bank data, that indicated a daily motion of +0.74° in a and +0.92° in d . 9 Using more precise observations obtained at Jodrell Bank during 1950–1953, K. Bullough (1954) determined the radiant’s daily motion as +0.48° in a and +0.30° in d . 10 Still another determination from Jodrell Bank data, this time covering the period 1950–1955, was published by T. W. Davidson (1956). He found the radiant’s daily motion to be +0.47° in a and +0.39° in d . 11 The data from a radar survey conducted in the Ukraine during 1960, was analyzed by B. L. Kashcheyev and V. N. Lebedinets (1967). They determined the daily motion as +0.7° in a and +0.1° in d . 12 From the numerous Jodrell Bank studies (many of which have been cited above) the diameter of the radiant appears to be about 3°, while the maximum hourly rate ranges from 54 to 76. Z. Sekanina published two papers during the 1970s giving details of the two sessions of the Radio Meteor Project. During the 1961–1965 session, Sekanina (1973) determined the duration as May 30 to June 21. The date of the nodal passage was given as June 9.3 ( l = 78.0°), at which time the radiant was at a = 42.9°, d = +25.7°. The geocentric velocity was determined as 34.7 km/s.13 During the 1968–1969 session, Sekanina determined the duration as May 22 to July 2. The date of the nodal passage was then given as June 8.1 ( l = 76.9°), at which time the average radiant position was determined as a = 39.1°, d = +23.8° and the geocentric velocity was 39.5 km/s. 14 Both of Sekanina’s papers noted that the minor planet 1566 Icarus had similar orbital characteristics to the Arietids. Various researchers have arrived at some interesting conclusions concerning links between this stream and other solar system bodies. In 1951, while obtaining the fi rst determination of this stream’s orbit, Almond concluded that another shower should be encountered as Earth crossed the stream’s orbital plane on July 28. The estimated radiant position was a = 336°, d = −11°, which falls within 15° of the position of the Southern Delta Aquariid meteor stream. After examining both stream orbits, Almond concluded that, although the orbits “are now different, it seems probable that they may have had a common origin in the past.” 15 Interestingly, D. K. Yeomans (1991) computed orbital solutions for several near-Earth minor planets to see if any showed signs of nongravitational effects due to outgassing. He said the orbit of 1566 Icarus was greatly improved by the nongravitational effects, indicating it was a possible comet candidate. 16 D. I. Steel (1992) suggested that minor planet 1991 RC (now known as 5786 Talos) was another associated member of the Arietids stream and that it and Icarus may be the remains of a larger comet.17 108 7 June Meteor Showers

The most recent radar survey to detect the Arietids was the Canadian Meteor Orbit Radar (CMOR). They determined 3592 meteor orbits for this stream during 2002–2008. Maximum occurred on June 12 ( l = 81°) from a radiant at a = 45.7°, d = +25°. The duration was revealed as May 23 to July 1 (l = 62°–99°), and the geocentric velocity was 39.1 km/s. The daily motion of the radiant was given as +0.86° in a and +0.18° in d .18 The road to ﬁ nding a parent to the Daytime Arietids started when B. G. Marsden (2002) noted that four comets discovered by the SOHO coronograph during 1999 and 2000 moved in orbits that were quite close to one another. 19 This group has become known as the “Marsden Comet Group.” A few weeks later, D. A. J. Seargent remarked on the similarity between the orbits of this group and the orbit of the Daytime Arietid meteor stream, to which Marsden added that the orbits “are also similar to those of both comet 96P/Machholz 1 and the Quadrantid meteor stream.”20 K. Ohtsuka, S. Nakano, and M. Yoshikawa (2003) examined the association of the Daytime Arietids, comet 96P, the Marsden Comet Group and the Kracht Comet Group (the members of this latter group were also discovered by the SOHO coronograph and the members being recognized by R. Kracht). They suggested that the Marsden and Kracht comet groups separated from comet 96P about 4,000 years ago.21 Despite being a daytime meteor shower, meteors have been detected by visual and video means. During 1971 June 6/7, K. Simmons (Florida, USA) estimated combined rates of the Daytime Arietids and Daytime Zeta Perseids [later in chapter ] reached 1–2 meteors per hour.22 During 1 h on the morning of 1973 June 2, J. West (Bryan, Texas, USA) observed four Arietids.23 Y. Fujiwara, M. Ueda, M. Sugimoto, T. Sagayama, S. Abe (2004) reported that multi-station video observations conducted since 1994 had captured 3 Daytime Arietids, one in 1999 and two in 2003. These indicated the average radiant was at a = 43.2°, d = +24.9°, while the geocentric velocity was 41.0 km/s.24 Numerous orbits have been determined over the years, some using a very small sample of less than 10 meteors. Below are the orbits based on large samples. The “1960” orbit is that of Kashcheyev and Lebedinets and is based on 380 meteors. The “1961–1965” orbit is that published by Sekanina in 1973 and is based on 41 meteors. The “1968–1969” orbit was published by Sekanina in 1976 and is based on 48 meteors. The “1969” orbit was published by Gartrell and Elford in 1975 and is based on 32 meteors. The “1999–2003” orbit was published by Fujiwara et al. (2004). The “2002–2008” orbit was from CMOR and is based on 3592 meteor orbits.

w W (2000) i q e a 1960 29.9 77.3 18.7 0.10 0.94 1.67 1961–1965 29.5 78.7 27.9 0.094 0.946 1.75 1968–1969 25.9 77.6 25.0 0.085 0.938 1.38 1969 28 82 17.4 0.08 0.96 2.78 1999–2003 27.02 77.84 31.96 0.073 0.970 2.43 2002–2008 25.57 81.0 28.0 0.0692 0.961 1.75 June Boötids (“Pons-Winneckids”) 109

There have been several associations suggested for this stream. The “1566” orbit is the minor planet Icarus. The “5786” orbit is the minor planet Talos. The orbit labeled “MCG” represents the mean orbits of 34 comets within the Marsden Comet Group.

w W (2000) i q e a 1566 31.11 88.26 22.92 0.187 0.827 1.08 5786 8.31 161.34 23.24 0.187 0.827 1.08 MCG 23.57 80.70 26.18 0.0484 1.0 ¥

June Boötids (“Pons-Winneckids”)

Duration: June 23 to July 5 (l = 92–103°) Maximum: June 27 (l = 95.7°) Radiant: a = 223°, d = +48° ZHR: Variable

Radiant Drift: a = UNK, d = UNK V G : UNK km/s

The entrance of this stream into the lists of active meteor showers occurred as a result of intense activity that was observed on the night of 1916 June 28 by people in England. After a cloudy day, the skies of England began clearing shortly before sunset. W. F. Denning went outside at 10:25 p.m. and quickly noted that a meteor shower was in progress. “Large meteors came in quick succession from a radiant in the region between Boötes and Draco,” he wrote. Denning described the meteors as “moderately slow, white with yellowish trains, and paths rather short in the majority of cases. Several of the meteors burst or acquired a great intensifi cation of light near the termination of their fl ights, and gave fl ashes like distant lightning.” Denning enlisted the help of a friend in observing the spectacle, while he plotted as many meteors as possible. Observations ended after 1:15 a.m. when clouds again moved in. Denning concluded that the greatest part of the display occurred prior to midnight. He also stated that the exact location of the radiant was impossible to pinpoint. As he projected his plotted paths backward he noted the “directions were from a wide region or area of about 12–15° diameter.” What Denning considered to be the main radiant was given the position of a = 231°, d = +54°. Though clouds prevented observations on June 29, Denning was able to observe between 10:15 and 11:30 p.m. on the 30th, but only one meteor was noted that could have been from the shower of the 28th. This meteor was also detected and plotted by F. Wilson (Totteridge, England). From both plots, Denning was able to determine the radiant to have been at a = 223°, d = +41°. Shortly after observing this strong shower, Denning wondered if its sudden appearance might be attributable to a comet. After searching through lists of cometary orbits, he concluded that periodic comet 7P/Pons-Winnecke was probably responsible. “The radiant was placed in the correct region and the date agreed. Moreover, the comet passed through perihelion on September 1 last year.”25 110 7 June Meteor Showers

C. P. Olivier, director of the American Meteor Society, received several charts during the latter half of 1916 which clearly indicated that, although the great shower of June 28 had been missed in the United States, observers had independently noted activity from a similar area of the sky during May, June, and July— J. Koep and P. Trudelle (both of Chippewa Falls, Wisconsin, USA) observed these meteors during the period of May 19 to June 5, while R. Lambert (Newark, New Jersey, USA) detected a radiant of a = 206.7°, d = +61.2° on July 4.26 Olivier tabulated the known 1916 observed radiants and computed both parabolic and elliptical orbits for each. He upheld Denning’s belief of a relationship with Pons-Winnecke and added that the long-term activity seen in the United States was from the same stream as the outburst. A later investigation into the link between this meteor shower and Pons- Winnecke was published in 1932. F. W. Smith extended Olivier’s mathematical work to check the similarity between a radiant ephemeris based on the observations and an ephemeris based on the orbit of Pons-Winnecke. Smith took a typical radiant from the Koep and Trudelle data and noted that it would drift toward the general position of the June 28 activity; however, the link between the orbits of the observed activity and that of Pons-Winnecke was far from perfect. Smith suggested, “the meteors had been separated from the actual orbit of the comet by dispersive forces, which would be expected in this case because of the direct motion of the comet, its short period, and the low inclination of its orbit.”27 Indeed, the forces being exerted upon the comet by Jupiter were great. In fact, from the beginning of the twentieth century until about 1940, the comet had been locked into a nearly perfect 2:1 resonance with Jupiter. The main effect of this resonance was the rapid increase of Pons-Winnecke’s perihelion distance. From the time of the comet’s discovery in 1819, until shortly after the 1869 perihelion passage, the comet’s perihelion distance remained about 0.2 AU inside Earth’s orbit. During the next 46 years the perihelion distance quickly moved away from the sun, and in 1915 it was only 0.04 AU inside of Earth’s orbit. By 1921, the perihelion was 0.03 AU outside of Earth’s orbit, and by 1964 it was located 0.22 AU outside of Earth’s orbit. The orbit of this comet has remained in a fairly stable state since 1964. Searches for evidence of this meteor shower prior to the 1916 outburst have found no convincing observations. The comet made several close approaches to Jupiter prior to the 1916 outburst, passing at a distance of 0.87 AU in 1870, 0.43 AU in 1882, 0.45 AU in 1894, and 0.42 AU in 1906. Through this period, the perihelion distance was increasing and the comet’s orbit was drawing closer to that of Earth. Following 1916, two notable, though weaker, appearances of this shower occurred during the next two perihelion passages of comet Pons-Winnecke. During 1921, observations in the United States and England revealed predominantly weak activity, with only R. M. Dole (Wilmington, North Carolina, USA) and Denning being able to secure enough plotted meteors to reveal radiants. On June 29.17, Dole plotted seven meteors from a = 213.6°, d = +47.2°, while on June 30.10, he plotted eight meteors from a = 213.2°, d = +47.0°.28 On June 28, Denning plotted seven June Boötids (“Pons-Winneckids”) 111 meteors from a = 228°, d = +58°.29 But, while these observers were barely collecting enough data for radiant determinations, K. Nakamura (Kyoto, Japan) noted increased numbers in early July.30 Nakamura searched for meteors of Pons-Winnecke on several occasions during late June and early July in weather that varied from clear to mostly cloudy skies. Beginning his observations on June 25, Nakamura observed his fi rst meteors from this shower on the 26th. Although the number of meteors from this shower increased by the 27th and 28th, the greatest rates were said to have occurred on July 3, when 153 meteors were seen in 35 min. Cloudy skies were present on the 4th, but observations on the 5th revealed meteors still falling at a rate of 91 per 41 min at one point. During the period of June 26 to July 11, Nakamura was able to plot enough meteors to obtain nine daily positions, with the radiant moving slowly southeastward. On June 28, the radiant was determined to have been at a = 212.5°, d = +49°, while the position on the night of maximum activity levels was a = 212°, d = +47°. Nakamura’s radiants are very similar to those determined by Dole. Nakamura had been described as possessing “very sensitive eyes,” and his daily estimations of the mean magnitude of these meteors showed the shower began at 5.4, slowly brightened to 3.5 on July 1, then varied between 4.5 and 5.0 during July 3–11. Responding to Yamamoto’s letter, Denning showed some doubt about the sensitivity of Nakamura’s eyes unless “Nakamura is able to discern meteors of 6th, 7th and 8th magnitudes.” 31 Despite Denning”s views, interesting observations were made during the next appearance of this shower. During late June and early July 1927, several members of the meteor section of the Russian society Mïrovédénïé, observing at Tashkent (Uzbekistan), noted increased activity, which reached hourly rates of 500 on June 27.32 According to their director, V. A. Malzev, “about 90 per cent of the meteors were fainter than the 5th magnitude, which leads to the conclusion that our observations are con fi rming those made in Japan in Kyoto in 1921.” According to N. N. Sytinskaja, the observations revealed the peak to have fallen on June 27.21, while the radiant’s daily motion was noted to be +1.0° in a and −0.3° in d . 33 Although the number of meteors seen in the United States was much lower than that in Russia, Dole (East Lansing, Michigan, USA) detected 145 meteors during June 26–30. The radiant moved from a = 212.5°, d = +55° on the 27th to a = 218°, d = +59.5° by the 30th.34 He remarked that “many brilliant individual meteors” were seen, but, overall, the display was “very faint.” Curiously, the radiant motion indicated by Dole’s observations indicate a northeastward motion, while the Russian data shows a southeastward motion. Similarly, Nakamura’s 1921 observations also revealed a southeastward motion, while Franklin Smith’s calculations revealed a northeastward motion for the radiant. An explanation for this discrepancy among observers is not easy to explain but could be linked to the apparent diffuse nature of the radiant. The June Boötids remained active for several decades, but only produced weak activity. E. F. Turco (1968) wrote that observations had revealed recent rates of 3–5 per hour, “with meteors being on the fairly dim side.” 35 In 1981, D. Swann (Dallas, Texas, USA) wrote that on six occasions during the period 1964–1971, he observed rates amounting to 1–2 meteors per hour from this stream. Concerning the individual 112 7 June Meteor Showers meteors, Swann noted that he had “never noticed any trains, even though I have seen several bright shower members.” He added that, despite the low number of meteors seen, he had seen several fi reballs. 36 Some observers managed to determine the meteor shower’s radiant. On 1964 June 28.6, D. Conger (Elizabeth, West Virginia, USA) observed fi ve meteors from a = 226°, d = +59°, 37 while on 1970 June 28, Pennsylvania observers G. Becker (Allentown) and M. T. Adams (Warrington) determined radiants of a = 223°, d = +59° and a = 224°, d = +58°, respectively. 38 The Radar Meteor Project operated using radio equipment in Havana, Illinois (USA) during the periods of 1961–1965 and 1968–1969. Z. Sekanina analyzed the data acquired during both sessions and found meteor streams with orbits very similar to that of the June Boötids. During the fi rst session, Sekanina (1973) found a stream that he called the “July Draconids.” This stream was based on only fi ve meteors and was active on July 1–2 from a radiant at a = 239.5°, d = +68.8°. The discrepancy of the radar radiant from that determined visually was due to the radar orbit possessing an orbital inclination of 30.3°.39 It has been shown that the June Boötids possess a fairly diffuse radiant due to the rapid alterations of the parent comet’s orbit, so this small sample may represent a random collection of high- inclination members of this stream. It should be noted that during the comet’s transition from a perihelion distance lying within Earth’s orbit to a perihelion outside of Earth’s orbit, perturbations by Jupiter also acted on the orbital inclination. When discovered in 1819, the inclination was only 10°, while the present orbit is at 22°. Since the June Boötids displayed an obvious diffuse radiant during 1916, 1921, and 1927, which appeared due to an orbital inclination spread of about 8°, such a diffusion would have become enhanced by the close approaches with Jupiter that followed. Thus, Sekanina’s orbit seems based on a collection of meteors orbiting near the edges of the main orbit of the June Boötid stream. Sekanina (1976) found two meteor streams in the second session of the Radio Meteor Project. The fi rst stream was referred to as the “Alpha Draconids” and was active during June 2 to July 19. It was defi ned by 54 meteors and the average radiant was at a = 207.4°, d = +64.0°. The orbit crossed the ecliptic on June 22.40 This orbit closely matches that determined for the visually observed radiants detected from 1921 to the present, as well as the 1927 orbit of Pons-Winnecke. The second stream was called the “Bootids-Draconids.” The duration extended from July 1 to 4, and at the time of its nodal crossing on July 2.1 the average radiant was at a = 233.7°, d = +52.2°. This orbit closely matches that determined by Olivier from the English observations of 1916 June 28. On 1998 June 27, B. G. Marsden published brief details of several observations made in Japan around June 27.6. In particular, K. Usuki (Aizu, Fukushima, Japan) observed 40–50 meteors per hour despite 80–90 % cloud cover, T. Hamane (Misato Astronomical Observatory) reported “many bright meteors with trains,” and Y. Kushida (Yatsugatake, Yamanashi, Japan) detected “numerous meteors” using VHF radio during June 27.58–27.67.41 On July 4, these observations were announced as an outburst from the June Boötid meteor shower, when P. G. Brown and W. K. Hocking (University of Western Ontario) said the Skiymet meteor radar in Saskatoon, Saskatchewan revealed a “strong increase in radar rates centered on June Boötids (“Pons-Winneckids”) 113

June 27.60±0.04 UT.” They revealed a “quite diffuse” radiant centered at a = 228°, d = +54°, as well as an additional radiant centered at a = 219°, d = +61°.42 An analysis by J. Rendtel, R. Arlt, and V. Velkov (1998) revealed a maximum ZHR near 100 during l = 95.7–96.0° from an average radiant at a = 230°, d = +47°. The average population index during the outburst was r = 2.22.43 Listed below are the elliptical orbits computed by Olivier in 1916. They reveal a fairly large difference between the orbits of the May–June activity (designated below as “1916a”) and the June 28 activity (designated “1916b”). These use the semimajor axis of Pons-Winnecke for the 1915 apparition for calculation purposes. The orbit labeled “1961–1965” is for the “July Draconids” and is from Sekanina (1973). The orbit labeled “1968–1969a” is for the “Alpha Draconids” and is from Sekanina (1976). The orbit labeled “1968–1969b” is for the “Bootids-Draconids” and is from Sekanina (1976).

w W (2000) i q e a 1916a 216.9 68.6 17.8 0.927 0.716 3.26 1916b 188.7 97.6 18.7 1.009 0.690 3.26 1961–1965 171.2 99.7 30.3 1.009 0.616 2.63 1968–1969a 168.0 91.2 21.7 1.000 0.596 2.48 1968–1969b 184.0 100.5 21.3 1.014 0.596 2.51

The orbits listed below are of comet 7P/Pons-Winnecke, with “1915” representing the orbit in that year and the “1927” representing the orbit in that year.

w W (2000) i q e a 1915 172.42 100.52 18.30 0.9706 0.7023 3.26 1927 170.40 99.14 18.94 1.0392 0.6857 3.31

Using an orbit similar to “1916b” above, K. Fox (1986) determined the stream orbit for 1,000 years into the past and future.44 The following were determined for the June Boötids:

w W (2000) i q e a 950 179.6 98.3 18.0 1.06 0.68 3.31 2950 182.3 98.6 17.8 0.98 0.70 3.25 114 7 June Meteor Showers

Interestingly, this study reveals the present June Boötid stream to be in a fairly stable orbit, even though the observations fail to bear this out.

Corvids

C. Hoffmeister (1948) was on a meteor expedition to South-West Africa (now Namibia) during 1937–1938. He observed an unexpected meteor shower radiating from the constellation Corvus during 1937 June 25 to July 2. No trace of this shower was seen in the years that followed, nor was there a trace in dozens of radiant lists published during the six or so decades prior to 1937. Hoffmeister said the earliest activity came on June 25, just 2 days after the full moon. He gave hourly rates of 4.1 on June 25.7, 13.1 on June 26.8, 9.5 on June 27.8, 7.8 on June 28.8, 6.0 on June 29.8, 1.7 on June 30.8, 0.5 on July 1.8, and 2.3 on July 2.8. Hoffmeister concluded that maximum came on June 27.0 ( l = 94.9°). The radiant was determined as a = 191.6°, d = −19.2° on June 28. It was described as diffuse, with a diameter of nearly 15°. Hoffmeister computed two orbits based on semimajor axes of 2.5 and 3.0 AU and noted “a rather striking resemblance to the orbit of Comet Tempel 3-Swift, except for argument of perihelion....”45 [ The comet “Tempel 3-Swift” is now known as “11P/Tempel-Swift-LINEAR. ”] In the 1988 edition of this book, it was noted that the minor planet 1979 VA might be associated with this meteor shower. During 1992, this minor planet was found to be identical to comet Wilson-Harrington, which was discovered on 1949 November 19. Although it was only followed until November 25, it was suspected to be moving in a short-period orbit.46 It is now known as periodic comet 107P/ Wilson-Harrington, and an association still seems possible. The association with periodic comet 11P/Tempel-Swift-LINEAR was investigated by G. V. Zhukov, M. G. Ishmukhametova, E. D. Kondrat’eva, and V. S. Usanin (2011). They integrated the comet’s orbit from 1600 to 1940 and modeled the ejection of particles in various directions and at different ejection rates from 1808 to 1940. For the comet, they identi ﬁ ed nine close approaches to Jupiter, the distances of which ranged from 0.34 to 0.61 AU. In the course of the 340-year period, the w rotated 169° and the W rotated 157°. At no time during this period did the orbit of the comet come close to matching the Corvid orbits calculated by Hoffmeister (see below). For the ejected particles, the authors assumed ejection speeds of +300 and −300 km/s with respect to the comet, to represent the extremes. Each cloud of particles made three close passes by Jupiter. For one cloud, the distances of these passes were 0.65–0.77 AU, with the w rotating by 62° and the W rotating by 64°. For the other cloud, the distances of these passes were 0.65– 1.99 AU, with the w rotating by 7.5° and the W rotating by 6.6°. Neither of these particle clouds were close to Hoffmeister’s orbits. The authors added that the theoretical radiant of comet Tempel-Swift-LINEAR around the time of the Corvids observation should have been a = 242.55°, d = +39.6°. Zhukov et al. concluded, “The possible connection between the comet 11P/Tempel-Swift-LINEAR and the meteor shower with the radiant in Corvus was not con ﬁ rmed.”47 Corvids 115

P. Jenniskens (2006) suggested that the minor planet 2004 HW, which was discovered by the Siding Spring Survey (Australia), is associated with this meteor shower. He said it appears to be moving in an orbit that gives it a 12 % chance of being an extinct comet nucleus.48 There is an interesting tie between the Corvids and the lunar crater Giordano Bruno. For a period of almost three decades, it was believed that the chronicles of Gervase of Canterbury recorded the actual impact that created this crater on 1178 June 25. The account is as follows: This year, on Sunday before the Nativity of St. John the Baptist, after the setting of the sun and when the Moon was fi rst becoming visible, a wonderful sign was seen by fi ve or more men as they faced the Moon. In fact, it was a bright new moon, and as usual in that phase, the horns were tilted towards the east: and, behold, suddenly the upper horn split in two. From the middle of this division leapt a fl aming torch, sparks, and embers farther down.49 J. B. Hartung (1976) was the fi rst person to suggest a link between the Canterbury account and the formation of Giordano Bruno, adding that it represented the creation of a crater >10 km across near the lunar coordinates of latitude 45° north, longitude 90° east. Hartung said the bright rayed crater Giordano Bruno was 20 km across and located at latitude 36° north, longitude 103° east.50 There were few challenges to this theory in the years that followed, and it was even popularized by C. Sagan in his TV mini-series Cosmos during 1980. Hartung (1991) introduced a new theory suggesting the ejecta from the lunar crater Giordano Bruno (GB) might have been seen as the Corvid meteor shower in 1937. He even predicted a return of the shower in 2003 or 2006.51 A. W. Harris (1992) disputed this idea of a link between the ejecta and the Corvids, noting, “that the dispersion velocity within a clump of ejecta leaving the surface of the moon would have to be less than a few cm/sec in order for the clump to retain suf fi cient compactness to produce a shower in only one year, and not at the same time in adjacent years as well.”52 No activity was reported from the Corvid radiant during 2003 or 2006. The suggested observation of the formation of Giordano Bruno took a series of blows during the 2000s and 2010s, when several astronomers published a series of papers stating that this crater was not formed in historical times. Perhaps the fi rst to suggest there was a problem with the link was P. Withers (2001), who noted that if this had been an impact, a “week-long meteor storm potentially comparable to the peak of the 1966 Leonids storm” should have occurred, but no observations from 1,178 support that type of activity. 53 Based on data accumulated by the lunar probes SELENE and the Lunar Reconnaissance Orbiter, astronomers now believe Giordano Bruno was probably created between 1 and 10 million years ago. So, the possible link to the Corvids is highly unlikely. It is interesting to note that the seismometers left on the Moon by the Apollo astronauts detected a strong “meteoroid storm” during 1975 June 20–30. The diameter of the cloud was given as 0.1 AU, and it is believed to have originated from a meteor radiant in the Southern Hemisphere.54 Although this activity has been linked to the Taurid complex, the duration is certainly similar to the Corvids. 116 7 June Meteor Showers

The orbits labeled “I” and “II” are from Hoffmeister (1948). The orbit labeled “11P (1938)” is periodic comet 11P/Tempel-Swift-LINEAR. The orbit labeled “107P (1936)” is periodic comet 107P/Wilson-Harrington.

w W (2000) i q e a I 38.8 275.7 2.5 0.930 0.628 2.5 II 7.6 275.7 3.1 1.013 0.662 3.0 11P (1938) 161.97 242.19 13.27 1.4876 0.5585 3.37 107P (1936) 81.00 280.18 2.81 1.0052 0.6197 2.64 2004 HW 62.45 220.28 0.83 0.9784 0.6363 2.69

Gamma Draconids

The earliest mention of this meteor shower came in 1968, when A. K. Terentjeva presented a paper titled “Investigation of Minor Meteor Streams.” She analyzed 3,700 photographic meteor orbits and found 95 new meteor streams. Four meteors de fi ned this stream and indicated a duration of May 25 to June 11; however, because of distinct differences in the eccentricities, she broke the stream down into two branches labeled “a” and “b.” The two meteors in branch “a” came from a radiant at a = 276°, d = +52°, while the orbital period of the stream was 6.77 years. The two meteors in branch “b” came from a radiant at a = 275°, d = +50°, and the indicated stream was strongly hyperbolic. The stream was labeled “216” in Terentjeva’s list of 95 streams and was called the “g Drads.”55 This paper was a continuation of an earlier paper presenting 154 minor meteor streams. The 249 total minor streams did not seem to get the attention they deserved and little, if any, follow-up observations were made in the ensuing years. This meteor shower was next noted on the night of 1996 June 15/16. M. Langbroek (Voorschoten, Netherlands) made the fi rst announcement in the 1996 August issue of the Journal of the International Meteor Organization. Starting at 22:53 UT, he saw a magnitude 0 meteor moving at a medium fast to fast speed, which he estimated as about 50 km/s. A few similar velocity meteors were noted until 23:30 UT and then “a fl urry of meteors appeared, again with that very characteristic velocity, all seemingly dispersing from a radiant near the head of Draco….” The greatest number of meteors was seen at 23:35 UT (l = 84.473°), and the last meteor from this area was seen about an hour later. Ultimately 13 meteors were plotted from this shower, with the radiant at a = 280°, d = +55°. Langbroek decided to call them the “Xi Draconids.” He determined a ZHR of about 20 and a population index of r = 2.7.56 Langbroek posted some preliminary details on the Internet and asked if any other observers had detected activity. G. Zay (Descanso, California, USA) quickly responded that he and R. Lunsford (Descanso) had observed weak activity from this Tau Herculids 117 radiant. Zay saw the meteors on the night of June 16, while Lunsford saw them on nights other than the 15th and 16th. Although the radiant position was initially determined as a = 274°, d = +54° by Lunsford and a = 280°, d = +53° by Zay,57 R. Arlt later said that 23 meteors plotted by Lunsford indicated a radiant at a = 300°, d = +58°, which was 11° northeast of Langbroek’s result.58 Arlt wrote an article about this display in the next issue of the Journal of the International Meteor Organization . He said V. Velkov and K. Koleva (Bulgaria) had also seen activity on the night of June 15/16. Velkov, an experienced observer, said fi ve meteors emanated from a radiant at a = 283°, d = +50°. The ZHR for 2.59 h of observing was 3.2. In comparing the radiant and estimated velocities given by Langbroek, Zay, and Lunsford, Arlt wrote, “The highest prominence of the radiant, calculated by probability functions is achieved at a geocentric velocity of 47 km/s.” 59 The International Meteor Organization has a website containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. There is evidence of activity on June 14 (l = 83°), when 44 meteors emanated from a radiant at a = 285.1°, d = +51.5°, June 15 (l = 84°), when 51 meteors emanated from a radiant at a = 286.0°, d = +51.0° and June 16 (l = 85°), when 38 meteors emanated from a radiant at a = 280.1°, d = +52.5°.60 There are additional radiants that are nearby on these dates that may also be associated. The orbits labeled “a” and “b” are from Terentjeva (1968). The orbit labeled “1996” was calculated based on Langbroek’s radiant position.

w W (2000) i q e a a 201 65 50 0.98 0.72 3.58 b 202 77 56 0.98 1.30 −3.68 1996 196.6 85.4 52.4 10.995 1.0 ¥

Tau Herculids

The discovery of this meteor shower occurred as a result of the discovery of its parent comet. The latter discovery occurred on 1930 May 2, when plates exposed by A. Schwassmann and A. A. Wachmann (Hamburg Observatory, Germany), during a regular minor planet survey, revealed the diffuse image of a comet. The saga of the Tau Herculids unfolded a short time later at an observatory in Japan. Kwasan Observatory (Kyoto, Japan), like many observatories around the world, was following this comet almost daily. One astronomer at this observatory, Watanabe, calculated a preliminary parabolic orbit from which his colleague, Y. Sibata, predicted a meteor shower might be produced by this comet that would peak on June 9. K. Nakamura commenced watching the sky on the night of May 21, but no activity from the predicted radiant was noted until May 24, when a stationary 118 7 June Meteor Showers meteor was seen coming from a = 230°, d = +48°. The next evening, several more meteors were seen radiating from a point slightly less than a degree east of the previous night’s position. Nakamura said that as the comet reached naked-eye visibility, his work of making observations of it “prevented the writer from tracing the meteors very faithfully up to the end of May.” By June 3, the meteor shower was again under scrutiny and Nakamura noted meteors emanating from a radiant at a = 232°, d = +46°. Further observations were made on the 6th and 7th as the radiant continued its southeastward trek, but the fairly weak activity observed up to this point suddenly changed on June 9, when Nakamura spotted 59 meteors (most of which were described as fainter than 4th magnitude) in 1 h, despite a 13-day-old moon. Short-trailed meteors were used to determine the radiant position as a = 236.25°, d = +41.5°. Nakamura saw slightly higher rates the next evening when 36 meteors were seen in 30 min. Weak displays had again returned when observations resumed on June 12 and 13, and the shower was last detected on June 19, from a radiant of a = 244.5°, d = +39°.61 Another Kwasan Observatory astronomer, K. Komaki, said that he, his wife, and K. Yosii watched for this meteor shower as well from his residence in Kanaya (now Aridagawa, Wakayama, Japan). He said that Yosii spotted ten meteors in a clear sky on the night of June 8/9 during 1 h and 10 min of observing, but added that only one was suspected as belonging to this shower. His wife saw another meteor at 1:11 a.m. on the 9th, which was also suspected as belonging to this shower.62 It should be noted that by the fi rst days of June, the prediction of a possible strong meteor shower had been published in newspapers around the world. Meteor section members of the British Astronomical Association noted that bright moonlight interfered with their observations on June 5, 7 and 9, so that no display of any kind was observed.63 I. Yamamoto, director of the Kwasan Observatory, commented on Nakamura’s paper that was published in the 1930 November issue of the Monthly Notices of the Royal Astronomical Society . He wrote, “Mr. Nakamura was practically the only observer, among several other members of the staff of Kwasan who were watching the sky for the expected meteors in last May and June, who successfully observed the display.” He continued, “Quite recently, however, Mr. K. Siomi, a young member of the Society of Astronomical Friends, sent his reports to me, among which I found fi ve meteors, seen on June 12–13, which are de fi nitely radiating from a radiant point, R.A. 237.5°, Decl. +41°, so that these undoubtedly belong to the shower from the comet….” Siomi, who lived in Fukuchiyama (Kyoto, Japan), had added that most of the meteors were faint, which agreed with Nakamura’s assessment.64 The observations of Nakamura were called into question during 2001. H. Lüthen, R. Arlt, and M. Jäger examined several aspects of the reports from Kwasan Observatory. They noted that there was a full moon on the night of June 9–10, yet Nakamura stated that few of the meteors were brighter than magnitude 4. Lüthen et al. wrote, “Even observers with very high perception will hardly be able to spot a considerable number of +5 and +6 meteors under such poor conditions….” The authors also re-examined Nakamura’s published plots of the June Boötid outburst that he observed in 1921. They wrote, “we found that what he calls high activity Tau Herculids 119 consists of very many meteors which start within the radiant and move out of it for about 10°. Every present-day meteor observer knows that this is nonsense.” They also examined the dust trails left by comet Schwassmann-Wachmann three that might have been responsible for enhanced activity during 1930. Only the 1892 dust trail could have come close enough to produce meteors. Particles from this dust trail were closest to Earth during May, and when Earth was closest to the comet’s node on 1930 June 8, there were over 0.01 AU from our planet. Nevertheless, they predicted the likely radiant and found it would have been at a = 219°, d = +45°, “far away from the listed radiant of Nakamura.”65 The only possible pre-1930 detection of this shower came during 1918 June 3–7, when W. F. Denning detected 4 very slow “Theta Coronids” from a radiant of a = 230°, d = +34°. 29 Following the 1930 shower, attempts at further observations proved fruitless. J. P. M. Prentice (Stowmarket, England) watched on 1931 May 20, 22, 23, and 24. His total observing time amounted to 11 h and 20 min, but no activity was noted. Stars to magnitude 6 were visible some of the time. 63 Additional attempts to reob- serve this shower—usually during the years of the comet’s predicted perihelion— occurred on several occasions during the 20 years following 1931, but no traces of the shower were ever noted. However, using photography during the early 1950s, the Harvard Meteor Project revealed the stream to still be producing meteors. R. B. Southworth and G. S. Hawkins (1963) detected two photographic meteors: one from 1953 June 20 and the other from 1954 June 25.66 B. A. Lindblad (1971) took a further look at possible photographic meteors associated with this comet. He identi fi ed 14 meteors from the Harvard Meteor Project. The average orbit “suggests good agreement in all orbital elements, and the proposed comet-meteor relation may now be considered very probable.”67 The last extensive search for meteors of this stream came in 1974, following a prediction by K. Kono.68 With Schwassmann-Wachmann 3 coming toward a mid- March 1974 perihelion, Kono predicted that a shower might occur on June 1.0 from a = 146°, d = +54° [ the comet’s orbit having underwent some changes since its 1930 apparition ]. H. R. Povenmire noted that observations for 2 h on June 1 by members of the Florida Fireball Network revealed only one meteor from the radiant, though moonlight was interfering.69 Some observers took an interest in this meteor shower during the late 1970s and early 1980s. During 1976 June 1–25, B. Matous (Grandview, Missouri, USA) observed only four Tau Herculids. 70 During 1977, J. West (Bryan, Texas, USA) saw two Tau Herculids on May 26 and 28, C. Smith (Bryan, Texas) saw three in 3 h,71 Matous saw 17 during June 6–11, and N. W. McLeod, III, (Florida, USA) recorded fi ve during May 21 to June 12.72 During 1979, F. Roy (Pte. Gatineau, Quebec, Canada) saw three meteors on June 3/4.73 During 1982, West saw four meteors in 4 h on May 22/23 and 27/28, while M. Zalcik (Edmonton, Alberta, Canada) observed two in 3 h on May 23/24. 74 During 1984, D. Swann (Dallas, Texas) saw no meteors during 2 h on May 29/30, one during 2 h on May 31/June 1 and one during 1 h 30 min on June 1/2. B. Katz (Willowdale, Ontario, Canada) observed during 6 h on June 3/4. Tau Herculids were noted each hour with the highest hourly 120 7 June Meteor Showers rate being six and the lowest being two.75 This marked some of the highest rates in recent years. Interestingly, the higher rates in 1984 fi t with the prediction of Lüthen et al. (2001). Examining the dust trails of comet Schwassmann-Wachmann 3 and making predictions of past encounters, they noted that Earth passed 0.0023 AU from the 1952 trail on June 3.47 UT.76 Lüthen et al. also provided predictions for future encounters with dust trails and mentioned 2001, 2011, 2017, and 2022 as possibilities for enhanced activity. No enhancement was noted in 2001, but P. Jenniskens, M. Phillips, R. Morales, and B. Grigsby reported “the detection of a meteor outburst of Tau Herculids on 2011 June 2.” They were using NASA’s Cameras for Allsky Meteor Surveillance in California. During 04:00–12:13 UT, the video cameras detected 12 meteors, of which three were Tau Herculids. These three meteors came from a “compact geocentric radiant” at a = 215.5°, d = +34.0°, while the average geocentric velocity was 12.55 km/s.77 With respect to the 2017 and 2022 meteor showers, Lüthen et al. said Earth would pass 0.0013 AU from the 1941 dust trail on 2017 May 31.136 and 0.0004 AU from the 1995 dust trail on 2022 May 31.205. They considered the latter date to be more promising since the comet broke up into multiple fragments, adding “the trail is more populated due to the massive expulsion of dust observed in 1995.”78 The orbit labeled “1930” was calculated using Nakamura’s radiant positions in 1930 and assuming the semimajor axis of periodic comet Schwassmann-Wachmann 3. The orbit labeled “1952–1954” is from Lindblad (1971). The orbit labeled “2011” was determined by Jenniskens et al. (2011).

w W (2000) i q e a 1930 202.1 76.6 22.2 0.985 0.681 3.09 1971 204.2 72.6 18.6 0.970 0.633 2.70 2011 199.5 71.303 13.60 0.991 0.651 2.84

The following orbits are of periodic comet 73P/Schwassmann-Wachmann 3 and are labeled “1930” and “2012,” with the latter orbit representing the orbit of fragment “C”.

w W (2000) i q e a 1930 192.35 77.73 17.39 1.0114 0.6718 3.08 2012 198.87 69.84 11.38 0.9429 0.6922 3.06

K. Fox (1986) determined the stream orbit for 1,000 years into the past and future. The following were determined for the Tau Herculids: June Lyrids 121

w W (2000) i q e a 950 169.1 90.9 23.1 1.07 0.60 2.68 2950 321.5 323.0 13.6 0.91 0.66 2.69

This study reveals a very interesting variation of the Tau Herculid activity over 2,000 years. About 1,000 years ago the shower’s maximum occurred during the latter half of June from a = 220.6°, d = +72.4°, while 1,000 years in the future maximum will occur in mid-August from a = 154.7°, d = −29.4°.44

June Lyrids

This meteor shower was discovered on the evening of 1966 June 15 by S. Dvorak while camping out in the San Bernardino Mountains (California, USA). His attention had been drawn to the region of Lyra by a very bright meteor that moved swiftly to the northeast through that constellation. Another meteor was noted a short time later and Dvorak began plotting additional meteors. After 1 1/2 h he had managed to plot 16 meteors, of which 13 appeared to originate from a hitherto unknown radiant located at a = 277.5°, d = +30°. He said the meteors “left trains visible for three to six seconds.”79 K. B. Hindley (1969) reported additional observations of this meteor shower. He said that a few hours after the observation by Dvorak, F. W. Talbot (Cheshire, England) reported seeing meteors emanating from a radiant at a = 275.5°, d = +30° at a rate of almost 9 per hour. Hindley added that moonlight interfered with observations in 1967, but that R. Nolthenius (Hacienda Heights, California) saw the shower on 1968 June 15 and 17. Nolthenius reported seeing eight June Lyrids during 1 h on the ﬁ rst night, and seeing seven meteors from this radiant on the second night.80 Hindley reported that the Meteor Section of the British Astronomical Association was requested to make observations during 1969 June 10–20. Results came from 46 observers, putting in 172 man-hours. The observations covered the period of June 11.5–21.0 ( l = 80.2°–89.2°) and the total number of June Lyrids observed was 363. Against a fairly constant sporadic meteor rate of 8.7 per hour, the June Lyrids displayed a broad maximum of about 6 per hour during June 13–17, with a sharp peak of 9 per hour on June 16.0 (l = 84.5°). The average magnitude was found to be 2.0 and 32 % of the shower’s meteors showed persistent trains. The average radiant was found to be a = 278° ± 2°, d = +35° ± 3°. From this position, Hindley calculated a parabolic orbit which revealed a close, but “not convincing” similarity to comet C/1915 C1 (Mellish), which was moving in a slightly hyperbolic orbit. Hindley concluded, “It is possible that the June Lyrids represent a meteor stream which has only become active in recent years, possibly due to the stream’s orbit being perturbed to a position close to the Earth’s orbit at its descending node.”81 122 7 June Meteor Showers

Adding even more evidence to the existence of this meteor shower, Z. Sekanina (1976) reported that 11 meteors were detected from the June Lyrids during 1969 by the Radio Meteor Project. The nodal passage was given as June 17.1 ( l = 85.5°), at which time the radiant was at a = 281.9°, d = +43.6°. The geocentric velocity was determined as 27.1 km/s. Sekanina said the radiant was only active from June 16.3 to 17.9.14 About 188 h of observations were made by 26 observers from the United States and Canada during 1971 June 10–24. The shower’s ZHR irregularly varied, with maximum peaks of 1.3–3.5. The radiant of the stream was determined from 37 meteors plotted by an Ottawa observing group from observations made during June 14 to 17, with the result being a = 278.3°, d = +41°.82 In 1972, the shower again showed a poor return. Meteor News combined the observations of 20 observers made during June 9–22. During the nights of June 10/11–14/15, the hourly rate fl uctuated between 0.4 and 1.3. The shower peaked on the night of June 15/16 at an hourly rate of 2.3. After an hourly rate of 1.6 on June 16/17 and 1.0 on June 17/18, the rates dropped to 0–0.3.83 Observations in 1974 indicated a resurgence of activity. The shower’s discoverer, Dvorak, observed on four nights during mid-June, with the following average hourly rates being noted: June 14/15, 2.9; June 15/16, 6.5; June 16/17, 6.2; June 17/18, 2.3. Dvorak added that the meteors moved swiftly, with the majority being bluish-green. Also, in 1974, Nolthenius, A. Devault and B. Fischer (all of California) observed during seven nights between June 9 and 22. Overall, they observed 32 June Lyrids, with the average magnitude being determined as 3.09. Slightly less than half of the June Lyrids were seen on the shower’s night of maximum (June 15/16). The average number of meteors seen from this radiant was 4 per hour.84 A weak return greeted observers during 1975. Between June 6 and 15, N. W. McLeod III (Florida, USA) saw only two June Lyrids, while, during the period June 9–14, M. T. Adams (Pennsylvania, USA) noted fi ve members, with four coming in less than 3.5 h on the fi nal date of observation. Interestingly, P. Jones (St. Augustine, Florida) observed for 3 h on the night of maximum and detected 20 June Lyrids.85 Interest in the June Lyrids seems to have waned in the latter half of the 1970s and into the 1980s, with only a few individuals continuing to monitor the shower annually—many of them rarely observing around the time of the shower’s established date of maximum. As is evident from the previously listed observations, activity from this radiant can be virtually nonexistent on dates other than June 15 and 16, due to the June Lyrids’ very pronounced peak of activity. In 1979, observers in Texas observed on June 15/16 and 17/18, with meteors attaining a rate of 2 per hour on the last date. F. Roy (Quebec, Canada) observed during June 16/17, 18/19 and 20/21 and noted 12 meteors in about 3.5 h. 73 During 1980, the enhanced rates still seemed present, with J. West (Texas, USA) noting 18 meteors in only 5 h on June 13/14 and 14/15.86 A search for pre-1966 observations of this shower has revealed only one possible observation. From meteor paths recorded by G. Zezioli (Italy), G. V. Schiaparelli found 11 meteors observed on 1869 June 14 came from a radiant at a = 280°, d = +35°. 87 June Lyrids 123

Observations after 1980 are hard to fi nd in the literature, and in 1995 the International Meteor Organization (IMO) removed the June Lyrids from their “Working list of meteor showers,” noting, “The present annual activity calculated from 64 IMO records is at 1.5 ± 0.4 without distinct maximum, i.e., at the detection limit.”88 Interestingly, the next year M. Weber (Chouzavá, Czech Republic) observed the June Lyrids, noting 11 shower members in 5.7 h. He gave the ZHR as 3.1 ± 5.3 on June 10/11, 4.5 ± 4.5 on June 11/12, and 8.9 ± 5.4 on June 14/15.89 K. Fox (1986) integrated the orbit of the June Lyrids 1,000 years into the past and future. This indicated that the June Lyrids were reaching maximum in late June 1,000 years ago from a radiant at a = 286.0°, d = +36.4°, while 1,000 years in the future they will be at maximum during early June from a = 271.0°, d = +35.7°. Thus, if the stream is in a short-period orbit, it should have been visible for quite some time. Since the shower seems to have suddenly appeared in 1966, this may indicate that the assumed semimajor axis of 2.5 AU may not be correct, or the stream is in the orbit of a long-period comet. M. R. Kidger (2000) examined the evidence for this meteor shower. In addition to the above information, he said that the Agrupacion Astronomica de Tenerife had detected weak activity during 1990, which amounted to a ZHR of about three on June 17 ( l = 85.8°). Kidger stated that these observations prompted a study by J. M. Trigo-Rodríguez which examined the observations made by the Sociedad de Observadores de Meteoros y Cometas during 1988–1990 and determined a peak ZHR of fi ve. Kidger then searched through the IMO Visual Meteor Database and said June Lyrid observations were made every year from 1985 to 1997. Although the average ZHR was 3.1, he said the shower “experiences signifi cant variations from year to year.” As examples, he cited a potential high ZHR of 10 in 1986, while the shower was “marginally detected” at best in 1997.90 The orbit labeled “1969” is the parabolic orbit calculated by Hindley (1969) from visual observations. The orbits labeled “1973a” and “1973b” are from A. F. Cook (1973). Cook took information from Hindley’s paper and calculated orbits with assumed semimajor axes of 2.5 and 10 AU, which he believed represented “likely extremes.”91 The orbit labeled “1976” is the elliptical orbit provided by Sekanina (1976) using radio-echo observations. The orbits labeled “950” and “2950” are from Fox (1986). Fox took Cook’s orbit with the semimajor axis of 2.5 AU and integrated it 1,000 years into the past and future. The orbit labeled “C/1915 C1” is the orbit of comet Mellish.

w W (2000) i q e a 1969 214 86 52 0.91 1.0 ¥ 1973a 237 85.2 44 0.83 0.67 2.5 1973b 231 85.2 50 0.84 0.92 10 1976 224.1 86.2 45.3 0.912 0.556 2.05 950 238.1 92.4 46.0 0.83 0.67 2.5 2950 235.8 78.4 42.1 0.80 0.68 2.5 C/1915 C1 247.78 73.45 54.79 1.0053 1.0002 −6,657 124 7 June Meteor Showers

Epsilon Perseids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) announced the discovery of 13 new meteor showers after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired during 2002–2006. The Epsilon Perseids were said to span the period of June 23 to July 9 ( l = 92–107°), with its maximum coming on June 26 (l = 95.5°) from a radiant at a = 58.2°, d = +37.9°. The geocentric velocity was given as 44.8 km/s, while the radiant’s daily motion was determined as +0.78° in a and +0.15° in d .92 Complete details were published in the journal Icarus during 2008.93 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as June 22 to July 9 (l = 91–107°). The date of maximum was given as June 27 ( l = 96°), at which time the radiant was at a = 58.3°, d = +37.5°. The geocentric velocity was determined as 44.6 km/s. The radiant’s daily motion was determined as +0.87° in a and +0.14° in d . 18 The International Meteor Organization has a website containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. There is no trace of this shower over solar longitudes (l ) of 92–93° and 95–101°, but at l = 94.0°, 27 meteors did emanate from a radiant at a = 60.8°, d = +41.5°.60 A search for previous observations was not very successful. W. F. Denning (1878) examined the observations made by the Italian Meteoric Association during 1872 and found ten meteors that emanated from a radiant at a = 64°, d = +46°.94 But searches through dozens of other lists published during the nineteenth and twentieth centuries revealed no matches. This could indicate that the radiant noted by Denning might have been a chance alignment. The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 203 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 1139 meteor orbits.

w W (2000) i q e a 2002–2006 38.0 95.5 64.9 0.123 0.9688 3.9 2002–2008 38.83 96.0 62.3 0.1263 0.970 4.15

Daytime Zeta Perseids

Duration: May 20 to July 5 (l = 59–103°) Maximum: June 4 (l = 74°) Radiant: a = 63°, d = +26° ZHR: High

Radiant Drift: a = +1.1°, d = +0.4° V G : 26 km/s Daytime Zeta Perseids 125

This daylight meteor shower was discovered in 1947, when operators of the radio equipment at Jodrell Bank (England) detected activity during May 30 to June 17. The meteors were visually detected by observers monitoring a cathode-ray tube display. Although the radiant was not accurately determined, J. A. Clegg, V. A. Hughes, and A. C. B. Lovell (1947) noted a radiant within the range of a = 52–62°, d = +15°, with an hourly rate of 20–40.5 A. Aspinall, Clegg, and Lovell (1949) noted that the Daytime Arietids and the Daytime Zeta Perseids “were not delineated in the 1947 observations. In retrospect, however, it is now evident that both these radiants existed in 1947 but the records were wrongly interpreted as indicating a radiant at a = 57°, d = +15°.” The 1948 survey at Jodrell Bank used a photographic method to record the meteors. The Daytime Zeta Perseids were detected during 22 days, with the radiant moving from a = 57°, d = +27° on May 25 to a = 76°, d = +33° on June 16. The Daytime Zeta Perseids peaked on June 1, reaching an hourly rate of 34.6 Jodrell Bank observations continued during 1949 and 1950, with Aspinall and G. S. Hawkins noting that the radiant moved from a = 58.0°, d = +28.0° on June 1 to a = 71.5°, d = +29.5° on June 16, with the weighted mean position being a = 61.6°, d = +23.8° on June 7. The highest hourly rate of 39 came on June 3.95 B. L. Kashcheyev and V. N. Lebedinets (1967) conducted a radar study during 1960, using equipment at the Kharkov Polytechnical Institute (Ukraine). The analysis revealed a duration of May 4 to June 19, with the nodal passage coming on June 2 (l = 71°), and the average radiant being a = 52°, d = +23°. 96 Two radar studies were conducted using equipment at the University of Adelaide (South Australia) during the 1960s. Unfortunately they were operated over periods of about a week, so that their results might be considered somewhat misleading when considering the radiant position and orbit. The ﬁ rst operated in 1961, when C. S. Nilsson detected the Daytime Zeta Perseids during June 13–16, and determined the radiant as a = 64.2°, d = +25.4°. He mentioned that the equipment had also been operated during May 19–28, and that a radiant at a = 44.3°, d = +19.5° was probably the same as the June shower.97 The second survey was conducted during 1969 June 9–14 by G. Gartrell and W. G. Elford. It revealed a radiant at a = 65°, d = +27°, and the authors showed that the stream was probably the twin of the Southern Taurids of November.98 During the 1961–1965 session of the Radio Meteor Project, Z. Sekanina determined the duration as May 20 to June 21. The date of the nodal passage was given as June 8.9 ( l = 77.6°), at which time the radiant was at a = 60.2°, d = +24.8°. 99 During the 1968–1969 session, Sekanina determined the duration as May 22 to July 4. The date of the nodal passage was then given as June 12.2 (l = 80.8°), while the average radiant position was determined to be a = 63.3°, d = +27.1°.14 This stream was detected during 2002–2008 by the Canadian Meteor Orbit Radar system.100 P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) detected 2304 meteors during the period of May 17 (l = 56°) to June 21 (l = 90°). The peak of activity occurred on June 4 (l = 74°) from a radiant at a = 56.6°, d = +23.2°. The geocentric velocity was determined as 27.1 km/s.18 126 7 June Meteor Showers

From observations made in the United States and Australia during 1971, it appears that meteors from this shower can be visually detected coming up from the horizon during the hours immediately after sunset and immediately before sunrise.101 D. Skelsey (Sydney, Australia) observed one Daytime Zeta Perseid during 2 h on June 5/6, while K. Simmons estimated that the combined rates of the Daytime Zeta Perseids and Daytime Arietids (earlier in chapter) reached one to two meteors per hour on the morning of June 6/7. Several orbits have been determined over the years. The “1960” orbit is from Kashcheyev and Lebedinets (1967). The “1961” orbit is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The “1968–1969” orbit is from Sekanina (1976). The orbit labeled “1969” is from Gartrell and Elford (1975). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1960 57 72 6 0.31 0.80 1.61 1961 55.5 84.4 5.7 0.300 0.82 1.67 1961–1965 59.3 78.2 5.3 0.319 0.834 1.92 1968–1969 60.6 81.4 6.5 0.365 0.755 1.49 1969 69 82 7.1 0.30 0.82 1.72 2002–2008 58.84 74.0 3.9 0.3305 0.800 1.65

Sagittariids

This stream appears to have been discovered during 1957 and 1958 while radio- echo surveys were being conducted at the University of Adelaide (South Australia, Australia). A. A. Weiss reported the shower to have rates of 30 per hour from a compact radiant. This rate is close to the detection threshold of the equipment. The radiant’s position was determined as a = 307°, d = −35° in 1957 and a = 301°, d = −36° in 1958. The date of maximum was given as June 11, while the total duration was 5 days. Weiss said no hint of the shower had been noted in 1952, 1953, 1954 and 1956.102 A more sensitive radar system was operated at the University of Adelaide during 1968–1969. The analysis by G. Gartrell and W. G. Elford (1975) detected only four meteors, so that the stream seemed practically nonexistent. For the mean activity date of June 10 (l = 80°), the radiant was established as a = 297°, d = −34°.98 Visual activity from this shower seems rare, as some of the most comprehensive southern hemisphere radiant catalogs have failed to reveal convincing evidence of the radiant’s existence prior to 1957. Recent observations also appear to be rare, although Jeff Wood, Director of the Western Australia Meteor Section (Australia), lists what appears to be a probable detection of this shower in 1980. The radiant Scorpiid-Sagittariid Complex: Antihelion 127 was called the “Alpha Microscopiids” and was detected only during June 11 and 12. A maximum ZHR of about 1.5 occurred on June 11 from a radiant of a = 305°, d = −36°.103 The International Meteor Organization’s Video Meteor Network created a website titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the Sagittariids are present within this sample. A radiant at a = 299.6°, d = −38.5° was delineated by 20 meteors on June 9 ( l = 78°). A radiant at a = 303.9°, d = −31.0° was delineated by 34 meteors on June 10 (l = 79°). A radiant at a = 304.0°, d = −34.0° was delineated by 43 meteors on June 11 (l = 80°). A radiant at a = 302.2°, d = −36.0° was delineated by 25 meteors on June 12 (l = 81°). 60 The orbit labeled “1969” is from Gartrell and Elford (1975).

w W (2000) i q e a 1969 152 260 33.5 0.11 0.90 1.15

Scorpiid-Sagittariid Complex: Antihelion

This is the largest region of activity during the year, completely spanning the months of May through July and the constellations of Libra, Ophiuchus, Sagittarius, Scorpius, and Capricornus. Several individual radiants seem to be active each year, but research shows that few of these radiants produce annual displays. Unlike the Virginid Complex [see Chap. 4 ], none of these radiants produce more than 1–2 meteors per hour. In the 1988 edition of this book, several of these streams were addressed individually with weaker radiants left out of the book entirely. For this edition it was decided to consider the region as a whole. C. Hoffmeister called this region the “Scorpius-Sagittarius System.” He classed it as one of the “Ecliptical Currents” visible during the year. Hoffmeister considered the “Ecliptical Currents” to be “regarded as differing in principle from the cometary currents” and said they generally appear 165° west of the Sun and are caused by currents of meteors.104 Today, these “Ecliptical Currents” are known as “antihelion” radiants. Photography and radio surveys have helped defi ne these areas of the sky by determining the orbits of meteors emanating from this region. According to R. Lunsford (2004), “this material orbits the sun in low-inclination, direct orbits, and encounters the Earth on its inbound or pre-perihelion portion of its orbit.” The meteors encounter Earth perpendicular to our planet’s direction of motion. Lunsford suggests that the source of antihelion meteors is probably “a combination of material produced by the Jupiter family of comets and Earth-crossing asteroids.”105 Hoffmeister described the Scorpiid-Sagittariid Complex as a “typical case of a dissolved current. There is no de fi ned radiant appreciable, the meteors radiating uniformly from an area up to 30° in diameter.” He continued, “But sometimes very 128 7 June Meteor Showers pronounced centers use to appear, vanishing again within 24 h. It is not before the fl at maximum at 75–80° that a distinct core is formed with the radiant at 270−30°. But very soon the area becomes diffuse again, extinguishing between 110° and 120°.” 104 It is interesting that the period of the fl at maximum and given radiant are quite close to what is expected for the “Theta Ophiuchids,” which have also been referred to as the “Alpha Scorpiids” and “Delta Sagittariids,” and “Scorpiids- Sagittariids.” The earliest account of meteors coming from this region appeared in the 1878 July issue of The Observatory . W. F. Denning discussed three fi reballs that were seen on 1878 June 7. The fi rst appeared in daylight, while the other two appeared in the early evening. In his conclusion, Denning said these last two appeared to diverge from a radiant near the star Antares. He gave the position as a = 246°, d = −20° and added that this was “not far from that of the detonating fi reball of June 17, 1873….” He also pointed out that Italian observers had recorded six meteors from a “fairly well-defi ned” radiant at a = 253°, d = −24° on 1872 June 7.106 The Italian radiant is not far from that of the Theta Ophiuchids, which peak a couple of days later. Denning again mentioned this region as a fi reball producer in 1884. In the April issue of the Monthly Notices of the Royal Astronomical Society, he stated that during June and July, “Several fi reballs [have appeared] from the northern limits of Sagittarius.” He gave the radiant as a = 285°, d = −12°. 107 In the May issue of The Observatory, Denning mentioned the appearance of two large fi reballs that were seen within 2 h of one another on 1883 June 3. He said G. Niessl was able to determine the radiants for each of these and found they originated from almost the same spot in the sky. One fi reball came from a radiant at a = 249.9°, d = −20.2°, while the other came from a = 248°, d = −20°. Denning again referred to the 1872 radiant that was detected by Italian observers and said the same group had also recorded meteors from a radiant at a = 247°, d = −18° on 1868 June 10–11.108 A few additional observations were reported during the last years of the nineteenth century. Denning (Bristol, England) published the results of his observations and did not mention the radiants discussed above. He did, however, report a radiant seen during 1886 April 30 to May 5 at a = 254°, d = −21° and 1887 June 10–20 at a = 268°, d = −24°. The meteors from the fi rst radiant were described as “slow,” while those from the second radiant were “very slow, bright.” 109 W. Doberck (Hong Kong Observatory) provided a list of radiants he had detected. He said meteors were detected during May 14 to June 25 of both 1893 and 1895 from a radiant at a = 245.5°, d = −28°. He calculated a parabolic orbit that is very close to the orbit of the “Chi Scorpiids” given below.110 H. Corder (England) reported fi ve slow meteors were detected during 1896 May 12–14 from a radiant at a = 248°, d = −15°.111 A. S. Herschel (England) detected two radiants from this region during 1894–1899 May 3–9. He said four meteors came from a radiant at a = 230°, d = −20°, while another four meteors came from a = 252°, d = −24°. 112 Throughout the period that these observations cover, occasional fi reballs were reported from the region, including from around the star Alpha Scorpii. Scorpiid-Sagittariid Complex: Antihelion 129

Observers continued to occasionally report radiants from this region during the fi rst few decades of the twentieth century. The fi rst visual survey of this century was the Arizona Expedition for the Study of Meteors. E. J. Öpik analyzed the data and published a list of radiants during 1934. Radiants were detected at a = 258°, d = −17° on 1932 May 29, a = 270°, d = −16° on 1932 June 11–14, a = 241°, d = −15° on 1933 May 15–16, a = 244°, d = −14° on 1933 May 26–27, and a = 286°, d = −20° on June 25.113 In R. A. McIntosh’s “An Index to Southern Meteor Showers,” which was published in the Monthly Notices of the Royal Astronomical Society in 1935, meteor observations from the New Zealand Meteor Section, as well as from a few other sources in the United States, England, and Russia, were reduced. The outcome was a list of 320 radiants that were visible from the Southern Hemisphere. Although McIntosh did not speci fi cally note the large number of radiants that were visible during May–July from the Libra, Ophiuchus, Scorpius, Sagittarius, and Capricornus regions, there are about four dozen in his list.114 Radiants from the Scorpiid-Sagittariid Complex were also found during the analysis of the meteors photographed during the Harvard Meteor Project, which spanned 1952–1954. R. B. Southworth and G. S. Hawkins (1963) identi fi ed fi ve meteors as members of a “new” meteor stream they called the “Theta Ophiuchids.” The duration of this stream was given as May 21 to June 16, and it was determined that 0.37 meteors could be photographed every hour. The average radiant was given as a = 264.0°, d = −26.8°. 115 B. A. Lindblad (1971) essentially confi rmed Southworth’s and Hawkins’ fi ndings—with one extra meteor being found. Lindblad had conducted a computerized search among 865 precise photographic meteor orbits and noted the same duration, but with the average radiant being at a = 265°, d = −27°.116 Further proof of the stream’s existence was obtained by Lindblad during a second computer stream search among 2,401 photographic meteors. The duration on this occasion was determined to be June 4–16, while the average radiant was a = 266°, d = −28°. 117 Meteors may be found in the Harvard Meteor Project collection that obviously come from the Scorpiid-Sagittariid Complex, but they were not plentiful enough to have been found by the stream searches. A. K. Terentjeva has identi fi ed several radiants using photographic orbits from several surveys. A paper written in 1966 presented 154 minor meteor showers, of which fi ve radiants probably belong to the Scorpiid-Sagittariid Complex. The “North Ophiuchids” were based on four meteors. The duration was June 16 to July 3, while the average radiant was a = 257.2°, d = −10.1°. The “South Ophiuchids” were based on three meteors. The duration was June 16 to July 3, while the average radiant was a = 259.3°, d = −31.7°. The “Zeta Serpentids” were based on four meteors. The duration was June 22 to July 6, while the average radiant was a = 268.0°, d = −14.5°. The “Scutids” were based on four meteors. The duration was June 12–29, while the average radiant was a = 276.0°, d = −15.3°. The “Gamma Scutids” were based on four meteors. The duration was August 5–14, while the average radiant was a = 275.5°, d = −17.5°. The “Eta Aquilids” were based on two meteors. The duration was August 1–16, while the average radiant was a = 296.0°, d = +4.5°. 118 A paper written in 1968 presented 95 more minor meteor showers from her analysis 130 7 June Meteor Showers of 3700 photographic meteor orbits. She found two radiants belonging to the Scorpiid-Sagittariid Complex. The “36 Ophiuchids” were based on three meteors. The indicated duration was May 27 to June 8, while the average radiant was a = 259°, d = −26°.. The “Eta Ophiuchids” were based on two meteors. The indicated duration was June 8–10, while the average radiant was a = 259°, d = −16°. 119 C. D. Ellyett and K. W. Roth (1955) found four radiants from this complex while using radio equipment at the University of Adelaide (South Australia, Australia) during 1953. Radiant “6” was based on six meteors detected during June 19–25 from a radiant at a = 268°, d = −23°. Radiant “7” was based on 11 meteors detected during June 17–28 from a radiant at a = 270°, d = −13°. Radiant “8” was based on ten meteors detected during June 17–28 from a radiant at a = 263°, d = −21°. Radiant “9” was based on fi ve meteors detected during June 17–26 from a radiant at a = 252°, d = −20°. The reason the duration of three of these radiants begins on June 17 is because the radiant was active when the equipment was switched on after a “non-operative period.”120 C. S. Nilsson (1964) analyzed the 2200 meteor orbits that had been determined using the radio equipment at the University of Adelaide during 1960–1961 and found a few streams that belong to the Scorpiid-Sagittariid Complex. Stream 61.5.10 was active from May 19 to 25 from a radiant at a = 255.2°, d = −19.1°. The geocentric velocity was determined as 32.5 km/s. Stream 61.6.6 was active during June 13–19 from a radiant at a = 277.7°, d = −20.0°. The geocentric velocity was determined as 26.5 km/s. Stream 61.6.9 was active during June 16–17 from a radiant at a = 267.2°, d = −27.7°. The geocentric velocity was determined as 23.3 km/s. Stream 61.6.10 was active during June 15–18 from a radiant at a = 275.2°, d = −24.5°. The geocentric velocity was determined as 31.1 km/s.121 Z. Sekanina (1973) noted that the 1961–1965 session of the Radio Meteor Project, which used radio equipment at Havana, Illinois (USA), revealed several clusters of radiants along the ecliptic. He referred to one of these as “The Great Cluster.” Sekanina wrote, “ The highest concentration of possibly related streams was detected in a huge area of the sky 120° wide in right ascension and almost 30° in declination.” He gave the center a = 290°, d = −15°. He continued, “The streams of this cluster do not seem to be so rich as, for example, the Taurids or the Piscids, so the high concentration of the related streams does not mean any major concentration of individual meteor radiants. Rather, the Great Cluster appears to be an extensive area of activity with a number of local radiation centers.” Sekanina said the core of the Great Cluster was identical to Hoffmeister’s “Scorpius-Sagittarius System.” 122 Although Sekanina included 11 streams in his Great Cluster, two of these were observed in January and were considered closely related to the May– June streams, while another was the Alpha Capricornids, which will be handled separately in this book under Chap. 8 . Table 7.1 compares the primary active radiants as published by Hoffmeister, Sekanina (1973), and Sekanina (1976), and reveals little similarity between these three studies. This indicates that the distribution of meteors within each stream is apparently not homogenous, probably as a result of perturbations by Jupiter, which would act to disperse and clump different portions of each stream, explaining why certain radiants do not always appear to be active every year. Scorpiid-Sagittariid Complex: Antihelion 131

Table 7.1 Radiants of the Scorpiid-Sagittariid Complex Hoffmeister123 Sekanina (1973)124 Sekanina (1976)125 l (°) a (°) d (°) l (°) a (°) d (°) l (°) a (°) d (°) 34.3 232.6 −21.6 27.1 232.1 −16.0 57.1 254.0 −25.0 41.6 246.1 −17.5 51.8 250.1 −22.4 57.6 256.2 −12.8 48.8 235.5 −23.0 56.2 252.3 −16.9 72.9 247.2 −14.9 54.1 245.9 −20.4 65.9 243.4 −10.8 85.5 269.1 −22.8 57.7 254.2 −19.1 72.4 262.5 −19.8 90.4 282.2 −25.2 62.2 247.9 −19.9 86.7 277.8 −25.3 92.3 292.4 −13.6 67.4 254.7 −24.5 106.9 297.6 −18.7 98.7 274.3 −20.7 72.0 266.8 −23.2 167.7 335.6 −1.7 99.5 289.7 −26.1 77.8 263.2 −28.3 180.6 349.6 +2.9 109.5 310.6 −14.7 82.6 271.6 −24.9 86.6 279.8 −22.8 102.4 296.1 −19.8 107.2 298.0 −21.2 114.7 299.6 −17.0 124.1 310.7 −11.7

Observations of meteors from the entire complex were reported on a couple of occasions during the 1970s. The 1971 October issue of Meteor News contained observations by seven observers from the United States and Australia. From 1971 June 15 to 21, rates rose slowly to a maximum of 8 per hour, then rapidly fell off during June 22–27 to values of 0–1 per hour.126 Coordinated observations of individual radiants are not common. The Western Australia Meteor Section reported a few observations of meteor showers within this complex during 1979 and 1980. J. Wood, the section’s director, reported that during 1979 May 16–27, observations were made of the “Eta Ophiuchids.”. Maximum came on May 19 when the ZHR reached about 2.5. The radiant was determined as a = 256°, d = −13°.127 Another shower from this complex was observed during 1979 May 17–26. Called the “Theta Ophiuchids,” it reached a maximum ZHR of about two on May 19 from a radiant at a = 254°, d = −25°. This same shower was observed again during 1980 May 23–24, but was labeled the “Xi Ophiuchids”. The maximum ZHR was near two on May 23 and the radiant was determined as a = 256°, d = −22°. 127 In addition, Wood said a shower referred to as the “Omega Scorpiids” is visible every year in Australia. Reaching maximum on June 4 from a = 240°, d = −22°, it is visible during May 24 to June 13. Wood claims the ZHR typically varies between 5 and 20.128 One of the potential associations suggested for at least some of the meteor streams in the Scorpiid-Sagittariid Complex is the lost periodic comet D/1770 L1 (Lexell). C. Messier (Paris, France) discovered this comet on 1770 June 14. The comet passed about 1.3 million miles from Earth on July 1, at which time Messier measured the coma as 2°23¢ in diameter, or nearly fi ve times the diameter of the full 132 7 June Meteor Showers moon! The comet passed perihelion on August 14 and was last detected on October 3. The fi rst person to show that the comet moved in an elliptical orbit was A. J. Lexell. Over the years, calculations by other astronomers have indicated an orbital period of 5.42–5.63 years.129 This comet was never seen again and calculations reveal that the comet passed only 0.0015 AU from Jupiter during 1779, which appears to have greatly increased the eccentricity of the comet’s orbit. E. I. Kazimirchak-Polonskaya and S. D. Shaporev (1976) said the comet could have been placed in an elliptical orbit with a period of 260 years or even a hyperbolic orbit. 130 According to J. G. Porter (1952), the probable date of maximum activity for a stream associated with comet Lexell would be July 5, with the radiant at a = 272°, d = −21°.131 Several astronomers have suggested radiants that were associated with comet Lexell. E. N. Kramer (1953) suggested that a meteor stream, designated “147” in his list, which was active on August 8 from a radiant at a = 305°, d = −17°, was associated with the comet.132 Nilsson suggested a radar stream that he designated 61.6.9, which he also called the “Ophiuchids.”133 Terentjeva (1968) suggested six of the minor radiants she had identi fi ed in 1966.134 Sekanina (1973) suggested two of the streams detected during the fi rst session of the Radio Meteor Project.135 No single orbit can represent the Scorpiid-Sagittariid Complex. Z. Sekanina (1976) analyzed the data from the 1968 to 1969 session of the Radio Meteor Project and published the largest set of orbits for then-active radiants, which were located in Ophiuchus (OPH), Scorpius (SCO), Sagittarius (SGR), and Capricornus (CAP). These are as follows:

w W (2000) i q e a S. May OPH 130.0 237.9 3.5 0.264 0.824 1.50 N. May OPH 308.3 58.3 13.5 0.283 0.807 1.46 c SCO 261.5 73.5 4.1 0.663 0.687 2.12 OPH 280.5 84.9 0.3 0.503 0.774 2.22 SCO-SAG 113.7 271.2 2.5 0.384 0.799 1.91 Sigma CAP 309.4 93.0 8.2 0.332 0.707 1.13 m SAG 263.5 99.2 1.5 0.665 0.642 1.86 c SAG 108.3 280.3 3.9 0.430 0.783 1.98 t CAP 311.3 110.1 4.5 0.272 0.792 1.31

The possible association is given as follows:

w W (2000) i q e a D/1770 L1 259.58 325.59 7.35 0.4581 1.0 ¥ June Scutids 133

June Scutids

The earliest evidence supporting this meteor shower comes from W. F. Denning’s “General Catalogue of Radiant Points of Meteoric Showers and of Fireballs and Shooting Stars Observed at More Than One Station” (1899). He listed two radiants detected by the Italian Meteoric Association that he referred to as the “Eta Serpentids.” The fi rst radiant, labeled “211-2”, was based on 20 meteors detected during 1869–1872 June 25–30 and indicated a radiant at a = 275°, d = −9°. The second radiant, labeled “211-3”, was based on 20 meteors observed during 1872 June 26 to July 11 and indicated a radiant at a = 273°, d = −2°.136 The next reference to this shower appears in the paper, “An Index to Southern Meteor Showers”, which was written by R. A. McIntosh (1935). Radiant number “191” was referred to as the “Eta Serpentids I” and was based on three visual radiants. The duration was given as June 25–30, during which time the radiant moved from a = 274°, d = −6° to a = 277°, d = −3°. C. Hoffmeister’s book Meteorströme (1948) listed fi ve observed radiants from this stream. The fi rst observation came on 1912 June 29 ( l = 97.0°), when several meteors were plotted from a = 281°, d = −3°. Two apparent observations were made in 1935, meteors were plotted on June 23 (l = 91.8°) from a radiant at a = 272°, d = −1° and on June 26 ( l = 94.6°) from a radiant at a = 277°, d = −10°. Another observation was made on 1936 June 25 (l = 93.0°), when meteors were plotted from a = 270°, d = +4°. The fi nal observation came on 1937 July 4 ( l = 101.6°), when a radiant at a = 276°, d = +4° was detected.137 During a computerized stream search among 2529 meteor orbits determined during the Harvard Meteor Project, B. A. Lindblad (1971) found a stream that he called the “Eta Serpentids.” Based on only two meteors that were photographed on 1954 June 25 and 1954 July 3, he gave the average radiant as a = 278°, d = −2°. He identi fi ed it with “Denning 211” and “McIntosh 191.”138 This meteor stream was detected during both sessions of the Radio Meteor Project (Havana, Illinois, USA), with the analysis being carried out by Z. Sekanina. During the 1961–1965 session, he isolated seven meteors from the period spanning June 17 to July 15. At the time of the nodal crossing on June 24.7 (l = 92.7°), the radiant was determined as a = 276.3°, d = −6.3°, while the geocentric velocity was 17.5 km/s.99 During the 1968–1969 session, Sekanina identi fi ed 32 meteors from this stream. The duration was given as June 2 to July 29. At the time of the nodal crossing on June 27.0 (l = 94.9°), the radiant was at a = 280.7°, d = +1.0°, while the geocentric velocity was given as 18.9 km/s. 40 During both sessions, the meteor stream was referred to as the “June Scutids.” Three orbits have been calculated for this stream. The orbit labeled “1954” is from Lindblad (1971). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). 134 7 June Meteor Showers

w W (2000) i q e a 1954 268.5 97.7 15.5 0.606 0.715 2.17 1961–1965 276.8 93.4 10.3 0.615 0.550 1.37 1968–1969 278.8 95.6 15.7 0.599 0.560 1.36

Daytime Beta Taurids

Duration: June 5 to July 18 (l = 75–116°) Maximum: June 28 (l = 96.7°) Radiant: a = 79°, d = +21° ZHR: Medium

Radiant Drift: a = +0.82°, d = +0.05° V G : 28 km/s

In the course of a study of 14 meteors photographed during 1938 and 1939, F. L. Whipple (1940) noted that the Taurids might produce a shower visible during the daylight hours of summer.139 A few years after Whipple’s comment, astronomers using the Jodrell Bank Experimental Station in England detected activity during 1947 June 20–27 from a radiant near within the range of a = 79–85°, d = +20–30°. The activity rate ranged from 20 to 30 radio meteors per hour.140 Apparent confi rmation of this stream came during 1948 June 24 to July 4, when the average radiant was determined as a = 90°, d = +26° and the hourly rate reached a high of 35 on July 3.141 These radio-echo studies were of a fairly low precision and, although the Beta Taurids were detected, it was not until 1950 that more precise details of the stream became available. During 1950 June 26 to July 4, the Jodrell Bank equipment again found the Beta Taurids. A. Aspinall and G. S. Hawkins (1951) analyzed the data and concluded that peak activity occurred on July 2 ( l = 99°) from an average radiant at a = 86.2°, d = +18.7°. They noted that the radiant seemed to move “at random from day to day in an area of sky 8° × 14° in Taurus.” The daily radiants of this stream remained less than 3° across until July 2 and 3, when the radiant diameter was 7° and 5°, respectively. The diameter was again less than 3° across on July 4.95 These same observations were also used by M. Almond (1951) to determine the fi rst orbit for this stream, which indicated a semimajor axis of 2.2 AU, a perihelion distance of 0.34 AU, and an inclination of 6°.142 Radar observations continued at Jodrell Bank during the next several years. From observations obtained during the period 1950–1952, Almond, K. Bullough, and Hawkins established the mean daily motion as +0.8° in a and +0.4° in d . 143 Bullough (1954) determined more re fi ned details of the shower by adding observations made in 1953. The daily motion was given as +0.67° in a and +0.44° in d . He described the Beta Taurids as “a rather weak stream with no peak of activity. The shower is active for about a week centered on a sun’s longitude of 97° to 98°.”144 Curiously, the 1953 data revealed a radiant diameter of 3–4° throughout the time of activity until July 2, when it increased to 8°… similar to what was observed in 1950. Finally, after 1958 studies had been conducted, G. C. Evans (1960) analyzed Daytime Beta Taurids 135 the Jodrell Bank radar studies made between 1950 and 1958 and concluded that maximum came when the solar longitude was 97.7°, and that the average radiant was then at a = 85.4°, d = +19.4°. The daily motion was determined to have averaged +0.57° ± 0.12° in a and +0.16° ± 0.22° in d . Evans described the shower maximum as “rather weak and broad.”145 The fi rst radar survey in the Southern Hemisphere occurred at Canterbury University College (Christchurch, New Zealand) during 1953. C. D. Ellyett and K. W. Roth (1955) delineated 21 shower radiants from this survey. Shower number “10” was detected during the period of June 17–26. The radiant ranged from 82° to 85° in a and +20–25° in d . The mean radiant was given as a = 84°, d = +23°. 120 C. S. Nilsson (1964) detected this stream, while analyzing data acquired during 1961 by the radar equipment at the University of Adelaide (South Australia, Australia). Only seven meteors were found, but the equipment was not in operation after June 19, so that this observation was that of the early part of the shower. The observed duration was June 12–18, and the radiant was at a = 75.5°, d = +20.3°. The geocentric velocity was determined as 27.0. Nilsson pointed out that his data showed signifi cant correlations between both the radiant position and geocentric velocity with time. He added that the “sign of the mean heliocentric latitude…is not signi fi cant, so the node marked as ascending is quite possibly a descending node, for at least part of the stream.”146 It was not until the studies of the Radio Meteor Project, at Havana, Illinois, USA, that the true extent of the Beta Taurids became known. Z. Sekanina (1973, 1976) found that the 1961–1965 data indicated a duration extending from June 12 to July 6. At the time of the nodal crossing on June 26.6 (l = 94.5°), the radiant was at a = 80.1°, d = +21.2° (2000). The geocentric velocity was determined as 28.2 km/s. The 1968–1969 data revealed a duration extending from June 5 to July 18. At the time of the nodal crossing on July 4.4 ( l = 102.0°), the radiant was at a = 84.7°, d = +23.6° (2000). The geocentric velocity was determined as 29.0 km/s.99, 147 The fi rst study revealed an orbit similar to those reported previously, while the second study showed both the w and W shifted by 180°—adding further strength to Nilsson’s observation that some of the stream’s orbit might be at its descending node when crossing Earth’s orbit during June and July. The Canadian Meteor Orbit Radar (CMOR) detected this stream during 2002– 2008. The analysis by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) revealed 1386 meteor orbits, which indicated a duration spanning June 20 to July 3 ( l = 89–101°). Maximum was attained on June 25 ( l = 94°), at which time the radiant was at a = 82.8°, d = +20.1°, and the geocentric velocity was determined as 26.8 km/s.18 The prediction published by Whipple in 1940 (see above) was mentioned by Almond (1951) when she calculated the fi rst orbit for the Beta Taurids during 1951. She said the Beta Taurids resembled the Taurids of October and November in velocity, semimajor axis, perihelion distance, and inclination, so that a relationship did seem possible. Nilsson (1964) and Sekanina (1973, 1976) independently noted that a relationship between the two streams was likely. In particular, Nilsson noted that the correlation of radiant position and geocentric velocity with time was also 136 7 June Meteor Showers present during the duration of the Taurids. Other researchers have pointed fi ngers at the stream’s long duration, fl at maximum, and diffuse radiant as other characteristics previously noted in the Taurids. The Taurids are believed to be a very old remnant of periodic comet 2P/Encke. The orbit labeled “1950” is from Almond (1951). The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1950 244 278.9 6 0.34 0.85 2.2 1961 255.0 265.0 3.7 0.46 0.79 2.17 1961–1965 239.0 275.4 2.2 0.325 0.825 1.85 1968–1969 53.5 101.5 0.3 0.274 0.834 1.65 2002–2008 246.47 274.0 3.5 0.3833 0.802 1.94

The orbit of periodic comet 2P/Encke (labeled “2P”), as of its 2000 apparition, is given below. The orbit has changed little since its discovery in 1786.

w W (2000) i q e a 2P 186.48 334.60 11.76 0.3395 0.8469 2.22

Daytime Lambda Taurids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) recognized 13 new meteor showers after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired during 2002–2006. The Daytime Lambda Taurids were said to span the period of May 31–June 30 ( l = 70–98°), with its maximum coming on June 16 ( l = 85.5°) from a radiant at a = 56.7°, d = +11.5°. The geocentric velocity was given as 36.4 km/s, while the radiant’s daily motion was determined as +0.82° in a and +0.27° in d .92 Complete details were published in the journal Icarus during 2008.93 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as June 1–30 ( l = 71–98°). The date of maximum was given as June 16 (l = 86°), at which time the radiant was at a = 57.3°, d = +11.4°. The geocentric velocity was determined as 35.6 km/s. The radiant’s daily motion was determined as +0.85° in a and +0.33° in d .18 Daytime Lambda Taurids 137

w W (2000) i q e a 2002–2006 211.5 265.5 23.5 0.108 0.9316 1.6 2002–2008 211.69 266.0 22.6 0.1123 0.925 1.50

1. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226, 228, 232. 2. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975 Oct.), p. 597. 3. M. Buhagiar, Western Australia Meteor Section Bulletin , No. 160 (1981). 4. J. M. Trigo-Rodríguez, WGN, Journal of the International Meteor Organization, 21 (1993 Jun.), pp. 133–4. 5. J. A. Clegg, V. A. Hughes, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society, 107 (1947), pp. 374–5. 6. A. Aspinall, J. A. Clegg, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society, 109 (1949), pp. 353–4, 357–8. 7. M. Almond, Monthly Notices of the Royal Astronomical Society , 111 (1951), pp. 37–44. 8. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), p. 601. 9. A. Aspinall and G. S. Hawkins, Monthly Notices of the Royal Astronomical Society, 111 (1951), p. 21. 10. K. Bullough, Jodrell Bank Annals , 1 (1954 Jun.), p. 75. 11. T. W. Davidson, Jodrell Bank Annals , 1 (1956 Dec.), p. 120. 12. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 189. 13. Z. Sekanina, Icarus , 18 (1973), pp. 256, 259, 267. 14. Z. Sekanina, Icarus , 27 (1976), pp. 278, 294. 15. M. Almond, Monthly Notices of the Royal Astronomical Society , 111 (1951), p. 41. 16. D. K. Yeomans, The Astronomical Journal , 101 (1991 May), pp. 1920–8. 17. D. I. Steel, WGN, Journal of the International Meteor Organization , 20 (1992 Feb.), pp. 20–2. 18. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 19. B. G. Marsden, International Astronomical Union Circular , No. 7832 (2002 Feb. 18). 20. B. G. Marsden and D. A. J. Seargent, Minor Planet Electronic Circular, No. 2002-E25. 21. K. Ohtsuka, S. Nakano, and M. Yoshikawa, Publications of the Astronomical Society of Japan , 55 (2003 Feb. 25), pp. 321–4. 22. K. Simmons, Meteor News , No. 7 (1971 Aug.), p. 6. 23. J. West, Meteor News , No. 18 (1973 Oct.), p. 2. 24. Y. Fujiwara, M. Ueda, M. Sugimoto, T. Sagayama, S. Abe, Earth, Moon, and Planets , 95 (2004 Dec.), p. 598. 25. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 76 (1916 Supplement), pp. 740–3. 26. C. P. Olivier, Monthly Notices of the Royal Astronomical Society , 77 (1916 Nov.), p. 73. 27. F. W. Smith, Monthly Notices of the Royal Astronomical Society , 93 (1932 Dec.), pp. 156–8. 28. C. P. Olivier, Publications of the Leander McCormick Observatory , 5 (1935), p. 22. 29. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923 Nov.), p. 52. 30. I. Yamamoto, The Observatory , 45 (1922 Mar.), p. 82. 31. W. F. Denning, The Observatory , 45 (1922 Mar.), p. 83. 32. A. King, The Observatory , 50 (1927 Nov.), p. 361. 33. A. King, The Observatory , 52 (1929 Jan.), p. 29. 34. A. King, The Observatory , 51 (1928 Jan.), p. 25. 35. E. F. Turco, Review of Popular Astronomy , 62 (1968 Oct.), p. 7. 36. D. Swann, Meteor News , No. 53 (1981 Apr.), p. 2. 37. D. Conger, Flower Observatory Reprint , No. 155, p. 16. 138 7 June Meteor Showers

38. G. Becker and M. Adams, Meteor News , No. 3 (1970 Oct.), p. 2. 39. Z. Sekanina, Icarus , 18 (1973), pp. 257, 259. 40. Z. Sekanina, Icarus , 27 (1976), pp. 279, 294. 41. B. G. Marsden, International Astronomical Union Circular , No. 6954 (1998 Jun. 27). 42. P. G. Brown and W. K. Hocking, International Astronomical Union Circular , No. 6966 (1998 Jul. 4). 43. J. Rendtel, R. Arlt, and V. Velkov, WGN, Journal of the International Meteor Organization , 26 (1998 Aug.), pp. 165–72. 44. K. Fox, Asteroids, Comets, Meteors II. eds. H. Rickman and C.-I. Lagerkvist, Uppsala: University of Uppsala (1986), pp. 523–5. 45. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 88, 91, 121–3, 126. 46. G. W. Kronk, Cometography , volume 2. United Kingdom: Cambridge University Press (2009), pp. 336–7. 47. G. V. Zhukov, M. G. Ishmukhametova, E. D. Kondrat’eva, and V. S. Usanin, Kazanskii Gosudarstvennyi Universitet. Uchenye Zapiski, Seriya Fiziko-Matematichaskie Nauki , 153 (2011), pp. 141–9. 48. P. Jenniskens, Meteor Showers and their Parent Comets . United Kingdom: Cambridge University Press (2006), p. 396. 49. Gervase of Canterbury, The Historical Works of Gervase of Canterbury, volume 1, edited by William Stubbs. London: Longman & Co. (1879), p. 276. 50. J. B. Hartung, Lunar and Planetary Institute Contribution , No. 259 (1976), p. 43. 51. J. B. Hartung, Lunar and Planetary Institute Contribution , No. 765 (1991), p. 87. 52. A. W. Harris, Bulletin of the American Astronomical Society , 24 (1992), p. 952. 53. P. Withers, Meteoritics & Planetary Science , 36 (2001 Apr.), pp. 525–9. 54. F. K. Duennebier, Y. Nakamura, G. V. Latham, and H. J. Dorman, Science , 192 (1876 Jun. 4), pp. 1000–2. 55. A. K. Terentjeva, Physics and Dynamics of Meteors. Edited by L. Kresák and P. M. Millman. Dordrecht: D. Reidel (1968), pp. 412, 415. 56. M. Langbroek, WGN, Journal of the International Meteor Organization, 24 (1996 Aug.), pp. 115–18. 57. G. Zay and R. Lunsford, WGN, Journal of the International Meteor Organization, 24 (1996 Aug.), p. 118. 58. G. Zay and R. Lunsford, WGN, Journal of the International Meteor Organization, 24 (1996 Oct.), pp. 152–3. 59. R. Arlt, WGN, Journal of the International Meteor Organization , 24 (1996 Oct.), pp. 152–3. 60. http://www.imonet.org/radiants/ 61. K. Nakamura, Monthly Notices of the Royal Astronomical Society, 91 (1930 Nov.), pp. 204–6. 62. K. Komaki, Astronomische Nachrichten , 256 (1935 Jul. 30), pp. 233–4. 63. A. King, The Observatory , 54 (1931 Jul.), p. 201. 64. I. Yamamoto, Monthly Notices of the Royal Astronomical Society , 91 (1930 Nov.), p. 209. 65. H. Lüthen, R. Arlt, and M. Jäger, WGN, Journal of the International Meteor Organization, 29 (2001), pp. 16, 20. 66. R. B. Southworth and G. S. Hawkins, Smithsonian Contributions to Astrophysics , 7 (1963), pp. 271, 274, 280. 67. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 19, 23. 68. B. G. Marsden, International Astronomical Union Circular , No. 2672 (1974 May 21). 69. B. G. Marsden, International Astronomical Union Circular , No. 2676 (1974 Jun. 5). 70. B. Matous, Meteor News , No. 33 (1976 Oct.), p. 3. 71. J. West and C. Smith, Meteor News , No. 37 (1977 Aug.), p. 11. 72. B. Matous and N. W. McLeod, III, Meteor News , No. 38 (1977 Oct.), p. 7. 73. F. Roy, Meteor News , No. 47 (1979 Oct.), p. 7. 74. J. West and M. Zalcik, Meteor News , No. 58 (1982 Jul.), p. 9. Daytime Lambda Taurids 139

75. D. Swann and B. Katz, Meteor News , No. 66 (1984 Jul.), p. 7. 76. H. Lüthen, R. Arlt, and M. Jäger, WGN, Journal of the International Meteor Organization, 29 (2001), pp. 24–5. 77. P. Jenniskens, M. Phillips, R. Morales, and B. Grigsby, Central Bureau Electronic Telegram, No. 2817 (2011 Sep. 11). 78. H. Lüthen, R. Arlt, and M. Jäger, WGN, Journal of the International Meteor Organization, 29 (2001), p. 26. 79. S. Dvorak, Sky & Telescope , 32 (1966 Oct.), p. 237. 80. K. B. Hindley, Journal of the British Astronomical Association , 79 (1969), p. 480. 81. K. B. Hindley, Journal of the British Astronomical Association , 79 (1969), pp. 481–4. 82. Meteor News , No. 8 (1971 Oct.), p. 6. 83. Meteor News , No. 13 (1972 Oct.), p. 9. 84. Meteor News , No. 27 (1975 Aug.), p. 2. 85. Meteor News , No. 28 (1975 Oct.), p. 4. 86. J. West, Meteor News , No. 51 (1980 Oct.), p. 5. 87. D1899, p. 273. 88. R. Arlt, WGN, Journal of the International Meteor Organization, 23 (1995 Aug.), pp. 105–9. 89. M. Weber, WGN, Journal of the International Meteor Organization, 24 (1996 Oct.), pp. 150–2. 90. M. R. Kidger, WGN, Journal of the International Meteor Organization , 28 (2000), pp. 171–6. 91. A. F. Cook, Evolutionary and Physical Properties of Meteoroids, Proceedings of IAU Colloq. 13, held in Albany, NY, 14–17 June 1971. Edited by C. L. Hemenway, P. M. Millman, and A. F. Cook. National Aeronautics and Space Administration SP 319, 1973. pp. 183, 187, 190. 92. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Central Bureau Electronic Telegram , No. 1142 (2007 Nov. 17). 93. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 330. 94. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), pp. 318–19. 95. A. Aspinall and G. S. Hawkins, Monthly Notices of the Royal Astronomical Society, 111 (1951), p. 22. 96. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 188. 97. N1964, pp. 226–8, 242. 98. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), pp. 597, 604. 99. Z. Sekanina, Icarus , 18 (1973), pp. 256, 259. 100. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2, 76. 101. Meteor News , No. 7 (1971 Aug.), p. 6. 102. A. A. Weiss, Monthly Notices of the Royal Astronomical Society , 120 (1960), pp. 397, 400. 103. J. Wood, Personal Communication (1986 Oct. 15). 104. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 172. 105. R. Lunsford, WGN, Journal of the International Meteor Organization , 32 (2004 Jul.), p. 81. 106. W. F. Denning, The Observatory , 2 (1878 Jul.), pp. 90–3. 107. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 44 (1884 Apr.), p. 300. 108. W. F. Denning, The Observatory , 7 (1884 May), pp. 136–7. 109. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), pp. 425–6. 110. W. Doberck, Astronomische Nachrichten , 140 (1896 Jun. 15), pp. 375–8. 111. H. Corder, Memoirs of the British Astronomical Association , 6 (1898), p. 44. 112. A. S. Herschel, Memoirs of the British Astronomical Association , 9 (1901), p. 16. 113. E. J. Öpik, Harvard College Observatory Circular , No. 388 (1934), pp. 35, 37. 114. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), pp. 711, 714–15 115. R. B. Southworth and G. S. Hawkins, Smithsonian Contributions to Astrophysics , 7 (1963), p. 271. 140 7 June Meteor Showers

116. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 8. 117. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 19. 118. A. K. Terentjeva, Rezultaty Issledovani MGP , No. 1 (1966), pp. 107, 109. 119. A. K. Terentjeva, Physics and Dynamics of Meteors. Symposium no. 33 held at Tatranska Lomnica, Czechoslovakia, 4–9 September 1967. International Astronomical Union. Symposium no. 33, Edited by L. Kresak and P. M. Millman. Dordrecht: D. Reidel (1968), pp. 412, 415. 120. C. D. Ellyett and K. W. Roth, Australian Journal of Physics, 8 (1955 Sep.), p. 396. 121. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 226–7, 232. 122. Z. Sekanina, Icarus , 18 (1973), pp. 270, 273. 123. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 139. 124. Z. Sekanina, Icarus , 18 (1973), pp. 256–7, 259–60. 125. Z. Sekanina, Icarus , 27 (1976), pp. 277–80. 126. Meteor News, No. 8 (1971 Oct.), p. 7. 127. J. Wood, Personal Communication (1986 Oct. 15). 128. J. Wood, Personal communication (1985 Oct. 24). 129. G. W. Kronk, Cometography , volume 1. United Kingdom: Cambridge University Press (1999), pp. 447–51. 130. E. I. Kazimirchak-Polonskaya and S. D. Shaporev, Soviet Astronomy, 20 (1976 Nov.–Dec.), pp. 743–4. 131. J. G. Porter, Comets and Meteor Streams . London: Chapman and Hall (1952), p. 92. 132. E. N. Kramer, Izvestiya Astronomicheskoj Observatorii Odessa , 3 (1953), p. 163. 133. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 237–9. 134. A. K. Terentjeva, Physics and Dynamics of Meteors. Symposium no. 33 held at Tatranska Lomnica, Czechoslovakia, 4–9 September 1967. International Astronomical Union. Symposium no. 33, Edited by L. Kresák and P. M. Millman. Dordrecht: D. Reidel (1968), p. 419. 135. Z. Sekanina, Icarus, 18 (1973). 136. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 272. 137. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 202, 222, 225, 235. 138. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 21. 139. F. L. Whipple, Proceedings of the American Philosophical Society , 83 (1940), p. 711. 140. J. A. Clegg, V. A. Hughes, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society , 107 (1947), pp. 375–7. 141. A. Aspinall, J. A. Clegg, and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society , 109 (1949), pp. 357–8. 142. M. Almond, Monthly Notices of the Royal Astronomical Society , 111 (1951), p. 38. 143. M. Almond, K. Bullough, and G. S. Hawkins, Jodrell Bank Annals , 1 (1952 Dec.), p. 20. 144. K. Bullough, Jodrell Bank Annals , 1 (1954 Jun.), pp. 75, 94. 145. G. C. Evans, Jodrell Bank Annals , 1 (1960 Nov.), p. 284. 146. C. S. Nilsson, Australian Journal of Physics , 17 (1964), pp. 226, 232, 245. 147. Z. Sekanina, Icarus , 27 (1976), p. 280. Chapter 8

July Meteor Showers

c Andromedids

S. Molau and J. Rendtel (2009) discovered this meteor shower during an analysis of more than 450,000 video meteors recorded by the International Meteor Organization’s Video Meteor Network. They found 491 video meteors that indicated a duration of July 5–17 (l = 102–114°) and a maximum on July 13 (l = 110°), at which time the radiant was at a = 32.4°, d = +48.4°. The radiant drift was determined as +1.0° in a and +0.4° in d per day.1 The database used by Molau and Rendtel had expanded by 2012 and the International Meteor Organization created a website containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. Stream number 105 is called the “c Andromedids” and is based on 1856 meteors. The duration is given as June 24 to July 21 (l = 92–118°), while maximum occurs on July 13 (l = 110°) from a radiant at a = 32.6°, d = +47.5°. The radiant drift was determined as +1.2° in a and +0.4° in d per day.2 The only photographic meteor located that might be a member of this stream is trail number 8079, which was detected by multiple cameras during the Harvard Meteor Project on 1953 July 16. It came from a radiant at a = 24°, d = +40° and had a geocentric velocity of 57.8 km/s.3 The orbit of this meteor is given below.

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 141 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_8, © Springer Science+Business Media New York 2014 142 8 July Meteor Showers

w W (2000) i q e a 8079 122 115 128 0.85 0.56 1.91

Delta Aquariids

Northern Branch Duration: July 16 to September 10 (l = 114–167°) Maximum: August 13 (l = 139°) Radiant: a = 344°, d = +2° ZHR: 3

Radiant Drift: a = +0.72°, d = +0.26° V G : 37 km/s Southern Branch Duration: July 14 to August 23 (l = 112–150°) Maximum: July 29/30 (l = 126°) Radiant: a = 340°, d = −16° ZHR: 18

Radiant Drift: a = +0.78°, d = +0.3° V G : 41 km/s

During July and August, the Aquarid–Capricornid complex becomes active—a region which contains the northern and southern branches of the Delta Aquariids and Iota Aquariids, as well as several distinct radiants in Capricornus. The strongest activity emanates from near the star Delta Aquarii. What might be the earliest observation of this stream is published in the book, On Meteors in the Southern Hemisphere , which was written by E. Heis and G. Neumayer. They noted that 23 meteors were seen during August of 1858–1863 from a radiant at a = 337°, d = −10°. 4 The reason this “might” be an observation is because of ambiguity within the month, as the radiant does move. In addition, during mid-August, this position actually represents the Antihelion radiant. During 1869, J. F. J. Schmidt (Athens Observatory, Greece) published a list of meteor radiants that he had determined. He said a radiant at a = 333°, d = −14° was seen during the period of July 20–31. He listed the observation by Neumayer as possibly related.5 G. L. Tupman (Mediterranean Ocean) appears to have determined a couple of Delta Aquariid radiants during 1870. He noted active radiants at a = 340°, d = −14° on July 27 and a = 340°, d = −19° on July 28.6 T. H. Waller and A. S. Herschel brie ﬂ y discussed a radiant in Aquarius during 1875. They mentioned a meteor that was seen at several locations on 1874 August 10 and added that W. H. Wood (Birmingham) was able to use the observations to determine the height, position, and radiant. The radiant was given as a = 325°, d = −17°. Waller and Herschel noted that this was close to the position determined by Tupman, Schmidt, Heis, and Neumayer, “forming a distinct radiant-region in Aquarius along a part of the southern arc of the ecliptic at that season of the year.”7 The above observations clearly refer to the Southern Delta Aquariids, and W. F. Denning listed no fewer than 15 additional observations of this radiant by experienced observers during the remainder of the nineteenth century.8 Delta Aquariids 143

Although the Northern Delta Aquariids were not offi cially discovered until the 1950s, it should be pointed out that some nineteenth century observations do seem present. Denning made three apparent observations between 1879 and 1893, which he erroneously grouped with several additional radiants occurring between May and November to form a stationary shower called the “Beta Piscids.” The fi rst observation involved ten meteors seen during 1879 August 21–23, from an average radiant of a = 350°, d = 0°. Another observation was made during 1885 August 16–20, when seven meteors were seen from a = 345°, d = 0°. His fi nal nineteenth century observation came during 1893 August 13–16, when six meteors were seen from a = 347°, d = 0°. 9 Since the observed radiants involved small numbers of meteors, there was no inspiration for other observers to continue observations and there was no hint as to an association with the well–known Delta Aquarid shower. Observations of the Delta Aquariids continued into the twentieth century, but they mostly referred to the southern branch. As an example, English observers made quite extensive observations during 1922. A. G. Cook plotted 13 meteors during July 25, 28 and 31, which revealed an average radiant of a = 338°, d = −12° and, from Ashby, A. King plotted four meteors from a = 340°, d = −16° during July 30 and 31. 10 J. P. M. Prentice also detected the radiant, when he plotted 12 meteors from a = 341°, d = −15° during July 30 to August 1.11 Among the 75 additional radiants recognized by these three observers during July and August of that year, only one observation of the Northern Delta Aquariids seems present. That observation was made by Cook during August 17, 19, and 20, when four meteors were plotted from a = 338°, d = 0°. 12 The fi rst signifi cant study of the Delta Aquariid stream was published in 1934. R. A. McIntosh used the observations made by the New Zealand Astronomical Society during 1926–1933 to determine the daily motion of the radiant. In all, 44 radiants were utilized, with their original observers being McIntosh (Auckland), M. Geddes (Otekura), F. M. Bateson (Wellington), and A. Bryce (Hamilton). McIntosh concluded that activity from the shower is continuous from July 22 to August 9, with the radiant moving northeastward from a = 334.9°, d = −19.2° to a = 352.4°, d = −11.8° [ average daily motion +0.96° in a and +0.41° in d ]. McIntosh added that a sharp maximum occurs on July 28 (a = 340.5°, d = −17.0°), and a diagram included in his paper revealed the following visual hourly rates: 1 on July 22, 2 on July 25, 3 on July 26, 7 on July 27, 14 on July 28, 9 on July 30, 6 on August 2, and 1 on August 9.13 The radiant ephemeris clearly represents the Southern Delta Aquariids and no mention was made as to a northern branch. During 1935, McIntosh published his classic paper “An Index to Southern Meteor Showers,” but among the 320 radiants listed, there are no convincing candidates for the Northern Delta Aquariids. C. Hoffmeister and his fellow German observers obtained good observations of the southern shower between 1908 and 1938. In evaluating the data, Hoffmeister found seven activity centers. Five of these were based on 2–3 observed radiants each, but it was clear to Hoffmeister that maximum occurred on August 3 (l = 130°). He based this statement on two well–established activity centers: one based on seven visual radiants that occurred on August 2 (l = 128.4°) from a = 342.4°, d = −17.7°, 144 8 July Meteor Showers and a second based on ten radiants that occurred on August 6 (l = 132.6°) from a = 341.5°, d = −17.2°.14 Hoffmeister does seem to have isolated a radiant with the characteristics of the northern branch as well. In a table listing 238 radiants observed on at least four occasions, there is a radiant at a = 349°, d = +1°. It was based on fi ve visual radiants and the average date was given as August 13 (l = 139°).15 The fi rst radio–echo observations of the Delta Aquariids were made by equipment at Ottawa, Canada, during 1949, when Canadian astronomer D. W. R. McKinley detected both branches of the stream. In the 1954 paper that appeared in the Astrophysical Journal , McKinley revealed how his velocity and radiant determinations on 1949 July 26–29, revealed two distinct radiants: a very strong one at a = 339° ± 2°, d = −17° ± 2° and a very weak one at a = 340° ± 5°, d = 0° ± 5°. The velocities of the two radiants were 40.20 ± 0.1 and 41.0 ± 0.5 km/s, respectively. Unfortunately, orbits were not determined for the two radiants, and the northern radiant was not recognized as being associated with the Delta Aquariid shower.16 Radio–echo observations of this shower were also made by equipment operating at Jodrell Bank Experimental Station (Lower Withington, Cheshire, England) during 1949–1951. The most reliable data was accumulated during the last days of 1950 July. G. S. Hawkins and M. Almond gave the weighted mean date of activity as July 28 ( l = 124.5°), at which time the hourly radio–echo rate peaked at 38. The radiant possessed a diameter of 3° and an average position of a = 339°, d = −14°. The 1949 observation occurred on July 29 ( l = 125.8°). Although an hourly rate of 24 was obtained, no further details could be established. Radio–echo rates reached 41 on 1951 July 27 (l = 123.4°). 17 The radiant determination was not considered to be of the highest quality, with the diameter being given as 6° and the position being estimated as a = 336°, d = 0°. The only hint that the 1951 shower might have been identical to the Southern Delta Aquariid radiant was its date of maximum activity. The actual position lies closer to the where the radiant of the Northern Delta Aquariids might lie at the end of July. During 1952, Almond made a specifi c attempt to determine the velocity of the Delta Aquariid meteors. Using a “more selective beamed aerial,” 32 probable members of the stream were detected and a mean velocity of 40.5 ± 2.7 km/s was revealed. In addition, maximum was found to have occurred on July 28 from a = 340°, d = −15°. When the radiant and velocity were combined they allowed the fi rst accurate determination of the orbit of the Delta Aquariids. From this orbit, Almond noted a strong similarity between the orbit of this stream and that of the Daytime Arietids of June (see Chap. 6). Most notable were the similar values determined for the perihelion distance, eccentricity and longitude of perihelion. The discrepancies in the argument of perihelion and ascending node were explained as due to the diffuse nature of both streams. “As the inclination of the orbit plane of the d Aquariids is 24°,” she explained, “the stream would be 0.31 AU away from the earth at its second approach on June 9. From the duration of 16 days observed for the daytime Arietids the width of the stream must be at least 0.27 AU, and there is also evidence that the Delta Aquariid shower lasts 18 days in the southern hemisphere. Hence, the system of orbits is so broad, it seems probable that the two showers are connected and are produced by one extended stream.”18 Delta Aquariids 145

Using over 2000 photographic meteor orbits determined during the Harvard Meteor Project of 1952–1954, F. W. Wright, L. G. Jacchia, and F. L. Whipple pointed out the mounting evidence supporting the existence of a northern branch of the Delta Aquariids. This marked the fi rst time the northernmost radiant had been recognized as being associated with the Delta Aquariid shower, and the authors offered the fi rst hint as to the complex evolution of the stream. They noted that the northern and southern branches were “symmetrical with respect to the ecliptic, or to Jupiter’s orbit....” Concerning the suggested link between the Southern Delta Aquariids and the Daytime Arietids of June, it was noted that the spread of about 134° between the nodes of the two streams “could have been caused by continual perturbations by Jupiter.”19 Several astronomers analyzed the photographic data accumulated during the Harvard Meteor Project during the 1960s and 1970s; however, B. A. Lindblad (1971) offered the most complete analysis. For the Southern Delta Aquariids he isolated 13 meteors which indicated a duration of July 21 to August 8. The stream’s date of nodal passage was given as July 31, at which time the radiant was at a = 340°, d = −16°.20 A second study by Lindblad utilized 11 precisely calculated meteor orbits. The study began with a D–criterion of 0.15, but he noted that when a more strict value of 0.10 was used the Southern Delta Aquariids still remained intact. He concluded that it “indicates a high degree of orbit similarity....”.21 For the Northern Delta Aquariids, Lindblad isolated nine photographic orbits. The indicated duration was August 5–25. The nodal passage came on August 14 (l = 140.5°), at which time the radiant was at a = 347°, d = +1°. 22 Although the radio–echo method had actually produced details about the Delta Aquariid streams as early as 1949, radar studies entered a new age of importance during the 1960s. The fi rst major study was conducted in 1960 by researchers at the Kharkov Polytechnical Institute (Ukraine). B. L. Kashcheyev and V. N. Lebedinets obtained 151 radio meteor orbits from the Southern Delta Aquariids during July 14 to August 14. When at maximum the average radiant was at a = 341.2°, d = −16.4° and the solar longitude was 126.7°. They gave the daily motion of the radiant as +0.85° in a and +0.35° in d , and determined an average orbit which revealed a semimajor axis of 2.04 AU. The Northern Delta Aquariids were also detected. The 50 radio–meteors observed revealed a duration extending from July 7 to August 14. The date of the nodal passage was August 1 (l = 127.7°), at which time the radiant was at a = 336.8°, d = −4.9°. The radiant’s daily motion was given as +0.9° in a and +0.3° in d . 23 Although many of the details determined for the Northern Delta Aquariids matched those of other researchers made both prior to and after the Kharkov study, several aspects indicate the data may have been contaminated by other meteor showers active at the time. Most notable are the dates of earliest activity and nodal passage, both of which occur at least 10 days prior to that generally accepted for this shower. In addition, the argument of perihelion is the highest ever revealed for this stream’s orbit, with a value nearly 15° above that given in most other orbital determinations. The next signifi cant radar survey used radio equipment at the University of Adelaide (South Australia, Australia) during 1961. C. S. Nilsson (1964) analyzed 146 8 July Meteor Showers the data and found 48 radio meteors during the period of July 23–August 4 from an average radiant of a = 339.4°, d = −17.3°. The date of maximum was given as July 28 (l = 125.8°) and the radiant’s daily motion was determined as +0.9° in a and +0.2° in d , while the stream’s average orbit had a semimajor axis of 2.33 AU. Nilsson tried to be as strict as possible in his evaluation of the data. He noted, “there are several distinct radiants…in the vicinity of the main Delta Aquariid radiant. It is not unlikely that some of these have contributed to the data used in previous determinations of the Delta Aquariid radiant.”24 Although Nilsson did not speci fi cally recognize the Northern Delta Aquariids, he did isolate four meteors during the period of August 20–23. The average radiant was given as a = 352.7°, d = +6.3°. It should be noted that the radar equipment at Adelaide did not operate during August 5–15, so that the true maximum of the northern branch would probably have been missed. As can be seen in the “Orbit” section below, Nilsson’s orbit bears a striking resemblance to orbits determined by other astronomers for the northern shower. The Radio Meteor Project was the most elaborate of the 1960s radio-echo surveys. It used radio equipment in Havana, Illinois (USA) and was conducted in two sessions: 1961–1965 and 1968–1969. Z. Sekanina analyzed both sessions. During the 1961–1965 session, Sekanina (1970) found the Southern Delta Aquariids to have a duration of July 16 to August 14. The nodal passage came on July 30.9 ( l = 127.3°), at which time the radiant was at a = 342.2°, d = −16.9°. The geocentric velocity was 38.7 km/s. He pointed out that the stream’s distribution “could be matched by no single model curve” and he suggested that the stream “might be composed of two constituents: a very compact fi lament and a more dispersed stream.” The Northern Delta Aquariids were given a duration of July 26 to August 27. Their nodal passage came on August 13.0 (l = 139.8), at which time the radiant was a = 344.0°, d = +0.3°. The geocentric velocity was determined as 35.3 km/s. Sekanina considered this stream “to be somewhat looser than the southern branch… and defi nitely less conspicuous and less populated.”25 During the 1968–1969 session, Sekanina (1976) gave the duration of the Southern Delta Aquariids as July 14 to August 18. The nodal passage was given as July 29.3 (l = 125.7°), while the average radiant was a = 341.8°, d = −15.9°. The geocentric velocity was determined as 38.2 km/s. For the Northern Delta Aquariids, the duration was given as July 28 to September 10. The nodal passage came on August 14.9 ( l = 141.7°), at which time the radiant was at a = 345.7°, d = +4.8°. The geocentric velocity was determined as 31.1 km/s.26 Following the earliest computations of orbits for the Southern Delta Aquariids came the studies of physical and evolutionary developments of the meteor stream. A. K. Terentjeva (1963) examined the structure of the stream and noted that the small perihelion distance (given as 0.06 AU) would bring the temperature of the individual meteors up to 1,100° K, which is the melting point of silicates. Terentjeva suggested this accounted, “for the peculiar general appearance of the shower meteors which are sharp, show no wakes, and give off no sparks.” Several visual and photographic radiants were studied and the northern and southern radiants were clearly apparent, with their average radiants for July 29 being a = 334.5°, d = −5.4° Delta Aquariids 147 and a = 338.5°, d = −16.9°, respectively. The daily motion of the Northern Delta Aquariids was given as +0.85° in a and +0.35° in d , while the Southern Delta Aquariids’ motion was +0.88° in a and +0.36° in d . Finally, it was noted that the orbits of the two streams were “symmetrical relative to the plane of Jupiter’s orbit.” She added, “This may be the effect of perturbations.”27 S. E. Hamid and F. L. Whipple (1963) conducted another interesting study. It raised the importance of the Southern Delta Aquariid stream to a very high level as being a link to other meteor showers. It has already been noted that a strong link exists between this stream and the Daytime Arietid stream of June, but Hamid and Whipple gave evidence to suggest that the Quadrantids of January also formed from this stream. Taking members of both streams and subjecting them to secular perturbations, they found that the orbital planes and perihelion distances were very similar 1,300–1,400 years ago. They wrote, “The effects of Jupiter perturbations on i and q are quite remarkable,” and “it is possible that the two streams were derived from a single comet....” They added that despite the present differences in the duration and activity levels of the two showers, “the physical characteristics of the meteoroids belonging to the two streams appear to be similar, as judged by their light curves.”28 Some attempts have been made to identify this shower among ancient displays. C. P. Olivier suggested the fi rst possible link in his 1925 book Meteors . He believed the strong displays of 714 July 19 and 784 July 14 were possible early appearances of the Southern Delta Aquariids.29 Sekanina (1976) said the shower of 714 had been classi fi ed as a possible early appearance of the Perseids. He added that the most promising early appearance of the Southern Delta Aquariids was a shower that occurred in 1007, in which two independent Japanese sources describe the meteors as fl ying toward the north—a direction quite inappropriate for a description of the Perseids. Sekanina said this radiant would indicate a nodal regression of 0.8−1.3°/ century. 30 One very interesting fi nding about the Southern Delta Aquariids is the diameter of the radiant. Hoffmeister noted in his 1948 book Meteorströme that “the radiant is at times very diffuse” and he added that activity tended to be strong within an area 20° in diameter centered on the Southern Delta Aquariid radiant [perhaps including the two branches of the Iota Aquariid stream as well—Author ].14 Several Northern Hemisphere observers have arrived at a similar conclusion during this century; however, observers south of the equator have formulated a different conclusion. McIntosh was struck by the fact that the Southern Delta Aquariid radiant seemed fairly small, with New Zealand observers independently determining radiants quite close to one another and determining a radiant diameter of about one degree.31 From South Australia, Nilsson also noted the “particularly small” radiant diameter based on his radio–echo survey. Such a contrast between northern and southern observations reveals what can happen to a radiant when zenithal attraction comes into play. For the Southern Hemisphere observers the radiant is almost directly overhead, while northern observations tend to occur when the radiant is only about 20° above the horizon. McIntosh provided other insights into this behavior of the Southern Delta Aquariids. He wrote, “The fact that for a period of nineteen days the radiants 148 8 July Meteor Showers

Table 8.1 Southern delta Aquariid radiant ephemeris Date RA (°) Dec (°) Jul. 22.0 334.9 −19.2 Jul. 24.0 336.8 −18.4 Jul. 26.0 338.6 −17.7 Jul. 28.0 340.5 −17.0 Jul. 30.0 342.4 −16.3 Aug. 1.0 344.3 −15.9 Aug. 3.0 346.0 −14.8 Aug. 5.0 347.8 −14.0 Aug. 7.0 349.7 −13.1 Aug. 9.0 351.5 −12.2

observed are clustered about a fi xed point in space, while in the time that point moved through an arc of 17° in the sky, clearly establishes that the radiant-point of the Delta Aquariid stream moves in the manner required by theory.” He added that this was the fi rst time this had been “proved observationally for the Delta Aquarids.” He provided a radiant ephemeris for 20 consecutive days. A truncated version of his ephemeris, covering every 2 days, is given in Table 8.1 . McIntosh determined that the Southern Delta Aquariids were active from July 22 to August 9, with maximum coming on July 28. He added that the maximum was sharp, climbing from a rate of 3 per hour on July 26, to 7 per hour on July 27, and then to 14 per hour on July 28. The decline was slower, with the shower still producing an hourly rate of 6 on August 2. McIntosh is also credited with calculating the fi rst orbit for the Southern Delta Aquariids, which is given with other orbits below.32 Visual observers acquired a number of observations of the Southern Delta Aquariids during the 1970s and 1980s, which provided new details on hourly rates and other aspects of this stream. M. Buhagiar (Western Australia, Australia) observed 8–12 meteors per hour during 10 h of observing on 1972 July 28/29 and 29/30, even though a full moon was present. 33 During 1973, visual rates reached 14.6 per hour on July 27/28, according to four observers in the United States, while Buhagiar detected 20 per hour on the same night from Western Australia.34 During 1974, ZHRs in the United States reached 12.5 ± 3.0 on July 29.4, while Buhagiar and R. Oates noted hourly rates of 37–44 meteors per hour on July 28 in Western Australia.35 Members of the Western Australia Meteor Section (WAMS) have had much success in observing the Southern Delta Aquariids. Section director J. Wood said a maximum ZHR of about 42 was observed on 1977 July 29, with an overall observed duration extending from July 23 to August 14. The radiant position at maximum was given as a = 339°, d = −15°. Maximum rates during 1979 were signi fi cantly lower, with a ZHR of about 17 occurring on July 28, from a radiant of a = 338°, d = −17°. The observed duration was July 20 to August 5. The shower’s 1980 appearance was hampered by a full moon on July 27. Subsequently, hourly rates Delta Aquariids 149 were signi fi cantly lower, with the shower’s maximum actually coming on August 3—the night of the last quarter moon. The ZHR reached about seven and the radiant was then a = 343°, d = −15°. The duration extended from July 18 to August 10.36 Observations of the Northern Delta Aquariid shower by the WAMS have revealed three puzzling facts: very low activity, an uncertain radiant location, and an earlier than usual date of maximum. In 1979, possible meteors from this shower were observed during July 27 to August 5. The maximum activity peaked on August 4 when the ZHR reached about 3, but the average radiant was then given as a = 328°, d = −3°—roughly 7° to the west of the expected position for that date. In 1980, meteors were observed from the shower during August 2–16. A maximum ZHR of about six came on August 4 (1 day after a fi rst quarter moon) from a radiant of a = 341°, d = −2°—roughly 6° east of the expected position for that date.36 Of course, both radiants were given dates of maximum activity which defi nitely contradicts the results of photographic and radar surveys, as well as the apparent visual observations of the past. It is interesting that an earlier maximum has also been noted in the United States by N. W. McLeod III (Florida). In an article published in Meteor News during 1984 April, McLeod stated that his observations since 1971 had revealed that maximum occurred at the same time as generally accepted for the Southern Delta Aquariids. He gave the Northern Delta Aquariid radiant as a = 326°, d = −7.6° for July 30, which is about 4° west of the expected position for that date.37 The minor controversy over the likely date of maximum for the Northern Delta Aquariids might have a simple explanation that points to a more complex structure for the Delta Aquariids as a whole. For the photographic meteors, the orbital inclinations tend to be 6–8° higher prior to August 10, than after that date. If this means that two different streams actually produce the overall Northern Delta Aquariid activity, then two different maximums might not be out of the question. On the other hand, if it is assumed that the inclination discrepancy among photographic meteors is due to a weak database, then the earlier, less supported maximum might simply re fl ect how easy it is to observe a weak meteor shower like the Northern Delta Aquariids during late July and early August, than during the time of the Perseid maximum in mid–August. A few studies were published during the 1980s, 1990s, and the early 2000s, which determined the observational characteristics of the two Delta Aquariid showers; however, A. Dubietis and R. Arlt (2004) used the largest dataset, which spanned several years. They used the International Meteor Organization’s Visual Meteor database for the period of 1997–2002. For the Southern Delta Aquariids, they extracted 6353 meteors spanning the period of July 5 to August 23 (l = 103– 150°), of which magnitude estimates were available for 5848 meteors. For the Northern Delta Aquariids, they extracted 4750 meteors spanning the period of July 13 to August 28 ( l = 110–156°), of which magnitude estimates were available for 4549 meteors. Two slightly different sets of characteristics were provided for the southern shower: one relied on Northern Hemisphere observations and the other relied on Southern Hemisphere observations. Since the radiant is at a higher eleva- tion for Southern Hemisphere observers, these details are provided. The duration of visibility was determined as July 14 to August 17, the date of maximum was July 31 ( l = 126.9°), the ZHR at maximum was about 18, and the population index was 150 8 July Meteor Showers r = 2.31. For the Northern Delta Aquariids, the duration of visibility was determined as July 21 to August 23, the date of maximum was August 4 (l = 131.8°), the ZHR at maximum was about 3, and the population index (r) is 2.66.38 Several orbits have been calculated for the Southern Delta Aquariids. The fi rst orbit calculated for this meteor stream was by McIntosh (1930), based on visual observations. It is labeled “1929”.39 Five years later, McIntosh (1935) calculated another orbit. This is labeled “1926–1933”, as he hoped to get a better average on the radiant by using multiple years. The fi rst elliptical orbit was calculated by Hoffmeister (1948). He indirectly arrived at a value of 34.64 km/s as the heliocentric velocity of the meteors. This orbit is labeled “1948”. The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1970). The orbit labeled “1968–1969” is from Sekanina (1976).

w W (2000) i q e a 1929 159.2 309.0 60.4 0.0331 1.0 ϱ 1926–1933 159.6 305.7 55.8 0.039 1.0 ϱ 1948 147.0 310.7 23.7 0.118 0.926 1.60 1960 151.1 307.4 28.4 0.08 0.96 2.04 1961 152.4 306.5 32.5 0.07 0.97 2.33 1961–1965 151.9 308.0 29.9 0.083 0.955 1.85 1968–1969 155.4 306.4 28.2 0.069 0.958 1.63

The 1960s and 1970s brought the ﬁ rst orbital determinations for the Northern Delta Aquariids from radar surveys. The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1970). The orbit labeled “1968–1969” if from Sekanina (1976).

w W (2000) i q e a 1961 328.2 149.0 22.4 0.11 0.93 1.56 1961–1965 324.5 140.5 16.0 0.132 0.927 1.82 1968–1969 323.2 142.4 19.2 0.169 0.866 1.26

Cassiopeiids

This is a complex, yet interesting meteor shower with an apparently long history, having been brought to wide-spread attention by J. F. J. Schmidt in an 1869 May issue of the Astronomische Nachrichten. Among the radiants listed was a shower observed by P. Tacchini (Italy) during 1868 July 20–26, with the meteors radiating from a = 6°, d = +59° ( l = 119–125°).5 Cassiopeiids 151

During the next decade, observations were reported by several observers, but, for the most part, the data is almost useless in trying to understand this shower. R. P. Greg (1872) listed a couple of interesting radiants, which might be associated with the Cassiopeiids. Analyzing meteor paths recorded by G. V. Schiaparelli and G. Zezioli during 1867–1870, he noted a radiant at a = 3°, d = +68° that was active on July 4 ( l = 104°). Analyzing meteor paths recorded by himself and A. S. Herschel during 1848–1871, he noted a radiant at a = 12°, d = +70° that was active during July 7 to August 4.40 W. F. Denning (1877) wrote a paper that was published in 1877 January that listed 51 radiants that his observations had revealed during 1876 April–December. The Perseid radiant was de fi ned by 43 recorded meteor paths, but the second highest number were the “Cassopieds I,” which was defi ned by 28 meteor paths during July 16 to August 14 ( l =116–143°). The radiant was determined as a –18°, d = +63°. Denning said they were very bright and rapid, “with streaks like Perseids….” The maximum came on July 24. 41 Greg (1877) suggested the observations of Herschel, Tacchini, Schiaparelli, Zezioli, and himself indicated a radiant at a = 12°, d = +64° was active during July 4 to August 4. He retained Denning’s designation of “Cassiopeids I.” Greg also noted a second radiant at a = 7°, d = +50° that was active during July 11 to August 20.42 During 1878, Denning provided several details about this meteor shower. He described two potential radiants observed in Cassiopeia during 1877. Both were believed to be related and were designated radiant 53 in his list. The fi rst was based on 11 meteor paths recorded during July 6–17, which indicated a radiant of a = 6°, d = +53°. He said the radiant was “exact” and said maximum came during July 12–17 ( l = 111–116°). The second radiant was based on nine meteor paths recorded during August 3–16 (l = 132– 145°), which emanated from a = 8°, d = +53°. They were described as “Swift, white meteors with streaks”. 43 Denning also analyzed the meteor paths recorded during 1872 by the Italian Meteoric Association. He said 15 meteors were detected during July 15 to August 2 ( l = 115–132°), which came from a radiant at a =8°, d = +54°. 44 The problem with these observations is that there is no real certainty that these radiants are actually one and the same. The concept of radiants moving from 1 day to the next had not yet been recognized, so it was assumed that a radiant could remain in the same place for months at a time. Perhaps the fi rst good determinations of the radiant came from E. F. Sawyer and N. de Konkoly during 1879–1881, when positions were given for periods of only 1–3 days. Sawyer (1879) recorded the paths of eight meteors on 1878 August 10 ( l = 139°) and noted a radiant at a = 8°, d = +55°. 45 De Konkoly presented a list of “probable” radiants that had been determined by observers in Hungary during 1871–1878. He noted positions of a = 357.0°, d = +65.7° during 1873 July 25–26 ( l = 124–125°), a = 1.0°, d = +66.8° during 1876 July 26–28 (l = 125–127°), and a = 7.0°, d = +58.8° during 1876 August 12–13 ( l = 141–142°). 46 Sawyer (1881) recorded fi ve “very bright, short, and rather slow” meteors from a = 5°, d = +57° on 1879 August 10–12 (l = 139–141°). Fourteen meteors emanated from a = 5°, d = +55° on 1880 August 8–9 (l = 137–138°). These were described as “quite bright, of medium length, and generally rapid with streaks.” Sawyer added that this was an “active shower.” Finally, he recorded six “very bright, short, and rapid” 152 8 July Meteor Showers

Table 8.2 Beta Cassiopeiid observations in 1929 Date RA (°) Dec (°) Jul. 26.74 356.9 +58.4 Jul. 27.73 359.9 +59.4 Jul. 29.73 358.9 +60.4 Jul. 30.73 0.9 +60.9 Jul. 31.77 2.9 +60.9

meteors from a = 5°, d = +75° during 1880 August 8–9 (l = 137–138°).47 Denning (1884) fi nally provided a short-duration radiant during an investigation of fi reballs, giving a position of a = 4°, d = +56° for August 9–11.48 During the remainder of the nineteenth century, more observers concentrated on determining radiants based on shorter durations. H. Corder (1897) reported that fi ve meteors were recorded during 1895 July 21–29 from a radiant at a = 8°, d = +51°. He referred to them as the “Cassiopeids” and described them as swift.49 Two observations of the “Cassiopeids” were reported in the 1898 issue of the Memoirs of the British Astronomical Association . Corder plotted six “quick” meteors from a radiant at a = 15°, d = +63° during 1896 August 4–14, while J. A. Hardcastle plotted four “quick” meteors from a radiant at a = 15°, d = +62° during 1896 August 10–11. 50 Corder (1899) plotted ten “quick” meteors from a = 16°, d = +56° on 1897 August 2.51 W. E. Besley (Westminster, England) observed 11 “swift” meteors from a radiant at a = 2°, d = +50° on 1898 August 11. 52 Denning (1899) collected all radiants that had been published during the nineteenth century and published his “General Catalogue of Radiant Points.” The catalog contained 278 meteor showers, of which four were active during July and August in Cassiopeia: Alpha Cassiopeiids, Pi Cassiopeiids, Delta Cassiopeiids, and Cassiopeiids. 53 Observations continued into the twentieth century, with almost every list of observations including at least one radiant in the Cassiopeia region. As an example, D. Eginitis (1904) made extensive observations of meteors at the National Observatory (Athens, Greece) during 1902. He determined two radiants for the “Alpha Cassiopeids.” Five meteors were plotted from a radiant at a = 5°, d = +60° on July 25, while three meteors were plotted from a radiant at a = 5°, d = +59° on July 26. 54 Perhaps the fi rst coordinated survey of this meteor shower was conducted by N. N. Sytinskaja (1930). He published the results of observations made during 1929 at Tashkent Observatory. He observed the shower for 5 days and recorded the paths of 273 meteors. A total of 83 meteors came from the “Beta Cassiopeids.” He described the meteors as “faint and very swift” and provided hourly rates of 19 on July 26, 15 on July 27, 12 on July 29 and 30, and 7 on July 31. Sytinskaja provided radiant positions for these 5 days, which gave the fi rst hint of the daily motion of the radiant. This data is in Table 8.2 . 55 Cassiopeiids 153

The two largest collections of radiants come from C. Hoffmeister’s 1948 book Meteorstöme and the American Meteor Society (AMS). Hoffmeister’s book contains tables of 5,406 radiants, of which 14 are in the Cassiopeia region during July and August in the years spanning 1908–1937. The AMS has compiled over 8,000 radiants, of which at least 26 are located in Cassiopeia during July and August in the years spanning 1902–1968. However, there is a distinct difference in the distribution of the radiants between these two sources. Hoffmeister and his assistants systematically observed meteors on every possible clear night in either Germany or Namibia, while the AMS observers were observing from across North America in a less systematic fashion. This is not to say that the AMS observers were not as dedicated as Hoffmeister, as some certainly were, but the fi nal result is interesting: Hoffmeister reveals an almost even distribution of Cassiopeiid radiants in July and August, while the majority of Cassiopeiid radiants in the AMS lists are in August— around the time of the maximum of the Perseid meteor shower. There might be an indication that the Cassiopeiid activity weakened by the middle of the twentieth century. For a meteor shower that was once described as producing bright meteors and frequent fi reballs, none of the photographic surveys conducted in the United States, Canada, and Europe in the 1940–1980s detected any defi nite members. A search through 2,529 photographic meteors published by R. E. McCrosky and A. Posen (1961) revealed two possible candidates, designated 8076 and 3402. Meteor 8076 was photographed on 1953 July 16.42 (l = 114.2°). The radiant was determined as a = 12°, d = +64°, while the geocentric velocity was 48.9 km/s. Meteor 3402 was photographed on 1952 July 26.22 ( l = 123°). The radiant was determined as a = 9°, d = +57°, while the geocentric velocity was 58.0 km/s. 56 Meteor 3402 could be a late member of the Zeta Cassiopeiids, which are discussed later in this chapter. Radar studies have been more successful in detecting these streams. B. L. Kashcheyev and V. N. Lebedinets (1967) analyzed the data acquired during 1960 by the radar system at the Kharkov Polytechnical Institute (Ukraine). Among the 51 meteor streams detected were streams “23” and “31”. Stream 23 was composed of 41 meteors that were detected during July 4–28 (l = 102–125°) from an average radiant at a = 13°, d = +66°. Stream 31 was composed of 23 meteors that were detected during July 14–28 (l = 112–125°) from an average radiant at a = 0°, d = +56°.57 Z. Sekanina (1976) analyzed the data acquired during 1969 by the Radio Meteor Project and found several radiants in Cassiopeia during July, but one was particularly interesting. Named the “Cassiopeids,” they were active during July 14–19 (l = 111–116°), although a longer duration is possible since the equipment was shut down during July 5–13, July 20, and July 22–24. The “Cassiopeids” had a nodal passage on July 16.2 (l = 113.2°), during which time the radiant was at a = 1.9°, d = +64.3°. The geocentric velocity was determined as 39.3 km/s. These numbers, as well as the orbit given below, are similar to the streams recognized by Kashcheyev and Lebedinets.58 V. Znojil (1982) studied a set of 10,224 telescopic and visual meteors that had been plotted during 1957–1968 and identi fi ed 23 meteor showers. Some of these 154 8 July Meteor Showers were already well known; however, there were three radiants in Cassiopeia that were active at the same time: Beta Cassiopeiids, Alpha Cassiopeiids, and the Kappa Cassiopeiids.59 The Beta Cassiopeiids were detected both visually and telescopically and were designated stream number three. Their duration was July 20 to August 20 ( l = 117–147°). The visual branch peaked on August 7 (l = 134.45°) from a radiant at a = 5.1°, d = +60.7°, and had a radiant drift of about +1.0° in a and +0.2° in d . The telescopic branch peaked on August 2 (l = 129.90°) from a radiant at a = 0.8°, d = +61.1° and had a radiant drift of +1.2° in a and +0.3° in d. As a whole, Znojil noted a complicated activity curve, with two maxima. The secondary maximum occurs on August 10 ( l = 137.6°) and it was noted that the frequency considerably varies from year to year. Znojil added, “it was quite large in 1967.” The Alpha Cassiopeiids were only detected telescopically and were designated stream number four. Their duration was July 27–August 7 (l = 124–135°). They peaked on July 31 (l = 127.93°) from a radiant at a = 5.6°, d = +57.6° and had a radiant drift of +1.2° in a and +0.2° in d . Znojil noted that this shower’s activity level in 1968 was half that observed in 1967. He suggested this stream was associated with stream 31 above. The Kappa Cassiopeiids were only detected telescopically and were designated stream number fi ve. Their duration was July 23 to August 7 ( l = 120–135°). They peaked on August 3 ( l = 130.24°) from a radiant at a = 11.8°, d = +65.8° and had a radiant drift of +1.2° in a and +0.1° in d . Znojil said this was the strongest telescopic shower in 1967. He added, “The stream radiant scatter is considerable (about 3° or more).” Znojil suggested this stream was associated with stream 23 above. A. Dubietis (2000) analyzed visual observations that had been made by himself at Salakas, Lithuania during 1990–1996. He noted that because of the shorter nights prior to July 21, as well as a brighter limiting magnitude, his analysis begins with this date. He added that his observations made in 1989, which were not included in this study, revealed the Cassiopeiids might be active as early as the fi rst 10 days of July. Dubietis observed 497 Cassiopeiids during the period of July 21 to August 17 (out of 5,631 total meteors) and said, “The shower is rich in faint and short meteors.” Dubietis added, “Another typical feature of … activity behavior is the irregular activity even approaching maximum. Large fl uctuations in meteor hourly rates (from 2 to 10) around the maximum make the de fi nition of the true maximum quite complicated.” This is evident in a table he provided showing the solar longitude of maximum and the ZHR for each year. This data is given in Table 8.2 , although Dubietis noted, “The 1991 ZHR may be overestimated due to changing observing conditions in a short period” (Table 8.3 ). Dubietis presented some additional information about the Cassiopeiids. The average date of maximum is July 29/30 (l = 126.6°). Taking the population index (r) as 3.4, he determined that r = 3.43 for the Cassiopeiids. In addition, he determined three radiants from his observations. The fi rst was at a = 0°, d = +59°, the second at a = 10°, d = +62°, and the third at a = 22°, d = +61°. 60 The International Meteor Organization’s Video Meteor Network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during Cassiopeiids 155

Table 8.3 Maximum ZHR of Cassiopeiids Year l (°) ZHR 1990 126.6 12.6 ± 3.8 1991 126.5 11.5 ± 3.5 1991 129.3 16.1 ± 4.1 1992 126.2 9.2 ± 2.9 1994 130.4 7.7 ± 1.9 1995 125.4 8.1 ± 1.8 the period 1993–2012. Despite a search through this database for signs of Cassiopeiid streams, mostly radiants were found in the right location lasting only 2–3 days. There is one long-term radiant that moves from northwestern Andromeda into south-central Cassiopeia and seems to peak in the latter constellation. The radiant is at a = 357.4°, d = +46.5° on August 3 (l = 131°) and moves to a = 11.9°, d = +54.0° by August 14 (l = 142°). A more northerly branch is also within the million meteors database, although it is based on a weaker dataset. The duration is July 27 to August 7 ( l = 124–135°) and the average radiant position is at a = 16.7°, d = +73.0°. Perhaps the strongest recent acknowledgement of a stream from this region comes from the Canadian Meteor Orbit Radar (CMOR). P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2008) detected a stream they called the “Psi Cassiopeids” amongst data gathered during 2002–2006. This stream was said to span the period of July 12–26 (l = 110–124°), with its maximum coming on July 19 (l = 117.5°) from a radiant at a = 11.9°, d = +65.4°. The geocentric velocity was given as 44 km/s, while the radiant’s daily motion was determined as +1.22° in a and +0.43° in d .61 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as July 1–31 ( l = 100–129°), while maximum occurred on July 22 ( l = 120°) from a radiant at a = 14.8°, d = +66.6°. The geocentric velocity was determined as 44.8 km/s. The radiant’s daily motion was determined as +0.96° in a and +0.38° in d . 62 The orbits labeled “3402” and “8076” are the photographic meteor orbits from McCrosky and Posen (1961). The orbits labeled “1960–1923” and “1960–1931” are from Kashcheyev and Lebedinets (1967). The orbit labeled “1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 3402 173 124 103 1.01 1.21 −4.78 8076 145 115 88 0.93 0.88 7.59 1960–1923 126 116 77 0.87 0.49 1.7 1960–1931 107 115 83 0.90 0.18 1.09 1969 136.5 113.9 76.1 0.939 0.375 1.50 2002–2006 143.9 117.5 83.1 0.949 0.5710 2.2 2002–2008 143.06 120.0 83.4 0.9378 0.622 2.48 156 8 July Meteor Showers

Zeta Cassiopeiids

This meteor shower was announced at the end of 2012 in two separate papers published in WGN, The Journal of the International Meteor Organization ; however, the actual discovery goes back to 2005. The Polish Comets and Meteors Workshop (CMW) was held during 2005 July 1–15. In the evenings, the sky was not only monitored visually, but also by photographic and video cameras. On the fi nal night of the CMW, visual observers “reported an unusual number of bright meteors and even fi reballs.” An analysis of the visual drawings revealed a ZHR higher than four. The photographic and video data was inspected the next day, and it was found that the video cameras had detected “an unusually high number of meteors,” about half of which indicated a radiant “north of Pegasus and Andromeda.” It was soon found that three stations of the Polish Fireball Network (PFN) had also recorded the brighter meteors, including a magnitude −6 fi reball in morning twilight. In all, the video cameras revealed a ZHR of 10–15. An analysis of the PFN data revealed a radiant at a = 6°, d = +51° and a geocentric velocity of 57 km/s. During the next few years this data, as well as video data from other sources, was analyzed by P. Zoładek and M. Wisniewski (2012). A search through CMW data going back to 1996 revealed no trace of this radiant prior to 2005. A search through the International Meteor Organization Video Network database revealed only weak activity in 2005 and 2006, but clearly visible activity during 2007–2011. They also analyzed the database of SonotaCo, the Japanese video meteor network during the period of 2007–2009. They indicated that bad weather interfered with observations during crucial periods, but ultimately found one meteor orbit from 2008 and 19 meteors during 2009. Zoładek and Wisniewski ultimately concluded that activity is present from July 12 to 17. Maximum occurs around July 15 ( l = 113.1°) from an average radiant at a = 5.9°, d = +50.5°. The geocentric velocity was determined as 57.4 km/s.63 Published at the same time and in the same publication as the above paper, was an independent analysis of this meteor shower by D. Šegon, Ž. Andreic, K. Korlevic, P. S. Gural, F. Novoselnik, D. Vida, and I. Skokic (2012) based on data gathered by the Croatian Meteor Network (CMN). They initially discovered this meteor shower during an analysis of 1,211 orbits that had been determined by CMN from data gathered during 2007. Thirteen orbits belonged to this new shower. Following an announcement to the International Astronomical Union Data Center, the shower received the formal name of “Zeta Cassiopeiids.” The authors next analyzed the orbits determined by the CMN from data gathered during 2008– 2010, as well as the data gathered by the International Meteor Organization’s Video Meteor Network. They found members of this shower were present in all years from 2006 to 2012 and noted, “we have found that the relative strength for this radiant has increased.” They concluded that the radiant is active during July 9–21. Maximum occurs on July 15 ( l = 113.2°) from a radiant at a = 6.9°, d = +50.7°. The geocentric velocity is 57.3 km/s, while the radiant drift is +1.4° in a and +0.5° in d .64 July Gamma Draconids 157

The orbit labeled “2005” is the average of four meteors detected by the Polish Fireball Network that were presented by Zoładek and Wisniewski (2012). The orbit labeled “2009” is the average of 19 video meteor orbits from SonotaCo that were presented by Zoładek and Wisniewski (2012). The orbit labeled “2007–2010” is from Šegon et al. (2012).

w W (2000) i q e a 2005 165.62 112.55 108.17 1.002 0.862 7.23 2009 165.01 112.68 107.39 0.9993 0.9610 25.60 2007–2010 163.2 113.7 107.5 0.995 0.947 18.77

July Gamma Draconids

The discovery of this meteor stream is attributed to P. B. Babadzhanov (1963). In the course of a photographic meteor survey at the Institute of Astrophysics of the Academy of Sciences of Tajikistan (Tajikistan) during 1957 June to 1959 December, a total of 185 meteors were photographed from two stations, which enabled the accurate reduction of their orbits. While examining the data for groupings for well- known meteor showers, Babadzhanov noted four meteors from a group he labeled “I”: three detected during 1957 July 26/27 and one detected on 1958 August 12.65 Because of data shown below, only the three meteors from July 26/27 (l = 123.7°) are considered as truly representing the July Gamma Draconids. These indicate a radiant of a = 278.65°, d = +49.60° and a geocentric velocity of 26.4 km/s. Babadzhanov also noted this radiant was close to a radiant that V. A. Malzev reported in 1930 (called the “c Draconids” at a radiant of a = 279°, d = +55°) and photographic meteor 8089 that was reported during the Harvard Meteor Program of 1952–1954. With respect to the latter, this meteor was among 413 precise orbits determined by L. G. Jacchia and F. L. Whipple (1961). It was photographed on 1953 July 20, came from a radiant at a = 280.97°, d = +50.72°, and had a geocentric velocity of 29.53 km/s.66 A. F. Cook, B. A. Lindblad, B. G. Marsden, R. E. McCrosky, and A. Posen (1973) isolated three photographic meteors detected during the Harvard Meteor Project of 1952–1954. The duration was given as July 6–24, while the average radiant was a = 271°, d = +59°. They noted that the orbit bore a resemblance to the orbit of comet C/1919 Q2 (Metcalf).67 Despite the detection during photographic surveys, no trace of this stream was found during Northern Hemisphere radio meteor surveys conducted by B. L. Kashcheyev and V. N. Lebedinets in 1960 and Z. Sekanina during 1961–1965. It is interesting that Sekanina did detect a nearby radiant during the 1968–1969 Radio Meteor Project. He named it the “Omicron Draconids”, establishing the radiant as a = 284.7°, d = +60.9° on July 17.7 (l = 114.7°) and noting a duration of 14 days.68 158 8 July Meteor Showers

The next detection of this meteor stream came during 2007–2008, when the Japanese video meteor network SonotaCo detected 22 meteors from a radiant at a = 280.1°, d = +51.1°. The radiant was active from July 24 ( l = 121.8°) to July 31 ( l = 128.8°), with the peak occurring on July 28 (l = 125.3°). The geocentric velocity was given as 27.4 km/s.69 The most recent detection of this meteor stream came in 2011 as a result of the Cameras for All-sky Meteor Surveillance (CAMS). A total of 25 meteors were detected during the period of July 24 (l = 120.93°) to August 1 (l = 128.45°). At the time of the peak on July 28, the radiant was at a = 279.62°, d = +50.41°. The geocentric velocity was given as 27.54 km/s.70 Little evidence of visual observations of this radiant was found. W. F. Denning (Bristol, England) plotted 21 meteors from a radiant at a = 284°, d = +57° during 1876 July 16–18. He described them as very rapid and faint.71 Thereafter, only three doubly observed meteors of magnitude 1–2 appear to be related to Denning’s radiant. These were reported by English observers in 1908 and 1914. The orbit labeled “1957–1958” is from Babadzhanov (1963). The orbit labeled “1953” is from Jacchia and Whipple (1961). The orbit labeled “1952–1954” is from Cook et al. (1973). The orbit labeled “2011” is from CAMS (2012). The orbit labeled “C/1919 Q2” is that of comet Metcalf.

w W (2000) i q e a 1957–1958 203.1 124.4 38.7 0.972 0.926 13.14 1953 203.7 118.0 43.6 0.973 1.012 −81 1952–1954 190 114 43 1.01 1.0 ϱ 2011 202.31 124.66 40.24 0.978 0.972 34.93 C/1919 Q2 185.75 122.10 46.38 1.1153 1.0002 −5023

Beta Equuleids

The International Meteor Organization created a web site containing an analysis of more than one million meteors detected by the Video Meteor Network from 1993 into 2012, but there does not seem to be convincing evidence of activity from these radiant positions. Occasional points of activity do pop up within about 10° of these positions, but none show longevity beyond a day or show a reasonable radiant drift that indicates they are related to one another.73 The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 62 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 1271 meteor orbits.

w W (2000) i q e a 2002–2006 331.5 106.5 48.5 0.153 0.8252 0.9 2002–2008 331.99 107.0 48.3 0.1517 0.824 0.86

Alpha Lacertids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) announced the discovery of 13 new meteor showers after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired during 2002–2006. The Alpha Lacertids were said to span the period of July 4–12 ( l = 102–110°), with its maximum coming on July 7 ( l = 105.5°) from a radiant at a = 343.0°, d = +49.6°. The geocentric velocity was given as 38.9 km/s, while the radiant’s daily motion was determined as +0.70° in a and +0.37° in d .72 Complete details were published in the journal Icarus in 2008. 61 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as July 2–17 (l = 100–115°), while maximum occurred on July 11 (l = 109°) from a radiant at a = 348°, d = +51.6°. The geocentric velocity was determined as 38.3 km/s. The radiant’s daily motion was determined as +1.1° in a and +0.42° in d .62 The International Meteor Organization’s Video Meteor Network created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. Activity from this radiant was located on three consecutive days spanning July 9–11 (l = 107–109°). On July 9, 38 meteors emanated from a radiant at a = 345.5°, d = +46.0°. On July 10, 76 meteors emanated from a radiant at a = 346.9°, d = +55.0°. On July 11, 105 meteors emanated from a radiant at a = 341.4°, d = +44.5°. 73 The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 62 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 1271 meteor orbits. 160 8 July Meteor Showers

w W (2000) i q e a 2002–2006 240.2 105.5 81.8 0.981 0.0791 1.1 2002–2008 331.99 107.0 48.3 0.1517 0.824 0.86

Alpha Lyrids

The Alpha Lyrids were discovered in 1958 July during a meteor expedition to Mount Bezovec, Slovakia. J. Grygar, L. Kohoutek, Z. Kviz, and J. Mikusek led the team of 44 observers from observatories and astronomy clubs. The purpose of the expedition was to obtain observations of sporadic telescopic meteors, but the observers ended up discovering a new meteor shower. The observers watched the skies between July 10 and 25, but the Alpha Lyrids were only detected during July 10–20. Observations made with 25 × 100 binoculars revealed a maximum hourly rate slightly higher than 18 on July 16, while observations with 10 × 80 binoculars revealed a maximum rate near 33 on July 15. In all, 839 meteor paths were plotted during eight nights of actual observations. Two radiants were revealed, although only the right ascension could be determined precisely: one radiant had a = 278.7°, while the other was at a = 300.5°. The authors concluded that the latter right ascension corresponded with the antisolar point, but they believed the former right ascension’s declination “cannot be too high....”.74 Fortunately, V. V. Martynenko happened to have independently discovered this shower while observing at Simferopol, Ukraine, in the same year. He observed a very strong telescopic shower on July 9–10, giving the radiant as a = 277.5°, d = +39°. 74 During 1969, members of the Crimean Yaroslavl and Dnepropetrovsk amateur astronomer societies participated in a visual and telescopic study of the Alpha Lyrids. One of the shower’s original discoverers, Martynenko, coordinated the survey with the help of N. I. Bondar, N. M. Kremneva, and V. V. Frolov. Meteors from this stream were detected during July 9–19, with the greatest activity coming during July 11–16. Based on 19 radiants determined from the plots of 825 visual and telescopic meteors, the average position was a = 280.9°, d = +37.8°. The radiant diameter was generally given as 2°, and the general direction of the radiant’s daily motion was to the southeast. The meteors were described as white and fast, with an average magnitude of 4.1. During the period of observation the authors concluded that the Alpha Lyrids were “one of the most active showers in the range of bright stellar magnitudes, up to 3.5 m, inclusively, and the most active in the faint range, 3m−6m.” 75 Previous observations of this shower seem to be nonexistent. No trace of activity is present in any of the nineteenth century publications, nor does convincing evidence exist in C. Hoffmeister’s Meteorströme and the records of the American Meteor Society. Daytime Xi Orionids 161

In an attempt to establish the orbit of this stream, the lists of photographic and radar meteor orbits were searched. No possible candidates were found among the ﬁ rst group of orbits, but three radar orbits were found among the raw data sent by Z. Sekanina. These meteors had been detected during the Radio Meteor Project and all appeared during 1969 July 15–19. The average radiant was determined as a = 286.8°, d = +35.5°.76 The International Meteor Organization created a web site containing an analysis of more than one million meteors detected by the Video Meteor Network from 1993 into 2012, but there does not seem to be convincing evidence of activity from these radiant positions. Occasional points of activity do pop up within about 5–10° of these positions, but none show longevity beyond a day or show a reasonable radiant drift.73 The following orbit is an average of three radio meteor orbits found among the 39,145 orbits determined by Sekanina.

w W (2000) i q e a 231.8 114.4 34.3 0.860 0.652 2.47

Daytime Xi Orionids

The ﬁ rst detection of this daylight shower is attributed to C. S. Nilsson (1964). He analyzed the data acquired during 1961 by the radio equipment at the University of Adelaide (South Australia, Australia). One of the meteor showers was designated “61.7.5” and was detected during July 23–25. Its nodal crossing was given as July 24 ( l = 121.2°), at which time the radiant was at a = 93.7°, d = +15.0°. The geocentric velocity was determined as 44.0 km/s.77 Analyzing data collected by the Canadian Meteor Orbit Radar (CMOR) during 2002–2008, P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 1089 meteor orbits from this stream. They noted a duration of July 31 to August 13 ( l = 128–140°) and said the shower peaked on August 9 ( l = 137°) when the radiant was at a = 107.5°, d = +16.2°. The radiant’s daily motion was determined as +0.7° in a and −0.1° in d , while the geocentric velocity was 43.8 km/s.62 The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1961 211.6 301.9 32.8 0.08 0.99 8.33 2002–2008 202.67 317.0 32.2 0.0461 0.986 3.24 162 8 July Meteor Showers

Epsilon Pegasids

This meteor shower was ﬁ rst announced in 2007, when P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2007) announced the discovery of 13 new meteor showers after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired during 2002–2006. The Epsilon Pegasids were said to span the period of July 6–8 ( l = 104–106°), with its maximum coming on July 7 ( l = 105.5°) from a radiant at a = 326.3°, d = +14.7°. The geocentric velocity was given as 29.9 km/s, while the radiant’s daily motion was determined as +1.50° in a and +0.45° in d .72 Complete details were published in the journal Icarus during 2008.61 Brown, Wong, Weryk, and P. A. Wiegert (2010) published further results from CMOR, this time using results spanning 2002–2008. The duration was given as June 28 to July 7 ( l = 97–105°), while maximum occurred on July 7 (l = 105°) from a radiant at a = 324.3°, d = +13.2°. The geocentric velocity was determined as 30.3 km/s. The radiant’s daily motion was determined as +1.15° in a and −0.3° in d . 62 The International Meteor Organization created a web site containing an analysis of more than one million meteors detected by the Video Meteor Network from 1993 into 2012. Weak traces of this shower are present. For example, 46 meteors came from a radiant at a = 320.4°, d = +13.5° on July 8 (l = 106°). On both the preceding and following days the radiant sometimes shifts northward by 5° or more. For example, 42 meteors came from a radiant at a = 320.4°, d = +19.5° on July 7 ( l = 105°). These radiants never seem to appear on the same day, so it is likely they are one and the same, with the small sample not being enough to ﬁ rmly establish the location.73 The orbit labeled “2002–2006” is from Brown et al. (2008) and is based on 62 meteor orbits. The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 1271 meteor orbits.

w W (2000) i q e a 2002–2006 335.7 105.3 52.5 0.173 0.7675 0.7 2002–2008 333.27 105.0 54.2 0.1733 0.780 0.79

July Pegasids

This meteor shower was ﬁ rst theorized by D. Olsson-Steel (1987), while calculating radiant locations for several comets and minor planets. He determined two radiants for comet “1979 X,” which is now known as C/1979 Y1 (Brad ﬁ eld). One of the radiants was predicted to occur on July 10 from a radiant at a = 346°, d = +10°.78 July Phoenicids 163

M. Ueda (2012) provided details of the July Pegasids after isolating 63 simultaneously observed meteors from the database kept by the SonotaCo Video Network of Japan. He noted that one meteor was detected in 2008, 11 in 2009, 17 in 2010, and 34 in 2011—the variations being attributed to bad weather. The duration was determined as July 6–19 (l = 104.6–117.0°), while the maximum came on July 13 (l = 110.9°) from a radiant at a = 349.6°, d = +11.3°. The geocentric velocity was determined as 63.9 km/s.79 The International Meteor Organization (IMO) created a web site containing an analysis of more than one million meteors detected by the Video Meteor Network from 1993 into 2012. Stream 108 is the July Pegasids. The duration spans July 3 to August 5 (l = 101–132°), during which time the radiant moves from a = 343.2°, d = +6.5° to a = 9.1°, d = +21.0°. Maximum comes on July 10 (l = 108°) from a radiant at a = 347.9°, d = +11.0°. The following orbits were calculated by the Author using the date of maximum and the radiant at maximum that were determined by the Video Meteor Network of the IMO. The orbit labeled “IMO-1” was calculated using the geocentric velocity that was determined by CMOR. The orbit labeled “IMO-2” was calculated assuming a semimajor axis of 2.5 AU. The orbit labeled “IMO-3” is a parabolic orbit. The orbit labeled “IMO-4” was calculated using the Vinf = 68.0 km/s that was determined by the IMO. The orbit labeled “2002–2008” is from Brown et al. (2010). The orbit labeled “C/1979 Y1” is that of comet Brad ﬁ eld.

w W (2000) i q e a IMO-1 355.1 108 117.0 0.016 0.972 0.58 IMO-2 279.3 108 154.8 0.490 0.804 2.5 IMO-3 261.1 108 155.9 0.587 1.0 ϱ IMO-4 260.9 108 155.9 0.588 1.003 −225 C/1979 Y1 257.60 103.22 148.60 0.5453 0.9879 45.12

July Phoenicids

The ﬁ rst observation of this shower is attributed to A. A. Weiss (1960). While analyzing the data acquired during 1956 December to 1958 August by the radio-echo apparatus at the University of Adelaide (South Australia, Australia), Weiss discovered “a previously unreported shower.” During 1957 July 12–17, Weiss noted an average radiant at a = 31°, d = −44°. He said the shower exhibited “a marked asymmetry in activity across the stream, with a fairly sharp maximum at l = 112° [July 14] . The activity is patchy and the radiant tends to be diffuse.” At the peak of activity, the hourly rate was slightly over 20. Weiss said the radiant reappeared during 1958 and was detected from July 8 (l = 106°), from a radiant at a = 28°, d = −50°, to July 16 (l = 114°), from a radiant at a = 36°, d = −46°. The peak of activity came on July 15, when the radiant was at a = 32°, d = −48°, at which time the hourly rate was 30.80 164 8 July Meteor Showers

Weiss proceeded to reexamine the radio–echo observations begun at Adelaide in 1953. Evidence that this stream existed was found on July 9, 10, 13, and 16, and the average radiant was determined as a = 30°, d = −43°. Weiss was also confi dent that observations had been made in 1954 and 1956 since increased activity had been noted around July 13, “which could be due to a radiant which transits near 08hr. This is suffi ciently close to the transit time of from 06.49 to 07.12 found from the radiant equipment to identify this activity also with the Phoenicid radiant.”81 This meteor shower was not detected when C. S. Nilsson analyzed the radio- echo data acquired at the University of Adelaide during 1961. The radio-echo survey conducted by G. Gartrell and W. G. Elford at the University of Adelaide during 1969 did not operate during July. Naked-eye observations have revealed weak activity levels, at best. During the period of 1969–1980, M. Buhagiar (Perth, Western Australia, Australia) observed 20,974 meteors. In 1981, he compiled them into a list of 488 visual radiants. During the 12 year period of study, Buhagiar observed this shower on only two occasions. He gave the duration as July 11–15, while a maximum hourly rate of one came on July 14 from a radiant of a = 34°, d = −50°. 82 According to J. Wood, observations by the Western Australia Meteor Section have produced somewhat inconclusive results as to the activity of this stream. Members failed to detect any activity from the region in 1977, and the 1979–1980 observations failed to cover the shower’s period of activity with observing gaps of July 2–19 in 1979, and July 7–18 in 1980.36 The conclusion that might be reached concerning this meteor shower is that, although strong activity seems to be present in the radio–echo (and probably telescopic and video) range, visual activity is very low. The stream might also produce periodic activity. Insuf fi cient data has been gathered to allow the determination of the velocity and, hence, the orbit of this stream. The following parabolic and elliptical orbits were calculated based on the existing information, the latter of which is based on an assumed semimajor axis of 2.0 (a good average for meteor streams).

w W 2000) i q e a 25.5 292.7 86.1 0.967 1.0 ϱ 37.0 292.7 79.0 0.946 0.527 2.0

Note a strong similarity between this parabolic orbit and the slightly hyperbolic orbit of comet C/1912 R1 (Gale). There is also a close similarity with comet C/1932 P1 (Peltier–Whipple), which has an orbital period of 291 years, although the biggest problem here is the ascending node. Jack D. Drummond (New Mexico State University) predicted that a shower from this latter comet would reach maximum on September 8 from a = 57°, d = −39°.83 Piscis Austrinids 165

w W (2000) i q e a C/1912 R1 25.62 298.25 79.81 0.7161 1.0005 −1432 C/1932 P1 38.47 345.46 71.72 1.0372 0.9764 43.89

Phi Piscids

This meteor shower was ﬁ rst announced by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2009) after analyzing data from the Canadian Meteor Orbit Radar (CMOR) acquired during 2002–2008. The Phi Piscids were said to reach maximum on July 7 ( l = 106.0°) from a radiant at a = 20.1°, d = +24.1°. The geocentric velocity was given as 62.9 km/s, while the radiant’s daily motion was determined as +1.56° in a and +0.36° in d .84 Complete details were published in the journal Icarus In 2010, including the duration, which was given as July 6–9 ( l = 104–107°). 62 The International Meteor Organization created a web site containing an analysis of more than one million meteors detected by the Video Meteor Network from 1993 into 2012. Stream 100 is the Phi Piscids, but the duration is far longer than indicated by CMOR, as a total of 4,258 meteors indicate a duration of June 15 to July 31 ( l = 84–128°). During this period, the radiant moves from a = 7.3°, d = +15.5° to a = 37.0°, d = +25.0°. The shower peaks on July 2 ( l = 100°) from a radiant at a = 13.8°, d = +25.0°. For a number of days in late June and early July, this shower can be the most active in the sky.85 The orbit labeled “2002–2008” is from Brown et al. (2010) and is based on 1395 meteor orbits.

w W (2000) i q e a 2002–2008 125.02 106.0 152.6 0.8559 0.590 2.09

Piscis Austrinids

Duration: July 16 to August 13 (l = 114–140°) Maximum: July 28 (l = 125°) Radiant: a = 339°, d = −29° ZHR: 5

Radiant Drift: a = UNK, d = UNK V G : UNK km/s

The discovery of this meteor shower should probably be credited to R. A. McIntosh (1935). He provided a list of 320 radiants that were based on the observations made by New Zealand observers during the 1920s and 1930s. He found seven separate areas of activity from the relatively small constellation of Pisces Austrinus 166 8 July Meteor Showers during mid–July to mid–August. The most prominent shower was called the “Alpha Pisces Australids,” the existence of which was based on 24 visual radiants. The duration was given as July 26–August 8, during which time the radiant moved from a = 337°, d = −33° to a = 350°, d = −30°.86 The other six radiants isolated by McIntosh could very well be related to this main radiant and are as follows: • “Pisces Australids:” Based on three visual radiants, the duration was given as July 28 to August 3, while the average radiant was at a = 326°, d = −26°. • “Theta Pisces Australids:” Based on two visual radiants, the duration was given as August 12–14, while the average radiant was at a = 327°, d = −32°. • “Beta Pisces Australids:” Based on 11 visual radiants, the duration was given as July 14–22, while the average radiant moved from a = 330.5°, d = −30° to a = 339°, d = −30°. • “Lambda Pisces Australids:” Based on fi ve visual radiants, the duration was given as August 5–14, while the average radiant moved from a = 334°, d = −27.5° to a = 339°, d = −26°. • “Epsilon Pisces Australids:” Based on three visual radiants, the duration was given as August 13–14, while the average radiant was at a = 338°, d = −24°. • “20 Pisces Australids:” Based on two visual radiants, the duration was given as August 8–9, while the average radiant was at a = 340.5°, d = −27°. C. Hoffmeister (1948) noted this meteor shower in his 1948 book Meteorströme . Hoffmeister separated the 5406 German–observed visual radiants into two separate groups and managed to detect the Pisces Austrinids in each collection. The fi rst group contained ten radiants observed during the period of 1910–1930. The average radiant was given as a = 336°, d = −28°, while the date of maximum was given as July 29 (l = 125°). The second group primarily contained radiants observed during 1937, when Hoffmeister was observing in South Africa. The average radiant was given as a = 338°, d = −29°, while the date of maximum was given as August 2 ( l = 129°). After combining all of the shower’s radiants, Hoffmeister concluded that the stream produced notable activity during July 29 to August 2 from an average radiant of a = 337°, d = −28°. The date of maximum was given as July 31 ( l = 127°). Hoffmeister added that the simultaneous rise and fall of activity from this stream and the Delta Aquariids, as well as the large apparent radiant of the latter shower, brought to light the possibility of an association.87 McIntosh and Hoffmeister were not the fi rst to observe this meteor shower. W. F. Denning (1899) included several observations from the nineteenth century. A. S. Herschel observed a radiant at a = 338°, d = −28° on 1865 July 28. E. F. Sawyer (Cambridge, Massachusetts, USA) plotted four very slow and bright meteors from a radiant of a = 337°, d = −33° on 1878 July 28. L. Cruls (Rio de Janeiro Observatory, Brazil) noted several meteors during 1881 July 25–30 from a = 343°, d = −25°. Denning plotted four slow and white meteors from a = 338°, d = −25° during 1898 July 28–31.8 Although Denning had put these observations under the label of “Alpha Piscis Australids,” he included observations spanning the period of July 2 through September, so he did not recognize the true nature of the stream. Denning Piscis Austrinids 167 was a believer in stationary radiants that could be active for months at a time, which unfortunately takes something away from the value of his research. There is a period of complete neglect of this meteor shower following the 1937 observations of Hoffmeister’s group, but observations fi nally resumed in 1953. C. D. Ellyett and K. W. Roth (1955) analyzed data acquired by radar equipment at Christchurch, New Zealand, and noted a “highly probable” Pisces Austrinid radiant at a = 328°, d = −27° during July 21–26. The shower was considered quite strong.88 B. L. Kashcheyev and V. N. Lebedinets (1967) analyzed the data acquired by a radar survey conducted during 1960 at the Kharkov Polytechnical Institute (Ukraine). They detected 32 meteors from this stream during July 16 to August 13 and concluded that maximum came on July 26 (l = 123°), at which time the radiant was at a = 340°, d = −26°. From this data, the fi rst orbit was calculated, which indicated a 45° inclination and a semimajor axis of 4.31 AU.23 The long absence of visual observations fi nally ended in 1965, when E. F. Turco (Cranston, Rhode Island, USA), a member of the American Meteor Society, observed the Alpha Pisces Australids during three nights, centered on July 29/30. “The meteors I saw were not too bright, though I was surprised with two exceptions, both fi reballs.” He pointed out that this was the fi rst time he had ever detected this shower.89 The fact that Turco only noted the shower in 1965, despite being a regular observer, as well as member and regional director of the American Meteor Society for many years, brings forth an excellent explanation as to the reason for the shower’s neglect during 1938–1952. Meteors from this shower are only visible from the United States and Europe under special circumstances that not only involve weather, but also require an unusual number of meteors heading toward the north. Observers in the Southern Hemisphere should fi nd the shower as an annual fi xture in their late July skies. It will be remembered that Hoffmeister noted excellent activity from this radiant during his observations in South Africa in 1937, and McIntosh noted numerous radiants in the area based upon observations made by him and fellow New Zealand observers during the 1920s and 1930s. The fi rst notable Southern Hemisphere visual survey of meteor activity following that of McIntosh was conducted by M. Buhagiar (Perth, Western Australia, Australia) during 1969–1980. Recording a total of 20,974 meteors, Buhagiar compiled a list of 488 probable visual radiants. Radiant 472 was called the “Alpha Pisces Australids” and was based on ten visual radiants. The duration was given as July 27 to August 10, while a maximum hourly rate of four was said to be emanating from a = 344°, d = −30° on July 31. 82 None of the nearby Pisces Austrinus radiants noted by McIntosh were prominent enough to make Buhagiar’s list. Nearly simultaneous with Buhagiar’s survey, the Royal Astronomical Society’s New Zealand Meteor Section was also conducting a decade–long survey for a list of Southern Hemisphere meteor showers. Covering the 1970s, the observations allowed section director J. E. Morgan to compile a list of 213 probable visual radiants. The “Alpha Pisces Australid” shower was detected. The duration was given as July 23 to August 2, during which time the radiant moved from a = 344°, d = −31° to a = 347°, d = −34°. The maximum hourly was given as four. The New Zealand 168 8 July Meteor Showers observers also detected McIntosh’s “Beta Pisces Australid” shower. Given a short duration of July 19–21, the average radiant was at a = 337°, d = −34°, while the maximum hourly rate was three. Another radiant was also found which seems closely related to the McIntosh’s August portion of the “Alpha Pisces Australids.” Called the “Xi Gruids”, their duration was given as July 24 to August 8, during which time the radiant moved from a = 343°, d = −32° to a = 350°, d = −32°.36 The Western Australia Meteor Section (WAMS), under the directorship of J. Wood, managed to acquire observations of this meteor shower from 1977 to 1980. The “Alpha Pisces Australids” were observed during 1977 July 23–29. The maximum ZHR of about four was observed on July 28, at which time the radiant was located at a = 343°, d = −30°. During 1979 meteors were observed from this shower during July 27 to August 5. A maximum ZHR of about four came on July 28 from an average radiant of a = 343°, d = −28°. A full moon occurred on 1980 July 27, thus interfering with complete observations of this shower maximum; however, observers still gave the shower’s duration as July 19 to August 4, and detected a maximum ZHR of about two on August 3. The average radiant was then given as a = 336°, d = −32°. 36 During 2006–2007, the Davis Station radar facility in Antarctica detected the “Alpha Pisces Australids” during the period of July 24–29. J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy (2009) determined that the radiant was at a = 335.9°, d = −22.9° at the time of maximum (l = 120.9°). 90, 91 The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “1952” is from a paper by R. E. McCrosky and A. Posen (1961).92 The orbit labeled “1961–1969” is an average of fi ve meteor orbits found among 39,135 orbits acquired by Z. Sekanina during the Radio Meteor Project. The orbit labeled “2006– 2007” is from Younger et al. (2009).

w W (2000) i q e a 1960 114 304 45 0.17 0.96 4.31 1952 131 306 42 0.19 0.98 7.50 1961–1969 137.8 305.8 39.9 0.186 0.893 1.74 2006–2007 138.0 307.1 32.3 0.180 0.936 2.82

1. S. Molau and J. Rendtel, WGN, Journal of the International Meteor Organization , 37 (2009), pp. 111, 115. 2 . http://www.imonet.org/showers/shw098.html 3. R. E. McCrosky and A. Posen, Smithsonian Contributions to Astrophysics , 4 (1961), p. 59. 4. E. Heis and J. F. J. Schmidt, On Meteors in the Southern Hemisphere. Mannheim: J. Schneider (1867), p. 15. 5. J. F. J. Schmidt, Astronomische Nachrichten , 74 (1869 May 14), pp. 53−4. 6. G. L. Tupman, Monthly Notices of the Royal Astronomical Society , 33 (1873 Mar.), p. 301. 7. T. H. Waller and A. S. Herschel, Report of the Annual Meeting of the British Association for the Advancement of Science , 44 (1875), p. 288. 8. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 284. Piscis Austrinids 169

9. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 285. 10. W. F. Denning, The Observatory , 45 (1922 Sep.), pp. 301–2. 11. W. F. Denning, The Observatory , 45 (1922 Oct.), p. 332. 12. W. F. Denning, The Observatory , 45 (1922 Oct.), p. 333. 13. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 94 (1934 Apr.), pp. 584, 587. 14. C. Hoffmeister, Meteorströme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 139. 15. C. Hoffmeister, Meteorströme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 81. 16. D. W. R. McKinley, Astrophysical Journal , 119 (1954), p. 519. 17. G. S. Hawkins and M. Almond, Monthly Notices of the Royal Astronomical Society, 112 (1952), pp. 222, 224. 18. M. Almond, Jodrell Bank Annals , 1 (1952 Dec.), pp. 24, 26–7. 19. F. W. Wright, L. G. Jacchia, and F. L. Whipple, The Astronomical Journal , 62 (1952 Sep.), p. 231. 20. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 16–17. 21. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 4. 22. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 16. 23. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics, 11 (1967), pp. 188–9. 24. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 227, 234. 25. Z. Sekanina, Icarus , 13 (1970), pp. 476–7, 483, 486. 26. Z. Sekanina, Icarus , 27 (1976), pp. 281, 283, 296–7. 27. A. K. Terentjeva, Smithsonian Contributions to Astrophysics , 7 (1963), pp. 293–5. 28. S. E. Hamid and F. L. Whipple, Astronomical Journal , 68 (1963 Oct.), p. 537. 29. C. P. Olivier, Meteors. Baltimore: Williams & Wilkins Company (1925), p. 44. 30. Z. Sekanina, Icarus , 27 (1976), p. 486. 31. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society, 94 (1934 Apr.), pp. 585. 32. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 94 (1934 Apr.), pp. 583–7. 33. Meteor News , No. 13 (1972 Oct.), p. 9. 34. Meteor News , No. 18 (1973 Oct.), p. 2. 35. Meteor News , No. 23 (1974 Oct.), pp. 5–6. 36. J. Wood, Personal Communication (1986 Oct. 15). 37. N. W. McLeod, III, Meteor News , No. 65 (1984 Apr.), p. 7. 38. A. Dubietis and R. Arlt, WGN, The Journal of the International Meteor Organization, 32 (2004 Jul.), pp. 70–2, 75. 39. R. A. McIntosh, The Observatory , 53 (1930 Aug.), p. 235. 40. R. P. Greg, Monthly Notices of the Royal Astronomical Society , 32 (1872), p. 351. 41. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 37 (1877 Jan.), p. 108. 42. R. P. Greg, Report of the Annual Meeting of the British Association for the Advancement of Science , 46 (1877), p. 159. 43. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 308. 44. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 318. 45. E. F. Sawyer, American Journal of Science and Arts , 3rd series, 17 (1879), p. 69. 46. N. de Konkoly, Monthly Notices of the Royal Astronomical Society , 40 (1880 Apr.), pp. 360, 363. 47. E. F. Sawyer, Monthly Notices of the Royal Astronomical Society , 41 (1881 Mar.), p. 301. 48. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 44 (1884 Apr.), p. 298. 49. H. Corder, Memoirs of the British Astronomical Association , 5 (1897), p. 9. 50. H. Corder and J. A. Hardcastle, Memoirs of the British Astronomical Association , 6 (1898), p. 45. 51. H. Corder, Memoirs of the British Astronomical Association , 7 (1899), p. 9. 52. W. E. Besley, Memoirs of the British Astronomical Association , 8 (1900), p. 10. 170 8 July Meteor Showers

53. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), pp. 226–30. 54. D. Eginitis, Astronomische Nachrichten , 165 (1904), p. 71. 55. N. N. Sytinskaja, Trudy Tashkentskoj Astronomicheskoj Observatorii , 3 (1930), p. 108. 56. R. E. McCrosky and A. Posen, Smithsonian Contributions to Astrophysics, 4 (1961), pp. 59, 60. 57. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics, 11 (1967), p. 188. 58. Z. Sekanina, Icarus , 27 (1976), pp. 280, 295. 59. V. Znojil, Bulletin of the Astronomical Institutes of Czechoslovakia , 33 (1982), pp. 201–10. 60. A. Dubietis, WGN, The Journal of the International Meteor Organization, 28 (2000), pp. 108–13. 61. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 330. 62. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 63. P. Zoladek and M. Wisniewski, WGN, The Journal of the International Meteor Organization , 40 (2012 Dec.), pp. 189–94. 64. D. Šegon, Ž. Andreic, K. Korlevic, P. S. Gural, F. Novoselnik, D. Vida, and I. Skokic, WGN, The Journal of the International Meteor Organization , 40 (2012 Dec.), pp. 195–200. 65. P. B. Babadzhanov, Smithsonian Contributions to Astrophysics , 7 (1963), pp. 288–9. 66. L. G. Jacchia and F. L. Whipple, Smithsonian Contributions to Astrophysics, 4 (1961), pp. 106–7. 67. A. F. Cook, B.-A. Lindblad, B. G. Marsden, R. E. McCrosky, and A. Posen, Smithsonian Contributions to Astrophysics , 15 (1973), p. 3. 68. Z. Sekanina, Icaru s , 27 (1976), pp. 281, 296. 69. SonotaCo, WGN, Journal of the International Meteor Organization , 37 (2009), p. 59. 70. D. Holman and P. Jenniskens, WGN, Journal of the International Meteor Organization, 40 (2012 Feb.), pp. 36–40. 71. D1899, p. 273. 72. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Central Bureau Electronic Telegram, No. 1142 (2007 Nov. 17). 73. http://www.imonet.org/radiants/ 74. J. Grygar, L. Kohoutek, Z. Kviz, and J. Mikusek, Bulletin of the Astronomical Institutes of Czechoslovakia , 11 (1960), p. 85. 75. N. I. Bondar, N. M. Kremneva, V. V. Martynenko, and V. V. Frolov, Solar System Research , 6 (1973 Jan.), pp. 112–13. 76. Z. Sekanina, Personal Communication (1985 Mar. 19). 77. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 227, 229. 78. D. Olsson-Steel, Australian Journal of Astronomy , 2 (1987), p. 32. 79. M. Ueda, WGN, Journal of the International Meteor Organization, 40 (2012 Apr.), pp. 59–64. 80. A. A. Weiss, Monthly Notices of the Royal Astronomical Society , 120 (1960), pp. 395, 397–8. 81. A. A. Weiss, Monthly Notices of the Royal Astronomical Society , 120 (1960), pp. 397–8. 82. M. Buhagiar, Western Australia Meteor Section Bulletin , No. 160 (1981). 83. J. D. Drummond, Icarus , 47 (1981), p. 507. 84. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Central Bureau Electronic Telegram, No. 1938 (2009 Sep. 3). 85. http://www.imonet.org/showers/shw100.html 86. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), p. 717. 87. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 80–5. 88. C. D. Ellyett and K. W. Roth, AJP , 8 (1955), pp. 395–6. 89. E. F. Turco, Review of Popular Astronomy , 62 (1968 Oct.), p. 7. 90. J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy, Monthly Notices of the Royal Astronomical Society , 398 (2009), pp. 353–4 91. J. P. Younger, Personal Communication (2013 Jan. 18). 92. R. E. McCrosky and A. Posen, Smithsonian Contributions to Astrophysics , 4 (1961), p. 60. Chapter 9

August Meteor Showers

Iota Aquariids: Antihelion

Northern Branch Duration: August 11 to September 10 Peak: August 25 (l = 152°) @ a = 350°, d = 0°

Radiant Drift: a = +1.03°, d = +0.13° V G : 29 km/s Southern Branch Duration: July 1 to September 18 Peak: August 6 (l = 133°) @ a = 337°, d = −12°

Radiant Drift: a = +1.07°, d = +0.18° V G : 29 km/s

This may represent one of the most confused of the well-known annual meteor streams due to a pair of very diffuse radiants. To make matters worse, visual observations are complicated by the addition of the two Delta Aquariid streams and several streams coming out of Capricornus during July and August…not to mention the fact that the Iota Aquariids sit in the Antihelion region of the sky. The ﬁ rst apparent observation of this meteor shower was by E. Heis, who observed meteors at Flagstaff Observatory, Melbourne, Australia from 1858 March 1 to 1863 October 28. During the month of August, he saw 23 meteors from the Southern Iota Aquariids and gave the radiant as a = 337°, d = −10°. 1 Meteors were detected from a large region surrounding this radiant during the 1870s. Some of these radiants were not a part of the Iota or Delta Aquariid streams, and it is likely that they were just general noise from the antihelion region; however, there were additional observations of the Southern Iota Aquariids. W. F. Denning (Bristol, England) plotted ten meteors from a radiant at a = 339°, d = −10° during

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 171 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_9, © Springer Science+Business Media New York 2014 172 9 August Meteor Showers

1877 August 3–16.2 Denning plotted 16 meteors from a radiant at a = 339°, d = −10° during 1879 August 21–25. He said the meteors were slow and bright.3 Denning made additional observations of the Southern Iota Aquariids during the late 1880s. On 1888 August 2 and 5, he plotted three meteors from a radiant at a = 336°, d = −11°. He again described them as slow and bright. From 1889 July 27-August 3, he plotted six meteors from a radiant at a = 336°, d = −13° and described them as slow and long.4 Denning also provided the fi rst apparent observations of the Northern Iota Aquariids. From 1879 August 21 to 23, he plotted ten slow meteors from a radiant at a = 350°, d = ±0°. From 1885 August 17–20, he plotted seven swift meteors from a radiant at a = 345°, d = ±0°. On 1886 August 24 and 29, he plotted fi ve swift meteors from a radiant at a = 346°, d = +1°. 5 Observations of both streams continued to be made during the 1890s and into the twentieth century, though the radiants tended to be grouped with meteors of other streams. The fi rst person to actually recognize the Iota Aquariid stream was A. King (England), who plotted fi ve meteors from a = 331°, d = −12° from 1911 July 27 to 30. The meteors were described as exhibiting “Longish paths” with no trains. 6 King’s identifi cation referred to the Southern Iota Aquariids, but he gave no indication of a possible northern branch. R. A. McIntosh (Auckland, New Zealand) published details on both branches of this stream from the observations made by New Zealand observers in the 1920s and 1930s. In his classic paper, “An Index to Southern Meteor Showers,” two showers, called the “Iota Aquariids,” were listed, which referred to the southern branch. Shower number “272” was based on seven visual radiants and indicated a radiant movement from a = 330°, d = −14° to a = 339°, d = −10° from July 31 to August 11. Shower “280” was based on 13 visual radiants and indicated the radiant moved from a = 332°, d = −15° to a = 338°, d = −12° from July 25 to August 5. For the Northern Iota Aquariid stream there were also two possibly associated showers. Shower number “301” was based on four visual radiants. It was called the “5 Piscids” and from August 13 to 21 its radiant averaged a = 346°, d = 0°. Shower “315” was called the “14 Piscids” and was also based on four visual radiants. From August 13 to 25, it exhibited an average radiant of a = 352°, d = −3°. 7 Radiants from both branches of this stream are included in C. Hoffmeister’s 1948 book, Meteorstöme. The southern branch was seen on fi ve occasions from 1932 to 1937. These observations indicated a duration of August 3–10, with the average radiant being a = 338.2°, d = −12.2°. Three radiants of the Northern Iota Aquariids were detected from 1930 to 1937. The indicated duration was August 26–30, while the average radiant was a = 354.0°, d = −2.7°.8 The fi rst of fi cial recognition that the Iota Aquariid stream was composed of two branches should be credited to F. W. Wright, L. G. Jacchia, and F. L. Whipple (1957), as a result of Harvard College Observatory’s photographic meteor surveys. While examining “all i -Aquarid meteors found on Harvard plates during the interval June 28 to September 1, for all years of observation up through 1955,” they noted a meteor found on 1952 August 18, which “seemed to indicate a possible northern stream....” They identifi ed two additional photographic meteors from Iota Aquariids: Antihelion 173

1952: one on August 21 and the other on September 1. Using only the two earliest meteor orbits, the authors used a least-squares solution to determine the radiant’s daily motion as +1.04° in a and −0.08° in d [ the use of only two meteors makes these values highly uncertain ]. For the Southern Iota Aquariids, they used fi ve double-station and fi ve single-station meteors to determine the radiant’s daily movement as +1.04° in a and +0.02° in d . Unfortunately, despite the photographic meteors indicating only late August activity for the Northern Iota Aquariids, the authors operated under the assumption that this stream possessed a date of maximum similar to that of the southern branch. Subsequently they identifi ed a visual radiant listed by McIntosh (not discussed earlier) as representing this stream. The radiant was designated shower number “275” and was based on 11 visual radiants. During its duration of July 28 to August 2, the radiant was said to have moved from a = 331°, d = −8° to a = 334°, d = −8°. From these photographic and visual details, the authors concluded that the mid-point of the shower’s activity occurred at a solar longitude of 132.5° [ August 4], with the radiant at a = 330.87°, d = −4.95°.9 Based on the data already given, the maximum of the Northern Iota Aquariids defi nitely seems to occur in late August. Subsequently, the adoption of August 4 as the maximum of the Northern Iota Aquariids caused confusion for several years to come. This confusion fi rst showed up during the analysis of the radar survey conducted at the University of Adelaide (South Australia, Australia) from 1960 to 1961. C. S. Nilsson (1964) examined the orbital data of 2200 radio meteors, which led to the determination of 71 meteor stream orbits. Using the work of Wright, Jacchia, and Whipple as a guide, two possible Iota Aquariid streams were noted, which came to maximum at the end of July. Designated as streams “61.7.3” and “61.7.11”, they were said to respectively represent the southern and northern branches. Nilsson noted that differences did exist between his work and the 1957 study, and he considered both of his identi fi cations as uncertain.10 From what is now known of the Iota Aquariid streams, it seems believable that stream “61.7.3” was more likely associated with the Southern Delta Aquariids. Stream “61.7.11” (observed during July 25 to August 3 from a = 326.2°, d = −12.3°) actually represented the southern branch of the Iota Aquariids, instead of the northern branch, while a stream designated “61.8.2” (detected during August 16–24, from a = 343.5°, d = +0.8°) was actually the Northern Iota Aquariid stream. The confusion continued for visual observers. Amateur groups worldwide subsequently adopted the August 4 date of maximum for the Northern Iota Aquariids and many had not corrected this error until the late 1970s and early 1980s. As a result, there is a complete lack of visual observations of the northern branch during the 1960s, and only a handful during the 1970s. The fi rst accurate delineation of these two streams came about during the two sessions of the Radio Meteor Project, which operated in Havana, Illinois (USA) in the 1960s. Z. Sekanina (1973) analyzed the data from the 1961 to 1965 session. He found the Southern Iota Aquariids to be active from July 14 to August 27. The nodal passage was identi fi ed as occurring on August 9.2 ( l = 136.2°), at which time the radiant was at a = 335.3°, d = −9.1°. The geocentric velocity was determined as 28.8 km/s. The Northern Iota Aquariids were described as having a duration 174 9 August Meteor Showers extending over the period of August 13–28. The nodal passage came on August 25.1 (l = 151.5°), when the radiant was at a = 351.9°, d = −1.1°. The geocentric velocity was determined as 28.2 km/s. 11 Sekanina (1976) found both streams again during the 1968–1969 session. The Southern Iota Aquariids were found to have a duration of July 1 to September 18. The nodal passage came on August 10.4 ( l = 137.3°), when the radiant was at a = 343.0°, d = −3.2°. The Northern Iota Aquariid activity extended over the period of August 11 to September 10. The nodal passage came on August 26.0 (l = 152.4°), at which time the radiant was at a = 349.5°, d = +0.3°. 12 Some of the fi rst signifi cant visual details of these two showers were obtained in 1977 by observers in Florida. N. W. McLeod III was able to determine the fi rst average magnitude estimates of each stream. The Southern Iota Aquariids generally produced the brighter meteors, with a value of 3.05 being determined from 43 magnitude estimates. The Northern Iota Aquariids were found to have an average magnitude of 3.32, as determined from 34 magnitude estimates. Bill Gates commented that the northern stream reached a peak activity rate of 12 meteors per hour on August 20.13 Southern Hemisphere meteor observers have provided some interesting results on the Iota Aquariid streams. In 1981, M. Buhagiar (Perth, Western Australia, Australia) published details of his 20,974 meteor observations made from 1969 to 1980. Among the 488 visual radiants determined, there was no convincing evidence supporting the existence of the Southern Iota Aquariids. A possible radiant representing the Northern Iota Aquariids was seen from August 21 to 24. From a total of three observations, it was concluded that a maximum hourly rate of fi ve came from a = 354°, d = 0° on August 22.14 Members of the Western Australia Meteor Section (WAMS) have also obtained inconsistent observations of these streams. No convincing observations have been made of the Northern Iota Aquariids, but several interesting details have come forth on the Southern Iota Aquariids. In 1978, 41 meteors of this stream revealed an average magnitude of 3.36, while 15.7 % left persistent trains.15 In 1980, the WAMS detected activity from this shower from August 2 to 10. A maximum ZHR of about 2 came on August 2, from a radiant of a = 335°, d = −16°.16 Combining all of the WAMS observations, director Jeff Wood concludes that the duration of the Southern Iota Aquariids extends from July 16 to August 19. A maximum ZHR of 7–8 occurs on August 6 from a radiant of a = 335°, d = −15°. 17 An ambitious project to visually determine the radiant structure of the summer meteor showers in Aquarius and Capricornus was conducted by the International Meteor Organization from 1989 to 1991. Called the “Aquarid Project,” it involved observers in Belgium, Bulgaria, Germany, Spain, and the United States. R. Arlt, R. Koschack, and J. Rendtel (1992) noted that the Southern Iota Aquariid radiant “becomes noticeable 1 day after their activity maximum on the display of August 5, 1989…. A possible second appearance on August 7 is actually too weak to be signi fi cant.” Concerning the Northern Iota Aquariids, they wrote that the radiant “stands out very prominently and isolated during the period August 19–22, 1990.” They added, “During the period August 23–24, 1990, the radiant…is still clearly Iota Aquariids: Antihelion 175 visible with only slightly reduced prominence.” The radiant positions of the northern branch were determined as a = 323°, d = −5° on August 21 and a = 327°, d = −3° on August 24, which the authors noted was “about 5° west of the literature values.”18 L. R. Bellot Rubio (1992) examined over 26,000 meteors and fi reballs to determine the percentage of shower meteors that leave trains. He found that 6 % of the Southern Iota Aquariids leave trains.19 A. Dubietis and Arlt (2004) conducted the most recent analysis of the observational characteristics of these two streams. They used observations spanning 1997–2002. The durations of the streams were determined as July 18 to August 21 ( l = 115–148°) for the southern branch and August 9 to September 2 ( l = 136–160°) for the northern branch. The maximum of the southern branch was found to occur on August 4 (l = 132.1°) when the ZHR attained 1.6 ± 0.1. The maximum of the northern branch exhibited a broad plateau from August 15 to 31 (l = 143–158°) when the ZHR attained 1.2–2.0. The population index of the southern branch was determined as 2.67 ± 0.08, while that of the northern branch was 2.62 ± 0.07.20 The results of the Canadian Meteor Orbit Radar for the period of 2002–2008 were published by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). For the Southern Iota Aquariids, it revealed the duration as August 5–17 (l = 133– 144°), while maximum occurred on August 13 (l = 140°) from a radiant of a = 340.2°, d = −11.4°. The daily motion of the radiant drift was determined as +0.87° in a and +0.41° in d , while the geocentric velocity was 29.1 km/s. For the Northern Iota Aquariids, it revealed the duration as August 18 to September 6 ( l = 145–164°), while maximum occurred on September 1 (l = 159°) from a radiant of a = 355.4°, d = +3.4°. The daily motion of the radiant drift was determined as +0.84° in a and +0.39° in d , while the geocentric velocity was 28.7 km/s.21 Three reliable orbits have been calculated for the Southern Iota Aquariids. The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The radar equipment noted in Nilsson (1964) was not in operation from August 5 to 15; therefore, since only the fi rst half of the shower was monitored, it is not unlikely that W would actually be larger than given here.

w W (2000) i q e a 1961 312.5 126.0 6.9 0.23 0.85 1.56 1961–1965 307.7 136.7 1.4 0.277 0.836 1.69 1968–1969 319.2 137.9 4.4 0.249 0.762 1.05

The previous orbits were all determined using radio-echo techniques, but it should be noted that several Southern Iota Aquarid orbits have been computed from photographic meteors. These indicate that the values of w and W are each reversed by about 180°. The orbit labeled “MP1961” was based on ten meteors. 22 The orbit 176 9 August Meteor Showers labeled “JW1961” was based on six meteors.23 The orbit labeled “SH1963” was based on four meteors.24

w W (2000) i q e a MP1961 129.5 311.1 4.2 0.22 0.92 2.78 JW1961 126.2 304.1 3.6 0.25 0.90 2.50 SH1963 133.3 302.0 1.2 0.23 0.88 2.00

The following orbits represent the Northern Iota Aquariids. The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010). Once again, a note should be added about Nilsson’s orbit. Since the radar equipment was not in operation from August 25 to September 21, the shower’s August 25th maximum was missed. Thus, it seems probable that the value of W could be larger than given by Nilsson.

w W (2000) i q e a 1961 310.4 146.7 7.9 0.301 0.75 1.21 1961–1965 313.5 152.2 3.2 0.242 0.823 1.37 1968–1969 307.4 153.1 5.2 0.302 0.777 1.36 2002–2008 308.07 159.0 6.9 0.2705 0.827 1.57

As can be seen, the orbits of the two streams are quite similar. Generalizations would give the Southern Iota Aquariids a smaller orbital inclination and perihelion, while the northern branch would possess a smaller argument of perihelion and semimajor axis. One fi nal note should be added about these meteor streams. As noted in Chap. 7, the Tau Capricornid orbit bears a striking resemblance to that of the Northern Iota Aquariids. The only signi fi cant difference is in the date of the nodal passage. The Southern Iota Aquariids could be added to this already striking similarity. What this implies is that the original orbit was perturbed in such a way that its shape and size remained basically unchanged—only the line of nodes and, thus, the longitude of perihelion were affected, which are the easiest changes orbits can experience. During this evolutionary change, three signifi cant events seem to have occurred which are now responsible for the maxima of these three showers. The solar longitudes of these events were 110°, 137°, and 152°. Two possible reasons seem to exist for these three distinct maximums: they are due to planetary perturbations and/or sudden increases in the dust output of the parent body. Alpha Capricornids 177

Alpha Capricornids

Duration: July 4 to August 16 (l = 102–143°) Maximum: July 31 (l = 128°) Radiant: a = 307°, d = −8° ZHR: 6

Radiant Drift: a = UNK, d = UNK V G : UNK km/s

Although the Iota Aquariids might be one of the most confused annual streams, the last few decades have revealed the Alpha Capricornids are not far behind. This visual shower has been well known since the nineteenth century, but as photographic and radio-echo surveys were conducted the shower began to appear more complex. Astronomers of today generally seem to agree that two or three distinct maximums occur during the time the Alpha Capricornids are active.

Discovery

This shower seems to have been ﬁ rst observed in 1871 when N. de Konkoly (Hungary) plotted six meteors from a = 305°, d = −4° during July 28–29.25 Before the end of the decade, two additional observations were made. On 1878 July 28, W. F. Denning (Bristol, England) made a probable observation of this shower when he plotted ﬁ ve meteors from a = 305°, d = −14° and E. Weiss (Hungary) observed the shower from 1879 July 25 to 28, when he plotted four meteors from a = 305°, d = −7°. 26 The Alpha Capricornids became known as a consistent producer of meteors from late July and early August, and in 1899, Denning commented that, at the time of Perseid activity, this shower was rich with very slow and “often bright” meteors. 27 This latter comment of bright meteors has become the trademark of this stream, and Denning provided interesting facts to back this statement in 1920. He pointed out that he and his fellow English observers had determined the real paths of 25 meteors from this shower during the period of July 15 to August 28, which emanated from a mean radiant at a = 305.2°, d = −10.4°. He added that he had personally “seen at least 34 bright meteors from it during the period from July 27 to August 5.”28

Observations

Several visual surveys of the early twentieth century helped to expand the knowledge of this shower. One of the fi rst was R. A. McIntosh’s 1935 paper “An Index to Southern Meteor Showers.” Primarily using observations made by observers in New Zealand from 1927 to 1934, McIntosh combined 15 visual radiant determinations of the Alpha Capricornids to reveal that the radiant 178 9 August Meteor Showers moved from a = 300°, d = −11° to a = 308°, d = −10° from July 22 to 31. A second radiant was also noted which may have been the fi rst indication of the complex nature of the Alpha Capricornids. It moved from a = 300°, d = −9° to a = 305°, d = −8° from July 23 to 31.29 The Alpha Capricornids are not listed in the table of annual meteor showers in C. Hoffmeister’s 1948 book Meteorströme . On the other hand, Hoffmeister’s analysis of the active annual showers began with a preliminary list of 238 radiants. One of those, designated number 56, was given an average activity date of July 29 ( l = 126°), at which time the radiant was at a = 314°, d = −12° and could very well be the Alpha Capricornids.30 Members of the American Meteor Society were quite successful in observing activity; from 1929 to 1953 no less than 21 radiants were observed. The indicated duration of the shower was July 15 to August 5, while the average radiant was at a = 303.1°, d = −12.5°. The Alpha Capricornid stream was detected in the 1960s by both sessions of the Radio Meteor Project. From the 1961 to 1965 session, the duration was determined as July 30 to September 11. The nodal passage came on August 20.2 (l = 146.8°), at which time the radiant was at a = 326.4°, d = −11.9°. 11 For the 1968–1969 session, a similar duration was given as July 25 to September 9, but the nodal passage was determined as August 9.6 (l = 136.6°), while the average radiant was at a = 314.8°, d = −7.1°. 31 Several members of the American Meteor Society observed the Alpha Capricornids from 1970 July 23 to August 1. Hourly rates seemed to reach a fairly consistent maximum of 2–3 between July 30 and August 1.32 This seems fairly typical for Northern Hemisphere observers and, up until this time, most of our knowledge of this meteor shower came from the Northern Hemisphere. But coordinated observations were made on several occasions in the 1970s by observers in Australia, which painted a slightly different picture of this shower. During the period 1969–1980, M. Buhagiar (Perth, Western Australia, Australia) observed 20,974 meteors. Among them was included the Alpha Capricornid shower, the hourly rate of which he gave as 14. 33 The 1979 observations of the Western Australia Meteor Section (WAMS) provided the fi rst hint at a more complex radiant system. The most signifi cant detail offered by these observations was that three distinct dates of activity were revealed: July 22, July 28, and August 5 (the latter being affected by increasing moonlight). The fi rst maximum on July 22 revealed three weak Alpha Capricornid radiants. The longest duration radiant lasted from July 20 to 27 and produced a maximum ZHR of about 2 from a radiant of a = 307°, d = −11°. The other two radiants lasted 2–3 days centered on July 22 and appeared to be subcenters of the longer duration group. One had a ZHR of about 1 and a radiant of a = 304°, d = −14°, while the second had a ZHR of about 1 and a radiant of a = 308°, d = −9°. The second maximum on July 28 produced two radiants with durations of July 27–28. One radiant was located at a = 304°, d = −12° and had a ZHR of about 2, while the other shower was at a position of a = 306°, d = −11° and had a ZHR of about 3. Finally, with moonlight beginning to interfere, the Australian Alpha Capricornids 179 observers found another radiant reaching maximum on August 5. The duration of this shower extended from August 3–5. The ZHR peaked at about 6, while the radiant was at a = 309°, d = −10°.16 Using all observations of WAMS members, section director Jeff Wood has concluded that the ZHR typically reaches 5–10.17 L. R. Bellot Rubio (1990) presented the observations and analysis of the 1989 return of the Alpha Capricornids. In all, 102 meteors were plotted by members of the Spanish Meteor Society (SMS) and the International Meteor Organization (IMO). Although meteors were looked for from July 8 to August 13, Alpha Capricornids were only observed from July 25 to August 12. The ZHR generally stayed within the range of 0.7–2.7 throughout this period. Rates above this range were 4.4 on July 26/27 ( l = 123.88°), 5.3 on July 30/31 ( l = 127.7°), and 3.5 on August 4/5. The population index (r) was determined as 2.09.34 Bellot Rubio (1992) examined over 26,000 meteors and fi reballs recorded by the SMS from 1987 to 1991 to determine the percentage of shower meteors that leave trains. He found 15 % of the Alpha Capricornids leave trains.19 R. Arlt, R. Koschack, and J. Rendtel (1992) examined 3 years of observations during the International Meteor Organization’s “Aquarid Project.” The project spanned 1989–1991, during which time observers plotted 4,989 meteors. In analyzing the data, they found that it was necessary to apply the 23 km/s entry velocity of the Alpha Capricornids, noting that if this was ignored, “the a -Capricornid radiant has disappeared, while a new area of higher density has emerged” further to the east. Because of the low amount of plots for the period of July 21–30, they decided to average the data. The result was a date of July 26 ( l = 123°) and a “rather diffuse” radiant at a = 303°, d = −9°. On August 2–3 (l = 130.5°), they determined the radiant as a = 308°, d = −7°. On August 6 (l = 134°), they determined the radiant as a = 308°, d = −9°. On August 8–10 ( l = 137°), they determined the radiant as a = 318°, d = −8°. The authors noted that although the Alpha Capricornids were quite prominent during the fi rst week of August, the “picture changes completely” in the second week. They said the most prominent shower in this region is the Northern Delta Aquariid radiant. The meteor plots indicate a “slight extension to the west [which] might be identifi ed with the weak a -Capri- cornid radiant.” After further calculations, they concluded that this weak extension was likely caused by meteors with entry velocities of 23 km/s. They determined the radiant drift as +0.9 in a and +0.3 in d per day.35 J. Zvolánková (1993) re-examined meteor observations that were made by astronomers at Skalnate Pleso Observatory (Slovakia) from 1946 August 5 to 14, representing the last 10 days of activity. He said over 3,200 meteors were recorded, of which only 54 belonged to the Alpha Capricornids. After making corrections for individual observers and sky conditions, he concluded that a secondary maximum was found on August 10 (l = 137°), when the ZHR reached 9.36 Enhanced rates were noticed for the Alpha Capricornids on the night of 1995 July 29/30. A. McBeath (1996) said observations from Britain, Bulgaria, Germany, South Africa, and New Zealand indicated ZHRs near ten and reported several fi reballs. The activity was best during 23:00–00:30 UT.37 180 9 August Meteor Showers

The spectrum of an Alpha Capricornid meteor was photographed on 1995 August 2 from Chouzava, Czech Republic. J. Borovicka and M. Weber (1996) said the photograph was obtained using an objective prism camera. Although only a single photograph was obtained, the meteor was seen and plotted by ﬁ ve visual observers at Skalky, Czech Republic. Using the plots and the photograph, the radiant was determined as a = 303°, d = −9°, “which is fully consistent with the radiant of the a -Capricornid meteor shower.” Measuring the spectrum with a microdensi- tometer and calibrating the spectrum using the star Vega, which was in the same frame, the authors wrote, “The brightest lines are the iron lines in the violet region (hardly visible to the human eye) which is not unusual for meteors of similar brightness. Sodium, magnesium, and calcium (both neutral and ionized) are also detected. Chromium and manganese lines are blended with iron.”38 The Canadian Meteor Orbit Radar (CMOR) detected members of this stream from 2002 to 2008. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert said it revealed the duration as July 10 to August 13 ( l = 108–140°). Maximum occurred on July 26 ( l = 123°) from a radiant of a = 303.1°, d = −10.7°. The daily motion of the radiant drift was determined as +0.6° in a and +0.3° in d , while the geocentric velocity was 22 km/s.21

Analysis

F. W. Wright, L. G. Jacchia, and F. L. Whipple (1956) analyzed the orbits of 12 doubly-photographed meteors and established the main parameters of the Alpha Capricornids. The duration was given as July 16 to August 22, while the date of maximum was determined as August 2 (l = 129.0°). The average radiant was a = 308.5°, d = −9.7°, while the daily motion was determined as +52’ ± 2.4’ in a and −2’ ± 2.6’ in d . As can be seen, the motion of d was quite uncertain, with the potential existing for either a northward or southward movement. The authors combined the double-station meteors with 36 single-station meteors to derive a graph showing the scatter of the meteors around the radiant. They found “the mean scatter for the early part of the stream, to July 27, to be 83’. The mean scatter for 10 days around August 1 is 93’, and from August 7 to August 22, there is a fairly large increase in scatter to an average of 155’, quite independent of mass (luminosity).” There was also an increase in the aphelion distance of the meteors between the beginning and end of activity. The authors added that an “irregular frequency distribution of meteors with date” existed. They suggested that “the a -Capricornid stream is a combination of two or more streams.”39 In the 1988 edition of this book, lists of photographic meteors from the United States and the former Soviet Union were reviewed to isolate 29 probable members of the Alpha Capricornid stream. Three distinct streams seemed to be present, as follows: • Stream I: This represents the main stream of the Alpha Capricornid complex. It is based on 17 meteors, and the duration covers July 16 to August 29. The nodal Alpha Capricornids 181

passage occurs on August 1 ( l = 128.6°) from an average radiant of a = 306.7°, d = −8.3°. The radiant’s daily motion is +0.84° ± 0.07° in a and +0.21° ± 0.02° in d . • Stream II: This stream is composed of seven meteors, which indicate the duration of July 15 to August 1. The nodal passage occurs on July 25 (l = 122.2°), at which time the radiant is at a = 302.7°, d = −12.5°. It is especially interesting that its semimajor axis of 2.069 AU is 20–25 % smaller than that determined for the other two streams. • Stream III: This is based on fi ve meteors, which indicate the duration of August 8–21. The nodal passage occurs on August 15 (l = 141.9°), at which time the radiant is at a = 322.4°, d = −13.1°. Numerous astronomers have tried to identify the object responsible for the formation of the Alpha Capricornid stream. E. N. Kramer (1953) was the fi rst to examine the problem when he concluded that the most likely candidate was comet C/1457 L1. H. J. Bernhard, D. A. Bennett and H. S. Rice (1954) suggested a link to periodic comet 72D/Denning-Fujikawa. Wright, Jacchia and Whipple (1956) suggested that comet 45P/Honda-Mrkos-Pajdusakova “may be a parent comet for the later a -Capricornids.”40 Sekanina (1973) indicated that the comet most likely capable of producing this stream was, again, 45P41 ; Sekanina (1976) suggested the Apollo asteroid (2101) Adonis as a candidate.42 L. Neslusan presented a paper at “Meteoroids 1998,” which was an international conference held at Tatranska Lomnica, Slovakia from 1998 August 17 to 21. He said his model of a meteor stream for the periodic comet 14P/Wolf corresponds to a part of the Alpha Capricornids, while comet 45P contributes to another part. 43 Neslusan (1999) looked at the possibility that the comets 14P and D/1892 T1 [now known as 206P/ Barnard-Boattini] were parent bodies to the Alpha Capricornids. He wrote that in studying the meteor streams associated with 14P and 206P, “it is possible to demonstrate that the detectable part of the stream of 14P/Wolf has been split into two rather different strands by planetary disturbances. The fi rst of these strands is over- lapped by the detectable part of [the] stream of [206P], whilst the second strand coincides with the a -Capricornids meteor stream.“ Neslusan added, ”The nucleus of comet [206P] was probably a fragment of 14P/Wolf, separating sometime before 1892, which belonged to the common stream.”44 The issue of the complexity of this stream and its potential associations was examined by I. Hasegawa (2001). He analyzed the orbits of 53 photographic meteors that were detected from 1949 to 1997 and concluded that the Alpha Capricornid stream was actually composed of seven streams. Stream 1 is the main stream and was produced by periodic comet 45P/Honda-Mrkos-Pajdusakova. Hasegawa noted that this stream contained three sub-groups, which represented meteors from the comet’s apparitions of 1785, 1878, and 1938. Stream 2 was another interesting group, which he suggests was produced by the currently lost periodic comet 72D/ Denning-Fujikawa. It is composed of two sub-groups, which represented meteors from this comet’s 1916 and 1951 apparitions. Hasegawa goes on to suggest that stream 3 was produced by the 1952 apparition of periodic comet 141P/Machholz 2, stream 4 was produced by the Apollo asteroid (2101) Adonis, stream 5 was produced by the Apollo asteroid (9162) Kwiila, stream 6 was produced by the unknown 182 9 August Meteor Showers comet that also produced the Daytime Chi Capricornid stream (active during February), and stream 7 was produced by comet C/1457 L1.45 A. Dubietis and Arlt (2004) determined the observational characteristics of the streams within the Aquariid-Capricornid complex using the Video Meteor Database of the International Meteor Organization for 1997–2002. The Alpha Capricornids comprised the largest dataset within the complex, with 7,106 meteors having been recorded. The authors noted that this stream “is a typical representative of ecliptical showers, being rich in bright meteors and fi reballs.” They determined the population index (r) as 2.31 and commented that this was “comparable to the most noticeable ecliptical meteor shower—the Taurids in November.” They said a characteristic feature of the ZHR pro fi le was an “extended background with ZHR ~1.5–2 in the solar longitude range of 110–120, which could not be simply suppressed by varying data selection parameters…. Yet the effect appears to be a structural feature, related to the origin of the meteoroid stream.” They noted the duration of this stream spans July 4 to August 14, while maximum occurs on July 31 (l = 127.7°), at which time the ZHR reaches 5.0.46 The orbits labeled “I”, “II”, and “III” were calculated from photographic meteor orbits. The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a I 266.5 129.3 7.8 0.597 0.785 2.78 II 272.3 122.8 5.4 0.573 0.723 2.07 III 268.3 142.4 1.1 0.582 0.780 2.65 1961–1965 267.4 147.3 0.9 0.630 0.659 1.85 1968–1969 267.9 137.3 6.1 0.620 0.677 1.92 2002–2006 269.93 123.0 6.7 0.5836 0.742 2.26

The Alpha Capricornids were detected in both sessions of the Radio Meteor Project conducted during the 1960s. It should be noted that both sessions poorly covered the period of July 19–25, so that the values of W given below could potentially be smaller. Several objects have been associated with this stream, as noted above. For the comet orbits, the elements represent their discovery apparitions. For the asteroid orbits, the most recently determined orbit is given. The orbit labeled “C/1457 L1” is a medieval comet that might have moved in a short-period orbit. The orbit labeled “14P” is the periodic comet Wolf’s orbit during its 1884 apparition. The orbit labeled “45P” is the periodic comet Honda-Mrkos-Pajdusakova during its 1948 apparition. The orbit labeled “72D” is the lost periodic comet Denning-Fujikawa during its 1881 apparition. The orbit labeled “141P” is the periodic comet Machholz Kappa Cygnids 183

w W (2000) i q e a C/1457 L1 183.28 187.55 7.34 0.7699 1.0 ∞ 14P 172.69 208.00 25.25 1.5720 0.5609 3.58 45P 184.10 233.82 13.16 0.5593 0.8142 3.01 72D 312.66 67.48 6.86 0.7254 0.8287 4.23 141P 149.26 246.18 12.79 0.7525 0.7502 3.01 206P 170.04 208.04 31.26 1.4318 0.5886 3.48 2101 43.21 349.88 1.33 0.4423 0.7640 1.87 9162 235.65 180.16 9.01 0.6052 0.5955 1.50

2 during its 1994 apparition. The orbit labeled “206P” is the periodic comet Barnard-Boattini during its 1892 apparition. The orbit labeled “2101” is the Apollo asteroid Adonis. The orbit labeled “9162” is the Apollo asteroid Kwiila.

Kappa Cygnids

Duration: July 26 to September 1 (l = 123–159°) Maximum: August 17 (l = 145°) Radiant : a = 288°, d = +56° ZHR: 3

Radiant Drift: a = +0.5°, d = +0.2° V G : 23 km/s

This meteor shower is usually hidden by the more spectacular Perseid meteor shower. In fact, meteors from this stream continued to go unnoticed more than 30 years after the Perseids were of fi cially recognized as an annual shower. The fi rst apparent observation of the Kappa Cygnids was made by F. Denza (Italy) while observing the Perseids on 1869 August 11. He gave the radiant as a = 277°, d = +54°. The next observation, which received more widespread attention, came from G. L. Tupman from 1871 August 20 to 25 while sailing between Queenstown, Ireland, and Lisbon, Portugal. His careful plots of observed meteors led him to determine the radiant position as a = 280°, d = +58°. Tupman noticed the similarity to Denza’s radiant.47 During the next few years, several possible observations were made, although there were large variations in the radiant position. W. F. Denning examined the meteor paths of 4,143 meteors observers by members of the Italian Meteoric Association. Six meteors seen from 1872 August 6 to 12 indicated a radiant at a = 283°, d = +63°. Nine more meteors seen from 1872 August 24 to September 14 indicated a radiant at a = 280°, d = +60°.48 While observing the Perseids on the night of 1874 August 11/12, N. de Konkoly (Hungary) observed three meteors from a radiant at a = 290.0°, d = +52.0° and four meteors from a radiant at a = 292.0°, d = +48.0°. 49 Denning fi rst observed the Kappa Cygnids in 1877. As had been the case with Konkoly, Denning saw the fi rst meteors while observing the Perseids, but he continued to observe for several days thereafter. Overall, meteors were seen 184 9 August Meteor Showers from August 3 to 16, with the radiant being determined as a = 292°, d = +48°.2 H. Corder (Writtle, Essex, England) plotted seven meteors from 1875 to 1879, which appeared around August 17. He said the radiant was at a = 298°, d = +55° and he described them as “small quick meteors.”50 The Kappa Cygnids seemed stronger than usual in 1879. Denning said he began observing around 9:30 p.m. on August 21 and “immediately found that a very active shower of slow trained meteors was proceeding from a point in Draco .” He said nine meteors were seen from this region during the next 45 min. He added that 21 meteors were seen in 4 h on that night. During the nights of August 22 and 23, Denning reported seeing “143 shooting stars, including 31 additional paths con- forming to the special shower in Draco, the exact position of which I determined at a = 291°, d = +60°….” Skies were overcast on the night of the 24th, but Denning saw “several fi ne meteors from the same radiant point” through breaks in the clouds on the night of August 25. He wrote, “The Draconids were generally brilliant, with short paths and spark-trails; motions rather slow.”51 Only a few observations were made in the 1880s; however, Denning considered the year 1893 as most notable. Writing in The Observatory in 1893 September, Denning wrote how he was “struck with the frequency and brightness of meteors from a con- temporary radiant on the N.W. limits of Cygnus near the star Kappa. Altogether I observed 28 paths directed from the point 292°, +53°, and must have missed others.” The activity was noted from August 5 to 16. He described the meteors as “rather swift, with short courses, and in a majority of cases the nucleus, before fi nal disruption, burst out very suddenly and left a short streak, marking the spot where it occurred.” Denning added that other British observers independently noted the unusual activity from Cygnus—most notably Corder (Bridgwater, Somerset, England), J. Evershed (Kenley, London), and R. A. Batt (Leyton Road, London, England)—with several bright fi reballs being noted from the region from August 13 to 17. One very notable fi nding made by Denning involved the eastward movement of the radiant, with his observations of August 5, 6, and 8 revealing a position of a = 290°, d = +53°, his observations of August 13 and 14 revealing a position of a = 292°, d = +53°, and his August 16 observations indicating a position of a = 296°, d = +53°.52 Since most of the August meteor observations made during the nineteenth century were typically centered on the date of the Perseid maximum, the actual date of the greatest Kappa Cygnid activity was not clearly understood until early in the twentieth century. Observers then began to notice that the shower was strongest around a week following the Perseid maximum. For example, in 1922, the English observers J. P. M. Prentice and A. G. Cook independently plotted more meteors from the Kappa Cygnid shower than for any other August shower, excluding the Perseids. The former observer plotted 12 meteors from August 15 to 20, from an average radiant at a = 291°, d = +52°. Cook plotted 18 meteors during August 15–17, 20, and 26, from a radiant at a = 291°, d = +50°. She called it the “Theta Cygnids.”53 A probable third independent observation came from across the Atlantic as W. H. Christie (Victoria, British Columbia) plotted six meteors from a = 299.5°, d = +50.8° on the night of August 21/22.54 Kappa Cygnids 185

Other interesting observations of this shower came in the years that followed. In 1925, the Russian Society of Amateurs plotted 23 meteors from August 16 to 20, and revealed the average radiant at a = 291.4°, d = +54.0°.55 Members of the American Meteor Society (AMS) made two excellent early observations of the shower on August 14 of both 1936 and 1951. In the fi rst year, B. S. Whitney (Oklahoma, USA) plotted seven meteors from a = 285°, d = +57°,56 while, in the latter year, R. Widner (Oregon, USA) plotted fi ve meteors from a = 289°, d = +50.5°.57 Curiously, despite the frequent appearance of this shower in various observational records, it has just as frequently been overlooked. In the previous two paragraphs, the observations by Christie, Whitney, and Widner mark the only Kappa Cygnid observations among over 6,000 radiants on record with the AMS. Similarly, in C. Hoffmeister’s book Meteorströme, not only is this shower overlooked as an annual producer of meteors, but among the 5,406 visual radiants obtained by German observers from 1908 to 1938, only one observation barely qualifi es as a Kappa Cygnid radiant. On 1930 August 21 (l = 147.2°), a radiant was detected at a = 289°, d = +61° and was given a weight of six on a scale of 1–10.58 Although additional visual observations were occasionally reported in the 1940s and 1950s, a newer more substantial view of the Kappa Cygnids was fi nally achieved in 1954 when F. L. Whipple published the fi rst list of photographic meteor orbits. He determined the orbits of 144 meteors from double-station photographs, and fi ve were identi fi ed as Kappa Cygnids. These meteors indicated a duration of August 9–22, while the average radiant was a = 291.5°, d = +53.0°. Whipple commented that the orbits indicated this stream has a “short-period comet orbit with high inclination, period 7–8 years, [aphelion] of 7–8 AU. The long duration…suggest remnants of a large comet.”59 The next important event in meteor studies involved radio-echo observations, and the Kappa Cygnids were fi nally recognized by this technique in the early 1960s. Z. Sekanina (1973) detected this stream during the 1961–1965 session of the Radio Meteor Project. Activity was detected from August 23 to 28 from an average radiant of a = 298.9°, d = +62.4° and a geocentric velocity of 25.9 km/s. Although the date of the nodal passage was given as August 26.1 (l = 152.5°),60 it should be noted that the radar equipment was not in operation from August 18 to 22, so that an earlier nodal passage and subsequent average date of maximum activity is quite probable. The stream’s occasional disappearance, noted earlier among visual observations, is also evident in the second session of the Radio Meteor Project from 1968 to 1969. Despite the radio equipment being operated from August 11–15, 17–18 and 25–30, the Kappa Cygnids were either too weak to be delineated by the computer or totally nonexistent. Why the Kappa Cygnids are absent in some years cannot be answered since the stream has never been the focus of intensive observations. What is apparent is that the hourly rates of the shower do seem to vary. The fi rst determination of the Kappa Cygnid activity levels came from an observation by Denning on 1879 August 22, when 52 of this shower’s meteors were seen during 5 h of clear sky, or slightly over ten meteors an hour.61 With increased visual observations, the variations in activity have been especially noted in recent years. In 1974, the Hungarian Meteor Team obtained a peak ZHR of 23.6 ± 5.1. 62 In 1982, observers of the Nippon Meteor 186 9 August Meteor Showers

Society estimated a peak ZHR of 14.1,63 while members of the Dutch Meteor Society obtained a maximum ZHR of only 2–3 in 1984.64 L. R. Bellot Rubio (1992) examined over 26,000 meteors and ﬁ reballs to determine the percentage of shower meteors that leave trains. He found 4 % of the Kappa Cygnids leave trains.19 The Kappa Cygnids showed higher rates than normal in 1993 and a number of bright meteors were photographed. M. C. de Lignie and K. Jobse (1997) set up video cameras in Puimichel and Tourves in southern France, with the intention to “conﬁ rm the clear presence of the k Cygnids….” From August 15 to 18, they photographed 84 total meteors, of which 60 “were suitable for measurement and triangulation.” Five Kappa Cygnids were detected. The radiant was at a = 287.1°, d = +52.0°, and the geocentric velocity was determined as 22.6 km/s.65 A. Grishchenyuk (1993) wrote that observers in Crimea (Ukraine) were clouded out on the night of the Perseid maximum, but did have clear skies on August 13/14. They saw several meteors from the Kappa Cygnid radiant, noting a ZHR of 13.8, and radiant diameter of 4°, and a radiant at a = 290.3°, d = +52°.66 After sifting through the published lists of photographic meteor orbits nine meteors can be isolated as are probable members of the Kappa Cygnid stream. They indicate a duration extending from July 26 to September 1. The date of the nodal passage is August 17 ( l = 143.4°), at which time the radiant is at a = 287.6°, d = +53.8°. The indicated daily motion of the radiant is +0.50° ± 0.06° in a and +0.15° ± 0.12° in d . The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1954–1977” represents those photographic meteors accumulated from papers published from 1954 to 1977.

w W (2000) i q e a 1961–1965 203.1 153.2 42.9 0.979 0.621 2.58 1954–1977 202.7 144.1 38.0 0.977 0.793 4.72 1993 204.2 143.6 34.8 0.976 0.698 3.26

August Eridanids

This somewhat diffuse radiant was noted while examining the 39,145 radio meteor orbits obtained by Z. Sekanina during the Radio Meteor Project of the 1960s. Six radio meteors were identi ﬁ ed which suggested a duration of August 2–27. Maximum seems to occur around August 11/12 from an average radiant of August Eridanids 187

a = 49.6°, d = −4.9°. What makes this stream orbit especially interesting is its similarity to the orbit of periodic comet 273P/Pons-Gambart. The orbits of the radio meteors and comet are shown below.

w W (2000) i q e a Meteors 17.1 320.6 140.2 0.985 0.644 4.09 273P 20.19 320.43 136.40 0.8103 0.9755 33.04

No visual evidence exists to directly support this radiant; however, there is strong evidence of activity 8–10° north among the records of the American Meteor Society (AMS) and the radiants published by C. Hoffmeister in his 1948 book Meteorströme . Among the AMS records, the most interesting are those of C. E. Worley (California, USA), when he saw activity from this radiant on three consecutive nights in 1954. He plotted ﬁ ve meteors from a = 45.0°, d = +4.8° on August 7.4, 5 meteors from a = 48.0°, d = +1.5° on August 8.4, and 7 meteors from a = 48°, d = +2° on August 9.4.67 The earliest observed radiant from this stream came from H. L. Alden (Virginia, USA), when he recorded three meteors from a = 45.0°, d = +4.8° on 1926 August 11.7.68 Additional AMS radiants were reported in 1929, 1941, and 1958. Among the list of 5,406 German radiants compiled by Hoffmeister, are three additional radiants which possess positions similar to those reported by the AMS. They were detected from 1937 August 8 to 19, while Hoffmeister was observing from South-West Africa (now Namibia). By combining these radiants with those of the AMS, the following parabolic orbit has been computed.

w W (2000) i q e a 351.4 318.1 151.3 1.002 1.0 ∞

The potential separation between the radio-echo data and the visual data could indicate that the August Eridanids are very old, indicating that mass separation has occurred. Comet Pons-Gambart was seen for a month in 1827. Although its orbital period was determined as 57.5 (with a probable error of ±10 years) it was considered lost after attempts to ﬁ nd it failed. It was accidentally rediscovered in 2012 November. The precise positions quickly allowed a link to the 1827 apparition and revealed that the orbital period was actually 188 years. 188 9 August Meteor Showers

Daytime Gamma Leonids

This daylight meteor shower was detected by two radio-echo surveys conducted during the 1960s, but has not been seen since. It is a signiﬁ cant stream, as it may represent a recurrence of January’s Delta Cancrid stream. C. S. Nilsson (1964) was the ﬁ rst to observe this stream, when the radio program he was directing at the University of Adelaide (South Australia, Australia) detected four meteors from 1961 August 18 to 22. The radiant was determined as a = 152.7°, d = +21.0°,69 while the following orbit was computed.

w W (2000) i q e a 90.6 148.7 7.5 0.595 0.75 2.38

The stream was also detected during the second session of the Radio Meteor Project, the equipment of which was located in Havana, Illinois (USA). Z. Sekanina (1976) said the daylight shower was observed from 1969 August 14-September 12. The date of the nodal passage was given as August 25.4 (l = 151.8°), at which time the radiant was at a = 155.5°, d = +20.1°. The geocentric velocity was determined as 22.0 km/s.70 The following orbit was computed.

w W (2000) i q e a 87.3 152.5 7.0 0.571 0.710 1.97

Sekanina considered that a slight chance existed that this stream was associated with the Delta Cancrids of January. The D-criterion was given as 0.285, so that it was a borderline association.

Perseids

Duration: July 23 to August 22 (l = 277–286°) Maximum: August 12 (l = 140°) Radiant: a = 48°, d = +57° ZHR: 100

Radiant Drift: a = +1.40°, d = +0.25° V G : 61 km/s

This is the most famous of all meteor showers. It never fails to provide an impressive display and, due to its summertime appearance, it tends to provide the majority of meteors seen by people not necessarily looking for meteors. Despite an observational history spanning several centuries, it took a while for its annual nature to be fully appreciated. Perseids 189

Discovery

The earliest record of Perseid activity appears in the Chinese annals, where it is said that in the year 36 on July 15 [converted to Gregorian calendar], “at dawn more than 100 small meteors fl ew on all four sides.”71 Numerous references appear in Chinese, Japanese, and Korean records throughout the eighth, ninth, tenth and eleventh centuries. Despite the Chinese reporting showers in consecutive years, such as from 713–714 to 924–926, there is no record that they ever recognized that they were seeing an annual display. During the next seven centuries, the Perseids were only noted on six occasions, by the Koreans in 1106 and by the Chinese in 1451, 1466, 1590, 1625, and 1645. A few observations began to show up during the eighteenth century. W. Hamilton saw the eruption of the volcano Vesuvius in 1779 August. In a letter written to J. Banks that was published in a 1780 volume of the Philosophical Transactions of the Royal Society of London, he noted that on August 9, at about 9:00 a.m., the volcano’s “fourth fever-fi t … began to manifest itself….” He said lava poured out around 2:00 p.m. and that the eruption had ceased by 7:00 p.m. Hamilton then noted, “It was universally remarked, that the air this night, for many hours after the eruption, was fi lled with meteors, such as are vulgarly called falling stars; they shot generally in an horizontal direction, leaving a luminous trace behind them, but which quickly disappeared.”72 C. Gannett wrote that on 1781 August 8, “Meteors appeared in great numbers, shooting, in general, from north-west to south-east.”73 N. Webster included the following account in volume 2 of his A Brief History of Epidemic and Pestilential Diseases : During the extreme heat which introduced the pestilence of the last summer, 1798, about the 9th of August, the small meteors or falling stars were incredibly numerous, for several nights. They almost all shot from the north-east to the south-west, and succeeded each other so rapidly as to keep the eye of a curious spectator almost constantly engaged. 74 There are two sources published during the eighteenth century which indicate that August was a month when meteors are most likely to be seen. The fi rst source is Introductio ad Philosophiam Naturalem by P. van Musschenbroeck. Published in 1762, it notes that “Falling stars are more numerous in August that at any other time of the year based on the trails observed, at least in Belgium, Leyden, and Utrecht.”75 The second source is the Pennsylvania (USA) newspaper National Gazette, which published an article on meteors in the 1792 August 15 edition, which stated, “It is a fact no less certain, than worthy of remark, that in the month of August there are more meteors to be observed in the atmosphere, than at any other period of the year….”76 Admittedly, these statements were very matter-of-fact, supplying no evidence to back them up; however, one cannot help but wonder what inspired these statements, since published accounts of meteor shower observations are rare during the eighteenth century. An interesting article appears in an 1821 issue of the Philosophical Magazine and Journal. J. Farey discussed something that he noticed in the meteorological observations of W. Burney in the year 1820. Burney saw a total of 131 meteors during that year, 80 of which were seen in August. Farey continues, “The singular fact, of the month of August having furnished so very disproportioned a number of 190 9 August Meteor Showers these observations, is accompanied by the mention, that 35 of these were observed in 1 h, which preceded midnight on the 9th of August last….” He added that some of the meteors were said to have left “sparkling trains” that lasted several seconds. Farey asked Burney to “commence a series of more minute observations on Shooting Stars and Meteors” in order to answer questions about these objects.77 J. Graziani (Rome, Italy) observed in 1826 and 1827 on the nights of August 14 and 15. In the fi rst year, he said, “there were more than 50 per hour in the two nights indicated.” He observed from 10:00 to midnight and said most of the meteors moved from northeast to southwest.78 In 1827, T. F. Forster wrote a book titled The Pocket Encyclopaedia of Natural Phenomena. He claimed that a manuscript by the name of Ephemerides Rerum Naturalium was preserved in the library of Christ’s College (Cambridge, England). Written by a monk in the tenth century, the manuscript lists natural phenomena for each day of the year and for August 10 was listed “meteorodes.”79 In the same book, Forster later wrote, “In the month of August meteors of all kinds are more common than at any other time of the year.” 80 It should be noted that no other author ever located the text at Christ’s College, despite searches that have been made since the mid-nineteenth century. The Perseid meteor shower reached maximum around July 22 during the tenth century, based on calculations, as well as the Chinese observations in 924, 925, and 926 that were noted earlier. About a decade later, Forster provided observations he had made of meteor showers beginning in 1806 to L. A. J. Quetelet (1837). This included several observations of the Perseids.81 There are some who believe Forster deserves credit for the discovery of the Perseids. He certainly predates the “of fi cial” discoverers of the shower’s annual occurrence by about a decade, but his failure to publish his observations to support his statement of meteors being more abundant in August relegates him to not much more than a footnote in the history of this shower. With respect to the above statement concerning the earlier maximum of the Perseids, this is a fact that is based on almost 2,000 years of observations. This bears heavily on a long-time statement that the Perseids have been referred to as the “tears of St. Lawrence.”82 The statement is commonly explained as indicating that meteors seem to be more abundant during the festival of that saint on August 10th. The festival is celebrated at that time, because Lawrence of Rome was put to death on that date in the year 258. Lawrence was an archdeacon of Rome and was in charge of the riches of the church. At the beginning of August in 258, Roman emporer Valerian ordered that all individuals holding high positions in the church were to be put to death. Among the fi rst to die was Pope Sixtus II. Lawrence immediately began distributing the wealth among the poor, but sent the Holy Grail to his parents. The prefect of Rome demanded that Lawrence turn over this wealth, but he refused, which led to his being put to death. In 258, the Perseid maximum would have occurred around July 14. The tradition of the “tears of St. Lawrence” could not have begun much earlier than late in the eighteenth century! Additional Perseid observations have been found that were made in 1830 and 1836. S. L. Andrews (Dartmouth College, Hanover, New Hampshire, USA) noted in his journal that the aurora borealis was “very bright” on the evening of 1830 August 10. He added, “Meteors (shooting stars) are darting across the heavens Perseids 191 almost every minute; their apparent size varies from that of a spark to that of the planet Venus.”83 F. H. Walferdin (Bourbonne-les-Bains, France) saw this meteor shower on 1836 August 8. He noted that he observed during 2½-hour periods between 9:30 and 11:30 p.m. He said he counted 156–158 meteors and added, “I have not seen less than two per minute.”84 Despite all of the observations discussed above, Quetelet (Brussels Observatory, Belgium) is widely recognized as the person who “discovered” that a meteor shower occurred annually in August. He fi rst made mention of this possibility in a presentation during the 1836 December 3 session of the Royal Academy of Sciences of Brussels, Belgium. He noted that H. W. Brandes had observed 140 meteors in 2 h while observing in Wroclaw, Poland on 1823 August 10 and added that E. F. F. Chladni had mentioned a report of numerous meteors seen on 1815 August 10. After the presentation, D. Sauveur noted that he had “observed a very considerable number of shooting stars” on the night of 1836 August 8/9. Quetelet commented “that this period presents a unique agreement with that of August 10….” 85 In the Annuaire de l ’ Observatoire Royal de Bruxelles pour l ’ an 1837 , Quetelet speci fi cally noted, “I have also thought that I remarked a greater frequency of these meteors in the month of August (from the 8th to the 15th).”86 At a presentation to the Royal Academy of Science of Brussels on 1837 March 4, Quetelet said he, “continues to believe that it is not only the middle of November, which is remarkable for the large number of occurrences of these meteors, but the middle of August, especially the 10th, that also deserves our attention.” Quetelet said he accidentally found two accounts of falling stars in the records of the Brussels Observatory. The fi rst was made by him on 1834 August 10, when he noticed a couple of very bright meteors, as well as “quite numerous” shooting stars. Quetelet continued by noting “many shooting stars” on the 11th and “very beautiful shooting stars” on the 15th. The second account was made by E. Mailly (one of Quetelet’s students) on 1835 August 10, where he wrote, “the evening of the 10th to 11th was notable for a large number of shooting stars.”87 The year 1837 became an unusual year for this meteor shower, in that observations were not only made in France, as a result of Quetelet’s announcement, but in other countries as well, purely by accident. This perhaps brings about the thought of a larger than normal display. At Paris Observatory (France), F. J. D. Arago provided two reports on 1837 August 14. First, his son and a friend were in the garden of the observatory on the night of August 10/11, where they counted 107 meteors from 11:15 p.m. to 12:15 a.m. Second, student astronomers A. Bouvard and P. A. E. Laugier saw 184 meteors in about 3 h from 12:37 to 3:26 a.m. on August 11 and added that the largest number seemed to point to Taurus.88 G. C. Schaeffer (New York, USA) had observed the November meteor display of 1836 and began watching for meteors as often as possible, noting their direction and number. He noted, “For 2 or 3 weeks previous to the 9th of August [1837] , a large number was seen….” Schaeffer then wrote, “About 8 o’clock on the evening of the 9th, my attention was directed to several meteors, which, notwithstanding the bright moonlight, were very conspicuous. Following up the usual observations upon direction, it was soon found that there was a common center of radiation.” Schaeffer noted that few of the meteors were seen near the radiant, with most 192 9 August Meteor Showers

“averaging a distance of 90° from it.” Although this made it diffi cult to pinpoint the exact radiant point, he did estimate it was near a = 55° d = +30°. Schaeffer said that from 8:00 p.m. until nearly 3:00 a.m., he saw between 200 and 300 meteors.89 E. C. Herrick (New Haven, Connecticut, USA) accidentally observed this display of meteors on 1837 August 9. He said that from 9:00 to 10:00 p.m., “I noticed in the northeastern quarter of the heavens (that being the only portion visible at my station,) from 12 to 15 shooting stars of uncommon brilliancy, most of which left trains of considerable extent. The moon was about 2 h high in the west at the time, and doubtless concealed some of inferior lustre.” He added, “many of them proceeded in a southwestern direction from a region in the northeast.”90 Herrick cited the observation by Schaeffer, as well as another made in Georgia that same night, as con fi rmation of his observation. He also mentioned a statement made by E. Loomis in 1835 that Brandes and his associates saw 140 meteors in less than 2 h on 1823 August 10. From these observations, Herrick wrote, “These facts appear to me suf fi cient to render highly probable the periodical occurrence of an unusually large number of shooting stars on or about the 9th of August.” 91

Observations

Following the announcements in 1836 and 1837 that annual activity occurred on August 9/10 of each year, observers were met with a last quarter moon in 1838 and reported hourly rates of 30–50; however, 1839 proved to be perfect for a number of observers and they were in for a surprise. Herrick was observing on the night of August 9/10, with F. Bradley, C. P. Bush, and A. B. Haile. They watched for 5 h and counted 691 different meteors. Throughout the night, the frequency of meteors increased, as they counted 194 different meteors from 1:00 to 2:00 a.m. on the 10th and then 34 different meteors, in the 7 min following 2:00 a.m. Herrick noted, “The meteors were increasing in frequency when we left the ﬁ eld, and had we continued observation until 4 o’clock, we should doubtless have seen in all more than a thousand.” On the night of August 10/11, Herrick observed with Bush, Haile, and A. D. Stanley. During 3 h, they counted 491 different meteors and Herrick indicated that rates were still increasing when they quit observing at 1:00 a.m. Herrick reported several additional accounts from other observers and wrote, “It is evident from the observations above detailed, that on the nights of August 9th and 10th, 1839, shooting stars were much more abundant than usual….”. 92 According to A. von Humboldt’s 1852 edition of Cosmos: A Sketch of a Physical Description of the Universe, E. Heis (Münster, Germany) also saw high numbers of meteors on the night of 1839 August 10, giving the rate as 160 per hour.93 The year 1841 was another special one for this meteor shower, as observations were made from several locations in the United States and Europe. A. Colla (Parma Observatory, Italy) provided a very complete series of observations on three consecutive nights. Observing from 8:44 p.m. to 2:14 a.m. on August 9/10, he recorded 80 meteors. This number jumped to 283 meteors on August 10/11, Perseids 193 when he observed from 8:47 p.m. to 3:40 a.m. Colla noted seven consecutive hours when he saw nearly 40 meteors each hour. He said 25 of the 283 meteors left trains, 203 were white in color, and 191 moved at a fast speed. He watched the sky from 8:37 p.m. until midnight on the night of August 11/12 and saw a total of 82 meteors. Colla added that A. Puastalle, who was with four observers in the tower of the town hall, reported 257 meteors on the night of August 9/10 and 440 meteors on the night of August 10/11. 94 J. Locke (Cincinnati, Ohio, USA) observed with an assistant on the night of August 10. From 9:00 to 10:00 p.m. they counted 60 meteors which were “mostly brilliant, rocket-like, and left a phosphorescent track.” He added, “The forty nine parallel meteors had courses which mostly, if prolonged, would fall between a and b of Perseus….” Locke said only half the sky was visible.95 Observations of the Perseids were reported annually thereafter, even during years of bright moonlight. According to A. S. Herschel, hourly rates between 1842 and 1855, as reported by Herrick, Heis, J. F. J. Schmidt (Athens Observatory, Greece), and R. Wolf (Zurich, Switzerland), ranged from 19 to 51.96 The rates began to change again in 1861, when numerous observers began reporting rates of over 70 per hour on the night of August 10/11. This included regular observers of this shower, such as A. Secchi (Roman College Observatory, Italy), who indicated a rate of 89 per hour from 9:00 to 10:30 p.m., 97 R. A. Coulvier- Gravier (France), who reported an average hourly rate of 73 for 6 h,98 and B. V. Marsh (Burlington, New Jersey, USA), who noted 85 meteors between midnight and 1:00 a.m.99 The full moon interfered with observations in 1862, yet a very complete series of observations by Coulvier-Gravier revealed that the best nights were August 10 and 11, when a 3.75 h session each night revealed hourly rates of 54.2 and 52.3, respectively.100 Dark skies in 1863 again brought higher rates to observers. Heis observed with several of his pupils for seven nights. On the night of August 10/11, they saw 601 meteors in 4.25 h. A total of 547 meteors were plotted on this night. The highest total meteor rates for the night were 144 from 10:00 to 11:00 p.m., 166 from 11:00 p.m. to midnight, and 158 meteors from midnight to 1:00 a.m. The Perseid radiant was determined as a = 45° d = +56°. Heis also told of other reports he had received, including one from M. Neuhaus (Gaesdonck, Germany), a teacher who observed with seven high school graduates. On the night of August 10/11 they counted 105 meteors from 9:17 to 10:00 p.m., 210 from 10:00 to 11:00 p.m., and 248 from 11:00 to midnight. 101, 102 Denning’s analysis in 1879 revealed that the corrected rates in 1863 were 109–215 per hour.103 While meteor observers and researchers were trying to understand the unexpectedly high activity during the early 1860s, a new comet was independently discovered on 1862 July 16 by L. Swift and July 19 by H. P. Tuttle. The comet was followed until October 31. During the next couple of years, several astronomers were busy determining its orbit and were coming to the conclusion that it had a period of about 120 years.104 194 9 August Meteor Showers

G. V. Schiaparelli calculated the orbit of the Perseids between 1864 and 1866 and discovered a very strong resemblance to periodic comet Swift-Tuttle. In a letter to Secchi, he suggested they were related and that “the great comet of 1862 is none other than one of the Perseids of August, and probably the largest of them all.”105 This was the fi rst time a meteor shower had been positively identi fi ed with a comet and there is no doubt that the high Perseid rates of 1861–1863 were directly due to the appearance of the comet. Although rates were still somewhat high in 1864, generally “normal” rates persisted throughout the remainder of the nineteenth century; however, the maximum hourly rates of the Perseids seemed to be declining during the early years of the twentieth century. From 1901 to 1910, Denning reported good displays in 1901, 1904, 1907, 1909, and 1910, when meteors were seen falling at 30 or more per hour, even on nights with haze and passing clouds. With the full Moon on 1908 August 10, Denning still reported 15 Perseids in 1.5 h. But 1911 and 1912 were far different. With a full Moon interfering with observations on 1911 August 10 and 11, Denning reported two Perseids in 1.5 h on the fi rst night and one Perseid during 1 h on the second night. A hazy sky was present on 1912 August 10. Denning reported that the stars appeared dim and that during 2.25 h, two Perseids were seen; however, he did see 12 Perseids in 1.5 h on the next night, despite clouds. Nevertheless, Denning asked, “Have the Perseids nearly deserted us?” He wrote, “Making every allowance for hard conditions in 1911 and 1912, I consider these meteors to have been very unusually scarce, and am led to believe that something must have occurred to bring about such a very marked decline in the splendor of the display.”106 Perseid activity did not improve greatly after 1912. During the decade of the 1910s, very few articles appeared in the usual periodicals and magazines describing Perseid activity. E. F. Sawyer did submit a short note to the 1915 October issue of the Astronomical Journal . He said he watched for meteors from 10:00 to 11:00 p.m. on the nights of 1915 August 9, 10, 11, and 13, noting that it was cloudy on August 8 and 12. He said he saw a total of 19 meteors, with 15 being Perseids. Fourteen Perseids were seen on the night of the 11th. He noted, “Very meagre displays for some years.”107 Interestingly, the Perseids experienced three outbursts from 1920 to 1945. Denning reported in the 1920 October issue of The Observatory that the Perseids were “of rather unusual abundance” in 1920. He said that on August 11 A. G. Cook recorded the paths of 112 meteors in 3 h, while J. P. M. Prentice recorded the paths of 135 Perseids in nearly 5.5 h.108 Since they were busy recording the paths, a number of meteors would have been missed. C. P. Olivier reported in the 1931 October and November issues of Popular Astronomy that numerous reports had been received concerning observations of the Perseids in 1931. He noted that observers with unobstructed views, a clear sky, and good eyesight reported rates “certainly over one per minute after midnight on both August 11 and 12.” 109, 110 Olivier reported in the 1945 December issue of Popular Astronomy that an “excellent shower” was present on the nights of August 11/12, 12/13, and 13/14, with several observers reporting hourly rates of over 120. Olivier wrote, “I believe there were Perseids 195 fewer conspicuous ones than might have been expected from such large totals. However, the return was heartening in that it indicated there are no real proofs that this most regular and rich of all annual showers is dying out.”111 The Perseids were consistently observed in the 1950s and 1960s, with hourly rates typically within the range of 40–60. P. M. Millman (Canada) even noted rates over 80 per hour during the 1955 display.112 Some excitement was generated in the early 1970s, when B. G. Marsden (1973) predicted that periodic comet 109P/Swift-Tuttle would arrive at perihelion on 1981 September 16.9 (±1.0 years). 113 The potential existed for enhanced activity that could occur a year or two before and after the perihelion date—as happened during the comet’s previous perihelion passage in 1862. This excitement seems to have initially been fully justi fi ed, as the average rate of 65 per hour during 1966–1975 suddenly jumped to over 90 per hour during 1976–1983—with the high being 187 in the latter year. Although meteor observers seemed content with their observations of the enhanced activity from Swift-Tuttle, comet observers were less enthu- siastic as the comet was not recovered. But Marsden’s 1973 paper was not fully committed to the 1981 perihelion date. Although this date was considered best, based on the comet’s calculated orbital period of about 120 years, Marsden thought that a comet seen by I. Kegler in 1737 was a better fi t to the motion of the comet… except it required Swift-Tuttle to have a period of over 130 years. So, an additional prediction was included in the paper, so that if the comet was not seen around 1981, it might pass perihelion around 1992 November 25. Following the 1983 peak, hourly rates for the Perseids declined. With a full moon occurring just a day before maximum in 1984, the Dutch Meteor Society still reported unexpectedly high rates of 60 meteors per hour. 114 In 1985, reported rates generally fell between 40 and 60 per hour in dark skies,115 and results were generally the same in 1986.116 Thus, the hourly rate of the Perseids had dropped back to normal. There was an interesting feature in the 1988 Perseid display. P. Roggemans (1989) was summarizing the display when he noted the occurrence of two maxima: the fi rst at l = 139.5° and the second at l = 140.0°. He noted a “deep decrease in activity” at l = 139.7° and added that the second maximum was the main one. Roggemans said the double maxima had also shown up in the analysis of the 1985 display, but “this phenomenon was not immediately interpreted as a real feature.” Observational effects and observers with low perceptions at the time of the “deep decrease” were ruled out as responsible. Roggemans suggested the only explanation was that Perseid activity “was just lower” between the two maxima.117 [ Note that the values of l above were originally for equinox 1950, but were converted to 2000 to better compare to the values that follow. ] The double maxima were again noted during the 1989 display. R. Koschack and Roggemans (1991) said the fi rst peak occurred at l = 139.6°, while the second occurred at l = 140.0°. The following idea was put forth: “Since this feature was not noticed in the 1960s and 1970s, the suggestion is raised that the peak at l = 139.6° might possibly have been caused by an injection of new cometary material from the unnoticed perihelion passage of comet Swift-Tuttle around 1980–1981.”118 196 9 August Meteor Showers

There were people who were still hoping that Marsden’s secondary prediction of Swift-Tuttle arriving at perihelion in 1992 would come true. As a result, interest in the Perseids increased as the 1990s dawned. Moonlight strongly interfered in 1990, but a strong Perseid display was present in 1991. The fi rst reports came from Japan and France. Y. Taguchi, observing near Kiso Observatory (Japan), reported hourly rates of 64 on August 12.62, 352 on August 12.66, and 62 on August 12.70. At Haute Provence, France, P. Aneca, B. de Pontieu, J. Deweerdt, and J. van Wassenhove reported individually seeing 280–300 meteors during 2 h centered on August 13.08.119 Additional reports came from other countries throughout Europe and North America. Another outburst was observed in 1992. Reports from A. Mizser (Hungary) and P. Jenniskens (Netherlands) indicated high visual activity was noticed from August 11.79 to August 11.87, while J. Rao (New York, USA) said U.S. radio amateurs indicated high activity during August 11.75–11.82. The peak was said to have coincided with the nodal longitude of Swift-Tuttle.120 R. Koschack, R. Arlt, and J. Rendtel (1993) analyzed the 1991 and 1992 displays and detected two peaks in each year. In 1991, the fi rst peak came at l = 139.58°, when the ZHR was over 350, while the second peak came at l = 140.00°, when the ZHR was over 120. In 1992, the fi rst peak came at l = 139.50°, when the ZHR was over 220, while the second peak came at l = 140.06°, when the ZHR was over 90. In studying the population index of the display, they noted that the core of the stream was characterized by r = 2.10–2.15, while the outburst was characterized by r = 2.15. They wrote, “This means the mass distribution of the fi lament which caused the outburst does not differ from that of the ‘regular core’ of the stream.”121 Periodic comet 109P/Swift-Tuttle was recovered on 1992 September 26. The observations indicated a perihelion date of 1992 December 12. Most importantly, Marsden stated that the period was 135 years, which con fi rmed the identity with Kegler’s 1737 comet and revealed large discordances with observations made in 1862.122 With two outbursts having occurred and the comet having been found, excitement grew for the expected 1993 outburst. Predictions indicated that Europe was the best location for viewing, and observers from around the world fl ocked into central Europe. The maximum was predicted to occur on August 12.05 UT, and some astronomers were suggesting the possibility of a meteor storm.123 The National Aeronautics and Space Administration (NASA) announced on July 31 that they were going to delay the launch of the Space Shuttle Discovery until at least August 12, because of the predicted enhancement of the Perseid meteor shower.124 Observations on August 11 indicated a slow rise in the ZHR from 60 to 90. The fi rst sign of the expected outburst came on August 12.00, but the increasing number of meteors reached a plateau of 145–150 for about an hour, which saw the predicted maximum come and go. Thereafter, the increase resumed, reaching a peak ZHR of about 300 on August 12.14 (l = 139.42°), more than 2 h later than the prediction. The ZHR dropped thereafter, but increased to over 100 by August 12.93 (l = 140.3°), which was the time of the traditional Perseid maximum. The population index started at r = 2.00 on August 11.08 and steadily increased. For about 17 h, which covered most of the outburst up to the traditional peak, the population index was r = 1.76–1.81. Thereafter, it dropped to r = 1.99 by August 13.00.125 Perseids 197

Enhanced displays of the Perseids continued for a few more years, reaching a ZHR of 250 in 1994, 160 in 1995, 120 in 1996, 137 in 1997, 110 in 1998, and 104 in 1999. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones (2008) identi ﬁ ed 361 meteors from the Perseids stream in the data acquired by the Canadian Meteor Orbit Radar from 2002 to 2006. These indicated a duration of August 6–15 (l = 134°– 142°), with maximum occurring on August 12 (l = 139.5°) from a radiant at a = 46.9°, d = +56.9°. The radiant drift was determined as +1.23° in a and +0.27° in d , while the geocentric velocity was determined as 62.1 km/s.126 Brown, Wong, Weryk, and P. A. Wiegert (2010) identiﬁ ed 2,024 meteors from this stream in the data acquired by the Canadian Meteor Orbit Radar from 2002 to 2008. The duration was given as July 26 to August 20 (l = 123°–147°). Maximum activity came on August 13 ( l = 140°) from a radiant at a = 48.0°, d = +57.2°. The geocentric velocity was determined as 61.4 km/s. They also gave the daily motion of the radiant as +1.39° in a and +0.29°.21

Perseids 160

140

120

100 Z H 80 R 60

0 100 110 120 130 140 150 160 Solar Longitude

This represents over a decade of observations of the Perseid meteor shower and illustrates normal activity. The observations were made by members of the International Meteor Organization from the 1990s to the 2010s (with periods of enhanced activity left out). The solar longitude basically represents 60 days, illustrating the long duration of the shower and the strong peak

Analysis

From the 1860s onward, studies of the Perseids began to include more than just hourly rates and radiant positions. Numerous observers began to plot the paths of 198 9 August Meteor Showers

Table 9.1 Perseid radiant ephemeris Date RA (°) Dec (°) July 27 27.1 +53.2 July 29 29.3 +53.8 July 31 31.6 +54.4 Aug. 2 33.9 +55.0 Aug. 4 36.4 +55.5 Aug. 6 38.9 +56.0 Aug. 8 41.5 +56.5 Aug. 10 44.3 +56.9 Aug. 12 47.1 +57.3 Aug. 14 50.0 +57.7 Aug. 16 52.9 +58.0

meteors onto star charts to derive the points from which the meteors seemed to be radiating. The most prolifi c observer of this stream was Denning, who, between 1869 and 1898, observed 2,409 Perseids127 and became the fi rst person to derive a daily ephemeris of the radiant’s movement. In 1901, he published his most precise radiant ephemeris128 (Table 9.1 ). In addition to this main radiant near Eta Persei, there have been indications that several secondary showers are also active. Minor activity near the main Perseid radiant has been noted on several occasions up to the present time and may have been noted as long ago as 1879, when Denning pointed out that he had “detected the existence of two other simultaneous showers from Chi and Gamma Persei.”129 This latter shower is one of the most active of the secondary radiants and seems to have been frequently observed during the twentieth century—especially with telescopic aid. The following observations represent some of the details. • In 1921, E. J. Öpik (Tartu, Estonia) observed the Perseids telescopically on August 10 and 12. On the latter date, he noted that nine meteors emanated from an oval area 5.7° × 2.2° across centered at a = 40.0° d = +55.6°. 130 • On 1921 August 11, C. P. Adamson (Wimborne, Dorset, England) detected both the normal radiant and this southern component visually by claiming the Perseids emanated from an elongated area extending from a = 43°, d = +57° to a = 49°, d = +58°.131 • On 1931 August 10, C. B. Ford and B. C. Darling found a telescopic radiant at a = 40.9°, d = +54.4°.132 • On 1932 August 8, Öpik observed a radiant at a = 39°, d = +54°.133 • During 1934 August 12–13, Ford found a telescopic radiant at a = 43.1°, d = +55.2°. 134 One of the more recent examples of the complexity of the Perseid meteor shower was revealed in three studies of the radiant conducted from 1969 to 1971, by observers in the Crimea. In addition to the main radiant near Eta Persei, they confi rmed the existence of the major radiants near Chi and Gamma Persei, as well as minor radiants near Alpha and Beta Persei. These meteor showers are generally short-lived and Perseids 199 possess radiants that move nearly parallel to the main radiant. The following are summaries of the most consistent of the secondary Perseid radiants.135, 136 • The Gamma Perseids mainly occur from August 11 to 16 from an average radiant at a = 41°, d = +55°. The radiant diameter averages about 2°. Rates rise and decline with those of main radiant. • The Chi Perseids occur from August 7 to 16 from an average radiant at a = 35°, d = +56°. The radiant diameter is about 2°. Maximum seems to occur between the 9th and 11th. • The Alpha Perseids occur from August 7 to 24 from an average radiant at a = 51°, d = +50°. The radiant diameter averages about 1.5°. Maximum seems to occur somewhere between the 12th and 17th. • The Beta Perseids occur from August 12 to 18 from an average radiant at a = 47°, d = +40°. The radiant diameter averages about 1°. Rates are irregular. This is the weakest branch of the Perseid cluster. These secondary centers of activity have been predominantly visual displays; however, time was taken to seek out some of these other radiants during the Jodrell Bank radio-echo survey of the 1950s. Only the Alpha Perseids were noted with con fi dence. Detected in both 1951 and 1953, the radiant was very diffuse and 8° in diameter centered at a = 54°, d = +48°. It was detected between August 8 and 11, and the highest radio-echo rate reached 37 per hour (the main Perseid radiant reached radio-echo rates of 50 per hour during the same years).137 Other studies conducted by amateur and professional astronomers during the last few decades have concentrated on speci fi c details of shower members. One especially interesting topic is the variation in meteor brightness (an indication of size) as activity progresses. A. Hruska (1954) said that in 1954 the average magnitude was about 2.5 from August 8 to 12, 2.8 on August 12/13, and 3.4 by August 14/15. 138 In the analysis of the 1956 display, Z. Ceplecha (1958) showed a similar, though less pronounced decline in brightness. From August 4 to 10, the average Perseid was near magnitude 2.68, while from August 10 to 15 it was 2.94. The extremes came on August 6/7 (magnitude 2.31) and August 13/14 (magnitude 3.18).139 Just as Hruska and Ceplecha’s studies show confl icting patterns representing the decline in the Perseid magnitude distribution in August, two later studies seem to support both views. In 1983, members of the Spanish astronomical group Agrupacion Astronomica Albireo, under the direction of E. M. Moya, obtained an excellent series of Perseid magnitude observations, which seemed to support Hruska’s study. Between 1983 August 1 and 13, the average daily magnitude varied from 1.75 to 2.04. Thereafter, it dropped to 2.19 by the 14th, 2.52 by the 15th, 2.77 by the 17th, 2.92 by the 19th and 3.45 by the 20th. Another excellent series of magnitude estimates were made by Roggemans from 1986 July 27-August 16. Observing in darker skies than the Spanish group, Roggemans detected 1,315 Perseids and gave the average magnitude of the shower as 3.10. 140 Roggemans’ estimates were very consistent throughout the shower’s duration with variations being typically less than 10 % on any given day; however, there were two exceptions. The fi rst came on August 5/6 and 6/7, when the average magnitude 200 9 August Meteor Showers dropped to a low of 3.54. The second drop occurred on August 9/10 and 10/11 when the average magnitude reached 3.71. This set of observations seems to support Ceplecha’s study. Ultimately, these magnitude studies (and many more not discussed here) point to an irregular mass distribution within the Perseid stream. It most likely involves the fi lamentary structure and perhaps even the Poynting-Robertson effect. Another statistic examined during the last few decades has been the percentage of Perseids that leave persistent trains. This is a major factor long noted in the separation of Perseids from other active showers occurring during the fi rst half of August. M. Plavec used the records made at the Skalnate Pleso Observatory (Slovakia) to produce one of the most ambitious studies of train phenomena to date. He studied 8028 meteors observed between 1933 and 1947, and found the following percent- ages: 45 % possessed trains in 1933, 60 % in 1936, 35 % in 1945, and 53.5 % in 1947. The variations could not be correlated to sunspot numbers.141 It is likely that the variations are another indication of the fi lamentary structure. With respect to the double peak that was noted by Roggemans and others in the late 1980s and early 1990s, Brown and Rendtel (1996) examined this. Their analysis of the fl ux pro fi le of the Perseids from 1988 to 1994 revealed there were three actual peaks: “a long-lived and relatively weak background component, a core component which is active for 1–2 days near the main peak of the shower, and an outburst component which is active for only a few hours.” The authors said the background component “is long-lived and shows weak activity extending from late July [l = ~115°] until the end of August [l = ~150°]. This portion of the Perseid stream shows a very gradual increase in activity until [l = ~138°], at which time the activity steepens as the core portion of the stream is encountered.” The core component is very symmetrical as it ascends to and descends from maximum, with the peak always occurring at l = 139.96° ± 0.05°. They added that the outburst component “changes position and strength dramatically from year to year…”.142

Evolution of the Stream

R. B. Southworth (1963) used the accurate observations acquired during the photographic Harvard Meteor Program and the IBM 704 and IBM 7090 computers at the Smithsonian Observatory to examine the dynamical evolution of the Perseids. He determined the observed variances of the radiant position, geocentric velocity, and the dates the photographic meteors appeared. Although he noted that the orbit of the Perseids passes 1.3 AU from Jupiter’s orbit and 0.3 AU from Saturn’s orbit, he said perturbations from these planets “cannot explain the present Perseid distribution.” From the variances, he deduced ages which indicated the Perseid stream was 2,600–27,000 years old. Southworth added, “Since other processes can scatter the Perseids 201 meteors, but can hardly bring them back together, the ages … are upper limits.” Southworth concluded that the average age of the Perseids “does not exceed 3,000 years, and that the overall age is not likely to exceed 6,000 years.”143 D. W. Hughes and B. Emerson (1982) studied the stability of the Perseid meteor stream node using observations from ancient and medieval times, as well as the present time. They said that during the years 36–1980, the node moved at a rate of 0.00038° per year or about 1 day every 70.59 years.144 In 1995, N. W. Harris, K. K. C. Yau, and Hughes published a paper that studied the long-term evolution of comet Swift-Tuttle and the Perseids. They integrated the orbit of comet Swift-Tuttle backwards for 270,000 years in order to understand the evolution of the Perseid stream. It was found that the comet was then moving in an orbit with a perihelion distance of about 1.5 AU, so that Earth did not encounter the meteor stream. The authors said that by 160,000 years ago planetary perturbations had reduced the perihelion distance to less than 1.2 AU and it was then that “the decay of this comet led to the production of any Perseid meteoroids that can be observed from Earth.” They added, “… the Earth only samples the ‘inner edge’ of the Perseid stream and … the core of the descending nodal distribution of the actual Perseids extends out to heliocentric distances of at least 1.2a.u”.145 The orbital evolution was modeled by J. Jones and Brown (1996) using 1.5 million theoretical particles released during the 1610, 1737, and 1862 apparitions of comet Swift-Tuttle. They found that the recently released particles would not be crossing the orbit of Earth if it were not for planetary perturbations. They discovered that the increased rates observed from 1991 to 1994 were a result of ejecta released during the comet’s 1862 apparition, while the weaker activity noted from 1987 to 1989 was a result of ejecta released during the 1737 apparition.146 The Jones and Brown model above included another statement and a prediction. They wrote, “A periodicity of approximately 12 years in Perseid activity is noted in the material ejected during the 1862 apparition.” They predicted that Perseid activity would subsequently increase again “starting in 2003 and lasting through 2010.” Such a prediction for enhanced activity was also announced by E. Lyytinen and T. van Flandern (2004). They applied their model that had been very successful in predicting the Leonid meteor outbursts of 1999–2003 and found “that particles ejected in 1862 about 78 days before perihelion at a distance of about 1.7 AU will cross the ecliptic very close to the Earth’s orbit in August 2004.” They said the outburst would involve “fainter-than-average meteors” with the peak occurring on August 11.87, which would favor Asia. 147 Analysis revealed the outburst reached a peak ZHR of 187 on August 11.87. 202 9 August Meteor Showers

Orbits

The orbits labeled “139” and “144” are from Schiaparelli (1871). The orbit labeled “1937–1963” represents an average of 102 photographic meteor orbits detected during these years. The orbit labeled “1960” is from B. L. Kashcheyev and V. N. Lebedinets (1967). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2002–2006” is from Brown et al. (2008). The orbit labeled “2002– 2008” is from Brown et al. (2010). The orbit labeled “109P” is that of the periodic comet 109P/Swift Tuttle.

w W (2000) i q e a 139 155 140 114 0.953 1.0 ∞ 144 152 142 118 0.941 1.0 ∞ 1937–1963 149.2 140.2 113.2 0.942 0.902 9.64 1960 150.9 137.2 113.1 0.95 0.91 11.11 1968–1969 152.5 140.4 110.2 0.960 0.881 8.040 2002–2006 152.7 139.8 115.0 0.957 0.984 61.2 2002–2008 153.12 140.0 115.6 0.9560 1.096 −9.91 109P 152.98 139.38 113.45 0.9595 0.9632 26.09

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21. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 22. R. E. McCrosky and A. Posen, Smithsonian Contributions to Astrophysics, 4 (1961), pp. 15–84. 23. L. G. Jacchia and F. L. Whipple, Smithsonian Contributions to Astrophysics, 4 (1961), pp. 97–129. 24. R. B. Southworth and G. S. Hawkins, Smithsonian Contributions to Astrophysics , 7 (1963), pp. 261–85. 25. N. de Konkoly, Monthly Notices of the Royal Astronomical Society , 40 (1880 Apr.), p. 361. 26. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 278. 27. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 222. 28. W. F. Denning, The Observatory , 43 (1920 Jul.), p. 263. 29. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), p. 716. 30. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 80. 31. Z. Sekanina, Icarus , 27 (1976), pp. 282, 296. 32. Meteor News , No. 3 (1970 Oct.), p. 3. 33. M. Buhagiar, Western Australia Meteor Section Bulletin , No. 160 (1981). 34. L. R. Bellot Rubio, WGN, Journal of the International Meteor Organization , 18 (1990 Feb.), pp. 26–8. 35. R. Arlt, R. Koschack, and J. Rendtel, WGN, Journal of the International Meteor Organization , 20 (1992 Jun.), pp. 114, 121–5. 36. J. Zvolánková, Contributions of the Astronomical Observatory Skalnaté Pleso , 23 (1993), pp. 57–62. 37. A. McBeath, WGN, Journal of the International Meteor Organization , 24 (1996 Feb.–Apr.), pp. 68–9. 38. J. Borovicka and M. Weber, WGN, Journal of the International Meteor Organization , 24 (1996 Feb.–Apr.), pp. 30–2. 39. F. W. Wright, L. G. Jacchia, and F. L. Whipple, Astronomical Journal, 61 (1956 Mar.), pp. 61–9. 40. F. W. Wright, L. G. Jacchia, and F. L. Whipple, Astronomical Journal, 61 (1956 Mar.), pp. 61–2. 41. Z. Sekanina, Icarus , 18 (1973), p. 267. 42. Z. Sekanina, Icarus , 27 (1976), p. 307. 43. L. Neslusan, Meteoroids 1998, Editors: W. J. Baggaley and V. Porubcan. Proceedings of the International Conference held at Tatranska Lomnica, Slovakia, 1998 August 17–21. Astronomical Institute of the Slovak Academy of Sciences (1999), pp. 319–22. 44. L. Neslusan, Astronomy and Astrophysics , 351 (1999 Nov.), pp. 752–8. 45. I. Hasegawa, Proceedings of the Meteoroids 2001 Conference, 6 – 10 August 2001, Kiruna, Sweden . Ed.: Barbara Warmbein. ESA SP-495, Noordwijk: ESA Publications Division, ISBN 92-9092-805-0 (2001), pp. 55–62. 46. A. Dubietis and R. Arlt, WGN, Journal of the International Meteor Organization , 32 (2004 Jul.), pp. 72–3, 75. 47. G. L. Tupman and F. Denza, Monthly Notices of the Royal Astronomical Society , 33 (1873 Mar.), p. 302. 48. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 318. 49. N. de Konkoly, Monthly Notices of the Royal Astronomical Society , 40 (1880), p. 356. 50. H. Corder, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), p. 136. 51. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), p 127. 52. W. F. Denning, The Observatory, 16 (1893 Sep.), pp. 317–18. 53. W. F. Denning, The Observatory , 45 (1922 Oct.), pp. 332–3. 54. W. H. Christie, Flower Observatory Reprint , No. 4 (1929), p. 22. 55. W. F. Denning, The Observatory , 49 (1926 Aug.), p. 257. 56. B. S. Whitney, Flower Observatory Reprint , No. 41 (1938), p. 7. 57. R. Widner, Flower Observatory Reprint , No. 99 (1954), p. 261. 58. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 221, 223. 204 9 August Meteor Showers

59. F. L. Whipple, The Astronomical Journal , 59 (1954 Jul.), pp. 202–3, 211. 60. Z. Sekanina, Icarus , 18 (1973), pp. 257, 260. 61. W. F. Denning, Nature , 20 (1979 Sep. 11), p. 458. 62. Meteor News , No. 35 (1977 Mar.), p. 6. 63. Meteoros , 14 (1984 May), p. 31. 64. R. Veltman, Radiant , 7 (1985 Jul.–Aug.), p. 75. 65. M. de Lignie and K. Jobse, WGN, Journal of the International Meteor Organization , 25 (1997 Jun.), pp. 130–5. 66. A. Grishchenyuk, WGN, Journal of the International Meteor Organization , 21 (1993 Dec.), p. 286. 67. C. E. Worley, Flower and Cook Observatory Reprint , No. 131 (1961), p. 7. 68. H. L. Alden, Popular Astronomy , 40 (1932 Dec.), p. 647 69. N1964, pp. 227–9, 233. 70. Z. Sekanina, Icarus , 27 (1976), pp. 283, 297. 71. D. W. Pankenier, Z. Xu, and Y. Jiang, Archaeoastronomy in East Asia , New York: Cambria Press (2008), p. 308. 72. W. Hamilton, Philosophical Transactions of the Royal Society of London , 70 (1780), p. 63. 73. C. Gannett, Memoirs of the American Academy of Arts and Sciences , 1 (1785), p. 327. 74. N. Webster, A Brief History of Epidemic and Pestilential Diseases , volume 2. Hartford: Hudson & Goodwin(1799), p. 89. 75. P. van Musschenbroeck and J. Lulofs, Introductio ad Philosophiam Naturalem . Volume 2. Leiden: S. and J. Luchtmans (1762), p. 1061. 76. S. F. C., National Gazette (1792 Aug. 15), p. 330. 77. J. Farey, The Philosophical Magazine and Journal , 57 (1821 May), pp. 346–51 78. J. Graziani, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 5 (1837 Aug.), p. 348. 79. T. F. Furley, The Pocket Encyclopaedia of Natural Phenomena (1827), p. 17. 80. T. F. Furley, The Pocket Encyclopaedia of Natural Phenomena (1827), pp. 40–1. 81. L. A. J. Quetelet, Correspondance Mathématique et Physique de l’Observatoire de Bruxelles (1837), pp. 436–9. 82. D. W. R. McKinley, Meteor Science and Engineering . New York: McGraw-Hill Book Company, Inc. (1961), p. 6. 83. S. L. Andrews, Annual Report of The Board of Regents of the Smithsonian Institution . Washington: Government Printing Ofﬁ ce (1867), p. 405. 84. Walferdin, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 5 (1837 Aug.), p. 348. 85. L. A. J. Quetelet, H. W. Brandes, E. F. F. Chladni, and D. Sauveur, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 3 (1836), pp. 410, 412–13. 86. L. A. J. Quetelet, Annuaire de l’Observatoire Royal de Bruxelles pour l’an 1837 , 4 (1836), p. 272. 87. L. A. J. Quetelet and E. Mailly, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 4 (1838), pp. 79–81. 88. F. J. D. Arago, P. A. E. Laugier, and A. Bouvard, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 5 (1837 Aug.), p. 183. 89. G. C. Schaeffer, American Journal of Science and Arts , 33 (1838 Jan.), pp. 133–4. 90. E. C. Herrick, American Journal of Science and Arts , 33 (1838 Jan.), p. 176. 91. E. C. Herrick, American Journal of Science and Arts , 33 (1838 Jan.), p. 177. 92. E. C. Herrick, American Journal of Science and Arts , 37 (1839 Jul.–Oct.), pp. 326–7, 333. 93. A. von Humboldt, Cosmos: A Sketch of a Physical Description of the Universe , volume 4. Translated by E. C. Otté and B. H. Paul. London: George Bell & Sons (1852), p. 578 94. A. Colla, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles , 8 pt. 2 (1841), p. 220. 95. J. Locke, American Journal of Science and Arts , 41 (1841 Jul.–Sep.), p. 400. Perseids 205

96. A. S. Herschel, Notices of the Proceedings at the Meetings of the Members of the Royal Institution of Great Britain , 4 (1866), p. 92. 97. A. Secchi, Wochenschrift fur Astronomie, Meteorologie, und Geographie, (1862 Jul. 2), pp. 209–12. 98. R. A. Coulvier-Gravier, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 53 (1861 Aug. 19), pp. 349–50. 99. B. V. Marsh and S. J. Gummere, American Journal of Science and Arts (2nd series) , 32 (1861 Sep.), pp. 294–5. 100. R. A. Coulvier-Gravier, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 55 (1862 Aug. 18), pp. 336–8. 101. E. Heis, Wochenschrift für Astronomie, Meteorologie, und Geographie , 17 (1863), pp. 363–6; 102. E. Heis, Report of the Annual Meeting of the British Association for the Advancement of Science , 33 (1864), p. 331. 103. W. F. Denning, Nature , 20 (1879 Sep. 11), p. 457. 104. G. W. Kronk, Cometography , volume 2. United Kingdom: Cambridge University Press (2003), pp. 307–13. 105. G. V. Schiaparelli, Bullettino Meteorologico dell’Osservatorio del Collegio Romano , 5 (1866 Nov.), pp. 127–33. 106. W. F. Denning, The Observatory , 35 (1912 Sep.), pp. 337–8. 107. E. F. Sawyer, Astronomical Journal , 29 (1915 Oct. 13), p. 64. 108. W. F. Denning, The Observatory , 43 (1920 Oct.), p. 369. 109. C. P. Olivier, Popular Astronomy , 39 (1931 Oct.), pp. 491–6; 110. C. P. Olivier, Popular Astronomy , 39 (1931 Nov.), pp. 546–51. 111. C. P. Olivier, Popular Astronomy , 53 (1945 Dec.), pp. 509–11. 112. P. M. Millman, Journal of the Royal Astronomical Society of Canada, 50 (1956 Feb.), pp. 30–1. 113. B. G. Marsden, The Astronomical Journal , 78 (1973 Sep.), pp. 654–62. 114. P. Roggemans, Werkgroepnieuws , 13 (1985 Feb.), pp. 8–13. 115. D. di Cicco, Sky & Telescope , 70 (1985 Nov.), pp. 504–5. 116. D. di Cicco, Sky & Telescope , 72 (1986 Nov.), p. 546. 117. P. Roggemans, WGN, Journal of the International Meteor Organization , 17 (1989 Aug.), pp. 127–37. 118. R. Koschack and P. Roggemans, WGN, Journal of the International Meteor Organization , 19 (1991 Jun.), pp. 87–98. 119. Y. Taguchi, P. Aneca, B. de Pontieu, J. Deweerdt, and J. van Wassenhove, International Astronomical Union Circular , No. 5330 (1991 Aug. 28). 120. A. Mizer, P. Jenniskens, J. Rao, International Astronomical Union Circular, No. 5586 (1992 Aug. 13). 121. R. Koschack, R. Arlt, and J. Rendtel, WGN, Journal of the International Meteor Organization , 21 (1993 Aug.), pp. 152–67. 122. B. G. Marsden, International Astronomical Union Circular , No. 5620 (1992 Sep. 27). 123. B. G. Marsden, International Astronomical Union Circular , No. 5839 (1993 Aug. 5). 124. P. G. Brown, WGN, Journal of the International Meteor Organization, 21 (1993 Aug.), p. 218. 125. J. Rendtel, WGN, Journal of the International Meteor Organization, 21 (1993 Oct.), pp. 235–9. 126. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 331. 127. W. F. Denning, Memoirs of Royal Astronomical Society , 53 (1899), p. 210. 128. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 62 (1901), p. 169. 129. W. F. Denning, Nature , 20 (1879 Sep. 11), p. 458. 130. E. J. Öpik, Astronomische Nachrichten , 217 (1922), p. 41. 131. C. P. Adamson, Nature , 107 (1921 Aug. 18), p. 793. 132. C. P. Olivier, Popular Astronomy , 39 (1931 Nov.), p. 547. 206 9 August MeteorShowers

133. E. J. Öpik, Harvard College Observatory Circular , No. 388 (1934), p. 36. 134. C. P. Olivier, Popular Astronomy , 42 (1934 Oct.), p. 469. 135. V. V. Martynenko, and N. V. Smirnov, Solar System Research , 7 (1973), pp. 104–9. 136. V. V. Martynenko, L. Y. Vagner, and A. S. Levina, Solar System Research , 7 (1973), pp. 163–5. 137. K. Bullough, Jodrell Bank Annals , 1 (1954 Jun.), pp. 80–5. 138. A. Hruska, Bulletin of the Astronomical Institutes of Czechoslovakia , 5 (1954), p. 14. 139. Z. Ceplecha, Bulletin of the Astronomical Institutes of Czechoslovakia , 9 (1958), p. 236. 140. P. Roggemans, Personal Communication (1986 Sep. 24). 141. Sky and Telescope , 12 (1953 Jan.), pp. 74–5. 142. P. G. Brown and J. Rendtel, Icarus , 124 (1996 Dec.), pp. 414–428. 143. R. B. Southworth, Smithsonian Contributions to Astrophysics , 7 (1963), pp. 299–303. 144. D. W. Hughes and B. Emerson, The Observatory , 102 (1982 Apr.), pp. 39–42. 145. N. W. Harris, K. K. C. Yau, and D. W. Hughes, Monthly Notices of the Royal Astronomical Society , 273 (1995 Apr.), pp. 999–1015. 146. J. Jones and P. G. Brown, Physics, Chemistry, and Dynamics of Interplanetary Dust . Astronomical Society of the Paciﬁ c Conference Series, Volume 104. Edited by Bo A. S. Gustafson and Martha S. Hanner (1996), pp. 105–8. 147. E. Lyytinen and T. van Flandern, WGN, Journal of the International Meteor Organization , 32 (2004 May), pp. 51–3. Chapter 10

September Meteor Showers

Gamma Aquariids

This meteor shower was fi rst observed in England during 1921, when A. G. Cook and J. P. M. Prentice independently detected activity in early September. The former observer plotted fi ve meteors from a = 334.5°, d = −2° during September 1, 3, and 8, while Prentice plotted four meteors from a = 335°, d = −2° during September 6–8.1 During 1923 September 7–8, Prentice reobserved the shower and managed to plot fi ve meteors from a radiant of a = 334°, d = −3°.2 No further observations of this meteor shower were reported until 1935, when R. A. McIntosh’s paper “An Index to Southern Meteor Showers” was published in the Monthly Notices of the Royal Astronomical Society . Among his list of 320 radiants, which were mostly determined using observations made by the New Zealand Astronomical Society, was a radiant at a = 335°, d = −2°, which was active during September 1–14.3 The meteor shower was also included among the 5406 visual radiants listed in C. Hoffmeister’s 1948 book Meteorströme . Despite the observations covering the period of 1908–1938, Gamma Aquariid radiants were only detected during 1929, 1932, and 1934. The 1929 radiant was detected on September 8 from a = 333°, d = +5°. The 1932 radiant was detected on September 5 from a = 333°, d = −10°, and the 1934 radiant was detected on September 4 from a = 330°, d = −11°. 4 Although the German observations of 1932 September 5 and 1934 September 4 appear to be slightly further south than indicated by the earlier English observations, calculations reveal the Gamma Aquariid radiant to possess a northeasterly

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 207 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_10, © Springer Science+Business Media New York 2014 208 10 September Meteor Showers motion, thus, it must be expected that the radiant of September 4–5 would be southwest of the September 8 position. A possible confi rmation of the early position of this radiant might be present in a 1964 paper by C. P. Olivier entitled “Catalogue of Fireball Radiants,” in which a radiant with a mean date of September 5 was given an average position of a = 333°, d = −8°. Based on fi ve observed fi reballs, the indicated duration extended for 3 days before and after the mean date.5 Only one radio-echo survey has ever revealed Gamma Aquariid activity. During the 1961–1965 session of the Radio Meteor Project, activity was noted during September 10–11. Z. Sekanina (1976) gave the date of the nodal passage as September 10.8 (l = 167.7°), at which time the radiant was at a = 335.6°, d = −1.7°. The geocentric velocity was determined as 18.1 km/s.6 The stream’s absence from other radio-echo surveys can usually be explained as due to the equipment not being in operation during early September; however, the second session of the Radio Meteor Project did not reveal this radiant, despite its being in operation during 1969 September 9–12. Sekanina describes this session as being more sensitive than that of 1961–1965, yet absolutely no evidence of activity was found during a search through the raw data. Thus, the possibility may exist that this stream produces a periodic display rather than an annual one. Although this stream was not noted in any of the analyses of photographic meteor orbits during the 1950s, 1960s and 1970s, two photographic meteors were identifi ed from a list of 2,529 orbits computed by R. E. McCrosky and A. Posen that appear to defi nitely belong to the Gamma Aquariid stream. They were both detected on 1952 September 11 during the Harvard Meteor Project and indicate a radiant of a = 335°, d = −3°. The magnitudes of the meteors were given as −0.4 and +1.6, while their beginning heights were 98.7 and 87.0 km, respectively.7 During the 1970s two positive detections of this stream came from observers in the Southern Hemisphere. The meteor section of the Royal Astronomical Society of New Zealand succeeded in observing this shower on several occasions during the decade. Section director J. E. Morgan compiled a list of 213 active radiants, which included the Gamma Aquariids. Meteor rates of four per hour were noted on September 10, from a = 335°, d = −3°. During 1980, the Western Australia Meteor Section observed meteors from this shower during September 10–13. A maximum ZHR of about one was observed on September 10 from a = 335°, d = −3°. 8 The International Meteor Organization’s Video Meteor Network created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. There are indications that the Gamma Aquariids are present within this sample, although they are at a more southerly declination, close to the radiants determined by Hoffmeister and Olivier above. Under l = 166°, a radiant at a = 337.5°, d = −12.5° was delineated by 101 meteors. Under l = 167°, a radiant at a = 337.9°, d = −12.0° was delineated by 120 meteors. Under l = 168°, a radiant at a = 335.6°, d = −9.5° was delineated by 92 meteors. The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1952” is an average of the two orbits found in McCrosky and Posen (1961). Alpha Aurigids 209

w W (2000) i q e a 1961–1965 250.6 168.4 4.4 0.725 0.718 2.57 1952 248.0 168.7 3.5 0.775 0.685 2.46

Alpha Aurigids

Duration : August 28–September 5 (l –155–163°) Maximum : September 1 (l = 158.6°) Radiant : a = 90°, d = +40° ZHR: 6

Radiant Drift : a = UNK, d = UNK V G : UNK km/s

The Alpha Aurigids were independently discovered by observers in Germany and the Czech Republic on the night of 1935 August 31/September 1. C. Hoffmeister and A. Teichgraeber (Sonneberg, Germany) began their observations around 9:00 p.m. and continued observations for about 6 h. Teichgraeber noted a defi nite increase in the number of meteors during 1:43–2:43 a.m. and even higher numbers during 2:43–3:43 a.m. Hoffmeister’s analysis of his own observations revealed that 1–2 meteors from the Auriga region were seen during the fi rst 4 h of his session, while four were seen during 12:45–1:45 a.m. Interestingly, he reported no meteor from the Auriga region during 1:45–2:45 a.m., which would have been coincident with Teichgraeber’s initial recognition of increased activity. Hoffmeister did report 15 meteors from the Auriga region during 2:45–3:45 a.m. “Hoffmeister determined the radiant as a = 85°, d = +40.5°, but added that “perhaps at the same time there was a radiant point at a = 85°, d = +59°.” 9 A short time after the German observers began their meteor watch, three members of the meteor section of the Czech Astronomical Society began observations of their own. A. Vratnik, J. Vlcek, and J. Stepanek were observing from Stefanik Observatory (Prague, Czech Republic). All three observers watched the sky from 9:31 to 10:45 p.m. and reported low hourly rates of 4–7. At this point, all three observers stopped observing for over an hour. Vratnik resumed observations from 11:42 p.m. to 12:03 a.m. and spotted one meteor. After another break, Vratnik resumed observations at 1:54 a.m. and during the next 2 h and 18 min he spotted 33 meteors, of which 23 were coming from the Auriga region. Ten meteors came from this region between 3:50 and 4:00 a.m. The radiant was determined as a = 87°, d = +40.5°. The average magnitude was 2.62, while 74 % of the meteors brighter than magnitude 3.5 left trains. V. Guth immediately noted the similarity between this radiant and the predicted radiant of a = 90.2°, d = +39.3° for comet C/1911 N1 (Kiess).10 In his 1948 book, Meteorströme, Hoffmeister noted that the link with comet Kiess made the circumstances of the 1935 observations curious. He pointed out that the comet’s orbit was nearly parabolic, making the shower’s sudden appearance 24 years after its perihelion passage dif fi cult to explain. Hoffmeister examined his own annual observations made near the end of August and in early September, and noted 210 10 September Meteor Showers probable detections of this shower in 1911, 1929, and 1930. In the former year, 5 of the 55 meteors he had plotted on September 2 (l = 159.2°) converged at a = 84°, d = +43°. During 1929, he found radiants of a = 85°, d = +38° on September 1 (l = 158.1°), a = 87°, d = +38° on September 3 (l = 159.8°), and a = 89°, d = +39° on September 4 (l = 161.0°). In 1930, one radiant was found at a = 82°, d = +38° on August 31 (l = 156.4°). Hoffmeister concluded that, although activity seems to have been present since the comet’s perihelion passage, there is no evidence that the Alpha Aurigids are a permanent shower. He added that the strong 1935 shower was probably due to an isolated meteor group in the comet’s orbit.11 Hoffmeister’s conclusion seemed well founded, as additional observations failed to appear in the records of American, European, or Russian observers during the four decades following 1935; however, observations have been made since the 1970s. During 1979 and 1980, members of the Western Australia Meteor Section (WAMS) succeeded in observing the Alpha Aurigids. In the former year, observations were made over the period of August 25–September 2. Maximum activity came on September 2, when the ZHR reached 8–9 from a radiant of a = 87°, d = +42°. In 1980, observations were made during August 31–September 6. Maximum came on the 6th, when the ZHR reached about 9, from a = 82°, d = +38°. 8 Another detection of this shower came on 1986 September 1, when I. Tepliczky (Tata, Hungary) noticed another outburst. He observed from 00:00 to 01:00 UT and saw very little activity. Although he was going to stop observing at that time, he wrote that a little after 01:00 UT, “I was an eyewitness of a very spectacular phenomenon. Very bright, yellow meteors began to appear, all of them leaving persist- ing trains.” As it turned out, a meteor he saw at 00:47 was the earliest member of this shower. He said that during 01:30–02:00 UT, “a meteor was seen every one or two minutes.” The display began to dwindle thereafter and the fi nal member of this display was seen at 02:11 UT. He determined the radiant position as a = 94°, d = +36.4°. He said the ZHR reached 39.6 ± 8.1. The meteors ranged in brightness from magnitude −4 to +4, with an average of +0.54.12 J. Rendtel (1990) analyzed a decade of observations provided by observers with the group Arbeitskreis Meteore (AKM) of Germany. He said it is apparent that an annual minor shower is present. Maximum occurs on August 31/September 1 ( l = 157.8° ± 0.4°), with a maximum ZHR of 10.13 This meteor stream produced another outburst in 1994. G. Zay and R. Lunsford (Descanso, California, USA) spent a total of fi ve nights observing Alpha Aurigid activity. Lunsford observed on the nights of August 29/30 and August 30/31 and noted two Alpha Aurigids each night in just over 3 h of observations. Both observers spent 8.39 h watching for these meteors on the night of August 31/September 1, with Lunsford seeing 17 Alpha Aurigids and Zay seeing 20. They said the peak de fi nitely came during 07:22–08:22 UT, when Lunsford saw 11 and Zay saw 13 Alpha Aurigids, at which time the radiant was only 13 above the horizon. As a result, the trajectories of all the Alpha Aurigids during the peak “were quite long.” The ZHR was determined as 37 for Lunsford and 55 for Zay.14 In the course of updating this book, an interesting account was located that appeared in the Report of the Forty-Third Meeting of the British Association for the Daytime Zeta Cancrids 211

Advancement of Science (1874). J. E. Clark (Street, Somersetshire, England) saw “quite an abundance of bright meteors” on the night of 1873 September 1. He wrote, “Nine meteors, some of them very fi ne ones, were seen between 11 h and 12 h p.m., mostly in the south; but the directions of their apparent paths were not noted with suffi cient accuracy to determine the place of their radiant-point, or if all the meteors of the display diverged very de fi nitely from a common centre.”15 There is no other indication that this observation represents the Alpha Aurigids, other than its occurrence on September 1. The orbit labeled “Visual” was calculated using the six visual radiants reported in Hoffmeister’s Meteorströme and the two radiants given by the WAMS. The orbit labeled “C/1911 N1” is the orbit of comet C/1911 N1 (Kiess).

w W (2000) i q e a Visual 126.7 159.4 149.0 0.807 1.0 ∞ C/1911 N1 110.37 158.67 148.42 0.684 0.996 184.07

Daytime Zeta Cancrids

The ﬁ rst detection of this daylight shower is attributed to C. S. Nilsson (1964). He analyzed the data acquired during 1961 by the radio equipment at the University of Adelaide (South Australia, Australia). One of the meteor showers was designated “61.8.5” and was detected during August 17–22. Its nodal crossing was given as August 18 ( l = 146.2°), at which time the radiant was at a = 119.7°, d = +19.0°. The geocentric velocity was determined as 43.8 km/s. The facility was not in operation during August 25 to September 21.16 Analyzing data collected by the Canadian Meteor Orbit Radar (CMOR) during 2002–2008, P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 949 meteor orbits from this stream. They noted a duration of August 12–September 10 (l = 140–167°) and said the shower peaked on September 3 (l = 160°) when the radiant was at a = 136.1°, d = +11.7°. The radiant’s daily motion was determined as +0.92° in a and −0.18° in d , while the geocentric velocity was 42.1 km/s.17 The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 1961 206.5 326.9 21.1 0.05 0.99 5 2002–2008 212.57 340.0 16.6 0.0883 0.981 4.64 212 10 September Meteor Showers

Eta Draconids

This meteor stream was detected during both sessions of the Radio Meteor Project during the 1960s. Z. Sekanina (1973) analyzed the data from the 1961 to 1965 session and noted activity during the period of August 28–September 23. The nodal passage came on September 12.1 (l = 168.9°), at which time the radiant was at a = 248.8°, d = +63.4°. The geocentric velocity was determined as 20.3 km/s.6 Sekanina analyzed the data from the 1968 to 1969 session and noted activity during the period of September 9–12. The nodal passage was determined to have occurred on September 12.2 (l = 169.0°), from a = 246.3°, d = +63.8°. The geocentric velocity was given as 19.2 km/s.18 No trace of this meteor shower seems to exist among the numerous radiant lists published since the mid-nineteenth century. The stream has also not been detected by the Canadian Meteor Orbit Radar system which has operated since 2002. The International Meteor Organization (IMO) has a website containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 to 2012. Although there is no radiant at the location on the month and days mentioned above, there are some radiants within 15°. Since low velocity meteor streams sometimes produce a larger diameter radiant, some of the more interesting IMO radiants are discussed here. On September 13 ( l = 170.0°), 117 meteors came from a radiant at a = 251.2°, d = +77.0°. Two radiants were detected on September 14 (l = 171.0°): one at a = 245.6°, d = +75.5° (based on 96 meteors) and the other at a = 238.7°, d = +58.0° (based on 72 meteors). On September 15 (l = 172.0°), 80 meteors came from a radiant at a = 267.2°, d = +61.5°. 19 The orbit labeled “1961–1965” is from Sekanina (1973), while the orbit labeled “1968–1969” is from Sekanina (1976).

w W (2000) i q e a 1961–1965 167.9 169.6 33.3 0.996 0.526 2.10 1968–1969 165.7 169.7 31.9 0.993 0.465 1.86

Daytime Kappa Leonids

B. L. Kashcheyev and V. N. Lebedinets (1967) conducted a radar study during 1960 using equipment at the Kharkov Polytechnical Institute (Ukraine). The analysis revealed 21 meteors detected during daylight during September 21–29. The nodal passage came on September 22 (l = 180°), with the average radiant being a = 162°, d = +16°.20 P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) identi ﬁ ed 1366 meteors from this stream in the data acquired by the Canadian Meteor Orbit Radar September Perseids 213 during 2002–2008. The duration was given as September 6–October 13 (l = 164– 200°). Maximum activity came on September 26 ( l = 183°) from a radiant at a = 162.3°, d = +14.9°. The geocentric velocity was determined as 43.3 km/s. They also gave the daily motion of the radiant as +0.62° in a and −0.3°.17 The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a

1960 39 1 26 0.11 1.000 48.0 2002–2008 33.84 183.0 24.1 0.0911 0.987 6.79

September Perseids

Duration : September 5–September 17 Peak : September 6–9 (l = 165°–167°) @ a = 63°, d = +36°

Radiant Drift : a = UNK, d = UNK V G : 64 km/s

The discovery of this meteor stream has to be credited to W. F. Denning, because of an article published in an 1882 edition of The Observatory titled “The September Perseids.” He fi rst described a “ fi ne meteor” with a long, swift path that was seen on 1874 September 6 and estimated that the radiant was probably near the star e Persei. Although no meteors were seen during the next 2 years, Denning saw 238 meteors during the fi rst half of 1877 September that indicated a radiant at a = 61°, d = +36°. He described these meteors as “swift and much brighter than average; they nearly all left streaks and were chie fl y noted during a series of morning watches between the 4th and 16th.” Denning saw impressive fi reballs again on 1878 September 8 and 1879 September 9, both of which left impressive trains, and then saw “striking activity” on 1880 September 6. With respect to the 1880 activity, Denning wrote, “The meteors were unusually bright and very swift, but their paths were registered with great accuracy in most cases from the streaks left.”21 Denning pointed to a still older account of this radiant which he had published in 1878. Observations by the Italian Meteoric Association during 1872 August 24–September 14 had led to the plotting of ten meteors from a radiant at a = 67°, d = +35°.22 In an article on September radiants published in 1880, Denning noted that Heis noted a radiant at a = 55°, d = +37°, which might be related. He also noted that Zezioli saw meteors from a radiant at a = 60°, d = +32° on 1869 September 6, and Tupman saw meteors from a radiant at a = 66°, d = +40° during 1871 September 7–15. Denning also reiterated that he observed activity from a = 61°, d = +36° during 1877 September 4–16.23 Denning published another paper in 1890 which contained several probable radiants from this stream. He saw seven swift meteors from a = 62°, d = +37° on 214 10 September Meteor Showers

1885 September 3, fi ve swift meteors from a = 60°, d = +35° on 1877–1885 September 4–5, four swift meteors from a = 61°, d = +36° on 1880 September 2 & 6, fi ve swift meteors from a = 60°, d = +38° on 1877 September 7, six swift meteors from a = 62°, d = +36° on 1886 August 28 and September 7, and four swift meteors from a = 62°, d = +37° on 1885 September 8–10.24 Denning continued providing evidence for this stream when he published a paper on fi reball paths and radiants in 1912. He noted that he and J. Herschel saw a fi reball from a = 65°, d = +35° on 1898 September 15 that was slightly fainter than Jupiter, while three people observed a fi reball from a = 62°, d = +34° on 1911 September 18 that was brighter than magnitude 1.25 Despite all of these apparent successes in viewing this meteor stream, Denning published two lists of radiants observed by him in Bristol, England from 1899 to 1911 26 and 1912–192227 and there was no trace of activity from this region. No coordinated searches for this stream occurred during the early to mid- twentieth century; however, radiants from this stream do occasionally appear in the records of the American Meteor Society, as well as in C. Hoffmeister’s Meteorstöme . Hoffmeister noted activity on 1936 September 16 (l = 173.9°) from a radiant at a = 52.9°, d = +40.8° and named it the “September Perseids.” He said 20 meteors were seen from this radiant in 3.7 h. He wrote, “Rather inconspicuous swarm … no doubt a cometary current. But no comet in connection with it could be found.” Interestingly, Hoffmeister also saw another radiant on the same date, from which four meteors indicated a radiant of a = 63°, d = +29°. 28 This radiant is quite close to that reported by Denning during the nineteenth century. No further observations seem to have been made until 1987 and 1988, when members of the Spanish Meteor Society conducted a coordinated search for meteors from this radiant. They observed for several nights spanning 1987 August 31–September 14 and 1988 September 3–20. During the 1987 run, 8 of the 11 nights produced 0–1 meteors for the entire night and the best night was four total meteors on September 1/2. During eight nights of observing in 1988, observers reported 15 meteors were seen in nearly 6 h of observing on both September 7/8 (l = 165°) and September 8/9 (l = 166°). The 41 total meteors registered in 1988 indicated a radiant at a = 60°, d = +37°. J. M. Trigo-Rodríguez (1989) analyzed the results. He pointed out that atmospheric conditions were bad with some interference from moonlight in 1987, while atmospheric conditions were excellent in 1988. This resulted in fainter meteors being seen in the latter year, which apparently accounted for the higher numbers. The population index (r) was given as 2.6. They also estimated that the velocity of these meteors was around 50 km/s. 29 A. K. Terentjeva published a paper titled “Fireball Streams” in 1989 which analyzed the data of 554 fi reballs photographed in the United States and Canada during 1963–1984. One stream, labeled the x Perseids was found active during September 9–17 from a radiant at a = 54°, d = +36°. 30 September Perseids 215

For a while, the September Perseids were included with the Delta Aurigids. The International Meteor Organization (IMO) “Meteor Shower Calendar” for 1992 listed the Delta Aurigids for the fi rst time and gave the duration as September 5–October 10.31 A. Dubietis and R. Arlt (2002) argued that the evidence revealed that the Delta Aurigids were actually two similar but distinct meteor showers. Using the Visual Meteor Database of the IMO, they found 3473 Delta Aurigids were reported during the period of 1991–2001. They divided the data into two periods (1991–1995 and 1996–2001) and conducted two separate analyses. They found that both sets of data indicated two peaks. They concluded that the fi rst peak was the September Perseids and occurred on September 9 ( l = 166.7°) with a ZHR of 3.1. The population index was r = 2.46.32 Arlt and J. Rendtel (2006) suggested that the duration for the September Perseids be established as September 5–17.33 S. Molau and J. Rendtel (2009) presented an analysis of more than 450,000 video meteors that had been recorded by the IMO Video Meteor Network for more than 10 years. They referred to the September Perseids as the “September Epsilon Perseids” and noted that their radiant position of a = 48.0°, d = +39.5° “differs signi fi cantly” from the IMO working list of visual meteor showers, which was a = 60°, d = +47°. 34 Rendtel and Molau (2010) examined meteor activity in the Perseus-Auriga region for the months of September and October using data collected by the IMO Video Meteor Network for over 11 years. For the September Epsilon Perseids, they found 1930 meteors indicating a duration of September 4–21 (l = 162–178°). Maximum came on September 9 (l = 167°) from a radiant at a = 48°, d = +40°. The daily radiant drift was given as +1.1° in a and +0.1° in d .35 The International Meteor Organization (IMO) has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. Stream number 156 is called the “September Epsilon Perseids” and is based on 5029 meteors. The duration is given as September 1–30 (l = 158°–187°), during which time the radiant moves from a = 43.3°, d = +47.0° to a = 66.5°, d = +35.0°. Maximum occurs on September 10 ( l = 167°) from a radiant at a = 48.0°, d = +39.5°. The radiant drift was determined as +1.0° in a and −0.1° in d per day.36 The same database also revealed a weaker component of this stream. It was designated stream number 158 and was also called the “September Epsilon Perseids.” Based on 410 meteors, its duration was given as September 14–19 (l = 171–176°), while maximum occurred on the 19th (l = 176°) from a = 50.4°, d = +25.5°. 37 P. G. Welch (2001) applied a new method of meteor stream search to the double- station photographic meteor database located at the IAU Meteor Data Centre at Lund. 38 Five meteors indicated the following orbit, which was designated “Delta Aurigids;” however, based on the arguments above, this actually represents the September Perseids: 216 10 September Meteor Showers

w W (2000) i q e a Welch 242.8 165.9 138.9 0.74 1.00 ∞

Using the details from the IMO’s stream “156,” the orbit is calculated below. The geocentric velocity is 64 km/s.

w W (2000) i q e a 265.3 167.0 158.7 0.620 0.719 2.21

Piscids: Antihelion

This is the earliest active meteor shower of the huge Taurid Complex. The radiant is quite diffuse and is apparently divided into northern and southern branches. C. Hoffmeister (1948) was the fi rst to offi cially recognize the Piscid stream. Analyzing the observations made by German observers between 1908 and 1938, he identifi ed numerous probable observations of this shower. He concluded that the duration extended from August 16 to October 8, while maximum came on September 12 (l = 169°) from a = 0°, d = +4°. Hoffmeister described the shower as distinct, but weak. He added that two radiants were possibly present—both moving parallel to one another, but one located north of the ecliptic and the other south.39 Although Hoffmeister gave no exact details about his possible northern and southern Piscid showers, a table was given which demonstrated the general motion of the radiant. Note some interesting patterns in this table. First, between August 16 and September 10, the declination changed only slightly, with the average being about +1.2° (based on 49 radiants). On the other hand, the declination for the period September 16–October 8 averaged +8.1° (based on 38 radiants). The number of observed radiants remained fairly consistent during September 1, 8, 12, and 18, which may indicate a fairly fl at maximum, rather than a distinct peak. On September 29, the number of observed radiants reached its highest point. Blending this declination and activity analysis, Hoffmeister’s data points to a southern stream reaching a fl at maximum during the fi rst half of September, while a northern branch is active around September 29. Whether the September 29 peak was due to a maximum of the northern branch or simply a combination of both branches cannot be determined. A search through dozens of radiant lists of the nineteenth and early twentieth centuries reveals only two possible observations—both by W. F. Denning (Bristol, England). The fi rst observation came on 1879 September 14–15, when he plotted seven “very slow” meteors from a = 1°, d = −5°. The next observation involved the plotting of fi ve meteors from a = 4°, d = −2° during 1885 September 3–5.40 Although both radiants were called “Piscids,” neither Denning nor any other astronomer Piscids: Antihelion 217

recognized this as a possible annual shower. Both radiants barely qualify as representing this stream. The addition of photography in the ﬁ eld of meteor studies had begun during the 1890s, but the Harvard Meteor Project of 1952–1954 was the most ambitious program. From this survey came the orbits of over 2500 meteors, which supplied a very large database for future studies of meteor showers. B. A. Lindblad (1971) began a computerized study of these meteor orbits in an attempt to isolate active streams. Lindblad detected two streams which he called the “Piscids”—each receiving a provisional stream number of “31” and “92.” Stream 92 was given a long duration extending from August 31 to November 2. The radiant was given as a = 10°, d = +6°. But while this stream possessed similar characteristics to Hoffmeister’s Piscid stream, the orbit revealed several strong dissimilarities, notably a 20° difference in the argument of perihelion, a 21° difference in the ascending node, and a 0.12 AU difference in the perihelion distance. Stream 31 seemed a more likely candidate, although it did occur 1 month later than Hoffmeister’s stream and possessed a fairly short duration of September 25–October 19. The indicated date of the nodal passage was October 13 (l = 199.1°), at which time the radiant was at a = 26°, d = +14°.41 During 1973, Lindblad, as well as A. F. Cook, B. G. Marsden, R. E. McCrosky, and A. Posen reevaluated several of the streams isolated by Lindblad’s 1971 study. One of the most important discoveries was that over half of the meteors representing stream 92 were actually the Andromedids (see November). The authors concluded that the remaining meteors of stream 92 and the meteors of stream 31 formed the respective southern and northern branches of the Piscids.42 The Piscids were well represented during the two sessions of the Radio Meteor Project conducted by Z. Sekanina during the 1960s. During the 1961–1965 survey, Piscid meteors were detected during August 14–October 4. The date of the nodal passage was calculated as September 10.7 (l = 167.6°), at which time the radiant was at a = 359.8°, d = +3.4°. The link with Hoffmeister’s Piscids was considered very good (D-criterion of 0.110).43 The 1968–1969 session revealed Piscids over the period of August 12–October 7. The nodal passage was said to have occurred on September 16.1 (l = 172.8°), at which time the radiant was at a = 8.5°, d = 6.9°.18 Sekanina’s radio-echo data seem to indicate that a long-duration shower does reach maximum in the Pisces region in early September; however, even though there was no trace of a secondary stream, the orbits obtained during the 1961–1965 study and that of 1968–1969 were somewhat different. These orbital differences, as well as the differences in the dates of nodal passage, may offer supporting evidence that two branches of the Piscid stream do exist, but that their production of very diffuse and weak showers make them dif ﬁ cult to separate when comparing orbital elements. It is probable that only a close monitoring of activity levels will properly separate these two streams. Members of the Western Australia Meteor Section (WAMS) made observations of the Piscids in 1979 and 1980. According to section director J. Wood, observations in 1979 began after the September full moon, when activity from the Delta Piscium region was detected during September 22–23. A maximum ZHR of a little 218 10 September Meteor Showers over one came on September 23 from a radiant at a = 10°, d = +11°. During 1980 September and October, WAMS observed several meteor showers in the Pisces region, but there were three which could be part of this particular shower. The “Piscids” were detected during September 10–12. The maximum ZHR was again slightly more than one, which came on September 11. The radiant was then given as a = 4°, d = +9°. The “Southern Piscids” were detected during September 11–27. At the time of maximum on September 19, a ZHR of about two was emanating from a radiant at a = 4°, d = 0°. The “Northern Piscids” were detected during October 5–16. A maximum ZHR of about three came on October 12 from a radiant at a = 26°, d = +8°.8 P. B. Babadzhanov (1999) announced a possible association of minor planet 1996 SK (now permanently numbered 297273) to the northern and southern branches of the Piscids.44 The orbit labeled “1948” is from Hoffmeister (1948). The stream labeled “1952– 1954” is from Lindblad (1971). The orbit labeled “1952–1958” was calculated using seven photographic meteor orbits. The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “297274” is that of the minor planet originally known as 1996 SK.

w W (2000) i q e a 1948 296 170 3.5 0.40 0.72 1.43 1952–1954 290.8 199.8 3.4 0.399 0.797 2.06 1952–1958 306.6 175.4 6.5 0.271 0.853 1.84 1961–1965 298.5 168.3 3.8 0.344 0.816 1.87 1968–1969 306.3 173.5 3.5 0.311 0.769 1.35 297274 284.21 197.53 1.96 0.5001 0.7945 2.43

Gamma Piscids

The discovery of this stream should be attributed to Z. Sekanina, who established its existence from data gathered during the two sessions of the Radio Meteor Project. The 1961–1965 session revealed only nine de ﬁ nite meteors from the Gamma Piscids during the period of September 10–October 5 (l = 167–192°). The date of the nodal passage was determined as September 24.0 (l = 180.6°), while the average radiant was a = 349.6°, d = +2.9°. 6 The 1968–1969 session picked up 35 members of this stream during August 26–October 22 ( l = 153°– Gamma Piscids 219

209°). The date of the nodal passage was determined as September 22.2 ( l = 178.8°), at which time the radiant was at a = 342.3°, d = +7.7°.18 The orbital elements were given as

w W (2000) i q e a 1961–1965 253.7 181.3 3.9 0.705 0.702 2.366 1968–1969 247.8 179.5 7.6 0.741 0.716 2.606

No trace of activity from this stream was found during the nineteenth century and the ﬁ rst half of the twentieth century among the articles by W. F. Denning, A. King, R. A. McIntosh, C. Hoffmeister, or E. J. Öpik. On the other hand, four photographic meteors were located among the 2529 orbits published by R. E. McCrosky and A. Posen (1961).45 These not only add support to the very existence of this stream, but obviously indicate that visual observations should be possible. The photographic meteors were detected during the Harvard Meteor Project of 1952– 1954 and indicate a duration of September 19–October 2 (l = 176–189°). The apparent date of the nodal passage is September 26 ( l = 183.0°), while the average radiant is a = 351°, d = +10°. The average orbit is

w W (2000) i q e a 255.3 183.7 8.0 0.695 0.723 2.509

A visual detection of this shower was made during the 1970s. A decade-long visual survey of meteors was conducted by M. Buhagiar (Perth, Western Australia, Australia), which involved the plotting of 20,974 meteors and the determination of 488 radiants. The Gamma Piscids were detected on ﬁ ve occasions, revealing a duration of September 21–28 (l = 178–185°). Maximum was said to have generally occurred on September 25 (l = 182°) from a = 350°, d = +5°. The highest hourly rate was typically given as 4.46 The International Meteor Organization (IMO) has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. A search through this database reveals that this shower was detected. On September 22 (l = 179°), 150 meteors were detected from a = 344.1°, d = +5.5°. On September 23 (l = 180°), 153 meteors were detected from a = 352.2°, d = +3.5°. On September 24 (l = 181°), 172 meteors were detected from a = 344.6°, d = +3.5°. On September 25 (l = 182°), 148 meteors were detected from a = 345.2°, d = +2.0°.19 220 10 September Meteor Showers

Daytime Sextantids

Duration : September 17–October 10 (l = 174–197°) Maximum : September 29 (l = 186°) Radiant : a = 154°, d = −1° ZHR : Medium

Radiant Drift : a = +0.56°, d = −0.54° V G : 31 km/s

This daytime meteor shower was discovered during a radio-echo survey using equipment at the University of Adelaide (South Australia, Australia). A. A. Weiss (1960) was analyzing the data acquired during 1956–1958 when he noted a meteor shower that was active from September 26 to October 4. He called it the “Sextantids-Leonids.” The radiant position was not fi rmly established at that time, due to only one aerial being in use, but a theoretical estimate of a = 155° ± 8°, d = 0° ± 10° was made. Weiss noted that the peak activity occurred during September 29 to October 3, when rates were nearly 30 meteor echoes per hour. He added that no trace of activity had been detected during previous radio- echo surveys. 47 This stream was next detected in 1961 during another radio-echo survey at the University of Adelaide. C. S. Nilsson (1964) said the equipment was operated during September 21–29 and that nine meteors were detected during September 24–29. The average radiant was given as a = 151.7°, d = −0.1°. Interestingly, Nilsson noted a similarity between the Sextantid orbit and the orbit of the Geminids of December. He wrote, “statistically, the difference between the Sextantid and Geminid orbits is not signifi cant, and the former could well represent the daytime return of a branch of the latter stream after perihelion passage, if the stream is wide enough.” As Nilsson pointed out, the closest approach of the Sextantids to Earth in December is 0.34 AU, while the indicated width of the Geminid stream is 0.11 AU. Besides the width of both streams, there were other problems as well. Nilsson noted that the Geminids occurred annually with consistent rates “indicating that the meteoric matter is extended uniformly along the orbit.” On the other hand, the Sextantids had only been detected in 1957 and 1961. Surveys in other years should have detected the stream, but since they did not, Nilsson suggested the shower might be periodic. 48 The possible periodic nature of the Sextantids seemed to be confi rmed as the 1960s progressed. B. L. Kashcheyev and V. N. Lebedinets analyzed the data acquired during 1960 by a radar system at the Kharkov Polytechnical Institute (Ukraine), but the Sextantids were not present. Z. Sekanina analyzed the data acquired during the 1961–1965 session of the fi rst Radio Meteor Project (Havana, Illinois, USA), but there was no trace of the Sextantids. The Sextantids were detected during the second session of the Radio Meteor Project, which operated during 1968–1969. Sekanina (1976) said the equipment was not in operation during September 27–October 5, but nine members of this stream were detected during October 7–9. At the time of the nodal passage on Daytime Sextantids 221

October 8.8 (l = 195.8°), the radiant was at a = 156.5°, d = −8.3°, while the geocentric velocity was given as 29.7 km/s.49 Although no major radio survey was conducted during the next few decades, the Sextantids appear to have been detected by amateur astronomers. During 1988, D. Artoos (Belgium) was monitoring the echo rates of meteors during late September, when he noted “high radio meteor activity in the morning of September 28.” He said the hourly rate of the radio meteors jumped from 176 late on September 27.88, to 280 on September 28.37, and then declined to 172 by September 28.88.50 Artoos also noted an increase in activity between 1990 September 24 and October 5, with peak activity occurring on September 27 and 30. He added that N. Kawamura (Japan) also reported higher rates during the period of September 27–30.51 Other amateur astronomers continued to report activity from the Sextantids, using the forward scatter method, throughout the 1990s and 2000s. Within the last two decades, there have been three surveys conducted using radar facilities. D. P. Galligan and W. J. Baggaley (2002) analyzed the data acquired during 1995–1999 by the Advanced Meteoroid Orbit Radar system. They detected 410 meteors, fi nding a peak of activity on September 29 (l = 186.1°) from a radiant at a = 154.5°, d = −1.5°. The geocentric velocity was determined as 31.2 km/s. They also gave the daily motion of the radiant as +0.84° in a and −0.43° in d .52 J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy (2009) analyzed data from 2006 to 2007 that had been acquired by facilities in Davis Station, Antarctica and Darwin, Australia. They identi fi ed activity from the Sextantids during September 26–October 4. At the time of maximum on October 1 ( l = 188.1°), the radiant was located at a = 155.7°, d = −3.9°.53, 54 The most recent observations come from the Canadian Meteor Orbit Radar survey. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) identifi ed 1292 meteors belonging to this stream during the period of September 17–October 10 (l = 174–197°). Maximum activity came on September 29 (l = 186°) from a radiant at a = 154.3°, d = −1°. The geocentric velocity was determined as 31.3 km/s. They also gave the daily motion of the radiant as +0.56° in a and −0.54°.17 A possible parent object was found for this meteor stream in 2005. The Apollo- type minor planet 155140 (2005 UD) was discovered by astronomers at the Catalina Sky Survey on 2005 October 22. 55 Just 3 weeks later, K. Ohtsuka, T. Sekiguchi, D. Kinoshita, and J.-I. Watanabe announced the similarity between the orbits of this object and the Daytime Sextantids, even suggesting this minor planet might be “a member of the Geminid stream complex.”56 Ohtsuka, Sekiguchi, Kinoshita, Watanabe, T. Ito, H. Arakida, and T. Kasuga (2006) suggested this minor planet was a fragment of the minor planet 3200 (Phaeton), which is considered to be the parent to the Geminid meteor stream. 57 Kinoshita, Ohtsuka, Sekiguchi, Watanabe, Ito, Arakida, Kasuga, S. Miyasaka, R. Nakamura, and H.-C. Lin (2007) announced that the surface colors of 3200 (Phaeton) and 155140 (2005 UD) are very similar, supporting their hypothesis that the two are related.58 222 10 September Meteor Showers

Several orbits have been determined during the last few decades. The orbit labeled “1961” was determined by Nilsson (1964). The orbit labeled “1968–1969” was determined by Sekanina (1976). The orbit labeled “1995–1999” was determined by P. Galligan and W. J. Baggaley (2002). The orbit labeled “2002–2008” was determined by Brown et al. (2010). The orbit of minor planet 155140 (2005 UD) is also provided.

w W (2000) i q e a 1961 213.2 4.3 21.8 0.146 0.87 1.12 1968–1969 212.3 15.8 31.1 0.172 0.816 0.94 1995–1999 212.5 6.1 23.1 0.151 0.855 1.06 2002–2008 212.99 6.0 22.0 0.1511 0.858 1.07 155140 207.56 19.77 28.69 0.1627 0.872 1.28

Alpha Triangulids

Unexpected meteor activity was independently observed from two different sites on the night of 1993 September 12 and subsequently reported to the International Meteor Organization (IMO). The observations were made by long-time ALPO members G. W. Kronk (Troy, Illinois, USA) and G. W. Gliba (Greenbelt, Maryland, USA), with Kronk being assisted by K. Sleeter (Swansea, Illinois). Kronk and Sleeter were observing deep sky objects from 04:00 to 05:15 UT and noted 11 meteors from the Aries-Triangulum region, including two which were seen through the telescope. The brightest meteor was estimated as magnitude 1, while all of the others were between magnitudes 3 and 4.5. There was no reasonable guess as to the actual amount of time spent watching for meteors, so no ZHR estimate could be made. By 05:15 UT, Kronk and Sleeter began looking exclusively for meteors, and continued to observe until 06:15 UT. They unfortunately were severely hampered by clouds for over one-half hour but still detected fi ve meteors of which three were from the Aries-Triangulum region. The magnitudes were all between 3 and 4.59 Gliba began observing meteors at 05:18 UT. He was located near Mathias, West Virginia (USA), at a private observing site for members of the Westminster Astronomical Society in Maryland (USA). He had just fi nished some extensive deep-sky observing and decided to put in some time looking for meteors. During the next 2 h, under very clear skies, he observed 35 meteors, of which 11 seem to have radiated out of the Aries region. Of these eleven, one was magnitude −2, another magnitude 1, and the remaining were between magnitudes 3 and 5. Kronk visually estimated the radiant as a = 35°, d = +30°, Sleeter plotted fi ve of his observed meteors on a star chart and obtained a radiant of a = 30°, d = +30°, and Gliba estimated his radiant was near Gamma Arietis, which indicated a radiant near a = 28°, d = +19°. Kronk and Sleeter had the good fortune of observing a short- trailed meteor just 10° south of Triangulum which generally confi rmed the right Alpha Triangulids 223 ascension of the radiant and indicated a declination more northerly than Gliba’s +19 deg, but Gliba noted his right ascension was more accurate than his declination because of the meteor distribution he observed. He suggested the radiant was diffuse and noted his radiant could subsequently be off by as much as 5° in any direction. Taking the three radiants and adding high weights to the declinations of Kronk and Sleeter, and the right ascension of Sleeter and Gliba, the resulting average radiant was a = 30°, d = +29°. This radiant is less than 2° from Alpha Trianguli. The meteors were moving at slow to medium speeds. A possible additional con fi rmation came from M. de Meyere (Deurle, Belgium). Between 00:00 and 02:00 UT on September 12, he was operating a forward scatter radio meteor detector and registered enhanced activity that was 17–83 % higher than during the same hours on all other dates during the period of September 1–15.60 A search for possible previous observations of this meteor shower found that the earliest comes from G. Zezioli (Bergamo, Italy), whose careful observations of 1867–1869 led to the completion of a list of 189 meteor radiants. Radiant number 152 was observed on September 23 from a radiant at a = 28°, d = +35°. An orbit was calculated by G. V. Schiaparelli (see below) which is very close to the orbits calculated for the 1993 observations.61 W. F. Denning (1878) analyzed meteor plots by the Italian Meteoric Association. He found 14 meteors seen during 1872 August 24–September 14 emanating from a radiant at a = 34°, d = +35°.62 H. Corder (1878) plotted 20 meteors from a radiant at a = 30°, d = +40° during 1877 September.63 Denning plotted six rapid meteors from a radiant at a = 29°, d = +36° on 1885 September 3–17.64 These are all of the nineteenth century observations, possibly indicating stronger than normal displays. The earliest twentieth century display was by Denning, when he plotted eight meteors from a radiant at a = 30°, d = +37° on 1902 September 3–7.64 Other observations appear in various journals as the century progresses, but the most interesting are those found in the records of the American Meteor Society (AMS) and in C. Hoffmeister’s book Meteorströme . First, on 1934 September 10, the radiant was observed by F. W. Smith in the United States and Hoffmeister in Germany. Second, in both 1940 and 1951, the radiant was detected independently by two AMS observers. There is reason to put a high confi dence upon the AMS data. First, the observers of the radiant in 1934, 1940, and 1951, were among the most prolifi c and experienced observers in the organization’s history: Smith, C. E. Worley, and J. H. Knowles. Second, in the days of C. P. Olivier, the AMS criteria for radiant determination was the intersection of four or more meteors within a circle of no more than 2.5°, which is more stringent than what some groups accept today. The next previous possible observations of this meteor shower appear in the 1968–1969 session of the Radio Meteor Project. Z. Sekanina (1976) found two streams that are particularly interesting: the “Alpha Triangulids” and the “Alpha Arietids.” The Alpha Triangulids were based on 13 radio-echo meteors, which indicated a nodal passage on September 8.8 ( l = 165.7°) from an average radiant at a = 30.4°, d = +29.5°. The duration was September 7.2–9.4 and the geocentric velocity was 26.6 km/s. The Alpha Arietids were based on six radio-echo meteor orbits, which indicated a nodal passage on September 8.9 (l = 165.8°) from an average radiant at a = 32.6°, d = +21.8°. The duration was September 7.2–9.3 and the 224 10 September Meteor Showers geocentric velocity was 53.3 km/s.65 The interest in these two meteor showers is that they were detected simultaneously, with the fi rst radiant being close to the radiant determined by Kronk and Sleeter in 1993 and the second radiant being close to the radiant determined by Gliba in 1993. Since these streams were only detected during the 1969 survey, that survey is supplemented by the raw data obtained by Sekanina, which amounted to 39,145 radio-echo meteor orbits, and search for additional meteors from this region during the period of 1962–1965, as well as 1969. It was hoped that if any members were found for the period of 1962–1965 their orbits could be combined with those detected in 1969 to more precisely determine the orbit. The result of the initial search was the detection of 47 meteors. Among those were perhaps fi ve potential streams. Both the “Alpha Triangulids” and “Alpha Arietids” were detected among this group, as well as three potential minor radiants de fi ned by four meteors or less. The “Alpha Arietids” exclusively appeared in 1969, so that the existing orbit could not be improved upon. The “Alpha Triangulids” produced meteors in 1962, 1963, and 1969 [the equipment did not operate between August 23 and September 21 during 1965, and no meteors were detected in 1964], which subsequently increased the overall number of radio meteors. However, it was then noted that a strong core of nine meteors was apparent. The average radiant was a = 27.5°, d = +28.8°. Some observations were made during 1994, which also helped to con fi rm the meteor shower’s existence. Gliba observed on the nights of September 10/11 and 11/12. He noted four meteors in the only hour observed on the fi rst night. For the second night, he observed for 4 h and noted hourly rates of 3–6.66 M. J. Currie (Grove, Oxfordshire, England) made observations on several nights using a 127 mm refractor. He said not possible Alpha Triangulids were noted on September 4/5, 5/6, or 6/7. He did note three members on September 8/9 (l = 166.1°), 5 on September 9/10 (l = 167.2°), 7 on September 10/11 (l = 168.1°), 14.5 on September 12/13 (l = 170.1°), and 1.5 on September 16/17 (l = 174.1°). Whenever the plot “did not yield an unequivocal result” it was considered a “half meteor.” Three half meteors were noted on September 12/13. Currie also determined radiants of a = 25°, d = +27° on September 8/9, a = 26°, d = +28° on September 9/10, a = 27.5°, d = +28.5° on September 10/11, and a = 30.5°, d = +29° on September 12/13. The daily motion of the radiant was +1.5° in a and +0.4° in d . He said his typical limiting magnitude through the telescope was +12.8. The brightest meteor seen was 4.0, while the faintest was 11.5. The average magnitude of the meteors was 9.32.67 During 2003, an analysis was made of the paths of 1906 meteor paths that had been accumulated around mid-September of 1996–2000 during the Polish Comets and Meteors Workshop. A. Olech conducted the analysis for the purpose of determining the existence of the “September Taurids,” the discovery of which was announced in 2002. No trace of this meteor shower was found; however, the RADIANT software did produce “maps of the probability for the presence of a radiant (hereafter PPR)” of two other radiants: The Delta Aurigids and the Alpha Triangulids. With respect to the latter, Olech wrote, “The highest PPR is observed on the border line between the Aries and Triangulum constellations … and can be connected with activity of the a -Triangulid shower.”68 Alpha Triangulids 225

The orbits labeled “Parabola,” “Ellipse #1,” “Ellipse #2,” and “Ellipse #3” were calculated using the radiant from the 1993 observations and several hypothetical velocities. The orbit labeled “1867–1869” is from Schiaparelli (1871). The orbits “ a TRI” and “ a ARI” are from Sekanina (1976). The orbit labeled “Core” was determined using nine of the radio-echo meteor orbits from Sekanina’s study.

w W (2000) i q e a Parabola 304.2 170.2 127.5 0.221 1.0 ∞ Ellipse #1 321.5 170.2 117.4 0.143 0.929 2.01 Ellipse #2 337.4 170.2 93.7 0.078 0.922 1.00 Ellipse #3 343.5 170.2 42.5 0.082 0.882 0.69 1867–1869 306 182 93 0.206 1.0 ∞ a TRI 345.9 166.4 38.7 0.087 0.870 0.67 a ARI 324.6 166.5 117.4 0.143 0.929 2.01 Core 344.1 166.5 36.1 0.097 0.857 0.68

1. W. F. Denning, The Observatory , 44 (1921 Oct.), p. 318. 2. W. F. Denning, The Observatory , 46 (1923 Nov.), p. 347. 3. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society , 95 (1935 Jun.), p. 717. 4. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 212, 217, 221. 5. C. P. Olivier, Flower Observatory Reprint , No. 146 (1964), p. 14. 6. Z. Sekanina, Icarus , 18 (1973), pp. 257, 260. 7. R. E. McCrosky and A. Posen, Smithsonian Contribution to Astrophysics , 4 (1961), p. 66. 8. J. Wood, Personal Communication (1986 Oct. 15). 9. C. Hoffmeister, Astronomische Nachrichten , 258 (1936 Jan. 11), pp. 25–6. 10. V. Guth, Astronomische Nachrichten , 258 (1936 Jan. 11), pp. 27–30. 11. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 120. 12. I. Tepliczky, WGN, Journal of the International Meteor Organization , 15 (1987), pp. 28–9. 13. J. Rendtel, WGN, Journal of the International Meteor Organization, 18 (1990 Jun.), pp. 81–4. 14. G. Zay and R. Lunsford, WGN, Journal of the International Meteor Organization , 22 (1994 Dec.), pp. 224–6. 15. J. E. Clark, Report of the Annual Meeting of the British Association for the Advancement of Science , 43 (1874), p. 396. 16. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 227, 229, 233. 17. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 18. Z. Sekanina, Icarus , 27 (1976), pp. 285, 299. 19. http://www.imonet.org/radiants/ 20. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 188. 21. W. F. Denning, The Observatory , 5 (1882 Sep.), p. 262. 22. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 318. 23. W. F. Denning, The Observatory , 3 (1880 Sep.), p. 536 24. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), pp. 443–4. 25. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912 Mar.), pp. 442–3. 26. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912 May), pp. 631–9 27. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923 Nov.), pp. 43–56. 28. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 88, 91, 124, 126, 226. 226 10 September Meteor Showers

29. J. M. Trigo-Rodríguez, WGN, Journal of the International Meteor Organization , 17 (1989), pp. 156–8. 30. A. K. Terentjeva, WGN, Journal of the International Meteor Organization, 17 (1989), pp. 242–3. 31. A. McBeath, International Meteor Organization 1992 Meteor Shower Calendar (1991), p. 10. 32. A. Dubietis and R. Arlt, WGN, Journal of the International Meteor Organization , 30 (2002), pp. 168–74. 33. R. Arlt and J. Rendtel, WGN, Journal of the International Meteor Organization , 34 (2006 Jun.), p. 80. 34. S. Molau and J. Rendtel, WGN, Journal of the International Meteor Organization , 37 (2009 Aug.), p. 109. 35. J. Rendtel and S. Molau, WGN, Journal of the International Meteor Organization , 38 (2010 Oct.), pp. 161–6. 36. http://www.imonet.org/showers/shw156.html 37. http://www.imonet.org/showers/shw158.html 38. P. G. Welch, Monthly Notices of the Royal Astronomical Society , 328 (2001), p. 107. 39. C. Hoffmeister, Meteorströme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 91, 139–40. 40. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 225. 41. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 16–17, 21–2. 42. A. F. Cook, B. A. Lindblad, B. G. Marsden, R. E. McCrosky, and A. Posen, Smithsonian Contributions to Astrophysics , 15 (1973), p. 4. 43. Z. Sekanina, Icarus , 18 (1973), pp. 257, 260, 267. 44. P. B. Babadzhanov, Solar System Research , 33 (1999), p. 60. 45. MP1961, pp. 67–9. 46. M. Buhagiar, Western Australia Meteor Section Bulletin , No. 160 (1981). 47. A. A. Weiss, Monthly Notices of the Royal Astronomical Society , 120 (1960), p. 399. 48. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), p. 159. 49. Z. Sekanina, Icarus , 27 (1976), p. 287. 50. D. Artoos, WGN, Journal of the International Meteor Organization , 17 (1989 Apr.), pp. 49–50. 51. D. Artoos, WGN, Journal of the International Meteor Organization, 19 (1991 Aug.), pp. 112–13. 52. D. P. Galligan and W. J. Baggaley, Dust in the Solar System and Other Planetary Systems . Edited by S.F. Green, I.P. Williams, J.A.M. McDonnell and N. McBride. Oxford: Pergamon, (2002), pp. 54, 58. 53. J. P. Younger, I. M. Reid, R. A. Vincent, D. A. Holdsworth, and D. J. Murphy, Monthly Notices of the Royal Astronomical Society , 398 (2009), pp. 353–4. 54. J. P. Younger, Personal Communication (2013 Jan.–Feb.). 55. Minor Planet Electronic Circulars , No. 2005-U22 (2005 Oct. 23). 56. K. Ohtsuka, T. Sekiguchi, D. Kinoshita, and J.-I. Watanabe, Central Bureau Electronic Telegram , No. 283 (2005 Nov. 11). 57. K. Ohtsuka, T. Sekiguchi, D. Kinoshita, J.-I. Watanabe, T. Ito, H. Arakida, and T. Kasuga, Astronomy & Astrophysics , 450 (2006), pp. L25–L28. 58. D. Kinoshita, K. Ohtsuka, T. Sekiguchi, J.-I. Watanabe, T Ito, H. Arakida, T Kasuga, S. Miyasaka, R. Nakamura, and H.-C. Lin, Astronomy & Astrophysics , 466 (2007), pp. 1153–8. 59. G. W. Kronk, WGN, Journal of the International Meteor Organization , 21 (1993 Dec.), pp. 261–3. 60. M. De Meyere, Personal Communication (1993 Sep.). 61. G. V. Schiaparelli, Entwurf einer Astronomischen Theorie der Sternschnuppen . Stettin : T. von der Nahmer (1871), pp. 90–1. 62. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 38 (1878 Mar.), p. 319. 63. H. Corder, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), p. 136. 64. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 72 (1912 May), p. 632. 65. Z. Sekanina, Icarus , 27 (1976), pp. 284, 298. 66. G. W. Gliba, Personal Communication (1994 Sep. 15). 67. M. J. Currie, WGN, Journal of the International Meteor Organization , 22 (1994 Dec.), pp. 220–23. 68. A. Olech, WGN, Journal of the International Meteor Organization , 31 (2003 Jun.), pp. 93–6. Chapter 11

October Meteor Showers

October Arietids

This shower is part of a cluster of radiants that is active in the Taurus-Aries region from the period of September through November. The complex nature of this region was ﬁ rst noted in 1928, when W. F. Denning published the details of 13 radiants. One of these radiants, the “Xi Arietids,” was said to be active during September and October from an average position of a = 30.9°, d = +9.6°, while another radiant, the “Sigma Arietids,” was said to be active during October from a = 41.9°, d = +13.7°.1 The currently known movement of the October Arietids would seem to link these two radiants. F. W. Wright and F. L. Whipple were the next to isolate the October Arietids when, during a 1950 investigation of the photographic Taurid meteors, they found eight photographic meteors which came from an average radiant of a = +41.3°, d = +10.3°. The mean date of activity was October 20–22.2 This study involved 102 meteors photographed from October 15-December 2, in the years 1896–1948. The authors expressed their opinion that the October Arietids might form a continuous stream with the southern Taurids, though they suggested further studies would be needed to clarify the situation. The use of radar equipment came of age during the 1950s but, despite numerous observations of the Taurids, the equipment was not yet sensitive enough to separate diffuse radiants close together. This changed in the early 1960s when two radio- echo studies detected the October Arietids.

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 227 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_11, © Springer Science+Business Media New York 2014 228 11 October Meteor Showers

B. L. Kashcheyev and V. N. Lebedinets used the radar system at the Kharkov Polytechnical Institute (Ukraine) during 1960 and detected 51 meteor streams. A total of 18 meteors were detected from the “Southern Arietids” which indicated a duration of October 10–21. The radiant was determined as a = 40°, d = +15°.3 C. S. Nilsson used the radio equipment at the University of Adelaide (South Australia, Australia) during 1961 and detected 30 meteors from a stream designated “61.10.1,” which they called the “Southern Arietids.” The duration was given as October 20–31, while the geocentric velocity was 29 km/s. The date of nodal passage came on October 26 (l = 213.0°), when the radiant was at a = 44.8°, d = +12.4°. Nilsson may have also detected this shower during the last days of September. He contemplated the matter after noting a similarity between stream 61.10.1 and a stream designated 61.9.1. The latter stream was detected during September 22–29, from an average radiant of a = 18.1°, d = +4.9°. It was based on 19 meteors and determined the geocentric velocity as 28.6 km/s. Nilsson found the orbit of 61.9.1 to closely resemble the orbit of the Daytime Zeta Perseids. He added, “It is just possible that the two streams 9.1 and 10.1 are both part of a wide band of meteors, but consideration of the characteristics of the October Arietids and November Taurids does not encourage this view.”4 Note that the radio equipment at Adelaide was not operational during 1961 September 30 to October 19. The two sessions of the Radio Meteor Project conducted during the 1960s at Havana, Illinois (USA), also succeeded in detecting the October Arietids. Z. Sekanina said the 1961–1965 session revealed activity during September 11- October 23. The date of the nodal passage was given as October 1.4 ( l = 187.8°), at which time the radiant was at a = 23.9°, d = +8.8°. 5 From data compiled during the 1968–1969 session, Sekanina gave the duration as September 7-October 22. The date of the nodal passage was given as October 11.5 ( l = 197.8°), while the average radiant was at a = 32.3°, d = +10.2°. 6 The October Arietids are a neglected shower among visual observers and, if not for the photographic and radar programs, virtually nothing would be known of this stream. Most of this neglect is probably due to the Southern Taurid stream which moves through a region of the sky a few degrees to the southwest. This latter shower is also a larger producer of meteors, with rates typically near 10 per hour. One of the most signi ﬁ cant visual studies was conducted while seven Russian astronomers observed the Orionids during 1973 October 17–21. Coordinated by G. N. Sizonov, the observations took place from the meteor station of Armavir middle school #18. Combined observations of the October Arietids revealed an average magnitude of 3.37, based on 43 magnitude estimates, and a maximum ZHR of 3.4. Sizonov showed the highest ZHR to have occurred on October 20, at which time the average distance between particles within the stream was 484 km, and the spatial density of particles per cubic kilometer was 8.90 × 10−9 . 7 From analyzing the photographic meteors of both the October Arietids and the Southern Taurids, it can be noted that the radiants of each stream remain fairly close together. At the time they both appear in mid-September, the October Arietids are 7° east of the Southern Taurids, while they are about 4° northeast at the end of Delta Aurigids 229

October. Both streams also possess diffuse radiants, so that it is nearly impossible to visually separate one from the other. The October Arietid details were based on 48 photographic meteors that had been detected during 1936–1962. This analysis also revealed the October Arietid daily motion to be +0.90° in a and +0.35° in d . The orbit labeled “1936–1962” was determined based on 48 photographic meteors detected in the United States and Tajikistan. The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The orbits labeled “61.9.1” and “61.10.1” are from Nilsson (1964).

w W (2000) i q e a 1936–1962 125.2 16.1 6.4 0.280 0.846 1.818 1960 131 23 1.2 0.24 0.86 1.74 1961–1965 127.0 8.4 1.4 0.273 0.841 1.723 1968–1969 122.6 18.4 2.9 0.333 0.768 1.435 61.9.1 125.7 3.0 5.4 0.34 0.83 1.64 61.10.1 118.3 33.7 5.9 0.28 0.83 2.00

Delta Aurigids

Duration: September 18 to October 18 (l = 197°–205°) Maximum: October 11 (l = 198°) Radiant: a = 84°, d = +44° ZHR: 2

Radiant Drift: a = +1.2°, d = +0.1° V G : 64 km/s This meteor shower was discovered in 1979, while J. D. Drummond, R. K. Hill, and H. A. Beebe (New Mexico State University, New Mexico, USA) were determining the orbits of 13 meteors doubly photographed during 1976 and 1977 at the NASA- NMSU Meteor Observatory in southern New Mexico. Two of the 13 meteors had nearly identical orbits and had been photographed on 1977 October 13 and 18. It was concluded that the possible date of maximum might have occurred during 1977 October 15–16, from an average radiant at a = 95.7°, d = +52.5°. 8 The ﬁ rst observations of this shower occurred during 1980 October, as N. W. McLeod, III (Florida) and Drummond (New Mexico) carried out independent visual observations. McLeod’s observations began early as he noted one meteor in 4.6 h on October 6, 1 in 0.8 h on the 10th and 0 in 2.7 h on the 12th. Both men observed on the 13th, with McLeod noting 2 in 1 h and Drummond detecting 3 in 2 h. Drummond’s observations of the 14th and 15th revealed 2 in 2 h and 5 in 2 h, respectively—the latter being the highest determined hourly rate of 2.5 per hour. Observations continued from the 16th to the 22nd, with the Delta Aurigids being either nonexistent or possessing hourly rates of 1 or less.9 230 11 October Meteor Showers

During 1981, Drummond isolated fi ve probable members of this stream that had been photographed by American and Russian surveys conducted between 1950 and 1962. Combining these fi ve with the two meteors from the 1977 NASA-NMSU survey, Drummond concluded that the shower’s duration might be from September 29 to October 18. The mean date of activity was October 8, with the radiant at a = 87.8°, d = +50.2°. The shower’s daily motion was given as +1.0° in a and +0.1° in d. Lastly, the stream’s mean orbit, based on the seven photographic meteors, is a retrograde orbit with a period of 115 years. Drummond pointed out that the visual observations of 1980 only covered the second half of the indicated shower duration and that the determination of the shower’s true maximum “must await further observation from the fi rst half.”9 During the mid-1980s, a search through 39,145 radio meteor orbits obtained during the two sessions of the Radio Meteor Project isolated 24 probable Delta Aurigids. The radio meteors indicate a peak about 1 week before the photographic meteors. In addition, their semimajor axis is only 2.3 AU, compared with 18.7 AU for the photographic meteors. When the radio and photographic meteors are combined, the meteor stream seems to be composed of four fi laments as follows: • Filament “A” reaches maximum on September 30 (l = 187.2°), from an average radiant of a = 87.8°, d = +54.1°. It possesses the largest perihelion distance (0.95 AU) of the four possible fi laments and is composed of 11 meteors—one being photographic. • Filament “B” reaches maximum on October 7 (l = 193.9°), from an average radiant of a = 87.5°, d = +50.2°. It possesses the largest semimajor axis of the four fi laments (4.5 AU) and is the probable main core of this stream. It was based on 13 meteors, with six being photographic. • Filament “C” is the weakest fi lament, but seems to reach maximum on October 13 ( l = 200.0°), from an average radiant of a = 91.1°, d = +47.8°. It possesses the highest inclination (133°) and the smallest perihelion distance (0.75 AU) of the four fi laments. It was based on four meteors, with two being photographic. • Filament “D” reaches maximum on October 2 (l = 188.9°), from an average radiant of a = 74.3°, d = +55.0°. It possesses the smallest inclination (116°) and the smallest semimajor axis (2.2 AU) of the four fi laments. It was based on fi ve radio meteor orbits. Searches for previous sightings of the Delta Aurigid shower have not revealed much, with the only possible nineteenth century observation coming from W. F. Denning. He plotted six meteors during 1876 October 14–17 and determined the radiant as a = 90°, d = +58°. The meteors were described as rapid, with streaks.10 This radiant is the closest nineteenth century match for the Delta Aurigids, but is only borderline according to the D-criterion. Prior to Drummond’s initial announcement of this meteor shower, the only possible visual observations of the twentieth century appear in C. Hoffmeister’s Meteorströme . He lists radiants at a = 86°, d = +57° on 1910 October 1 (l = 187°), a = 84°, d = +48° on 1920 October 9 ( l = 195.4°), and a = 83°, d = +48° on 1935 October 7 ( l = 193.8°).11 The fi rst radiant seems a good example of a fi lament “A” Delta Aurigids 231 shower, while the latter two radiants probably belong to fi lament “B”. Seven additional radiants also appear but are strictly borderline, according to the D-criterion. These seven radiants might belong to fi laments “A”, “B”, and “C”. There are no close candidates for fi lament “D” indicating that it may be composed mostly of small, telescopic particles—if it exists at all. A. McBeath (1992) examined observations made during 1984–1990 by the JAS Meteor Section and found evidence for the Delta Aurigids. Although the observers generally noted only the meteor direction and approximate length of the path, McBeath said there was evidence to support this meteor shower. With respect to the fi laments noted above, he said their results “show a reasonable match for [Kronk’s] four fi lamental maxima…and gives some support to his conclusion of a general maximum apparent from October 6 to 15….” McBeath added, “The limiting dates of September 22 to October 23…do not seem to be confi rmed however, nor does the suggestion that fi lament “B” represents the stream’s main core, but it would be unwise to try to be too precise about these matters based only on the current results.” 12 For many years, the IMO concluded from radiant and velocity data that the Delta Aurigids and September Perseids were one continuous stream. J. Rendtel (1993) suggested the accepted Delta Aurigids were actually two streams, with the September Perseids actually peaking on September 12 and the Delta Aurigids peaking on October 8. 13 An extensive study of the Delta Aurigids was published by A. Dubietis and R. Arlt (2002). They argued that the evidence revealed that the Delta Aurigids were actually two similar but distinct meteor showers. Using the Visual Meteor Database of the IMO, they found 3473 Delta Aurigids were reported during the period of 1991–2001. They divided the data into two periods (1991–1995 and 1996–2001) and conducted two separate analyses. They found that both sets of data indicated two peaks. They concluded that the fi rst peak was the September Perseids and occurred on September 9 ( l = 166.7°) with a ZHR of 4.5, while the second peak was less precise, but occurred on September 24 ( l = 181°) with a ZHR of 2.6. They added that the Delta Aurigid maximum “seems to be rather fl at and not well pronounced with the activity level being just slightly above the visual detection limit (ZHR ³ 1).” The population index was determined as r = 2.46 for the September Perseids and r = 2.91 for the Delta Aurigids.14 Arlt and J. Rendtel (2006) suggested that the duration for these two streams be established as September 5–17 for the September Perseids and September 18-October 10 for the Delta Aurigids.15 Rendtel and S. Molau (2010) examined meteor activity in the Perseus-Auriga region for the months of September and October using data collected by the IMO Video Meteor Network over 11 years. They found 744 meteors to represent the Delta Aurigids, indicating a duration of October 9–16 (l = 196°–203°). Maximum came on October 11 (l = 198°) from a radiant at a = 84°, d = +44°. The daily radiant drift was given as +1.1° in a and −0.4° in d . 16 The following orbits were determined. The orbit labeled “Photo” is based on ten photographic meteor orbits. The orbit labeled “Radio” is based on 24 radio meteor orbits. The orbit labeled “P-R” is an average of all of these photographic 232 11 October Meteor Showers and radio meteor orbits. The orbits labeled “A”, “B”, “C”, and “D” represent the four fi laments discussed above.

w W (2000) i q e a Photo 229.5 196.0 131.1 0.823 0.956 18.71 Radio 226.4 189.3 123.9 0.878 0.617 2.29 P-R 227.1 191.6 125.9 0.859 0.720 3.07 A 210.2 187.2 123.4 0.951 0.621 2.51 B 229.4 193.9 129.5 0.848 0.810 4.46 C 243.5 200.0 132.6 0.753 0.793 3.64 D 245.2 188.9 116.4 0.773 0.648 2.20

Only one known comet seems to have an orbit similar to that of the Delta Aurigids—comet C/1972 E1 (Brad ﬁ eld). The link should not be considered de ﬁ nite, but its orbit is given here as follows:

w W (2000) i q e a 1972 E1 257.70 160.30 123.69 0.9272 0.9981 494.78

Eta Cetids

This stream might be similar in nature to the Aurigids of February as they seem to possess a very weak, almost nonexistent shower with occasional fi reballs thrown in. The duration of activity stretches from September 20 to November 2 (l = 177°– 220°), while the maximum occurs during the fi rst week of October from a radiant of a = 15°, d = −13°. The fi rst recognition of this area as a producer of fi reballs came in 1964, when C. P. Olivier published the “Catalog of Fireball Radiants” as an American Meteor Society publication offered through Flower and Cook observatories. Designated radiant number 5148, it was based on 6–8 fi reballs. The mean date of activity was given as October 4, with a radiant of a = 10°, d = −18°. Activity was also present 3 days before and after this mean.17 One of the most spectacular fi reballs attained a magnitude −20. It was photographed by nine of the 16 cameras of the Prairie Network (designated 40503) on 1969 October 9.30 (l = 196.2°), from a radiant of a = 18.0°, d = −17.7°. Another very bright stream member was detected by observers in Florida on 1972 October 8.3 ( l = 195.5°). Reaching a magnitude of −14, its radiant was determined as a = 8°, d = −11°. October Cetids 233

The investigation of the 39,145 radio meteor orbits obtained by Z. Sekanina during the two sessions of the Radio Meteor Project has uncovered 16 orbits. The following orbit is the average of these radio meteor orbits, as well as six photographic meteors obtained from surveys in the 1950s.

w W (2000) i q e a 75.6 15.5 10.0 0.70 0.67 2.10

October Cetids

C. S. Nilsson (1964) discovered this weak meteor shower during an analysis of data gathered by the radio-echo equipment at the University of Adelaide (South Australia, Australia) during 1961. He detected stream members during October 23–30 and noted that the nodal passage occurred on October 27 (l = 213.9°) from an average radiant at a = 39.3°, d = +0.2°. The geocentric velocity was determined as 27.1 km/s. The equipment did not operate during September 30-October 19, so the early part of the shower’s activity might have been missed.18 The shower was detected by both sessions of the Radio Meteor Project. During an analysis of the 1961–1965 data, Z. Sekanina (1973) found a stream that he called the “Beta Cetids.” The duration was given as September 8 to October 1. Its nodal passage was given as September 25.7 ( l = 182.2°), while the average radiant was a = 16.3°, d = −11.7°. The geocentric velocity was determined as 23.6 km/s.5 Sekanina (1976) analyzed the data from the 1968 to 1969 session and identi fi ed a stream called the “Delta Piscids” that might be associated. The duration was given as September 22-October 22, while the nodal passage occurred on October 5.2 ( l = 191.6°), at which time the radiant was at a = 12.5°, d = +4.2°. The geocentric velocity was determined as 20.5 km/s.19 The radio equipment was again operated at the University of Adelaide during 1969. G. Gartrell and W. G. Elford (1975) analyzed the data and found four meteors during the period of October 15–19 that probably represent this stream. The date of the nodal passage was October 16 (l = 203°), while the average radiant was at a = 28°, d = +3°. The equipment had been shut down since mid-June, so the early part of the activity was de fi nitely missed.20 A search through publications containing lists of visible radiants reveals that the earliest sighting of this meteor shower was by W. F. Denning (Bristol, England) on 1885 October 7, when he recorded the paths of fi ve slow meteors from a radiant at a = 31°, d = +8°.21 H. Corder (England) reported plotting four slow meteors during 1897 October from a radiant at a = 30°, d = +10°. 22 Denning provided observations almost two decades later. During 1916 October 20–25, 4 meteors were seen from a radiant at a = 28°, d = +4°. The meteors were described as rapid.23 On 1917 October 16, a 1st-magnitude stationary meteor was observed from a = 28°, d = +3°. 24 234 11 October Meteor Showers

The orbit labeled “1961” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976).

w W (2000) i q e a 1961 94.0 34.6 13.9 0.52 0.86 3.70 1961–1965 102.4 2.9 14.6 0.493 0.725 1.79 GE1975 96 24 8.2 0.47 0.90 4.17 1968–1969 93.8 12.1 0.7 0.566 0.693 1.84

As previously noted, the data published by Nilsson (1964) and Gartrell and Elford (1975) did not cover the early half of this stream’s activity, thus giving the indicated nodal passages little meaning. In addition, the orbits from these two surveys were each based on only three meteors, so the reliability should not be considered very high. The orbits obtained in each of Sekanina’s surveys should be considered more reliable, as they were based on about 10 and 45 meteors, respectively. Most interesting is the inclination change between the 1961–1965 and 1968–1969 surveys, but this may be a result of the different selection methods being used: the early study used a D-criterion of 0.20, while the second survey used a less stringent value of 0.25. After obtaining the 39,145 radio meteor orbits computed by Sekanina during the 1960s, 57 radio meteors were found that are probable members of this stream. Combined with 13 photographic meteors found in various sources, the subsequent orbit was obtained:

w W (2000) i q e a 95.4 15.9 7.3 0.529 0.745 2.08

By utilizing a D-criterion value of about 0.15, it is found that this stream splits into northern and southern branches. The fairly compact northern branch was composed of 46 radio and photographic meteors, while the more diffuse southern stream was composed of 16 meteors.

w W (2000) i q e a Northern 95.4 16.9 4.2 0.537 0.740 2.07 Southern 96.0 14.3 13.6 0.528 0.744 2.06

The northern branch is de ﬁ nitely the strongest portion of this stream, but neither branch is especially strong visually, and most likely telescopic aid will probably be necessary for future observations. The northern branch has a duration of September 20-October 27, with maximum occurring on October 9 (l = 196.2°) from a radiant October Cygnids 235 at a = 20°, d = +2°. The daily motion of the radiant is +0.95° in a and +0.35° in d . The southern branch has a duration of September 14-October 22, with maximum occurring on October 6 (l = 193.6°) from a radiant at a = 23°, d = −8°. The daily motion of the radiant is +0.81° in a and +0.25° in d . What makes this stream especially interesting is its orbital similarity to the Apollo asteroid 69230 Hermes.

w W (2000) i q e a Hermes 92.68 34.26 6.07 0.6224 0.6240 1.66

This asteroid’s ascending node occurs around October 29, which coincides with the end of the October Cetid shower.

October Cygnids

The ﬁ rst detection of this radiant should be attributed to C. Hoffmeister (Germany), who observed a radiant at a = 305°, d = +57° on 1931 October 9 (l = 195.6°).25 Although additional visual observations seem quite rare, this radiant has been detected by both radar and photography. Six photographic meteors were located from photographic surveys conducted by Harvard College Observatory (Massachusetts USA), which indicate a duration extending from September 26 to October 10. The nodal passage seems to occur on October 6, at which time the average radiant is at a = 311.3°, d = +54.7°. The average orbit of these meteors is as follows:

w W (2000) i q e a 207.1 193.4 29.9 0.953 0.734 3.58

Two meteor streams were detected during the 1961–1965 session of the Radio Meteor Project. The “Delta Cygnids” had a duration of October 4–10. The date of the nodal passage was given as October 8.9 (l = 195.2°), at which time the radiant was at a = 299.7°, d = +50.7°. The “Alpha Cygnids” had a duration of September 22-October 11. The date of the nodal passage was given as October 4.4 (l = 190.8°), at which the radiant was at a = 316.3°, d = +52.3°.5 Their orbits are

w W (2000) i q e a Delta CYG 198.6 195.9 25.0 0.976 0.647 2.76 Alpha CYG 216.0 191.5 25.5 0.930 0.538 2.01 236 11 October Meteor Showers

The International Meteor Organization (IMO) has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. There are indications that this shower was detected. On October 4 ( l = 192.0°), 78 meteors emanated from a radiant at a = 318.3°, d = +57.5°. On October 5 (l = 193.0°), 72 meteors emanated from a radiant at a = 317.4°, d = +53.0°. On October 6 (l = 194.0°), 109 meteors emanated from a radiant at a = 304.5°, d = +54.0°. Additional observations are evident on other days.26

Draconids (“Giacobinids”)

Duration: October 6 to October 10 (l = 193°–197°) Peak: October 8/9 (l = 195.4°) @ a = 262°, d = +54°

Radiant Drift: a = UNK, d = UNK V G : UNK km/s The discovery of this meteor shower resulted from predictions by several astronomers that the periodic comet 21P/Giacobini-Zinner might produce a radiant in early October; however, this meteor shower would eventually have been discovered anyway, because of a major outburst in 1933. The fi rst to make such a prediction was M. Davidson (1915), who examined the periodic comets observed since 1892 to fi nd any that might be capable of producing meteor showers. He found that the orbit of comet Giacobini-Zinner would be fairly close to Earth on 1915 October 10 and predicted that, if the debris from this comet had spread outward by about two million miles, a shower might be active from a radiant at a = 267°, d = +50°. 27 This was about 2 years after the parent comet had passed perihelion. During the fi rst half of October, W. F. Denning (Bristol, England) recorded “a number of meteors” from a = 267°, d = +49°.28 Davidson revised his prediction in 1920 (primarily due to an error discovered in his earlier prediction), saying that the distance between the orbits of the comet and Earth amounted to 5 1/2 million miles. He subsequently suggested that maximum would most likely occur on October 9 from a radiant at a = 251.5°, d = +55.9°. 29 Later that same year, Denning plotted fi ve meteors from a = 268°, d = +53° during October 6–9. 30 These meteors were described as slow. Giacobini-Zinner had passed perihelion during the spring of 1920. The comet was next expected at perihelion at the end of 1926, and Davidson and A. C. de la C. Crommelin published predictions for a meteor shower in October of that year. Both men gave October 10 as the expected day of maximum, and they gave similar radiants of a = 261°, d = +53.5° and a = 265°, d = +54°, respectively. The orbits of the comet and Earth were found to intersect in 1926, though the expected shower would occur 70 days before the comet passed that point of its orbit. 31 According to a summary written by Denning, several experienced observers were watching on the night of October 9/10; however, what initially caught the attention of observers that evening was the appearance of a fi reball at 10:16 p.m. Draconids (“Giacobinids”) 237

The event was noted by hundreds in the British Isles and 35 reports allowed the radiant to be determined as a = 262°, d = +55°. The meteor moved slowly and lit up the sky. A persistent train lasted about 30 min “during which time it underwent curious changes of form and exhibited drift amongst the stars.” Thereafter, a number of meteors were observed from the radiant predicted by Davidson and Crommelin. J. P. M. Prentice (Stowmarket, Suffolk, England) observed for 3 h centered on October 9.9, and detected 16 meteors from a = 263°, d = +54°. He described the meteors as slow and estimated the radiant diameter as 6°. He claimed that the hourly rate may have been near 17 had his observations been continuous. Observations made by A. King (Ashby, England) and Denning gave a radiant of a = 255°, d = +56°.32 A few observers continued to monitor for additional Draconid activity in the years following 1926. During 1927–1932, Prentice observed extensively around October 9–10, but no activity was detected; however, the skies opened up again on 1933 October 9. Comet Giacobini-Zinner had passed perihelion on 1933 July 15, and, on the date of the predicted maximum, Earth crossed the area of the comet’s descending node just 80 days after the comet. Astronomers were not prepared for what was in store for them, but, as evening twilight fell over Europe, observers noted the beginnings of something unusual. Within just a couple of hours the number of Draconids sky- rocketed, and, at 20:00 UT, one of the best displays of the twentieth century was in progress. Some of the more impressive observations follow. These were published by King in the 1933 November and December issues of The Observatory.33, 34 • Northern Ireland: W. F. A. Ellison (Armagh Observatory) reported that meteors fell as frequently as snowﬂ akes, and he gave the radiant as a = 266°, d = +55°. W. H. Milligan (near Amagh) saw thousands, including 100 during one 5 s interval. The radiant was a = 264.5°, d = +54.5°. • Malta: R. Forbes-Bentley (Birchircara) observed over 22,500 meteors in just a few hours and estimated the peak rate hit 480 per minute at 20:15 UT. The meteors were described as mostly faint, with only 5 % reaching ﬁ rst magnitude. The radiant was estimated as a = 262.5°, d = +55°. • Russia: N. N. Sytinskaja (Leningrad) collected numerous observations made from 18:00–22:00 UT. At maximum, rates reached 100 per minute at Leningrad, 300 per minute at Pulkovo and 200 per minute at Odessa. • Spain: P. M. Ryves (Zaragoza) estimated a maximum rate of 100 per minute and an average radiant of a = 266°, d = +53.5°. He said the meteors were generally faint with the “great majority of the meteors being 3rd to 5th mag.” It was generally agreed that the shower’s maximum rate reached more than 100 per minute, or over 6,000 per hour, around 20:15 UT on October 9. The meteors were described as slow, generally faint, and were usually yellow. Following the 1933 appearance, the Draconids again became nonexistent. The comet’s next perihelion date was 1940 February 17, and there were numerous predictions of a possible strong return in 1939 October; however, Earth crossed the comet’s orbit 136 days ahead of the comet which meant bad news for meteor 238 11 October Meteor Showers

enthusiasts, as no storm—or even a small shower—appeared. During 1940–1945, activity continued to be absent, but astronomers were already making predictions for the very favorable 1946 return. In that year, the comet was expected at perihelion on September 18, so that Earth would cross the comet’s orbit just 15 days after the comet! The Draconids were best placed for observers in the Western Hemisphere during October 9/10, and excellent meteor counts not only came from all across the United States, but also from Canada and even Venezuela. European observers did detect the Draconids, but the radiant was very low over the horizon and, though spectacular, it was at least one-fourth the strength of that seen in the Americas. Observations were also made in Czechoslovakia for slightly more than one hour prior to morning twilight. Some of the more interesting observations are as follows: • Oklahoma (USA): B. S. Whitney led a team of ten observers during the period of 1:23 and 4:34 UT. Taking counts every 10 min, they determined that maximum came around 3:50 UT (October 10) when estimated hourly rates were near 3,000. 35 • California (USA): R. Michaelis and K. Bouvier (Grif fi th Observatory) observed rates of 55 per minute between 3:45 and 4:02 UT. E. L. Forsyth (Fallbrook) detected 63 per minute at 3:50 and G. W. Bunton (Sunland) observed 180 per minute around this same time.36 • England: Prentice evaluated the British observations and noted a maximum hourly rate of 965 per hour. The radiant was then very low over the horizon, and it was determined that the ZHR was actually 2,250.37, 38 • Skalnate Pleso Observatory (Czech Republic): observers fought clouds, moonlight, and morning twilight to observe the Draconids. Maximum occurred at 3:53 UT with a corrected rate of 6,800 per hour. Two secondary maxima occurred at 3:23 and 3:40. Analysis revealed the half-time of the shower to have been 0.65 h.39 The 1946 event marked an important fi rst for meteor astronomy—the detection of a meteor shower by radar. In the United States alone, 21 radar systems were operated at frequencies of 100, 600, 1,200, 3,000, and 10,000 Mc/s. From these instruments, only the radar operating at 100 Mc/s detected meteor echoes. The majority of all meteor activity occurred between 3:00 and 4:30 UT on October 10.40 Perhaps the most extensive survey was conducted in England during October 7–11. J. S. Hey, S. J. Parsons, and G. S. Stewart (1947) told of their results using equipment operating at a 5 m wavelength. Radio-echo meteors were detected at a fairly constant rate during October 7 and 8. Starting at 20:00 UT on the 9th, they noted a de fi nite increase in echoes, which reached a minor peak during 22:00–23:00 UT. Following 0:00 UT on the 10th, the authors noted “a steep rise in numbers,” with the peak occurring during 3:30–4:40 UT. The overall enhanced activity had ended by 8:00 UT. An important fi rst for this method of detecting meteors was the determination of the geocentric velocity. A total of 22 of the meteor tracks revealed a velocity of 22.9 km/s.41 Draconids (“Giacobinids”) 239

Most interesting was a record obtained by Harvard professor J. A. Pierce, who used a 3.5 Mc/s pulsed ionospheric sounder and found that meteors were so numerous that a temporary ionosphere was formed at a height of 90 km.42 This meteoric ionosphere lasted 3 h and was con fi rmed elsewhere. Following 1946, both visual and radio-echo techniques were utilized in searches for this shower during 1947–1951. Visual observers detected no meteors possibly associated with the Draconids, while radio-echo observations at Jodrell Bank detected “no activity during the Giacobinid epoch in excess of the background sporadic rate (that is, not greater than 4 or 5 per hour).”43 A possible shower was predicted for 1952 October 9. Various calculations revealed Earth would cross the comet’s orbit 193 days ahead of the comet. In addition, the closest distance between the orbits of Earth and Giacobini-Zinner was very similar to that of 1933, or about 0.0057 AU; however, on this occasion, the comet’s orbit would actually pass inside of Earth’s orbit. Visual observations by British observers revealed only the barest hint of activity shortly after sunset on October 9/10, but, just a few hours earlier, daylight observations had been made using the radio-echo apparatus at Jodrell Bank in England. The Jodrell Bank team fi rst noted the Draconid rate rising above that of the sporadic background at 14:20 UT on October 9. Meteor echoes were counted during 10 min intervals: 3 were noted at 15:00 UT, there were 6 at 15:10 UT, 10 at 15:20 UT, 11 at 15:30 UT, and 17 appeared at 15:40 UT. The highest rates occurred at 15:50 UT, when 29 meteors were detected in 10 min—indicating an hourly rate of 174. The following decline in activity was very rapid, and one-half hour after maximum the 10 min rate had declined to only three. The last de fi nite sign of activity occurred at 16:40 UT, when the rate was two. The Jodrell Bank observers concluded that maximum occurred at a solar longitude of 196.25° from a = 262°, d = +54°. 44 The 1959 return of Giacobini-Zinner was very favorable and, since Earth arrived at the comet’s orbit just 21.6 days before the comet passed through the region, some believed a meteor storm would occur; however, perturbations by Jupiter had moved the comet’s perihelion distance closer to the sun so that the closest distance between the orbits of Earth and the comet was 0.058 AU. Subsequently, no shower was observed. The comet’s 1966 return also failed to produce meteors due to unfavorable geometric conditions. Important details of the Draconid meteor stream were obtained during the 1960s as a result of Harvard’s Radio Meteor Project. The surveys used radio equipment in Havana, Illinois (USA) during 1961–1965 and again in 1968–1969. The data was analyzed by Z. Sekanina. In his fi rst paper published in 1970, Sekanina examined the data acquired during the fi rst session. He said that although the equipment operated on October 8 and 9 for 4 years, “no meteors have been found to move in orbits notably close to the comet’s orbit. Instead, a number of meteors have been detected in orbits similar to the comet’s in shape, node, and longitude of perihelion, but with inclinations about 20° higher.” The duration was determined as September 23-October 12, with the nodal passage occurring on October 5.8. The average radiant was given as a = 262.8°, d = +77.7°, while the geocentric velocity was 30.3 km/s. 240 11 October Meteor Showers

Sekanina suggested these meteors “are not directly related to the Draconid shower” that produced the outbursts, but “might be associated” with comet Giacobini- Zinner.45 During the second session, Sekanina said the facility operated during 1969 October 6–10 and detected meteors from this stream on each day. The nodal passage came on October 8.2 and the average radiant position was a = 268.8°, d = +77.7°. The geocentric velocity was determined as 28.6 km/s.19 Giacobini-Zinner passed only 0.58 AU from Jupiter during 1969, which acted to increase its perihelion distance to 0.99 AU, meaning that Draconid showers were again possible. Searches for activity began during 1971 October, with Earth crossing the comet’s orbit 309 days before the comet. No notable activity was observed by members of the American Meteor Society during October 7–10, as hourly rates remained around one.46 The 1972 Draconids were looked for with much anticipation. Not only was Earth going to cross the comet’s orbit 58.5 days after the comet, but the two orbits were separated by only 0.00074 AU! Unfortunately, despite these promising statis- tics, the shower was quite a disappointment. Observers in the United States obtained the highest visual rates when 10–15 per hour were detected on October 8/9. Maximum had been predicted for 17:00 UT on October 8, which made Japan the best location for observations. Unfortunately, the Japanese observers were met with cloudy skies. Despite this hindrance, the Hiraiso Branch of the Radio Research Laboratory operated a 27.1-MHz radar. A peak of 84 returns in 10 min was noticed at 16:10 UT on October 8, followed by a secondary peak of 69 returns in 10 min at 21:00 UT.47 Further predictions for Draconid showers in 1978–1979 and 1985–1986 were not met with noticeable displays. Comet Giacobini-Zinner returned to perihelion on 1985 September 5 and was followed a month later by another enhanced Draconid display. International Astronomical Union Circular number 4120 was published on October 11 and provided details of observations made in Japan on October 8. Y. Yabu (Omihachiman, Shiga, Japan) gave hourly rates as 200 at 9:40 UT, 100 at 10:00 UT, and 10 at 11:00 UT. K. Watanabe and K. Nose (Sapporo Science Center) saw 83 meteors during the period of 10:40–11:40 UT and said maximum occurred prior to 10:00 UT. Y. Takeuchi (Tochigi, Japan) saw 39 meteors in 14 min centered around 10:00 UT.48 Additional reports indicated observations were also made in the North America and Europe. B. A. Lindblad (1986) discussed radar observations that had been conducted at the Onsala Space Observatory (Sweden) on October 8 and 9. He said Draconid activity “rose signiﬁ cantly above the background level” at about 8:40 UT. The peak occurred around 9:35 UT (l = 194.55°). The activity ended around 11:10 UT. The maximum occurred 3 h and 35 min prior to Earth crossing the region of the comet’s descending node.49 Weak activity was detected by E. P. Bus (Groningen, the Netherlands) using the radio forward scatter technique during 1996, even though the comet was not due to pass perihelion until late 1998. Bus said that since 1993, he has noted that around the time Earth crossed the plane of comet Giacobini-Zinner’s orbit, “the number of meteor re ﬂ ections was slightly higher than on the day before or after.” He suspected this “was caused by particles of the comet.” On 1996 October 8, Bus said activity Epsilon Geminids 241

“rose clearly above ‘sporadic’ background level” after 7:30 UT. Maximum rates of nearly 60 meteor refl ections per hour came at 8:50 UT, “almost coinciding with the descending node of Comet 21P/Giacobini-Zinner.” For an hour after the peak, Bus said there was an increase in long-duration re fl ections.50 The 1998 display was highly anticipated, although the Moon was 87 % full. L. Kresák had predicted the October 8 peak would occur at 17:00 UT, while M. Langbroek published a prediction of 21:00 UT. 51 From the observations of 87 observers, R. Arlt (1998) determined that maximum actually came on October 8 at 13:10 UT, which was 8 h prior to the nodal longitude of the comet. Activity with ZHRs of 5–10 was present for “several days before and after the Draconid peak,” while the maximum ZHR was about 720.52 Despite the comet’s expected perihelion passage in 2005 July, no substantial outburst was expected from the Draconids; however, the Canadian Meteor Orbit Radar (CMOR), which had been operating continually since 2002, detected signi fi cantly increased rates, which peaked on October 8 at 16.1 UT (l = 195.42°). According to M. Campbell-Brown, J. Vaubaillon, P. G. Brown, R. J. Weryk, and R. Arlt (2006), “Numerical modelling of radar-sized Draconids show that a signifi cant number of meteoroids from the 1946 perihelion passage of 21P/Giacobini- Zinner encountered the Earth…in 2005, centered about [l =]195.50.” The ZHR peaked at more than 150 and the radiant was determined as a = 256.9°, d = +56.6°.53 Using the orbit of periodic comet Giacobini-Zinner as representing that followed by the Draconids, K. Fox (Queen Mary College, England) projected the orbit of this stream backward and forward for 1,000 years. He found the distances between Earth and meteor stream orbits to have been too great for showers to occur in the years 950 or 2950.54 The orbit labeled “1961–1965” is from Sekanina (1970). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “2005” is from Campbell- Brown et al. (2006). The orbits labeled “21P-1946” and “21P-2012” are the orbits for periodic comet Giacobini-Zinner in 1946 and 2012, respectively.

w W (2000) i q e a 1961–1965 184.0 192.9 51.5 0.997 0.623 2.65 1968–1969 187.6 195.2 49.2 0.994 0.553 2.22 2005 167.9 195.40 30.0 0.990 0.691 3.6 21P-1946 171.81 197.00 30.72 0.9957 0.7167 3.51 21P-2012 172.59 195.39 31.91 1.0305 0.7069 3.52

Epsilon Geminids

Duration: October 10 to October 27 (l = 197°–214°) Maximum: October 18 (l = 205°) Radiant: a = 103°, d = +26° ZHR: 3

Radiant Drift: a = +0.7°, d = −0.1° V G : 69 km/s 242 11 October Meteor Showers

The fi rst instance of this shower being recognized as a fairly consistent producer of meteor activity was in 1899, when W. F. Denning listed a shower called the “Delta Geminids” in his “General Catalogue of Radiant Points of Meteoric Showers and of Fireballs and Shooting Stars observed at more than one Station.” Although the shower was listed as being active from September through January, it is obvious after examining Denning’s list that several streams were responsible for the activity— most notably, a shower was de fi nitely active shortly after mid-October. According to Denning’s article, the fi rst sighting of this shower may have been on 1868 October 19, when T. W. Backhouse (Sunderland, England) plotted six meteors from a = 100°, d = +18°. Denning had observed the shower on two occasions, the fi rst being 1879 October 15–20 ( a = 106°, d = +23°), and the second being 1887 October 14–21 (a = 105°, d = +22°). Other probable radiants were also listed, including one observed by D. Booth (Leeds, England) during 1887 October 15–20 ( a = 99°, d = +22°),55 which apparently confi rmed Denning’s observation of the same year. Since 1899, observations of this shower have occasionally appeared in the literature, but these were purely accidental observations, as no specifi c searches were carried out. During 1922 October 18, 20 and 24, J. P. M. Prentice plotted 13 very rapid meteors from an average radiant of a = 103.5°, d = +18.5°. 56 On 1932 October 25, Harvard College Observatory’s Arizona Expedition for the Study of Meteors obtained an excellent radiant determination of a = 108°, d = +25°. 57 C. Hoffmeister (Germany) was the next person to recognize an active mid- October shower in Gemini. In his classic book Meteorströme , Hoffmeister listed a shower with an average radiant of a = 101°, d = +26°. This shower had been noted on 12 occasions between 1909 and 1933, and the probable date of maximum was October 19 (l = 206°).58 This book was published in 1948, but the Epsilon Geminids again fell into obscurity. The shower was next “discovered” by R. E. McCrosky and A. Posen (1959). They identi fi ed six photographic meteor orbits from data gathered during the Harvard Meteor Project of 1952–1954. The indicated duration of activity was October 17–27, and the date of maximum was believed to be October 17. The average radiant position was a = 102°, d = +26°. 59 The shower was next observed in 1960, when it was detected by radio equipment at the Kharkov Polytechnical Institute (Ukraine). B. L. Kashcheyev and V. N. Lebedinets (1967) isolated 13 Epsilon Geminids during October 10–27. The date of the nodal passage was indicated as October 16 (l = 203°), at which time the average radiant was a = 104°, d = +25°. Interestingly, this has remained the only radio- echo survey to reveal any trace of this stream.3 V. Znojil (1968) published the results of the fi rst visual study of this meteor shower. Conducted in 1965, from Boleradice and Bohuslavice (Czech Republic), the observations were made during October 20–25, with Epsilon Geminids being detected each day. Maximum may have occurred on October 22 (though the low activity obtained by the telescopic observations made the exact date diffi cult to determine), at which time the average radiant was at a = 103°, d = +25°. The radiant’s daily motion was given as +0.7° in a and +0.2° in d . Znojil combined these Epsilon Geminids 243 observations with previous studies conducted by Hoffmeister (1948), McCrosky, and Posen (1958 & 1961), Southworth and Hawkins (1963), and Kashcheyev and Lebedinets (1967) and concluded that the shower reached maximum at a solar longitude of 204.4°. The average radiant was determined as a = 101.8°, d = +26.2°, and Znojil’s revised estimate of the radiant’s daily motion was +0.7° in a and −0.1° in d .60 Several amateur astronomers observed this meteor shower during the late 1970s and early 1980s. During 1979 October 15–28, M. T. Adams (Arizona, USA) observed 19 Epsilon Geminids in 18 h 36 min and determined the average magnitude as 3.32. He estimated that the maximum rate reached 1–3 per hour.61 R. Lunsford (California, USA) observed 11 Epsilon Geminids in 24 h during 1980 October 15–21, and noted that the average magnitude was 2.73. 62 J. Wood, director of the meteor section of the National Association of Planetary Observers (Western Australia, Australia), gives the shower’s duration as October 14–27. He concluded that a maximum rate of 1–2 meteors per hour was detected on October 20, from a = 104°, d = +26°. 63 What makes the Epsilon Geminids such an interesting stream is that it bears a strong resemblance to the Orionids, except that the argument of perihelion and ascending node are reversed by about 180°. R. B. Southworth and G. S. Hawkins (1963) pointed out that the orbit of the Epsilon Geminids was similar to the Orionid orbit, but they showed that the major differences between the orbits were in inclination (9°) and longitude of perihelion (34°).64 Znojil and J. Papousek (1968) showed that while the radiant dispersion of the Epsilon Geminids was “of the same order of magnitude as that of the radiants of the individual branches of the Orionids,” the fact that the Epsilon Geminids undergo greater planetary perturbations than the Orionids makes this stream younger. The authors concluded that a relationship between these two streams would be dif fi cult to explain.65 There is some variances in this stream’s activity. As noted earlier, the 1960 Russian study remains the only radio-echo survey to detect the Epsilon Geminids, with similar and more sensitive studies in the United States, Australia, and Canada operating during the 1960s and 2000s failing to show a trace. In fact, the activity of this stream has consistently shown signs of being irregular or periodic in nature. Five of the six photographic meteors noted earlier were actually detected in 1952. As pointed out earlier, both Denning and Booth independently observed the shower in 1887 and obtained similar radiants and durations. Finally, Hoffmeister’s 12 visual radiants were observed during 1909–1933, but four were seen during a 3-day interval in 1931. Two astronomers have made suggestions as to a possible parent for this meteor stream. J. D. Drummond (1981) suggested comet C/1964 N1 (Ikeya),66 while D. Olsson-Steel (1987) suggested comet C/1987 B1 (Nishikawa-Takamizawa-Tago). 67 Although the orbits of both comets are fairly close to the Epsilon Geminids, the orbit of C/1964 N1 does suffer differences of about 60° in both w and W , while the orbit of C/1987 B1 differs by about 30° in both w and W. Olsson-Steel did predict possible enhanced activity for the Epsilon Geminids during October 1987. An analysis of observations made by three observers during 1987 October 17–24 revealed no enhanced activity.68 244 11 October Meteor Showers

The orbit labeled “1952–1953” is from McCrosky and Posen (1959). The orbit labeled “1960” is from Kashcheyev and Lebedinets (1967).

w W (2000) i q e a 1952–1953 236.8 209.5 173.0 0.773 0.971 26.66 BL1967 223 204 175 0.88 0.75 3.58

The orbits of the two comets that have been suggested as possibly associated with the Epsilon Geminids are as follows:

w W (2000) i q e a C/1964 N1 290.76 269.95 171.92 0.822 0.985 53.51 C/1987 B1 200.40 176.01 172.23 0.870 0.996 206.87

Using an orbit similar to the photographic one above (but with a = 26.77 AU), K. Fox (1986) projected the orbit of this stream backward and forward for 1,000 years.54 This stream might have produced a meteor shower in 950, which would have reached maximum at the end of September. By 2950, a shower might be present, though maximum will likely occur at the beginning of November. The following orbits were given.

w W (2000) i q e a 950 214.0 186.3 173.3 0.80 0.97 26.55 2950 246.1 219.6 173.3 0.76 0.97 25.25

Orionids

Duration: October 11 to November 9 (l = 198°–227°) Maximum: October 22 (l = 208.9°) Radiant: a = 96°, d = +16° ZHR: 23

Radiant Drift: a = +0.8°, d = +0.12° V G : 65 km/s The Orionids are among the earliest meteor showers to be recognized as producing an annual display. The meteor stream was created by periodic comet 1P/Halley and is also responsible for the Eta Aquariid meteor shower in May. Orionids 245

Discovery

The fi rst observation of the Orionids is attributed to J. F. Benzenberg (Clausberg, Germany) and H. W. Brandes (Sesebühl, Germany). On the night of 1798 October 14/15, both men were logging meteors as part of their program to observe the same meteors from two separate locations in order to determine their heights. Benzenberg logged 33 meteors, while Brandes logged 123. Benzenberg said his numbers were low, as his assistant started to freeze and was sent home. Benzenberg logged the remaining meteors of this night by himself, which caused him to miss many. It was noted that the number of meteors detected this night was considerably higher than on the nights preceding and following.69 Another observation may have been made on the night of 1805 October 23. According to L. F. Kämtz, a large number of shooting stars were seen on this night over a large part of Germany.70 Benzenberg decided to try and observe the meteor shower again during 1837 October. He wrote, “Since it was decided that shooting stars orbit the sun, I planned to observe in the night of October 14–15.” Unfortunately, this night turned out to be “completely murky and no observation was possible;” however, Benzenberg did observe on the night of October 13, during a lunar eclipse. During 3.75 h, he saw 13 meteors, or a little over 3 per hour, which is about what could be expected on a normal night. 71 He did see higher rates on October 19, when he saw 20 meteors in 3 h. 72 This has been considered an independent discovery of the Orionids, despite the “con fi rming” observations being based on weak activity. In a letter presented to the Academy of Sciences on 1839 March 4, J. de Malbos (Berrias-et-Casteljau, Ardéche, France) said he woke up an hour before daybreak on 1838 October 18 and saw a meteor that headed eastward 20°–30°. He said another was seen three minutes later and, altogether, he saw 13 before twilight began. He wrote, “I would have liked getting up earlier in the morning, because I think many others had preceded them.”73 Despite these early observations, the discovery of the Orionid meteor shower seems attributable to E. C. Herrick (New Haven, Connecticut, USA). In a letter written to the American Journal of Science and Arts on 1838 December 24, he made the statement that October 8–15 was a “season” when “meteors may possibly be found unusually numerous.”74 Herrick commented on this activity again in 1840, when he wrote that the “precise date of the greatest meteoric frequency in October is still less defi nitely known, but it will in all probability be found to occur between the 8th and 25th of the month.”75 An independent discovery is credited to L. A. J. Quetelet (1839) when he said the October observations of 1805 and 1838 indicated a period for observers to focus their attention. Quetelet added that two potential observations also exist in ancient writings: 902 and 1202.76 246 11 October Meteor Showers

Observations

The earliest precise observations of this shower were made by A. S. Herschel (Hawkhurst, England) on 1864 October 18. Eleven meteors revealed a radiant at a = 90°, d = +16°. Herschel next observed the shower on 1865 October 20 and determined the radiant as a = 90°, d = +15°, based on 16 meteors.77 W. F. Denning (Bristol, England) made observations of the shower during 1877 October 16–19. He spotted a total of 57 Orionids during a total of 6.5 h and noted that 47 left streaks. Denning believed the maximum occurred on the morning of the 18th, when he spotted 12 Orionids in 1 h. The radiant position was given as a = 92°, d = +15°.78 The Orionids were frequently observed during the latter years of the 19th century. The radiant was generally more diffuse than some of the other annual showers, and this created a strong debate during the fi rst quarter of the twentieth century. Denning, as has been mentioned on several earlier occasions, was a strong sup- porter of the stationary radiant hypothesis, and the Orionids were considered one of his best examples. Visual studies had generally failed to detect any motion in the radiant’s position during the 10–15 days the shower was under observation each year, and Denning strongly believed that two prominent radiants were present: the Orionids at a = 91°, d = +15° and the Geminids at a = 98°, d = +14°.79 During 1913, the pages of the Monthly Notices of the Royal Astronomical Society became a forum for the pens of Denning and C. P. Olivier as the two debated the stationary character of the Orionids; however, little was resolved and the matter had to wait until 1923, when the debate was resumed in the pages of The Observatory . Based on observations made by himself and three colleagues from Leander McCormick Observatory (Virginia, USA), Olivier demonstrated how the radiant clearly moved eastward from day to day: the position for 1922 October 18 being a = 91.0°, d = +15.0°, while the October 26 position was at a = 99.2°, d = +13°. 80 The fi ve positions given by Olivier clearly indicated an advance in right ascension, but the declination actually showed no clear movement. Olivier added that recent observations by members of the American Meteor Society for the dates of October 12–31, inclusive, had also indicated motion in the right ascension, but, again, the movement in the declination was not determined. The very next issue of The Observatory contained letters by three supporters of the stationary radiant theory: Denning, J. P. M. Prentice, and A. G. Cook. Denning stated the “American observers appear to have failed to discover the minor streams, and until they can do this the real character of the chief radiant must continue to elude them, for it will be easy to make it a shifting position, and especially by the plentiful meteors radiating from 99° + 13°.”81 Prentice and Cook essentially argued in support of Denning, citing extensive observations made by themselves and other British observers. In June 1923, Olivier struck back and, as his ammunition, he stressed the importance of a photographic radiant obtained by E. S. King at Harvard College Observatory on 1922 October 20, and a series of excellent radiant determinations made by R. M. Dole between 1922 October 17 and 30. Dole essentially con fi rmed Olivier’s belief that the radiant moved and provided the following list of radiant positions: Orionids 247

Orionid radiant ephemeris Date RA (°) Dec (°) Oct. 17.9 90.7 +15.0 Oct. 18.8 91.5 +14.8 Oct. 19.8 93.4 +14.8 Oct. 21.8 93.0 +15.1 Oct. 23.8 95.9 +16.8 Oct. 24.9 99.1 +16.6 Oct. 25.8 99.6 +16.6 Oct. 26.8 100.5 +16.8

Olivier said King’s photographic radiant fell “exactly where a moving radiant would give it on Oct. 20…” with the position being determined as a = 94.1°, d = +15.8°.82 Olivier’s belief in a moving radiant gradually won out during the next few years, with several well-known amateur and professional astronomers adding support. Notably, in 1928, R. A. McIntosh conducted a very extensive set of observations during the period October 14–24, inclusive.83 Again, the movement of the right ascension was clearly demonstrated, as was the diffi culty in determining the motion of the declination. Estimates made over the last 50 years have shown that the declination actually moves slightly northward as each day passes. The 2013 International Meteor Organization’s “Meteor Shower Calendar” indicates the radiant’s daily motion as +0.8° in a and +0.12° in d . Referring back to McIntosh’s 1928 observations, he noted that 25 Orionids, or 46 %, left trains, and that the average duration of these trains was 1.3 s. His estimates of color revealed 24 % to be red and 9 % to be blue. Although his observations were frequently hampered by clouds, mist and, fi nally, the moon, McIntosh did observe on two very clear nights: the 15th and 20th. These nights possessed the highest observed rates of Orionids, with hourly totals being 8 and 6, respectively. One very unusual feature the Orionids tend to display is an unpredictable maximum. In 1981, observers reported very low rates of less than ten meteors per hour during the period of October 18–21 (maximum predicted for October 21), but high rates of near 20 per hour were noted on the morning of October 23. 84 Interestingly, a study published in Czechoslovakia during 1982 revealed the Orionids to generally possess a double maximum. The fi nding was based on observations made during 1944–1950, and the maxima occurred at solar longitude 207.8° (primary) and 209.8° (secondary).85 Shortly thereafter, several visual studies indicated the presence of a “plateau effect” or a long period of maximum devoid of any sharp decline of activity, instead of a double peak. Most notably, the 1984 observations of the Western Australia Meteor Section show a nearly fl at maximum lasting from October 21 to 24, 86 while N. W. McLeod, III, has frequently noted it to stretch up to 6 days. 87 What appears to be the best explanation of the Orionids’ irregular occurring date of maximum, was made by A. Hajduk (Astronomical Institute of the Slovak Academy of Sciences, Bratislava, Czechoslovakia) in 1970. 248 11 October Meteor Showers

Hajduk examined the reported activity of the Orionids for the period of October 14–28 during the years 1900–1967. He particularly noted that the “stream density varies along the orbit,” and “there is no fi xed periodically recurring position of maximum or secondary maxima.” Hajduk concluded that the density changes were not random and that the displacement of activity “can be explained by the presence of some fi laments along the stream orbit.”88 A strong con fi rmation of Hajduk’s fi lamentary structure was made during 1975, when radar equipment at Ondrejov and Dushanbe was simultaneously utilized during the period of October 17–29. The data was analyzed by P. B. Babadzhanova and R. P. Chebotarev (Dushanbe, Tajikistan), and Hajduk. They found radio-echo rates to slowly increase, but suddenly, at a time generally attributed as the maximum of the Orionids ( l = 208°), rates drastically declined. Just as curious was the fi nding that rates had doubled during the next 24 h and then were followed by the normal decreasing rates for every day thereafter. The authors concluded that as Earth entered the Orionid stream “we fi rst intersected a halo with a slight variation of density, then a gap corresponding to l = 208, and this was followed by a steep increase at l = 209.”89 It was claimed that this structure con fi rmed the presence of fi laments. Hajduk continued the simultaneous observations of the Orionid shower during 1978—this time combining his results at Ondrejov with those obtained by G. Cevolani (Budrio, Italy). Both stations covered the period of October 17–24; however, the Budio equipment operated until October 29. Unlike 1975, the activity curves of both stations indicated a more consistent increase towards maximum. This maximum occurred during October 21 ( l = 207.8–208.4°), with a relatively fl at peak being noted. Rates remained above one-half of maximum during October 19–22 ( l = 206.5–209.5°). The Budrio data also seems to have detected a secondary maximum on October 27 (l = 214.6°), which was explained as due to an encounter with a fi lament. The only hint of a fi lamentary structure near maximum was noted on October 20 ( l = 207.5°), when a decline in activity was noted at Ondrejov. This decline was not detected at Budrio, causing Hajduk and Cevolani to conclude that, since Ondrejov was capable of detecting fainter and, thus, smaller meteors, a region possessing fewer small particles than normal may have been encountered by Earth. 90 An interesting feature of the Orionids is the apparent complexity of the radiant. In 1939, Prentice noted two active radiants: the primary radiant, at a solar longitude of 208°, was described as being about 7° wide, centered at a = 94.4°, while the declination spread from d = 14.9° to 15.5°. A secondary radiant was noted at a = 97.8°, d = +18.2°.91 As complete as Prentice’s visual study was, a convincing confi rmation of the secondary branch had to await a 1965–1966 telescopic survey conducted in the Czech Republic. V. Znojil (1968) outlined the details of the survey and results. Telescopes with 80 mm lenses and magni fi cations of ten were used. This resulted in a fi eld of view of 7° 22’ and a limiting magnitude of 10.8. During 1965, two stations were separated by 23.91 km, while the separation was increased to 63.60 km during 1966. Znojil found two distinct radiants were present, which he referred to as the northern Orionids 249

Orionids 160

140

120

Z 100 H R 80

0 180 190 200 210 220 230 240 Solar Longitude

This represents over a decade of observations of the Orionid meteor shower. The observations were made by members of the International Meteor Organization in the 2000s and the 2010s. The solar longitude basically represents 60 days, illustrating the roughly month-long duration of the shower and several days of enhanced activity. and southern Orionids. Their average radiants were given as a = 95.4°, d = +17.8° and a = 95.6°, d = +15.9°, respectively. The latter radiant agrees very well with the position usually attributed to the Orionids, while the northern branch is very close to the position noted by Prentice 30 years earlier. Znojil’s further analysis revealed that the northern branch consistently produced fainter meteors than the southern, with the average difference amounting to 1.02 magnitudes. Both radiants exhibited a spread in right ascension amounting to 5°, while their declinations covered only 2° of the sky. 92 Observations of this meteor shower were provided by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system during 2002–2008, they detected 2536 meteors from this stream. These meteors indicated a duration from October 11 to November 9 (l = 198°–227°), which is one of the longest durations ever announced for this shower. Maximum occurred on October 21 (l = 208°) from a radiant at a = 95.5°, d = +15.2° and the daily motion of the radiant was +0.78° in a and +0.02° in d . The geocentric velocity was determined as 65.4 km/s.93

Past and Future Evolution

Studies of the evolution of the Orionid shower possess a strong interest due to the stream’s link to Halley’s comet. This link was indirectly made in 1911, when Olivier mentioned the similarity between the orbit of the Orionids and that of the Eta Aquariids of May.94 Since 1868, this latter stream was believed to be related to 250 11 October Meteor Showers comet Halley (see the Eta Aquariids in Chap. 5 ); however, this link between comet Halley and the Orionids was not considered defi nite, as pointed out by J. G. Porter in 1948. Porter considered the 0.15 AU separation between the comet’s orbit and Earth’s orbit enough of a deterrent to make a connection with the Orionids impossible.95 Although others agreed with Porter’s hypothesis, the similarity in the characteristics of the Orionid and Eta Aquarid meteors and activity rates was considered uncanny. Thus, despite the orbital distance of comet Halley at the time of the Orionid maximum, it is generally accepted that the two must be related. B. A. McIntosh and Hajduk (1983) published details of a new proposed model of the meteor stream produced by comet Halley. Using a 1981 study published by D. K. Yeomans and T. Kiang, which examined the orbit of comet Halley back to 1404 BC, 96 McIntosh and Hajduk theorized, “the meteoroids simply exist in orbits where the comet was many revolutions ago.”97 Further perturbations have acted to mold the stream into a shell-like shape containing numerous debris belts possessing stable orbits. These belts are considered as the explanation as to why both the Orionids and Eta Aquariids experience variations in activity from 1 year to the next. J. Rendtel (1990) published an analysis of the Orionid and Eta Aquariid meteor showers that calculated the number density within the two streams. He used the 1981–1986 observations by Australian groups for the Eta Aquariids and the 1984– 1987 observations by Dutch and Germany groups for the Orionids. Rentel found the Eta Aquariid number density at maximum to be 15.5−9 per cubic kilometer, while the Orionid number density at maximum was 8.85−9 per cubic kilometer. Despite the fact that the Eta Aquariids are far closer to the core of the stream caused by comet Halley than are the Orionids, the number densities were a lot closer than was expected. The number density of these streams was also less than the other major showers visible each year.98 A. Dubietis (2003) examined the long-term activity of the Orionids and Eta Aquariids. He wrote, “In general, the h -Aquarids exhibit similar structural features ( fi laments) to the Orionids. The existence of a fi lamentary structure has been justifi ed from radio…and, to some extent, from visual observations.” Examining the visual observations of the Orionids spanning 1984–2001, Dubietis stated that the population index is about r = 2.4, which is similar to the Eta Aquarids. He also pointed out that the Orionids population index reached a clear minima of 2.25 in 1993, while a clear minima was reached by the Eta Aquarids in 1992. The ZHR of the Orionids varied from 14 to 31.99

Orbit

The orbit labeled “Photo” is from B. A. Lindblad and V. Porubcan (1999) and is based on 60 “precisely reduced photographic Orionid orbits.”100 The orbit labeled “1961–1968” is from Sekanina (1970). The orbit labeled “1968–1969” is from Sekanina (1976). October Ursae Majorids 251

w W (2000) i q e a Photo 81.9 28.4 164.0 0.576 0.961 14.51 1961–1965 87.4 28.0 164.5 0.561 0.846 3.63 1968–1969 87.0 27.8 164.4 0.562 0.854 3.85 2002–2008 83.98 28.0 162.8 0.5746 0.895 5.47

Two orbits are provided for comet Halley. The orbit labeled “240 BC” is the orbit of the ﬁ rst observed apparition of this comet, which is quite close to the present orbit of the Orionids. The orbit labeled “1986” is the comet’s most recent orbit.

w W (2000) i q e a 240 BC 88.11 30.81 163.47 0.5854 0.9676 18.07 1986 111.33 58.42 162.26 0.5860 0.9671 17.83

The following two orbits were calculated by Fox (1986) for the years 950 and 2950. 54

w W (2000) i q e a 950 81.1 25.1 163.8 0.58 0.96 15.59 2950 80.5 29.2 164.0 0.57 0.96 15.17

October Ursae Majorids

This meteor shower was discovered during 2006 October 14–16, by the Japanese video meteor network SonotaCo. They noted 14 meteors were observed simultaneously from multiple stations. This allowed the radiant to be precisely determined as a = 144.8°, d = +64.5°, while the geocentric velocity was 54.1 km/s.101 Observations of this meteor shower were provided by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system during 2002–2008, they detected 1,223 meteors from this stream. These meteors indicated a duration from October 15–17 (l = 201°–203°), with maximum occurring on October 16 (l = 202°) from a radiant at a = 143.8°, d = +63.9°. The geocentric velocity was 58.1 km/s.102 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by video cameras from 1993 into 2012. Stream number 182 is based on 1,235 meteors. The duration is given as October 15–20 (l = 201°–206°), while maximum occurs on October 16 (l = 202°) from a 252 11 October Meteor Showers radiant at a = 145.8°, d = +63.8°. The radiant drift was determined as +1.5° in a and −0.8° in d per day. 103 S. Gajdos (2008) looked for past signs of this activity. He mentioned “one indis- tinct record” from 1798 October 9.7 (l = 199.4°) as a possible previous observation, when “Stars fl ew all around, next few nights too;” however, there are no details that would hint at where the meteors might have come from. He also identi fi ed fi ve photographic meteor orbits from years spanning 1953–2002, ultimately considering two of these meteors as “past members” of the October Ursae Majorid stream and another meteor as a potential member.104 After searching dozens of radiant lists published since about the middle of the nineteenth century, there only seems to be one reported radiant that is close to qualifying as a previous appearance of this meteor shower. J. P. M. Prentice (Stowmarket, England) plotted fi ve meteors from a radiant at a = 133°, d = +68° during 1922 October 13/14. He called the shower the “Sigma Ursids” and said the meteors were very rapid.105 The orbit labeled “2006” is from Uehara et al. (2006). The orbit labeled “2002– 2008” is from Brown et al. (2010).

w W (2000) i q e a 2006 163.7 202.1 99.7 0.979 0.875 5.9 2002–2008 165.74 202.0 103.3 0.9810 1.115 −8.55

1. W. F. Denning, Journal of the British Astronomical Association , 38 (1928), p. 302. 2. F. W. Wright and F. L. Whipple, Harvard College Observatory Reprints, Series 2, No. 35 (1950), pp. 1–44. 3. B. L. Kashcheyev and V. N. Lebedinets, Smithsonian Contributions to Astrophysics , 11 (1967), p. 188. 4. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 227, 229, 233, 242. 5. Z. Sekanina, Icarus , 18 (1973), pp. 257, 260. 6. Z. Sekanina, Icarus , 27 (1976), p. 288. 7. G. N. Sizonov, Solar System Research , 9 (1975), pp. 52–4. 8. J. D. Drummond, R. K. Hill, and H. A. Beebe, Astronomical Journal, 85 (1980 Apr.), pp. 496–7. 9. J. D. Drummond, Icarus , 51 (1982), pp. 656–7. 10. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 246. 11. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 200, 207, 223. 12. A. McBeath, WGN, Journal of the International Meteor Organization , 20 (1992), pp. 36–9. 13. J. Rendtel, Meteoroids and their parent bodies , Proceedings of the International Astronomical Symposium held at Smolenice, Slovakia, July 6–12, 1992, Bratislava: Astronomical Institute, Slovak Academy of Sciences, edited by J. Stohl and I.P. Williams (1993), pp. 185–8. 14. A. Dubietis and R. Arlt, WGN, Journal of the International Meteor Organization , 30 (2002), pp. 168–74. 15. R. Arlt and J. Rendtel, WGN, Journal of the International Meteor Organization , 34 (2006 Jun.), p. 80. October Ursae Majorids 253

16. J. Rendtel and S. Molau, WGN, Journal of the International Meteor Organization , 38 (2010 Oct.), pp. 161–6. 17. C. P. Olivier, Flower Observatory Reprint , No. 146 (1964), p. 14. 18. C. S. Nilsson, Australian Journal of Physics , 17 (1964 Jun.), pp. 227, 229, 233. 19. Z. Sekanina, Icarus , 27 (1976), pp. 287, 300. 20. G. Gartrell and W. G. Elford, Australian Journal of Physics , 28 (1975), pp. 597, 613. 21. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), p. 451. 22. H. Corder, Memoirs of the British Astronomical Association , 7 (1899), p. 9. 23. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923), p. 47. 24. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923), p. 38. 25. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 252. 26. http://www.imonet.org/radiants/ 27. M. Davidson, Journal of the British Astronomical Association , 25 (1915 Apr.), p. 292. 28. W. F. Denning, MNRAS , 87 (1926 Nov.), p. 104. 29. M. Davidson, Monthly Notices of the Royal Astronomical Society , 80 (1920 Jun.), pp. 739–40. 30. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 87 (1926 Nov.), pp. 104–5. 31. W. F. Denning, M. Davidson, and A. C. D. Crommelin, Monthly Notices of the Royal Astronomical Society , 87 (1926 Nov.), p. 105. 32. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 87 (1926 Nov.), pp. 104–5. 33. A. King, The Observatory , 56 (1933 Nov.), pp. 348–9; 34. A. King, The Observatory , 56 (1933 Dec.), p. 380. 35. B. S. Whitney, Flower Observatory Reprint , No. 67 (1947), pp. 29–30. 36. C. H. Cleminshaw, Publications of the Astronomical Society of the Paciﬁ c , 58 (1946 Dec.), pp. 362–3. 37. J. P. M. Prentice, The Observatory , 67 (1947), p. 3. 38. J. P. M. Prentice, Journal of the British Astronomical Association , 57 (1947), p. 86. 39. L. Kresák, Meteor News , No. 43 (1978 Oct.), pp. 4–5. 40. J. Q. Stewart, M. Ference, J. J. Slattery, and H. A. Zahl, Sky & Telescope , 6 (1947), pp. 3–5. 41. J. S. Hey, S. J. Parsons, and G. S. Stewart, Monthly Notices of the Royal Astronomical Society , 107 (1947), pp. 176–83. 42. J. A. Pierce, Physical Review (Series 2) , 71 (1947 Jan.), pp. 88–92. 43. J. G. Davies and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society , 115 (1955), p. 23. 44. J. G. Davies and A. C. B. Lovell, Monthly Notices of the Royal Astronomical Society , 115 (1955), pp. 25–6. 45. Z. Sekanina, Icarus , 13 (1970), pp. 476–7, 487. 46. Meteor News , No. 8 (1971 Oct.), p. 11. 47. B. G. Marsden, International Astronomical Union Circular , No. 2451 (1972 Oct. 16). 48. Y. Yabu, K. Watanabe, K. Nose, and Y. Takeuchi, International Astronomical Union Circular , No. 4120 (1985 Oct. 11). 49. B. A. Lindblad, ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley’s Comet. Volume 2: Dust and Nucleus (1986), pp. 229–31. 50. E. P. Bus, WGN, Journal of the International Meteor Organization , 25 (1997 Dec.), pp. 250–1. 51. M. Langbroek, WGN, Journal of the International Meteor Organization , 25 (1997 Feb.), p. 39. 52. R. Arlt, WGN, Journal of the International Meteor Organization, 26 (1998 Dec.), pp. 256–9. 53. M. Campbell-Brown, J. Vaubaillon, P. G. Brown, R. J. Weryk, and R. Arlt, Astronomy & Astrophysics , 451 (2006 May), pp. 339–44. 54. K. Fox, Asteroids, Comets, Meteors II . eds. Rickman, H., and Lagerkvist, C.-I., Uppsala: University of Uppsala (1986), pp. 523–5. 55. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 250. 56. Denning, W. F., The Observatory , 45 (1922 Dec.), p. 402. 57. E. J. Öpik, Harvard College Observatory Circular , No. 388 (1934), p. 36. 58. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 82. 254 11 October Meteor Showers

59. R. E. McCrosky and A. Posen, The Astronomical Journal , 64 (1959 Feb.), p. 26. 60. V. Znojil, Bulletin of the Astronomical Institutes of Czechoslovakia , 19 (1968), pp. 306–15. 61. M. Adams, Meteor News , No. 49 (1980 Apr.), p. 6. 62. R. Lunsford, Personal Communication (1986 Oct. 11). 63. J. Wood, Personal Communication (1985 Oct. 24). 64. R. B. Southworth and G. S. Hawkins, Smithsonian Contributions to Astrophysics , 7 (1963), p. 281. 65. V. Znojil, Bulletin of the Astronomical Institutes of Czechoslovakia , 19 (1968), pp. 314–15. 66. J. D. Drummond, International Astronomical Union Circular , No. 3610 (1981 Jun. 5). 67. D. Olsson-Steel, WGN, Journal of the International Meteor Organization , 15 (1987), pp. 109–11. 68. P. Roggemans, WGN, Journal of the International Meteor Organization , 15 (1987), pp. 188–9. 69. J. F. Benzenberg and H. W. Brandes, Versuche die Entfernung: die Geschwindigkeit und die Bahnen der Sternschnuppen zu bestimmen . Hamburg: Friedrich Perthes (1800), pp. 41–60. 70. L. A. J. Quetelet, Correspondance Mathématique et Physique de l ’Observatoire de Bruxelles , 9 (1837), p. 436. 71. J. F. Benzenberg, Die Sternschnuppen . Hamburg: Perthes, Besser, and Mauke (1839), pp. 244–5. 72. J. F. Benzenberg, Correspondance Mathématique et Physique de l ’Observatoire de Bruxelles , 10 (1838), p. 217. 73. J. de Malbos, Comptes Rendus Hebdomadaires des Séances de l ’Académie des Sciences , 8 (1839 Mar.), p. 344. 74. E. C. Herrick, The American Journal of Science and Arts , 35 (1839 Jan.), p. 366. 75. E. C. Herrick, The American Journal of Science and Arts , 39 (1840 Jul.–Sep.), p. 334. 76. L. A. J. Quetelet, Nouveaux Mémoires de l ’ Académie Royale des Science et Belles-Lettres de Bruxelles , 12 (1839), p. 23. 77. A. S. Herschel, Monthly Notices of the Royal Astronomical Society , 26 (1865 Dec.), p. 53. 78. W. F. Denning, The Observatory , 1 (1877), pp. 243–4 79. W. F. Denning, The Observatory , 41 (1918 Jan.), p. 60. 80. C. P. Olivier, The Observatory , 46 (1923 Jan.), pp. 17–18. 81. W. F. Denning, The Observatory , 46 (1923 Feb.), p. 47. 82. C. P. Olivier, The Observatory , 46 (1923 Jun.), pp. 188–9. 83. R. A. McIntosh, Monthly Notices of the Royal Astronomical Society, 90 (1929 Nov.), pp. 161–2. 84. Meteor News, No. 56 (1982 Jan.), p. 4. 85. Meteor News, No. 60 (1983 Jan.), p. 7. 86. Meteor News, No. 70 (1985 Jul.), p. 7. 87. N. W. McLeod, III, Meteor News , No. 70 (1985 Jul.), p. 4. 88. A. Hajduk, Bulletin of the Astronomical Institutes of Czechoslovakia , 21 (1970), pp. 39–40. 89. P. B. Babadzhanov, R. P. Chebotarev, and A. Hajduk, Bulletin of the Astronomical Institutes of Czechoslovakia , 30 (1979), p. 227. 90. A. Hajduk and G. Cevolani, Bulletin of the Astronomical Institutes of Czechoslovakia , 32 (1981), pp. 309–10. 91. J. P. M. Prentice, Journal of the British Astronomical Association , 49 (1939), p. 148. 92. V. Znojil, Bulletin of the Astronomical Institutes of Czechoslovakia , 19 (1968), pp. 311–12. 93. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 71–2. 94. C. P. Olivier, Transactions of the American Philosophical Society , 22 (1911). 95. A. C. B. Lovell, Meteor Astronomy , Oxford: Oxford University Press, 1954. p. 296. 96. D. K. Yeomans and T. Kiang, Monthly Notices of the Royal Astronomical Society , 197 (1981), pp. 633–46. 97. B. A. McIntosh and A. Hajduk, Monthly Notices of the Royal Astronomical Society , 205 (1983), p. 931. 98. J. Rendtel, WGN, Journal of the International Meteor Organization , 18 (1990 Apr.), pp. 63–4. 99. A. Dubietis, WGN, Journal of the International Meteor Organization, 31 (2003 May), pp. 43–6. 100. B. A. Lindblad and V. Porubcan, Meteoroids 1998, editors: W. J. Baggaley and V. Porubcan. Proceedings of the International Conference held at Tatranska Lomnica, Slovakia, August 17–21, 1998. Astronomical Institute of the Slovak Academy of Sciences (1999), p. 233 October Ursae Majorids 255

101. S. Uehara, Y. Fujiwara, T. Furukawa, H. Inoue, K. Kageyama, K. Maeda, H. Muroishi, S. Okamoto, T. Masuzawa, T. Sekiguchi, M. Shimizu, and H. Yamakawa, WGN, Journal of the International Meteor Organization , 34 (2006), pp. 157–62. 102. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 103. http://www.imonet.org/showers/shw182.html 104. S. Gajdos, Earth, Moon, and Planets , 102 (2008 Jun.), pp. 117–23. 105. J. P. M. Prentice, Memoirs of the British Astronomical Association , 24 (1924), p. 71. Chapter 12

November Meteor Showers

Andromedids (“Bielids”)

The history of the Andromedids is directly linked to the history of the remarkable periodic comet 3D/Biela. The comet was discovered on three occasions before its periodic nature became known: fi rst by J. L. Montaigne (Límoges, France) on 1772 March 8, second by J. L. Pons (Marseilles, France) on 1805 November 10, and fi nally by W. von Biela (Josephstadt, Germany) on 1826 February 27. The apparitions of 1772 and 1805 involved short observation periods of only 29 and 36 days, respectively, but during 1826, the comet was observed for 72 days, which enabled Biela to mathematically link all three apparitions and declare the discovery of a new periodic comet. The comet was successfully recovered by J. F. W. Herschel (Slough, England) on 1932 September 24.1 Comet Biela was missed at the unfavorable return of 1839, but was recovered by F. de Vico (Rome, Italy) on 1845 November 26. Although a few observations were made in the next month, interest in the comet increased following observations of two distinct nuclei. Observers reported the nuclei to slowly move away from one another and by the end of March they were separated by 14’; however, later investigations revealed the increasing separation was due to the comet’s steady approach to Earth and, in truth, the nuclei had remained about 1.6 million miles apart during the entire apparition.2 Periodic comet Biela was next observed in 1852. A. Secchi (Rome, Italy) recovered the main comet on August 26, but it was September 15 before the fi rst observations of the secondary comet were made. The somewhat unfavorable approach of the comet caused it to enter the Sun’s glare at the end of September,

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 257 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_12, © Springer Science+Business Media New York 2014 258 12 November Meteor Showers and no observations were made following the 29th. As it turned out, 1852 marked the last time observations were made of comet Biela. It was poorly placed for observation in 1859, and several months of extensive, but unsuccessful searches during the very favorable return of 1865–1866 caused astronomers to theorize that the comet had completely broken up.1 As the story on comet Biela slowly unfolded, a new meteor shower was making itself known. G. W. Krafft (St. Petersburg) observed “many shooting stars” on 1741 December 6.3 On the night of 1797 December 7, the Chinese reported that the “stars fell like rain.”4 On the evening of 1798 December 6, H. W. Brandes (Göttingen, Germany) witnessed a large display of shooting stars. He said, “I fi rst noticed them soon after the close of evening twilight, and having no other business, I kept count of the number which appeared in the small segment of the heavens which I could with convenience survey from my seat.” His counting revealed rates of about 100 per hour for four straight hours. Activity drastically declined thereafter. Brandes noted that occasional glances to other parts of the sky revealed similar quantities of meteors and he estimated “many 1,000 shooting stars must have been visible above my horizon.” 5 There does not seem to be a record of Brandes trying to observe this meteor shower in subsequent years. That same night, the Chinese reported, “a multitude of stars streamed back and forth as if weaving,” while a person in Japan wrote, “I went out to the garden and saw a myriad of large and small stars fl ying through the air, streaming north to south, east to west, as they fell like rain….at dawn, they could not be seen in the glare of the rising sun in the east.”6 During the next three decades, two additional observations were made. R. Phillips (Cape Town, South Africa) wrote about an earthquake that struck on 1809 November 30. He went on to describe the various aftershocks that were present until December 5. He then said, “Several meteors or falling stars were observed during the night of the 4th.”7 F. Raillard (France) reported an “extraordinary appearance of shooting stars” on 1830 December 7.8 E. C. Herrick (1838) mentioned Brandes’ observation of 1798 December 6 in the 1838 July-September issue of the American Journal of Science and Arts and wrote, “It is a highly interesting question, whether shooting stars do not now occur in unusual numbers on or about this day of the year, and it is earnestly to be hoped that none of our observers will suffer this period of the present year to pass without the most attentive inspection of the heavens.” 9 Herrick said Brandes’ observation was brought to his attention by E. Loomis (Western Reserve College, Hudson, Ohio, USA) in 1838 April. Herrick wrote, “Believing that phenomena of this nature result from celestial causes more or less permanent, I at once entertained strong hopes and considerable expectation that a return of this display would now be seen on or about the same period of the year.”10 Numerous observers enjoyed the Andromedid display of 1838 December, partly as a result of Herrick’s suggestion, but also because of luck. Herrick, as well as C. P. Bush, A. B. Haile, J. D. Whitney, and B. Silliman, Jr., watched the skies over New Haven (Connecticut, USA) from the 4th to the 15th. It was noted that many “large and splendid fi reballs … attended with trains” were visible on both the 6th and 7th, while on the latter date the observers noted meteors falling at a rate of Andromedids (“Bielids”) 259

28–62 per hour. Herrick uncovered additional observations from Connecticut, New York, and Georgia, and concluded that the meteors seemed to radiate “not far from Cassiopeia; or perhaps, more nearly, from the vicinity of the cluster in the sword of Perseus” at an overall rate of between 125 and 175 per hour. 11 P. Parker (Guangzhou, China) wrote, “On the fi fth of December … the falling meteors were still more abundant [than on the morning of November 14, 1838,] 100 and 60 being counted in the space of 1 h from eight and a half to nine and a half o’clock, P.M.; and a few evenings after this they were much more frequent ”. 12 J. H. Maverly (Gosport, England) wrote that on the night of the 7th, from 7:00 to 10:00 p.m., he observed 97 meteors, 56 eastward of the meridian and 51 toward the west. 13 A. Colla (Parma Observatory, Italy) observed for 3 h on the night of the 7th and observed 114 meteors.14 Another observation came from P. Flaugergues. In a note presented to the Academy of Sciences in Paris on 1839 February 18, he told of his observations made at Toulon (France) on December 6, from 8:55 to 9:15 p.m. He said he was facing Pegasus and saw 42 meteors, which seemed to have emanated from a point near the zenith. He said 31 moved through the region between the Milky Way and Pegasus, while the 11 others moved in other directions away from the zenith. The length of the trails ranged from 5° to 20°. 15 Considering the short period of time that Flaugergues observed, It can be determined that a radiant at the zenith, as seen from Toulon, would be at a = 35°, d = +43° at 8:55 p.m. and a = 40°, d = +43° at 9:15 p.m. on December 6. But the annual nature of this meteor shower also came into doubt a few years later. In a letter presented to the Royal Academy of Science in Brussels (Belgium) on 1842 December 14/15, Colla wrote that the shooting stars of December 6 and 7 were very few this year. He suggested that the idea of this meteor shower producing a large number of meteors is not correct.16 The next important observation came from E. Heis (Aachen, Germany) during 1847 December 8 and 10. He plotted 21 meteors from Andromeda on the fi rst night and 22 from Andromeda on the second night. From these plots, he determined the fi rst radiant position for this stream: a = 25°, d = +40°.17 A paper published by Heis in the Astronomische Nachrichten in 1867 again identi fi ed this radiant. Using observations from the period of 1839–1849, he gave the position as a = 21°, d = +54°. 18 The 1860s were especially important for the fi eld of meteoritics as G. V. Schiaparelli’s recognition of comet Swift-Tuttle’s production of the Perseids inspired other astronomers to seek additional comet-meteor associations.19 Early in 1867, E. Weiss (1867) 20 and H. L. d’Arrest (1867) 21 independently noted that meteor activity observed in early December of 1798 and 1838 moved in the same orbit as comet Biela. With this link being established, Biela became one of the early comets to be recognized as a meteor shower producer. D’Arrest (1867) wondered whether it was a coincidence that strong displays of this meteor shower occurred in 1798 and 1838, or exactly 40 years apart. He wondered whether a rich meteor shower should be expected 40 years after the 1838 display, or during the early days of 1878.22 Weiss (1868) approached the matter on a deeper level of mathematics than d’Arrest. He noted that J. S. Hubbard had published an in-depth series of 260 12 November Meteor Showers papers in The Astronomical Journal in 1860, which investigated the motion of comet Biela from its discovery apparition in 1772 to its 1852 apparition. Weiss took the orbits for 1772, 1826, and 1852 and calculated the theoretical radiants for the expected meteor shower. He noted that the comet’s ascending node was gradually decreasing and suggested this was because of planetary perturbations on the “meteor ring.” These calculations revealed that the date of maximum activity had changed from December 10 in 1772, to December 4 in 1826, and then to November 28 in 1852. Finally, Weiss predicted that activity might return in 1872 or 1879.23 Meanwhile, although not being immediately revealed until several years later, G. Zezioli (Italy) observed fairly weak activity from the Andromeda-Cassiopeia border on 1867 November 30. Overall, seven meteors were plotted and a radiant of a = 17°, d = +48° was revealed.24 This was the fi rst activity noted from this region since 1838; however, although it offered support to Weiss’ recognition of the shower’s maximum moving into November, this activity was in no way comparable to the activity of 1798 and 1838. Comet Biela was next predicted to arrive at perihelion in 1872, but the few searches made revealed no trace of either component; however, shortly after sunset on November 27, the pulverized remains of Biela began striking Earth’s atmosphere. P. F. Denza (Moncalieri, Italy) and three others observed about 33,400 meteors during 6 h 30 min. Around 8:00 p.m. (November 27.79) he said the display “seemed a real rain of fi re,” when meteors fell at a rate of 400 every minute and a half. 25 J. F. Anderson (Pau, France) obtained excellent meteor counts, which revealed rates of 30 per minute shortly after 6:30 p.m., which slowly increased to 36 per minute around 7:45 p.m. (November 27.78) and then declined to about 14 per minute by 10:30 p.m.26 One of the most complete of the 1872 observations came from Stonyhurst Observatory (Lancashire, England). Being aware of Weiss’ prediction of possible enhanced activity, S. J. Perry began observing after darkness had settled. As soon as he had detected notable activity he directed two assistants to aid in watching the sky. The result was a fairly accurate determination of the radiant position as a = 26.6°, d = +43.8°. It was estimated that maximum had occurred around 8:10 p.m. (November 27.84) when meteors were falling at rates too numerous to count. During the 13 min prior to 9:00 p.m. one observer counted 512 meteors, for a rate of about 40 per minute. Perry estimated that a total sky rate would then have been about 100 per minute. The character of the shower’s meteors was well established by the Stonyhurst observers as they indicated 90 % of the meteors were very faint. Perry said a typical bright Andromedid had the appearance of “a white star with a greenish-blue trail.” A peculiar feature of the shower involved the simultaneous appearance of meteors, which moved parallel to one another. For example, Perry pointed out that at 9:16 p.m. “ fi ve burst out close to g Andromedae and travelled eastward together.”27 Although Western Europe was defi nitely the best place to be for the maximum of the Andromedids in 1872, observations were also made elsewhere in the world. Most notable were the observations by H. A. Newton and others in the eastern portion of the United States. Activity was fi rst noted from the Gamma Andromedae Andromedids (“Bielids”) 261 region on November 24 when three-fourths of the 40–50 meteors seen each hour radiated from that star. On the 25th the rates were 20–25 per hour, with about half radiating from near Gamma Andromedae. Overcast skies were present on the 26th, but the storm was well observed on the 27th. Newton said a party of 2–6 observers counted 1,000 meteors between 6:38 and 7:34 p.m. (about November 28.0), with the quantity dropping to 750 in the next hour and 25 min. The meteors were described as slower than the Leonids and generally faint. Newton and A. C. Twining placed the radiant “in the line from the Pleiades to g Andromedae and 3° beyond that star” (this is computed as about a = 26°, d = +44°). Newton and Twining described the radiant as longer in a than in d , with the length not being less than 8°.28 In the years immediately following 1872, activity was totally absent from the region of Andromeda. D’Arrest’s predicted 1878 appearance of the Andromedids never took place, nor did Weiss’ possible 1879 return. Shortly thereafter, several astronomers predicted the shower would reoccur on 1885 November 27 and a last- minute reminder was published by Dun Echt Observatory a couple of weeks prior to this date. As the sun set on 1885 November 27, observers immediately became aware of exceptional activity in the sky. J. Smieton (Broughty Ferry, Scotland) fi rst began observations at 5:30 p.m. and noted meteors falling at a rate of 25 per minute. By 6:00 p.m. (November 27.75) rates had gradually increased to 100 per minute. Something curious occurred at 6:20 p.m., when “a marked decrease in the intensity of the shower was noted.” Thereafter, Smieton noted a steady increase to a peak of 70 per minute around 6:38 p.m., after which the shower steadily declined. The radiant was determined as a = 21°, d = +44°. He described the activity as consisting mainly of “shooting stars,” but a large number of meteors “had brilliant phosphorescent trains, which continued to glow for several seconds after the meteors themselves had vanished. Occasionally one of the trains would break up into fragments, and in one instance a curious spiral form was assumed.”29 W. F. Denning (Bristol, England) actually noted activity from the region of the Andromedids 24 h earlier, when rates averaged 100 per hour. But on the evening of the 27th, he declared, “meteors were falling so thickly as the night advanced that it became almost impossible to enumerate them.” He said observers with especially clear skies had rates of about one meteor every second or 3,600 every hour.30 Additional details of the 1885 Andromedids activity were revealed in the early portion of an 18-page paper written by Newton and published in the American Journal of Science and Arts in 1886 June. It appears that while some observers experiencing clear skies could not accurately count the meteors visible each minute, others gave quite consistent estimates. At Marseilles Observatory (France), E. J. M. Stephan, A. L. N. Borrelly and J. E. Coggia independently made several counts near the shower’s maximum and said the single observer rate reached 233 per minute. Observers at Palermo obtained a similar estimate of 213 per minute during one 5 min interval. Using these observations, as well as others made in Beirut and Moncalieri, Newton determined the maximum hourly rate as 75,000 under very clear skies. 31 His indicated time of maximum corresponds to November 27.76. 262 12 November Meteor Showers

Although Newton’s study produced an excellent view of the 1885 Andromedids, he went on to look at the physical characteristics of the stream, as well as how it had evolved. From the 1885 observations, he concluded the stream had an overall thickness of 200,000 miles, while “the really dense portion of the stream was less than 100,000 in breadth.” Newton commented on the perturbations the comet had experienced from Jupiter during 1794, 1831, and 1841–1842, and theorized the debris encountered by Earth in 1872 and 1885 must have left the comet after the last encounter with Jupiter, otherwise the perturbations “would have scattered the group, and we should have had a much less brilliant star-shower in 1872 and 1885.” He also con fi rmed Weiss’ 1868 discovery of the decreasing ascending node of comet Biela by showing how the actual observations of the shower in 1798, 1838, 1847, 1867, 1872, and 1885 indicated the solar longitude of the shower’s maximum had also declined from 256.2° to 245.8°—meaning the date of maximum had decreased by nearly 11 days.32 In the years immediately following 1885, the Andromedids were again nowhere to be seen, but at the next predicted passage of Biela in 1892 (the comet was again not located) observers in the United States detected a strong meteor shower. Although it was not of the caliber of the 1872 and 1885 displays, the Andromedids of 1892 November 24 did produce rates of several 100 per hour. In particular, D. Kirkwood (California, USA) observed 150 during one 30 min interval and reported “an intelligent and trustworthy young gentleman counted 350 meteors in half an hour” later in the evening. 33 Another example comes from C. D. Perrine (Alameda, California, USA), who observed 1,013 meteors during one interval of an hour and 18 min. 34 The Andromedids next reached maximum on 1899 November 24,35 and on 1904 November 21,36 with hourly rates of 100 and 20, respectively. These rates, when combined with the longer observed durations of 1899 November 23–24 and 1904 November 16–22, indicated the stream was rapidly dispersing. The shower was virtually nonexistent in the years immediately following 1904, although there were a couple of interesting possible appearances. F. W. Smith (Student’s Observatory, Swarthmore College Pennsylvania, USA) was exposing a photographic plate on 1928 November 12 and was guiding using a 5 in. refractor, which had a 1° fi eld of view. During the 102 min exposure he noted 11 meteors between magnitudes 6 and 8. He also noted the position angle of motion. C. P. Olivier wrote that as soon as these observations were reported, “it appeared to the writer that most of the meteors belong to the widely scattered remnants of the Biela stream.” Olivier plotted the meteors and noted they converged at a position of about a = 10°, d = +40°, which he noted “cannot be more than 3° out in right ascension nor more than 1° in declination, quantities too small to affect general conclusions.” He then determined a parabolic orbit from this position and commented, “The resemblance of these elements to those of Biela’s comet makes it quite certain that Mr. Smith was fortunate enough to observe and alert enough to record properly a group of telescopic meteors belonging to the Biela stream.” 37 In 1940, two apparent peaks of activity were noted: an outburst of 30 faint meteors per hour occurred on November 15, according to R. M. Dole (Cape Elizabeth, Maine, USA), while 5 per hour were detected Andromedids (“Bielids”) 263 by J. P. M. Prentice (England) during November 27-December 4.38 These two peaks inspired Prentice to theorize that the Andromedids had divided up into several components. Although visual activity seemed nonexistent following 1940, some remnants of the Andromedid stream were detected among the over 2,000 meteors photographed during the Harvard Meteor Project of the early 1950s. The fi rst of fi cial recognition of the photographic Andromedid meteors came in a paper by G. S. Hawkins, R. B. Southworth, and F. M. Stienon (1959). Isolating all November meteors detected during 1950–1956 with the right ascension ranging from 0° to 50° and the declination ranging from 0° to 50°, they compiled a list of 47 “possible Andromedids.” Noting the period of Comet Biela, the authors said associated meteors should have an atmospheric velocity of 20 km/s and, after sorting out all meteors with velocities between 19 and 21 km/s, a total of 23 meteors remained. Plotting the meteors by date of appearance, the authors noted a maximum photographic hourly rate of 1.0 was reached on November 14, and they theorized this represented a visual rate of 5 per hour. The duration of activity was given as November 2–22. The authors also examined the duration of the 1872 activity and deduced a thickness of 400,000 miles. They concluded that the failure of activity to appear in 1878 indicated the debris had then spread over less than 4 % of the comet’s orbit.39 B. G. Marsden and Z. Sekanina recalculated the orbit of 3D/Biela during 1971.40 Subsequently, L. Kresák computed the new encounter conditions between Earth and the comet’s orbit and noted that the shower’s maximum would occur 12 days earlier than in the past, or on 1971 November 17.0 [essentially confi rming the photographic maximum determined by Hawkins, Southworth and Stienon] , at which time the radiant would be at a = 26.2°, d = +24.6° [20¡ south of the nineteenth century positions] . Kresák noted that the closest approach of Earth to the comet’s orbit was 0.05 AU, while Earth remained within 0.10 AU during November 6 to December 1.41 B. A. Lindblad conducted a computerized stream search in 1971 using 865 precise meteor orbits obtained during the Harvard Meteor Project. On this occasion, Lindblad used the D-criterion calculation and revealed the Andromedids to consist of two streams.42 Two years later, however, a further investigation by A. F. Cook, Lindblad, Marsden, R. E. McCrosky, and A. Posen revealed the 1971 study to have actually placed several members of the Andromedid stream in with the Piscids of September. The subsequent 24 photographic meteors were interpreted as indicating one very complex Andromedid stream, rather than two simple branches. The authors described the existence of “a systematic trend with the longitude of the sun (i.e., with that of the earth) such that the perihelion moves out from the sun, the inclination increases, and the node and argument of perihelion vary in such a way as to keep the longitude of perihelion unchanged.”43 The average orbit based on these 24 meteors is given in the “Orbit” section below. Investigation into the photographic “Andromedids” of Cook et al. reveals the described orbital variations to be real, though it is obvious that the described transition is not smooth. A more direct explanation might be that the present Andromedid stream is composed of numerous fi laments—each of which represents a ringlet of material left by Biela during previous evolutionary changes in its orbit. 264 12 November Meteor Showers

As has already been pointed out, Biela underwent several close approaches to Jupiter and it seems likely that debris would have been left in each of the comet’s previous orbits. It will be recalled that Weiss said these Jupiter encounters meant a steady decrease in the ascending node. This has continued, so that the date of maximum gradually moved from the second week of December back to mid-November. Comparing the observed orbit of Biela in 1772, with its hypothetical orbit of 1971 (see the “Orbit” section), it will be noted that perturbations over the last 200 years have also caused a steady decrease in the inclination and perihelion distance, as well as an increase in the argument of perihelion. For meteor observers this indicates that the current Andromedid activity of November comes from the newest orbits, while that of early December comes from the oldest. More importantly, this also indicates that from November to December Earth encounters a series of ﬁ laments, the orbits of which gradually increase in perihelion distance, inclination, and ascending node, and decrease in the argument of perihelion—the same conditions noted in 1973 by Cook and his fellow researchers. The 1970s saw a resurgence of interest in the Andromedid radiant as several amateur astronomers observed weak activity. During 2 h on 1970 November 22, M. Hale (Canisteo, New York, USA) detected a rate of 1 Andromedid per hour,44 while M. Savill (Selsey, England) observed average rates of 4 per hour on November 21/22 and 23/24, 3.5 per hour on November 25/26, 1 per hour on November 26/27, and 2 per hour on December 4/5. 45 During 1971 November 12 and 14, A. Porter (Narragansett, Rhode Island, USA) observed a total of ﬁ ve meteors from this radiant, all of which were described as red and of negative magnitudes. Porter commented, “This shower suffers from an inattention it does not deserve, because many amateurs hear somewhere that it’s dead.”46 Some of the most extensive observations of this stream came from the Western Australia Meteor Section. J. Wood encouraged a survey of the Andromedid shower in 1979. Activity was noted from November 10 to 29 and a maximum ZHR of about 4 came on November 27 from a radiant of a = 28°, d = +38°.47 A total of 114 man- hours were accumulated, but only 26 Andromedid meteors were observed. The average magnitude of these meteors was 3.42, while 3.8 % left trains. The actual hourly rate peaked at 2 on November 26/27 and 1 on November 17/18. 48 Curiously, Wood’s group compiled 76 man-hours of observing time during 1981 November 13–30 and saw only three Andromedids.49 S. Molau and J. Rendtel (2009) found the Andromedids were present among 450,000 video meteors recorded over more than 10 years by the International Meteor Organization Video Meteor Network. They found that 764 of the video meteors belonged to the Andromedids, establishing a peak at November 12 ( l = 230°) and a duration extending from November 5 to 30 ( l = 223–248°). The radiant at the time of the peak was a = 22.8°, d = +31.4°, while the radiant drift was given as +0.2° in a and +0.86° in d . Molau and Rendtel noted, “… the annual Andromedids shower is a weak source which can be traced over almost a month. There is no other source interfering with the shower meteor data because of their distinct low velocity.”50 Andromedids (“Bielids”) 265

Quite unexpectedly, the Andromedids returned in 2011 from December 3 to 5. According to a paper by P. A. Wiegert, P. G. Brown, R. J. Weryk, and D. K. Wong (2013), the Canadian Meteor Orbit Radar (CMOR) detected this outburst. They said CMOR registered 122 probable Andromedids, which indicated peak activity on December 5 (l = 252.8°) from a radiant at a = 18.2°, d = +57.5°. The geocentric velocity was given as 16.2 km/s. They concluded that “predominantly small particles (~500 m m) were seen.” Wiegert et al. subsequently found a weaker shower amongst the data gathered by CMOR during 2008. The 30 detected meteors came from a radiant at a = 26.6°, d = +44.4°, which peaked on November 28 (l = 246°). The geocentric velocity was determined as 15.9 km/s. Calculations revealed that both the 2008 and 2011 outbursts were caused by the dust trail from the 1,649 perihelion passage of comet Biela.51 The ﬁ rst elliptical orbits calculated for this stream came from Hawkins, Southworth, and Stienon in 1959. They obtained two orbits using meteors photographed during 1950–1956. The ﬁ rst orbit only uses photographic meteors which possessed short trails, while the second was based on all 23 photographic meteors which had been isolated.

w W (2000) i q e a 242.7 226.2 7.5 0.777 0.732 2.90 245.4 228.8 6.3 0.783 0.728 2.88

A. F. Cook (1973) listed the following orbit for the Andromedids of 1885.52

w W (2000) i q e a 222 248 13 0.86 0.76 3.53

N. Makhmudov (1982) took Cook’s orbit and investigated the past and future orbital evolution of the Andromedids.53 Some of the results are given below:

w W (2000) i q e a 1685 207.8 264.6 20.2 0.946 0.732 3.53 1785 213.0 258.0 16.5 0.890 0.748 3.53 1885 222 248 13 0.86 0.76 3.53 1985 237.1 230.8 10.0 0.817 0.769 3.54 2085 263.3 203.8 8.4 0.798 0.774 3.53 266 12 November Meteor Showers

The orbit labeled “2011” is from Wiegert et al. (2013).

w W (2000) i q e a 2011 216.3 253.5 18.3 0.902 0.76 3.78

The following orbits are those of periodic comet 3D/Biela. The ﬁ rst two orbits represent the observed orbital extremes from the year it was discovered until it was last seen.54 The last orbit is the predicted orbit by Marsden and Sekanina for the unobserved 1971–1972 apparition.55

w W (2000) i q e a 1772 213.4 260.9 17.1 0.990 0.726 3.61 1852 223.2 248.0 12.6 0.861 0.756 3.53 1971 255.1 213.5 7.6 0.825 0.767 3.54

November Theta Aurigids

This is a newly discovered meteor shower that was ﬁ rst recognized by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system in 2002–2008, they detected 1,180 meteors from this stream. These meteors indicated a duration from November 15 to 21 (l = 233–239°), with maximum occurring on November 19 (l = 237°) from a radiant at a = 89.0°, d = +34.7°. The geocentric velocity was 33.8 km/s, while the radiant drift was determined as +1.49° in a and +0.14° in d per day.56 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by the cameras of the Video Meteor Network from 1993 into 2012. This shower appears to have been detected on several occasions. On November 17 ( l = 235.0°), 128 meteors emanated from a radiant at a = 86.5°, d = +36.0°. On November 18 (l = 236.0°), 169 meteors emanated from a radiant at a = 84.7°, d = +33.0°. On November 19 (l = 237.0°), 91 meteors emanated from a radiant at a = 91.1°, d = +33.5°. 57 The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 2002–2008 330.07 237.0 27.8 0.1160 0.897 1.13 Leonids 267

Omicron Eridanids

The discovery of this meteor shower was announced in 2009 by the Japanese video meteor network SonotaCo. In a survey spanning 2007–2008, they detected 26 meteors from a radiant at a = 60.7°, d = −1.5°. The radiant was active from November 10 to 27 ( l = 227.9°–245.0°), with the peak occurring on November 16 ( l = 234.7°). The geocentric velocity was given as 26.9 km/s, while the radiant drift was determined as +0.65° in a and −0.03° in d per day.58 The International Meteor Organization’s video meteor network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. Stream number 220 is called the “Omicron Eridanids” and is based on 935 meteors. The duration is given as November 14–29 ( l = 231– 247°), while maximum occurs on November 22 ( l = 239°) from a radiant at a = 64.0°, d = −7.5°. The radiant drift was determined as +0.8° in a and −0.0° in d per day.59 The orbits below were calculated using the radiants and velocities given by each group above.

w W (2000) i q e a SonotaCo 80.7 52.3 32.6 0.574 0.994 95.10 IMO 70.3 58.8 31.7 0.675 0.912 7.66

Leonids

Duration : November 6 to November 30 (l = 224–248°) Maximum : November 18 (l = 236.1°) Radiant : a = 154°, d = +22° ZHR : 15

Radiant Drift : a = +0.55°, d = −0.37° V G : 67 km/s The night of 1833 November 12/13 not only marks the of ﬁ cial discovery of the Leonid meteor shower, but also sparked the actual birth of meteor astronomy. Beginning around 11:00 p.m. on November 12, some astronomers noted an unusual number of meteors in the sky, but it was the early morning hours of the 13th that left the greatest impression on the people of the eastern half of North America. In the 4 h that preceded dawn, the skies were ﬁ lled with meteors.

Discovery

Several newspapers published descriptions of the spectacle on 1833 November 13. The Boston Transcript noted that between 3:30 and 4:30 a.m., “there was a war of 268 12 November Meteor Showers shooting stars in the northwest.”60 The Baltimore Gazette and Daily Advertiser printed the following: While most of our fellow-citizens were comfortably wrapt in the arms of Somnus, we beheld one of the most sublime and awful spectacles which nature can present.—At fi ve o’clock this morning the sky was perfectly serene, and not a cloud was to be seen. On a sudden the heavens became illuminated by thousands of shooting stars going in the direction of the N.W. The phenomenon lasted without intermission for nearly thirty minutes.61 Reactions to the 1833 display varied from the hysterics of the superstitious claiming Judgment Day was at hand, to the just plain excitement of the scientifi c, who estimated that a 1,000 meteors a minute emanated from the region of Leo. Newspapers of the time reveal that almost no one was left unaware of the spectacle, for if they were not awakened by the cries of excited neighbors, they were usually awakened by fl ashes of light cast into normally dark bedrooms by the fi reballs. At the time of the 1833 display, the true nature of meteors was not known for certain, but theories were abundant in the days and weeks which followed. The Charleston Courier published a story on how the sun caused gases to be released from plants recently killed by frost. These gases, the most abundant of which was believed to be hydrogen, “became ignited by electricity or phosphoric particles in the air.”62 The United States Telegraph of Washington, DC, stated, “The strong southern wind of yesterday may have brought a body of electrifi ed air, which, by the coldness of the morning, was caused to discharge its contents towards the earth.”63 The 1833 storm changed the lives of two men: D. Olmsted, a professor of Mathematics and Natural Philosophy at Yale College (Connecticut, USA), and A. C. Twining, a civil engineer in the town of West Point (New York, USA). Olmsted’s work prior to the morning of the storm was concentrated on Natural Philosophy. A two-volume book published in 1832 was titled “Introduction to Natural Philosophy” and included such topics as hydrostatics, acoustics, electricity, magnetism, and optics. The latter topic actually discussed the telescope, but that was as close as Olmsted had gotten to astronomy. Twining had gone to Yale College where he took courses in mathematics and natural sciences, to eventually become a civil engineer. A few months before seeing the storm, the American Journal of Science had published an extract of a letter written by him that was titled “On the growth of timber.” 64 Despite the early, creative attempts to explain what had happened, it was Olmsted and Twining who began wading through the reports of the night of November 12/13. Olmsted had published a request for accounts in the New Haven Daily Herald, expecting to only hear from readers of that newspaper; however, his story was reprinted in newspapers across the country and he subsequently heard from people throughout the United States. One of these accounts came from Twining. Perhaps it was the detail with which Twining described the event, which rivaled that of Olmsted, but the two men began regularly corresponding in the days following this event. Leonids 269

From Olmsted’s account, it can be seen that he was awakened by a friend at about 5:30 a.m. He wrote, “The fi rmament was unclouded; the air still and mild; the stars seemed to shine with more than their wonted brilliancy, a circumstance arising not merely from the unusually transparent state of the atmosphere, but in part no doubt from the dilated state of the pupil of the eye of the spectator, emerging from a dark room…” He continued with the following: To form some idea of the phenomenon, the reader may imagine a constant succession of fi re balls, resembling sky rockets, radiating in all directions from a point in the heavens, a few degrees south-east of the zenith, and following the arch of the sky towards the horizon. They commenced their progress at different distances from the radiating point, but their directions were uniformly such, that the lines they described, if produced upwards, would all have met in the same part of the heavens. Around this point, or imaginary radiant, was a circular space of several degrees, within which no meteors were observed. The ball, as they travelled down the vault, usually left after them a vivid streak of light, and just before they disappeared, exploded, or suddenly resolved themselves into smoke. No report or noise of any kind was observed, although we listened attentively.65 Twining began watching the event shortly after 5:00 a.m. and continued to watch until morning twilight had become too bright to follow the progression of meteors any longer. He noted that despite a very clear sky, “there was a perceptible and constant light like twilight, given out from the numerous luminous bodies which were in motion in the sky above.” He wrote the following: Of these bodies, a host of which were darting out on every side and at every altitude, the greater multitude were like stars suddenly lighted up in a state of rapid motion shooting a certain distance and gone in a second; leaving where they had passed a luminous trace, resembling commonly a fi lament of white or yellowish white cloud, of sensible breadth in the middle, but tapering to a point at each extremity like two very acute triangles united at their bases; and these luminous traces, like dissolving nebulae, gradually faded and were indiscernible after a few seconds.66 Twining did note larger meteors, which left longer lasting traces, as well as some that “created a bright fl ash like moderate or distant lightning….” He added that although it was diffi cult to count the number of meteors appearing overhead, “I should not deem it extravagant to suppose 10,000 to a single hour, during the period of my observations.” Olmsted and Twining both remarked on the area of the sky from which the meteors seem to be radiating. Olmsted noted that the radiant was in Leo, “a little westward of Gamma Leonis, and not far from Regulus.” He used a celestial globe and determined that the “radiating point” was at a = 150°, d = +20°.67 Twining wrote to Olmsted and said, “As a defi nite point, I should select as near the truth a small star in the Lion’s neck, which I fi nd on the celestial globe at the bisection of a line from e to g, and also nearly at the bisection of a line from m to h of that constellation….” 68 This star may be identi fi ed as EO Leonis, which would have been located at a = 148.4°, d = +22.7° in 1833. Olmsted spent weeks collecting eyewitness reports. Details of these reports, as well as his analysis, appeared as two large articles published in the American Journal of Science . He suggested the shower was of short duration, said it was not 270 12 November Meteor Showers seen in Europe or west of Ohio. [In fact, the meteor storm was seen by American Indians at several locations west of Ohio.] Olmsted said the meteors originated “beyond the limits of our atmosphere.” He noted that an abnormal display of meteors had also been observed in Europe and the Middle East on 1832 November 13 and in South America on 1799 November 12. Olmsted theorized that the meteors had originated from a cloud of particles in space.69, 70 With respect to the latter statement, Olmsted stated the following: We have seen that the meteors appeared to be analogous, in their constitution, to the material of which the nebulous matter of comets is composed, in all the particulars in which we can compare the two. We may be permitted, therefore, in order to avoid circumlocution, to call the body which afforded the meteoric shower, a comet, while we pursue the inquiry, whether it exhibited the other attributes of that class of bodies.71 Finally, Olmsted wrote that, “on comparing notes with Mr. Twining, I learn, that we have pursued nearly the same track of investigation, and arrived at some results similar to each other; and I am happy to share with so able a coadjutor, the responsibility of bringing them before the public.”

Meteor Storm of 1799

The birth of meteor astronomy could have begun 34 years earlier, except it seems that the right people were not inspired by the observations. The Gentleman’s Magazine and Historical Chronicle of 1799 November published an account made on the morning of 1799 November 12, by an unnamed person in Hull, England. The account states the following: This morning, between 5 and 6, the heavens exhibited an awfully grand appearance. The setting Moon became partially obscured by dark cloudy spots or streaks; in opposition to her was seen a lunar rainbow of the most beautiful varied colours; after which, the middle region of the air was illuminated by meteors, crossing each other in different directions, and leaving behind them long sparkling trains, which were visible for two or three minutes after these luminous bodies had disappeared.72 The Scots Magazine of 1799 November published an account that had appeared in the Newcastle Chronicle newspaper, describing a display that was seen at Greathem (England). The story follows: On the 12th November, several meteors or fi re balls were seen at Greathem, near Hartlepool, and other parts of that neighbourhood. They were fi rst observed between fi ve and six o’clock in an eastern direction, and continued till day-break, when they were succeeded by slight fl ashes of lightning. The general appearance was sublimely awful.73 An anonymous writer from the Bahamas sent an account dated 1799 November 26 that was published in several newspapers. He/she wrote that on the night of November 11/12, …the sky exhibited a most splendid phaenomenon, from about twelve o’clock till near sun rise, the atmosphere was one continued blaze of fi re balls, and what are commonly called Leonids 271

falling stars, fi fty at least might have been counted in the space of one minute, darting in every direction and bursting with a glare which often exceeded the brightness of the moon which was then nearly in the zenith.74 J.-J. Aymé was sailing in the Atlantic Ocean from Cayenne, French Guiana, to Europe. They had just crossed the Tropic of Cancer (latitude about 23.4° N) on 1799 November 11. On the morning of November 12, he was not able to sleep and went up to the deck. He wrote the following: The fi rmament appeared to me all on fi re, from midnight till about four o’clock in the morning. It seemed to the eye that all the stars were detaching themselves from it, in order to traverse it in different directions, pursuing and crossing each other every second, or, to speak more correctly, without intermission, and leaving behind them a long train of light, which diffused a very great brightness. The moment when the cluster of a grand fi rework has just been let off, and a great many sky-rockets thrown into the air, may afford a just idea of the state of the sky during this fi ne night.75 Aymé also noted that he had received a communication from Cayenne after he was back in Europe. This stated that the display was fi rst noticed around midnight and that at 3:15 a.m. “the sky appeared lighted by the most brilliant fi res.” The meteors were said to cross each other in every direction and “left a lively trace.” Aymé said the writer noted, “When for a few moments, the moon which then shone, was veiled by some clouds, the scene became more magnifi cent and more striking. It ceased only with the fi rst dawn of day.” A. Ellicott was conducting a survey of the Florida Keys in a small, light-built schooner. The schooner anchored at Key Largo on 1799 November 11. At about 2:00 a.m. on November 12, he wrote, I was called up to see the shooting of the stars, (as it is vulgarly termed,) the phenomenon was grand and awful, the whole heavens appeared as if illuminated with sky-rockets, fl ying in an in fi nity of directions, and I was in constant expectation of some of them falling on the vessel. They continued until put out by the light of the sun after day break. This phenomenon extended over a large portion of the West India islands, and was observed as far north as St. Mary’s, where it appeared as brilliant as with us.76 A. von Humboldt and A. Bonpland witnessed the same display from Cumana, Venezuela. Humboldt said the night of 1799 November 11 “was cool and extremely beautiful.” He added the following: Toward the morning, from half after two, the most extraordinary luminous meteors were seen toward the east. Mr. Bonpland, who had risen to enjoy the freshness of the air in the gallery, perceived them fi rst. Thousands of bolides and falling stars succeeded each other during four hours. Their direction was very regularly from north to south.77 Humboldt added that Bonpland noted, “from the beginning of the phenomenon, there was not a space in the fi rmament equal in extent to three diameters of the moon, that was not fi lled at every instant with bolides and falling stars.” He also said that many of the meteors left luminous trains that lasted 7 or 8 s. Humboldt said the display had considerably decreased by four o’clock, although some meteors were still seen “a quarter of an hour after sunrise.” 272 12 November Meteor Showers

A meteorological journal kept by missionaries was published in the Annalen der Physik and stated the following: On the 12th November we saw in Nain and Hoffenthal [Labrador, Canada] a strange appearance in the air, which greatly frightened the Eskimos. Around the daybreak, a lot of fi reballs, some of which seemed to be a half a yard in diameter, appeared in all four corners of the heavens. This phenomenon was observed at the same time at New Herrnhut and Lichtenau in Greenland.78 J. Dalton (Kendal, England) fi rst read the accounts of Ellicott and Humboldt during the winter of 1833 and wondered whether he might have observed the Leonid outburst of 1799. He checked his journal for that year and found that he wrote for November 12, “Several large meteors and much lightning in the morning from fi ve to seven o’clock.”79

Observations

The Leonids reappeared on the morning of 1834 November 13, although they were not as plentiful as in the previous year. Olmsted and Twining both noted that bright moonlight only enabled bright meteors to be seen early in the morning, but after the moon set around 4:00 a.m. fainter meteors became visible. Nevertheless, Olmsted said that from 2:15 to 5:15 a.m. he and some friends counted 155 meteors. He added that the paths of several meteors were noted and were traced backward to reveal a radiant at a = 144.5°, d = +30.25°, which he remarked was northwest of the 1,833 radiant.80 Twining said he occasionally watched from 1:00 to 2:00 a.m., noting one meteor “of considerable brightness,” but “was satisfi ed that nothing uncommon was visible at that hour, and ceased observing.” He did go back outside shortly after 4:00 a.m. and quickly noticed “an unusual number of meteors.” Twining counted 30 meteors in 25 min and said most of the meteors were “attended with trains of several minutes in breadth.”81 In the years that followed, Leonid displays continued to weaken. In 1837, H. W. M. Olbers looked at the available data, noting that Earth “went through such a dense swarm” in 1799, 1833, and maybe 1832, but a less dense region in 1831, 1834, and 1836. He suggested, “perhaps the inhabitants of Earth must now wait until 1867” before the displays of 1799 and 1833 return.82 Not much was written about the Leonids in the 1840s and 1850s; however, the interest of the astronomical world began focusing on the predicted return of the Leonids as the 1860s began. Most important was H. A. Newton’s examination of meteor showers reported during the past 2,000 years. In 1863, he identi fi ed previous Leonid returns in the years 585, 902, 1582 and 1698.83 In 1864, Newton further identifi ed ancient Leonid displays as occurring in 931, 934, 1002, 1202, 1366 and 1602. He capped this study with the determination that the Leonid period was 33.25 years and predicted the next return would actually occur on 1866 November 13/14. 84 Leonids 273

Despite Newton’s identi fi cation of a display in 585, we now know that the oldest records of a Leonid shower come from 855. Ibn al-Jawzi, an Islamic scholar in Baghdad, wrote in Al-Muntazam fi al-ta ’ rikh that in 855, “The stars were disorderly in the heavens and began to fl y east and west and arrange themselves one after another, like locusts before the beginning of the dusk, till close to the dawn. There never was anything like that except for at the event of the appearance of the Messenger of God [Muhammad].”85 Although no month or day was given, W. S. Rada and F. R. Stephenson (1992) indicated that two of the three Arab chronicles they found indicated the event occurred in 855 on Thursday night after Jamada II had begun, which indicated a date of October 17.86 The French text Annales Fuldenses contains the account of a “multitude of spikes” which traveled toward the west throughout the night on 855 October 17.87 Beginning with the work of Newton, astronomers have demonstrated how the date of maximum has steadily increased over the centuries and that October 17 is very close to the expected date for a display in 855. As the year of the predicted outburst approached, observers began noticing an increase in meteors starting in 1860. Among the observers looking at the sky on the morning of November 14 were two individuals who had a particularly strong interest in this meteor shower: Newton (New Haven) and Twining (New York, New York, USA). Newton remarked that his view was partially blocked by tall buildings, but he saw 21 meteors in the southeastern sky from 3:15 to 4:15 a.m., of which slightly less than one-fourth could be traced back to Leo. Twining watched the sky from 3:00 to 4:00 a.m. and saw eight meteors emanate from the Leo radiant in the fi rst 15 min. During the next 45 min, only one very brilliant Leonid meteor was seen. He added that the previous morning had been unfavorable for observations. 88 D. Kirkwood (Indiana State University, Indiana, USA) happened to be observing the Leonids on the morning of November 13 with a group of students. Care was taken not to count any meteor more than once. The lowest hourly rate was 45, which came during the fi rst hour of viewing, which was 10:00–11:00 p.m. on November 12. The highest rate of 90 per hour was seen from 2:00 to 3:00 a.m. on the 13th. Kirkwood wrote, “About one half of those seen after one o’clock appeared to diverge from the usual point in Leo.”89 Meteor rates steadily increased during the next few years and 1866 was eagerly awaited. Twining watched alone at New Haven on the morning of November 14. From midnight until 1:00 a.m., he saw 24 Leonids from an area 8° across that was centered at a = 147.5°, d = +24.5°. He watched again from 3:08 to 4:08 a.m. and saw 38 Leonids. 90 Other observers across the United States saw meteor totals that did not vary much from these, but while some people were disappointed that the prediction had not come true, people in Europe were seeing a sky full of stars. P. Smyth, the Astronomer Royal for Scotland, noted that the sky was “exqui- sitely clear” on the night of November 13/14. The meteors started to become more frequent around 11 p.m., with a steady increase to about 12:54 a.m., which is when he suggested the peak was actually reached. Smyth said one observer that was looking east was calling out the meteors, while an assistant recorded the times. From 12:58 to 1:58 a.m., the assistant had noted 1,492 meteors. Smyth said that during 274 12 November Meteor Showers the last half hour, another observer facing the northwest “registered rather more than half the numbers of the eastern observer.” Smyth determined that during the hour centered on 12:54 a.m., 4,626 meteors were seen. 91 E. J. Lowe (Beeston Observatory, Nottinghamshire, England) was hampered off and on by clouds. Between 9:00 p.m. and 11:00 p.m. on the 13th, he noted “six fl ashes like faint re fl ecting lightning.” Clouds again blocked the sky until about 1:20 a.m. on the 14th. He then counted 104 meteors in a minute. After this he counted 100 per minute at 1:30 a.m. and 80 per minute at 1:50 a.m. The rates had dropped to 6 per minute by 3:30 a.m.92 The majority of other observers reported hourly rates of 2000–5000. During the years that followed, the activity levels of the Leonids again decreased. The 1867 display had the misfortune of occurring with the moon above the horizon, but observers still reported rates as high as 1000 per hour, meaning the shower may have actually been stronger than in the previous year. Another strong appearance of the Leonids in 1868 reached an intensity of 1000 per hour in dark skies. After a fi nal notable display on 1869 November 14, when seven people at Port Louis Observatory (Mauritius) saw hourly rates reach 200 or more, 93 the following years were notable only due to a fairly consistent rate ranging from 10 to 15 Leonids per hour. Numerous confi dent predictions were put forth that the Leonids would next be at their best in 1899, and an early sign of returning enhanced activity was detected in 1898, when hourly rates reached 50–100 in the United States on November 14.94 What C. P. Olivier called “the worst blow ever suffered by astronomy in the eyes of the public,” was the failure of a spectacular meteor shower to appear in 1899.95 Predictions had been made, and newspapers in Europe and America made the public well aware that astronomers were predicting a major meteor storm. Although the “storm” failed to appear, the Leonids did exhibit maximum hourly rates of 40 on November 14—at least indicating some unusual activity. Later investigations revealed the stream to have experienced close encounters with both Jupiter (1898) and Saturn (1870), so that the stream’s distance from Earth in 1899 was nearly double that of the 1866 return. As it turned out, the actual peak of activity for the Leonids came on 1901 November 14/15. In the British Isles, H. Corder (Bridgwater, England), E. C. Willis (Norwich, England) and others reported hourly rates as high as 25 before morning twilight interfered.96 Several hours later, the Leonid radiant was well placed for observers in the United States, and it was apparent that the activity had increased. On the east coast, Olivier (Virginia, USA) and R. M. Dole (Massachusetts, USA) independently obtained hourly rates of 60 and 37, respectively.97 By the time the Leonids were visible over the western half of the United States, they had apparently reached their peak. At Carlton College (Minnesota, USA) it was estimated that individuals could have counted about 400 per hour. E. L. Larkin (Echo Mountain, California, USA) estimated that rates reached a maximum of 5 per minute (300 per hour). By the time the British Isles had the radiant back in view, hourly rates had apparently declined to about 20. After analyzing the available data, W. F. Denning indicated that the maximum of this shower came on November 15.98 UT.98 Leonids 275

The Leonids were barely detected in 1902, due to moonlight, but they reappeared in 1903. On November 16, Denning estimated a maximum hourly rate of 140, and said that for 15 min following 5:30 a.m. meteors were falling at 3 per minute. From plotted meteor paths, he found the radiant to have been 6° in diameter, centered at a = 151°, d = +22°.99 J. R. Henry (Dublin, Ireland) was also surprised by the intensity of the display, and he noted maximum rates near 200 per hour. Henry further noted that, at maximum, the Leonid meteors were pear-shaped and left rich trains. “Other members of the star shower dissolved in bright streaks, or made their appearance as vivid fl ashes of light....”100 Finally, A. King (Shef fi eld, England) did not begin observations until 5:57 a.m. He noted that 18 Leonids were seen in the fi rst fi ve and a half minutes, while only 16 were seen in the next half hour. King plotted ten meteors which indicated a radiant of a = 148°, d = +22°.101 From the above observations, it would seem the 1,903 maximum came on November 16.2 UT. The Leonids returned to normal in the years following 1903, with hourly rates ranging from 5 to 20. Despite having miscalculated the Leonid maximum in 1899, astronomers began to make predictions for the next return—the most likely date being 1932. Enhanced activity began early when, in 1928, maximum hourly rates reached 50 or more. During 1929, rates were lower, only 30 per hour, but moonlight was then a factor. Nevertheless, members of the American Meteor Society (AMS) made fairly extensive observations, and Olivier’s analysis revealed a radiant diameter of 5–6° and indicated the shower spanned 8–10 days.102 The Leonids began to show great strength in 1930. C. C. Wylie (Iowa City, Iowa, USA) estimated maximum hourly rates of 120 shortly before dawn on November 17. Olivier said the shower contained “many brilliant meteors with long enduring trains.”103 His analysis showed Leonids were fi rst observed on November 13/14 and last seen on the 22nd. He confi rmed that rates were “considerably over 100 per hour, despite moonlight....” 104 The 1931 display showed a slight increase over 1930, but certainly not as great as expected considering the lack of moonlight. Olivier’s analysis of AMS observations revealed rates between 130 and 190 per hour for observers in the United States during the pre-dawn hours of November 17.105 King (1932) looked at the observations he made from 1899 to 1904 and from 1920 to 1931. He noted the diameter of the radiant was generally less than 4°, and he determined a radiant ephemeris which indicated a daily motion of +1.0° in a and −0.4° in d . 106 The predicted meteor storm of 1932 was looked for with great anticipation, but it was realized that moonlight would interfere with observations. The fi rst detection of the rapid rise to maximum came at Helwan Observatory (Egypt) during the pre- dawn hours of November 17. P. A. Curry was one of seven observers keeping a lookout for the expected storm, and the greatest hourly rates reached 51; however, it should be noted that the 5 min counts showed a steady rise to nine meteors at 4 a.m.—amounting to 108 per hour—followed by a rapid decrease in numbers thereafter.107 Members of the British Astronomical Association (BAA) were best placed for maximum, which came just a few hours after the Helwan observations. J. P. M. 276 12 November Meteor Showers

Prentice obtained the highest rates of 240 per hour. 108 Unfortunately, even after taking moonlight into account, it was obvious that a meteor storm comparable to those of 1833 and 1866 did not occur. The Leonids seemed to decline slower than normal after 1932, as maximum rates remained between 30 and 40 per hour from 1933 through 1939. This meant that greater than normal activity persisted from 1928 to 1939. The previous periods of enhanced activity had been shorter, occurring during 1898–1903, 1865–1869, and 1831–1836. Throughout the 1940s and 1950s, hourly rates retained their “normal” character of 10–15 per hour. This period was highlighted by a new advance in astronomy— radar studies. The Jodrell Bank Experimental Station acquired several observations of the Leonids, with maximum observed rates being 24 in 1946, but only 3–11 from 1947 to 1953. 109 Unfortunately, due to the weakness of the Leonids in the 1950s, the increasing sophistication of the equipment still could not obtain information such as radiant positions or radiant diameters. Visual observers generally ignored the Leonids in the late 1950s, and this state of neglect caused many to completely miss the unexpected arrival of enhanced activity in 1961. D. Milon was one of fi ve amateur astronomers observing outside Houston, Texas, when 51 Leonids appeared between 3:10 and 4:10 a.m. on November 16 (about November 16.4). The next morning the greatest 1 h interval produced a rate of 54 Leonids (about November 17.4 UT), bringing the Texas group to believe maximum had probably occurred late on the 16th. Similar rates were reported elsewhere. N. D. Petersen (California, USA) commented that the Leonids were blue-white, very rapid, and often left long-enduring trains 10° in length.110 The 1962 and 1963 displays were a little above normal with hourly rates of 15–20, while the 1964 display perked up with rates of 30 per hour. In 1965, observers in Hawaii and Australia were treated to one of the best displays since 1932. From the Smithsonian tracking station at Maui (Hawaii) hourly rates were near 20 on November 16.56 but increased to about 120 by November 16.64. Meanwhile, observers at the Smithsonian tracking station at Woomera (Australia) reported 38 Leonids of an average magnitude of −3 between November 16.65 and 16.77 UT. 111 Although astronomers were still just 1 year away from the predicted Leonid maximum, optimism did not run high concerning the appearance of a meteor storm. Judging by the 1899 and 1932 returns, the stream orbit had obviously been perturbed so that a close encounter with Earth’s orbit seemed no longer possible. About as far as astronomers were willing to gamble was to say that rates would probably be greater than 100 per hour. For much of the world, this is the best that was seen, but for the western portion of the United States, it was a night to be remembered. On the night of 1966 November 17, expectations were high worldwide, but few observers got to see the Leonids as well as Milon and a dozen other amateur astronomers situated under the clear skies of Arizona. Observations began at 2:30 a.m. (November 17.35) and 33 Leonids were detected during the next hour. After a Leonids 277 short break, the next hour of observation began at 3:50 a.m., with 192 Leonids being observed. The team had been keeping magnitude estimates during the early part of the shower, but this ended around 5:00 a.m. and, by 5:10 a.m., the observers were detecting 30 meteors every minute, but the display was far from over. Rates at 5:30 a.m. were estimated as several 100 a minute, and the team estimated a peak rate of 40 per second was attained at 5:54 a.m. (November 17.50)! The activity declined thereafter, and by 6:40 a.m. it was down to 30 per minute, despite the fact that astronomical twilight had begun 9 min earlier.112 To sum up, it would seem the 1966 return of the Leonids was one of the greatest displays in history, with maximum rates being 2,400 meteors per minute or 144,000 per hour. Observers in the eastern portion of the United States did report rates of several 100 per hour, but other countries reported rates generally less than 200 per hour, since maximum had occurred during daylight. An exception was observers at a Soviet Union polar arctic station, who were able to monitor the shower at its peak. With the radiant only 8° above the horizon, the report from two observers said, “there was a continuous fl ight of meteors in a single direction, from north to south. Some appeared in the zenith and curved over the southern horizon, some appeared from the northern horizon and disappeared in the zenith, and some fl ew across the entire horizon, leaving behind a bright trail.” R. L. Khotinok’s analysis of the complete report revealed an observed maximum rate of 20,000 per hour, while a correc- tion for the low altitude gave a rate of 130,000 per hour—agreeing quite well with the Arizona observations.113 Other interesting stories came from the meteor storm of 1966. E. Cunnius (Decatur, Texas) was 6 years old and was awakened early by his mother and told to go outside. Confused, he was exiting his house and noticed his father in the middle of the yard looking into the sky. Ed looked up and saw “the sky was covered with meteors.” He added, “Facing east, I looked up into the ‘center’ of the storm where the meteors were so fast and constant it looked as if Earth were rushing through the stars.”114 What might be the most western observation of the event was made by T. Ishikawa, who was an offi cer aboard a Japanese freighter in the Pacifi c Ocean, off the coast of Baja California. He said the ship’s night watch person was watching the meteors increase as the morning progressed. They were fi nally falling at such a high rate, he began banging on the doors of the boat crew to wake everyone up. Ishikawa’s son translated the following from his father: The unobstructed view from the ship (ship usually darkens the illumination during the ocean voyage so that they can adjust to the darkness) gave the crew a spectacular view of many bright meteors. He told us that some meteors were as bright as half, or full moons and every time such meteors fl ew, the ocean surrounding the ship refl ected back the light as if it were daytime and it was a surreal experience for the crew.115 In the years following the 1966 display, hourly rates for the Leonids remained high. From 1967 through 1969, observers continued to detect rates of 100–150 per hour. After a return to normality in 1970 (15 per hour), rates jumped to 170 per hour in 1971 and 40 in 1972. The Leonids basically maintained rates of 10–15 per hour through the remainder of the 1970s and throughout the 1980s. 278 12 November Meteor Showers

In 1971 and 1972, extensive observations were made by professional and amateur astronomers in the Ukraine. The fi rst set of observations was made at Sudak and Simferopol in 1971 from November 15 to 19. Although numerous observers participated, the observations of the more experienced observers, N. V. Smirnov and Y. V. Lyzhin, were the ones evaluated. Some of the various observed aspects of the meteors included an average magnitude of 3.40 and several color estimates: green (74 %), white (20 %), blue (1 %), and orange (1 %). One of the most striking discoveries was the detection of multiple radiants. Although six radiants were determined, the most active was the long-known radiant at a = 151.7°, d = +22.9° (based on 222 plotted meteors), and the authors noted that the total plots indicated activity primarily came from an area 2.5° × 8° centered on this radiant.116 The 1972 visual survey was conducted during November 16–18, from the same locations given above. A magnitude breakdown was not given strictly for the Leonids, but for all meteors observed. The average brightness ended up as 3.01 for 576 meteors, of which 335 were Leonids. On this occasion, six radiants were again determined from plots, with the main center at a = 151.9°, d = +22.7° (based on 185 meteors).117 The radiants were generally grouped into an area about 10° across; however, it should be noted that two radiants within this area were distinctly detected in both years—one near Mu Leonis (a = 150°, d = +28°) and the other between Gamma and Eta Leonis (a = 151°, d = +17°). Interest in the Leonids was on the increase in the 1990s. The International Leonid Watch was created to pull amateur and professional astronomers together to coordinate a thorough study of the upcoming strong Leonid displays expected at the end of the twentieth century. P. G. Brown (1994) examined the period of 1988–1993 and concluded there was no trace of enhanced activity, with an average activity pro fi le for the period revealing a peak ZHR of 10 occurring on November 17/18 ( l = 235.5°); however, he announced that an enhanced display was apparently observed in 1994, despite bright moonlight. He said four observers reported 13–18 meteors per hour on November 18, which, when converted to the ZHR, indicated rates of 15–42 per hour. 118 The Leonid rates continued to increase during the next few years. The ZHR reached about 35 in 1995, 90 in 1996, 100 in 1997, and about 250 in 1998.119 The stage was set for the 1999 display, which was expected to be the biggest since 1966. As will be seen later, predictions for the 1999 display were based on an analysis of previous dust trails laid out by the parent comet of the Leonids. Maximum was expected to occur over Europe, Africa, and the Middle East on the night of November 17/18. Preparations were made months in advance, with observers in these locations and elsewhere in the world making plans to be in the best regions for observations. Perhaps the most ambitious plan was that put together by P. Jenniskens, which utilized aircraft from the National Aeronautics and Space Administration (NASA) and the United States Air Force to fl y from Israel, across the length of the Mediterranean Sea, and into the Atlantic Ocean during the predicted storm night. Named the Leonid Multi-Instrument Aircraft Campaign (Leonid MAC), it had fl own in 1998 and gathered data on the Leonid display while fl ying near Okinawa in the Paci fi c Ocean. As the Leonid MAC 99 mission boarded planes to fl y on the primary mission night of November 17/18, some noticed some bright meteors despite being in the Leonids 279 lights of Ben Gurion Airport in Tel Aviv, Israel. It was obvious a major meteor shower was already underway as cruising altitude approached. Both of the mission planes had several optical glass windows installed on both sides, which is where video cameras were set up, many with fi lters to image key wavelengths across the light spectrum. At the peak of the meteor storm it was estimated that meteors were falling at a rate of one per second. This peak happened within a few minutes of the predictions. Using a video headset that allowed me to monitor one of the cameras with a 20° × 25° fi eld of view, a two-button mouse was used to register Leonid, as well as non-Leonid meteors. The highest 5 min count for the night was 270 meteors between 01:55 and 02:00 UT on November 18! R. Arlt, L. R. Bellot Rubio, Brown, and M. Gyssens (1999) published an over- view of the 1999 Leonid display. The details were based on 277,172 meteors reported by 434 observers. They said a meteor storm occurred on November 18 at 02:02 UT ( l = 235.285°), at which time the ZHR was 3700. This was a result of Earth passing through the dust trail created by the parent comet in 1899. Another peak had occurred prior to this at 01:43 UT (l = 235.272°), which was from the 1932 dust trail.120 One particularly interesting observation was made during the 1999 display. Five observers in the United States and Mexico reported seeing and/or videotaping some fl ashes of magnitude 3–7 on the darkened portion of the Moon between 03:49 and 05:15 UT on November 18. The closest approach of the 1899 dust trail to the Moon came at 04:49 UT on November 18.121 Enhanced displays of the Leonids continued for several years after the intense 1999 display. Three maxima were detected during the 2000 display, with the peak ZHR reaching 480 when Earth passed through the 1866 dust trail on November 18.3. 122 Five different dust trails were encountered in 2001, with the highest ZHR reaching 3430 on November 18.8.123 Two dust trails were encountered on 2002, which produced similar activity levels. The fi rst trail produced a ZHR of 2510 on November 19.2, and the second produced a ZHR of 2940 on November 19.4. 124 Although predictions were published for the 2003 display, these were encounters with very old dust trails and maximum ZHRs of about 100 were predicted. Activity was noted from November 13 to 23, with several minor peaks being reported. The highest ZHR was 63 on November 19.6. 125 The last notable displays of the Leonids came in 2004, 2006, and 2009, with maximum ZHRs of 37,126 74,127 and 56,128 respectively.

Association

On 1865 December 19, E. W. L. Tempel (Marseilles, France) had discovered a 6th- magnitude, circular comet near Beta Ursae Majoris and an independent discovery was made by H. P. Tuttle (Harvard College Observatory, Massachusetts, USA) on 1866 January 6. The comet is now known as periodic comet 55P/Tempel-Tuttle. Perihelion came on 1866 January 12. The comet faded quickly thereafter and was not seen after February 9. The ﬁ rst parabolic orbit was published less than 2 weeks 280 12 November Meteor Showers

Leonids - Outburst 3000

2500

2000

Z H 1500 R

1000

500

0 233.5 234 234.5 235 235.5 236 236.5 237 Solar Longitude

The Leonid meteor shower is normally very weak, but is capable of very strong outbursts that occur whenever its parent comet returns every 33 years. This represents the Leonid outburst of 2002. Observations were made by members of the International Meteor Organization after the discovery, and the ﬁ rst elliptical orbits were published shortly after the ﬁ nal observation.129 In 1867 January, T. R. Oppolzer precisely calculated the period to be 33.17 years.130 Following the intense Leonid display of 1866 November, both G. V. Schiaparelli and U. J. J. Le Verrier independently calculated an orbit for the Leonid meteor stream, with Schiaparelli’s paper being published in 1866 November19 and Le Verrier’s being published in 1867 January.131 Following the publication of these orbits, three astronomers saw an important link. C. F. W. Peters (1867) wrote a short letter to the Astronomische Nachrichten on 1867 January 29 comparing Le Verrier’s orbit for the Leonids with Oppolzer’s orbit for comet Tempel-Tuttle. This was published on February 4.132 Schiaparelli wrote a full-page, two-column article comparing these orbits and mailed it to the Astronomische Nachrichten on 1867 February 2. It was published on February 20. 133 Oppolzer wrote a letter to the Astronomische Nachrichten on 1867 February 6 comparing the orbits calculated by Le Verrier and Schiaparelli for the Leonids with his orbit for comet Tempel-Tuttle. This was published on February 20.134 The Leonids had become the second meteor shower to be linked to a comet (after the Perseids of August).

Analysis

Although astronomers had quickly linked the outbursts of 1799 and 1833 to predict a return in 1866, J. C. Adams (1867) set out to more fully understand the timing of the Leonid returns. To do this, he used the list of “November Star Showers” Leonids 281 published by Newton (1864) in the American Journal of Science and Arts (see above), which provided about 1,000 years of Leonid observations. Adams began his work shortly after the 1866 display and used the method of C. F. Gauss to determine the amount of perturbations on the meteor stream orbit. He found that every 33.25 years, Jupiter increased the node of the Leonid orbit by 20’, Saturn increased it by 7’, and Uranus increased it by 1’, totaling an increase of 28’, which was close to the 29’ deduced by Newton from the old observations. He said this con fi rmed the 33.25-year period for the Leonids. Adams added, “In order to attain a suf fi cient degree of approximation it is requisite to break up the orbit of the meteors into a considerable number of portions, for each of which the attractions of the elliptic rings corresponding to the several disturbing planets have to be determined; hence the calculations are necessarily very long…”.135 G. Johnstone Stoney and A. M. W. Downing (1899) said the work of Adams generated an average for the planetary perturbations, but noted that there were actually “oscillations in the rate of the advance of the node….” They added that when predicting the outbursts of the Leonids, these oscillations sometimes caused the predicted date to miss the observed date by more than a day. They broke the Leonid stream into segments, with segment A representing that part of the stream that Earth encountered in 1866. After applying perturbations by Mars, Jupiter, Saturn, and Uranus, they said Earth would encounter the stream again on 1899 November 16 at 06:00 UT. As was noted earlier, there was no meteor storm in 1899, the reason being that the distance between Earth and the meteor stream was nearly double what it had been in 1866. Johnstone Stoney and Downing had not considered the separation distance of the orbits.136 They added another piece of information the week before the predicted peak, noting, “that different parts of the immensely long ortho-stream have been so variously affected by perturbations that the stream cannot now be a uniform one evenly extended along a portion of its elliptic orbit. We must accordingly recognise that it is more or less sinuous, and that, moreover, the distribution of meteors along it is uneven.”137 Following the failure of the Leonids to produce a strong display in 1899, Johnstone Stoney and Downing added another Leonid orbit segment into their calculations and basically reworked the scenario for 1898 and 1899. They found that the segment Earth passed through in 1865 missed Earth by 960,000 miles in 1898 November. The segment Earth passed through in 1866 missed Earth by 1,300,000 miles in 1899 November. They commented, “It thus appears that the displacements of the meteoric orbits which have been brought about by the perturbations of the last 33 years suffi ce to have prevented the meteoric orbit from now intersecting the earth’s orbit. This accounts for our not having had any great shower in either of the last 2 years, and unfortunately the conditions seem still more unfavourable in the present year.”138 Surprisingly, there was little in-depth analysis of the Leonids through the fi rst half of the twentieth century, with the majority of articles published about the Leonids simply providing observations. In 1959, T. Murakami examined the structure of the Leonids by using visual observations made from 1929 to 1934. The fi rst thing he did was try to equalize the observations by making corrections for seeing, 282 12 November Meteor Showers as well as the altitude of the radiant. He concluded, “that the density distribution of the meteoric particles decreases exponentially to the distance from the central line of the orbit. Also the lengthwise extension of the stream is ascertained to be considerably great.” He estimated the latter to possibly be as long as 25 AU.139 The 1966 Leonids inspired an effort to understand the mechanism behind the outbursts—an effort that would literally span the next 33-year revolution of periodic comet Tempel-Tuttle. In 1967, E. I. Kazimirchak-Polonskaya, N. A. Belyaev, I. S. Astapovich, and A. K. Terentjeva took the orbit determined for the 1866 Leonid storm and created 12 hypothetical meteor groups situated around the orbit. One of the major fi ndings was that Jupiter and Saturn were primarily responsible for altering the encounter conditions between Earth and the meteor stream. Earth itself was even found to have a strong effect on meteor bodies passing within several 1,000 km of its surface by shortening the revolution period by several years, strongly altering the eccentricity and even changing the inclination. 140 In 1972, two important papers came from the former Soviet Union. Y. V. Evdokimov and E. D. Kondrat’eva (Kazan State University, Russia) examined the Leonid meteor stream during 1822–1966. They suggested that the 1833 storm was caused by dust ejected from the comet in 1800, while the 1966 storm was caused by dust ejected in 1899—both of which would prove correct. 141 Astapovich and Terentjeva (Kiev State University, Ukraine) examined the encounter conditions between Earth and the Leonids during the period of 1898–2000. This led to predictions of high rates for 1997 November 17.85, 1998 November 18.14, 1999 November 18.42, and 2000 November 19.71.142 D. K. Yeomans (1981) mapped out the dust distribution surrounding Tempel- Tuttle by “analyzing the associated Leonid meteor shower data over the 902–1969 interval.” He noted that most of the ejected dust lagged behind the comet and was outside its orbit, which was directly opposite to the theory of outgassing and dust ejection developed to explain the comet’s deviation from “pure gravitational motion.” Yeomans suggested this indicated “that radiation pressure and planetary perturbations, rather than ejection processes, control the dynamic evolution of the Leonid particles.” Concerning the occurrence of Leonid showers, Yeomans said “signifi cant Leonid meteor showers are possible roughly 2,500 days before or after the parent comet reaches perihelion but only if the comet passes closer than 0.025 AU inside or 0.010 AU outside the Earth’s orbit.” He added that optimum conditions would be present in 1998–1999, but that the lack of uniformity in the dust particle distribution still makes a prediction of the intensity of the event uncertain. He determined that enhanced activity from the Leonids would occur on 1997 November 17.4, 1998 November 17.5, and 1999 November 17.8.143 Kondrat’eva and E. A. Reznikov (1985) calculated the orbit of comet Tempel- Tuttle during the period 1833–1966 “to investigate the contributions of particles ejected from the Comet and the Leonid meteor swarm.” They theorized that dust would be ejected from the comet in all directions as it approached perihelion and that planetary perturbations subsequently alter the orbits of the meteoroids. They found that the Earth passed 0.00039 AU from the 1899 dust trail on 1966 November Leonids 283

17.50, which matched the time of the observed storm. They predicted “intense Leonid meteor streams in the years 1999–2002.” A meteor storm was predicted for 1999 November 18.09, when Earth would again encounter the 1899 dust trail. 144 L. Kresák (1992) took the orbital integrations of comets published by A. Carusi, Kresák, and G. B. Valsecchi in 1982 and examined the Leonid outbursts that were observed from 1799 to 1966. He then predicted future meteor storms. Kresák said the fi rst storm would occur on 1997 November 17.10, with rates of 1,000 per hour. The next would occur on 1998 November 17.35, with rates of 10,000 per hour. The best year was expected to be 1999, when the Leonids would produce 100,000 per hour on November 17.60. Finally, he predicted rates of 1,000 per hour for 2000 November 16.85.145 Some of the same astronomers already mentioned above published additional papers in the next few years that examined dust trail encounters during the nineteenth and twentieth centuries, but the landmark paper that brought everything together was published by R. H. McNaught and D. J. Asher in 1999 April. McNaught and Asher said the only purpose in knowing the motion of comet Tempel-Tuttle was to recognize when dust trails were created. Thereafter, they integrated the dust trails forward and predicted the outbursts from 1798 to 2042 based on dust trails that were between 1 and 6 revolutions old. They said their model predicted the times of outbursts within a few minutes.146 In an early test of the model as the paper was being written, McNaught’s model predicted outbursts on three dates that they were having dif fi culty fi nding details about. One of these was a Leonid shower in 1869 (mentioned above). An article from the periodical Nature addressed this and after converting the local time of the observation to universal time, it came up with a peak time of 00:19 UT on November 14. This turned out to be an unbelievably perfect estimate—the model was predicting a peak at 00:24 UT on that day. 147 The McNaught-Asher model ultimately predicted encounters with fi ve different dust trails during 1999 November 18.07–18.92, with the strongest expected to be with the 1899 trail, which would be encountered on 1999 November 18 at 02:08 UT. Comparing this prediction to the observation mentioned earlier reveals a difference of only 6 min. During the next few years, slightly different models were developed and several astronomers began predicting not only Leonid outbursts, but also outbursts of other meteor showers. A new era in understanding the evolution of meteor showers had begun. It should be noted that the Leonid MAC 99 mission, as well as Leonid MAC missions during the following years, gathered a lot of data that had never been acquired before—enough to fi ll several books. This data offered new information on planetary science, atmospheric science, and even astrobiology. With respect to the latter, it was discovered that Leonid meteors began their ablation process at an altitude of about 200 km, instead of the 115–120 km that had been determined from photographic meteors. With much less atmospheric drag at the higher altitude, this meant a much lower temperature for the meteor as it began breaking up, increasing the odds of material surviving entry into the atmosphere. Cameras imaging in the mid-infrared on the Leonid MAC missions revealed that the wakes of meteors 284 12 November Meteor Showers contained carbon dioxide, water, and organic material. This indicates that it is probable for material from meteors to eventually settle to the surface of our planet. The implications for atmospheric composition, the presence of water, and the existence of life are profound. Other information gathered during these missions included details on meteoroid composition and morphology, as well as upper atmosphere winds, including gravity waves and tides.148

Orbits

The orbit labeled “1938–1965” represents an average of 12 photographic and three radio meteor orbits. The orbit labeled “1999” is from H. Betlam, P. Jenniskens, P. Spurny, G. D. van Leeuwen, K. Miskotte, C. R. Ter Kuile, P. Zarubin, and C. Angelos (2000).149 The orbit labeled “2002–2008” is from P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). 56 The orbit labeled “55P” is the orbit of comet Tempel-Tuttle during the 1998 apparition.

w W (2000) i q e a 1938–1965 173.1 236.1 161.0 0.983 0.901 9.96 1999 172.39 235.28 162.50 0.9844 0.9025 10.10 2002–2008 171.11 237.0 162.0 0.9838 0.610 2.52 55P 172.50 235.27 162.49 0.9764 0.9056 10.34

Alpha Monocerotids

Duration : November 13 to December 2 (l = 231–250°) Maximum : November 21 (l = 239.32°) Radiant : a = 117°, d = +1° ZHR : Variable

Radiant Drift : a = +0.8°, d = −0.4° V G : 65 km/s

Our present knowledge of this meteor shower is primarily based on visual observations obtained in four separate years, but the implications are that this shower is of short duration and has an orbital period of almost exactly 10 years. The actual discovery should be credited to F. T. Bradley (Crozet, Virginia, USA), who observed on the night of from 11:02 to 11:15 a.m. A 10 min break was taken to obtain star charts for plotting, but when he resumed observations at 11:25 a.m. the outburst had ended. Without having had the opportunity to plot any of the meteors, no deﬁ nite radiant could be determined, but judging by the meteors’ tendency to move from east to west, Bradley estimated the radiant was below Orion. Fortunately, C. P. Olivier had been working in the observatory at the University of Virginia that same night. He said he stepped outside for a few moments and “saw three bright meteors about 11:05 a.m. The paths of two of the meteors were Alpha Monocerotids 285

mentally noted quite accurately, the path of the third being too poorly seen, though it was parallel to that of the second.” The deduced radiant was a = 97.5°, d = +8.5°, but Olivier admitted that the position was not very accurate. After uncovering several additional reports of enhanced activity, none of which acted to shed light on the position of the radiant, Olivier concluded that the meteors “were of various colors, bright, slow, and left trains.”150 No additional activity was noted from this region until 1935 November 21.75, when M. A. R. Khan (Begumpet, India) witnessed “a fi ne shower of meteors whose radiant appeared to be near Gamma Monocerotis.” Overall, over 100 meteors were noted in the fi rst 20 min, while 11 were counted in the next 20 min.151 A few months later, Khan wrote to Olivier with a more precise radiant position of a = 110°, d = −5°, revealing that the star he indicated as Gamma Monocerotis was actually marked as Alpha Monocerotis on the American Meteor Society star charts. Olivier calculated a parabolic orbit, which is given below. The activity and radiant of the shower were apparently con fi rmed by the commanding of fi cer of the USS Canopus , which was then anchored in Manila harbor, who noted that meteors appeared about once every 30 s during one 30 min interval.152 Olivier was confi dent enough to say the strong returns of 1925 and 1935 were not only related, but pointed towards a probable return in 1945. Although he was the fi rst to point out a possible 10-year period, Olivier did not rule out the possibility of this being an annual shower whose short duration and “apparently very nar- row cross-section,” would make it easy to miss completely. He cited an American Meteor Society observation of 1904 November 19.17, as possibly representing a previous appearance (AMS radiant number 165, with a position of a = 95.4°, d = +10.9°).151 If any attempts were made to observe activity from this stream in 1945, conditions would have been very poor due to the appearance of a full moon late on November 19. Conditions would have been a little better in 1955, with full moon coming on November 29, but no apparent searches or accidental observations were made. L. Kresák (1958) examined the 1925 and 1935 events, claiming the 1935 shower represented “a unique and highly interesting example of an extremely condensed meteor stream....” Kresák estimated the maximum ZHR may have reached 2,000 per hour, which he said made it “the most conspicuous meteoric event observed in the present century, with the exception of the two richest returns of the October Draconids.” Kresák said the cometary character of the two showers was “beyond doubt,” and that their very short durations indicated a very recent departure from their parent body. In trying to determine what comet was responsible, he compared the solar longitudes of the 1925 and 1935 displays (given as 238.68° and 238.73°, respectively) and, after adding details on the theoretical orbit, he said only comet C/1943 W1 (van Gent-Peltier-Daimaca) came closest to representing the meteor stream orbit. Kresák admitted to some large discrepancies between the comet and stream orbits and concluded that if comet [C/1943 W1] was not responsible, the stream “must have been generated by a body too faint to be discovered by the present means.”153 286 12 November Meteor Showers

This region produced no notable activity in the fi ve decades following 1935, but on the night of 1985 November 21, two independent discoveries were made by observers in California (USA). The fi rst was K. Baker, night assistant at Lick Observatory. He stepped outside around 3:00 a.m. and observed 18 meteors in 7 min coming from a region near Canis Minor. The meteors were of magnitude 2–4, rapid, of short duration, and left no trains. From Capitola, R. Ducoty observed 27 meteors from 3:41 to 3:45 a.m., 5 from 3:45 to 3:49 a.m., 2 from 3:49 to 3:53 a.m., and 2 from 3:53 to 3:57 a.m. His estimate of the radiant position was a = 109°, d = −7° ± 5°. He said, “The brightest meteors were 0–−2. Their speed was quite fast, a little slower than the Leonids.”154 The 1985 radiant estimate by Ducoty provided an excellent con fi rmation of Khan’s 1935 radiant determination. Utilizing these observations, as well as the apparent 10-year period, it is possible to calculate an elliptical orbit (provided below). From this point a search was conducted through the published observations to see if other observations could be located. The earliest possible observation appears to be that of W. Doberck (Hong Kong Observatory), who managed to plot fi ve meteors from a radiant of a = 102.5°, d = −12° in 1895 from November 19 to 25. 155 R. M. Dole (East Lansing, Michigan, USA) plotted three meteors from a = 111°, d = −11.2° on 1923 November 17.8.156 C. Hoffmeister (South-West Africa, now Namibia) plotted several meteors from a = 112°, d = −10° on 1937 November 26. 157 Only Doberck’s observation satis fi es the 10-year period, but none of these observations represent outbursts. It is thus suggested that these observations might indicate the presence of activity for at least 2 years before and after the appearance of the main shower, and that the stream is wide enough to produce activity during November 17–26. M. T. Adams (1986) said Ducoty’s observation indicated a peak on 1985 November 21.49, when the solar longitude ( l) was equal to 238.62°. He said the solar longitude was in good agreement with the 1925 and 1935 displays. Adams then provided the predicted time of maximum for every year from 1900 to 2000. This included a prediction for the 1995 return, which was November 22.17. Adams wrote, “I would encourage observers to be alert for this stream in future years during the 24 h intervals centered on the predicted maxima.” He added, “I would also encourage observers to examine any meteor observations they might have made in past years which cover the indicated periods.”158 Further predictions followed, with Kresák (1993) suggesting the next outburst would occur on 1995 November 22.00, adding that observers in Africa and Europe would be most favored, 159 and P. Jenniskens (1995) predicting 1995 November 22.00–22.25. Jenniskens cited a nearly New Moon and “a similar relative position of the major planets as in 1935….” He mentioned a study by V. Guth (see Lyrids in Chap. 4 ) that suggested Lyrid outbursts “occur typically when the major planets Jupiter and Saturn are in conjunction with the stream. He [Guth] suggested that the major planets are responsible, perhaps, for density variations in the stream.” Jenniskens proposed another idea that “the planets cause perturbations of the orbits of individual particles that bring the orbits only occasionally in collision with the Earth.” 160 Alpha Monocerotids 287

The next outburst came on 1995 November 22 and was fi rst reported in International Astronomical Union Circular number 6265, which was issued the same day. The outburst was observed at several locations throughout Europe. P. Spurny and J. Borovicka (Ondrejov Observatory, Czech Republic) monitored the radiant from November 21.96 to 22.11. They said the fi rst meteor from this radiant was noted on November 22.050. They saw six or more every 2 min until November 22.067, with the highest rate of seven in 1 min coming at November 22.058. They said activity continued until November 22.098. L. R. Bellot Rubio, A. Roman, and F. Reyes (Almería, Spain) observed about 70 meteors from this radiant during November 22.055–22.071, noting that most meteors were magnitude 0–2. The radiant was determined as a = 113°, d = −3° by J. Rendtel, a = 112.5°, d = −3° by R. Haver and R. Gorelli (Frasso Sabino, Italy), and a = 116°, d = +4° by Z. A. Nagy, K. Sarenczky and I. Tepliczky (Vertes Mountain, Hungary). 161 Rendtel (1995) analyzed some of the early reported observations in the December issue of the Journal of the International Meteor Organization . He said the fi rst signs of activity started on November 22.051. The peak came on November 22.061 (l = 239.321°), when the Effective Zenithal Hourly Rate (EZHR) reached 350, while the enhanced activity remained above half this value for 27 min. Rendtel determined the population index as r = 2.51.162 Rendtel, P. G. Brown, and S. Molau (1996) provided a more extensive analysis of this outburst. They gave the duration as 01:15–01:45 UT and said the highest EZHR came during 01:25–01:30 UT, when it reached 420. The activity remained above half the maximum value for 22 min, while the population index was r = 2.36. Video observations were able to determine the radiant as a = 117°, d = +1°, which was considered the most accurate radiant ever determined for this meteor shower. The authors calculated several orbits using this radiant and velocities of 54–64 km/s [some of which are given below] . They concluded that, “an association with C/1943 W1 seems unlikely.” They added, “The 10-year periodicity suggests that the most probable origin for the stream is from a parent with a semimajor axis (a) in the interval 4.49 < a < 4.80 au. The periodic outbursts are probably associated with a return of the comet to the neighbourhood of the Earth and the Earth’s passage near the cometary nodal point close to the time of the parent’s passage…”.163 Although observers were on alert for a possible outburst in 2005, only a normal return was detected,164 indicating there is still much to learn about this meteor stream. Using a D-criterion value of 0.20 and less to compare photographic and radio meteor orbits with the computed elliptical orbit, only four orbits were revealed altogether: two photographic meteors from the Harvard Meteor Project (1952– 1954) and two radio-echo meteors from the fi rst session of the Radio Meteor Project (1961–1965). These meteors do not offer much evidence to support either the 10-year period or the short-duration, although the photographic meteors do seem to offer additional proof supporting the persistence of activity for a period of 2 years before and after the expected dates of maxima. What is interesting is that the implied duration of activity is November 13-December 2. The dates of the appearance of the meteors (as well as their radiant positions) are 1953 November 288 12 November Meteor Showers

13 ( a = 101.7°, d = −2.1°), 1954 November 26 (a = 115.4°, d = −7.4°), 1962 November 16 ( a = 109.1°, d = −5.8°), and 1963 December 2 ( a = 118.0°, d = −9.4°). Combining the meteor radiants with the visual observations of 1935, 1937 and 1985, a daily motion is found of +0.8° in a and −0.4° in d . The orbit labeled “1935” is from Olivier (1936). The orbit labeled “1953–1963” was calculated using two photographic and two radio meteor orbits acquired by surveys in the United States. The orbit labeled “P = 10” was calculated with the assumption of a 10-year period. The orbits labeled “1995–54,” “1995–59,” and “1995–64” are from Rendtel, Brown, and Molau (1996) and represent orbits based on velocities of 54, 59, and 64 km/s, respectively. The orbit labeled “C/1943 W1” is the orbit of comet van Gent-Peltier-Daimaca.

w W (2000) i q e a 1935 85.5 59.6 114.5 0.46 1.0 ϱ 1953–1963 95.7 60.1 112.3 0.464 0.941 7.83 P = 10 101.1 59.4 108.8 0.428 0.908 4.64 1995–54 126 59.3 124 0.31 0.7726 1.3 1995–59 107 59.3 130 0.40 0.8430 2.6 1995–64 90 59.3 133 0.49 1.012 ∞ C/1943 W1 33.08 58.63 136.18 0.8743 1.0 ∞

Alpha Pegasids

This meteor shower is based on very weak evidence, but is included because of an apparent association with a lost periodic comet. The Alpha Pegasids were discovered in 1959, while R. E. McCrosky and A. Posen were examining the orbits of meteors photographed during the Harvard Meteor Project of 1952–1954. Three meteors were found, all of which had been photographed on 1952 November 12 (the date had been incorrectly published as November 11). McCrosky and Posen referred to this stream as the “Mu Pegasids” and gave the average radiant as a = 340°, d = +23°.165 The orbit is as follows:

w W (2000) i q e a 199.4 230.4 8.3 0.965 0.778 4.35

McCrosky and Posen suggested an association with the lost periodic comet D/1819 W1 (Blanpain), based on the similarity of the longitude of perihelion. They Alpha Pegasids 289 said the “comet was subject to repeated perturbations by Jupiter, so it is not unrea- sonable that the nodes of the orbit of the meteor stream should be the reverse of those of the original comet orbit…” The orbit of the comet is as follows:

w W (2000) i q e a 350.26 79.81 9.11 0.8923 0.6988 2.96

B. A. Lindblad (1971) conducted a computerized stream search using 2,401 photographic meteor orbits detected during the Harvard Meteor Project. In addition to the three meteors originally found by McCrosky and Posen, two additional meteors were added: one from 1952 November 12, and one from 1953 October 29. He referred to this stream as the “Pegasids.” The ﬁ ve meteors revealed a duration of October 29-November 12 and an average radiant of a = 344°, d = +19°.166 The resulting orbit is as follows:

w W (2000) i q e a 200.2 227.7 6.8 0.966 0.718 3.51

The strongest support for this stream’s existence obviously comes from the photographic data and the suggestion of a link to comet Blanpain, but with four of the fi ve photographic meteors being detected on 1952 November 12, Lindblad suggested “caution should perhaps be exercised” when considering this stream as “regular, recurrent phenomena.”167 These words have taken on a stronger meaning with attempts to locate visual observations of this shower. Although the very fi rst observation of this radiant seems to have been made by R. de Kövesligethy (Hungary) on 1885 November 9, when fi ve meteors were plotted from a = 344°, d = +19°, 168 no trace of the radiant is present among nearly 8000 American Meteor Society radiants made from 1900 to 1984, and 5406 German observations made from 1908 to 1938 and included in C. Hoffmeister’s book, Meteorströme . Only two known observations were speci fi cally made to see this meteor shower. In 1978, N. W. McLeod, III (Florida, USA) observed only one possible meteor from this stream during nearly 26 h of observation from November 4 to 17.169 In 1980, members of the Western Australia Meteor Section observed a maximum ZHR of about 2 on November 1/2. They determined the radiant as a = 336°, d = +19°.47 The International Meteor Organization’s Video Meteor Network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras 290 12 November Meteor Showers during the period 1993–2012. A search for radiants for this shower found only two apparent radiants that could be associated with this stream. On November 8 ( l = 226°), 52 meteors emanated from a radiant at a = 344.4°, d = +27.5°. On November 9 (l = 227°), 45 meteors emanated from a radiant at a = 333.7°, d = +21.5°. On November 14 (l = 232°), 28 meteors emanated from a radiant at a = 343.8°, d = +20.0°.57

Taurids

Northern Branch Duration : October 12 to December 2 (l = 199°–250°) Maximum : November 12 (l = 230°) Radiant : a = 56°, d = +21° ZHR : 5

Radiant Drift : a = +0.78°, d = +0.19° V G : 29 km/s Southern Branch Duration: September 17 to November 27 (l = 174°–245°) Maximum: November 5 (l = 223°) Radiant: a = 52°, d = +13° ZHR: 5

Radiant Drift: a = +0.99°, d = +0.28° V G : 29 km/s

Observations of the Taurids had long revealed that this was not a particularly strong meteor shower, but discoveries in the latter half of the twentieth century revealed they were associated with several other meteor showers, minor planets, and even a comet or two. The entire group is known as the Taurid Complex. Unlike the Virginid Complex of March-April and the Scorpiid-Sagittariid Complex of May- June, the antihelion meteors seem to have less of an impact on the Taurid Complex and, as a result, several of these radiants have been discussed separately in this book. The fi rst observation of activity from the Taurids was reported by E. Heis. While analyzing the plots of meteors acquired from 1839 to 1849, he determined a number of radiant positions spanning the entire year. He noted that from November 1 to 15 there was an active radiant at a = 55°, d = +16°.170 Both branches of the Taurid meteor shower were observed in 1869 by three different observers: T. W. Backhouse (West Hendon, Sunderland, England), G. L. Tupman (Mediterranean Sea), and G. Zezioli (Bergamo, Italy). Backhouse observed 21 meteors on the night of 1869 November 6, noting that 12 came from a radiant at a = 54°, d = +16°. In addition, 4 of the 10 meteors that were seen by Backhouse on November 4 “agreed with this radiant-point.” This radiant agrees well with the Southern Taurids.171 Tupman’s observations spanned November 7–10, and he described the activity as a “rich shower with well-defi ned double radiant.” He detected both the northern and southern radiants on November 7 and 9. On the fi rst night, he plotted 6 meteors from a = 57°, d = +19.5° and 9 meteors from a = 50°, d = +14.5°. On the second night, he plotted 5 meteors from a = 59°, d = +18° and 8 meteors from a = 52°, d = +12.5°. On November 10, he plotted seven meteors from a = 53°, d = +18° and said this was an accurate radiant.172 Taurids 291

Zezioli’s radiant observation was not present in a list of his radiants published in 1871. W. F. Denning (1899) published the details in his “General Catalogue of the Radiant Points of Meteoric Showers and of Fireballs and Shooting Stars observed at more than one Station.” He indicated Zezioli recorded the paths of 11 meteors from a radiant at a = 56°, d = +23° during November 1–7. This would be an observation of the Northern Taurids.173 During the next few years, a few more observations were reported. An observer at the Royal Observatory (Greenwich, England) reported seeing meteors radiate from a = 55°, d = +25° on 1870 November 13.174 From 1872 November 1 to 3, Tupman detected a radiant at a = 56°, d = +23°.172 In an article by R. P. Greg (1875), radiant lists by Heis, G. V. Schiaparelli, Zezioli, Tupman, Schmidt, the British Association Reports, and “private sources” were collated into a master list of 187 radiants. Radiant 156 was said to be a “well- marked shower, with radiant at a Tauri.” He added, “The meteors of this shower may be called ‘Taurids .’” The included observations spanned October 25 to November 15, which were from a radiant at a = 64°, d = +18°.175 Additional Northern Taurid radiants were reported during the remainder of the nineteenth century. Among a list of radiant points detected from 1876 to 1879, H. Corder (Writtle, Essex, England) detected a radiant at a = 59°, d = +20° from November 7 to 10. He remarked, “Always interesting; slow meteors.”176 Denning (Bristol, England) plotted 14 “Taurids” from a radiant at a = 62°, d = +21° on 1879 November 12 and 11 more from a radiant at a = 58°, d = +21° from 1879 November 13 to 14. 177 A Southern Taurid radiant was noted by Denning (1884) in a paper on fi reball radiants. Designated shower number “XXXII”, it was active from November 5 to 8 from a radiant at a = 58°, d = +16°.178 Denning (1890) reported seeing more radiants from this region. From 1876 November 7 to 8, he recorded 3 “not swift, bright” meteors from a = 58°, d = +16°. From 1877 November 1 to 7, he recorded 9 “slowish” meteors from a = 57°, d = +18°. From 1879 November 13 to 14, he recorded 11 “slow” meteors from a = 58°, d = +21°. Other nearby radiants were recorded as early as 1872, which might also be associated with the Taurids.179 Despite the fact that Taurid radiants were reported almost every year during the next two decades, especially in the Memoirs of the British Astronomical Association , A. King (1918) announced the existence of a new meteor shower. His interest was sparked by the observation of six meteors by T. F. Cranidge and himself within 24 min on 1918 November 12. King said the hourly rate for two observers would have been 15, but correcting for bright moonlight would have made this much higher. One additional meteor was seen later in the evening, and King’s analysis of the seven plots revealed a radiant of a = 54°, d = +24°. King searched for previous appearances of this radiant and announced a duration extending from August to December; however, half of the radiants he uncovered occurred during the fi rst half of November.180 The Southern Taurids were fi rst discussed in depth in 1920. Denning pointed out that the majority of the “considerable number of fi reballs” which appeared in early November of 1920 came from a Taurid shower at a = 59°, d = +12°. He said he had 292 12 November Meteor Showers noted the radiant “to have been very active on 1886 November 2–3, when 17 of its meteors were seen at Bristol, and they indicated a diffused radiant situated a few degrees west of the Hyades.”181 In the years following 1920, observations of both radiants were fairly abundant, though both were rarely seen by the same observer in the same year. For example, J. P. M. Prentice plotted ten Northern Taurids from a radiant of a = 60°, d = +22° from 1921 November 8 to 10 (this observation was even confi rmed by A. G. Cook, who plotted 11 meteors from a = 63°, d = +22° during November 6–10)182 ; however, he detected strong Southern Taurid activity in 1922 on November 13 and 15, from a = 53°, d = +14° 183 and in 1923 from November 2 to 17, from a = 54.8°, d = +11.6°184 . In a 1924 article briefl y discussing the Taurid radiants, Denning pointed out that the Southern Taurids (referred to as the Lambda Taurids) exhibited “marked variation in strength in different years.”185 F. L. Whipple (1940) commented that the “multiplicity of radiants, the uniformity and the long endurance of the Taurid stream of meteors have disguised its character as one of the more important known showers.”186 Indeed, today’s Taurids seem almost lost amidst a collection of strong showers producing activity during the months of October and November. But such was not always the case. I. S. Astapovich and A. K. Terentjeva (1968) conducted a study of fi reballs appearing between the fi rst and fi fteenth centuries and revealed the Taurids to have been “the most powerful shower of the year in the eleventh century (with 42 fi reballs belonging to them) and no shower, not even the great ones, could be compared with them as to activity.” The authors said both branches of the stream were active: the Northern Taurids possessed a duration of October 20-November 18, with an average radiant of a = 56°, d = +24°, while the Southern Taurids had a duration of October 25-November 17 and an average radiant of a = 54°, d = +8°. The northern stream was the strongest of the two branches and exhibited a radiant measuring 6° × 1°. The southern shower was only half as active as the northern and exhibited a radiant 3° in diameter.187 The existence of the Taurid streams cannot be accounted for between the 11th and 19th centuries. In the midst of an ambitious study of 5,406 visual radiants, Hoffmeister reexam- ined the Taurids in his 1948 book Meteorströme . He failed to recognize the Southern Taurids, but he uncovered 91 radiants representing the Northern Taurids. He indicated the stream’s duration extended from September 27-December 10 ( l = 183.6°–256.9°), with the radiant steadily moving from a = 27.2°, d = +16.8° to a = 78.8°, d = +20.0°. Maximum activity was represented by 16 radiants and fell on November 4 ( l = 221.9°), when the radiant was at a = 51.1°, d = +21.8°.188 [Note that on page 82 of Hoffmeister ’ s book, there is a radiant matching the general description of the Southern Taurids. It was based on only four visual observations and occurred on November 3 from a = 57¡, d = +8¡.] Although observers and researchers tended to agree with the notion that the region of Taurus and Aries contained several active radiants in October and November, it was the photographic analysis of F. W. Wright and Whipple that made the fi rst elaborate attempt to isolate these. Altogether they found four radiants: Northern Taurids, Southern Taurids, Northern Arietids, and Southern Arietids. The Taurids 293 two Arietids streams were not well represented in the data, and the authors contemplated that the southern branch might form a continuous stream with the Southern Taurids. Wright and Whipple’s analysis of the two Taurid streams was quite complete. They found 49 double-station and single-station photographic meteors, which represented the Southern Taurids. These indicated a duration extending from October 26 to November 28, and a radiant moving from a = 46.9°, d = +13.4° to a = 67.0°, d = +16.3°. The mean date of photographic activity came on November 8.69, at which time the radiant was at a = 55.2°, d = +14.5°. The 24 double-station and single-station meteors representing the Northern Taurids revealed a duration of October 17-December 1, with the radiant moving from a = 44.6°, d = +19.0° to a = 67.5°, d = 24.5°. The mean date of photographic activity came on November 10.72 from a radiant of a = 56.9°, d = +22.4°. The authors said the hourly rate of the Southern Taurids seemed to rise abruptly to an early November maximum, slowly decline, and then rise again to a secondary maximum on November 11, while the Northern Taurids showed only a fl at maximum around mid-November. They concluded that the differences and character of the activity of the two streams indicated the Southern Taurids were less diffuse than the Northern Taurids and, therefore, may have developed more recently.189 Other photographic surveys were conducted during the 1950s and 1960s by astronomers in both the United States and the Soviet Union. The subsequent analyses of these photographic meteor orbits tended to reveal similar orbital details, but the utilization of fewer meteors did not allow a determination of the radiant, date of maximum and daily motion that could compare with that of Wright and Whipple. The double-station photographic orbits obtained from all of these surveys were combined to produce orbits for both Taurid streams (see “Orbit” section); however, the data is still inadequate to enable an accurate determination of even the date of maximum. The reason for this is that photographic Taurids are in greater abundance in October than in November. Whether this is due to mass distribution within the streams or just an inadequate use of cameras during November cannot be determined at this time. It is, however, possible to determine the daily motion of both Taurid radiants, with values of +0.78° in a and +0.19° in d being determined for the northern stream, and +0.99° in a and +0.28° in d being determined for the southern stream. Radio-echo studies became a powerful addition to the arsenal of data available to astronomers in the mid-1940s. Unfortunately, even the best equipment then available, which was located at the Jodrell Bank Experimental Station, possessed a resolution so low it was impossible to separate the two Taurid streams. Thus, from 1946 to 1950 radio-echo details revealed only a general picture of the Taurid shower. For 1946 and 1947, not even a radiant could be determined, but radio-echo rates of 18 per hour were detected on November 9 of the former year, while rates reached 9 per hour on November 6 of the latter year. In 1950, 109 echoes were detected on November 9, which revealed a radiant of a = 55°, d = +25°. The maximum hourly rate reached 14.190 294 12 November Meteor Showers

From 1951 to 1953, the Jodrell Bank survey obtained four radiant determinations. In 1951, 57 echoes detected on November 7, revealed a 4°-diameter radiant of a = 61°, d = +25°, while the maximum hourly rate reached 25. Two radiants were detected in 1952. The fi rst was a 3°-diameter radiant located at a = 52°, d = +24° on November 5, while the second was a 6°-diameter radiant located at a = 59°, d = +17° on November 10. The maximum hourly rates attained 7 and 14, respectively. In 1953, a 3°-diameter radiant was detected at a = 58°, d = +25° on November 9. The maximum hourly rate reached 8.191 The additional survey years of 1954–1958 closely re fl ected the results obtained from 1950 to 1953. As the 1960s began, radio equipment was set up in other areas of the world that would provide more information about the Taurids—equipment which was more sensitive than that at Jodrell Bank. For the fi rst time, astronomers had the means to precisely detect meteors at magnitudes fainter than what photographic methods offered. In 1960, B. L. Kashcheyev and V. N. Lebedinets (Kharkov Polytechnical Institute, Ukraine) succeeded in splitting the Taurids into two distinct streams, despite the fact that the equipment did not operate beyond October 23. Southern Taurids were detected from September 20-October 22, during which time 73 meteors were detected from an average radiant of a = 27.2°, d = +8.6°. The Northern Taurids were detected from October 11 to 23, during which time 13 meteors were detected from an average radiant of a = 33.5°, d = +18.2°. The authors determined orbits for each stream based on velocity measurements, and concluded that both streams were in good agreement with the orbits determined by photographic methods. The next step in the evolution of radio equipment took meteor detection far below naked-eye visibility, thus detecting meteors far smaller than could be detected by previous surveys. The Radio Meteor Project operated from Havana, Illinois (USA) during two different periods: 1961–1965 and 1968–1969. Z. Sekanina (1970) analyzed the data and wrote, “The gap between the two branches, so striking in the case of bright photographic meteors, is no longer seen in the radio sample. Also, the radio Taurids appearing on the same day as the bright photographic Taurids have their radiants, on an average, shifted eastward.” Sekanina said the most notable difference in the orbital elements was in the longitude of perihelion, which varied from the photographic orbits by nearly 10°. He concluded that the separation between the photographic and radio data “may suggest a difference in the mean age between the two groups of meteors.”192 With observations of both Taurid radiants becoming more numerous as the twentieth century progressed, certain facts about the streams became known. Two of the most notable characteristics were the long durations and the slow daily motion of each stream’s radiant. This led to the 1930s conclusions of O. H. J. Knopf 193 and C. Hoffmeister 194 that the Taurids were of interstellar origin rather than a product of the solar system. This conclusion was challenged in 1940, when Whipple published a list of 14 photographic meteors detected by the northern stations of Harvard Observatory from 1937 to 1938. Orbits were computed for six of the meteors simultaneously photographed by two cameras, and this allowed Whipple to discover that the Taurids possessed unusually short periods. He concluded that the semimajor axis, Taurids 295

Northern Taurids 50

30 Z H 25 R 20

0 180 190 200 210 220 230 240 Solar Longitude

This represents observations of the Northern Taurid meteor shower. The observations were made by members of the International Meteor Organization from 2007 to 2009. The shower spans about 60 days and the graph illustrates the variable activity of 1–5 per hour throughout the entire period

Southern Taurids 50

30 Z H 25 R 20

0 180 190 200 210 220 230 240 Solar Longitude

This represents observations of the Southern Taurid meteor shower. The observations were made by members of the International Meteor Organization from 2007 to 2009. The shower spans about 60 days and the graph illustrates the broad peak in early November eccentricity and longitude of perihelion all pointed to a possible association with periodic comet Encke, and that the observed 10–15° difference in the planes of the meteor orbits and the comet could be explained as the result of 14,000 years’ worth of perturbations from Jupiter.195 296 12 November Meteor Showers

Whipple and S. E. Hamid (1950) took a more in-depth look at the evolution of the Taurids. They calculated the effects of secular perturbations by Jupiter on the orbital inclination and longitude of perihelion of nine photographic meteor orbits and found the orbital planes of four of the meteors coincided with that of comet Encke 4,700 years ago. Three other orbits coincided with one another, but not with comet Encke 1,500 years ago. The authors theorized “that the Taurid streams were formed chie fl y by a violent ejection of material from Encke’s Comet some 4,700 years ago, but also by another ejection some 1,500 years ago, from a body moving in an orbit of similar shape and longitude of perihelion but somewhat greater aphelion distance....” It was suggested that this unknown body had separated from Encke sometime in the past.196 Whipple’s 1940 paper discussed more than the Taurids and their link to comet Encke. Whipple said the stream’s apparent spread of 0.2 AU meant Mercury, Venus, and Mars were also likely to encounter it. He also noted that the stream could produce a post-perihelion shower for Earth, which would occur in late June and early July during daylight.197 Of course, it will be some time before the “Taurids” of Mercury, Venus, and Mars are confi rmed, but in 1951, M. Almond computed orbits for the daylight streams discovered at Jodrell Bank and found the Beta Taurids of June to be very similar to the Northern Taurids.198 The subject of Taurid fi reballs was revisited by K. B. Hindley (1972). He said the meteor section of the British Astronomical Association compiled a catalog of 1,700 bright fi reballs that had been investigated since 1676. A total of 83 fi reballs were visible within a 15°-diameter area from September 20-December 20. The average radiant was determined as a = 55.9°, d = +18.9°, while the radiant drift was given as +0.79° in a and +0.18° in d. The period of activity extended from October 13-December 2 (l = 200–250°) and the maximum came on November 8 (l = 225°). Hindley noted, “As one might expect, the fi reball scatter is considerably greater [than the photographic scatter]—mainly due to errors of observation, and the two branches have become diffuse by these to overlap.” Nevertheless, he said it was possible to separate the two branches. What he found was, “Taurid activity comes mainly from the northern branch of the stream, whilst after l = 215°, the northern activity actually falls and the southern branch suddenly becomes very active. Consequently, at the time of Taurid maximum, the bulk of the activity comes from the southern radiant. Shortly after l = 230°, however, the southern radiant suddenly decreases in activity and the northern one again becomes prominent.” 199 D. I. Steel, D. J. Asher, and S. V. M. Clube (1991) examined the structure and evolution of the Taurid Complex. Beginning with a selection process that pulled 313 probable core members of this stream from a database of about 68,000 total meteor orbits, they plotted the orbital details “to see whether there are any indica- tors as to the origin and evolution of the complex.” The main things they noted were the following: • There was a “great deal of scatter” among the individual elements. • There is a “general increase” of the semimajor axis (a) with the ascending note (W ). Taurids 297

• The “radar orbits are smaller than the optical orbits, as would be expected if the Poynting-Robertson effect had time to operate by any signi fi cant amount.” • “There is evidence for clustering in the (a, W ) plots.” • “The perihelion distances show a general increase with W .” • There is some clustering noted among the Northern Taurids and Southern Taurids. Ultimately, Steel et al. “modeled the Taurid Complex as resulting from the decay and disintegration of a very large progenitor, with the meteoroid orbits being dispersed by planetary perturbations over a time-scale of” 10,000 years. They added, “we fi nd from our integrations that there are epochs of large infl ux to the Earth which last for several 100 years and are spaced by several 1,000 years.” They believed that since large bodies are presently known to exist within the Taurid Complex, then these periods of high meteor rates in Earth’s atmosphere could have been accompanied by “large body (Tunguska-sized) impacts.”200 Asher and Clube (1993) said the Taurid meteor stream was moving in a 7:2 resonance with Jupiter and suggested this could lead to concentrations within the meteor stream. Their predictions of encounters with Earth indicated probable enhanced activity at intervals ranging from 3 to 7 years. 201 M. Beech, M. Hargrove, and P. G. Brown (2004) examined the results of six fi reball surveys conducted during 1962–2002 and found “enhanced, or at least conspicuous, numbers of Taurid fi reballs were recorded on all eight occasions predicted by the resonance-controlled, swarm-encounter model.”202 As an example, Asher and Clube had predicted enhanced activity in 2005. In a paper by A. Dubietis and R. Arlt (2006), enhanced activity was noted for the Taurid meteor shower from 2005 October 28-November 11, when the ZHR was ³ 10. Maximum occurred on November 1/2 (l = 219.6), at which time the ZHR was 15.3, and they noted that this was “a week earlier and two times stronger than the ‘traditional’ maximum of the annual Taurid meteor shower.” They added, “A high proportion of bright Taurid meteors has to be noted, and is re fl ected by an unusually low population index of r = 1.90.”203 The orbits labeled “1960-N” and “1960-S” are from Kashcheyev and Lebedinets (1967), but the ascending node ( W ) is early, because the equipment did not operate after October 23. The orbits labeled “1990-N” and “1990-S” are from J. Stohl and V. Porubcan (1990) and were determined from 144 photographic orbits.204 The orbit labeled “1961–1965” is from Sekanina (1970) and the orbit labeled “1968–1969” is from Sekanina (1976). Even though neither of Sekanina’s surveys detected both branches, it is obvious that the southern branch in fl uenced the “1961–1965” orbit, while the northern branch in fl uenced the “1968–1969” orbit.

w W (2000) i q e a 1960-N 294.6 206.1 5.5 0.36 0.84 2.17 1968–1969 293.6 217.9 0.0 0.398 0.750 1.60 1990-N 293.0 228.0 3.1 0.369 0.826 2.14 1960-S 118.3 15.2 2.2 0.33 0.84 2.08 1961–1965 114.3 50.2 1.4 0.385 0.770 1.68 1990-S 113.8 38.7 5.5 0.370 0.815 2.03 298 12 November Meteor Showers

Numerous objects have been found to be associated with the Taurid streams, but only a few are listed below. The orbit labeled “2P” is that of periodic comet Encke. The orbit labeled “2201” is that of the minor planet Oljato. The orbit of the minor planet “4183” is that of the minor planet Cuno. The orbit labeled “4341” is that of the minor planet Poseidon. The orbit labeled “69230” is that of the minor planet Hermes. The orbit labeled “b Taurids” is that of the June daytime shower.

w W (2000) i q e a 2P 186.54 334.57 11.78 0.3362 0.8481 2.21 2201 98.19 75.01 2.52 0.6246 0.7124 2.17 4183 236.28 294.93 6.71 0.7253 0.6341 1.98 4341 15.62 108.12 11.85 0.5881 0.6796 1.84 69230 92.68 34.26 6.07 0.6224 0.6240 1.66 b Taurids 239.2 275.2 0.3 0.274 0.834 1.65

Chi Taurids

This is a newly discovered meteor shower that was ﬁ rst recognized by P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010). Using the Canadian Meteor Orbit Radar system from 2002 to 2008, they detected 1,850 meteors from this stream. These meteors indicated a duration from October 7-November 9 (l = 194°– 227°), with maximum occurring on November 2 (l = 220°) from a radiant at a = 63.2°, d = +24.7°. The geocentric velocity was 42.1 km/s, while the radiant drift was determined as +0.96° in a and +0.19° in d per day.56 The International Meteor Organization has a web site containing an analysis of more than one million meteors detected by the cameras of the Video Meteor Network from 1993 into 2012. Stream number 206 is based on 901 meteors. The duration is given as October 31-November 12 (l = 217°–229°), while maximum occurs on November 12 (l = 229°) from a radiant at a = 67.1°, d = +28.5°. The radiant drift was determined as +0.5° in a and +0.2° in d per day.205 The orbit labeled “2002–2008” is from Brown et al. (2010).

w W (2000) i q e a 2002–2008 328.49 220.0 12.3 0.0807 0.984 4.97 Chi Taurids 299

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128. P. Jenniskens, Central Bureau Electronic Telegram, No. 2046 (2009 Nov. 24). 129. G. W. Kronk, Cometography, volume 2. United Kingdom: Cambridge University Press (2003), pp. 343–5. 130. T. Von Oppolzer, Astronomische Nachrichten , 68 (1867 Jan. 28), p. 241. 131. U. J. J. Le Verrier, Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences , 64 (1867 Jan.), pp. 94–9. 132. C. F. W. Peters, Astronomische Nachrichten , 68 (1867 Feb. 4), pp. 287–8. 133. G. V. Schiaparelli, Astronomische Nachrichten , 68 (1867 Feb. 20), pp. 331–2. 134. T. Oppolzer, Astronomische Nachrichten , 68 (1867 Feb. 20), pp. 333–4. 135. J. C. Adams, Monthly Notices of the Royal Astronomical Society , 27 (1867 Apr.), pp. 247–52. 136. G. Johnstone Stoney and A. M. W. Downing, Astronomische Nachrichten , 149 (1899 Apr. 1), pp. 33–8. 137. G. Johnstone Stoney and A. M. W. Downing, Nature , 61 (1899 Nov. 9), pp. 28–9. 138. G. Johnstone Stoney and A. M. W. Downing, Nature , 63 (1900 Nov. 1), p. 6. 139. T. Murakami, Publications of the Astronomical Society of Japan , 11 (1959), pp. 151–6. 140. E. I. Kazimirchak-Polonskaya, N. A. Belyaev, I. S. Astapovich, and A. K. Terentjeva, Soviet Astronomy , 11 (1967 Nov.–Dec.), pp. 490–500. 141. Y. V. Evdokimov and E. D. Kondrat ’ eva, Trudy Kazanskaia Gorodkoj Astronomicheskoj Observatorii , 38 (1972), pp. 68–73. 142. I. S. Astapovich and A. K. Terentjeva, Problemy Kosmicheskoi Fiziki , 7 (1972), pp. 100–7. 143. D. K. Yeomans, Icarus , 47 (1981), p. 492. 144. E. D. Kondrat’ eva and E. A. Reznikov, Solar System Research , 19 (1985 Oct.), pp. 96–101. 145. L. Kresak, Meteoroids and their parent bodies , Proceedings of the International Astronomical Symposium held at Smolenice, Slovakia, July 6–12, 1992, Edited by J. Stohl and I.P. Williams, Bratislava: Astronomical Institute, Slovak Academy of Sciences (1993), pp. 148, 154. 146. R. H. McNaught and D. J. Asher, WGN, Journal of the International Meteor Organization , 27 (1999 Apr.), pp. 85–102. 147. R. H. McNaught, Personal Communication (1999 March 30–31). 148. P. Jenniskens, S. J. Butow, and M. Fonda, Earth, Moon, and Planets , 82–83 (2000), pp. 1–26. 149. H. Betlam, P. Jenniskens, P. Spurny, G. D. van Leeuwen, K. Miskotte, C. R. Ter Kuile, P. Zarubin, and C. Angelos, Earth, Moon, and Planets , 82–83 (2000), pp. 277–84. 150. C. P. Olivier, Popular Astronomy , 34 (1926 Mar.), pp. 167–8. 151. C. P. Olivier, Popular Astronomy , 44 (1936 Feb.), p. 89. 152. C. P. Olivier, Popular Astronomy , 44 (1936 Jun.–Jul.), pp. 327–8. 153. L. Kresák, Bulletin of the Astronomical Institutes of Czechoslovakia, 9 (1958 May 1), pp. 88–96. 154. Meteor News , No. 73 (1986 Apr.), p. 6. 155. W. Doberck, Astronomische Nachrichten , 140 (1896 Jun. 15), pp. 375–80. 156. C. P. Olivier, Flower Observatory Reprint , No. 4 (1929), p. 21. 157. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), p. 244. 158. M. T. Adams, Meteor News , No. 74 (1986 Jul.), p. 7. 159. L. Kresák, Meteoroids and their parent bodies, Proceedings of the International Astronomical Symposium held at Smolenice, Slovakia, 1992 July 6–12. Bratislava: Astronomical Institute, Slovak Academy of Sciences (1993), edited by J. Stohl and I.P. Williams, p. 147. 160. P. Jenniskens, WGN, Journal of the International Meteor Organization , 23 (1995 Jun.), pp. 84–6. 161. P. Spurny, J. Borovicka, L. Bellot, A. Roman, F. Reyes, J. Rendtel, R. Haver, R. Gorelli, Z. A. Nagy, K. Sarenczky, and I. Tepliczky, International Astronomical Union Circular , No. 6265 (1995 Nov. 22). 162. J. Rendtel, WGN, Journal of the International Meteor Organization , 23 (1995 Dec.), pp. 200–3. 163. J. Rendtel, P. G. Brown, and S. Molau, Monthly Notices of the Royal Astronomical Society , 279 (1996), pp. L31–6. Chi Taurids 303

164. A. McBeath, WGN, Journal of the International Meteor Organization, 33 (2005 Dec.), p. 162. 165. R. E. McCrosky and A. Posen, Astronomical Journal , 64 (1959 Feb.), p. 26. 166. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), pp. 16–17. 167. B. A. Lindblad, Smithsonian Contributions to Astrophysics , 12 (1971), p. 6. 168. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 285. 169. N. W. McLeod, III, Meteor News , No. 39 (1978 Jan.), p. 6. 170. E. Heis, Astronomische Nachrichten , 69 (1867 May 27), p. 160. 171. T. W. Backhouse, Report of the Annual Meeting of the British Association for the Advancement of Science , 40 (1871), p. 97. 172. G. L. Tupman, Monthly Notices of the Royal Astronomical Society , 33 (1873 Mar.), p. 304. 173. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 238. 174. R. P. Greg, Monthly Notices of the Royal Astronomical Society , 32 (1872), p. 353. 175. R. P. Greg, Report of the Annual Meeting of the British Association for the Advancement of Science , 44 (1875), p. 337. 176. H. Corder, Monthly Notices of the Royal Astronomical Society , 40 (1880 Jan.), p. 138. 177. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 42 (1881 Dec.), p. 90. 178. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 44 (1884 Apr.), p. 299. 179. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 50 (1890 May), pp. 457–8. 180. A. King, Monthly Notices of the Royal Astronomical Society , 79 (1918 Dec.), pp. 158–9. 181. W. F. Denning, The Observatory , 43 (1920 Dec.), p. 432. 182. W. F. Denning, The Observatory , 44 (1921 Dec.), p. 376. 183. W. F. Denning, The Observatory , 46 (1923 Jan.), p. 25. 184. W. F. Denning, The Observatory , 47 (1924 Jan.), p. 31. 185. W. F. Denning, The Observatory , 47 (1924 Aug.), p. 255. 186. F. L. Whipple, Proceedings of the American Philosophical Society , 83 (1940 Oct.), p. 742. 187. I. S. Astapovich and A. K. Terentjeva, Physics and Dynamics of Meteors. eds. L. Kresák and P. M. Millman. Dordrecht: D. Reidel Publishing Company, 1968, pp. 316–17. 188. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 140–1. 189. F. W. Wright and F. L. Whipple, Technical Reprint of Harvard College Observatory, No. 6 (1950). 190. G. S. Hawkins and M. Almond, Monthly Notices of the Royal Astronomical Society , 112 (1952), p. 223. 191. K. Bullough, Jodrell Bank Annals , 1 (1954 Jun.), pp. 80–1. 192. Z. Sekanina, Icarus , 13 (1970), p. 482. 193. O. H. J. Knopf, Astronomische Nachrichten , 242 (1931 May 25), p. 161. 194. C. Hoffmeister, Die Meteor. Leipzig: Akademische Verlagsgeselleschaft M. B. H. (1937), p. 46. 195. F. L. Whipple, Proceedings of the American Philosophical Society , 83 (1940 Oct.), pp. 711–45. 196. F. L. Whipple, and S. Hamid, Astronomical Journal , 55 (1950 Oct.), pp. 185–6. 197. F. L. Whipple, Proceedings of the American Philosophical Society , 83 (1940 Oct.), p. 723. 198. M. Almond, Monthly Notices of the Royal Astronomical Society , 111 (1951), p. 41. 199. K. B. Hindley, Journal of the British Astronomical Association , 82 (1972), pp. 287–98. 200. D. I. Steel, D. J. Asher, and S. V. M. Clube, Monthly Notices of the Royal Astronomical Society , 251 (1991), pp. 632–48. 201. D. J. Asher and S. V. M. Clube, Quarterly Journal of the Royal Astronomical Society , 34 (1993), p. 485, 490. 202. M. Beech, M. Hargrove, and P. G. Brown, The Observatory , 124 (2004 Aug.), pp. 203. A. Dubietis and R. Arlt, WGN, Journal of the International Meteor Organization , 34 (2006 Feb.), pp. 3–6. 204. J. Stohl and V. Porubcan, Asteroids, comets, meteors III, Proceedings of a meeting (AMC 89) held at the Astronomical Observatory of the Uppsala University, June 12Ð16, 1989 . Edited by C. I. Lagerkvist, H. Rickman, and B. A. Lindblad, Uppsala: Universitet (1990), pp. 571–4. 205. http://www.imonet.org/showers/shw206.html Chapter 13

December Meteor Showers

Delta Arietids

The fi rst recognition of a possible December radiant near the star Delta Arietis was made by R. E. McCrosky and A. Posen (1959), while analyzing the photographic meteor orbits obtained by the Harvard Meteor Project from 1952 to 1954. Seven meteors indicated a shower was active from December 8 to 13 ( l = 256–261°), with a probable maximum on the 8th. The average radiant was given as a = 51°, d = +21°.1 In 1971, a computerized stream search of the same collection of photographic meteors was conducted by B. A. Lindblad. This revealed 14 meteors as belonging to the Delta Arietids; however, Lindblad noted that 12 of the meteors belonged to a northern branch, while two belonged to a southern branch.2 These meteors indicate the duration of the northern branch was December 8–January 2 ( l =256–281°), while that of the southern branch was December 11–16. A. K. Terentjeva (1989) examined the photographic data of 554 fi reballs detected by fi reball networks in the United States and Canada from 1963 to 1984. She found that 375 could be fi t into 78 different fi reball streams. Stream number 70 was called the Delta Arietids and was active from November 22 to December 21. Terentjeva found three distinct branches, with radiants of a = 53°, d = +29°, a = 55°, d = +18°, and a = 61°, d = +07°.3 A group of 20 members of the Dutch Meteor Society (DMS) fl ew to southern Spain during 1995 November 17–22 to observe the Leonids and Alpha Monocerotids. Simultaneous video observations allowed the determination of 189 meteor orbits. In a paper written by M. de Lignie and H. Betlam (1997), it was noted that four of

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 305 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3_13, © Springer Science+Business Media New York 2014 306 13 December Meteor Showers the meteors were from the Northern Delta Arietids. The radiant was determined as a = 46.9°, d = +22.8°, while the geocentric velocity was 18.3 km/s.4 A brief examination of the Dutch Meteor Society database of multi-station video orbits reveals that two of these meteors were seen on November 18, one on November 21, and one on November 22. J. Greaves (2000) examined comet-meteor associations and found that the Apollo asteroid 217628 Lugh [previously known as 1990 HA] appears to be associated with the Northern Delta Arietids. He said a comparison with the four meteors found by the DMS in 1995 reveals a D-criterion of 0.077–0.132—values which suggest an association.5 J. Stohl and V. Porubcan (1993) had suggested that this asteroid could produce a meteor shower a few years earlier. They said the geocentric velocity of the meteors would be around 15.9 km/s. They said they found 14 precise meteor orbits that matched the asteroid orbit with a D-criterion value of <0.20. A plot of the radiant positions of these meteors, indicated a radiant 20–30° across. Comparing this result with the result of asteroids producing meteors with higher and lower velocities, they noted that an “inverse dependence of the diameter of the radiant area on the velocity is evident.” They added, It makes meteor streams of very low geocentric velocity even less detectable. It is therefore not surprising that we fi nd possible associations of asteroids with meteors mostly among minor meteor streams, or even as streams which as such are almost completely undetect- able, except of careful investigation of their orbits.6 M. Langbroek (2003) further examined Greaves’ suggested association. Using the asteroid’s orbit, he said the theoretical maximum would come on December 5 from a radiant at a = 53°, d = +22°, which he said “correspond closely to the velocity, radiant, and maximum date of MeCrosky and Posen’s d Arietids.” He conducted a search for meteor orbits and found 11 in the DMS video database (including the four found earlier) and two were found in the DMS photographic database. Langbroek noted that these were found during the Leonid, Geminid, and Quadrantid campaigns of 1990, 1995, 1996, and 1998. He found 23 additional photographic orbits in the International Astronomical Union database. Langbroek found that these evenly separated into northern and southern branches, where the only real difference was a 180° shift in w and W . These meteors indicated the duration of the northern branch was November 7–January 4, while the duration of the southern branch was November 17–December 22. For early December, the northern branch produces meteors from a = 43°, d = +26°, while the southern branch produces meteors from a = 48°, d = +11°. The geocentric velocity of the northern branch is 15.02 km/s, while it is 16.1 km/s for the southern branch. Langbroek also suggested the possibility of the daylight meteor shower from this stream during March–April.7 Y. Shigeno and M.-Y. Yamamoto (2012) examined the database of 3770 double- station image-intensifi ed video observations that had been acquired from Japan from 1992 to 2009. They found 16 probable members of the Southern Delta Arietids in this data, of which fi ve were used to determine the mean radiant and orbit. The mean date of activity was December 12 (l = 260.19°), while the average radiant was at a = 72.9°, d = +16.0°. The geocentric velocity was 16.0 km/s.8 11 Canis Minorids 307

No trace of this stream seems to be present in records covering the nineteenth century, but the fi rst appearance of shower members may have occurred early in the twentieth century, when several fi reballs appear in various sources. The fi rst really good visual radiants from this stream appear in C. Hoffmeister’s Meteorströme in 1912 and 1932. The most detailed observation obtained thus far was by observers in Waltair, India, on 1964 December 8. M. Srirama Rao, P. V. S. Rama Rao, and P. Ramesh plotted ten meteors from a = 57°, d = +22° and concluded that the radiant produced a rate of 7.5 meteors per hour. 9 However, numerous observers’ attempts to observe the shower during the 1970s in 1980s have never shown hourly rates greater than one at the time of the predicted maximum. The International Meteor Organization (IMO) has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. There are de fi nite signs of this radiant group among these records covering the range of radiants noted above. Two radiants were detected on December 11 (l = 259°): 128 meteors from a = 61.8°, d = +21.5° and 172 meteors from a = 75.9°, d = +13.0°. Two radiants were detected on December 12 (l = 260°): 62 meteors came from a radiant at a = 45.0°, d = +15.0° and 155 came from a = 74.6°, d = +12.0°. Two radiants were detected on December 13 (l = 261°): 94 meteors from a = 56.5°, d = +11.0° and 181 meteors from a = 73.9°, d = +21.0°. There are many more besides these.10 The orbit labeled “1959-N” is from McCrosky and Posen (1959). The orbits labeled as “T-N,” “T-Q,” and “T-S” are from Terentjeva (1989) and represent the north, “Q”, and south branches. The orbit labeled “DMS-N” is from de Lignie and Betlem (1997). The orbit labeled “Japan-S” is from Shigeno and Yamamoto (2012). The orbit labeled “217628” is the Apollo asteroid Lugh. The orbits of the northern and southern branches as determined from 12 to 3 meteors, respectively, are as follows:

w W (2000) i q e a 1959-N 229.6 260.2 1.3 0.848 0.638 2.34 T-N 247.2 251.9 4.2 0.766 0.560 1.83 T-Q 60.0 75.4 1.2 0.786 0.671 2.44 T-S 62.9 76.0 5.8 0.788 0.591 1.98 DMS-N 256.5 237.3 2.9 0.681 0.681 2.13 Japan-S 73.6 80.0 3.0 0.719 0.601 1.80 217628 310.15 183.16 4.02 0.7566 0.7033 2.55

11 Canis Minorids

The discovery of this radiant came about on the morning of 1964 December 11, while K. B. Hindley was conducting a telescopic meteor watch so as to “record positional details of Geminid meteors.” The watch lasted 3 h and 45 min, during 308 13 December Meteor Showers which time 26 telescopic meteors were detected. Six of these meteors proved to be true Geminids, but ﬁ ve others clearly emanated from an area 35 arc minutes across centered at a = 117.0°, d = +12.8°. The meteors ranged in brightness from 6.0 to 11.0 and were described as white and swift. On the night of December 13/14, Hindley observed for 4.5 h, but no trace of activity was noted from the 11 Canis Minorid radiant, which brought Hindley to conclude that the shower possessed a very short duration. Hindley noted a similarity between this orbit and that of comet C/1821 B1 (Nicollet-Pons), although “the difference of 28° in the longitude of the ascending node made it unlikely that these two orbits are in fact related.”11 Hindley and M. A. Houlden (1970) revised the radiant to a = 115°, d = +12° and suggested that comet C/1917 F1 (Mellish) might have produced the stream.12 New light was shed on the stream during 1974, while M. Kresáková was investigating photographic meteor orbits in an attempt to suggest a link between comet C/1917 F1 (Mellish) and the Geminids. She found nine meteors that were photographed from 1950 to 1958, which she named “short-period component B.” The suggested duration was December 4–15. The average radiant was determined as a = 109.3°, d = +12.4°, while the daily motion was given as +0.53° in a and −0.37° in d. Kresáková concluded that component B might be part of a chain association, whereas comet Mellish produced “long-period component A,” now known as the December Monocerotids, which in turn produced the 11 Canis Minorids, which subsequently produced the Geminids. Kresáková theorized that the chain could have started following a disruption of comet Mellish.13 The Western Australia Meteor Section made observations of this radiant in 1979. The overall duration was given as December 7–9, while a maximum ZHR of about one occurred on the 9th from a radiant of a = 116°, d = +14°. 14 There has been no trace of this meteor shower in recent times, as the Canadian Meteor Orbit Radar and the highly successful Video Meteor Network of the International Meteor Organization have failed to detect stream members in the 1990s and 2000s. The orbit labeled “1969” is from Hindley (1969). The orbit labeled “1970” is from Hindley and Houlden (1970). The orbit labeled “1974” is from Kresáková and represents “short-period component B.” The orbit labeled “C/1821 B1” is comet Nicollet-Pons. The orbit labeled “C/1917 F1” is comet Mellish.

w W (2000) i q e a 1969 157.4 78.7 107.9 0.038 1.0 ∞ 1970 158 79 89 0.04 1.0 ∞ 1974 150.9 79.5 29.1 0.092 0.942 1.64 C/1821 B1 169.21 51.18 106.46 0.092 1.0 ∞ C/1917 F1 121.32 88.67 32.68 0.190 0.993 27.65 Coma Berenicids 309

Coma Berenicids

Duration: December 8 to January 23 (l = 256–302°) Peak: December 19/20 (l = 268°) @ a = 165°, d = +30°

Radiant Drift: a = +0.91°, d = −0.47° V G : 63 km/s The fi rst hint of this stream’s existence came in 1954, when F. L. Whipple published a paper in The Astronomical Journal containing the orbits of 144 photographic meteors. He found three meteors which he labeled as “association VII”: one detected on 1942 December 9 and two detected on 1950 December 13. Together they indicated a radiant of a = 150.8°, d = +33.3°. Whipple described this stream as, “A long-period highly retrograde orbit considerably spread….”15 Interestingly, there was a meteor designated “1918” that was photographed on 1950 January 20 that Whipple labeled a sporadic. It emanated from a radiant at a = 185.7°, d = +20.5°. Although Whipple did not notice the similarity between its orbit and those of the other three meteors of association VII, he did notice a similarity between the orbit of the January meteor and the orbit of a very uncertain comet that was discovered near the end of 1912 and was designated “1913 I”. Rough orbits were calculated by two well-known astronomers of the time and, although there was a general agreement between them, there was a notable difference in the inclination of these orbits. Whipple said these orbits were similar to that of the January meteor, while one of the comet orbits actually had an inclination that was a near match. He said the orbital similarities between the meteor and the comet would make an association “fairly probable except for an uncertainty in the inclination of the comet’s orbit.” Whipple added, “if future meteor observations con fi rm the association, we may learn more about the orbit of Comet Lowe by meteor studies than we can glean from the direct observation.”16 R. E. McCrosky and A. Posen (1959) were searching through the orbits of 2538 meteors that were photographed during the Harvard Meteor Project of 1952–1954. They found six meteors spanning the period of January 13–23, which they called the “Coma Berenicieds.” The probable maximum came on January 17 from a radiant at a = 187°, d = +18°. This stream had a similar radiant and orbit as meteor “1918” that was published in Whipple’s paper. They reiterated Whipple’s suggestion of a possible association to comet “1913 I”.17 An important development in the understanding of this stream came in 1973. A. F. Cook, B. A. Lindblad, B. G. Marsden, McCrosky, and Posen isolated seven photographic meteors from the same collection of Harvard meteors used by McCrosky and Posen in 1959. They gave the duration as December 12–17 and referred to the stream as the “December Leo Minorids.” They said the peak occurred on December 17 from an average radiant of a = 156.1°, d = +34.6°. They commented that the “orbit bears a strong resemblance to that of the Coma Berinicids in January.”18 Indeed, the orbits of both streams are so similar that their mutual existences cannot be due to mere chance. Unfortunately, there was a gap in the photographic 310 13 December Meteor Showers records that spanned the period of late December and early January that would have provided a vital link between these two streams. During the late 1950s and throughout the 1960s, several radio-echo surveys were conducted which should have detected this stream, but no trace was revealed. The more sensitive Canadian Meteor Orbit Radar (CMOR) went into full-time operation in 2002. The fi rst paper to present results was published in 2008, but this stream was again absent; however, CMOR would come through 2 years later. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) presented the results of the CMOR survey that spanned the 7 years from 2002 to 2008. They found 1304 meteors from a stream they called the “December Leo Minorids.” They noted activity from December 13 to January 7 (l = 261–286°) and added that maximum occurred on December 19/20 (l = 268°) from a radiant at a = 162.2°, d = +29.9°. The authors also gave the geocentric velocity as 62.8 km/s and noted the radiant’s daily motion as +0.91° in a and −0.47° in d .19 The International Meteor Organization (IMO) has a web site containing an analysis of more than one million meteors detected by cameras of the Video Meteor Network from 1993 into 2012. Stream number 245 is called the “December Comae Berenicids” and is based on 6865 meteors. The duration is given as December 3–January 19 (l = 251–299°), during which time the radiant moves from a = 145.6°, d = +37.5° to a = 188.2°, d = +18.0°. Maximum occurs on December 17 (l = 265°) from a radiant at a = 159.2°, d = +32.0°. The radiant drift was determined as +0.9° in a and −0.4° in d per day.20 Few visual observations have been made of this shower in the years following its discovery. Amateur astronomers in Western Australia have failed to detect it annually, which indicates either an irregular distribution of this stream’s meteors or very weak annual activity. During the period of 1969–1980, M. Buhagiar (Perth, Western Australia, Australia) plotted 20,974 meteors for the purpose of compiling a list of southern hemisphere meteor radiants. On two occasions during those 12 years, he detected a radiant near Delta Leonis. Given a duration of December 20–23 and a maximum on December 21, the activity radiated from a = 167°, d = +27° with a maximum hourly rate of 2.21 The Western Australia Meteor Section, led by J. Wood, managed to detect activity from this radiant in 1980 on January 5–6. A maximum ZHR of about 6 was detected on January 6 from a = 171°, d = +24°. 14 On checking to see if observations of this shower could be found in previous publications, the oldest identi fi ed was an observation by T. W. Backhouse (Sunderland, England) on 1878 December 20/21. He reported seven meteors were plotted from a radiant located at a = 157°, d = +35°. 22 H. Corder (Bridgwater, Somerset, England) plotted four meteors from a radiant of a = 162°, d = +34° on 1895 December 10–15.23 M. A. R. Khan (Begumpet, India) plotted six meteors on 1940 December 29 that came from a radiant as a = 171°, d = +31°. 24 J. H. Knowles (Marblehead, Massachusetts, USA) plotted four meteors from a radiant at a = 170°, d = +22.5° on 1948 December 29.25 There have been indications of a renewed interest in this stream in the last 25 years. B. Koch, M. Nolle, and S. Ströbele, were observing in Southern France from 1987 December 20 to 29 and noted meteors from this radiant on every night. The Coma Berenicids 311 night of December 27/28 was the best as hourly rates ranged from 3 to 8. The average magnitude of 76 of these meteors was 3.7.26 R. Taibi (Maryland, USA) published the results of his observations of this shower from 1984 to 1989. Overall, his observations covered the period of December 12–February 22 and he saw a total of 33 Coma Berenicids. His four best nights were 1984 December 29 (three meteors in 2 h), 1986 January 17 (three meteors in 2 h), 1986 December 28 ( fi ve meteors in 1.88 h), and 1989 January 12 (three meteors in 2 h). Taibi added that the average magnitude of his meteors was 3.33 and noted that the observers in Koch’s group enjoyed skies that “were about one magnitude darker than my site….”27 Compilation of a database consisting of 23 photographic meteors that were detected during surveys in the United States, Tajikistan, and Ukraine from 1942 to 1963 indicate these meteors follow an orbital period of 72.4 years, but what is most striking is that this orbit seems to be composed of two fairly distinct fi laments with periods of 27.3 and 157.1 years. In addition, the orbital inclinations differ very little, while the perihelion distances vary by 0.1 AU and the argument of perihelion differs by 13°. A comparison is given in the “Orbit” section below. This seems to be a very complex region, as several branches appear to be active in Coma Berenices and Leo Minor in December and January. The latest IMO meteor shower calendar lists the Coma Berenicids and the December Leo Minorids as separate showers, yet the analysis of the IMO’s Video Meteor Network mentioned above shows three separate Coma Berenicid meteor showers in December and does not mentioned the December Leo Minorids. Some surveys have failed to distinguish between the two radiants (e.g., CMOR) and the respective meteor streams have very similar, if not identical, orbits. It is certainly a region that requires more study. The fi rst three orbits were determined from an initial database of 23 photographic meteors. The fi rst orbit uses all 23 meteors, while the other two represent the two groups that seem to be present in this data. The orbit labeled “2002–2008” is that from Brown et al. (2010).

w W (2000) i q e a 264.9 278.5 134.4 0.547 0.969 17.38 260.2 280.4 135.4 0.582 0.980 29.12 273.6 275.0 132.5 0.481 0.947 9.08 2002–2008 263.57 268.0 135.5 0.5662 0.916 6.73

The orbit below is that of the very uncertain comet discovered by Lowe, which was designated “1913 I”. M. A. Viljev calculated the orbit in 1913.28

w W (2000) i q e a 1913 I 280.3 304.9 120.5 0.405 1.0 ∞ 312 13 December Meteor Showers

December Alpha Draconids

The discovery of this meteor shower was announced in 2009 by the Japanese video meteor network SonotaCo. During a survey spanning 2007–2008, they detected 145 meteors from a radiant at a = 207.9°, d = +60.6°. The radiant was active from November 18 to December 29 (l = 236.4–278.3°), with the peak occurring on December 8 ( l = 256.5°). The geocentric velocity was given as 41.0 km/s, while the radiant drift was determined as +0.40° in a and −0.14° in d per day.29 The International Meteor Organization’s video meteor network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2012. Stream number 233 is called the “December Alpha Draconids” and is based on 1423 meteors. The duration is given as December 1–19 ( l = 249–267°), while maximum occurs on December 4 (l = 252°) from a radiant at a = 209.5°, d = +58.0°. The radiant drift was determined as +0.1° in a and −0.2° in d per day.30 The orbit below was calculated using the radiant and velocity provided by the IMO Video Meteor Network.

w W (2000) i q e a 168.1 251.6 71.2 0.981 0.277 1.36

December Kappa Draconids

The discovery of this meteor shower was announced in 2009 by the Japanese video meteor network SonotaCo. During a survey spanning 2007–2008, they detected 61 meteors from a radiant at a = 186.0°, d = +70.1°. The radiant was active from November 21 to December 11 (l = 239.7–259.7°), with the peak occurring on December 2 ( l = 250.2°). The geocentric velocity was given as 43.4 km/s, while the radiant drift was determined as +0.05° in a and −0.09° in d per day.29 The International Meteor Organization’s video meteor network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2011. Stream number 229 is called the “December Kappa Draconids” and is based on 682 meteors. The duration is given as December 2–9 ( l = 250–257°), while maximum occurs on December 3 (l = 251°) from a radiant at a = 185.7°, d = +70.5°. The radiant drift was determined as +1.4° in a and −0.5° in d per day.31 [Vinf = 43.0 km/s] The orbit below was again calculated using the radiant and velocity provided by the IMO Video Meteor Network. Geminids 313

w W (2000) i q e a 226.9 250.5 69.8 0.878 0.525 1.85

Geminids

Duration : December 6 to December 19 (l = 254–267°) Maximum : December 13/14 (l = 261.2°) Radiant : a = 113°, d = +32° ZHR : 120

Radiant Drift : a = +0.83°, d = −0.28° V G : 35 km/s This meteor shower is currently among the top three strongest meteor showers to appear every year; however, despite observations made in the 1830s, 1840s, and 1850s, it was not until the 1860s that it was recognized as an annual display. There are indications that the shower became stronger as the nineteenth century progressed.

Discovery

Two reports were published in the 1830s which probably refer to the Geminids based on their dates of peak activity and the area of the sky the meteors were seen. The ﬁ rst came from L. F. Kämtz (Heiligenstadt, Austria). He wrote that on the night of 1830 December 12/13, about 40 bright meteors were seen in a short period of time heading toward the southeast. 32 The second account comes from E. C. Herrick (Connecticut, USA). He said that he and a small group of assistants were observing a meteor shower in 1838. This meteor shower would later become known as the Andromedids. After seeing large numbers of meteors from December 6 to 8, observations were continued on almost “every favorable evening” though the 15th. Covering the eastern quarter of the sky for 75 min on the evening of the 11th, one observer saw 18 meteors. During 120 min on the evening of the 12th, an observer facing the eastern quarter saw 18 meteors. A single observer saw ten meteors during 45 min on the 13th. Finally, two observers observed the eastern and western quarters of the sky for a total of 150 min on the evening of the 15th and saw a total of nine meteors.33 Several observations were made during the 1840s. On the evening of 1846 December 9, A. Colla (Parma Observatory, Italy) reported that he saw “a considerable number of shooting stars.” On the 10th, he reported that “many stars” were seen in the evening. 34 On the night of 1847 December 12, E. J. Lowe (Nottingham, Nottinghamshire, England) reported, “Many falling stars noticed in the constellations Orion, Taurus, Gemini, and Auriga.”35 E. Heis (Aachen, Germany) saw “10 shooting stars; many of the ﬁ rst magnitude and with trains” between 5:38 and 6:50 a.m. on 1848 December 11. 36 Also during 1848, Colla observed “many shooting stars” on December 14–15.37 314 13 December Meteor Showers

Lowe made an interesting statement in 1849. He wrote that the period of December 6–12 was one of six “epochs when falling stars are said to be abundant,” but added that it was “somewhat doubtful.”38 Had he not expressed doubt, he might be considered as the fi rst person to recognize the Geminids as an annual display; however, the early part of the period he mentions also included the Andromedid meteor shower, which had already been identi fi ed as an annual display by Herrick during 1839. The only observation made in the 1850s came from Lowe, when he spotted “many meteors” on the night of 1855 December 12.39 The Geminids became unmistakably active in the 1860s. F. Miller and several students from Stanmore School (Montgomery County, Maryland, USA) observed on the night of 1860 December 12 and spotted 180 different meteors. A total of 30 meteors were counted during 8:20–9:00 p.m., 34 meteors during 9:00–10:00 p.m., 56 meteors from 10:00 to 11:00 p.m., and 60 meteors from 11:00 p.m. to midnight. 40 G. Wood was riding from Philadelphia, (Pennsylvania, USA) to Haverford College (about 8 miles to the west) on the morning of 1861 December 12. From about 4:30 a.m. until daybreak, he spotted “not less probably than 25 [meteors], chie fl y in the northwest.”41 The offi cial recognition that this was an annual shower was fi rst made by B. V. Marsh (Philadelphia), who observed activity on the night of 1862 December 10/11. From 10:30 to 11:00 p.m., he reported “about half a dozen brilliant meteors” and he noted the radiant was around Castor and Pollux in Gemini. He observed again from 4:00 to 4:30 a.m. the next morning, and wrote that the meteors “were not remarkable for number or brilliancy, but all radiated from the same vicinity.” Marsh added that Wood’s observation of the previous year “would agree very well with this radiant, so that I think there is strong reason to conclude that from the 10th to the 12th of December the meteors mostly belong to one group radiating from the vicinity of Castor and Pollux.”42 R. P. Greg (Prestwitch, England) independently observed this meteor shower on 1862 December 10 and 11 from about 6:00 to midnight. He said meteors appeared in “all quarters of the sky” on both nights and added that “10 or 12 meteors” were as bright as fi rst magnitude stars. Greg said the radiant was “ perfectly marked between Auriga and Gemini.”43 Portions of a letter written by Greg to the Connecticut Academy of Arts and Sciences were published in the May 1864 issue of the American Journal of Science and Arts. He stated that the period of December 5–13 had produced a fi ne shower in recent years and noted the radiant was halfway between Alpha Gemini and Beta Aurigae.44

Observations

As the 1860s progressed, more details came forth. The fi rst precise position of the radiant seems to have been determined by A. S. Herschel (Hawkhurst, England), who plotted 17 meteors from a radiant at a = 105.5°, d = +30.5° on 1863 December 12/13. 45 The rate at which meteors fell during the Geminid display seemed to jump Geminids 315 in 1866. T. H. Waller (York, England) saw 15 meteors between 11:00 p.m. and midnight on the evening of December 10, which was a couple of days before the expected maximum. He said they were “mostly radiating from Castor.” W. H. Wood (Birmingham, West Midlands, England) noted that he was observing alone on the evening of December 12, when meteors started falling at a rate of “one per minute.” He added that they were “directed from a Geminorum.”46 The British Association for the Advancement of Science designated a committee to promote the study of meteor showers. Every year they collected observations and published them in an extensive paper in the Association’s annual report. From 1871 to 1872 they encouraged observers in Scotland and England to record “the appearances of shooting-stars visible on the annually recurring meteoric dates in August, October, November, December, January, and April.” Sadly, most locations across Scotland and England experienced overcast skies during the December period, but with so many observers watching the sky, some Geminids were seen. Herschel said the sky cleared after 10:15 p.m. and completely cleared after 11:00 p.m. He saw 30 meteors in all, 26 being Geminids. Herschel said half were brighter than magnitude 2. He said 14 of the Geminids indicated a radiant at a = 108°, d = +33°. H. W. Jackson (Tooting, England) was able to record the paths of seven Geminids on a map and found the radiant 8–10° across, with a center at a = 112°, d = +30°. A few other observers reported some success as well. After all of the plotted meteors were analyzed by the committee, they noted, “a radiant-region of oval form contained between the meridians of R. A. 96° and 112°, and between the parallels of north declination 20° and 40°, would include the directions of 37 of the 45 tracks which are thus drawn. In this area the intersections of the tracks, prolonged backwards, are slightly more concentrated than elsewhere within the radiant-space, at a point in R. A. 104°, N. Decl. 34°, about 4° from [Theta] towards a Geminorum, while the general character of the radiation was diffuse….”47 E. F. Sawyer (Cambridgeport, Massachusetts, USA) made a commitment to observe the Geminids in 1879 and 1884. In the fi rst year, cloudy weather prevailed until December 7. Thereafter, he had relatively clear nights on December 7, 9, and 12. He said eight meteors radiated from Gemini on the 7th, of which fi ve indicated a radiant at a = 100°, d = +35° and 3 indicated a radiant at a = 110°, d = +33°. He added that meteors from the fi rst radiant were “long, faint, and rapid,” while those from the second radiant were “short, bright, and rapid.” On the 9th, he recorded four meteors from the fi rst radiant and two from the second. Sawyer observed for 3.5 h on the 12th and recorded 37 meteors. A total of 21 meteors were Geminids, with six coming from the fi rst radiant noted above and 15 coming from the second radiant. He noted, “The brighter meteors were generally accompanied by streaks….” Sawyer added, “The meteor-tracks mapped on the 7th and 9th were deduced separately from those recorded on the 12th, but no shifting of either position could be detected.”48 Conditions were not much better in 1884, as he was only able to observe for 1 h on the evening of December 11. He saw 17 meteors, of which 13 were Geminids. Six of the Geminids came from a radiant at a = 99.5°, d = +32°, while four others came from a = 115°, d = +35°.49 W. F. Denning (Bristol, England) made observations of the Geminids on seven nights from 1885 November 30 to December 10, but was not able to follow the 316 13 December Meteor Showers shower thereafter. In 24.5 h of total observing time, he saw 252 meteors, of which 66 were Geminids. He said he saw no indication of activity from this radiant on November 30. He wrote, “On Dec. 1 I saw that meteors began to fall, somewhat scantily it is true, from near the normal position, and on Dec. 4 the shower had so far developed as to form the richest display visible.” In summarizing his observations, Denning noted three radiants: 34 meteors came from a = 107°, d = +33°, 21 came from a = 117°, d = +32°, and 11 came from a = 110°, d = +25°. He suggested the fi rst represented “true Geminids,” the other two “are implicated in apparently diffusing the radiant as well as augmenting the numerical strength of the display.” He added that meteors from the second radiant were generally brighter than meteors from the other two radiants.50 Denning summarized the observations of several observers made the night of 1892 December 12/13. These indicated low hourly rates of about 10 at maximum, which was similar to the last few years. Herschel (Slough, England) saw 24 meteors in nearly 3 h, noting that the Geminids were “not very active” and its position was not well defi ned. Six of the meteors indicated a radiant at a = 112°, d = +38°. H. Corder (Bridgwater, England) counted 66 meteors in about 5.3 h. He said 38 meteors came from a = 109°, d = +34°, while 12 others came from a = 117°, d = +30°. Denning said he observed for about 1.5 h, counting 20 meteors, of which 15 were Geminids. He said the “chief radiant point” was established as a = 119°, d = +29°, but said the center of the “true Geminids” was “indistinctly marked” at a = 107°, d = +34°. Denning added that the fi rst radiant produced “brighter and longer” meteors than the second radiant.51 According to a summary published in the 1902 issue of the Memoirs of the British Astronomical Association , Geminid meteors were not very plentiful in 1900. T. W. Backhouse (Sunderland, England) reported one in 41 min on December 9, three in about 40 min on December 11, seven in about an hour on December 12, and eight in about an hour on December 13. C. L. Brook (Meltham, England) observed for 2.5 h on the 11th and saw 11 Geminds. He counted 17 during about 3.4 h on the 12th. He added that the main radiant was at a = 111°, d = +31.5°. A. King (Leicester, England) saw no Geminids in 30 min on the 11th, 3 Geminids in 50 min on the 13th, and no Geminids on the 15th. T. H. Astbury (Wallingford, England) saw 15 Geminids in about 75 min on the 13th.52 The Geminids appear to have been very poorly observed during the fi rst 32 years of the twentieth century. Aside from a few radiants that occasionally appeared in various lists, only a few details of actual observations were published and these indicated fairly weak displays. Denning (1924) simply noted that the Geminids “were in considerable numbers” on 1920 December 12.6 (l = 260.78°) and “were also very active on 1923 December 13 in early evening.”53 A. G. Cook (1924) wrote, “Weather spoilt the chance of observing” the Geminids in 1922. She said the only report at hand was her own, which was made on December 13. During about 1.8 h, she saw 18 Geminids, of which 11 had their paths recorded.54 Perhaps the best coverage of the meteor shower during the 1930s came from a monthly column called “Meteor News” in the Journal of the Royal Astronomical Society of Canada . Geminids 317

P. M. Millman (1934) noted that observations from 1933 December 11 to 14 indicated “that this shower is a reliable one.” He described coordinated observations that were made at David Dunlap Observatory (Ontario, Canada). A total of 307 meteors were observed by fi ve people on the night of December 11/12, the majority being Geminids. Seven of these were “brighter than zero magnitude, the brightest being magnitude −3.” He said hourly rates were highest on the morning of the 12th, when, during one 20 min interval, the fi ve observers spotted 22 different Geminids. Millman said the night of December 12/13 was completely cloudy, while the sky was only clear for a short time on December 13/14. On the latter night, he said the Geminids were still active. One observer plotted 14 Geminids in 1 h 10 min, while three other observers plotted a total of 9 Geminids in 1 h 40 min. A little later, Millman said “a dozen meteors were seen on the 10 min walk from the highway in to the observatory,” which he said indicated they were more numerous than on December 11/12. Millman provided a plot showing the number of meteors seen per hour. He used factors, based on Denning’s statement that six observers could see half the visible meteors, to convert the existing data. The highest hourly rate was about 110. Magnitude estimates were made of 144 Geminids and 85 sporadics, with averages of 1.79 and 2.39, respectively.55, 56 Additional observations were published in “Meteor News” during the remainder of the 1930s. Millman said they only had one good night for both the 1934 and 1936 Geminids. For 1934, that night was on December 13/14. He converted the observations to the “six observer” method and found the highest rate was 120 per hour. Millman added, “The average magnitude for the 1934 Geminids is a whole magnitude brighter than for those observed in 1933.”57 The best night of the 1936 display was December 12/13. He saw 12 meteors during one 15 min interval and said the reduced rate was 160 per hour.58 Millman was able to observe the Geminids for several hours on the nights of 1937 December 11/12 and 12/13. The visual rates never exceeded 20 per hour.59 The Geminids were even weaker on 1938 December 12/13, as Millman said his highest hourly rate was 15.60 M. S. Burland and M. M. Thompson (1940) discussed observations made at David Dunlap Observatory and Newmarket in Ontario, Canada on 1939 December 11/12. Only 12 Geminids were seen in 90 min at the former location and 42 were seen during 240 min at the latter, indicating the best hourly rates were 10–11.61 From the previous paragraphs, it can be seen that there were really no long-term, coordinated observations of the Geminids. The fi rst consistent observations actually came from the Jodrell Bank Experimental Station (England) starting in 1946, as they detected the ionization trails of meteors using radio equipment. They noted maximum hourly rates of 53 on 1946 December 14 (l = 261.4°), 57 on 1947 December 14 (l = 261.3°), 56 on 1948 December 13 (l = 261.1°), 40 on 1949 December 13 and 14 (l = 260.8–261.8°), and 79 on 1950 December 13 (l = 260.5°). The equipment improved during those years, with radiants being determined in 1949 and 1950. In 1949, the radiant moved from a = 108°, d = +33° on December 8 to a = 114°, d = +34° on December 15. In 1950, the radiant moved from a = 107°, d = +37° on December 7 to a = 115°, d = +31° on December 14.62 Meteor radars also became operational at Ottawa (Canada) and Ondrejov Observatory (Czech Republic) in the late 1950s. In a paper published by A. Hajduk, 318 13 December Meteor Showers

B. A. McIntosh, and M. Simek (1974), it was demonstrated that the maximum rates do vary from year to year. The Ottawa observations spanned 1958–1971, with adjusted shower rates ranging from 86 to 245. The Ondrejov observations spanned 1959–1969, with adjusted shower rates ranging from 49 to 214. The differences in the numbers between the two radar facilities were due to differences in the equipment. The 1958 rate of 245 for the Ottawa facility was unusually high, and the authors said this was not because of a change in the sensitivity of the equipment. They noted that observers at Skalnate Pleso Observatory also noted an unusually high number of visual meteors on 1958 December 12/13, so the “anomalously high rate” was considered valid.63 The International Meteor Organization (IMO) was formed in 1988 and improved the way visual observations of meteor showers could be analyzed. The ﬁ rst analysis of the Geminids under the IMO banner was by P. Roggemans (1989). A total of 14,193 Geminids were counted by IMO members during the 1988 display, which indicated a secondary ZHR maximum of 50 meteors per hour on December 11 ( l = 259.9°) and a primary ZHR maximum of 120 meteors per hour on December 13 (l = 261.38°). 64 Additional analyses of annual Geminid rates spanning 1990– 2012 reveal ZHRs of 108–140. Analyzing data collected by the Canadian Meteor Orbit Radar (CMOR) from 2002 to 2008, P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert (2010) found 1038 meteor orbits from this stream. They noted a duration of November 22–December 25 (l = 240–273°) and said the shower peaked on December 13 ( l = 261°), when the radiant was at a = 112.5°, d = +32.1°. The geocentric velocity was 34.5 km/s, while the daily motion of the radiant was determined as +1.12° in a and −0.17° in d .19

Geminids 160

140

120

100 Z H 80 R 60

0 232 242 252 262 272 282 292 Solar Longitude

This represents over a decade of observations of the Geminid meteor shower. The observations were made by members of the International Meteor Organization during the 2000s and 2010s. The solar longitude basically represents 60 days, illustrating the fairly rapid buildup and even quicker decline from a very strong maximum Geminids 319

Table 13.1 Geminid radiant ephemeris Date RA (°) Dec (°) Nov. 25 91 +34 Nov. 27 93 +34 Nov. 29 96 +34 Dec. 1 98 +34 Dec. 3 101 +33 Dec. 5 104 +33 Dec. 7 106 +33 Dec. 9 109 +33 Dec. 11 111 +32 Dec. 13 114 +32 Dec. 15 116 +32

Analysis

As with many meteor showers, the fi rst person to begin analyzing the visual data was Denning. As early as 1885, Denning suspected that the radiant moved slightly as each day passed, and, in 1923, he published a radiant ephemeris (see Table 13.1 ). 65 His analysis revealed a daily motion of +1.25° in a and −0.10° in d. King (1926) essentially con fi rmed Denning’s fi ndings as he published an ephemeris that revealed a daily motion of +1.23° in a and −0.10° in d . 66 Despite the fact that two researchers had arrived at similar conclusions, the matter of the motion of the radiant was disputed by V. A. Malzev (1931). He criticized King’s conclusions— claiming an inadequate treatment of the basic data. His subsequent ephemeris revealed a daily motion of +1.05° in a and −0.06° in d . 67 The general correctness of Malzev’s daily motion has since been con fi rmed by A. F. Cook. Cook published a paper in 1973 which examined photographic meteors. It revealed a motion of +1.02° in a and −0.07° in d . 68 Visual observations have shown this shower to possess a very sharp peak of activity, with hourly rates remaining above a value of half the maximum for about 2 days. 69 Although visual evidence of this shower indicates activity persists from December 6 to 19, de fi nite photographic members of this shower have been detected as early as December 4,70 while radar studies have shown activity as early as November 30 and as late as December 29.71 One of the most complete studies of the average magnitude of the Geminid shower was conducted in 1982 by G. H. Spalding. Using meteor magnitude estimates made by members of the British Astronomical Association during the period 1969–1980, Spalding showed that for solar longitudes of 254–255° (December 7) the magnitude is about 2.14. It brightens slightly to 1.63 by the time the sun reaches longitudes of 256–257° (December 9), then proceeds to steadily fade to a magnitude of 2.41 at longitudes of 260–261° (December 13). Maximum occurs shortly there- 320 13 December Meteor Showers after, and the magnitude brightens during the next several days, so that by the time of solar longitude 265–266° (December 18), the average magnitude is near 1.60. Spalding said “in the two days before maximum there is a moderate concentration of small particles, but … the Earth then moves into a region of larger particles.”72 In 1984, P. B. Babadzhanov and Y. V. Obrubov also stressed the correlation between the solar longitude and the magnitude of the meteors. According to their calculations, which they say agree with observations, they found that meteors of magnitude 6 reach maximum at a solar longitude 0.9° earlier than the maximum of meteors of magnitude 1. Meteors of magnitude −4 tend to reach maximum 1.3° later than meteors of magnitude 1.73 This survey tends to confi rm the British study, except for the fact that Spalding said the Geminids produced brighter meteors on December 9 than on the 7th or 13th. Roggemanns (1989) published an extensive analysis of the visual observations of the 1988 Geminids. Although the population index (r) seems to have varied from day to day, Roggemans wrote, “we cannot con fi rm this [because] too few observers reported the Geminid and sporadic magnitude distribution per date.”64 This changed for the 1990 Geminids, when Roggemans produced a table of 35 r value calculations. This revealed smooth increases and decreases in the r value beginning with 2.50 at l = 256.41°, increasing to 2.63 at l = 260.82°, decreasing to 2.27 at l = 263.51°, and then slightly increasing to 2.29 by l = 265.01°. 74 Although the population index variations have not been the same for every return of the Geminids, the variations are nevertheless present. J. Rendtel (2004) studied the visual observations of the Geminids from 1955 to 2002, noting a shift in the time of maximum amounting to 0.008° per year in solar longitude. He also noted the typical peak ZHR is slightly higher than 140 from 1988 to 1997.75 A major advance in the understanding of the already mentioned intricacies of this meteor stream was made in 1947. F. L. Whipple had been involved in the Harvard Meteor Project, a photographic survey aimed at better understanding meteors and their origins by obtaining data that could be used to calculate orbital elements. While analyzing meteors associated with the Geminids he found an orbital period of only 1.65 years, as well as a high eccentricity and a low inclination.76 Such an orbit attracted the attention of M. Plavec (1950), who began investigating the effects of perturbations on the orbit. Plavec found that only two planets affect the orbit of the Geminids—Earth and Jupiter, though the former was considered negligible compared to the effects of the giant planet. “From the observer’s point of view,” he wrote,“ the most important phenomenon is the rapid backward shift of the node.” The degree of this shift was calculated to cause the date of maximum to occur 1 day earlier every 60 years. Another interesting conclusion involved the point of intersection between the stream’s orbit and the ecliptic. For the year 1700, it was found that the intersection point was placed 0.1337 AU inside Earth’s orbit. For 1900, the intersection point was located 0.0178 AU inside Earth’s orbit and in 2100, the point would be 0.1066 AU outside of Earth’s orbit.77 Thus, Plavec not only showed why the activity of the Geminids was steadily increasing, but he also demonstrated that the activity Geminids 321 would eventually decline and that sometime in the future Earth would no longer contact the stream’s orbit. Despite Plavec’s calculations, the history of the Geminid stream was still uncertain. In 1967, during the International Astronomical Union’s Symposium No. 33, I. S. Astapovich and A. K. Terentjeva submitted a paper titled “Fireball Radiants of the 1st-15th Centuries.”78 They discussed their determination of the radiants of 153 meteor showers. According to their fi ndings, a total of 14 fi reballs were detected between the years 1038 and 1099 from a radiant similar to the Geminids, while additional fi reballs were noted in 381 and 1163. They remarked that the “ fi reballs of the eleventh century gave a de fi nite radiant a = 103°, d = +26° (December 6–18).” They said the eleventh century radiant was situated south and east of the present radiant and added “apparently there has occurred a secular increase of the orbital inclination and a change in the line of apsides.” They added, “the node of the orbit remained practically unchanged in the course of nine centuries.” The possible age of the Geminid stream has attracted a lot of attention. J. Jones (1978) looked at two aspects. First, he determined the period of the Geminids as 1.49 years and said it would take 3,000 years for the material from a “now vanished parent comet” to be evenly dispersed around the orbit. Second, he noted a “systematic change of orbital parameters with meteor magnitude,” which he said could be due to the Poynting-Robertson effect. He suggested such a separation would indicate an age of 4,700 years.79 Babadzhanov and Obrubov (1983) modeled the Geminid mass distribution, including nongravitational effects due to solar radiation pressure. In order to account for the observed mass distribution, they suggested it would take 1,600 years for small particles and up to 19,000 years for the largest particles.80 E. N. Kramer and I. S. Shestaka (1986) conducted a secular perturbation analysis for a period of 4,000 years and concluded that the age of the “swarm” that is connected to the minor planet Phaethon (see below) “does not exceed 1,000 years, and the swarm will remain as compact as it is for 400 years more.” 81 G. O. Ryabova (1989) studied fi rst-order secular perturbations and the Poynting- Robertson effect and estimated the age as 2,000 years.82 Ryabova (1999) produced a new model, which included solar wind drag and secular variations and determined the age as 10,000 years.83 M. Beech (2002) examined fi reball fl ickering as a method of determining the age of the Geminids. He estimated “the time required to spin-up a meteoroid through non-isotropic photon scattering interactions with the solar radiation fi eld ….” He found meteoroid ejection times occurred 1,000–4,000 years ago and added, “There appears to be some indication that the stream formation process lasted for at least ~1,000 years.”84 Jones (1982) examined the annual variation in the activity levels of the Geminids, which he said amounts to 30 %. After presenting the results of his calculations, he concluded that the Geminid stream contains “a number of distinct streamlets.” He added, “Comparison with the theory of ejection of dust from comets indicates that the cometary fragments from which these streamlets were formed probably were covered by an insulating layer which greatly attenuated the emission of particles at perihelion.” He said it could take 100 years of observations “to resolve signifi cant structure in the activity power spectrum.”85 322 13 December Meteor Showers

K. Fox, I. P. Williams, and D. W. Hughes (1982) published a paper titled, “The evolution of the orbit of the Geminid meteor stream.”86 They essentially con fi rmed Plavec’s fi ndings of a nodal retrogression rate of about 1.6°/century, as well as his recognition of the relative newness of the shower in historical records—thus, eliminating the link to the fi reballs of the eleventh century (see the December Monocerotids). However, the confi rmation of the nodal retrogression rate led to a problem: the observations did not confi rm the predicted change in the date of maximum that amounted to 1 day in about 60 years. The authors theorized that the predicted change was actually being altered and proceeded to analyze several possibilities. Since the orbit of the Geminid stream passed through the asteroid belt, the British researchers looked for an asteroid that may periodically pass near the stream’s orbit. They found that asteroid 132 Aethra actually passed only 0.0003 AU from the Geminid orbit; however, they quickly discovered that for the asteroid to account for the variations noted would require it to possess a mass only slightly less than that of Jupiter! Another possibility was that of general relativity—an effect noted in several planetary orbits—but the result of the calculations was a slight increase in the nodal retrogression rate, rather than the expected slowing down. The fi nal possibility considered was “the shape of the cross-section of the intersection of the meteor stream with the ecliptic plane.” A computer simulation predicted “that the meteor rate profi le is skew.” Fox, Williams and Hughes further elaborated on this distribution in a paper published in 1983. “At the present time the Geminid shower slowly builds up to maximum rate and then drops away from maximum relatively sharply. About 50 years ago the skewness should have been exactly the opposite with a sharp build up to maximum rate and a much slower falling away.” The proposed model indicated Earth’s orbit would intersect the Geminid stream only between 1800 and 2100. It also explained the currently observed mass segregation within the stream.87

Association

A major question concerning the Geminid stream involves its origin. It was long known that no parent comet for this stream was present in current catalogs, but, since the exact size and shape of the stream were not known until 1947, few conjectures were made. In 1950, Plavec theorized about the Geminid stream’s parent body and pointed out that the “existence of a parent comet in such a short-period orbit, even in the past, seems to be not very probable. Planetary perturbations could scarcely have reduced the semimajor axis so much. More probably, the Geminids were separated from a parabolic comet by the close approach of the comet to the sun.”77 Concerning a possible candidate for the parabolic comet mentioned, Plavec considered the great comet of 1680 (after a suggestion made in 1931 by Malzev) and concluded that the close approach of the two orbits at a point slightly beyond the Geminid perihelion point made a possible connection impossible to exclude. Geminids 323

L. Kresák strengthened the comet link to this meteor stream’s formation, but instead of offering a theory as exotic as Plavec’s, he favored a more direct formation of the Geminids. In 1972, he wrote that the parent comet “must have previously occupied the present orbit.”88 He stressed that the compact nature of the stream would eliminate the possibility of it having formed in a different orbit and then been perturbed into the present orbit. Eleven years later, Kresák’s theory would gain considerable strength. On 1983 October 11, during a search for moving objects amidst the data gathered by the Infrared Astronomical Satellite (IRAS), S. Green and J. K. Davies found a rapidly moving asteroid in Draco. The next evening, C. T. Kowal (Palomar Observatory, California, USA) confi rmed the body by photographing it with the 122 cm Schmidt telescope. The asteroid received the preliminary designation 1983 TB. As early orbital calculations were being made, the International Astronomical Union Circular for 1983 October 25 relayed the opinion of Whipple that this asteroid’s orbit was almost identical to that of the Geminid meteor stream.89 Additional observations confi rmed the link and the asteroid eventually received the permanent designation of 3200 Phaethon. The excitement of having found the parent body of the Geminid stream was almost dwarfed by another realization—this was the fi rst time an asteroid had been defi nitely linked to a meteor shower and it subsequently serves as an important link between comets and meteor streams.

Origin of the Meteor Stream

A few papers have been published that examine the formation of the Geminids by the minor planet Phaethon. J. Hunt, K. Fox, and I. P. Williams (1986) presented a model based on the assumption that Phaethon was not an extinct comet nucleus. They said their trials indicated “that the best cross-section shape was obtained when the collision point was close to the aphelion of the orbit” of Phaethon, while the “best results were obtained when the maximum ejection speed was” about 200 m per second. They concluded “that the asteroid model is capable of reproducing the correct cross- section for a stream but has diffi culty in matching the distribution of aphelia.” To account for this, they said the stream “must be old enough for planetary perturbations to cause a signi fi cant change in the aphelion distance of the orbits, though this is dif fi cult since the major perturbations will be occurring near aphelion.”90 Ryabova (1989) presented a model of a collision of an asteroidal object in the Geminid orbit. A total of 1,000 particles were ejected along a cone. She wrote, “the velocity and cone’s angle distributions for particles of several masses were based on published experimental and theoretical data on impacts, collisional breakups and explosions. It was found that the structure of the model stream cross-section by ecliptic plane does not agree with the Geminid shower observed structure. So collisional origin of the Geminid meteoroid stream was discarded.”91 324 13 December Meteor Showers

Orbit

The orbit labeled “1937–1977” is based on 37 photographic meteor orbits acquired from various sources. The orbit labeled “1949–1950” is from Hawkins and Almond (1952). The orbit labeled “2002–2008” is from Brown et al. (2010). The orbit labeled “3200” is that of the Apollo asteroid Phaethon.

w W (2000) i q e a 1937–1977 324.1 262.0 23.9 0.143 0.896 1.61 1949–1950 325 261.8 23 0.14 0.89 1.31 2002–2008 324.95 261.0 23.2 0.1373 0.898 1.35 3200 322.15 265.27 22.24 0.1399 0.8899 1.27

Sigma Hydrids

Duration : December 3 to December 15 (l = 251–263°) Maximum : December 12 (l = 260°) Radiant : a = 127°, d = +2° ZHR : 3

Radiant Drift : a = UNK, d = UNK V G : 58 km/s The discovery of this stream should be attributed to R. E. McCrosky and A. Posen (1961). They published a list of 2,529 photographic meteor orbits that had been computed from double-station photographs obtained during the Harvard Meteor Project of 1952–1954 and identi fi ed seven of these meteors as emanating from a radiant near the star Sigma Hydri.92 Later that year, L. G. Jacchia and F. L. Whipple (1961) published an analysis of 413 precise photographic orbits also obtained during the Harvard Meteor Project and identifi ed three meteors as belonging to this stream.93 The average radiant indicated by the precise orbits was a = 126.7°, d = +1.8°. Con fi rmation of a December shower from this radiant was made by observers at Waltair, India, during a survey for minor meteor showers conducted by M. Srirama Rao, P. V. S. Rama Rao, and P. Ramesh from 1961 to 1967. From 1963 December 12 to 15, fi ve meteors were detected from a = 127°, d = +4°. It was calculated that the radiant had an hourly rate of 6.6. From 1964 December 11 to 14, the radiant was again detected. On this occasion 31 meteors emanated from a = 123°, d = +7°. The hourly rate was given as 6.0.94 A search through previously published accounts listing visual radiants reveals occasional indications of this shower’s presence in the latter half of the nineteenth century and well into the twentieth century. But the most striking series of observations extracted from these older records are the 1937 observations made by C. Hoffmeister in South-West Africa (now Namibia). The radiants were designated 4582, 4612, 4621, 4642 and 4668 and were all detected between December 6 and 13. The fi ve radiants indicate an average radiant at a = 129°, d = +3°. Sigma Hydrids 325

Observations by members of the National Association of Planetary Observers Meteor Section in Australia have revealed activity during the period December 3–19, with a maximum ZHR of 3–5 meteors radiating from a = 128°, d = +4° on December 11.95 In 1978, the same group monitored this shower from December 2 to 10. They found the hourly rate to be highest on the latter date at 5. Based on the 49 meteors observed, the average magnitude was determined as 3.06, while 6.1 % of the meteors left persistent trains. The meteors were said to have a “Perseid type velocity” and 21.4 % were yellow.96 On the whole, northern hemisphere observers have rarely observed rates greater than one meteor per hour; however, in 1983, N. W. McLeod, III (Florida, USA) noted rates rose to 6 per hour on December 8/9, and were still at 4 per hour on December 10/11.97 From 1982 December 10/11–13/14, R. Lunsford (California, USA) determined the average magnitude of the Sigma Hydrids as 3.6.98 On 1993 December 11.59, a magnitude −8 ﬁ reball was seen over Japan, which was photographed from two different locations. C. Shimoda, K. Ohtsuka, T. Nakagawa, and Y. Shiba (1994) analyzed the two images and concluded the meteor came from the Sigma Hydrid stream, with the radiant being determined as a = 128.84°, d = +1.66°. The geocentric velocity was determined as 58.8 km/s.99 Y. Shigeno and M.-Y. Yamamoto (2012) analyzed 3770 double-station video observations of meteors seen over Japan from 1992 to 2009. The Sigma Hydrids were at maximum on December 15 (l = 262.85°) from a radiant at a = 130.4°, d = +1.5°. The geocentric velocity was 57.7 km/s.100 The orbit labeled “Photo” is based on eight photographic meteors collected from astronomical papers published from 1954 to 1976. The orbit labeled “Fireball” was the orbit determined by Shimoda et al. (1994). The orbit labeled “1992–2009” is from Shigeno and Yamamoto (2012).

w W (2000) i q e a Photo 120.6 79.6 127.5 0.248 0.991 26.05 Fireball 119.8 79.648 129.3 0.256 0.977 11.49 1992–2009 125.3 82.9 126.8 0.217 0.978 9.76

Using an orbit similar to the photographic orbit above, K. Fox (1986) integrated the orbit of this stream backward and forward for 1,000 years.101 The following two orbits were obtained:

w W (2000) i q e a 950 120.5 78.8 125.6 0.25 0.99 29.28 2950 121.5 81.7 124.0 0.25 0.99 30.13 326 13 December Meteor Showers

The orbit of the Sigma Hydrids thus seems fairly stable. In 950, the date of maximum was unchanged from that of the present, while the radiant position was a = 125.8°, d = +1.1°. In 2,950, maximum will occur about 1 day later than at present and the radiant will be at a = 127.0°, d = +1.6°.

December Monocerotids

Duration : November 27 to December 17 (l = 245–265°) Maximum : December 9 (l = 257°) Radiant : a = 101°, d = +09° ZHR : 2

Radiant Drift : a = +0.95°, d = −0.03° V G : 22 km/s F. L. Whipple (1954) discovered this meteor stream during a search through 144 meteor orbits detected during the photographic surveys of Harvard College Observatory from 1936 to 1951. Two meteors had been photographed on 1950 December 13 and 15, which moved in very similar orbits that indicated an average radiant of a = 103°, d = +8°. 102 What made the fi nd especially signifi cant was the fact that the indicated orbit was very similar to that of comet C/1917 F1 (Mellish)—a comet with an orbital period of about 145 years.103 R. E. McCrosky and A. Posen (1961) published a list of 2529 meteor orbits obtained from 1952 to 1954 by the Harvard Meteor Project. They found three meteors that they said belonged to the “Monocerotid” stream. The meteors were photographed between December 10 and 17. 104 The radiant was a = 103.7°, d = +9.7° and the geocentric velocity was 42.5 km/s. Further details came forth in the 1960s, as four major radar surveys provided additional details on this meteor stream. C. S. Nilsson (1964) analyzed the data acquired from 1960 to 1961 by the radio equipment at University of Adelaide (South Australia, Australia). Although the computer technique designed to process the 2101 radar meteor orbits did not reveal a stream with the orbit determined by the photographic data, Nilsson studied the radiant data and located two meteors in 1960 December and six meteors in 1961 December. The latter meteor orbits allowed a good determination of the stream’s orbit. It also indicated a duration of December 5–12, with an average radiant of a = 101.6°, d = +9.6°. Interestingly, Nilsson’s computer technique did reveal a stream in both 1960 and 1961, which possessed a similar orbit to the photographic determinations, but with an inclination some 10–15° lower. This resulted in an average radiant of a = 95°, d = +15°—meaning it was shifted nearly 9° to the northwest. What made this stream particularly signifi cant was the fact that it seemed to possess a twin from September 23–29, at a = 162°, d = +14°. Nilsson noted that “care must be taken not to confuse the separate and newly determined radiant at 95°, +15° with the Monocerotid radiant at 102°, +10°. The values of geocentric velocity are similar, and the orbit of the former is also near parabolic; however, the inclination of the orbit is defi nitely smaller than that of the Monocerotid stream.” He added the similarity of the orbits might suggest a connection.105 December Monocerotids 327

Z. Sekanina (1973) published the results of the Radio Meteor Project conducted at Havana, Illinois, from 1961 to 1965. This project revealed a very distinct stream with an average radiant at a = 91.4°, d = +15.0°—very similar to the strong, lower inclination stream noted by Nilsson. Sekanina commented that “the photographic stream associated with P/Mellish has both its mean optical radiant and its theoretical radiant in Monoceros, but the mean radiant of the rich radio stream detected in our sample, which is beyond any doubt also related to the comet, lies in Orion....” A further surprise revealed by this radar study was that the indicated duration of this stream was from November 9 to December 18.106 A further, more sensitive session of the Radio Meteor Project operated in 1968–1969. Sekanina (1976) again found this stream, noting a duration of November 16 to December 14. The nodal passage came on December 4.3 (l = 251.8°) at which time the radiant was at a = 93.8°, d = +14.4°. Due to the similarity of these streams to the meteor orbits found in the photographic studies, Sekanina referred to the streams as the “Monocerotids.”107 G. Gartrell and W. G. Elford (1975) analyzed the data acquired in 1968–1969 by the radio equipment at the University of Adelaide. They wrote, “Although no Monocerotids were found to be associated by the systematic stream searches, three meteors were observed with radiants and velocities corresponding to this stream.” Designated stream 60.12.09, the mean date was determined as December 15 and the radiant was at a = 106°, d = +6°. 108 K. Ohtsuka (1989) searched through published catalogs of photographic meteors and found 15 probable members of this stream. The duration was December 12–13, while maximum occurred on December 11 ( l = 260.2°) from a radiant at a = 102.0°, d = +8.3°. The geocentric velocity was 41.6 km/s. The daily motion of the radiant was determined as +0.95° in a and −0.03° in a . 109 Y. Shigeno and M.-Y. Yamamoto (2012) analyzed 3770 double-station video observations of meteors seen over Japan from 1992 to 2009. The December Monocerotids were at maximum on December 12 (l = 260.51°) from a radiant at a = 102.1°, d = +7.8°. The geocentric velocity was 40.1 km/s. The fi rst study of this meteor stream was conducted by M. Kresáková in 1974, as she studied comet Mellish and its possible relationship to the Geminids. 110 While studying comet Mellish and the lists of photographic meteors, it was noted that two apparent minor streams were present. The fi rst was referred to as “long-period component A”, and possessed nearly identical orbital elements to the Monocerotids fi rst suggested by Whipple. It was based on 16 meteors acquired from both American and Russian sources. The second stream was composed of nine photographic meteors and was later identi fi ed with the 11 Canis Minorids fi rst announced by K. B. Hindley in 1969 (see the 11 Canis Minorids earlier in this chapter). The Monocerotids of Kresáková lay very close in radiant position to that predicted for P/Mellish. A preliminary examination of previously known data by the author had seemed to indicate two distinct streams being present with a separation of about 10° in inclination; however, the photographic meteors listed by Kresáková and the original radar orbits acquired during the two Radio Meteor Projects directed by Sekanina, seem to show no sign of distinct streams, but, instead, one very diffuse stream. 328 13 December Meteor Showers

Nevertheless, one cannot ignore the fact that photographic and radar studies tend to indicate distinctly different orbital inclination averages. Thus, it would seem that the fainter and smaller radar meteors tend to possess more lower inclination orbits than the brighter, larger photographic meteors. Meteor showers visible to the naked eye will probably originate from the photographic radiant, while telescopic meteors will tend to lean toward the radar radiant. Based on the number of meteors detected both by photographic and radio-echo techniques, it would seem the Monocerotid shower may be stronger telescopically than visually. Coordinated attempts to observe this stream visually have never been conducted, but Meteor News published details of many individual attempts to observe this shower between 1977 and 1985 (see issues 40, 49, 53, 57, 61, 65, 68 and 73). Typical observations indicate hourly rates of only one to two per hour. From 1982 December 11 to 14, R. Lunsford (San Diego, California) observed ten Monocerotids and gave the average magnitude as 3.2. 111 Surprisingly, the December Monocerotids may be responsible for the solving of a major puzzle in meteor astronomy. During the International Astronomical Union’s Symposium No. 33 in 1967, I. S. Astapovich and A. K. Terentjeva submitted a paper entitled “Fireball Radiants of the 1st-15th Centuries.”112 They discussed their determination of 153 meteor radiants and pointed out a collection of 14 fi reballs that emanated from a radiant similar to that of the Geminids during the years from 1038 to 1099. They remarked that the “fi reballs of the eleventh century gave a de fi nite radiant a = 103°, d = +26° (December 6–18), the early fi reball of 381 December 13 passing 5° to the South of it.” Their linking of this fi reball radiant to the Geminid shower has caused much controversy (see the Geminids earlier in this chapter), but in 1985, K. Fox and I. P. Williams offered a reasonable solution. Beginning with an orbit possessing the angular elements determined by Kresáková and borrowing the semimajor axis of comet Mellish, Fox and Williams examined the orbital evolution of a particle between 783 AD and 3183 AD.113 Perturbations from Jupiter, Saturn, Uranus, and Neptune were taken into account. Their results were that the ascending node varied by less than 5° during the 2,400 years examined, while the nodal distance from Earth’s orbit “remained fairly constant.” The fi nal conclusions of the study indicated that “a Monocerotid shower would still be seen during December in the eleventh century,” as well as 1,000 years from the present time. Also, Fox and Williams showed that, of the currently known meteor showers, only the Monocerotids were capable of producing a shower close to the radiant of the eleventh century fi reballs, though “there is always the possibility that the ancient fi reballs came from a stream which is not observable at present.” I. Hasegawa (1999) examined Chinese historical records for previous appearances of the December Monocerotids. He began with the accepted orbit for comet C/1917 F1, which has a period of 145 years, but with an uncertainty of 6 months. He found several accounts, mostly of fi reballs, that occurred around the time expected to qualify as belonging to this meteor shower. The earliest was on 381 November 20 ( l = 262.1°), when a meteor appeared in the southeast and fl ew through the Chinese constellations Yi and Zhen with sound.114 Note that it would Chi Orionids 329 be impossible to state that these individual meteors are December Monocerotids; however, Hasegawa provided plots of these historical fi reballs and, as a whole, an argument could be made that the December Monocerotids were active in ancient and medieval times. The orbit labeled “1950–1962” is from Kresáková (1974). The orbit labeled “1950–1985” is from Ohtsuka (1989). The orbits labeled “1960” and “1961” are from Nilsson (1964). The orbit labeled “1968–1969” is from Sekanina (1976). The orbit labeled “1992–2009” is from Shigeno and Yamamoto (2012). The orbit labeled “C/1917 F1” is that of comet Mellish.

w W (2000) i q e a 1950–1962 133.7 75.1 29.4 0.154 1.000 ∞ 1950–1985 128.9 80.8 34.9 0.188 0.991 19.88 1960 131.5 77.3 18.7 0.2 0.99 20.0 1961 135.3 74.6 22.6 0.11 0.99 11.1 1968–1969 135.8 72.5 22.3 0.153 0.975 6.20 1992–2009 128.3 80.3 33.8 0.199 0.973 7.29 C/1917 F1 121.32 88.67 32.68 0.1902 0.9931 27.65

Using the orbit of comet Mellish, Fox (1986) computed the orbit of the December Monocerotid stream for periods 1,000 years in the past and future with the following results:115

w W (2000) i q e a 950 121.8 87.6 32.8 0.19 0.99 27.29 2950 119.9 90.7 32.4 0.19 0.99 27.30

In 950, the shower’s maximum would have occurred only one-half day earlier than at present from a radiant of a = 102.0°, d = +6.0°. In 2950, maximum will occur 1.1 days later than at present, with the radiant being a = 103.3°, d = +5.2°. As can be seen, the orbit of comet Mellish is very stable, so any associated stream must also be stable.

Chi Orionids

Northern Branch Duration: November 16 to December 16 (l = 234–264°) Peak: December 10 (l = 258°) @ a = 82°, d = +23°

Radiant Drift: a = UNK, d = UNK V G : 23 km/s 330 13 December Meteor Showers

Southern Branch Duration: December 2 to December 18 (l = 250–266°) Peak: December 10 (l = 258°) @ a = 88°, d = +20°

Radiant Drift: Unknown V G : 22 km/s The Chi Orionids have been around for at least 100 years, though its weak activity at a time when the Geminids are nearing prominence should probably be blamed for its frequently being overlooked by observers. But this stream occasionally gets the attention of even casual observers because it is a source of slow-moving fi reballs. The earliest observations were made by W. F. Denning (Bristol, England), who plotted 20 meteors from 1876 November 22 to December 8, giving the radiant as a = 80°, d = +23°, and noting a maximum on December 6. He named this radiant “Taurids II” and described the meteors as bright and very slow.116 Denning plotted six meteors from 1877 November 25 to December 13 from a = 80°, d = +25°. He again referred to the radiant as “Taurids II” and again described the meteors as very slow. 117 Denning’s “Taurids II” radiant was con fi rmed by E. F. Sawyer (Cambridge, Massachusetts, USA). He plotted ten meteors from 1877 November 30 to December 9 from a radiant of a = 80°, d = +22°. Sawyer added that the meteors were “generally quite bright.”118 Sawyer plotted fi ve meteors from 1879 December 7 to 12, from a = 82°, d = +23°. He described them as “rather bright, of medium length and velocity.” Five meteors were also plotted during 1880 November 21–28, which indicated a radiant of a = 81°, d = +23°. He said the meteors were “rather bright, of medium length, and slow.” 119 H. Corder (Writtle, England) plotted meteors from 1876 to 1879 and found a radiant at a = 78°, d = +23° during December 10–13.120 Denning published a paper titled “The Radiant Points of Fireballs” in 1884 April. He basically took his plots of meteors that were equal to or brighter than Jupiter and combined them with plots from other observers. A total of 37 radiants were identi fi ed. Radiant 36 was given a duration of December 6–8 and a position of a = 81°, d = +23°. 121 Despite the confi rming observations of this meteor shower, few observations were made during the remainder of the 1880s. Denning included three radiants from this shower in his list of 918 radiants that was published in the Monthly Notices of the Royal Astronomical Society in 1890. The fi rst two were his observations from 1877 to 1878, while the third was from his observations made from 1885 November 30 to December 10. During this last period, Denning plotted 11 meteors from a radiant of a = 88°, d = +19°. He described the meteors as “slowish” and said the most active date was December 7.122 This last radiant appears to be the very fi rst observation of the Southern Chi Orionids, with all previous observations referring to the northern branch. In addition, during 1899, Denning combined meteor plots obtained by E. Weiss (Hungary), G. Zezioli (Bergamo, Italy), and himself, which extended back to the late 1870s and found 17 meteors that emanated from a radiant at a = 86°, d = +19° during December 9–13. He called this meteor shower the Chi Orionids.123 Chi Orionids 331

It is uncertain whether any observations of this radiant were made in the 1890s. The Memoirs of the British Astronomical Association reported three radiants, which were 8–10° north of the expected radiant of the Chi Orionid branches. Corder (Bridgwater, England) and J. T. Pope (Dingwall, England) spotted seven slow meteors from a radiant at a = 81°, d = +30° on 1892 December 9.124 E. R. Blakeley (Dewsbury, England) and Corder spotted six slow meteors from a = 80°, d = +28° from 1895 December 10 to 15. 125 Corder reported 12 slow meteors were observed from a = 80°, d = +29° in 1896 December.126 The Southern Chi Orionids were not well observed during the fi rst half of the twentieth century, but numerous observations were made of the northern branch. Most notable was the inclusion of the Northern Chi Orionid radiant in a table of “third grade radiants” in C. Hoffmeister’s 1948 book Meteorströme . Ten radiants were isolated which were active around December 11 (l = 259°) from an average radiant of a = 83°, d = +22°. 127 The examination of these radiants revealed an average diameter of 3°. Interestingly, the Chi Orionids are not prominent among thousands of radiants reported to the American Meteor Society, with only one or two radiants appearing every decade from the 1920s through the 1960s, although a couple of these radiants are from well-observed fi reballs. From 1977 through 1980, the Western Australia Meteor Section (WAMS) plotted meteors during the fi rst half of December and detected both branches of this stream each year. The duration of the northern branch was determined as December 2–16, while the duration of the southern branch was determined as December 5–15. The northern branch peaked during December 11/12, while the southern branch peaked during December 9/10. They found the maximum ZHR varied year to year from 2 to 4. WAMS also found that the Chi Orionids produced fairly bright meteors, with an average magnitude of 1.60, while 14.3 % of the meteors produced trains. 14 Photography played an important role in understanding this meteor shower, as it did with other meteor showers; however, there was an unexpected result in that the Southern Chi Orionids were more plentiful than the Northern Chi Orionids. B. A. Lindblad (1971) applied computer analysis to 2401 photographic meteor orbits acquired during the Harvard Meteor Project (1952–1954). The southern branch was represented by eight meteors detected from a radiant of a = 85°, d = +16° from December 7 to 14. The northern branch was represented by four meteors detected from a radiant of a = 83°, d = +26° from December 4 to 13. Both branches had a geocentric velocity of 28 km/s.128 Further examination of the photographic meteor orbits obtained in the 1940s, 1950s, and 1960s, in the United States and Soviet Union, has led to more re fi ned orbits for each branch of the Chi Orionid stream using stricter values of the D-criterion than used by Lindblad. The southern branch was again best represented with 12 meteors. The stream’s duration was December 4–14, while the average radiant was a = 83.9°, d = +16.8°. Curiously, the stricter D-criterion shortened the duration of the northern branch to December 11–17. The average radiant was a = 84.4°, d = +26.1°. 332 13 December Meteor Showers

The most impressive fi reball recorded from the Chi Orionids stream came from the northern branch on 1974 December 4. Z. Ceplecha analyzed the images acquired by the European Network of All-Sky Cameras and found the maximum magnitude reached −21, while the original mass was estimated as 100,000 kg (110 t). The meteor fi rst appeared at an altitude of 99 km and was last detected at an altitude of 55 km. The radiant was determined as a = 77.0°, d = +25.6° and the geocentric velocity was determined as 24.3 km/s. Radio-echo surveys conducted during the 1960s were successful in detecting the Chi Orionids, but not in isolating both the northern and southern branches at the same time. C. S. Nilsson (Adelaide Observatory, South Australia, Australia) detected four radio meteors from 1960 December 7 to 12, which came from a radiant of a = 80.0°, d = +16.8° and had a geocentric velocity of 21.5 km/s, indicating an observation of the southern branch. 129 Z. Sekanina detected the Chi Orionids during both sessions of the Radio Meteor Project. During the 1961–1965 session, the duration was given as December 2–18. The date of the nodal passage was given as December 9.9 (l = 257.5°), at which time the radiant was at a = 87.1°, d = +20.6° and the geocentric velocity was 25.2 km/s.130 This radiant represents the southern branch. The 1968–1969 session indicated a duration of November 16–December 16. The date of the nodal passage was given as December 9.9 (l = 257.5°), at which time the radiant was at a = 81.5°, d = +23.4° and the geocentric velocity was 22.2 km/s. 107 This radiant represents the northern branch. It is interesting to note that neither branch of the Chi Orionids was detected during the studies published in 2008 and 2010 from the Canadian Meteor Orbit Radar. The Chi Orionids were mentioned in a couple of papers published in 1979 and 1982. These papers pointed out the fact that the Chi Orionids were one of two meteor streams that have produced a signi fi cant number of fi reballs, with the other being the Taurids. J. T. Wasson and G. W. Wetherill (1979) provided a table which showed that photographic fi reball surveys have detected fi ve defi nite fi reballs and a possible sixth from the Northern Chi Orionids from 1961 to 1975, while three others came from the Southern Chi Orionids from 1947 to 1966. Wasson and Wetherill wrote, “Fragments of extinct comets are not con fi ned to small meteors. Large objects, kilograms in mass, are associated with these streams. There is even evidence that very large (~100 t) bodies are sometimes found in streams.”131 Wetherill and D. O. ReVelle (1982) noted that the boundaries between the Chi Orionids and Taurids “are not clear.” They added that in the data from the Harvard Meteor Project “the boundary seems de fi ned by an absence of data during the period of 25 Nov.–4 Dec., and thus could be an artifact of the data set used in the statistical identifi cation of streams.”132 J. D. Drummond (1982) published a paper in Icarus that determined the theoretical meteor radiants of Apollo, Amor, and Aten asteroids. For asteroid 2201 Oljato, he noted that it would produce meteors from a radiant of a = 85°, d = +20° from December 12 to 29. Not only did he show the Chi Orionids to be a probable association, his search among 334 fi reballs detected by the Prairie Network from 1963 to 1975 revealed “no less than 11 fi reballs associated with its orbit, six quite closely.” 133 Chi Orionids 333

As noted above, Wetherill and ReVelle suggested a relationship between the Chi Orionids and the Taurids. The Taurids have been found to be associated with a large collection of meteor showers, minor planets, and comet 2P/Encke. The minor planet 2201 Oljato has an orbit that is particularly close to the Chi Orionids. I. Hasegawa, Y. Ueyama, and Ohtsuka (1992) indicated that Oljato would produce a radiant on December 22 (l = 269.8°) from a radiant of a = 86.3°, d = +19.6°.134 The most recent observations of the Chi Orionids have involved double-station video observations. The million-meteor database of the International Meteor Organization’s Video Meteor Network has revealed the Northern Chi Orionids, although they have labeled it as an antihelion radiant. During observations spanning 1993 through 2012, they found that maximum occurs on December 7/8 ( l = 256.0), at which time the radiant is at a = 80.9°, d = +25.5°. Y. Shigeno and M.-Y. Yamamoto (2012) published their meteor stream detections among 3,770 meteors detected from 1992 through 2009. They detected both branches of the Chi Orionids. The northern branch reached maximum on December 11 (l = 260.0), at which time the radiant was a = 86.5°, d = +29.3° and the geocentric velocity was 22.9 km/s. The southern branch reached maximum on December 11 ( l = 259.7), at which time the radiant was a = 80.8°, d = +14.1° and the geocentric velocity was 20.4 km/s. 135 Several orbits have been determined for both branches of the Chi Orionids and photographic meteor orbits have been collected from several sources. The Northern Chi Orionid (N) orbit was based on ﬁ ve meteors, while the Southern Chi Orionid (S) orbit was based on 12 meteors.

w W (2000) i q e a N 275.3 261.9 2.4 0.528 0.739 2.02 S 101.6 78.5 6.0 0.460 0.798 2.28

The stream was also detected during three radio-echo surveys of the 1960s, although the northern and southern branches were not separated. The orbit labeled “1960” is from Nilsson (1964). The orbit labeled “1961–1965” is from Sekanina (1973). The orbit labeled “1968–1969” is from Sekanina (1976). The fi rst two orbits were obviously in fl uenced by the Southern Chi Orionids, while the last orbit was in fl uenced by the Northern Chi Orionids.

w W (2000) i q e a 1960 93.8 79.2 4.6 0.556 0.70 1.85 1961–1965 109.1 78.1 2.6 0.420 0.765 1.79 1968–1969 276.8 260.1 0.2 0.515 0.711 1.78 334 13 December Meteor Showers

The following orbit was that determined for the 1974 European ﬁ reball, which came from the northern branch.

w W (2000) i q e a 1974 281.8 252.64 2.3 0.471 0.76 1.98

Finally, the double-station video observations of Shigeno and Yamamoto produced the following orbits for the northern (N) and southern (S) branches.

w W (2000) i q e a N 282.0 259.9 4.9 0.487 0.723 1.76 S 89.5 79.6 6.2 0.579 0.706 1.97

Phoenicids

Duration: November 28–December 9 (l = 246–257°) Maximum: December 6 (l = 254.25°) Radiant: a = 18°, d = −53° ZHR: Variable

Radiant Drift: a = UNK°, d = UNK° V G : 18 km/s An unexpected, strong display of meteors was observed by both visual and radio-echo means on the night of 1956 December 5. It was seen by observers in New Zealand, Australia, South Africa, and by crewmen on ships in the Indian Ocean. Two amateur astronomers published papers on their visual observations of this outburst in 1957 February. C. A. Shain (Radiophysics Laboratory, Fleurs fi eld station, New South Wales, Australia) was working on the night of December 5. He stepped outside for about 5 min at 11:00 p.m. and for about 15 min at 11:30 p.m. In both instances, he estimated “the observed meteor rate was one or more per minute.” He said the “meteors moved slowly, appearing very bright and yellow; their apparent magnitudes were very roughly estimated to be about −2.” Schain noted that the frequency of the meteors “permitted a fair estimate of the radiant of the shower, about 5° preceding Achernar.” He estimated the radiant as a = 15°, d = −58° and said the error was “probably not more than 5° in each coordinate.”136 S. C. Venter (Pretoria, South Africa) was the director of the meteor section of the Astronomical Society of Southern Africa. Besides personally seeing the meteor outburst on the night of December 5, he also received reports from other people. He commented, “The beauty of this phenomenon and the rarity of its appearance brought astronomer and layman alike out into the open, and, fortunately, many of them began to note the numbers of meteors appearing.” Venter noted the Phoenicids 335 low velocity and said the radiant was located at a high altitude, about 20° from the zenith. He determined the radiant position as a = 15°, d = −46°. Venter said he saw 60 meteors between 6:15 and 10:45 p.m. He noted that of all the observers, G. Bekink was probably experiencing the best conditions, as he was about 10 miles outside of Pretoria. He counted 52 meteors during 6:00–6:30 p.m. and 50 meteors during 7:30–8:00 p.m. Venter wrote, “It is therefore safe to say that the Zenith Hourly Rate of the shower was 100 during the fi rst two hours” after 6:00 p.m.137 H. B. Ridley (1957) did not see the meteor shower, but began an analysis of his own when reports starting being received by the British Astronomical Association. The fi rst report came from H. Welsh (Port Elizabeth, South Africa), followed by reports from J. H. Botham (Johannesburgh, South Africa) and Venter. Ridley said maximum activity occurred during the period of 19:00–20:00 UT, with hourly rates reported as 20–100. He said Venter’s reported radiant was the most reliable, having been determined from the tracks of 40 plotted meteors, and was given as a = 15°, d = −45°, with a possible error of ±5° in a and ±3° in d . Ridley determined a parabolic orbit and noticed a similarity to the orbit of the lost periodic comet discovered by J. J. Blanpain (Marseille, France) on 1819 November 28. He then calculated an elliptical orbit using the orbital period of comet Blanpain (see below).138 Another observation was published in 1958 March. A. A. Weiss analyzed the radio-echo observations made with equipment at the University of Adelaide (South Australia, Australia) in 1956 December. He determined the maximum rate as 30 per hour and gave the radiant position as a = 15° ± 2°, d = −55° ± 3°. Weiss considered the hourly rate a puzzle. For major showers, such as the Delta Aquariids and Geminids, the radio-echo rate was always greater than the visual rate, while the radio-echo Phoenicids were only one-third the strength shown by visual observations. One possible theory put forth was that “Earth was still on the fringe of the stream” when radio observations were made. Another suggested explanation was the possibility that slow meteors possessed a lower ionizing effi ciency that faster meteors—a condition never satisfactorily tested prior to the appearance of the Phoenicids. Weiss calculated a parabolic orbit and noted a “general similarity of the…elements with those of Comet 1819 IV Blanpain.” He then calculated an elliptical orbit for the meteor shower, but assuming the orbital period was the same as that of comet Blanpain, which was 5.1 years.139 Ridley (1962) made a complete investigation of the visual observations. He said the activity was fi rst detected by R. Lynch (Auckland, New Zealand) at 10:10 UT, and that it continued to become visible “as sunset progressed westwards,” until last detected by Venter (Pretoria, South Africa) at 22:45 UT. Ridley’s analysis could not clearly pinpoint the time of maximum, but he estimated “it must have lain somewhere between 17 h and 21 h UT.” For orbital calculations, he adopted 19 h UT ( l = 253° 33’) as the time of maximum. One of the most impressive features of the shower was the apparent presence of exploding fi reballs, as observers were frequently comparing the meteors “to the Moon, Venus, Jupiter, Sirius, etc.” The meteors were also frequently described as reddish and yellow. Ridley noted a large discrepancy in the estimates of the radiant, ranging from 10° to 70° in a and +10–−55° in d . But he noted that the most experienced observers, namely Venter 336 13 December Meteor Showers and Botham, determined radiants that were quite similar. Venter’s radiant was a = 15°, d = −45°, while Botham’s was a = 10°, d = −45°. Ridley considered Venter’s radiant more accurate because more plotted meteors were used. He also noted Weiss’ radiant determined using radio-echo methods was a = 15°, d = −55°.140 A search through the published papers of Southern Hemisphere meteor shower radiants reveals no prior observation of the Phoenicids. For the 30 years following the shower’s sudden appearance in 1956, no return of the prominent activity has been reported; however, visual observations were made on numerous occasions in the 1970s and 1980s. Observers in Western Australia (Australia) successfully monitored this radiant in the 1970s and 1980s. M. Buhagiar observed an apparent outburst on 1972 December 4/5, giving the ZHR as 20.141 The Western Australia Meteor Section (WAMS) made observations spanning 1977–1986. Activity was seen from 1977 December 2 to 5, with a maximum ZHR near 5 coming on December 5 from a radiant at a = 15°, d = −57°. In 1979, activity was observed on December 5 and 6, with a maximum ZHR near six coming on December 5 from a = 15°, d = −51°. Activity was next observed from 1980 November 29 to December 9. The maximum ZHR was near 3 and came on December 4 from a = 17°, d = −52°.14 In 1983, 17 amateur astronomers compiled 62 man-hours of observations and detected Phoenicids from December 1 to 10. The ZHR was above 1 during December 2–7, with a maximum near 6 coming on the night of December 4/5. A total of 97 meteors revealed an average magnitude of 3.27, while only 2 % left trains. 142 Another extensive observation program was conducted in 1985, as 25 observers compiled 122 man-hours over nine nights. The maximum ZHR reached eight, while the average magnitude was 2.38 and 4.8 % of the meteors left trains.143 Finally, in 1986, the 16 members of the WAMS observed for 40 man-hours and detected ZHRs of about 1 on December 4/5, 5 on December 5/6, and 1 on December 6/7. The average magnitude was 2.88, while 5.3 % of the meteors left trains.144 J. Rendtel (1996) presented a paper at the Proceedings of the International Meteor Conference in Brandenburg, Germany in 1995. He points out that Ridley (1962) listed 27 reports and adds, “The spread in the radiant positions is enormous.” Rendtel continues, “Even if we consider only those reports which base on more than ten shower meteors, the given radiants are situated between 10° and 70° in right ascension, and between +5° and −55° in declination.” He also commented that “the available data do not show a distinct maximum” and he pointed out that there is a gap in the observations that spans 14:00–18:00 UT. Finally, Rendtel concludes that all that can be stated is that there was “considerable meteor activity for the entire period between 10 and 20 UT.”145 The orbit labeled “1957” is from Ridley (1957) using Venter’s radiant and an assumed orbital period of 5.1 years, which is that accepted for the lost periodic comet D/1819 W1 (Blanpain). Weiss (1958) calculated two hypothetical orbits. The orbit labeled “1958p” is the parabolic one, while the orbit labeled “1958e” is the elliptical orbit using the assumed orbit period of 5.1 years for comet Blanpain. Ridley (1962) published a second paper that calculated two more hypothetical orbits. The orbit labeled “1962p” is the parabolic one, while the orbit labeled Alpha Puppids 337

“1962e” is the elliptical orbit using the assumed orbit period of 5.1 years for comet Blanpain. The orbit labeled “D/1819 W1” is the orbit of comet Blanpain. The orbit labeled “2003 WY25” is the orbit of the Apollo asteroid that might prove to be comet Blanpain.

w W (2000) i q e a 1957 356.5 74.3 12.0 0.985 0.668 2.96 1958p 0.1 74.1 19.3 0.985 1.0 ∞ 1958e 0.3 74.1 15.9 0.985 0.667 2.96 1962p 358.9 74.3 16.5 0.985 1.0 ∞ 1962e 358.7 74.3 13.4 0.987 0.667 2.96 D/1819 W1 350.26 79.81 9.11 0.8923 0.6988 2.96 2003 WY25 9.81 68.95 5.90 0.9613 0.6846 3.05

Alpha Puppids

The discovery of this stream should be attributed to R. A. McIntosh (Auckland, New Zealand), who listed this stream in his 1935 paper, “An Index to Southern Meteor Showers.” Based on two visual radiants detected in the period 1927–1934, the position was determined as a = 117.5°, d = −40.5°, while the duration was given as December 3–4.146 C. Hoffmeister (1948) spent most of 1937 in South-West Africa (now Namibia), where he was part of an expedition to isolate meteor radiants in southern skies. Four possible Alpha Puppid radiants seem to have been detected: the fi rst on December 6 (l = 253.5°) from a = 125°, d = −36°, another on the 8th (l = 255.6°) from a = 124°, d = −38°, a third on the 9th ( l = 257.0°) from a = 118°, d = −45° and the fi nal radiant on the 10th (l = 257.6°) from a = 115°, d = −40°.147 These observations seem to have offered the fi rst hint that this stream produces a fairly diffuse radiant. During the operation of radar equipment at Christchurch (New Zealand) in 1956, C. D. Ellyett and K. W. Roth detected activity from this radiant during ten nights between November 17 and December 8. The resolution capability of the equipment was not especially high so that the right ascension appeared to irregularly vary from 112° to 126°, while the declination fl uctuated between −41° and −49°. The authors gave average radiant estimates of a = 122°, d = −45° for November 17–21, and a = 120°, d = −43° for November 27–December 8.148 The Western Australia Meteor Section (WAMS) obtained several excellent observations of this stream, which they refer to as the “N Puppids.” In 1977, stream members were detected from December 2 to 6, with a maximum ZHR of about 7 coming on December 2 from a = 120°, d = −43°. 14 In 1978, activity was detected from November 25 to December 6 and a maximum of ten meteors per hour came on December 4/5 from an average radiant of a = 118°, d = −43°. The meteors were described as fast, with an average magnitude of 3.29 and a total of 2.2 % left trains. The meteor colors tended to be blue-white or white.149 338 13 December Meteor Showers

The WAMS continued to observe this radiant in 1979 and 1980. In the former year, the duration of activity extended from November 24 to December 9. A maximum ZHR of about 9 came on December 1 from a = 116°, d = −42°. In the latter year, observations revealed activity from November 29 to December 15. A maximum ZHR of about 7 came on December 5 from a radiant of a = 128°, d = −45°.14 The following two orbits were calculated assuming December 5 as the date of maximum and averaging four radiants from December 3 to 6. The ﬁ rst is a parabolic orbit, while the second is an elliptical orbit based on an assumed semimajor axis of 2.5 AU.

w W (2000) i q e a 21.1 71.9 75.7 0.952 1.000 ∞ 25.3 71.9 69.0 0.949 0.621 2.5

Sigma Serpentids

w W (2000) i q e a 2002–2006 41.1 275.5 62.4 0.157 0.9216 2.0 2002–2008 41.20 275.0 62.4 0.1596 0.916 1.90 Ursids 339

Psi Ursae Majorids

The discovery of this meteor shower was announced in 2009 by the Japanese video meteor network SonotaCo. During a survey spanning 2007–2008, they detected 33 meteors from a radiant at a = 167.8°, d = +44.5°. The radiant was active from November 22 to December 16 (l = 240.0–265.1°), with the peak occurring on December 4 ( l = 252.9°). The geocentric velocity was given as 60.7 km/s, while the radiant drift was determined as +0.20° in a and −0.01° in d per day.29 The International Meteor Organization’s Video Meteor Network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras from 1993 to 2012. Stream number 230 is called the “Psi Ursae Majorids” and is based on 1297 meteors. The duration is given as November 30–December 16 (l = 248– 264°), while maximum occurs on December 4 (l = 252°) from a radiant at a = 174.0°, d = +41.9°. The radiant drift was determined as +1.1° in a and −0.4° in d per day.153 The orbit below was again calculated using the radiant and velocity provided by the IMO’s Radio Meteor Network.

w W (2000) i q e a 204.3 250.8 122.0 0.950 0.686 0.95

Ursids

Duration: December 17 to December 26 (l = 265–275°) Maximum: December 22 (l = 270.7°) Radiant: a = 217°, d = +75° ZHR: 10

Radiant Drift: a = +1.77°, d = −0.05° V G : 36 km/s

The Report of the Forty-Fourth Meeting of the British Association for the Advancement of Science (1875) contained a list of possible meteor shower radiants calculated from the orbits of comets. Theoretical radiants were determined for 82 different comet apparitions, including two apparitions of periodic comet 8P/Tuttle. For the discovery apparition of 1790, maximum was predicted for December 20 from a radiant at a = 220°, d = +76°. The comet was lost for several returns but was accidentally rediscovered in 1858. For this apparition, maximum was predicted for December 20 from a radiant at a = 221°, d = +77°. 154 There seems to be no trace of this meteor shower in any radiant catalog published in the nineteenth century; however, W. F. Denning (Bristol, England) wrote a letter to The Observatory in 1916, which mentioned the radiant calculations noted above (attributing them to A. S. Herschel) and stated, “I have seen a meteoric 340 13 December Meteor Showers shower from 220°, +76° Dec. 18–25 in various years, but the display has shown no special abundance.” He continued, “I have, however, obtained comparatively few observations at the particular date mentioned, except in 1876 and 1885.” Although the radiant he gives for the 1885 radiant is about 12° southwest of the predicted radiant for the Ursids, he wrote, “The other shower near [Beta] Ursae Minoris is, however, in excellent agreement, and suggestive that further observations should be made on about Dec. 20 to recover it.”155 Despite Denning’s request for further observations, few appear to have been made during the years that followed. Denning (1923) did mention the shower in his catalog of radiant points, but gave no indication of recent observations. He simply noted that in “various” years meteors had been seen from December 18 to 22 from a radiant at a = 218°, d = +76°. He said the radiant was determined from seven meteors and he considered it accurate.156 This meteor shower was forgotten about by the time the next observation was made. On the night of 1945 December 22, M. Dzubák (Skalnate Pleso Observatory, Slovakia) observed a meteor shower from the region of Ursa Minor from 16:30 to 20:45 UT. He said maximum came between 18:15 and 18:25 UT, when meteors were falling at a rate of 169 per hour. From 16 plotted paths, he determined the radiant as a = 233°, d = +82.6°. According to A. Becvár (Skalnate Pleso Observatory), many meteors were photographed. He added, “Connection with the comet 1792 II [this should have been 1790 II, which is 8P/Tuttle] is highly presumable.” 157 A rein- vestigation of the data by Z. Ceplecha revealed a ZHR of 108, after compensating for the fact that the original numbers were made by four observers. He also said the measurements of meteors on four photographs revealed a radiant at a = 217.1°, d = +75.9°. With respect to the difference between the radiant determined from the visual plots and that determined from photographs, Ceplecha noted that meteors No. 2 and No. 3 on Dzubák’s chart were also photographed, and it became evident that the visual plots were off. He referred to the meteor shower as the “Umids”. Ceplecha commented, “Becvár’s meteor stream 1945 was evidently a condensation in the Umid stream….” He added, “It is interesting that the condensation observed in 1945 in Umid meteor stream is almost on the opposite side of the orbit than comet.”158 Coordinated studies of this meteor shower were made in 1946. The initial announcement sent out by Skalnaté Pleso Observatory indicated that 55 meteors were seen on the night of December 22. The peak occurred on December 22.92 UT, at which time the radiant was at a = 203°, d = +75°. The frequency of meteors seen by one observer was 7/h, but corrected for a zenith location increased this to 11/h. 159 Z. Bochnícek (Skalnaté Pleso Observatory) and V. Vanysek (Ondrejov Observatory, Czech Republic) provided additional details. Plots of 17 meteors by Bochnícek indicated a radiant at a = 213°, d = +75°, 160 while plots of 9 meteors by Vanysek found it to be at a = 217.8°, d = +76.7°. 161 J. P. M. Prentice (England) watched for signs of this meteor shower in 1947. During 1 h 43 min on December 22, only one meteor from the Ursid radiant was seen, but in 25 min on December 23, eight meteors were detected—making the hourly rate about 20. Four of the eight meteors detected on the latter date were Ursids 341 plotted and revealed a radiant of a = 207°, d = +74°. The radiant diameter was less than 1°.162 In addition to Prentice’s observations, the Ursids were also detected by the radio-echo equipment at the Jodrell Bank Experimental Station in 1947. The aerials fi rst got a bearing on the shower on December 22.13. Rates were determined from December 22.38 until December 23.46; these rates averaged 15 per hour (equiva- lent visual rate of about 10). Thereafter, activity dropped sharply. The pointing of the aerial to different directions allowed the radiant to be determined as a = 195 ± 8°, d = +78 ± 5°. 163 C. Hoffmeister published his book Meteorströme in 1948 and provided additional observations for the Ursids. On 1914 December 20 (l = 268°), he plotted meteors from a radiant at a = 214°, d = +66°. On 1931 December 18.3 (l = 265.4°), he plotted meteors from a radiant at a = 196°, d = +73°. On 1933 December 16.6 ( l = 264.2°), he plotted meteors from a radiant at a = 215°, d = +69°. 164 Astronomers at Jodrell Bank provided the only observations of this meteor shower from 1948 to 1953, discovering a fairly consistent, but much weaker shower than had been seen in 1945. They said the peak rate in 1948 was 15 per hour and came on December 21.3 (l = 269.4°) from a radiant at a = 210° ± 10°, d = +82° ± 8°. In 1949, the peak rate was 13 per hour and came on December 22.3 (l = 270.2°) from a radiant at a = 207.1° ± 8°, d = +77.6° ± 3°. The peak rate in 1950 was 20 per hour and came on December 22 (l = 269.8°) from a radiant at a = 199° ± 8°, d = +77° ± 3°. 165 K. Bullough (1954) published observations for the period of 1951 through 1953. In 1951, the peak rate was 13 per hour, which came on December 23 ( l = 270.5°) from a radiant at a = 200°, d = +77°. Positions were not determined in 1952 and 1953, but the peak rate was 8 per hour on December 21 (l = 269.5°) in the fi rst year and 11 per hour on December 23 (l = 271.0°) in the second year. Bullough added that the observations of this weak display “are limited to the hourly rates observed during transit, this fi gure being an upper limit to the activity” of this stream.166 The Ursids were occasionally observed in the 1970s, but the shower seemed weaker than what was indicated in the 1940s and early 1950s. Several observers in the United States provided observations from 1970 December 20 to 28. The average ZHR for the entire period was 2.5, with the highest rates being 3.1–3.2 on December 22 and 3.5 on December 26.167 The Ursids were seen again in the United States in 1971. Observations spanned December 20–25, but the hourly rate only reached 2.9. 168 In Japan, observers detected ZHRs of 5.7 in 1970 and 2.4 in 1971. 168 Observers in the United States determined the ZHR as about 1.2 on 1974 December 22/23. 169 An outburst seems to have been noted by observers in Sogne, Norway in 1979. They noted a strong display during 2 h of observations on December 22 and estimated ZHRs of 25–27.170 N. W. McLeod, III (Florida) commented that the Ursids “must be a compact stream like the Quadrantids. You have to be within 12 h of maximum to see much.”171 There was a report of enhanced activity on the night of 1981 December 22. Although hourly rates are not available, there were reports of numerous fi reballs 342 13 December Meteor Showers seen over Japan. The all-sky camera at Kiso Observatory (Mt. Ontake, Japan) photographed fi ve of these fi reballs in 6 h.172 Reports of attempted observations of the Ursids were reported to Meteor News for the 1982 return. The only success was by M. T. Adams (Palm Bay, Florida, USA), who saw a ZHR of 2 on December 22.173 Another outburst occurred in 1986. L. Gobin (Belgium) reported unexpected “very high rates” while operating his radio equipment at 66.17 MHz. 175 Gobin’s equipment had detected average hourly echo rates of 60–68 on December 19, 20, 21, and 23, but found rates of 171 on the 22nd.175 This enhanced activity was also noted visually and seems to have peaked in the nighttime hours over Europe. G. H. Spalding (director of the British Astronomical Association Meteor Section) said his observations on December 22 revealed a ZHR of 87 ± 29.176 T. E. Hillestad (Norwegian Meteor Section) reported the observations of K. Gaarder and L. T. Heen. The former observer detected 94 Ursids in 4 h, including 37 in the hour following December 22.83 (ZHR = 64 ± 11), and reported an average magnitude of 1.90. The latter observer saw 75 Ursids in 2 h, including 54 in the hour following December 22.88 (ZHR = 122 ± 17), and reported an average magnitude of 2.61. Of the 175 Ursids seen, 17.1 % exhibited a persistent train. Of the 66 Ursids of magnitude 2 and brighter, 51.5 % were white, 33.3 % were yellow, 7.6 % were red, 2.3 % were green, and 5.3 % were blue.177 In 1993, J. Brausch (North Dakota, USA) and R. Lunsford (California, USA) independently reported unusual activity from the Ursids on the morning of December 22. Brausch reported hourly rates of 24, while Lunsford reported hourly rates as high as 26. P. G. Brown (1994) said both observations occurred at almost the same time and “under good sky conditions.” He said resulting ZHRs would have been “between 50 and 100!”178 There were con fl icting reports of enhanced activity in 1994. K. Ohtsuka, H. Shioi, and E. Hidaka (1995) reported that enhanced activity was reported by Shioi on December 22.757 (l = 270.75°). The indicated hourly rate was 30, while the ZHR was >100. A tentative population index of r = 2.2 was estimated and the radiant was determined as a = 217°, d = +76°. Because of prevailing bad weather across Japan, few observers were able to see the display. In addition, only one camera of the Tokyo Meteor Network was able to capture an Ursid meteor, which appeared on December 22.756.179 Interestingly, seven members of the British Astronomical Association watched the Ursids on the same night covering the period December 22.751–22.927. They reported ZHRs of 8.4–16.4, which would be close to normal.180 A widely publicized prediction of a possible Ursid outburst was made on 2000 December 18 by P. Jenniskens. He expected the peak to occur on December 22.31 as a result of material ejected from the comet in 1405. He added that additional material from the 1378 to 1392 returns “could expand this activity over an interval of 4–5 h”.181 In a very short note on International Astronomical Union Circular number 7548, Jenniskens announced that the prediction was successful with the peak ZHR being >50.182 Ursids 343

A formal paper on the outburst was published in the Journal of the International Meteor Organization in 2001 April. Written by Jenniskens and E. Lyytinen, it presented the data acquired by image intensi ﬁ ed video cameras, 35 mm cameras, and radio-echo observations in California (USA), Finland, Japan, and Belgium. Visual observations were apparently made in California, the Netherlands, and Japan. The peak activity reached 90 on December 22.34.183 Ursid outbursts were again predicted by Jenniskens for 2006 and 2007. ZHRs in the ﬁ rst year amounted to 15 ± 5. Although this was less than half the predicted value, the Ursids were described as “unexpectedly bright.” 184 The peak ZHR in 2007 reached 34 ± 5 at a solar longitude of 270.53°.185 The orbit labeled “1954” is from Jodrell Bank reprints, volume 4 (1960).186 The orbit labeled “1961–1965” is from Sekanina (1970). Sekanina admitted that the maximum of the shower was missed, but said, “several meteors with orbits some-

w W (2000) i q e a 1954 206 272 51 0.92 0.88 7.7 1961–1965 194.7 281.6 63.0 0.968 0.761 4.05 Photo 208.4 268.0 52.6 0.929 0.848 6.11 8P 207.51 270.34 54.98 1.0271 0.8199 5.70

what resembling that of P/Tuttle were detected....” The orbit labeled “Photo” is the average of two photographic meteors found among survey results.187 The orbit labeled “8P” is that of periodic comet Tuttle.

w W (2000) i q e a 950 205.4 276.8 53.4 0.99 0.83 5.86

Using an orbit similar to the photographic one above, K. Fox (1986) computed the orbit of the Ursid stream for periods 1,000 years in the past and future. Although Earth seems to have been in contact with the Ursid stream 1,000 years ago, no contact will apparently be possible 1,000 years in the future. In 950, the shower’s maximum would have occurred 6 days later than at present from a radiant of a = 214.5°, d = +73.2°.115 344 13 December Meteor Showers

December Chi Virginids and December Sigma Virginids

The discovery of the “December Chi Virginids” was announced in 2009 by the Japanese video meteor network SonotaCo. During a survey spanning 2007–2008, they detected 31 meteors from a radiant at a = 186.8°, d = −7.9°. The radiant was active from November 28 to December 18 (l = 246.1–266.4°), with the peak occurring on December 8 (l = 256.7°). The geocentric velocity was given as 67.8 km/s, while the radiant drift was determined as +0.20° in a and −0.14° in d per day.29 J. Greaves (2012) discovered the “December Sigma Virginids” while examining the meteor database of the Japanese video meteor network SonotaCo. He found 22 meteor orbits from 2007 to 2009, indicating the duration as December 15–25 ( l = 262.3–272.6°). Maximum came during December 20–22 (l = 267–270°) from a radiant at a = 205.0°, d = +5.5°. The geocentric velocity was determined as 66 km/s. 188 Greaves said the orbit of this meteor stream was close to that of comet C/1846 J1 (Brorsen). The similarity of these two showers is striking, with the December Chi Virginids representing the southern branch and the December Sigma Virginids representing the northern branch of a fairly well-de ﬁ ned system. The International Meteor Organization’s Video Meteor Network has created a web site titled “Million Meteors in the IMO Video Meteor Database,” which includes the results of over a million meteor paths acquired by video cameras during the period 1993–2011. Both of these radiants are present. The December Sigma Virginids were found by a software took called StrmFind and were listed as shower 243. The details were based on 1517 meteors. The duration is given as December 6–January 8 (l = 254–287°), during which time the radiant moves from a = 193.7°, d = +6.5° to a = 222.5°, d = −0.5°. Maximum occurs on December 31 (l = 279°) from a radiant at a = 213.7°, d = +2.5°. The radiant drift was determined as +0.8° in a and −0.2° in d per day.189 The December Chi Virginids were not found by the StrmFind software tool; however, activity was located from this radiant on 17 consecutive days spanning December 8–24 (l = 256–272°). During this period the radiant moved from a = 186.3°, d = −9.0° to a = 197.7°, d = −15.0°. Maximum occurred on December 13–14 from a radiant at a = 189.7°, d = −9.3°. The radiant drift was determined as +0.7° in a and −0.4° in d per day.10 T. Brorsen (Holstein, Germany) discovered comet C/1864 J1 on 1846 May 1. The comet passed 45 million miles from Earth on May 6 and passed closest to the Sun on June 5 (0.63 AU). It became a naked eye object around mid-May and was followed until June 15, when it became lost in twilight. The comet was not seen thereafter. Several astronomers calculated elliptical orbits indicating a period between 401 and 538 years.190 A search for older observations of these two meteor showers found few potential candidates. J. F. J. Schmidt (1869) noted a radiant at a = 182°, d = −2° that was visible during December.191 Schmidt (1874) listed the radiant again, but provided the duration as December 10–21.192 W. F. Denning (1899) reported that he made an observation of a radiant at a = 193°, d = −5° around 1877 December 13.193 F. W. December Chi Virginids and December Sigma Virginids 345

w W (2000) i q e a Chi 281.0 75.2 164.5 0.592 0.974 22.87 Sigma 102.66 267.41 149.64 0.605 0.974 23.29 C/1846 J1 99.73 263.99 150.68 0.634 0.990 66.11

Smith (Glenolden, Pennsylvania, USA) plotted four meteors from a radiant at a = 189.0°, d = −1.0° on 1934 December 15.194 The orbit labeled “Chi” was calculated using the radiant and velocity provided by SonotaCo (2009). Greaves (2012) determined the orbit labeled “Sigma” using meteors found in the SonotoCo database. The orbit labeled “C/1846 J1” is that of comet Brorsen.

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137. S. C. Venter, Monthly Notes of the Astronomical Society of Southern Africa , 16 (1957 Feb. 28), pp. 6–7. 138. H. B. Ridley, British Astronomical Association Circular , No. 382 (1957 Feb. 7). 139. A. A. Weiss, Australian Journal of Physics , 11 (1958 Mar.), pp. 114–17. 140. H. B. Ridley, Journal of the British Astronomical Association , 72 (1962), pp. 267–8. 141. M. Buhagiar, Personal Communication (1995 June 16). 142. J. Wood, WGN, Journal of the International Meteor Organization , 12 (1984 Jun.), pp. 75–6. 143. J. Wood, Meteoros , 16 (1986 Aug.), p. 69. 144. J. Wood, Meteor News , No. 79 (1987 Oct.), p. 6. 145. J. Rendtel, Proceedings of the International Meteor Conference, Brandenburg, Germany, 1995 (1996), pp. 72–5. 146. R. A. McIntosh, Monthly Notices of Royal Astronomical Society , 95 (1935 Jun.), p. 712. 147. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 244–5. 148. C. D. Ellyett and K. W. Roth, Australian Journal of Physics , 17 (1964), p. 505. 149. J. Wood, Meteor News , No. 45 (1979 Apr.), p. 11. 150. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Central Bureau Electronic Telegram , No. 1142 (2007 Nov. 17). 151. P. G. Brown, R. J. Weryk, D. K. Wong, and J. Jones, Icarus , 195 (2008), pp. 327, 331. 152. P. G. Brown, D. K. Wong, R. J. Weryk, and P. A. Wiegert, Icarus , 207 (2010), pp. 70, 72. 153. http://www.imonet.org/showers/shw230.html 154. Report of the Annual Meeting of the British Association for the Advancement of Science , 44 (1875), pp. 270, 358–9. 155. W. F. Denning, The Observatory , 39 (1916 Nov.), pp. 466–7. 156. W. F. Denning, Monthly Notices of the Royal Astronomical Society , 84 (1923 Nov.), p. 52. 157. A. Becvár, International Astronomical Union Circular , No. 1026 (1946 Jan. 24). 158. Z. Ceplecha, Bulletin of the Astronomical Institutes of Czechoslovakia , 4 (1951), pp. 156–160. 159. A. Becvár, International Astronomical Union Circular , No. 1078 (1947 Feb. 4). 160. Z. Bochnicek and V. Vanysek, Bulletin of the Astronomical Institutes of Czechoslovakia , 1 (1948), pp. 26–7. 161. V. Vanysek, Bulletin of the Astronomical Institutes of Czechoslovakia , 1 (1947), pp. 10–11. 162. J. P. M. Prentice, Journal of the British Astronomical Association , 58 (1948 May), p. 140. 163. Clegg, J. A., Hughes, V. A. and Lovell, A. C. B., Journal of the British Astronomical Association , 58 (1948 May), pp. 134–9. 164. C. Hoffmeister, Meteorstöme . Leipzig: Verlag Werden und Werken Weimar (1948), pp. 205, 212, 214, 216–17, 247. 165. A. C. B. Lovell, Meteor Astronomy . Oxford: Clarendon Press (1954), pp. 320, 322. 166. K. Bullough, Jodrell Bank Annals , 1 (1954 Jun.), pp. 81, 96. 167. Meteor News , No. 5 (1971 Mar.), pp. 7–8. 168. Meteor News , No. 10 (1972 Mar.), p. 5. 169. Meteor News , No. 25 (1975 Mar.), p. 6. 170. Meteor News , No. 51 (1980 Oct.), p. 5. 171. N. W. McLeod, III, Meteor News , No. 35 (1977 Mar.), p. 8. 172. K. Ohtsuka, H. Shioi, and E. Hidaka, WGN, Journal of the International Meteor Organization , 23 (1995 Apr.), p. 69. 173. M. T. Adams, Meteor News, No. 61 (1983 Apr.), p. 3. 174. C. Steyaert, Personal Communication (1987 Jan. 19). 175. J. van Wassenhove, WGN, Journal of the International Meteor Organization , 15 (1987 Feb.), pp. 12–13. 176. P. Roggemans, WGN, Journal of the International Meteor Organization , 15 (1987 Apr.), p. 50. 177. T. E. Hillestad, WGN, Journal of the International Meteor Organization , 15 (1987 Apr.), pp. 59–60. 178. P. G. Brown, WGN, Journal of the International Meteor Organization, 22 (1994 Apr.), p. 51. 350 13 December Meteor Showers

179. K. Ohtsuka, H. Shioi, and E. Hidaka, WGN, Journal of the International Meteor Organization , 23 (1995 Apr.), pp. 69–72. 180. N. Bone, WGN, Journal of the International Meteor Organization , 23 (1995 Aug.), p. 158. 181. P. Jenniskens, International Astronomical Union Circular , No. 7544 (2000 Dec. 18). 182. P. Jenniskens, International Astronomical Union Circular , No. 7548 (2000 Dec. 23). 183. P. Jenniskens and E. Lyytinen, WGN, Journal of the International Meteor Organization , 29 (2001 Apr.), pp. 41–5. 184. P. Jenniskens, Central Bureau Electronic Telegram , No. 788 (2006 Dec. 28). 185. P. Jenniskens, Central Bureau Electronic Telegram , No. 1188 (2007 Dec. 31). 186. Jodrell Bank Reprints , 4 (1960), p. 222. 187. Z. Sekanina, Icarus , 13 (1970), pp. 476, 488. 188. J. Greaves, WGN, Journal of the International Meteor Organization , 40 (2012 Feb.), pp. 17–19. 189. http://www.imonet.org/showers/shw243.html 190. G. W. Kronk, Cometography , volume 2. United Kingdom: Cambridge University Press (2003), pp. 165–6. 191. J. F. J. Schmidt, Astronomische Nachrichten , 74 (1869), pp. 57–8. 192. J. F. J. Schmidt, Report of the Annual Meeting of the British Association for the Advancement of Science , 44 (1875), p. 323. 193. W. F. Denning, Memoirs of the Royal Astronomical Society , 53 (1899), p. 260. 194. F. W. Smith, Popular Astronomy , 50 (1942 Dec.), p. 558. Glossary

De ﬁ nitions

Aberration An effect that is caused by the rotation of Earth on its axis. This becomes a very important factor when calculating the true radiants and orbits of meteors and meteor showers. Apparent Radiant The point from which meteors are observed to radiate before being corrected for zenithal attraction and aberration. Bolide A bright meteor which is observed to fragment or explode. If close enough the observer can expect to hear sounds of the explosion. Daylight Meteor Shower A meteor shower which is above the horizon during the same time as the sun. It is detectable only by radio and radar methods. Double Radiant A meteor stream that is affected by planetary perturbations can become split into two or more branches. Several major meteor streams visible near the ecliptic and therefore more susceptible to perturbations possess double radiants, usually referred to as northern and southern components. Fireball A meteor which is brighter than any planet or star, i.e. brighter than magnitude −4. Hourly Rate The number of meteors seen in an hour. Abbreviated “HR”. Meteor The streak of light produced when a meteoroid encounters Earth’s atmosphere and burns up due to the friction of air resistance. Meteors are popularly known as “shooting stars” and “falling stars.”

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 351 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3, © Springer Science+Business Media New York 2014 352 Glossary

Meteorite A meteor that is large enough to survive its passage through the atmosphere and reach the ground. Meteor Shower A shower of meteors occurs when Earth’s orbit intersects the orbit of a meteor stream. The meteors usually fall at a rate less than 1 per minute as a result of their being separated by hundreds of kilometers. Meteor Storm This is a rare event that occurs when Earth encounters closely grouped meteors in the orbit of a meteor stream. During the time of this encounter, meteors can fall at rates greater than 1,000 per minute. Meteor Stream This represents the orbit of meteoroids as they travel about the sun. Meteors are the by-product of comets, so it is possible for the parent comet to be traveling in the same orbit if it still exists. Meteor Swarm A cluster of meteoroids traveling within a meteor stream that is separated by much smaller distances than normal. If encountered by a planet, a meteor storm will occur. Minor Showers Meteor showers that produce less than 10 meteors per hour at the time of maximum activity. Path The trajectory of a meteor projected against the sky from the observing site. Persistent Train Train luminosity that lasts more than a second. Radiant The point from which a meteor appears to emanate. For meteor showers the radiant is actually a by-product of a perspective effect, similar to what is seen when looking down railroad tracks the meteors appear to be moving in all directions, but they are actually parallel to one another. Radiant Drift The movement of a meteor shower’s radiant against the star background. This characteristic is common to all meteor showers and is caused by Earth’s passage through a meteor stream. Solar Longitude The longitude of the sun as given in geocentric coordinates. The evaluation of meteor data strongly relies on this ﬁ gure rather than a conventional date. Sporadic Meteor A meteor which does not belong to an active shower radiant. The number visible per hour on any given night with the naked eye averages 6 after sunset and 18 just before dawn. Stationary Radiant A radiant which remains in one position for days, weeks, or months. Such a radiant is a mathematical impossibility. Telescopic Meteors A meteor below the limit of naked-eye visibility that is only visible in telescopes or binoculars. Terminal Burst The ﬂ are at the end of a meteor’s path. Glossary 353

Toroidal Stream A stream with an orbit of low eccentricity and high inclination which surrounds the Earth’s orbit. Train A trail of ionized dust and gas that remains along the path of a meteor. Wake Train luminosity lasting only a fraction of a second. Zenithal Attraction The displacement of a radiant’s location due to the gravitational attraction of Earth. The displacement becomes more pronounced as a radiant approaches the horizon, so that corrections must be applied. Zenithal Hourly Rate (ZHR) This is the rate a meteor shower would possess if seen by an observer with a clear, dark sky and with the radiant in the zenith. Index

A B Abe, S. , 108 Babadzhanov, P.B. , 37, 38, 157, 158, 218, 248, Adams, J.C. , 278, 279 318, 319 Adams, M.T. , 112, 122, 243, 284, 340 Backhouse, T.W. , 32, 91, 242, 288, 308, 314 Adamson, C.P. , 198 Baggaley, W.J. , 45, 46, 79, 221, 222 Afana’seva, L.M. , 57, 66 Baker, K. , 284 Alcock, G.E.D. , 33, 99 Banks, J. , 189 Alden, H.L. , 187 Bateson, F.M. , 143 Almond, M. , 32, 38, 97, 98, 101, 106, 107, Batt, R.A. , 184 134–136, 144, 294, 322 Becker, G. , 112 Anderson, J.F. , 258 Becvár, A. , 338 Andreic, Ž. , 156 Beebe, H.A. , 229 Andrews, S.L. , 190 Beech, M. , 295, 319 Aneca, P. , 196 Bekink, G. , 333 Angelos, C. , 282 Bellot Rubio, L.R. , 175, 179, 186, 277, 285 Arago, F.J.D. , 67, 191 Beltran, A.G. , 79 Araki, G. , 99 Belyaev, N.A. , 280 Arakida, H. , 221 Belyakov, B.M. , 57 Aristotle , 2, 3 Bennett, D.A. , 181 Arlt, R. , 74, 113, 117, 118, 149, 174, 175, 179, Benzenberg, J.F. , 7, 8, 67, 245 182, 196, 215, 231, 241, 277, 295 Berberich, A. , 75 Artoos, D. , 221 Bernhard, H.J. , 181 Asher, D.J. , 281, 294, 295 Besley, W.E. , 32, 152 Aspinall, A. , 97, 100, 106, 107, 125, 134 Betlam, H. , 282, 303 Astapovich, I.S. , 280, 290, 319, 326 Biela, W. von , 255, 257, 258, 260–262 Astbury, T.H. , 314 Biot, J.B. , 69 Aymé, J.-J. , 269 Blagden, C.B. , 6, 7

G.W. Kronk, Meteor Showers: An Annotated Catalog, The Patrick Moore 355 Practical Astronomy Series, DOI 10.1007/978-1-4614-7897-3, © Springer Science+Business Media New York 2014 356 Index

Blakeley, E.R. , 329 Collander-Brown, S.J. , 37 Blanpain, J.J. , 286, 333, 334 Collinson, E.H. , 70, 71 Blencowe, G. , 79 Conger, D. , 59, 112 Bochnícek, Z. , 338 Cook, A.F. , 19, 66, 99, 100, 123, 157, 158, Bondar, N.I. , 160 217, 232, 261–263, 307, 317 Bonpland, A. , 269 Cook, A.G. , 70, 143, 184, 194, 207, 246, Booth, D. , 242, 243 290, 314 Borovicka, J. , 180, 285 Corder, H. , 19, 26, 70, 90, 91, 128, 152, 184, Borrelly, A.L.N. , 259 223, 233, 272, 289, 308, 314, 328, 329 Botham, J.H. , 333, 334 Coulvier-Gravier, R.A. , 193 Bouvard, A. , 191 Cranidge, T.F. , 289 Bouvier, K. , 238 Crommelin, A.C. de la C. , 236, 237 Bradley, F.T. , 67, 192, 282 Cruls, L. , 166 Brandes, H.W. , 7, 8, 191, 192, 245, 256 Cunnius, E. , 275 Brausch, J. , 340 Currie, M.J. , 58, 59, 224 Brook, C.L. , 314 Curry, P.A. , 273 Brorsen, Theodor Johann Christian Curtis, H.D. , 91 Ambdersá , 342 Brown, P.G. , 18, 22–24, 27, 36, 38–40, 45, 46, 55, 56, 65, 66, 73, 75, 77, 94, 95, 97, D 98, 101, 112, 124–126, 135–137, 155, Dalton, J. , 270 158, 159, 161–163, 165, 175, 176, 180, Darling, B.C. , 198 182, 197, 200–202, 211–213, 221, 222, d’Arrest, H.L. , 257, 259 241, 249, 251, 252, 263, 264, 276, 277, Davidson, M. , 236, 237 282, 285, 286, 295, 296, 308, 309, 316, Davidson, T.W. , 101, 107 322, 336, 340 Davies, J.K. , 321 Bryce, A. , 143 Davis, M.T. , 39, 168, 221 Buhagiar, M. , 22, 50, 62, 75, 79, 105, 148, de Cesaris, A.G. , 6 164, 167, 174, 178, 219, 308, 334 de Konkoly, N. , 151, 177, 183 Bullough, K. , 97, 98, 107, 134, 339 de Kövesligethy, R. , 287 Bunton, G.W. , 238 de Lignie, M.C. , 35, 38, 186, 303, 305 Burland, M.S. , 315 de Malbos, J. , 245 Burney, W. , 8, 189, 190 de Meyere, M. , 223 Burt, P. , 56 de Pontieu, B. , 196 Bus, E.P. , 240, 241 de Vico, F. , 255 Bush, C.P. , 192, 256 Denning, W.F. , 9, 16, 18, 25, 26, 33, 46, 47, 52, 65, 70–72, 80, 82, 90, 91, 109–111, 119, 124, 128, 133, 142, 151, 152, 158, 166, C 171, 172, 177, 181–185, 193, 194, 198, Campbell-Brown, M. , 241 213, 214, 216, 219, 223, 227, 230, 233, Carusi, A. , 281 236, 237, 242, 243, 246, 259, 272, 273, Ceplecha, Z. , 199, 200, 330, 338 289, 290, 313–315, 317, 328, 337, 342 Cevolani, G. , 248 Denza, F. , 183 Chasles, M. , 69 Denza, P.F. , 258 Chebotarev, R.P. , 248 Devault, A. , 122 Chladni, E.F.F. , 7, 8, 191 Deweerdt, J. , 196 Christie, W.H. , 184, 185 Dole, R.M. , 110, 111, 246, 260, 272, 284 Clap, T. , 5, 6 Downing, A.M.W. , 279 Clark, J.E. , 211 Doylerush, E. , 16 Clegg, J.A. , 92, 100, 106, 125 Drummond, J.D. , 11, 57, 79, 99, 164, 229, Clifton, S. , 99 230, 243, 330 Clube, S.V.M. , 294, 295 Dubietis, A. , 74, 93, 149, 154, 175, 182, 215, Coggia, J.E. , 259 231, 250, 295 Colla, A. , 31, 192, 193, 257, 311 Ducoty, R. , 284 Index 357

Dunlop, J. , 85 Graziani, J. , 190 Dvorak, S. , 121, 122 Greaves, J. , 304, 342, 343 Dzubák, M. , 338 Green, S. , 321 Greg, R.P. , 31, 39, 46, 69, 82, 90, 151, 289, 312 Gregory of Tours , 69 E Grigg, J. , 75 Edwards, B. , 78 Grigsby, B. , 120 Eginitis, D. , 152 Grishchenyuk, A. , 186 Elford, W.G. , 22, 49–51, 55, 56, 60, 62, 95, Grygar, J. , 160 105–108, 125–127, 164, 233, 234, 325 Gural, P.S. , 51, 156 Elkin, W.L. , 10 Guth, V. , 72, 73, 209, 284 Ellicott, A. , 269, 270 Gyssens, M. , 277 Ellison, W.F.A. , 237 Ellyett, C.D. , 61, 130, 135, 167, 335 Emerson, B. , 201 H Erman, A. , 8, 9 Haile, A.B. , 192, 256 Evans, G.C. , 17, 134, 135 Hajduk, A. , 93, 247, 248, 250, 315 Evdokimov, Y.V., 280 Hale, M. , 47, 262 Evershed, J. , 184 Halley, E. , 4–6 Hamane, T. , 112 Hamid, S.E. , 34, 35, 37, 78, 147, 294 F Hamilton, W. , 143, 189 Farey, J. , 8, 189, 190 Hardcastle, J.A. , 152 Faulkner, D. , 56 Hargrove, M. , 295 Fischer, B. , 122 Harris, A.W. , 115 Flaugergues, P. , 257 Harris, N.W. , 201 Forbes-Bentley, R. , 237 Hartung, J.B. , 115 Ford, C.B. , 198 Harvey, G.A. , 38 Forshey, C.G. , 82 Hasegawa, I. , 37, 181, 326, 327, 331 Forster, T.F. , 190 Haver, R. , 285, 312 Forsyth, E.L. , 238 Hawkins, G.S. , 10, 25, 32, 38, 95, 97, 101, Fox, K. , 53, 74, 75, 113, 120, 123, 241, 244, 107, 119, 125, 129, 134, 144, 243, 251, 320, 321, 323, 326, 327, 341 261, 263, 322 Frolov, V.V., 56, 160 Heen, L.T. , 340 Fujiwara, Y. , 108 Heis, E. , 31, 80, 82, 142, 171, 192, 193, 213, 257, 288, 289, 311 Henry, J.R. , 273 G Herrick, E.C. , 30, 67, 68, 72, 192, 193, 245, Gaarder, K. , 340 256, 257, 311, 312 Gajdos, S. , 252 Herschel, A.S. , 16, 23, 31, 69, 82, 90, 91, 128, Galle, J.G. , 70 142, 151, 166, 193, 246, 312–314, 337 Galligan, D.P. , 45, 46, 221, 222 Herschel, J.F.W. , 214, 255 Gannett, C. , 189 Hesiod , 3 Gartrell, G. , 22, 49–51, 55, 56, 60–62, Hey, J.S. , 11, 238 105–108, 125–127, 164, 233, 234, 325 Hidaka, E. , 340 Gates, B. , 19, 20, 47, 174 Hill, R. , 47 Gauss, C.F. , 279 Hill, R.K. , 229 Geddes, M. , 61, 92, 143 Hillestad, T.E. , 340 Gervase of Canterbury , 115 Hindley, K.B. , 33, 74, 121, 123, 294, 305, Gliba, G.W. , 222–224 306, 325 Gobin, L. , 340 Hocking, W.K. , 112 Goodall, W.M. , 11 Hoffmeister, C. , 9, 10, 18, 19, 25, 26, 40, 50, Gorelli, R. , 285 52, 56, 78, 80–84, 114, 116, 127, 130, 358 Index

131, 133, 143, 144, 147, 150, 153, 160, Kiang, T. , 93, 250 166, 167, 172, 178, 185, 187, 207–211, Kidger, M.R. , 123 214, 216–219, 223, 230, 235, 242, 243, King, A. , 172, 219, 237, 273, 289, 314, 317 284, 287, 290, 292, 305, 322, 329, 335, King, E.S. , 246 339 King, P. , 3 Holdsworth, D.A. , 39, 168, 221 Kingman, R. , 25 Houlden, M.A. , 306 Kinoshita, D. , 221 Hruska, A. , 199 Kirkwood, D. , 9, 31, 32, 72, 260, 271 Hubbard, J.S. , 257 Knight, G.M. , 91 Hughes, D.W. , 35, 80, 201, 320 Knopf, O.H.J. , 292 Hughes, V.A. , 92, 100, 106, 125 Knowles, J.H. , 223, 308 Humboldt, A. von , 192, 269, 270 Koch, B. , 308, 309 Hunt, J. , 321 Koep, J. , 110 Kohoutek, L. , 160 Koleva, K. , 117 I Komaki, K. , 71, 118 Ishikawa, C. , 243 Kondrat’eva, E.D. , 114, 280 Ishikawa, T. , 275 Kono, K. , 119 Ishmukhametova, M.G. , 114 Kopycheva, T.A. , 57, 66 Ito, T. , 221 Korlevic, K. , 156 Kornos, L. , 74 Korovkina, T.L. , 56, 57 J Koschack, R. , 174, 179, 195, 196 Jacchia, L.G. , 17, 145, 157, 158, 172, 173, Kowal, C.T. , 321 180, 181, 322 Kracht, R. , 108 Jackson, H.W. , 313 Krafft, G.W. , 256 Jäger, M. , 118 Kramer, E.N. , 38, 132, 181, 319 Jenniskens, P. , 35–37, 51, 76, 115, 120, 196, Kremneva, N.M. , 160 276, 282, 284, 340, 341 Kresák, L. , 241, 261, 281, 283, 284, 321, Jiang, Y. , 69 326, 327 Jobse, K. , 38, 186 Kresáková, M. , 306, 325–327 Johnstone Stoney, G. , 279 Kronk, G.W. , 222–224, 231 Jones, J. , 18, 22, 24, 27, 77, 124, 136, 155, Kushida, Y. , 112 158, 159, 162, 197, 201, 319, 336 Kviz, Z. , 160 Jones, P. , 19, 122

L K Laërtius, D. , 3 Kac, J. , 45, 53, 58 Lambert, R. , 110 Kämtz, L.F. , 245, 311 Langbroek, M. , 35, 116, 117, 241, 304 Karpov, V.K. , 57 Larkin, E.L. , 272 Kashcheyev, B.L. , 76, 77, 94–97, 101, 107, Laugier, P.A.E. , 191 108, 125, 126, 145, 150, 153, 155, 157, Lavoisier, A.L. , 7 167, 168, 202, 212, 213, 220, 228, 229, Le Verrier, U.J.J. , 278 242–244, 292, 295 Lebedinets, V.N. , 76, 77, 94–97, 101, 107, Kasuga, T. , 221 108, 125, 126, 145, 150, 153, 155, 157, Katz, B. , 119 167, 168, 202, 212, 213, 220, 228, 229, Kawamura, N. , 221 242–244, 292, 295 Kazimirchak-Polonskaya, E.I. , 84, 132, 280 Leichenok, V.K. , 66 Kegler, I. , 195, 196 Lexell, A.J. , 131, 132 Khan, M.A.R. , 283, 284, 308 Lichtenberg, G.C. , 7 Khotinok, R.L. , 275 Lin, H.-C. , 221 Index 359

Lindblad, B.A. , 19, 20, 25, 26, 51, 53, 66, 73, Miyasaka, S. , 221 74, 119, 120, 129, 133, 145, 157, 217, Mizser, A. , 196 218, 240, 250, 261, 287, 303, 307, 329 Molau, S. , 45, 53, 58, 141, 215, 231, Locke, J. , 193 262, 285, 286 Loomis, E. , 68, 192, 256 Montaigne, J.L. , 255 Lovell, A.C.B. , 92, 100, 106, 125 Montanari, G. , 3, 4 Lowe, E.J. , 31, 272, 309, 311, 312 Morales, R. , 120 Lucy, Russell , 70 Morgan, J.E. , 167, 208 Lunsford, R. , 82, 116, 117, 127, 210, 243, Moya, E.M. , 199 323, 326, 340 Mrkos, A. , 71 Lüthen, H. , 118, 120 Murakami, T. , 279 Lynch, R. , 333 Murphy, D.J. , 39, 168, 221 Lyytinen, E. , 201, 341 Murray, C.D. , 35 Lyzhin, Y.V. , 276 Murray, G.C. , 68

M N Mailly, E. , 191 Nagaoka, H. , 11 Malakhaev, E.A. , 56 Nagy, Z.A. , 285 Malikov, N.S. , 66 Nakagawa, T. , 323 Malzev, V.A. , 72, 73, 111, 157, 317, 320 Nakamura, K. , 111, 117–120 Marsden, B.G. , 49, 66, 75, 108, 112, 157, 195, Nakamura, R. , 221 196, 217, 261, 264, 307 Nakano, S. , 108 Marsh, B.V. , 193, 312 Neslusan, L. , 181 Martinez, F. , 20 Neuhaus, M. , 193 Martynenko, V.V. , 56, 160 Neumayer, G. , 142 Maskelyne, N. , 6, 8 Newton, H.A. , 69, 89, 258–260, 270, 271, 279 Matous, B. , 119 Niessl, G. , 128 Mattey, S.B. , 47 Nilsson, C.S. , 20, 22, 55, 56, 76, 77, 95–98, Maverly, J.H. , 257 105, 125, 126, 130, 132, 135, 136, 145, McBeath, A. , 83, 84, 179, 231 146, 147, 150, 161, 164, 173, 175, 176, McCrosky, R.E. , 28, 38, 59, 66, 83, 153, 155, 188, 211, 220, 222, 228, 229, 233, 234, 157, 168, 208, 217, 219, 242–244, 261, 324, 325, 327, 330, 331 286, 287, 303, 305, 307, 322, 324 Nolle, M. , 308 McIntosh, B.A. , 37, 72, 93, 250 Nolthenius, R. , 121, 122 McIntosh, R.A. , 9, 61, 82, 92, 129, 133, 143, Nose, K. , 240 165, 172, 177, 207, 219, 247, 335 Novoselnik, F. , 156 McKinley, D.W.R. , 144 McLeod, N.W. III , 19, 119, 122, 149, 174, 229, 247, 287, 323, 339 O McNaught, R.H. , 12, 281 Oates, R. , 148 Mellish, J.E. , 75 Obrubov, Y.V. , 37, 318, 319 Messenger, S. , 80 Ohtsuka, K. , 99, 108, 221, 323, 325, 327, 340 Messier, C. , 131 Olbers, H.W.M. , 270 Michaelis, R. , 238 Olech, A. , 224 Mikusek, J. , 160 Olivier, C.P. , 9, 10, 12, 47, 81, 91, 92, 110, Miller, F. , 312 112, 113, 147, 194, 208, 223, 232, 246, Milligan, W.H. , 91, 237 247, 249, 260, 272, 273, 282, 283, 286 Millman, P.M. , 99, 100, 195, 315 Olmsted, D. , 8, 266 Milon, D. , 274 Ono, K. , 100 Mims, S.S. , 85 Öpik, E.J. , 78, 129, 198, 219 Miskotte, K. , 282 Oppolzer, T.R. , 70, 278 360 Index

P Roggemans, P. , 195, 199, 200, 316, 318 Pajdusakova, L. , 49, 71 Roman, A. , 285 Pankenier, D.W. , 69 Roth, K.W. , 130, 135, 335 Papousek, J. , 243 Routledge, N.A. , 41 Parker, P. , 257 Roy, F. , 119, 122 Parsons, S.J. , 11, 238 Russell, H.N. , 70 Pearlmutter, A. , 23 Ryabova, G.O. , 319, 321 Perrine, C.D. , 260 Ryves, P.M. , 32, 91 Perry, S.J. , 258 Peters, C.F.W. , 278 Petersen, N.D. , 274 S Phillips, M. , 120 Saare, A. , 79 Phillips, R. , 256 Safonov, S.V. , 66 Pierce, J.A. , 239 Sagan, C. , 115 Plavec, M. , 318, 320 Sagayama, T. , 108 Pliny the Elder , 2, 3, 7 Sarenczky, K. , 285 Pons, J.L. , 255 Sauveur, D. , 191 Pope, J.T. , 329 Savill, M. , 262 Pope Sixtus II , 190 Sawyer, E.F. , 151, 166, 194, 313, 328 Porter, A. , 262 Schaeffer, G.C. , 191, 192 Porter, J.G. , 78, 132, 250 Schafer, J.P. , 11 Porubcan, V. , 72–74, 250, 295, 304 Schiaparelli, G.V. , 9, 18, 23, 25, 46, 80, 82, Posen, A. , 28, 38, 59, 66, 83, 153, 155, 157, 122, 151, 194, 202, 223, 225, 257, 168, 208, 217, 219, 242–244, 261, 286, 278, 289 287, 303, 305, 307, 322, 324 Schmidt, J.F.J. , 89, 142, 150, 193, 342 Povenmire, H.R. , 119 Schulhof, L. , 85 Prentice, J.P.M. , 33, 52, 70, 71, 119, 143, 184, Schwassmann, A. , 117 194, 207, 237, 238, 242, 246, 248, 249, Secchi, A. , 9, 193, 194, 255 252, 261, 274, 290, 338 Šegon, D. , 156, 157 Pringle, J. , 5 Sekanina, Z. , 15–17, 19–21, 24–28, 38, 39, 48, Ptolemy , 2 49, 52, 53, 57, 66, 73–75, 77, 81, 83, Puastalle, A. , 193 84, 85, 94–98, 101, 105, 107, 108, 112, 113, 122, 123, 125, 126, 130–133, 135, 136, 146, 147, 150, 153, 155, 157, 161, Q 168, 173–176, 181, 182, 185, 186, 188, Quetelet, L.A.J. , 30, 68, 190, 191, 245 202, 208, 212, 217, 218, 220, 222–225, 228, 229, 233, 234, 239–241, 250, 261, 264, 292, 295, 325, 327, 330, 331, 341 R Sekiguchi, T. , 221 Rada, W.S. , 271 Seneca , 2 Raillard, F. , 256 Shain, C.A. , 332 Rama Rao, P.V.S. , 305, 322 Shaporev, S.D. , 132 Ramesh, P. , 305, 322 Shearer, G. , 19 Rao, J. , 196 Shestaka, I.S. , 319 Reid, I.M. , 39, 168, 221 Shiba, Y. , 323 Rendtel, J. , 113, 141, 179, 196, 200, 210, 215, Shigeno, Y. , 304, 305, 323, 325, 327, 231, 250, 262, 285, 286, 318, 334 331, 332 ReVelle, D.O. , 330, 331 Shimoda, C. , 100, 323 Reyes, F. , 285 Shioi, H. , 340 Reznikov, E.A. , 280 Sibata, Y. , 117 Rice, H.S. , 181 Simek, M. , 316 Ridley, G.W. , 40 Simmons, K. , 108, 126 Ridley, H.B. , 78, 333, 334 Simmons, W. , 19 Index 361

Simpson, J.W. , 59 Tsarev, N.A. , 57 Siomi, K. , 118 Tupman, G.L. , 89–91, 142, 183, 213, 288, 289 Sitarski, G. , 78, 79 Turco, E.F. , 111, 167 Sizonov, G.N. , 228 Tuttle, H.P. , 193, 277 Skellett, A.M. , 11 Twining, A.C. , 259, 266–268, 270, 271 Skelsey, D. , 126 Skokic, I. , 156 Sleeter, K. , 222–224 U Smieton, J. , 259 Ueda, M. , 108, 163 Smirnov, N.V. , 57, 66, 276 Ueyama, Y. , 331 Smith, C. , 119 Usanin, V.S. , 114 Smith, E.R. , 68 Usuki, K. , 112 Smith, F.W. , 110, 111, 223, 260, 342–343 Smyth, P. , 271, 272 Soldevilla, V. , 105 V Southworth, R.B. , 10, 25, 95, 119, 129, 200, Valerian , 190 201, 243, 261, 263 Valsecchi, G.B. , 281 Spalding, G.H. , 317, 318, 340 van Flandern, T. , 201 Spurny, P. , 282, 285 van Leeuwen, G.D. , 282 Srirama Rao, M. , 305, 322 van Musschenbroeck, P. , 189 Stanley, A.D. , 192 van Vliet, M. , 35 Steel, D.I. (also Olsson-Steel) , 53, 107, 162, van Wassenhove, J. , 196 243, 294, 295 Vanysek, V. , 338 Stepanek, J. , 209 Vaubaillon, J. , 80, 241 Stephan, E.J.M. , 259 Velkov, V. , 113, 117 Stephenson, F.R., 271 Venter, S.C. , 332–334 Stewart, G.S. , 11, 238 Vida, D. , 156 Stohl, J. , 73, 74, 295, 304 Viljev, M.A. , 309 Ströbele, S. , 308 Vincent, R.A. , 39, 168, 221 Sugimoto, M. , 108 Vlcek, J. , 209 Svoren, J. , 73 Vratnik, A. , 209 Swann, D. , 111, 112, 119 Swift, L. , 193 Sytinskaja, N.N. , 111, 152, 237 W Wachmann, A.A. , 117 Walferdin, F.H. , 191 T Walker, A. , 69 Tacchini, P. , 150, 151 Walker, S.C. , 82 Taguchi, Y. , 196 Waller, T.H. , 142, 313 Taibi, R. , 20, 309 Wallis, J. , 4 Takeuchi, Y. , 240 Warren, J. , 50 Talbot, F.W. , 121 Wasson, J.T. , 330 Tedesco, E.F. , 38 Watanabe, J.-I. , 221 Teichgraeber, A. , 18, 209 Watanabe, K. , 240 Tempel, E.W.L. , 277 Watkins, C.D. , 16 Tepliczky, I. , 210, 285 Weber, M. , 123, 180 Ter Kuile, C.R. , 282 Webster, N. , 189 Terentjeva, A.K. , 53, 59, 84, 99, 100, 116, Weinek, L. , 10 117, 129, 132, 146, 214, 280, 290, 303, Weiss, A.A. , 61, 126, 163, 220, 333, 334 305, 319, 326 Weiss, E. , 32, 70, 75, 90, 177, 257, 328 Theognis , 3 Welch, P.G. , 215 Trigo-Rodríguez, J.M. , 105, 123, 214 Welsh, H. , 333 Trudelle, P. , 110 Wenz, W. , 38 362 Index

Weryk, R.J. , 18, 22, 24, 27, 38–40, 45, 55, 65, Wood, W.H. , 69, 142, 313 73, 77, 94, 95, 97, 98, 101, 124, 125, Worley, C.E. , 187, 223 135, 136, 155, 158, 159, 161, 162, 165, Wright, F.W. , 144, 172, 173, 180, 181, 227, 175, 180, 197, 211, 212, 221, 241, 249, 290, 291 251, 263, 264, 282, 296, 308, 316, 336 Wylie, C.C. , 273 West, J. , 19, 119, 122 Wetherill, G.W. , 330, 331 Whipple, F.L. , 17, 38, 73, 134, 135, 145, 147, X 157, 158, 172, 173, 180, 181, 185, 227, Xu, Z. , 69 290–292, 294, 307, 318, 321, 322, 324, 325 Whitney, B.S. , 52, 185, 238 Y Whitney, J.D. , 256 Yabu, Y. , 240 Widner, R. , 185 Yamamoto, I. , 118 Wiegert, P.A. , 18, 23, 24, 27, 36, 38–40, 45, Yamamoto, M.-Y. , 304, 305, 323, 325, 327, 55, 65, 73, 77, 94, 95, 97, 98, 101, 331, 332 124, 125, 135, 136, 155, 158, 159, Yau, K.K.C. , 201 161, 162, 165, 175, 180, 197, 211, Yeomans, D.K. , 93, 107, 250, 280 212, 221, 249, 251, 263, 264, 282, Yoshikawa, M. , 108 296, 308, 316, 336 Yosii, K. , 118 Williams, I.P. , 35, 37, 320, 321, 326 Younger, J.P. , 39, 168, 221 Willis, E.C. , 272 Youssef, M.N. , 34 Wilson, F. , 33, 47, 109 Wisniewski, M. , 156, 157 Withers, P. , 115 Z Wolf, R. , 193 Zalcik, M. , 119 Wong, D.K. , 18, 22, 23, 24, 27, 38–40, 45, Zarubin, P. , 282 55, 65, 73, 77, 94, 95, 97, 98, 101, 124, Zay, G. , 116, 117, 210 125, 135, 136, 155, 158, 159, 161, 162, Zezioli, G. , 23, 25, 46, 80, 122, 151, 213, 223, 165, 175, 180, 197, 211, 212, 221, 249, 258, 288, 289, 328 251, 263, 264, 282, 296, 308, 316, 336 Zhukov, G.V. , 114 Wood, G. , 312 Znojil, V. , 47, 153, 154, 242, 243, 248, 249 Wood, J. , 50, 52, 60, 75, 79, 126, 131, 148, Zoładek, P. , 156, 157 164, 168, 174, 179, 217, 243, 262, 308 Zvolánková, J. , 179