DOCSLIB.ORG

On the Nature of the Anti-Tail of Comet Kohoutek (1973F)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
On the Nature of the Anti-Tail of Comet Kohoutek (1973F) zcAavs 27, 135-146 (1976) On the Nature of the Anti-Tail of Comet Kohoutek (1973f). I1. Comparison of the Working Model with Ground-Based Photographic Observations ZDENEK SEKANINA Center for Astrophysics, Harvard College Observatory and Smithsonian Astrophysical Observatory, Cambridge, Massachusetts 02138 AND FREEMAN D. MILLER Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48104 Received May 13, 1975; revised June 3, 1975 Photographic observations of the anti- tail of Comet Kohoutek ( 1973f ), obtaitled at the Cerro Tololo Inter-American Observatory, are photometrically reduced and the results compared with a recently formulated working model of the anti- tail. The applied technique of photometric reduction is described, and the radial and transverse profiles of the anti-tail, corrected for the effects of atmospheric extinction and the variable intensity of the ambient sky, are derived. Brightness variations in time are also studied, The most important result reached so far is a quantitative confirmation of the previously suggested hypothesis, arguing that dust particles in the anti-tail suffered a significant loss in radius due to evaporation near the perihelion passage. We find that only particles initially larger than 100-150/~m in diameter (at an assumed density of I gcm -3) survived. Numerically, however, this result is still preliminary, because the dynamical effect associated with particle evaporation remains to be explained. It is also tentatively suggested that. the emission rate of the dust from the comet was probably comparable with the rates derived earlier for Comets Arend-Roland (1957 III) and Bennett (1970 II). I. INTRODUCTION then tested quantitatively. The photo- graphic material studied here was secured A working model was recently formu- under the supervision of the second author. lated for the anti-tail of Comet Kohoutek The photometric reduction and physical (Sekanina, 1974; referred to hereafter as interpretation are due to the first author. Paper I). The model was based on the Finson-Probstein (1968) theory of dust II. TttE MICHIGAN PROGRAM OF comets and fitted reasonably well the semi- PHOTOGRAPHIC OBSERVATIONS OF COMETS quantitative descriptions of the anti-tail by a number of observers, including the The plates described in Section III form Skylab III astronauts. In the present paper, part of a program of comet observations the radial and transverse brightness pro- initiated by the second author in 1950 with files and the time variations in the surface the Curtis-Schmidt telescope (61/91cm, brightness of the anti-tail are established f/3.5, 96':6mm -~) of the University of from plates of the comet taken at the Cerro Michigan. ]in addition to unfiltered "blue" Tololo Inter-American Observatory, near plates, exposures have been taken through La Serena, Chile, and the working model is red filters to suppress the CO t emissions of Copyright (c) 1976 by Academic Press, Inc. 135 All rights of reproduction in any form reserved. Printed in Great Britain 136 SEKANINA AND MILLER Type I tails relative to the scattered Still- telescope between January 16 and Feb- light of the Type II tails, on which the ruary 15, 1974. Five plates, taken on former are often superposed. The extent to January 23, 24, and 26 and February 12 which the suppression is successful has and 15, are 098-02 panchromatic enmlsions varied from one comet to another (Miller, combined with an RG1 filter to provide 1958, 1962). The development of a model maximum sensitivity near 661~(1A and of dust tails by Finson and Probstein (1968) to cut off the visible spectrum below has stimulated interest in the study of the A ~ 5900A. The photometric system thus Michigan material, and analyses for Comets obtained is similar to the R system of Seki-Lines 1962 III (Jambor, 19731 and Johnson and Mitchell (1962). The other Bennett 1970 I] (Sekanina and Miller, seven plates, taken on January 16, 17, 20, 1973) have already appeared. 21, 23, 25, and 27, are standard 103a-O From the first, the comet-program plates emulsions without filter. The red-sensitive have been photometrically calibrated with plates are of primary interest, both a 14-tube spot sensitometer designed by because they span a longer interval of E. B. Weston; when the telescope was time and because they show the anti-tail transferred from Michigan to Cerro Tololo, better. The guiding of the ,lanuary 24 the sensitometer accompanied it. Since the plate was somewhat imperfect, so only the precision of the sensitometer calibration is other four plates, two in January an(I two critical, the photometric scale was meas- in February, have been photometricall.v ured photoelectrically by W. Liller in 1951 studied. The four observations are listed and 1955 and by S. M. Simkin in 1965. The in Table 1. average deviation from the mean scale of Of much concern has been the very low the three independent measurements for altitude of the comet. At the end of the each spot is ±0.04mag; a more detailed exposure, the comet was only slightly over discussion of the calibration tests can be 1() ° above the horizon on plates 15520, tbund in a paper by Miller (1967). A calibra- 15687, and 157(i13 and about 7 ° above the tion exposure is made for each comet horizon on 15554! Thanks to the excellent photograph through the same filter used in sky at Cerro Tololo, the plates are still the comet exposure and on a plate taken photometrically valuable, but the very from the same box and developed with the low altitude of the comet is a source of two comet [)late. The length of the calibration potential complications for the photometry exposure is the same as that, for the comet. of the plates, namely the effects of dif- ferential refi'action and strongly variable sky brightness. In addition, atmospheric III. THE (~ERRO TOLOLO PHOTOGRAPHS extinction, which is severe at these alti- A total of 12 calibrated plates were taken tudes even in the red section of the at Cerro Tololo with the Curtis-Schmidt spectrum, also needs to be accounted for. TABLE I (~ERRO TOLOLO ]~E|)-SENSITIVE PHOTOGfCAPHS OF (~OMET ]%OHOUTEK (098-02 EMULSION "tVITHAN RGI FILTEU) C,omet's posit, ion 1950.0 Phas(' Date UT /1 r angle Altitude at Exl)oSur(~ Platte 1974 R.A. I)eel. (AU) (AU) ~ midexposure" (mm) 15520 Jan. 23.0495 23n40~. 67 +@ 46~5 O.853 O.837 71 ~2 1316 20 15554 Jan. 26.0614 0n07 .m3(~ +3c 12:2 0.894 (k909 66.2 I 1~8 50 15687 Feb. 12.0572 lh54m21 +12~01:9 1.257 1.278 45 ~ 16~3 60 15703 Feb. 15.0566 2h07T40 +12 57~7 1.334 1.338 43'14 16~2 60 " Not corrected tbr t~ depressed horizon. THE ANTI-TAIL OF COMET KOHOUTEK (1973f). II 137 The differential-refraction effect has been quantitatively analyzed following the procedure described in Appendix A. PLATE 15 Numerically, refraction has been found to affect the angular distance from the nucleus on the four plates by less than 1%, and the position angle, by no more than 0.1 ° at an angular distance of 1 ° from the nucleus and no more than 0.2 ° at 2 +. The effect of variable sky brightness proved considerably more severe. It so happened that the brightest section of the anti-tail was directed almost exactly toward the horizon on all the plates, so that the maximum brightness gradient of the sky projected unforeshortened along the anti-tuil. In addition, all exposures began during astronomical twilight (with the Sun's depression between 15 + and 17°), and almost the whole 15520 exposure was taken during twilight (with the Sun's depression at midexposure 17+). To demon- strate the extent of interference, we I000 mention that the relative gradient of the sky brightness on plates 15520 nad 15554 /• reached a maximum rate of 7% per degree S(;~,LE of altitude, while at the same time the intrinsic surface brightness of the anti-tail 0 I0' 20 ~ 50 / Fro. 1. A two-dimensional scan of plate 15687. amounted to only some 4-6% of the sky Scanning aperture is 9'.'7 by 9'.'7. The anti-tail brightness at 15' from the nucleus and points to the bottom of the scan, and the regular about 1-2% at 25". dust tail to the top. The numbers indicate the relative surface brightness, uncorrected for the contribution from the sky. IV. THE TECHNIQUE OF PHOTOMETRIC REDUCTION known positions have been used to fix the The technique for reducing the plates position angles. The position of the comet was essentially dictated by the trouble- on the plates was measured relative to the some observing conditions. Because of the ambient stars and reduced routinely with complicated character of the sky-bright- the use of the method of dependences. The ness variations near the horizon, it was result has also been checked by computing virtually impossible to use the standard the expected topocentric position of the two-dimensional scans to map the sky comet from Marsden's (1974) definitive "noise" over the area occupied by the orbit. The measured and computed posi- anti-tail (see Fig. 1). Preferable, because tions agree within 2" on plate 15520, more revealing, are one-dimensional radial 7" on 15554, 8" on 15687, and 13" on 15703. tracings, passing through the comet's These residuals can be accounted for nucleus and effectively covering the whole entirely by the uncertainty in the location anti-tail. Each radial scan is defined by on the plates of the nucleus in the strongly the position angle, and the "noise" varia- overexposed coma, which is almost 2' in tions in the respective section of the anti- diameter.
Load more

Recommended publications
  • January 12-18, 2020
    3# Ice & Stone 2020 Week 3: January 12-18, 2020 Presented by The Earthrise Institute This week in history JANUARY 12 13 14 15 16 17 18 JANUARY 12, 1910: A group of diamond miners in the Transvaal in South Africa spot a brilliant comet low in the predawn sky. This was the first sighting of what became known as the “Daylight Comet of 1910” (old style designations 1910a and 1910 I, new style designation C/1910 A1). It soon became one of the brightest comets of the entire 20th Century and will be featured as “Comet of the Week” in two weeks. JANUARY 12, 2005: NASA’S Deep Impact mission is launched from Cape Canaveral, Florida. Deep Impact would encounter Comet 9P/Tempel 1 in July of that year and – under the mission name “EPOXI” – would encounter Comet 103P/Hartley 2 in November 2010. Comet 9P/Tempel 1 is a future “Comet of the Week” and the Deep Impact mission – and its results – will be discussed in more detail at that time. JANUARY 12, 2007: Comet McNaught C/2006 P1, the brightest comet thus far of the 21st Century, passes through perihelion at a heliocentric distance of 0.171 AU. Comet McNaught is this week’s “Comet of the Week.” JANUARY 12 13 14 15 16 17 18 JANUARY 13, 1950: Jan Oort’s paper “The Structure of the Cloud of Comets Surrounding the Solar System, and a Hypothesis Concerning its Origin,” is published in the Bulletin of the Astronomical Institute of The Netherlands. In this paper Oort demonstrates that his calculations reveal the existence of a large population of comets enshrouding the solar system at heliocentric distances of tens of thousands of Astronomical Units.
    [Show full text]
  • Kohoutek Is Coming! New York, New York September I0, 1973
    INSTITUTE OF CURRENT rORLD AFFAIRS ATW-20 Kohoutek Is Coming! New York, New York September I0, 1973 Mr. Richard H. Nolte Institute of Current World Affairs 535 Fifth Avenue New York, New York 10017 Dear Mr. Nolte: Our planet earth is about to be visited by a ghost. The name of the visitor is "1973f" or "Kohoutek," and it is a great comet, perhaps the greatest of the century. Comets have been called the ghosts of the solar system because they are so insubstantial relative to their size and brightness. Percival Lowell called them "bagfuls of nothing," and, in fact, their most eye- catching features great tails of enormous length and brilliance seem to be nothing more than tenuous streamers of gas excited to lumin- escence by the radiation of the sun. The great comet now rushing at us from the far corners of space was discovered on March 7th of this year by Dr. Lubo Kohoutek of the Hamburg Observatory in Bergedorf, West Germany. It showed up on a photo- graphic plate as a faint, diffuse object with no tail in the constel- lation of Hydra. Subsequent observations made possible the calculation of the orbit of this body. We now know that it will reach perihelion, its closest approach to the un, on December 24th, and it should be spectacu- larly visible to the naked eye for about six weeks before and after that date. The word "comet" comes from the Greek "hairy star." Comets are members of the solar system. Like planets they revolve in orbits around the sun.
    [Show full text]
  • Monthly Newsletter of the Durban Centre - May 2018
    Page 1 Monthly Newsletter of the Durban Centre - May 2018 Page 2 Table Of Contents Chairman’s Chatter …...…………………….…...….………..….…… 3 The Man Of Mars ……..………………………………...…….……….. 5 At The Eye Piece ……………...…………………………….….…….... 9 The Cover Image - Eta Carinae ……………….……….………….... 11 Comets Continued.………………………………..……..………….... 14 The Green Flash …….………………...…….………..………………. 21 Sutherland 2018 …..…..………………………………..…..………… 23 The Month Ahead …..…………………...….…….……………..…… 27 Minutes Of The Previous Meeting ……………………..…….……. 28 Public Viewing Roster …………………………….……….…..……. 29 Pre-loved Astronomical Equipment ..…………..….…........…… 30 Committee Nomination Form For 2018-19 …………………..….. 31 Image by Angus Burns from Newcastle, KZN Member Submissions Disclaimer: The views expressed in ‘nDaba are solely those of the writer and are not necessarily the views of the Durban Centre, nor the Editor. All images and content is the work of the respective copyright owner Page 3 Chairman’s Chatter By Mike Hadlow Dear Members, We are moving into May and autumn and are starting to get into a period of clearer skies and great viewing. We have certainly had some fantastic viewing evenings over the last 2 weeks. Particularly, the end of last week. For those of you who have been watching the skies, in the late evening we could see a risen Scorpio following Jupiter, with both Mars and Saturn following closely. Three of the five visible planets in one night and if you looked a little earlier you would have seen Venus on the western horizon just after sunset! Our activities over the last month were dominated by our trip to Sutherland which turned out to be a most fantastic trip. Not only did the skies play ball, (the Cape rain held out till the 26 April), but our hosts at SALT did the usual, taking us through SALT and in the evening through the control centre where we had the working astronomers giving us a presentation.
    [Show full text]
  • Dust in Comet 103P/Hartley 2 Coma During EPOXI Mission Q ⇑ E
    Icarus 222 (2013) 774–785 Contents lists available at SciVerse ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Dust in Comet 103P/Hartley 2 coma during EPOXI mission q ⇑ E. Hadamcik a, , A.K. Sen b, A.C. Levasseur-Regourd c, R. Gupta d, J. Lasue e, R. Botet f a UPMC (U. P. & M. Curie, Sorbonne Universités), LATMOS/CNRS, 11 Bld d’Alembert, 78280 Guyancourt, France b Assam Univ., Silchar 788 001, India c UPMC (U. P. & M. Curie, Sorbonne Universités), LATMOS/CNRS, 4 Place Jussieu, 75005 Paris, France d IUCAA, Post Bag 4, Ganeshkhind, 411007 Pune, India e Univ. de Toulouse, UPS-OMP, IRAP, BP 44346, 31028 Toulouse, France f Univ. Paris-Sud, LPS/CNRS, Bat. 510, 91405 Orsay, France article info abstract Article history: The Deep Impact spacecraft flew by Comet 103P/Hartley 2 on 4 November 2010 (EPOXI mission). In situ Available online 16 July 2012 observations are complemented by a systematic ground- and space-based observation campaign. In the present work, imaging polarimetry is used to emphasize different dust regions in the coma and follow Keywords: their evolution over a period including the EPOXI fly-by. Comets, Dust On the intensity images, the coma is asymmetric with an important tailward feature. Jets in the sun- Comets, Coma ward direction are observed to present an extension that depends on the nucleus phase. The azimuthal Polarimetry integrated intensity presents a nominal radial decrease (À1 in log–log scale) for optocentric distances lar- ger than a few hundred kilometers. Through cometary continuum narrow band filters, the aperture polar- ization decreases with the optocentric distance.
    [Show full text]
  • Kudo-Fujikawa\), C/2002 V1 \(NEAT\
    A&A 528, A142 (2011) Astronomy DOI: 10.1051/0004-6361/201016250 & c ESO 2011 Astrophysics Molecular investigations of comets C/2002 X5 (Kudo-Fujikawa), C/2002 V1 (NEAT), and C/2006 P1 (McNaught) at small heliocentric distances N. Biver1, D. Bockelée-Morvan1, P. Colom1, J. Crovisier1, G. Paubert2,A.Weiss3, and H. Wiesemeyer3 1 LESIA, CNRS UMR 8109, UPMC, Université Paris-Diderot, Observatoire de Paris, 5 pl. Jules Janssen, 92195 Meudon, France e-mail: [email protected] 2 IRAM, Avd. Divina Pastora, 7, 18012 Granada, Spain 3 Max Planck Institute for Radio Astronomy, PO Box 20 24, 53010 Bonn, Germany Received 2 December 2010 / Accepted 14 January 2011 ABSTRACT We present unique spectroscopic radio observations of comets C/2002 X5 (Kudo-Fujikawa), C/2002 V1 (NEAT), and C/2006 P1 (McNaught), which came within rh ≈ 0.2 AU of the Sun in 2003 and 2007. The molecules OH, HCN, HNC, CS, and CH3OH + were detected in each of these comets when they were exposed to strong heating from the Sun. HC3NandHCO were detected in comets C/2002 X5 and C/2006 P1, respectively. We show that in these very productive comets close to the Sun screening of the photodissociation by the Sun UV radiation plays a non-negligible role. Acceleration of the gas expansion velocity and day-night −5 −1 asymmetry is also measured and modeled. The CS photodissociation lifetime was constrained to be about 2.5 × 10 s at rh = 1AU. The relative abundances are compared to values determined from more distant observations of C/2002 X5 or other comets.
    [Show full text]
  • Comet ISON! (Comet of the Century?)
    1 Mr. Justin J McCollum (BS, MS Physics) Lab Physics Coordinator Dept. of Physics Lamar University 2 Table of Contents ISON network………………..….………………….…...3 – 6 C/2012 S1 Discoverers………….…...……….…...…7 – 10 CoLiTech System…………………….……….….………...11 Discovery & Prediscovery……………….…….………...12 Early Orbital Analysis…………………….……….…….…13 Speculations of Comet ISON…………..…………14 - 15 Oort or Oort – Opik Cloud………….……........16 – 17 Origin of Comet ISON……….………………….……….18 Sungrazer Comets…………………………………….19 - 20 Evolution of Comet ISON………………………………21 Facts about Comet ISON…………………....…..22 – 23 ISON a Pristine Comet?...............................24 – 25 Photometry & Current Brightness……………..26 – 27 Nature and State of the Coma…………………..28 – 30 Central Nucleus of Comet ISON………………31 – 32 Nucleus to the Tail……………………………….…..……33 Nature & State of the Tail…………………………34 – 35 Future & Expectations………………………….....36 – 39 Getting to know more about Comets!...........40 – 46 After Perihelion Passage!..............................47 – 49 Catching the Comet in December!…………….50 – 53 ISON in the Daytime…….…………………………….…54 NASA Involvement!.............................................55 C/2012 S1 Orbital Structure………………..…………..56 Ephemeris Terminology………………………………...57 Data Spreadsheet Introduction………………………..58 Data Table Spreadsheets…………………………..59 - 60 Comet ISON Updates………………………………61 - 62 Knowing where & how to find ISON……...…63 – 64 Current ISON Observing Campaign………….65 – 66 Comet ISON photo contest…………………………….67 End Page……………………………………………………...68 3 Imperial Academy of
    [Show full text]
  • A Great Comet Coming? Comet ISON May Grow Into a Truly Incredible Sight
    OBSERVING Exploring the Solar System John E. Bortle A Great Comet Coming? Comet ISON may grow into a truly incredible sight. Or not. A faint and distant comet discovered by Russian ama- potential for becoming a spectacular object, comets are teur astronomers Vitali Nevski and Artyom Novichonok notoriously unpredictable. Observers need only recall the in September is going to be big news in late 2013. But dismal failure of Comet Elenin in 2011, which was also whether it will become a great comet remains unclear. touted to become a grand spectacle. From the outset, Comet C/2012 S1 (also known as As this is being written, only a few weeks after the Comet ISON after the International Scientific Optical discovery with Comet ISON still 6 a.u. from the Sun, it’s Network involved with its discovery) was wrapped in a unclear whether the comet’s orbit is parabolic or very swirl of hype and controversy. The initial orbital elements, highly elliptical — an important factor for the comet’s indicating that the comet will pass just 0.01 astronomical future performance. A parabolic orbit suggests that the unit (a.u.) from the Sun, generated a firestorm of wild comet is coming in from the Oort Cloud for a first-time speculation across the internet. Poor understanding of swing by the Sun. Such objects often brighten very early, how comets typically behave led people to post early com- raising high hopes, but once they come within about 1½ ments suggesting that Comet ISON would become 100 a.u. of the Sun their brightening can radically slow.
    [Show full text]
  • Comet Kohoutek (NASA 990 Convair )
    Madrid, UCM, Oct 27, 2017 Comets in UV Shustov B., Sachkov M., Savanov I. Comets – major part of minor body population of the Solar System There are a lot of comets in the Solar System. (Oort cloud contains cometary 4 bodies which total mass is ~ 5 ME , ~10 higher than mass of the Main Asteroid Belt). Comets keep dynamical, mineralogical, chemical, and structural information that is critically important for understanding origin and early evolution of the Solar System. Comets are considered as important objects in the aspect of space threats and resources. Comets are intrinsically different from one another (A’Hearn+1995). 2 General comments on UV observations of comets Observations in the UV range are very informative, because this range contains the majority of аstrophysically significant resonance lines of atoms (OI, CI, HI, etc.), molecules (CO, CO2, OH etc.), and their ions. UV background is relatively low. UV imaging and spectroscopy are both widely used. In order to solve most of the problems, the UV data needs to be complemented observations in other ranges including ground-based observations. 3 First UV observations of comets from space Instruments Feeding Resolu Spectral range Comets Found optics tion Orbiting Astronomical 4x200mm ~10 Å 1100-2000 Å Bennett OH (1657 Å) Observatory (OAO-2) ~20 Å 2000-4000 Å С/1969 Y1 OI (1304 Å) 2 scanning spectrophotometers Launched in 1968 Orbiting Geophysical ~100cm2 Bennett Lyman-α Observatory (OGO-5) С/1969 Y1 halo Launched in 1968 Aerobee sounding D=50mm ~1 Å 1100-1800 Å Tago- Lyman-α halo rocket Sato- wide-angle all-reflective Kosaka spectrograph С/1969 Y1 Launched in 1970 Skylab 3 space station D=75mm Kohoutek Huge Lyman- Launched in 1973 С/1969 Y1 α halo NASA 990 Convair D=300mm Kohoutek OH (3090Å) aircraft.
    [Show full text]
  • The Objective View March 1996 Newsletter of the Northern
    The ObjectiveView March 1996 Newsletter of the Northern Colorado Astronomical society Lee Youngblood, President 669-8321. Brad Jarvis, Vice President 686-5369 [email protected] David Chamness,Secretary 482-1794 [email protected] Mike McCarthy, Treasurer 493-6428 Dan Laszlo, TOV Editor 498-9226 [email protected] WWW Page: httpt/ /lamar.colostate.edu/-rmoench/ncasrdm.html Meetings first Thursday of each Month Next Meeting: March 7, 1996,7:30Pm Harold Porter, "Or6ital Mechanicsfor Everyone(bring your calculator!)" UpcomingEvents: February 1 Meeting: Comet Hale-Bopp, by Dr. Roger Don't Miss Comet HYakutake! CuIver Comet Hyakutake 1.996 82 is predicted to reach naked Dr. Culver haced the traditional association of bright eye visibility in late March-Aprll 1996. comets with dire events, citing the record of Halley's comet in the Bayeaux Tapestry, in its chronicle of the March 7 Meeting Directions invasion by William the Conqueror. Christian armies Aspen Medical Center, Building H' 2001 S Shields St were alarmed in 1456 by the aPPearance of comet which Fort Collins (near Rolland Moore Park) hung like a Turkish sword in the sky, but took heart when In Fort Collins, from the CSU campus go South on Shields the comet was excommunicated by the Pope. However, St about 0.5 mile past W Prospect Rd. Turn Right into comets continue to be perceived as ominous, evidenced by Spring Creek Medical Park. tracts published at the passage of Comet Kohoutek in From Loveland, take Taft Ave, North. From W Drake Rd L973, and Halley's Comet in 1985. Numerous dire events, in Fort Collins, go about 0.5 mile North and turn Left into such as World War II, have been unhearalded by comets, Spring Creek Medical Park.
    [Show full text]
  • The Comet's Tale
    THE COMET’S TALE Newsletter of the Comet Section of the British Astronomical Association Volume 7, No 2 (Issue 14), 2000 October WHAT IS THE DIFFERENCE BETWEEN ASTEROIDS & COMETS? From Science-Week via CCNet astronomical units from the Sun, that astronomers should now perhaps due to the influence of consider these objects as members Other than the moons of the massive Jupiter just outside the of highly diverse family: the various planets, the chief small asteroid belt. Until recently, the small bodies of the Solar System. bodies of the solar system are shapes and surface features of comets and asteroids. asteroids were a matter of 2) If all comets were solid dirty conjecture; during the past balls of water ice, then their bulk In general, a comet is a decade, however, significant densities would be approximately kilometre-size chunk of ice and direct observations of asteroids 1 gram per cubic centimetre. But associated dust and debris. The have been relayed back to Earth some comets have apparent low- Oort cloud is an apparent from spacecraft. density structures that are made spherical shell of comets 10,000 from several bits held together by to 100,000 AU from the Sun and Classical astronomers have little more than their own self- the proposed source of comets categorised comets and asteroids gravity. This conclusion arose that orbit the Sun. The cloud is as distinctly different entities with after some comets were observed at the extreme edge of the Sun's different histories and to break up as a result of tidal influence, halfway to the nearest compositions, but recent evidence forces from either the Sun or star, and it is believed that when is blurring the conceptual Jupiter, and more than two dozen the cloud is perturbed by passing boundary between these two other comets have split apart for stars, comets may be sent into a groups of small Solar System no obvious reason at all.
    [Show full text]
  • Ice& Stone 2020
    Ice & Stone 2020 WEEK 53: DECEMBER 27-31 Presented by The Earthrise Institute # 53 Authored by Alan Hale This week in history DECEMBER 27 28 29 30 31 1 2 DECEMBER 27, 1984: A team of American meteorite hunters finds the meteorite ALH 84001 in the Allan Hills region of Antarctica. This meteorite was found to have come from Mars, and in 1996 a team led by NASA scientist David McKay reported the presence of possible “microfossils” and other evidence of potential biological activity within it. This is the subject of a previous “Special Topics” presentation. DECEMBER 27, 2020: The main-belt asteroid (41) Daphne (around which a small moon, named Peneius, was discovered in 2008) will occult the 7th-magnitude star HD 49385 in Monoceros. The predicted path of the occultation crosses Oregon, the northern Pacific Ocean, the southern part of the island of Sakhalin, far southeastern Russia, far northeastern China, northern Mongolia, and east-central Kazakhstan. DECEMBER 27 28 29 30 31 1 2 DECEMBER 28, 1969: Amateur astronomer John Bennett in South Africa discovers the comet now known as Comet Bennett 1969i. Around the time of its perihelion passage in March 1970 it became a bright naked-eye comet and it is the first Great“ Comet” that I ever observed; it is a previous “Comet of the Week.” DECEMBER 28, 1973: Comet Kohoutek 1973f passes through perihelion at a heliocentric distance of 0.142 AU. Although it did not become the “Great Comet” that had been originally expected, it was nevertheless a moderately conspicuous naked-eye object and was an important comet scientifically.
    [Show full text]
  • Arxiv:2101.05267V3 [Astro-Ph.EP] 23 Mar 2021 (∼5Σ Significance) with Column Density N(HI) = (1.8 ± 0.09) × 1022 Cm−2
    Detection of the atomic hydrogen (HI) absorption line and continuum emission from comet C/2020 F3 (NEOWISE) using GMRT Sabyasachi Pal Indian Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata, India 700084 Midnapore City College, Paschim Medinipur, West Bengal, India 721129 Arijit Manna Midnapore City College, Paschim Medinipur, West Bengal, India 721129 and Ruta Kale National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University, Pune, India 411007 ABSTRACT Comets are the most primordial objects in our solar system which are made of icy bodies. Comets used to release gas and dust when it moves close to the Sun. The C/2020 F3 (NEOWISE) is a large periodic comet that is moving in a near-parabolic orbit. The C/2020 F3 (NEOWISE) is the brightest comet in the northern hemisphere after comet Hale-Bopp in 1997. Here we present the first interferometric high-resolution detection of the comet C/2020 F3 (NEO- WISE) using the Giant Metrewave Radio Telescope (GMRT). The observational frequency range is 1050{1450 MHz. We detect the radio continuum emission from this comet with flux density level 2.8{3.4 mJy between the frequency range 1050{1450 MHz. We also detect atomic HI absorption line at ν = 1420 MHz arXiv:2101.05267v3 [astro-ph.EP] 23 Mar 2021 (∼5σ significance) with column density N(HI) = (1:8 ± 0:09) × 1022 cm−2. The continuum emission from the comet in meter wavelength arises from the large Icy Grains Halo (IGH) region. Significant detection of C/2020 F3 in ∼21 cm indicates the presence of large size of particles in the coma region of the comet.
    [Show full text]