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RADIAL VELOCITIES in the ZODIACAL DUST CLOUD
A SURVEY OF RADIAL VELOCITIES in the ZODIACAL DUST CLOUD Brian Harold May Astrophysics Group Department of Physics Imperial College London Thesis submitted for the Degree of Doctor of Philosophy to Imperial College of Science, Technology and Medicine London · 2007 · 2 Abstract This thesis documents the building of a pressure-scanned Fabry-Perot Spectrometer, equipped with a photomultiplier and pulse-counting electronics, and its deployment at the Observatorio del Teide at Izaña in Tenerife, at an altitude of 7,700 feet (2567 m), for the purpose of recording high-resolution spectra of the Zodiacal Light. The aim was to achieve the first systematic mapping of the MgI absorption line in the Night Sky, as a function of position in heliocentric coordinates, covering especially the plane of the ecliptic, for a wide variety of elongations from the Sun. More than 250 scans of both morning and evening Zodiacal Light were obtained, in two observing periods – September-October 1971, and April 1972. The scans, as expected, showed profiles modified by components variously Doppler-shifted with respect to the unshifted shape seen in daylight. Unexpectedly, MgI emission was also discovered. These observations covered for the first time a span of elongations from 25º East, through 180º (the Gegenschein), to 27º West, and recorded average shifts of up to six tenths of an angstrom, corresponding to a maximum radial velocity relative to the Earth of about 40 km/s. The set of spectra obtained is in this thesis compared with predictions made from a number of different models of a dust cloud, assuming various distributions of dust density as a function of position and particle size, and differing assumptions about their speed and direction. -
Atmospheric Effects Are Looking Up
Atmospheric Effects are Looking Up OASI Workshop 21st May 2018 by Olaf Kirchner Ever seen one of these ? OK, so how about one of these? Atmospheric Effects - caused by sun- or moonlight interacting with liquid water or ice in the air - surprisingly common - always beautiful and one or several phenomena may be seen at the same time - can be in-your-face obvious or very subtle, and ... - ... span the entire sky - a challenge to photograph - very complicated theoretical explanations Effects caused by Liquid Water Droplets - rainbows - glories, Heiligenschein and the Spectre of the Brocken - aureoles / coronae - nacreous / iridescent / Mother-of-Pearl clouds Rainbow Rainbow Ray paths for primary rainbow Ray paths through a spherical water drop Ray paths for secondary rainbow Secondary Rainbow Secondary rainbow Alexander’s Band Supernumerary rainbow Primary rainbow Rainbow Gap in cloud behind observer = partial rainbow Rainbow in spray, Geneva Jet d’Eau Supernumerary Rainbow Interference colours from different lengths of light path Rainbow Circular rainbow seen from an aircraft Rainbows don’t reflect ... Glory Colourful diffraction rings centred on the antisolar point, caused by reflection from spherical droplets Glory ... i.e. centred on where the shadow of your head would be! Brockengespenst = Spectre of the Brocken Taken against fog from Golden Gate Bridge Brocken (1142 m) . Highest point in the Harz mountains Heiligenschein = Halo Antisolar point in hydrothermal steam ... scary stuff Heiligenschein ... i.e. a glory centred on your head -
Atmospheric Phenomena by Feist
Atmospheric optical phenomena An introductory guide by Mike Feist Effects caused by water droplets— rainbows and coronae The most well known optical sky effect is the rainbow. This, as most people know, sometimes occurs when the Sun is out and it is raining. To see a rainbow you must stand with your back to the Sun with the raindrops in front of you. It does not have to be raining where you are standing but in the direction that you are looking. The arc of the primary (main) bow is centred on the antisolar point, the spot directly oppo- site the Sun, and has a radius of 42°. The antisolar point is actually centred on the shadow of your head. If the Sun is rising or setting and therefore on the horizon, the primary rainbow will be a complete semi- circle and the top will be 42° up in the sky. If, on the other hand, the Sun is 42° up in the sky, the primary bow will be on the horizon, the top just rising or setting. Con- ventionally the rainbow is said to have John Constable. Hampstead Heath with a Rainbow (1836). seven colours but all we need to remember seen in the spray near waterfalls and artifi- ous forms but with a six-sided shape. They is that, in the primary bow, the red is on cial rainbows can be made using a garden may be as flat hexagonal plates or long the outside and the blue on the inside. Out- hose. Rainbows are one of the easiest opti- hexagonal prisms or as a combination of side the primary bow sometimes there is cal effects to photograph although they the two. -
Atmospheric Optics
53 Atmospheric Optics Craig F. Bohren Pennsylvania State University, Department of Meteorology, University Park, Pennsylvania, USA Phone: (814) 466-6264; Fax: (814) 865-3663; e-mail: [email protected] Abstract Colors of the sky and colored displays in the sky are mostly a consequence of selective scattering by molecules or particles, absorption usually being irrelevant. Molecular scattering selective by wavelength – incident sunlight of some wavelengths being scattered more than others – but the same in any direction at all wavelengths gives rise to the blue of the sky and the red of sunsets and sunrises. Scattering by particles selective by direction – different in different directions at a given wavelength – gives rise to rainbows, coronas, iridescent clouds, the glory, sun dogs, halos, and other ice-crystal displays. The size distribution of these particles and their shapes determine what is observed, water droplets and ice crystals, for example, resulting in distinct displays. To understand the variation and color and brightness of the sky as well as the brightness of clouds requires coming to grips with multiple scattering: scatterers in an ensemble are illuminated by incident sunlight and by the scattered light from each other. The optical properties of an ensemble are not necessarily those of its individual members. Mirages are a consequence of the spatial variation of coherent scattering (refraction) by air molecules, whereas the green flash owes its existence to both coherent scattering by molecules and incoherent scattering -
Insider Tips
It’s no secret that North Lake Tahoe has some of the most gorgeous sunsets on the west coast, but did you know that winter is actually the best time to watch the sunset? The shoreline of North Lake Tahoe is the perfect place to watch the sky light up, so follow along and get your cameras ready! What Is It? Fun Facts Year-round, North Lake Tahoe is home to the most awe- • Alpenglow happens when light is reflected off airborne inspiring sunsets featuring breathtaking cotton candy colored precipitation and ice crystals in the lower atmosphere skies. In winter, the signature snowy scenery and glittering and technically is only visible after sunset or before waters add even more beauty to the region’s sunsets for a sunrise. The term “alpenglow” dates back to 19th can’t-miss viewing experience. century Germany to describe this unique phenomenon. Where Can I Find It? If You Like This, You’ll Love: North Lake Tahoe’s beaches are some of the best places to Other great spots for winter lakeside sunsets in North Lake catch stunning sunsets in the winter, from Commons Beach Tahoe include: in Tahoe City to The Hyatt Regency Lake Tahoe’s beach in • Hidden Beach in Incline Village Incline Village and everywhere in between. • Donner Summit in Truckee Because sunsets happen earlier during winter months, these beaches also offer the perfect jumping off point to enjoy • Moon Dunes Beach in Tahoe Vista dinner during or after a sunset. Try these different restaurants • Speedboat Beach in Crystal Bay for the perfect post-sunset meal: In Tahoe City and Commons Beach Insider Tips • Christy Hill, Sunnyside Restaurant & Lodge, Jake’s On • Because the sun goes down earlier in the winter, visitors The Lake, or Wolfdale’s Cuisine Unique can enjoy the sunset before, or during, dinner without In Kings Beach and Carnelian Bay having to stay up late. -
The Quest for the Gegenschein Erwin Matys, Karoline Mrazek
The Quest for the Gegenschein Erwin Matys, Karoline Mrazek The sun’s counterglow — or gegenschein — is kind of a stargazers’ legend. Every amateur astronomer has heard about it, only a few of them have actually seen it, and even fewer were lucky enough to capture an image of this dim and ghostlike apparition. As a fellow observer put it: “The gegenschein is certainly not a GOTO-object.” Matter of fact, it isn’t an object at all. But let’s start from the beginning. What exactly is the gegenschein? It is widely known that the space between the planets isn’t empty. The plane of the solar system is filled with an enormous disk of small dust particles with sizes ranging from less than 1/1000 mm up to 1 mm. It is less commonly known that this interplanetary dust cloud is a highly dynamic structure. In contrast to conventional wisdom, it is not an aeon-old leftover from the solar system’s formation. This primordial dust is long gone. Today’s interplanetary dust is — in an astronomical sense of speaking — very young, only millions of years old. Most of the particles originate from quite recent incidents, like asteroid collisions. This is not the gegenschein. The picture shows the zodiacal light, which is closely related to the gegenschein. Here imaged from a rural site, the zodiacal light is a cone of light extending from the sun along the ecliptic, visible after dusk and before dawn. The gegenschein stems from the same dust cloud, but is much harder to detect or photograph. -
Atmospheric Refraction
International Young Naturalists’ Tournament 4. Sunset Serbian team Regional Center For Talented Youth 4. Sunset The visible Sun disk touches the horizon and after a particular time interval disappears behind the horizon. What is the duration of this time interval? Explain the optical phenomena observed during a sunset. SUNSET Sunset (sundown) - daily disappearance of the Sun below the western horizon, as a result of Earth's rotation In astronomy : the time of sunset - moment when the trailing edge of the Sun's disk disappears below the horizon ANGULAR VELOCITY OF THE SUN • angularthe angle speed by which for one an complete object spins rotation in a certain is given time as: - its rotation rate t = 23h 54 min 4s ANGULAR VELOCITY - orthogonal component- ω ϕ DURATION OF SUNSET •equation for the duration of sunset: DURATION OF SUNSET • The fastest sunset at the time of the equinoxes (March 21 and September 23 • The slowest sunset at the time of solstice (around 21 June and 21 December) DURATION OF SUNSET • The fastest sunset - 2 minutes 47 sec • The slowest sunset - 3 min 23 sec • At the equator, between 128 and 142 sec (2 min. 8 sec and 2 min. 22 sec) DURATION OF SUNSET City Duration of sunset Latitude Beijing 167 s 39.92° Belgrade 183.6 s 44.82° Paris 198 s 48.86° London 209.3 s 51.51° Moscow 231.5 s 55.75 ° Light scattering Reflection Refraction LIGHT SCATTERING • caused by small particles and molecules in the atmosphere • scattered rays go off in many directions RAYLEIGH SCATTERING • Rayleigh scattering - elastic scattering of light • Blue light from the sun is scattered more than red LAW OF REFLECTION DIFFUSE REFLECTION • It occurs when a rough surface causes reflected rays to travel in different directions ATMOSPHERIC REFRACTION • the shift in apparent direction of a celestial object caused by the refraction of light rays as they pass through Earth’s atmosphere MORE OPTICAL PHENOMENA Twilight Wedge Belt of Venus Earth’s shadow Afterglow Alpenglow CONCLUSION During the sunset: 1. -
Wfc3 Isr 2014
SPACE TELESCOPE SCIENCE INSTITUTE Operated for NASA by AURA Instrument Science Report WFC3 2014-11 The Near Infrared Sky Background N. Pirzkal May 13, 2014 ABSTRACT WFC3 IR observations are often background limited. In the vast majority of cases, when HST is pointed away from the Earth Limb, the main contribution to this background light is caused by zodiacal infrared light, including the Gegenschein, the diffuse glow in the sky centered upon Earth's antisolar point. In this ISR, we present direct measurements of the infrared background levels as observed by WFC3 since its launch and in several broad band filters. We compare our observations to the values currently used in the Exposure Time Calculator (ETC) and derive a model of the IR background levels as a function of Ecliptic Latitude and Sun Angle. Data and Analysis WFC3 IR images have been continuously monitored since the installation of WFC3 on board of HST, as part of the \Blob" Monitoring Program (Pirzkal et al. 2012) and the making of deep sky-flats (Pirzkal et al. 2011). The data that were used and details of the procedures used are given in Pirzkal et al. 2011 and Pirzkal et al. 2012. As part of this routine monitoring, we naturally needed to accurately measure the background level in each of the available infrared exposures. The was done by first generating an object mask using SExtractor for each individual FLT file. This mask was then used to mask out sources in each of the IMSET of the original IMA file and we then computed the background in each IMSET Copyright c 2008 The Association of Universities for Research in Astronomy, Inc. -
When the Earth Was Young in This Issue
WESTCHESTER AMATEUR ASTRONOMERS August 2014 Illustration Credit: Simone Marchi (SwRI), SSERVI, NASA When the Earth Was Young Four billion years ago, our Solar System was a dangerous shooting gallery of large and dangerous rocks and ice chunks. Recent examination of lunar and Earth bombardment data in- In This Issue . dicate that the entire surface of the Earth underwent piecemeal upheavals, creating a battered world with no remaining famil- pg. 2 Events For August iar landmasses. The rain of devastation made it difficult for pg. 3 Almanac any life to survive. Oceans thought to have formed during this pg. 4 Into the Belly of the Beast: The epoch would boil away after particularly heavy impacts, only to reform again. The above artist's illustration depicts how ATLAS Detector Earth might have looked during this epoch, with circular im- pg. 10 The Invisible Shield of our Sun pact features dotting the daylight side, and hot lava flows visi- ble in the night. Credit: APOD SERVING THE ASTRONOMY COMMUNITY SINCE 1986 1 WESTCHESTER AMATEUR ASTRONOMERS August 2014 Events for August 2014 Kopernik AstroFest 2014 WAA Lectures This event will be held at the Kopernik Observatory Lienhard Lecture Hall, & Science Education Center – Vestal, NY on Octo- th th Pace University Pleasantville, NY ber 24 and 25 , 2014. Presented by the The Ko- As usual, there will be no WAA lecture for the month pernik Astronomical Society, the Astrofest will fea- of August. Our Lecture series will resume on Septem- ture astronomy workshops, solar viewing, observa- ber 12th. During the Fall we have tentatively scheduled tory tours and speakers from the amateur and pro- presentations by Victor Miller on the Galileo Jupiter fessional communities as well as observing at night. -
Atmospheric Optical Phenomena and Radiative Transfer
ATMOSPHERIC OPTICAL PHENOMENA AND RADIATIVE TRANSFER BY STANLEY DAVID GEDZELMAN AND MICHAEL VOLLMER Sky colors, rainbows, and halos are simulated using models that include light scattered as it passes through clear air and clouds of finite optical depth. ivid rainbows, ice crystal halos, coronas, iridescence, glories, mirages, sky colors, and crepuscular rays have Valways inspired awe and wonder. This makes simulating atmospheric optical phenomena both a scientific and aesthetic undertaking. Atmospheric optics has a venerable history (Pernter and Exner 1922; Minnaert 1993; Humphreys 1940; Tricker 1970; Greenler 1980; Meinel and Meinel 1983; Lynch and Livingston 2001), because the phenomena appear so simple and striking, and because scientists emphasized this branch of atmospheric science at a time when it was far more difficult to examine large-scale weather systems. Discoveries made about or involving the rainbow by Rene Descartes, Isaac Newton, and Thomas Young rank among the early triumphs of the scientific revolution (Boyer 1987). All optical phenomena are produced when air molecules, aerosol particles, or hydrometeors either scatter or absorb light as it passes through the atmosphere. Many of the observed features of the optical phenomena can be reproduced by applying a scattering theory of light to a single particle. This can be done at various levels of complexity. The most accurate and perhaps most intricate Rainbow. " University Corporation for Atmospheric theories involve • i Research, Photo by Carlye Calvin BAH5- AMERICAN METEOROLOGICAL SOCIETY Unauthenticated | DownloadedAPRIL 2008 10/09/21 01:28 AM UTC solving Maxwell's equations with appropriate bound- flattening of drops (Fraser 1983), while models of ary conditions. -
Than Mountain Air and Daytime Scenery
Moonbows overYosem te By Donald W. Olson, Russell L. Doescher, and the Mitte Honors Students The rainbow occurs by day, and it was formerly thought that it never appeared by night as a moon rainbow. This opinion was due to the rarity of the phenomenon: it was not observed, for though it does happen, it does so rarely. The colors are not easy to see in the dark. The moon rainbow appears white. — Aristotle, Meteorologica, about 340 BC More than mountain Few sights evoke such spontaneous delight and wonder as a late- afternoon rainbow bursting into view in the eastern sky after a air and daytime spring downpour. Even before it appears, you sense that it might, and you keep a lookout. Maybe you once fancied fi nding a pot of scenery beckon gold where the colorful arc ends. Yet how many of us have seen a rainbow at night? While this is a visitors to Yosemite fairly rare event, nature lovers as far back as Aristotle knew it was National Park each possible for a bright Moon, like the Sun, to produce a rainbow. When rays of light from the Sun (or Moon) shine on spherical spring — many go for drops of water in a rain shower, a combination of refraction, inter- nal refl ection, and dispersion can produce a rainbow display. The a chilly, damp, night- primary bow forms a circular arc with a radius of 42°, and under good conditions a much fainter secondary rainbow can appear time vigil. with a radius of 51° and with the sequence of colors reversed. -
Alpenglow- Denali National Park and Preserve Newsletter
Denali National Park and Preserve, Alaska National Park Service U.S. Department of the Interior Official newspaper Autumn 2016 to Spring 2017 Alpenglow PHOTO COURTESY MENNO BOERMANS The "Edge of the World" near the 14,200-foot camp on Denali's popular West Buttress route has a dramatic 5,000-foot drop to the Northeast Fork of the Kahiltna Glacier. Superintendent Greeting Denali Celebrates its Next Century The year 2016 was special as the Park staff and community groups are Several special events are being planned National Park Service marked its working together to host events to for that Sunday to commemorate the 100th birthday. Special events were held commemorate the 100th anniversary of the specific date of the park's 100th birthday. in Denali and other parks across the park's establishment on Feb. 26, 1917. Among the honored guests in attendance country to mark the milestone. is expected to be Charlie Sheldon, a At a Solstice Luminary Stroll, you can descendant of Charles Sheldon, who was The year 2017 will be just as exciting as ski, snowshoe, or stroll down a trail lit by among the leading advocates lobbying Denali celebrates its own centennial in luminaria (candles) on a snowy winter's Congress to create the park in 1917. More February. night. This family-friendly at http://go.nps.gov/Winterfest event begins in the early evening of The park offers year-round activities Wed Dec 21 at the Winter Visitor Center As a highlight of its Centennial for people of all ages. I encourage (Murie Science and Learning Center) at å outreach this winter, the park will visitors, neighbors and partners to take Mile 1.4 of the Denali Park Road.