ASTRONOMY ENCYCLOPEDIA ASTRONOMY ENCYCLOPEDIA FOREWORD BY LEIF J ROBINSON Editor Emeritus, Sky & Telescope magazine STAR MAPS CREATED BY WIL TIRION GENERAL EDITOR SIR PATRICK MOORE HOW TO USE THE ENCYCLOPEDIA PHILIP’S ASTRONOMY ENCYCLOPEDIA First published in Great Britain in 1987 by Mitchell Beazley under the title The Astronomy Encyclopedia (General Editor Patrick Moore) This fully revised and expanded edition first published in 2002 by Philip’s, an imprint of Octopus Publishing Group 2–4 Heron Quays London E14 4JP Copyright © 2002 Philip’s ISBN 0–540–07863–8 All rights reserved Apart from any fair dealing for the purpose of private study, research, criticism or review, as permitted under the Copyright Designs and Patents Act, 1988, no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, electrical, chemical, mechanical, optical, photocopying, recording, or otherwise, without prior written permission All enquiries should be addressed to the Publisher A catalogue record for this book is available from the British Library Printed in Spain Details of other Philip’s titles and services can be found on our website at www.philips-maps.co.uk Managing Editor Caroline Rayner Technical Project Editor John Woodruff Commissioning Editor Frances Adlington Consultant Editor Neil Bone Executive Art Editor Mike Brown Designer Alison Todd Picture Researcher Cathy Lowne Production Controller Sally Banner THE GREEK ALPHABET α β γ δ ε ζ Α Β Γ ∆ Ε Ζ alpha beta gamma delta epsilon zeta η θ ι κ λ µ Η eta Θ theta Ι iota Κ kappa Λ lambda Μ mu ν ξ ο π ρ σ Ν Ξ Ο Π Ρ Σ nu xi omicron pi rho sigma τ υ φ χ ψ ω Τ tau Υ upsilon Φ phi Χ chi Ψ psi Ω omega MULTIPLES AND SUBMULTIPLES USED WITH SI UNITS Multiple 103 106 109 1012 1015 1018 Prefix kilomegagigaterapetaexa- Symbol k M G T P E Submultiple 103 106 109 1012 1015 1018 Prefix millimicronanopicofemtoatto- Symbol m m n p f a Alphabetical order ‘Mc’ is treated as if it were spelled ‘Mac’, and certain shortened forms as if spelled out in full (e.g ‘St’ is treated as ‘Saint’) Entries that have more than one word in the heading are alphabetized as if there were no space between the words Entries that share the same main heading are in the order of people, places and things Entries beginning with numerals are treated as if the numerals were spelled out (e.g 3C follows three-body problem and precedes 3C 273) An exception is made for HI region and HII region, which appear together immediately after Hirayama family Biographies are alphabetized by surname, with first names following the comma (Forenames are placed in parentheses if the one by which a person is commonly known is not the first.) Certain lunar and planetary features appear under the main element of names (e.g Imbrium, Mare rather than Mare Imbrium) Cross-references in an article indicate a separate entry that defines and explains the word or subject capitalized ‘See also’ at the end of an article directs the reader to entries that contain additional relevant information SMALL CAPITALS Measurements Measurements are given in metric (usually SI) units, with an imperial conversion (to an appropriate accuracy) following in parentheses where appropriate In historical contexts this convention is reversed so that, for example, the diameter of an early telescope is given first in inches Densities, given in grams per cubic centimetre, are not converted, and neither are kilograms or tonnes Large astronomical distances are usually given in light-years, but parsecs are sometimes used in a cosmological context Particularly in tables, large numbers may be given in exponential form Thus 103 is a thousand, ϫ 106 is two million, and so on ‘Billion’ always means a thousand million, or 109 As is customary in astronomy, dates are expressed in the order year, month, day Details of units of measurement, conversion factors and the principal abbreviations used in the book will be found in the tables on this page Stellar data In almost all cases, data for stars are taken from the HIPPARCOS CATALOGUE The very few exceptions are for instances where the catalogue contains an error of which the editors have been aware In tables of constellations and elsewhere, the combined magnitude is given for double stars, and the average magnitude for variable stars Star Maps pages 447–55 Acknowledgements page 456 FRONTMATTER IMAGES Endpapers: Andromeda Galaxy The largest member of the Local Group, this galaxy is the farthest object that can be seen with the naked eye Half-title: Crab Nebula This nebula is a remnant of a supernova that exploded in the constellation of Taurus in 1054 Opposite title: M83 Blue young stars and red HII emission nebulae clearly mark out regions of star formation in this face-on spiral galaxy in Hydra Opposite Foreword: NGC 4945 This classic disk galaxy is at a distance of 13 million l.y Its stars are mainly confined to a flat, thin, circular region surrounding the nucleus Opposite page 1: Earth This photograph was obtained by the Apollo 17 crew en route to the Moon in 1972 December SYMBOLS FOR UNITS, CONSTANTS AND QUANTITIES a Å AU c d e E eV f F g G G h h Ho Hz i IC Jy k K semimajor axis angstrom unit astronomical unit speed of light distance eccentricity energy electron-volt following focal length, force acceleration due to gravity gauss gravitational constant hour Planck constant Hubble constant hertz inclination Index Catalogue jansky Boltzmann constant degrees kelvin L Ln luminosity Lagrangian points (n = to 5) l.y light-year m metre, minute m apparent magnitude, mass mbol bolometric magnitude mpg photographic magnitude mpv photovisual magnitude mv visual magnitude M absolute magnitude, mass (stellar) N newton p preceding P orbital period pc parsec q perihelion distance qo deceleration parameter Q aphelion distance r radius, distance R Roche limit s second t T Teff v W y z α δ λ µ ν π ω Ω ° Ј Љ time temperature (absolute), epoch (time of perihelion passage) effective temperature velocity watt year redshift constant of aberration, right ascension declination wavelength proper motion frequency parallax longitude of perihelion observed/critical density ratio, longitude of ascending node degree arcminute arcsecond CONVERSION FACTORS Distances nm = 10 Å inch = 25.4 mm mm = 0.03937 inch 1ft = 0.3048 m m = 39.37 inches = 3.2808 ft mile = 1.6093 km km = 0.6214 mile km/s = 2237 mile/h pc = 3.0857 × 1013 km = 3.2616 l.y = 206,265 AU l.y = 9.4607 × 1012 km = 0.3066 pc = 63,240 AU Temperatures (to the nearest degree) °C to °F : ϫ1.8, ϩ32 °C to K : ϩ273 °F to °C : Ϫ32, Ϭ1.8 °F to K : Ϭ1.8, ϩ255 K to °C : Ϫ273 K to °F : ϫ1.8, Ϫ460 Note: To convert temperature differences, rather than points on the temperature scale, ignore the additive or subtractive figure and just multiply or divide CONTRIBUTORS hilip’s would like to thank the following contributors for their valuable assistance in updating and supplying new material for this edition: P Alexander T Basilevsky, Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russia Richard Baum, UK Peter R Bond, FRAS, FBIS, Space Science Advisor for the Royal Astronomical Society, UK Neil Bone, Director of the BAA Meteor Section and University of Sussex, UK Dr Allan Chapman, Wadham College, University of Oxford, UK Storm Dunlop, FRAS, FRMetS, UK Tim Furniss, UK Peter B J Gill, FRAS, UK Dr Ian S Glass, South African Astronomical Observatory, South Africa Dr Monica M Grady, The Natural History Museum, London, UK Dr Andrew J Hollis, BAA, UK James B Kaler, Department of Astronomy, University of Illinois, USA William C Keel, Department of Physics and Astronomy, University of Alabama, USA Professor Chris Kitchin, FRAS, University of Hertfordshire, UK Professor Kenneth R Lang, Tufts University, USA Dr Richard McKim, Director of the BAA Mars Section, UK Mathew A Marulla, USA Steve Massey, ASA, Australia Sir Patrick Moore, CBE, FRAS, UK Dr Franỗois Ochsenbein, Astronomer at Observatoire Astronomique de Strasbourg, France Dr Christopher J Owen, PPARC Advanced Fellow, Mullard Space Science Laboratory, University College London, UK Chas Parker, BA, UK Neil M Parker, FRAS, Managing Director, Greenwich Observatory Ltd, UK Martin Ratcliffe, FRAS, President of the International Planetarium Society (2001–2002), USA Ian Ridpath, FRAS, Editor Norton’s Star Atlas, UK Leif J Robinson, Editor Emeritus Sky & Telescope magazine, USA Dr David A Rothery, Department of Earth Sciences, The Open University, UK Robin Scagell, FRAS, Vice President of the Society for Popular Astronomy, UK Jean Schneider, Observatoire de Paris, France Dr Keith Shortridge, Anglo-Australian Observatory, Australia Dr Andrew T Sinclair, former Royal Greenwich Observatory, UK Pam Spence, MSc, FRAS, UK Dr Duncan Steel, Joule Physics Laboratory, University of Salford, UK Nik Szymanek, University of Hertfordshire, UK Richard L S Taylor, British Interplanetary Society, UK Wil Tirion, The Netherlands Dr Helen J Walker, CCLRC Rutherford Appleton Laboratory, UK Professor Fred Watson, Astronomer-in-Charge, Anglo-Australian Observatory, Australia Dr James R Webb, Florida International University and the SARA Observatory, USA Dr Stuart Weidenschilling, Senior Scientist, Planetary Science Institute, USA Professor Peter Wlasuk, Florida International University, USA John Woodruff, FRAS, UK Contributors to the 1987 edition also include: Dr D J Adams, University of Leicester, UK Dr David A Allen, Anglo-Australian Observatory, Australia Dr A D Andrews, Armagh Observatory, N Ireland R W Arbour, Pennell Observatory, UK R W Argyle, Royal Greenwich Observatory (Canary Islands) H J P Arnold, Space Frontiers Ltd, UK Professor W I Axford, Max-Planck-Institut für Aeronomie, Germany Professor V Barocas, Past President of the BAA, UK Dr F M Bateson, Astronomical Research Ltd, New Zealand Dr Reta Beebe, New Mexico State University, USA Dr S J Bell Burnell, Royal Observatory, Edinburgh, UK D P Bian, Beijing Planetarium, China Dr D L Block, University of Witwatersrand, South Africa G L Blow, Carter Observatory, New Zealand Professor A Boksenberg, Royal Greenwich Observatory (Sussex, UK) Dr E Bowell, Lowell Observatory, USA Dr E Budding, Carter Observatory, New Zealand Dr P J Cattermole, Sheffield University, UK Von Del Chamberlain, Past President of the International Planetarium Society Dr David H Clark, Science & Engineering Research Council, UK Dr M Cohen, University of California, USA P G E Corvan, Armagh Observatory, N Ireland Dr Dale P Cruikshank, University of Hawaii, USA Professor J L Culhane, Mullard Space Science Laboratory, UK Dr J K Davies, University of Birmingham, UK M E Davies, The Rand Corporation, California, USA Professor R Davis, Jr, University of Pennsylvania, USA D W Dewhirst, Institute of Astronomy, Cambridge, UK Professor Audouin Dollfus, Observatoire de Paris, France Commander L M Dougherty, UK Dr J P Emerson, Queen Mary College, London, UK Professor M W Feast, South African Astronomical Observatory, South Africa Dr G Fielder, University of Lancaster, USA Norman Fisher, UK K W Gatland, UK A C Gilmore, Mt John Observatory, University of Canterbury, New Zealand Professor Owen Gingerich, Harvard-Smithsonian Center for Astrophysics, USA Dr Mart de Groot, Armagh Observatory, N Ireland Professor R H Garstang, University of Colorado, USA L Helander, Sweden Michael J Hendrie, Director of the Comet Section of the BAA, UK Dr A A Hoag, Lowell Observatory, USA Dr M A Hoskin, Churchill College, Cambridge, UK Commander H D Howse, UK Professor Sir F Hoyle, UK Dr D W Hughes, University of Sheffield, UK Dr G E Hunt, UK Dr R Hutchison, British Museum (Natural History), London, UK Dr R J Jameson, University of Leicester, UK R M Jenkins, Space Communications Division, Bristol, UK Dr P van de Kamp, Universiteit van Amsterdam, The Netherlands Professor W J Kaufmann, III, San Diego State University, USA Dr M R Kidger, Universidad de La Laguna, Tenerife, Canary Islands Dr A R King, University of Leicester, UK Dr Y Kozai, Tokyo Astronomical Observatory, University of Tokyo, Japan R J Livesey, Director of the Aurora Section of the BAA, UK Sir Bernard Lovell, Nuffield Radio Astronomy Laboratories, Jodrell Bank, UK Professor Dr S McKenna-Lawlor, St Patrick’s College, Co Kildare, Ireland Dr Ron Maddison, University of Keele, UK David Malin, Anglo-Australian Observatory, Australia J C D Marsh, Hatfield Polytechnic Observatory, UK Dr J Mason, UK Professor A J Meadows, University of Leicester, UK Howard Miles, Director of the Artificial Satellite Section of the BAA, UK L V Morrison, Royal Greenwich Observatory (Sussex, UK) T J C A Moseley, N Ireland Dr P G Murdin, Royal Greenwich Observatory (Sussex, UK) C A Murray, Royal Greenwich Observatory (Sussex, UK) I K Nicolson, MSc, Hatfield Polytechnic, UK J E Oberg, USA Dr Wayne Orchiston, Victoria College, Australia Dr M V Penston, Royal Greenwich Observatory (Sussex, UK) J L Perdrix, Australia Dr J D H Pilkington, Royal Greenwich Observatory (Sussex, UK) Dr D J Raine, University of Leicester, UK Dr R Reinhard, European Space Agency, The Netherlands H B Ridley, UK C A Ronan, East Asian History of Science Trust, Cambridge, UK Professor S K Runcorn, University of Newcastle upon Tyne, UK Dr S Saito, Kwasan & Hida Observatories, University of Kyoto, Japan Dr R W Smith, The Johns Hopkins University, USA Dr F R Stephenson, University of Durham, UK E H Strach, UK Professor Clyde W Tombaugh, New Mexico State University, USA R F Turner, UK Dr J V Wall, Royal Greenwich Observatory (Sussex, UK) E N Walker, Royal Greenwich Observatory (Sussex, UK) Professor B Warner, University of Cape Town, South Africa Professor P A Wayman, Dunsink Observatory, Dublin, Ireland Dr G Welin, Uppsala University, Sweden A E Wells, UK E A Whitaker, University of Arizona, USA Dr A P Willmore, University of Birmingham, UK Dr Lionel Wilson, University of Lancaster, UK Professor A W Wolfendale, University of Durham, UK Dr Sidney C Wolff, Kitt Peak National Observatory, USA K Wood, Queen Mary College, London, UK Les Woolliscroft, University of Sheffield, UK Dr A E Wright, Australian National Radio Astronomy Observatory, Australia FOREWORD he progress of astronomy – or, more precisely, astrophysics – over the past century, and particularly the past generation, is not easily pigeon-holed On the one hand, profound truths have tumbled abundantly from the sky Here are four diverse examples: Our universe began some 14 billion years ago in a single cataclysmic event called the Big Bang Galaxies reside mainly in huge weblike ensembles Our neighbouring planets and their satellites come in a bewildering variety Earth itself is threatened (at least within politicians’ horizons) by impacts from mean-spirited asteroids or comets On the other hand, ordinary citizens may well feel that astronomers are a confused lot and that they are farther away than ever from understanding how the universe is put together and how it works For example, ‘yesterday’ we were told the universe is expanding as a consequence of the Big Bang; ‘today’ we are told it is accelerating due to some mysterious and possibly unrelated force It doesn’t help that the media dine exclusively on ‘gee-whiz’ results, many of them contradictory and too often reported without historical context I can’t help but savour the pre-1960s era, before quasars and pulsars were discovered, when we naïvely envisioned a simple, orderly universe understandable in everyday terms Of course, all the new revelations cry out for insightful interpretation And that’s why I’m delighted to introduce this brand-new edition So much has been discovered since it first appeared in 1987 so much more needs to be explained! It’s sobering to catalogue some of the objects and phenomena that were unknown, or at least weren’t much on astronomers’ minds, only a generation or two ago The one that strikes me most is that 90% (maybe 99%!) of all the matter in the universe is invisible and therefore unknown We’re sure it exists and is pervasive throughout intergalactic space (which was once thought to be a vacuum) because we can detect its gravitational influence on the stuff we can see, such as galaxies But no one has a cogent clue as to what this so-called dark matter might be Masers, first created in laboratories in 1953, were found in space only 12 years later These intense emitters of coherent microwave radiation have enabled astronomers to vastly improve distance determinations to giant molecular clouds and, especially, to the centre of our Galaxy A scientific ‘war’ was fought in the 1960s as to whether clusters of galaxies themselves clustered Now even the biggest of these socalled superclusters are known to be but bricks in gigantic walls stretching across hundreds of millions of light-years These walls contain most of the universe’s visible matter and are separated from each other by empty regions called voids The discovery of quasars in 1963 moved highly condensed matter on to astronomy’s centre stage To explain their enormous and rapidly varying energy output, a tiny source was needed, and only a black hole having a feeding frenzy could fill the bill Thus too was born the whole subdiscipline of relativistic astrophysics, which continues to thrive Quasars are now regarded as having the highest energies in a diverse class called active galaxies Gamma-ray bursts, the most powerful outpourings of energy known in the universe, only came under intense scrutiny by astronomers in the 1990s (they had been detected by secret military satellites since the 1960s) The mechanism that leads to this prodigious output is still speculative, though a young, very massive star collapsing to form a black hole seems favoured A decades-long quest for extrasolar planets and closely related brown-dwarf (failed) stars came to an abrupt end in 1995 when the first secure examples of both entities were found (By a somewhat arbitrary convention, planets are regarded as having masses up to several times that of Jupiter; brown dwarfs range from about 10 to 80 Jupiters.) Improved search strategies and techniques are now discovering so many of both objects that ordinary new ones hardly make news T One of the greatest successes of astrophysics in the last century was the identification of how chemical elements are born Hydrogen, helium, and traces of others originated in the Big Bang; heavier elements through iron derive from the cores of stars; and still heavier elements are blasted into space by the explosions of very massive stars The discovery of pulsars in 1967 confirmed that neutron stars exist Born in supernova explosions, these bodies are only about 10 kilometres across and spin around as rapidly as 100 times a second Whenever a pulsar’s radiation beam, ‘focused’ by some of the strongest magnetic fields known, sweeps over the Earth, we see the pulse In addition to being almost perfect clocks, pulsars have allowed studies as diverse as the interstellar medium and relativistic effects Finally, unlike any other astronomical object, pulsars have yielded three Nobel Prizes! Tantalizing though inconclusive evidence for extraterrestrial life accumulates impressively: possible fossil evidence in the famous Martian meteorite ALH 84001, the prospect of clement oceans under the icy crust of Jupiter’s satellite Europa, and the organiccompound rich atmosphere of Saturn’s moon Titan And then there is the burgeoning catalogue of planets around other stars and the detection of terrestrial life forms in ever more hostile environments All this suggests that we may not be alone On a higher plane, despite many efforts to find extraterrestrial intelligence since Frank Drake’s famous Ozma experiment in 1960, we haven’t picked up E.T.’s phone call yet But the search has barely begun The flowering of astrophysics stems from the development of ever larger, ever more capable telescopes on the ground and in space All the electromagnetic spectrum – from the highest-energy gamma rays to the lowest-energy radio waves – is now available for robust scrutiny, not just visible light and long-wavelength radio emission as was the case in as recently as the 1950s Equally impressive has been the development of detectors to capture celestial radiation more efficiently In the case of the CCD (charge-coupled device), trickle-down technology has allowed small amateur telescopes to act as though they were four or five times larger Augmented by effective software, CCDs have caused a revolution among hobbyists, who, after nearly a century-long hiatus, can once again contribute to mainstream astrophysical research Increasingly, astronomers are no longer limited to gathering electromagnetic radiation Beginning late in the last century, they started to routinely sample neutrinos, elementary particles that allow us to peek at such inaccessible things as the earliest times in the life of the universe and the innards of exploding stars And the gravitational-wave detectors being commissioned at the time of this writing should allow glimpses of the fabric of spacetime itself Astronomy has involved extensive international collaborations for well over a century The cross-disciplinary nature of contemporary research makes such collaborations even more compelling in the future Furthermore, efforts to build the next generation of instruments on the ground and especially in space are so expensive that their funding will demand international participation Where astronomers go from here? ‘Towards the unknown’ may seem like a cliché, but it isn’t With so much of the universe invisible or unsampled, there simply have to be many enormous surprises awaiting! When it comes to the Big Questions, I don’t know whether we are children unable to frame our thoughts, or teenagers at sea, or adults awash in obfuscating information Researchers find the plethora of new discoveries – despite myriad loose ends and conundrums – to be very exciting, for it attests to the vibrancy and maturation of the science Yet, as we enter the 21st century, astronomers are still a very long way from answering the two most common and profound questions people ask: what kind of universe we live in, and is life pervasive? Leif J Robinson Editor Emeritus, Sky & Telescope magazine absolute temperature AAT Abbreviation of ANGLO-AUSTRALIAN TELESCOPE AAVSO Abbreviation of AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS Abbot, Charles Greeley (1872–1961) American astronomer who specialized in solar radiation and its effects on the Earth’s climate He was director of the Smithsonian Astrophysical Observatory from 1907 Abbot made a very accurate determination of the solar constant, compiled the first accurate map of the Sun’s infrared spectrum and studied the heating effect of the solar corona He helped to design Mount Wilson Solar Observatory’s 63-ft (19-m) vertical solar telescope Abell, George Ogden (1927–83) American astronomer who studied galaxies and clusters of galaxies He is best known for his catalogue of 2712 ‘rich’ clusters of galaxies (1958), drawn largely from his work on the PALOMAR OBSERVATORY SKY SURVEY The Abell clusters, some of which are billion l.y distant, are important because they define the Universe’s large-scale structure Abell successfully calculated the size and mass of many of these clusters, finding that at least 90% of the mass necessary to keep them from flying apart must be invisible aberration (1) (aberration of starlight) Apparent displacement of the observed position of a star from its true position in the sky, caused by a combination of the Earth’s motion through space and the finite velocity of the light arriving from the star The effect was discovered by James BRADLEY in 1728 while he was attempting to measure the PARALLAX of nearby stars His observations revealed that the apparent position of all objects shifted back and forth annually by up to 20Љ in a way that was not connected to the expected parallax effect The Earth’s movement in space comprises two parts: its orbital motion around the Sun at an average speed of 29.8 km/s (18.5 mi/s), which causes annual aberration, and its daily rotation, which is responsible for the smaller of the two components, diurnal aberration The former causes a star’s apparent position to describe an ELLIPSE over the course of a year For any star on the ECLIPTIC, this ellipse is flattened into a straight line, whereas a star at the pole of the ecliptic describes a circle The angular displacement of the star, ␣, is calculated from the formula tan ␣ = v/c, where v is the Earth’s orbital velocity and c is the speed of light Diurnal aberration is dependent on the observer’s position on the surface of the Earth Its effect is maximized at the equator, where it produces a displacement of a stellar position of 0Љ.32 to the east, but drops to zero for an observer at the poles Bradley’s observations demonstrated both the motion of the Earth in space and the finite speed of light; they have influenced arguments in cosmology to the present day aberration (2) Defect in an image produced by a LENS or MIRROR Six primary forms of aberration affect the quality of image produced by an optical system One of these, CHROMATIC ABERRATION, is due to the different amount of refraction experienced by different wavelengths of light when passing through the boundary between two transparent materials; the other five are independent of colour and arise from the limitations of the geometry of the optical surfaces They are sometimes referred to as Seidel aberrations after Ludwig von Seidel (1821–96), the mathematician who investigated them in detail The five Seidel aberrations are SPHERICAL ABERRATION, COMA, ASTIGMATISM, curvature and distortion All but spherical aberration are caused when light passes through the optics at an angle to the optical axis Optical designers strive to reduce or eliminate aberrations and combine lenses of different glass types, thickness and shape to produce a ‘corrected lens’ Examples are the composite OBJECTIVES in astronomical refractors and composite EYEPIECES Curvature produces images that are not flat When projected on to a flat surface, such as a photographic film, the image may be in focus in the centre or at the edges, but not at both at the same time Astronomers using CCD cameras on telescopes can use a field flattener to produce a well-focused image across the whole field of view Often this is combined with a focal reducer to provide a wider field of view Distortion occurs where the shape of the resulting image is changed Common types of distortion are pincushion and barrel distortion, which describe the effects seen when an image of a rectangle is formed Some binocular manufacturers deliberately introduce a small amount of pin-cushion distortion as they claim it produces a more natural experience when the binoculars are panned across a scene Measuring the distortion in a telescope is extremely important for ASTROMETRY as it affects the precise position measurements being undertaken Astrometric telescopes once calibrated are maintained in as stable a condition as possible to avoid changing the distortion A Abetti, Giorgio (1882–1982) Italian solar physicist, director of ARCETRI ASTROPHYSICAL OBSERVATORY (1921–52) As a young postgraduate he worked at Mount Wilson Observatory, where pioneering solar astronomer George Ellery HALE became his mentor Abetti designed and constructed the Arcetri solar tower, at the time the best solar telescope in Europe, and used it to investigate the structure of the chromosphere and the motion of sunspot penumbras (the Evershed–Abetti effect) ablation Process by which the surface layers of an object entering the atmosphere (for example a spacecraft or a METEOROID) are removed through the rapid intense heating caused by frictional contact with the air The heat shields of space vehicles have outer layers that ablate, preventing overheating of the spacecraft’s interior absolute magnitude (M) Visual magnitude that a star would have at a standard distance of 10 PARSECS If m = apparent magnitude and r = distance in parsecs: M = m ϩ Ϫ log r For a minor planet this term is used to describe the brightness it would have at a distance of AU from the Sun, AU from the Earth and at zero PHASE ANGLE (the Sun–Asteroid–Earth angle, which is a physical impossibility) absolute temperature Temperature measured using the absolute temperature scale; the units (obsolete) are ºA This scale is effectively the same as the modern thermodynamic temperature scale, wherein temperature angle of aberration distance light travels AAO Abbreviation of ANGLO-AUSTRALIAN OBSERVATORY ᭣ aberration Aberration can cause displacement in the position of a star relative to its true position as viewed in a telescope Bending of the light path away from the optical axis produces coma, drawing the star image into a ‘tail’ (3) Offset of the star’s position (2) can reduce the effectiveness of the telescope for astrometry A X-ray burster ᭤ X-ray binary The strong X-ray source Cygnus X-3 is a close binary system in which matter from a normal star is being drawn into a neutron star or black hole This Chandra X-ray Observatory image shows a halo of emission resulting from scattering by interstellar dust in the line of sight, allowing the distance to Cygnus X-3 to be estimated at 30,000 l.y of the neutron star and is burnt to helium (see NUCLEAR When the amount of helium on the surface of the neutron star exceeds a critical amount, the helium suddenly ignites, causing a burst of X-rays The temperature can rise to 30 million K at the peak of the burst and 10 seconds later fall back to 15 million K Almost 30 X-ray bursters have been found in GLOBULAR CLUSTERS; for example, the first was found in NGC 6624 (Omega Centauri has five, M22 has four) They are generally found close to the centre of the cluster, where the star density is very high These X-ray bursters are also thought to be binary stars, with a neutron star accreting material from a low-mass companion star REACTIONS) X-ray galaxy Galaxy that emits powerfully in the X-ray part of the ELECTROMAGNETIC SPECTRUM, indicating that it probably has a large or supermassive black hole at its centre, with an ACCRETION DISK These galaxies include active galaxies (such as NGC 4151 and Centaurus A), SEYFERT GALAXIES, QUASARS and BL LACERTAE OBJECTS, many of which are also radio sources X-ray galaxies often appear to be merging or colliding systems ᭢ X-ray galaxy A strong source of radio waves, Centaurus A (NGC 5128) is seen optically to have a dark lane crossing its centre, believed to result from a merger between two galaxies – a giant elliptical and a spiral – several hundred million years ago X-ray observations reveal further activity, in the form of a jet extending from the nucleus towards top left in this image X consist of a normal star and a compact object such as a WHITE DWARF, NEUTRON STAR or BLACK HOLE The UHURU satellite originally showed that some X-ray stars underwent eclipses, revealing that they were close binary systems (for example HERCULES X-1) There are several types of X-ray binary system, with properties that depend upon the nature of the compact object There are massive (high-mass) X-ray binaries and low-mass X-ray binaries (low-mass implies stars around the mass of the Sun) Low-mass X-ray binaries containing a neutron star tend to be X-RAY BURSTERS, for example SCORPIUS X-1 and Hercules X-1 Low mass X-ray binaries with a white dwarf as the compact object are CATACLYSMIC VARIABLES When the companion star shedding the material is a massive star (for CYGNUS X-1 the mass is more than 30 solar masses), the star can often be detected optically The strong stellar wind transfers material directly on to the compact object X-ray pulsars are usually found in binary systems with high-mass companions SS433 is an unusual massive X-ray binary, with a possible black hole as the compact object; it shows relativistic JETS X-ray burster Source with intense flashes, or bursts, of X-rays The bursts have rise times of around second and can last as little as 10 seconds, yet the energy released is equivalent to a week’s output from the Sun (or more) A few X-ray bursts have been detected at optical wavelengths X-ray bursters are BINARY STAR systems in which one star is a NEUTRON STAR The neutron star is surrounded by a hydrogen-rich ACCRETION DISK from a low-mass companion star (around one solar mass) The hydrogen flows from the accretion disk on to the surface X-ray nova BINARY STAR system that occasionally becomes bright at X-ray wavelengths One member of the binary is a WHITE DWARF and the other is a low-mass giant (usually around one solar mass) Material from the giant star falls on to the white dwarf, and eventually there is so much material on the surface that it ignites (see NUCLEAR REACTIONS) causing the X-ray emission, which will fade away over weeks or months It is assumed that this will recur, but the timescale may be decades or centuries DWARF NOVAE have ACCRETION DISKS, so the material falls on to the white dwarf from the disk rather than from the companion star Although the outburst is less dramatic (hence the adjective ‘dwarf’), the outburst can occur frequently, even as often as every week or two X-ray star Star that is a powerful source of X-rays The detection of X-rays from a star usually means the star is a CLOSE BINARY system, with one member being a compact object, either a WHITE DWARF, NEUTRON STAR or BLACK HOLE (see X-RAY BINARY) However, even the Sun emits Xrays, from its CORONA, as other stars Massive hot O stars (such as CYGNUS X-3) emit X-rays because of their high temperatures and high mass-loss in their stellar winds X-ray telescope Instrument for imaging X-ray sources All X-ray telescopes are satellite-borne because X-rays not penetrate the Earth’s atmosphere Unlike less energetic electromagnetic radiation, X-rays cannot be focused by reflection from a conventional concave mirror (as in a reflecting telescope) because, for all but the shallowest angles of incidence, they penetrate the surface In grazing incidence X-ray telescopes the focusing element is a pair of coaxial surfaces, one PARABOLOIDAL and the other HYPERBOLOIDAL, from which incoming X-rays are reflected at a very low ‘grazing’ angle towards a focus The detecting element is often a CCD adapted for X-ray wavelengths An alternative instrument is the microchannel plate detector, in which the incident radiation falls on a plate made up of many fine tubes, rather like a short, wide fibreoptic bundle The plate is charged, so that the radiation generates electrons which are accelerated down the tubes and together form an image that can be read off X-ray telescopes have been flown on missions such as YOHKOH, the CHANDRA X-RAY OBSERVATORY and NEWTON X-ray transient X-ray outburst from a BINARY STAR system; it is similar to an X-RAY NOVA outburst but lasts for a longer period The X-ray source will brighten suddenly and fade away after a few weeks (or occasionally months) More than 30 objects have been found to show X-ray transients Some NEUTRON STARS have hot companion stars and some have cool (K or M), low-mass companions The transient indicates that mass transfer is erratic for some (unknown) reason See also X-RAY BURSTER 442 Young, Charles Augustus Yagi antenna Basic form of ANTENNA, used in RADIO TELESCOPES and for work on the IONOSPHERE It consists of several parallel elements mounted on a straight member; it is the familiar form of a television aerial A Yagi antenna often forms the basis of cheap arrays used for APERTURE SYNTHESIS It was developed by the Japanese engineer Hietsugu Yagi (1886–1976) year Time taken for the Earth to complete a single revolution around the Sun Several different types of year are defined, with differing lengths, according to which point of reference is chosen An ANOMALISTIC YEAR is one revolution relative to PERIHELION; it is equivalent to 365.25964 mean solar days An ECLIPSE YEAR is one revolution relative to the same node of the Moon’s orbit; it is equivalent to 346.62003 mean solar days Nineteen eclipse years are 6585.78 days, almost exactly the same as a SAROS A SIDEREAL YEAR is one revolution relative to the fixed stars; it equivalent to 365.25636 mean solar days A TROPICAL YEAR or solar year is one revolution relative to the EQUINOXES; it equivalent to 365.24219 mean solar days For convenience, the civil or CALENDAR year is set at a whole number of days, usually 365 but 366 in a LEAP YEAR Yerkes Observatory Observatory of the University of Chicago, located at an elevation of 334 m (1050 ft) at Williams Bay, Wisconsin, near Chicago It is famous for its 1.02-m (40-in.) refracting telescope, built in 1897 with optics figured by ALVAN CLARK & SONS and a mounting constructed by the WARNER & SWASEY COMPANY, and still the largest refractor in the world The observatory owes its foundation to George Ellery HALE, who persuaded the streetcar magnate Charles Tyson Yerkes (1837–1905) to finance the great telescope The observatory also has 1.02-m (40-in.) and 0.6-m (24-in) reflectors and a number of smaller instruments Gerard KUIPER used the 40-inch to discover MIRANDA in 1948 and NEREID the year after Today, though LIGHT POLLUTION limits observational astronomy from the William Bay site, Yerkes is still a major research institution and its astronomers use such facilities as the Astrophysics Research Consortium’s 3.5-m (138-in.) telescope at Apache Point, New Mexico, the HUBBLE SPACE TELESCOPE and the telescopes of the W.M KECK OBSERVATORY The observations of spectral lines provide information about the temperature and density of the hot plasma in the Sun’s atmosphere, and about motions of the plasma along the line of sight The SXT images X-rays in the range 0.25–4.0 keV and can resolve features down to 2Љ.5 in size Flare images can be obtained every seconds Smaller images with a single filter can be obtained as frequently as once every 0.5 seconds The HXT observes hard X-rays in four energy bands and can resolve structures with angular sizes of about 5Љ These images can also be obtained once every 0.5 seconds Yohkoh played an important role in improving understanding of processes in the solar atmosphere Of particular interest were the origin of solar flares, the link between such flares and coronal mass ejections, studies of coronal holes and the evolution of magnetic loops The Yohkoh spacecraft is in a slightly elliptical low Earth orbit, with an altitude ranging from approximately 570 to 730 km (355 to 455 mi); 65 to 75 minutes of each 90-minute orbit are spent in sunlight Young, Charles Augustus (1834–1908) American solar astronomer at Dartmouth (1866–77) and Princeton (1877–1905) who made early spectroscopic studies of the solar corona, proving its gaseous nature He obtained the first FLASH SPECTRA of the solar chromosphere during a total eclipse in 1870 and compiled a catalogue of bright solar spectral lines to measure the Sun’s rotational velocity Young obtained the first successful photographs of solar prominences in visible light Y ᭢ Yohkoh This Yohkoh image of the active Sun at X-ray wavelengths shows hot coronal plasma in magnetic loops above active regions Cooler, dark regions above the poles are described as coronal holes; these extend to lower solar latitudes at sunspot minimum ‘Y-feature’ Characteristic atmospheric feature of VENUS Although this planet is virtually featureless in visible light, ultraviolet photographs reveal a banded structure that resolves into a characteristic shape, a horizontal letter Y This feature rotates around the planet in a period of only four to five days, implying wind speeds of 100 m/s (330 ft/s) in the upper atmosphere The solid surface rotates at only about m/s (13 ft/s) Yohkoh (Sunbeam) Solar X-ray satellite, a collaboration between the Japanese Institute of Space and Astronautical Science (ISAS), NASA and the UK Launched from the Kagoshima Space Centre in 1991 August, the spacecraft has observed the solar atmosphere continuously for more than an entire cycle of solar activity Yohkoh’s main scientific objective is to observe the energetic phenomena taking place on the Sun, especially X-ray and gamma-ray emissions from solar FLARES It carries four instruments that detect these energetic emissions – two spectrometers, a soft X-ray telescope (SXT) and a hard X-ray telescope (HXT) Y 443 z z Symbol for REDSHIFT Zelenchukskaya Astrophysical Observatory See SPECIAL ASTROPHYSICAL OBSERVATORY Z Zach, Franz Xaver von (1754–1832) Hungarian astronomer known for his part in the discovery of Ceres In 1786 he began building the Seeberg Observatory near Gotha, Germany; three years later he began searching for the hypothetical planet between Mars and Jupiter predicted by BODE’S LAW Concluding that a more organized search by the world’s most skilled observers would be necessary to find the ‘missing’ planet, in 1800 he convened a meeting at the private observatory of Johann SCHRÖTER, one of the CELESTIAL POLICE On 1801 January 1, Giuseppe PIAZZI discovered CERES, orbiting between Mars and Jupiter The asteroid was subsequently lost, but Zach recovered it using orbital calculations by Carl Friedrich GAUSS ZAMS Abbreviation of ZERO-AGE MAIN SEQUENCE Z Andromedae star (ZAND) Type of CATACLYSMIC VARIABLE, included in the larger SYMBIOTIC STAR grouping Z Andromedae star systems resemble DWARF NOVAE, but instead of a main-sequence secondary, they contain a red giant or supergiant together with a hot white dwarf The components are close together, and MASS TRANSFER appears to occur either in the form of a stream of material or as an enhanced stellar wind, depending on the system The material is accreted by the white dwarf, either directly or through an ACCRETION DISK, giving rise to occasional outbursts Z Andromedae itself has a magnitude range of 8.3 to 12.4 zap crater Most commonly, a very small crater created by micrometeorite impact It is a usually lined with glasses and surrounded by fractures Zarya Russian Functional Energy module for the INTERNATIONAL SPACE STATION (ISS) It was the first ISS component to be launched, in 1988 Z Camelopardalis star (UGZ) ERUPTIVE VARIABLE star, a subtype of DWARF NOVA Z Camelopardalis stars differ from the common dwarf nova class (see U GEMINORUM STAR) in that they experience occasional ‘standstills’, remaining more or less constant in brightness for a long period These standstills always seem to begin during a decline from maximum When the standstill ends, the star drops to minimum brightness, and then resumes its ‘normal’ behaviour Both the occurrence of the standstills and their duration, ranging from a few days to many months, are quite unpredictable Z Camelopardalis itself is the brightest member of the class It may reach magnitude 10.2 at brightest and falls to about 14.5 at minimum The usual interval between outbursts is roughly 22 days Zeeman effect Splitting of a spectral line into several components by the presence of a magnetic field Where the components are unresolved, a broadened line is seen The effect allows the measurement of the strengths of magnetic fields on the Sun, the stars and even in the interstellar medium Zel’dovich, Yakov Borisovich (1914–87) Russian astrophysicist and cosmologist, born in Minsk, modern Belorussia, who originated the ‘pancake model’ of LARGE-SCALE STRUCTURE in the Universe With Rashid Alievich Sunyaev (1943– ) he described the Sunyaev–Zel’dovich effect, an apparent reduction in the temperature of the cosmic background radiation as it passes through hot ionized gas between members of galaxy clusters In the early 1970s, Zel’dovich and others developed a model of the early Universe in which huge discrete lumps of primordial matter collapsed asymmetrically under their own weight as they cooled, forming thin ‘pancakes’ The model correctly predicts the arrangement of galaxies in sheets and voids revealed by REDSHIFT SURVEYS Z 444 Zenit Heavyweight former Soviet Union satellite launcher, first flown in 1985, which can place payloads weighing 13 tonnes into low Earth orbit The two-stage Zenit, built in the Ukraine, had 28 successful and failed launches to 2001 It mainly carried Soviet electronic intelligence and Earth observation satellites The booster also provides the basis of the SEA LAUNCH commercial satellite launcher zenith Point on the CELESTIAL SPHERE directly overhead an observer and 90º from the horizon This is known as the astronomical zenith Because the Earth is not a sphere, the geocentric zenith is defined as a line joining the centre of the Earth to the observer The point 180º away from the zenith, directly beneath an observer, is the NADIR zenith distance Angular distance from the ZENITH to a celestial body, measured along a GREAT CIRCLE It is usually expressed as a topocentric measure, from the observer’s position on the Earth’s surface, but sometimes geocentric, as measured by a hypothetical observer at the centre of the Earth The zenith distance is equal to 90º minus the altitude of the body above the horizon zenithal hourly rate (ZHR) Useful index of METEOR activity, allowing comparison of observations made at different times and under different sky conditions Zenithal hourly rate is determined by allowing for the altitude (a) of the shower RADIANT during observations, the stellar limiting magnitude (LM), and the POPULATION INDEX (r, indicative of the proportions of faint meteors that might be lost to background skyglow in the shower under study) The derived ZHR corresponds to the expected number of meteors seen in a perfectly transparent sky (LM = ϩ6.5) with the radiant overhead; it is calculated by multiplying the observed hourly count by 1/sin a ϫ r6.5ϪLM SHOWER zero-age main sequence (ZAMS) MAIN SEQUENCE as defined by stars of zero age, which is the point when they have achieved a stable state, with core temperatures sufficiently high for nuclear fusion to begin As the star evolves and changes hydrogen into helium, its chemical composition changes and it shifts to the right of its zeroage position on the HERTZSPRUNG–RUSSELL DIAGRAM zero gravity Apparent absence of GRAVITATIONAL FORCES within a free-falling system A body in a ‘zero gravity’ or free-fall state experiences no sensation of weight, hence the ‘weightlessness’ of astronauts, since the spacecraft is continuously free falling towards the Earth while its transverse motion ensures that it gets no closer The term ‘zero gravity’ does not imply a total absence of gravity, rather it refers to an absence of any detectable gravitational forces Although gravity becomes very weak at large distances from massive bodies, it nowhere declines absolutely to zero See also ACCELERATION OF FREE FALL Zeta Aurigae ECLIPSING BINARY with a period of 972 days; the visual range is from magnitude 3.7 to 4.2 It is the faintest of the three ‘Kids’ near Capella The Zeta Aurigae system consists of a hot B-type star and a supergiant companion of type K; the distance is about 790 l.y During the partial phase of the eclipse of the hot star, its light shines through the outer, rarefied layers of the supergiant, and there are complicated and informative spectroscopic effects The eclipse of the B-type star is total for 38 days; this is preceded and followed by partial stages lasting for 32 days each Zhang Heng (AD 78–139) Chinese scientist, the first in China to build a rotating celestial globe and an armillary sphere with horizon and meridian rings With these and other simple instruments, he observed and catalogued 320 Zöllner photometer bright stars, and estimated the total number of naked-eye stars as 11,520 He concluded that ‘the sky is large and the Earth small’ – a radical concept at the time Zhang understood that the Earth and Moon are spherical, lunar eclipses are caused by the Earth’s shadow falling upon the Moon, and the Moon shines by reflected sunlight ZHR Abbreviation for ZENITHAL HOURLY RATE Zijin Shan Observatory See PURPLE MOUNTAIN OBSERVATORY zodiac Belt of CONSTELLATIONS, roughly 8º on either side of the ECLIPTIC, through which the Sun, Moon and planets (except Pluto) appear to pass The zodiac includes the 12 familiar constellations – Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius and Pisces, which are of varying sizes In ASTROLOGY, however, the zodiac is divided into 12 equal signs, each 30º long, but because of the effects of PRECESSION and re-definitions of constellation boundaries they no longer coincide with the constellations of the same name Precession has also caused the ecliptic to now pass through the constellation Ophiuchus, while the zodiac now also includes parts of Cetus, Orion and Sextans zodiacal band Very faint band of light that extends along the ECLIPTIC and joins the ZODIACAL LIGHT to the GEGENSCHEIN Its brightness is variable and it can only be observed under conditions of extreme clarity when no Moon is present Like the zodiacal light, it is caused by the scattering of sunlight towards the Earth by a cloud of dust particles surrounding the Sun (see INTERPLANETARY DUST) The band is faintest at around 135º from the Sun and brightens towards the cone of the zodiacal light and towards the gegenschein zodiacal catalogue Catalogue of stars in a narrow zone straddling the ECLIPTIC (the zodiac), through which most of the planets and asteroids move OCCULTATIONS of stars in this region by the Moon, planets or smaller members of the Solar System permit highly accurate position measurements of the occulting body, and may also reveal the binary nature of an occulted star, or even allow an estimation of its radius Zodiacal catalogues therefore give highly accurate positions of stars James Robertson’s Catalogue of 3539 Zodiacal Stars brighter than 9th magnitude was published in 1940; the largest zodiacal catalogue (USNO-SA2.0) lists about 50 million stars zodiacal dust See INTERPLANETARY DUST zodiacal light Faint, diffuse conical skyglow seen extending along the ecliptic soon after twilight ends at sunset, or before dawn begins to brighten the sky ahead of sunrise The zodiacal light is comparable in brightness to the Milky Way, and it is best seen from temperate latitudes in the spring evening sky about 90 minutes after sunset, or in the autumn morning sky about 90 minutes before sunrise At these times, the ecliptic is steeply inclined relative to the western or eastern horizon respectively From lower latitudes – between the tropics and the equator – viewing conditions for the zodiacal light are favourable throughout the year Transparent skies and the absence of moonlight (even a crescent moon can swamp it) are essential for successful observation of the zodiacal light Broadest at its base, the zodiacal light extends some 60–90º along the ecliptic from the Sun, and it is produced by the scattering of sunlight from myriad small (1–300 ␮m diameter) particles lying in the plane of the planets’ orbits This material, originating from emissions by comets close to perihelion and collisions in the asteroid belt, forms a vast zodiacal dust complex, which permeates the inner Solar System out to the orbit of Jupiter, AU from the Sun Spacecraft measurements show that the dust is very much less abundant beyond Jupiter The zodiacal light is joined around the ecliptic to the GEGENSCHEIN by narrow faint extensions known as the zodiacal bands Variations in the intensity of the zodiacal light are thought to occur, with maximum brightness being found at sunspot minimum when interplanetary space is pervaded by fast-flowing particle streams from coronal holes The zodiacal dust complex contains a mass of material estimated to be equivalent to that of a typical comet nucleus; without continual replenishment from active comets, the complex and its associated zodiacal light would probably disappear within about 10,000 years Zöllner, (Johann Karl) Friedrich (1834–82) German inventor of astronomical instruments and pioneer astrophysicist In the late 1850s and early 1860s, he perfected the astronomical PHOTOMETER, with which the relative brightnesses of stars are measured accurately by comparing them with an artificial star produced by a petroleum lamp The Potsdam Observatory used this instrument to compile the first photometric star catalogue, the Photometrische Durchmusterung des nördlichen Himmels He also invented the ‘reversion spectroscope’ – based on the same principles as the HELIOMETER – which Hermann Carl VOGEL used to calculate the Sun’s rotation period In theoretical astrophysics, Zöllner introduced the idea that a star’s temperature determines its spectral characteristics, and that these attributes are both related to the star’s evolutionary stage Zöllner photometer Visual PHOTOMETER that uses a fixed and a rotating polarizing element to vary the apparent brightness of an artificial star until it is the same as a real star seen in the same field of view The amount of rotation of the polarizer can be calibrated to give the APPARENT MAGNITUDE of the real star ᭣ zodiacal light Produced by scattering of sunlight from interplanetary dust, the zodiacal light appears as a conical glow extending along the ecliptic in the late-evening or pre-dawn sky In this photograph, the planet Venus is visible at lower right 445 Z Zond Zond Eight unmanned Soviet spacecraft launched in 1964–70 Zond 1, and returned no data Zond photographed the farside of the Moon in 1965 Zond 5, 6, and went around the Moon and returned to Earth as part of preparations for a crewed circumlunar mission zone of avoidance Region of the sky near the plane of the Milky Way, where dust absorption and the high concentration of stars make it difficult to locate other galaxies optically It typically spans 10º on either side of the galactic plane Some kinds of galaxies in the zone of avoidance can now be detected by their radio, infrared or X-ray emissions, which are less vulnerable to dust and gas absorption Surveys of such galaxies are important for tracing LARGE-SCALE STRUCTURE, since some important nearby SUPERCLUSTERS and the GREAT ATTRACTOR either cross the zone of avoidance or lie mostly within it Zürich number See RELATIVE SUNSPOT NUMBER Zvezda Russian Service Module for the INTERNATIONAL SPACE STATION (ISS) Zwicky, Fritz (1898–1974) Swiss physicist and astrophysicist, born in Bulgaria, known chiefly for his observational and theoretical work on supernovae and his cataloguing of clusters of galaxies He left Switzerland for the United States in 1925, joining the CALIFORNIA INSTITUTE OF TECHNOLOGY in 1927, where he was appointed professor of astrophysics in 1942 Although Zwicky lived in America for nearly fifty years, he retained his Swiss citizenship In 1934 he and Walter BAADE coined the term ‘supernova’ They had noted that ordinary novae in the Z 446 Andromeda Galaxy (M31) reached a maximum average apparent magnitude of 17 However, the ‘nova’ observed in 1885 in that galaxy, designated S Andromedae, had reached 7th magnitude, and now that the great distance to M31 was appreciated, it was clear that this was a phenomenon of a different order from ordinary novae Zwicky and Baade suggested that a supernova is a cataclysmic stellar explosion that leaves behind a neutron star, and that the CRAB NEBULA was a supernova remnant (the latter confirmed in 1968 with the discovery of the CRAB PULSAR) From 1936, using the newly developed Schmidt camera, Zwicky discovered and examined many supernovae in other galaxies In 1933 Zwicky inferred the presence of dark matter by observing that outlying members of the COMA CLUSTER were moving more rapidly than could be explained by the calculated mass of the cluster, and four years later he suggested that dark matter could be investigated via gravitational lensing by intervening galaxies His extensive studies of galaxies culminated in the six-volume Catalogue of Galaxies and Clusters of Galaxies (1961–68), listing 30,000 galaxies and 10,000 clusters, compiled with colleagues and completed just before his death ZZ Ceti star (ZZ) White dwarf VARIABLE STAR, with low amplitude (0.001–0.2 mag.) The variations arise from non-radial pulsations, and generally multiple periods are present simultaneously in each star Periods range from about 30 seconds to 25 minutes There are three recognized subtypes based upon the presence of hydrogen, helium, or helium and carbon absorption lines in the spectra Approximately 50 examples are currently known STAR MAPS CREATED BY WIL TIRION Maps & 2: Northern Stars to dec +30º Map 3: Equatorial Stars, RA 18 to 0h, dec +60º to –60º Map 4: Equatorial Stars, RA 12 to 18h, dec +60º to –60º Map 5: Equatorial Stars, RA to 12h, dec +60º to –60º Map 6: Equatorial Stars, RA to 6h, dec +60º to –60º Maps & 8: Southern Stars to dec –30º This complex of hot stars and nebulosity is designated Chamaeleon I It lies in the constellation of the same name 6h +30º STAR MAP 1: NORTHERN STARS TO DEC ϩ30° 5h χ T φ ι US R TAU AURIGA σ 4h ζ µ ω λ ο ξ 3h ε IES π AR ο ν ω β µ 48 Algol π 16 κ δ λ ξ α Mirphak β δ σ ψ ι +60º 2h TRIANGULUM γ δ β θ Almaak η χ β 1h σ ω ξ Mirach Double Cluster 51 φ 869 φ µ π ξ ANDROMEDA σ ρ ν ζ R λ θ α υ η 0h ρ R γ 58 50 CASSIOPEIA κ β Polaris α +90º γ τ ψ κ ω ψ Schedir Caph σ ι ι δ 1,2 γ ε φ θ µ π ο M31 Andromeda Galaxy CAMELOPARDALIS χ ν δ α 884 +80º υ +70º τ τ PISCES γ τ γ M33 +50º ρ R ε β Capella 17 Menkalinan α ε PERSEUS θ ν ρ η ζ 58 υ τ +40º hese star maps were specially created for this edition by Wil Tirion Between them they cover the whole of the sky, with some overlap Maps and 2, on these pages, represent the northern stars down to declination +30° Maps to cover a broad strip of the sky extending 60° either side of the celestial equator, suitably oriented for northern hemisphere observers (Southern-hemisphere observers should simply turn the book through 180°.) Maps and show the southern stars, to declination –30° All 88 constellations are shown on these maps (An index showing on which map(s) each constellation appears will be found alongside maps and 8.) The ο λ π ρ ι CEPHEUS ξ δ ο α 23h 11 ζ ε β ν µ τ ε α Alderamin ρ LACERTA η +80º η π χ σ θ υ φ +70º δ π2 41,40 VV λ PEGASUS κ β π W π ρ DRACO 33 ο 60 h 22 ξ 7000 North America Nebula σ τ 61 υ ζ α ν ω ω1 Deneb ο1 ψ ο2 κ ι θ δ γ Sadr λ +60º +50º T P ε R h 21 CYGNUS 52 LYRA 39 η 41 η θ χ 20 h KEY TO STAR MAGNITUDES ι φ ε12 ε +40º ζ α δ Vega κ γ λ 0.0 and brighter 0.1 – 0.5 0.6 – 1.0 1.1 – 1.5 1.6 – 2.0 2.1 – 2.5 2.6 – 3.0 3.1 – 3.5 3.6 – 4.0 4.1 – 4.5 4.6 – 5.0 5.1 – 5.5 19 h β M57 Ring Nebula HER +30º 18h 448 6h STAR MAP 2: NORTHERN STARS TO DEC ϩ30° +30º 7h RT τ ρ GEMINI α AURIGA θ Castor π ο UU constellation names are in capital letters, while star names are lower case with an initial capital A few other features, for example prominent asterisms such as the Square of Pegasus, are also named The Milky Way is shown in a lighter blue than the main background The ecliptic (the Sun’s path against the background stars) is shown as a dashed red line The Moon and the planets will always be found near the ecliptic Stars to magnitude 5.5 are shown (in half-magnitude steps), together with major deep-sky objects A key to star magnitudes and a key to map symbols accompany each chart The brightest stars are shown in their true colours 8h θ +40º ψ3 ψ7 ψ2 Menkalinan ψ4 π CANCER ψ5 9h β σ2 ψ1 σ3 RS LYNX ψ6 +50º 21 α 31 38 δ LEO 10 UMa 15 ι 12 h 10 10 κ +60º 21 15 LEO MINOR θ ο β 26 λ φ τ CAMELOPARDALIS ρ σ1 σ2 46 υ 23 11h +70º π2 µ URSA MAJOR ω 47 M81 ψ β +80º M82 ξ Merak α Dubhe ν M97 Owl Nebula The Plough γ λ Polaris δ δ T ε β Alioth Y Kochab 41,40 β ζ Mizar η α 80 Thuban γ α Alcor M51 Whirlpool Galaxy RR ψ Cor Caroli COMA B ERENIC ES URSA MINOR ζ θ +70º Megrez κ ε +80º 12h North Pole 13 h +90º χ Phecda α η CANES VENATICI Alkaid ω ζ κ ι θ ι λ η DRACO AT θ +60º 44 γ Etamin µ β β υ τ +50º ι σ φ χ 30 λ HERCULES τ η +40º M13 ρ ζ ν σ µ µ δ ζ κ CORONA BOREALIS η θ σ ξ h 16 Double stars ε +30º ν1 ν2 π 68 ρ BOÖTES ν ν φ θ γ 17,16 15 h ν 14 h ξ Variable stars Open clusters Globular clusters Planetary nebulae Diffuse nebulae Galaxies KEY TO MAP SYMBOLS 17h 18h 449 STAR MAP 3: EQUATORIAL STARS, RA 18 TO 0h, DEC ϩ60° TO Ϫ60° 0h +60º 23h β Caph 22h τ δ ρ 0.0 and brighter 21h λ 20h µ ζ CEPHEUS ε λ 18h ο 33 σ 0.1 – 0.5 19h DRACO CASSIOPEIA κ β 0.6 – 1.0 R 1.1 – 1.5 +50º ψ π1 α π ω 1.6 – 2.0 λ ψ κ 2.1 – 2.5 ρ W 2.6 – 3.0 ξ R θ ρ ANDROMEDA σ 3.6 – 4.0 σ τ δ Deneb R North America Nebula LYRA ν +40º 3.1 – 3.5 ο2 ο1 7000 ο ω1 α 11 ι 63 LACERTA γ Sadr λ T π +30º 5.1 – 5.5 η α Scheat Alpheratz KEY TO STAR MAGNITUDES ψ +20º µ τ υ χ µ ο β ζ CYGNUS 52 41 Algenib α α γ δ Markab ξ 70 σ ρ 55 ω γ TX λ 0º ε θ β η ζ φ χ ψ 3,2 ψ ι –10º ω2 λ E CL –20º ρ IC ξ β θ AQUARIUS δ γ ι –30º λ π α ν ι ρ θ κ δ1 µ2 λ τ σ π ε ο ζ κ –60º 0h π υ ρ1 χ2 52 ω χ1 SAGITTARIUS ι η ε γ ε α λ δ2 ι δ1 α ζ TELESCOPIUM η κ µ θ η1 CORONA AUSTRALIS ξ κ ρ ε θ ARA λ η µ ν INDUS α Peacock β 22h Kaus Australis ζ β2 θ δ W γ δ β1 ν Alnair δ η α α M8 Lagoon Nebula λ ζ ι ζ M20 Trifid Nebula φ τ θ2 θ1 M24 µ ν2,1 M22 σ Nunki ψ M17 Y M25 ξ1 ο ξ2 59 ι M16 Eagle Nebula Omega Nebula σ η TUCANA 23h ρ α β GRUS τ SCUTUM β MICROSCOPIUM ξ µ ε γ R α α1 α θ1 ζ M11 M55 β PHOENIX η ζ δ ν γ λ 67 70 68 π ι ε –50º υ SERPENS (Cauda) θ AQUILA ψ ε ι γ φ Ankaa θ PISCIS AUSTRINUS β –40º δ ι ω τ µ β δγ SCULPTOR θ υ η Fomalhaut γ ν 24 ε µ σ CAPRICORNUS ζ α η Altair ν η φ 72 OPHIUCHUS R µ ε θ 36 δ κ2 κ ζ ι ε 86 γ κ µ τ υ 88 ε λ µ κ 99 β θ ν ι 98 T 111 FF IPT δ 71 ο τ CETUS τ 102 ω1 α ξ 95 109 ζ χ η E Q U AT O R γ α SAGITTA β δ ο α EQUULEUS σ ω1 φ α κ 30 ζ ρ κ DELPHINUS β ν π κ ι δ γ Enif θ ι PISCES ζ 113 110 S ζ η ε β HERCULES VULPECULA η γ PEGASUS +10º 450 Dumbbell Nebula M27 Square of Pegasus ο α 13 φ γ β Albireo κ TV κ Ring Nebula λ Vega β γ λ M57 χ φ 51 α ζ δ ι 23 ι ε2 η ε 39 4.6 – 5.0 ε1 η θ P 61 υ 4.1 – 4.5 ι θ 21h PAVO 20h 19h 18h STAR MAP 4: EQUATORIAL STARS, RA 12 TO 18h, DEC ϩ60° TO Ϫ60° 17h 16h 15h 14h 13h 12h AT DRACO ι θ ξ URSA MAJOR Megrez δ Alioth ν ζ Alcor µ 80 ε Mizar Double stars The Plough γ 17,16 β Eltanin +60º T θ γ Variable stars Phecda κ ι +50º η Alkaid 44 τ ι υ Open clusters χ M51 Whirlpool Galaxy λ Y φ σ ρ χ 30 η π θ τ ν1 ζ ε ξ ν 68 ν ι µ βο χ ψ α δ γ Alphekka ω 67 ο τ1 β π χ λ µ υ π π 110 109 SERPENS ξ (Cauda) η ξ SGR X ECLIPTI C θ ω ω 2,1 ρ 36 τ Galactic Centre 45 ν ζ µ2 θ ζ λ ι ε µ θ ξ β y ο ι ψ β ν1 τ1 κ τ2 α π υ CENTAURUS υ1 B D ι ζ Omega Centauri ω 5139 ρ LUPUS –40º n µ φ ο λ µ ν χ η κ ε η c1 Menkent δ d θ σ ξ1 τ γ e ξ2 C3 C2 σ –50º δ ζ ε1 ρ ε NORMA κ β γ ζ V PAVO η 17h µ CIRCINUS ι1 ARA 18h c2 γ2 γ π α d γ ω α ε2 β CRATER ε –30º φ1 φ2 δ λ ψ γ ζ HYDRA π η µ1 µ σ ζ 54 58 υ η η γ CORVUS ψ1 ψ2 θ Shaula ι2 ι1 δ –20º υ τ ξ χ SCORPIUS κ α σ ρ –10º ι η R ε υ Spica M7 λ θ M104 Sombrero Galaxy ι RR G λ α κ LIBRA π M4 α ξ2 κ λ χ ψ µ δ ο σ Antares β 0º θ δ γ η θ Graffias β ν ψ ι µ τ υ η γ VIRGO 54 48 χ ο 44 δ φ Sabik ν β ζ υ +10º ξ ω τ φ ε ο π M5 ψ χ ξ ζ ρ δ µ ε ε σ E Q U AT O R ο β Vindemiatrix ω σ COMA BERENICES Denebola SERPENS α (Caput) ε +20º 93 24 α τ υ ζ λ OPHIUCHUS ν η Arcturus δ σ γ α ξ ι β LEO ι R φ Galaxies North Galactic Pole W M64 κ κ 66 γ β ρ κ γ α +30º σ ε Izar ω γ Rasalhague ρ π β α α Diffuse nebulae θ η δ Rasalgethi Planetary nebulae Cor Caroli δ CORONA BOREALIS ξ +40º γ µ ζ κ β β σ ε λ ν1 λ M13 HERCULES ν2 φ Globular clusters CANES VENATICI BOÖTES KEY TO MAP SYMBOLS 18h γ 16h β λ Mimosa β R 15h 14h 13h Gacrux γ CRUX δ ο2 12h ο1 –60º 451 STAR MAP 5: EQUATORIAL STARS, RA TO 12h, DEC ϩ60° TO Ϫ60° 12h +60º 11h 9h 8h 7h 6h υ 12 15 Megrez δ 0.0 and brighter 10h β Merak 0.1 – 0.5 The Plough γ Phecda δ φ M97 Owl Nebula 0.6 – 1.0 26 15 θ 1.1 – 1.5 +50º URSA MAJOR χ κ 1.6 – 2.0 2.1 – 2.5 ψ1 ψ6 21 ι LYNX π Menkalinan ψ4 ψ 2.6 – 3.0 31 10 UMa µ 47 +40º ψ5 λ ω ψ7 β ψ2 AURIGA ψ3 3.1 – 3.5 UU β 3.6 – 4.0 21 4.1 – 4.5 4.6 – 5.0 σ3 σ2 LEO MINOR ξ KEY TO STAR MAGNITUDES τ γ µ 54 LEO COMA BERENICES γ β The Sickle Regulus ξ ω χ σ ν α LIP β θ RT ι υ ε ω δ µ κ γ ε η δ α σ η χ2 ν λ α ρ η µ ζ γ Alhena S ε β µ 13 2237 Rosette Nebula Procyon ORION CANIS MINOR 18 δ1 δ ζ τ1 C SEXTANS ε θ –10º ε ι η δ CORVUS η γ ζ λ –20º ζ ε ν α γ CRATER φ HYDRA κ θ θ λ –30º α γ δ ο2 ξ ο η τ k ζ δ ο1 Wezen ω σ ANTLIA η h1 U ψ d λ κ π θ COLUMBA a η σ e ν L2 B D CENTAURUS C –50º VELA m C a c J PUPPIS V H τ δ H I.2391 κ φ x J Gacrux γ CRUX ο ο 12h x ο α χ A δ u 3372 11h η s h Eta Carinae Nebula 10h Canopus δ CARINA N g 3532 δ 452 Q M ρ –60º L1 P γ b p µ σ ζ ζ h2 w λ q v1,2 c q i Adhara f ι –40º CANIS MAJOR δ β ε ξ1 κ α ο LEP ξ2 ε Aludra η PYXIS ξ β ν1 ν2 Mirzam ν3 M41 ρ θ Sirius π 11 Y α ι 16 χ2,1 β θ µ M47 γ υ1 µ γ β α 12 β α MONOCEROS α λ υ2 U δ Alphard γ ν ξ 30 ξ ζ M35 GEMINI ζ τ2 ι δ φ κ η θ υ TIC τ α ω E Q U AT O R EC π λ σ CANCER ω ο τ β η ξ R 31 ρ χ χ Pollux β φ M44 Beehive ο π ψ ν α ι ο 0º γ η LEO Denebola π ξ δ θ VIRGO λ 60 93 +10º ρ2 υ ε Algieba ι κ ζ δ +20º θ RS +30º 5.1 – 5.5 ο π Castor α ρ α 46 ν θ 38 10 ι PICTOR Avior a 9h ε 8h 7h 6h STAR MAP 6: EQUATORIAL STARS, RA TO 6h, DEC ϩ60° TO Ϫ60° 5h 4h 3h 2h 1h χ η ξ δ ο µ β δ 48 Capella φ ι AURIGA η τ ν λ ω ω PERSEUS ρ γ TRIANGULUM ο ζ ι ζ χ1 ο2 ORION λ φ2,1 Bellatrix ψ Alnilam Alnitak ζ ρ π6 δ Mintaka θ 2,1 M43 Orion ι υ Saiph π2 λ µ µ λ ο ν κ ν ι ν µ ο2 ψ ε ζ ρ3 ρ2 EC τ9 θ ι TX TIC λ 0º τ8 τ5 τ6 τ4 τ ω2 β υ ω β South Galactic Pole π δ κ2 κ ζ –30º σ π µ η φ SCULPTOR θ β f α CAELUM –40º ι θ Acamar δ s γ e χ κ η1 λ ι HOROLOGIUM γ η ι φ λ2 λ1 τ ρ χ σ PHOENIX ζ α ι ε µ β δ R Ankaa κ ν ψ ERIDANUS α υ φ δ PICTOR ι α η2 y ζ –20º T ν µ g α ω1 Deneb Kaitos γ2 α FORNAX η2 –10º ψ ψ1 κ i β τ τ2 δ 43 41 γ ψ CETUS σ τ7 ρ υ2 ο ι χ ρ π υ1 η –50º π ζ γ p DORADO ζ λ 6h LIP η ζ ε τ1 ε β ω 30 η ERIDANUS COLUMBA ξ +10º δ µ ν ξ ε ζ θ π γ κ β ε Square of Pegasus ο δ RX µ β γ Algenib Mira λ ν2 γ +20º φ TV δ ο1 µ Phact PEGASUS χ ψ3 ο ξ1 α 32 ξ LEPUS λ α Galaxies ψ ψ1 ρ +30º 70 γ 54 σ α Alpheratz ζ η χ β γ ν 10 Diffuse nebulae PISCES ξ2 Menkar α ε τ ξ 53 γ σ η ξ π5 ω β τ α δ ι ARIES λ σ δ σ π ρ E Q U AT O R Rigel β η π 88 η σ Nebula κ ρ η Planetary nebulae θ ANDROMEDA λ κ δ 2,1 π3 π4 γ 32 ω σ 2,1 α ν ε τ ζ Hyades δ2,1 θ γ α 90 π1 Betelgeuse ε δ3 Aldebaran ο1 M45 Pleiades 37 R M33 Hamal κ 2,1 Globular clusters ι Andromeda Galaxy M31 π 41 η λ ψ β Mirach α ω ε 119 α υ τ M1 Crab Nebula U χ TAURUS Open clusters +40º ε φ +50º κ ν β δ ψ Elnath β R ξ 16 R ι Variable stars µ 17 χ λ ο π υ τ π ξ φ γ β Algol ε ω χ Almaak 58 Double stars σ ξ 51 ν ζ µ σ θ υ θ κ ε ρ ν φ α Menkalinan µ Schedir ζ σ ψ α τ Mirphak α λ π θ γ τ ρ η CASSIOPEIA +60º β Caph υ1 φ Double Cluster 884 869 CAMELOPARDALIS 0h υ2 KEY TO MAP SYMBOLS 6h κ 5h Achernar RETICULUM ε η TUCANA HYDRUS µ 4h α 3h 2h 1h 0h –60º 453 18h –30º STAR MAP 7: SOUTHERN STARS TO DEC Ϫ30° γ 19h δ ζ The constellations and their names are approved by the International Astronomical Union ε Kaus Australis 20 M55 η h SAGITTARIUS λ κ µ β CORONA AUSTRALIS θ δ 21 h α ζ η1 β1 ι –40º ε γ α θ2 θ1 δ2 β2 ε α δ1 MICROSCOPIUM ζ –50º θ ι κ ρ θ µ γ υ δ1 γ β ε θ β µ κ ρ δ β ε φ δ GRUS γ φ INDUS δ2 ζ ι ζ ε ο SX α ν ν TUCANA OCTANS ψ π η τ ε β κ α η ε π µ ρ κ ι ρ α ν σ δ γ λ φ µ χ η s ζ ζ2 κ ζ γ α Large Magellanic Cloud η R ε ζ 2h ι e PICTOR λ η2 η1 y α –60º λ γ γ δ ζ η2 β –50º δ CAELUM 3h f α g η i δ –40º β ρ 41 43 COLUMBA γ 4h KEY TO STAR MAGNITUDES ε κ α h δ β DORADO HOROLOGIUM ERIDANUS β –70º 2070 Tarantula Nebula θ δ ι θ Acamar φ γ η β ι FORNAX γ β RETICULUM R –90º –80º κ MENSA β ι κ π µ ν θ ε ζ Achernar χ ψ φ π δ ι ν HYDRUS PHOENIX South Pole µ π π2 α p χ σ τ γ3 λ2 β γ1 β λ η2 ζ υ 104 (47 Tuc) λ Small Magellanic Cloud η λ1 λ2 β θ ζ θ Ankaa ε ξ σ SCULPTOR φ ο δ κ γ υ γ ν ο ι µ2,1 σ α η π PAVO φ1 β α Alnair ρ π µ θ µ1 µ2 ι ν λ –80º λ ν δ ξ ω Peacock β Fomalhaut ν η ι α PISCIS AUSTRINUS α ξ ξ –70º τ α ζ λ TELESCOPIUM η –60º ι 22 h 1, 3, 3 3, 4, 1, 2, 5, 6 1, 5 4, 5, 8 4, 5, 3, 4 3 6, 6 3, 6, 4, 1h Andromeda Antlia Apus Aquarius Aquila Ara Aries Auriga Boötes Caelum Camelopardalis Cancer Canes Venatici Canis Major Canis Minor Capricornus Carina Cassiopeia Centaurus Cepheus Cetus Chamaeleon Circinus Columba Coma Berenices Corona Australis Corona Borealis Corvus Crater Crux Cygnus Delphinus Dorado Draco Eridanus Fornax Gemini Grus Hercules Horologium Hydra Hydrus 0h Map 23 h Constellation ο υ2 Phact 0.0 and brighter 0.1 – 0.5 0.6 – 1.0 1.1 – 1.5 1.6 – 2.0 2.1 – 2.5 2.6 – 3.0 3.1 – 3.5 3.6 – 4.0 4.1 – 4.5 4.6 – 5.0 5.1 – 5.5 α λ µ 5h ξ β ε γ σ –30º 6h 454 18h STAR MAP 8: SOUTHERN STARS TO DEC Ϫ30° –30º 17 h RR M7 ε ξ ζ µ α κ ε1 ε2 –50º π θ η h ζ γ Atria ζ ε ε κ –60º α σ β κ η η δ µ β θ α θ υ i ι p φ Avior U N a g –80º VOLANS q κ m M ε 2516 α ANTLIA α H δ VELA I.2391 ο –60º η c CARINA χ ψ λ a ε b A w V γ J τ e d Q H P –50º L1 σ PYXIS h2 ζ L2 β h1 Naos a q ν η α c π –40º v1,2 COLUMBA f PUPPIS θ 8h κ δ λ –30º µ J h c Canopus ο HYDRA x s S ι δ α C π u η p i β PICTOR β R α δ C3 2,1 ZZ ε ι γ π2 δ ξ Eta Carinae Nebula 3372 q θ κ ζ D ρ B I.2602 β Miaplacidus CENTAURUS σ λ Southern Pleiades η α γ Gacrux ο ω MENSA Mimosa x 3532 ν η β α ε δ ζ η θ1,2 CRUX µ λ n γ τ µ Acrux ζ2 ε MUSCA λ κ ι γ ι ζ θ ε ξ1 e Coalsack 4755 Coalsack ε η ε ζ α γ CHAMAELEON β κ South Pole –80º ι ξ2 δ d β CIRCINUS ι1 ν µ 5139 ω Omega Centauri R Hadar 12h δ ι ζ φ J η OCTANS υ υ V Rigil Kent θ y χ ζ α δ α ε θ δ α τ ι τ1 11 h –70º APUS ψ η Menkent ι1 γ ν ο π κ X β γ κ β λ ρ α c1 NORMA TRIANGULUM ι AUSTRALE β θ δ ζ –70º c2 ε κ η η –90º δ d ARA δ φ1 φ2 υ γ ω ν1 µ ζ PAVO LUPUS δ γ γ1 β γ λ ε ψ1 1, 5 5, 4, 2, 7, 3, 8 7, 3, 5, 3, 7, 1, 3, 5, 6, 7, 3, 5, 6, 3, 4 3, 3, 3, 3, 2, 4, 1, 5, 8 9h –40º ι µ ψ η σ λ χ θ η θ µ1 13h µ2 Map Indus Lacerta Leo Leo Minor Lepus Libra Lupus Lynx Lyra Mensa Microscopium Monoceros Musca Norma Octans Ophiuchus Orion Pavo Pegasus Perseus Phoenix Pictor Pisces Piscis Austrinus Puppis Pyxis Reticulum Sagitta Sagittarius Scorpius Sculptor Scutum Serpens Sextans Taurus Telescopium Triangulum Triangulum Australe Tucana Ursa Major Ursa Minor Vela Virgo Volans Vulpecula 10 h SCORPIUS h 14 υ 15 λ κ ι ι 16 h Shaula G Constellation ζ κ CANIS MAJOR Double stars Variable stars Open clusters Globular clusters Planetary nebulae Diffuse nebulae Galaxies KEY TO MAP SYMBOLS 7h 6h 455 ACKNOWLEDGEMENTS Abbreviations AMANDA – Antarctic Muon and Neutrino Detector Array AUI – Associated Universities, Inc AURA – Association of Universities for Research in Astronomy, Inc Caltech – California Institute of Technology CfA – Harvard-Smithsonian Center for Astrophysics CNES – Centre National d’Études Spatiales, France CXC – Chandra X-ray Observatory Center, HarvardSmithsonian Center for Astrophysics DLR – Deutschen Zentrum für Luft- und Raumfahrt DMI – David Malin Images DMSP – Defense Meteorological Satellite Program ERSDAC – Earth Remote Sensing Data Analysis Center, Tokyo ESA – European Space Agency ESO – European Southern Observatory FTS – Fourier Transform Spectrometer (Kitt Peak) GSFC – Goddard Space Flight Center IAC – Instituto de Astrofísica de Canarias ING – Isaac Newton Group of Telescopes IPAC – Infrared Processing and Analysis Center of California Institute of Technology ISAS – Institute of Space and Astronautical Science, Japan JAROS – Japan Resources Observation System Organization JHU – Johns Hopkins University JPL – Jet Propulsion Laboratory JSC – Johnson Space Center KSC – Kennedy Space Center LaRC – Langley Research Center MISR – Multi-angle Imaging SpectroRadiometer MIT – Massachusetts Institute of Technology MITI – Ministry of International Trade and Industry MPE – Max-Planck-Institut für extraterrestrische Physik, Garching NASA – National Aeronautics and Space Administration NCSSM – North Carolina School of Science and Mathematics NSO – National Solar Observatory NOAA – National Oceanic and Atmospheric Administration NOAO – National Optical Astronomy Observatory NRAO – National Radio Astronomy Observatory NSF – National Science Foundation RGO – Royal Greenwich Observatory SAO – Smithsonian Astrophysical Observatory SOHO – Solar and Heliospheric Observatory SOHO is a project of international cooperation between ESA and NASA STScI – Space Telescope Science Institute ST-ECF – Space Telescope European Coordinating Facility SwRI – Southwest Research Institute, Boulder, Colorado TRACE – Transition Region and Coronal Explorer, Lockheed Martin Solar and Astrophysics Laboratories USAF – US Air Force USGS – US Geological Survey WIYN – Univ Wisconsin, Indiana Univ., Yale Univ and NOAO t – top, b – bottom, l – left, r – right, c – centre Endpapers T A Rector/B A Wolpa/NOAO/AURA/NSF Half-title ESO Opposite title ESO Opposite Foreword ESO Opposite page NASA/JSC Nigel Sharp/NOAO/AURA/NSF 4l NASA/JPL/Malin Space Science Systems 4br NOAO/AURA/NSF 5t ESO 5b NASA/GSFC NASA 7t Science Photo Library 7b NASA/JPL NASA 10 NASA/JPL 13t NASA/JPL/Caltech 13b NASA/JPL/Cornell Univ 14 Science Photo Library 16 T A Rector/B A Wolpa/NOAO/AURA/NSF 18 Sir Patrick Moore Collection 19 AMANDA Collaboration 21 NASA/JPL 22t NASA 22b NASA/David R Scott 25 National Astronomy and Ionosphere Center/Cornell Univ./NSF 26 NASA/JPL 27t NASA/JPL 27b NASA/JPL/USGS 28t NASA/USAF 28b Chuck Claver, Nigel Sharp (NOAO)/WIYN/NOAO/NSF (Courtesy WIYN Consortium, Inc All Rights Reserved) 32 J and M Tichá, Klet Observatory, Czech Republic 34 David Parker/Science Photo Library 39 NASA 43 © Akira Fujii/DMI 45 © AngloAustralian Observatory, Photograph by David Malin 46 S Ostro (JPL/NASA) 47 The Boomerang Collaboration 48 ESO 49t All Rights Reserved Beagle (http://www.beagle2.com) 49b Robin Scagell/Science Photo Library 50 © Akira Fujii/DMI 51 ESO 52 NASA/JPL 53t A Dupree (CfA)/NASA/STScI 53b Big Bear Solar Observatory 56 Nik Szymanek (Univ Herts) based on data in the ING archive 57 NRAO/NSF 58 Bruce Balick and Jason Alexander (Univ Washington)/Arsen Hajian (US Naval Obs.)/Yervant Terzian (Cornell Univ.)/Mario Perinotto (Univ Florence)/Patrizio Patriarchi (Arcetri Observatory)/NASA 59 Rex Saffer (Villanova Univ.)/Dave Zurek (STScI) 62t NASA/JPL 62b T Nakajima and S Kulkarni (Caltech)/S Durrance and D Golimowski (JHU) 63 NOAO/AURA/NSF 65 NASA/JPL 68t NASA/JPL 68b NASA/JPL 70 Carl Grillmair (Caltech)/NASA/STScI 71 © Natural History Museum, London 72 © Anglo-Australian Observatory, Photograph by David Malin 73 NASA/JPL/Univ Arizona 74 © Akira Fujii/DMI 75t NASA/CXC/SAO 75b S Ostro (JPL/NASA) 79 NOAO/AURA/NSF 82 ESO 83 NASA/MIT/F Baganoff et al 84 NASA/JPL/USGS 86 NASA/JPL/USGS 87 ESA 88 H Weaver (JHU)/NASA 89 456 NOAO/AURA/NSF 91 © Anglo-Australian Observatory, Photograph by David Malin 92 © Anglo-Australian Observatory, Photograph by David Malin 97 John Caldwell (York Univ Ontario)/Alex Storrs (STScI)/NASA 98t Courtesy of the TRACE consortium, Stanford-Lockheed Institute for Space Research/NASA 98b NASA/JPL 99 Courtesy SOHO/LASCO Consortium 100 DMR/COBE/NASA/FourYear Sky Map 101 DMR/COBE/NASA/Two-Year Sky Map 103 P Garnavich (CfA) et al/STScI/NASA 104 ESO 105 ESO 106 NASA/JPL 107t ©Akira Fujii/DMI 107b NASA/JPL/Brown Univ 109t NASA/JPL 109b © AngloAustralian Observatory, Photograph by David Malin 110 Courtesy of the Deep Impact Mission/NASA (http://deepimpact.jpl.nasa.gov) 111 NASA 112 NASA/JPL 113 ESO 114 © Akira Fujii/DMI 116 ESO 118 © Akira Fujii/DMI 119 Bill Schoening/NOAO/AURA/NSF 121 ESO 122 NASA/JSC 125 A Cochran (Univ Texas)/STScI/NASA 126 L J King (Univ Manchester)/STScI/NASA 127 NASA/JPL/USGS 129 NOAO/AURA/NSF 130 © Anglo-Australian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 131t NASA/JPL/USGS 131b NASA/JPL 134 NASA/JHU Applied Physics Laboratory 135t A Fruchter and the ERO Team (STScI)/NASA 135b ©Anglo-Australian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 136 Univ Arizona/DLR/NASA/JPL 137 ESO 138 NASA 141t Courtesy SOHO/MDI Consortium 141b Dr S R McCandliss, Dr K R Sembach and the FUSE team 142 SEC/NOAA/US Department of Commerce 145 Courtesy SOHO EIT Consortium 147 © Anglo-Australian Observatory, Photograph by David Malin 148 Nigel Sharp/NOAO/NSO/Kitt Peak FTS/AURA/NSF 149 NASA/JPL 150 © Akira Fujii/DMI 152 NASA/JPL/DLR 153 NASA/JPL/Univ Arizona 154 ESO 155 NASA/JPL/Brown Univ 156 NASA/JPL/USGS 157 Gemini Observatory/NSF/Univ Hawaii Institute for Astronomy 159 S Ostro (JPL/NASA) 160 Nigel Sharp/NOAO/AURA/NSF 161 ESA/MPE 162 NOAO/AURA/NSF 163t Michael Rich, Kenneth Mighell and James D Neill (Columbia Univ.)/Wendy Freedman (Carnegie Observatories)/NASA 163b © AngloAustralian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 164 S Ostro (JPL/NASA) 165t G Scharmer/Swedish Vacuum Solar Telescope 165b A Fruchter and the ERO Team (STScI, ST-ECF)/NASA 166 ESO 167 NASA/JPL/Cornell Univ 170 © Akira Fujii/DMI 173 (x-ray) NASA/UMass/D Wang et al (optical) NASA/HST/D Wang 174 Courtesy SOHO/MDI Consortium 175 © Anglo-Australian Observatory, Photograph by David Malin 176 NASA/JPL/USGS 177 ESO 178 Sheila Terry/Science Photo Library 181 NASA/JPL 182 ESA 183 Sir Patrick Moore Collection/Ludolf Meyer 184 © AngloAustralian Observatory, Photograph by David Malin 185 Raghvendra Sahai and John Trauger (JPL)/WFPC2 science team/NASA 187 R Williams (STScI)/NASA 188 NASA/JSC 189 NASA/JPL 190 © Akira Fujii/DMI 193tl NASA/JPL/USGS 193tr NASA/JPL 193b Roger Lynds/NOAO/AURA/NSF 194l Johan Knapen/Nik Szymanek (Univ Herts) 194r Johan Knapen/Nik Szymanek (Univ Herts) based on data in the ING Archive 195 NASA/GSFC/LaRC/JPL/MISR Team 196 IPAC/JPL 197 IPAC/JPL 198 ESA/ISOCAM/ISOGAL Team 199 NASA/Hubble Heritage Team (STScI/AURA) 200 NASA/STS-108 Crew 201 ESA 204 NASA/JPL/Lunar and Planetary Laboratory 206t IPAC 206b Natural History Museum, London 207 Nik Szymanek (Univ Herts) 209 NASA/JPL 210 Ian Morison/Jodrell Bank Observatory 212 NASA/JPL/Univ Arizona 213t Reta Beebe/Amy Simon (New Mexico State Univ.)/STScI/NASA, 213b NASA/ESA/John Clarke (Univ Michigan) 214 NASA/JPL 215 © Anglo-Australian Observatory, Photograph by David Malin 216 NASA 218 © Anglo-Australian Observatory, Photograph by David Malin 219t NOAO/AURA/NSF 219b S Ostro (JPL/NASA) 221 A Caulet (ST-ECF, ESA)/NASA 222t NASA/JPL 222b NASA/LaRC 223 NASA/JPL 228 Alcatel Space Industries 230 NASA/GSFC/DMSP 231 NASA/Harold Weaver (JHU)/HST Comet LINEAR Investigation Team 236t NASA/JSC 236b NASA HQ 237 NASA/JSC 239 NOAO/AURA/NSF 241 © AngloAustralian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 244 ESO 245 NASA/JPL 246t NASA/JPL/USGS 246b NASA/JPL/Malin Space Science Systems 247 NASA/JPL/Malin Space Science Systems 249t NASA/JPL/GSFC 249b NASA/JPL 250 ESA/ESO/MACHO Project Team 251t NASA/JHU Applied Physics Team 251b Richard Wainscoat/Gemini Observatory/AURA/NSF 254 NASA/JPL 255 NASA/JPL 256 Daniel Bramich (ING)/Nik Szymanek (Univ Herts) 257 Alan Fitzsimmons 262 © Anglo-Australian Observatory, Photograph by David Malin 263 NASA/JPL 264t NASA/JSC 264b © Akira Fujii/DMI 265 NASA/JPL/USGS 268 NASA/JPL/USGS 269 NASA/JSC 274 Alistair Gunn, Jodrell Bank Observatory 276 Scott Manley and Duncan Steel 278t NASA/JPL 278b Lawrence Sromovsky (Univ Wisconsin-Madison)/STScI/NASA 279l NASA/JPL 279r NASA/JPL 280 NASA/JPL 281t Institute for Cosmic Ray Research, Univ Tokyo 281b NASA/NCSSM/C Olbert et al 284 Robin Scagell/Galaxy Picture Library 285t Ian King 285b Mike Shara, Bob Williams and David Zurek (STScI)/NASA 288t NASA/UMass/D Wang et al 288b NASA/JPL/USGS 289 NASA/JPL 290 NASA/JPL/Arizona State Univ 291 NASA/JPL/USGS 292t © Anglo-Australian Observatory, Photograph by David Malin 292b Todd Boroson/NOAO/AURA/NSF 295 © Akira Fujii/DMI 296 Mark McCaughrean/ESO 297 NOAO/AURA/NSF 298 C M Lowne 299 Dr Seth Shostak/Science Photo Library 302t NASA/JPL/USGS 302b John Bally (Univ Colorado)/NOAO/AURA/NSF 303t Mir 27 Crew © CNES 303b Courtesy SOHO/MDI Consortium 305 NASA/JPL/Malin Space Science Systems 308 Bill Schoening/NOAO/AURA/NSF 310 NASA/ESA/Hubble Heritage Team (STScI/AURA) 313 © Anglo-Australian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 314t Dr R Albrecht ESA/ESO/ST-ECF/NASA 314b A Stern (SwRI), B Buie (Lowell Observatory)/ESA/NASA 316 ESO 320 Courtesy SOHO/EIT Consortium 322 NASA/JPL 323 C R O’Dell/Rice Univ./NASA/STScI 324 NASA/JPL 325 NASA/CXC/SAO 327 John Bahcall, Institute for Advanced Study, Princeton/Mike Disney (Univ Wales)/NASA 328t Dr John Hutchings/Dominion Astrophysical Observatory/STScI 328b Gregory L Slater/Gary A Lindford/NASA/ISAS/Lockheed-Martin Solar and Astrophysics Laboratory of Japan/Univ Tokyo 329 NASA/JPL 332 NRAO/AUI 334 NASA/JPL 335 NASA/JPL/USGS 337 Prof J Huchra/HarvardSmithsonian Center for Astrophysics 338 NASA/Hubble Heritage Team (STScI/AURA) 340 NASA/JPL 341 NASA/JPL 343t NASA/JPL 343b © Anglo-Australian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 344t NASA/JPL 344b ESO 345 Bill Schoening/NOAO/AURA/NSF 346 MPE 347 © AngloAustralian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 349 ESO 351 NASA/MIT/F Baganoff et al 354t NASA/Hubble Heritage Team (STScI/AURA)/R G French (Wellesley College)/J Cuzzi and J Lissauer (NASA/Ames Reseach Center)/L Dones (SwRI) 354b J T Trauger (JPL)/NASA 355t NASA/JPL 355cr NASA/JPL 356 NASA/KSC 361 © Gran Telescopio CANARIAS (GTC), Instituto de Astrofísica de Canarias 362 SETI@home/Univ California, Berkeley 363 NOAO/AURA/NSF 364 NASA/KSC 365t NASA/JPL 365b Hubble Space Telescope Comet Team/NASA 368 CXC/NASA/SAO 369 NASA 370 Courtesy SOHO/LASCO Consortium 372 © Akira Fujii/DMI 373 Courtesy SOHO/MDI Consortium 374 Courtesy SOHO/LASCO Consortium 375t Rolf Kever/The Institute for Solar Physics of the Royal Swedish Academy of Sciences 375b ESA 376 © Anglo-Australian Observatory, Photograph by David Malin 377 Genesis Photo Library 378 NASA/KSC 383 NOAO/AURA/NSF 384 NOAO/AURA/NSF 387t © AngloAustralian Observatory, Photograph by David Malin 387b © Anglo-Australian Observatory, Photograph by David Malin 390 NASA/Donald Walter (S Carolina State Univ.)/ Paul Scowen and Brian Moore (Arizona State Univ.) 391 NASA/Jayanne English (Univ Manitoba)/Sally Hunsberger, Sarah Gallagher and Jane Charlton (Pennsylvania State Univ.)/Zolt Levay (STScI) 393 Courtesy SOHO/MDI Consortium 394 Courtesy SOHO/MDI Consortium 395 NASA/GSFC/U Hwang et al 396t Jeff Hester (Arizona State Univ.)/NASA 396b © Anglo-Australian Observatory, Photograph by David Malin 398t NASA/JPL 398b © Akira Fujii/DMI 399 Romano Corradi (IAC)/Mario Livio (STScI)/Ulisse Munari (Osservatorio Astronomico di Padova)/Hugo Schwarz (Nordic Optical Telescope)/NASA 400 © Anglo-Australian Observatory, Photograph by David Malin 401 NASA/JPL/Univ Arizona 402 NASA/JPL 403 NASA/JPL 405 NASA/JPL/Lunar and Planetary Observatory 409t STScI 409b NASA/JPL 410t NASA/GSFC 410b S Ostro (JPL/NASA) 411t Bill Livingston/NOAO/AURA/NSF 411b Alan Fitzsimmons 412 Robert Dalby/Nik Szymanek (Univ Herts) 413 NASA/JPL/USGS 415 ESO 416 © Anglo-Australian Observatory/Royal Observatory, Edinburgh, Photograph by David Malin 417 Courtesy Tunguska Page of Bologna Univ (http://www.th.bo.infn.it/tunguska) 419t NASA/Hubble Heritage Team (STScI) 419b NASA/KSC 420t Courtesy of the UK Infrared Telescope, Mauna Kea Observatory, Hawaii 420bl Nik Szymanek (Univ Herts) 420br Nik Szymanek (Univ Herts) 421 NASA/JPL 422 Heidi Hammel (MIT)/NASA/STScI 423 Kenneth Seidelmann, US Naval Observatory/NASA/STScI 424 © Akira Fujii/DMI 425 NASA/JPL/USGS 426 © IAC/RGO/Malin, Photograph by David Malin 428t © Anglo Australian Observatory, Photograph by David Malin 428b Novosti 429t NASA/JPL 429b NASA/JPL 430 ESO 431l Steve Massey 431r Steve Massey 432 NASA/JPL/USGS 433 NASA/GSFC/MITI/ERSDAC/JAROS and US/Japan ASTER 434 NASA/JPL 435 © Akira Fujii/DMI 436 Javier Méndez (ING)/Nik Szymanek (Univ Herts) 437 Harvey Richer (Univ British Columbia)/STScI/NASA 438 Nik Szymanek (Univ Herts) 439 © Anglo-Australian Observatory, Photograph by David Malin 441 NASA/CXC/Rutgers/J Hughes et al 442t NASA/SRON/MPE 442b (X-ray) NASA/CXC/SAO (optical) AURA/NOAO/NSF 443 ISAS 445 Domenic Cantin 447 ESO Illustration acknowledgements Artworks prepared by Philip’s/Raymond Turvey Stefan Chabluk 40 Cartography by Philip’s 122 and 408 Star Maps created by Wil Tirion 448–55 ... PATRICK MOORE HOW TO USE THE ENCYCLOPEDIA PHILIP’S ASTRONOMY ENCYCLOPEDIA First published in Great Britain in 1987 by Mitchell Beazley under the title The Astronomy Encyclopedia (General Editor.. .ASTRONOMY ENCYCLOPEDIA ASTRONOMY ENCYCLOPEDIA FOREWORD BY LEIF J ROBINSON Editor Emeritus, Sky & Telescope magazine... Dr Andrew J Hollis, BAA, UK James B Kaler, Department of Astronomy, University of Illinois, USA William C Keel, Department of Physics and Astronomy, University of Alabama, USA Professor Chris Kitchin,