Astronomy_Encyclopedia.pdf

ASTRONOMY

ENCYCLOPEDIA

ENCYCLOPEDIA

F OREWORD BY L EIF J. R OBINSON

Editor Emeritus, Sky & Telescope magazine

S TA R M APS CREATED BY W IL T IRION

GENERAL EDITOR SIR PATRICK MOORE

ASTRONOMY

HOW TO USE THE ENCYCLOPEDIA

P HILIP ’ S A STRONOMY E NCYCLOPEDIA

First published in Great Britain in 1987 by Mitchell Beazley

under the title The Astronomy Encyclopedia (General Editor

Patrick Moore)

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).

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

ISBN 0–540–07863–8

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.

Cross-references

SMALL CAPITALS 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.

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 tele-

scope 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 usu-

ally 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 10 3 is a

thousand, 2 10 6 is two million, and so on. ‘Billion’ always means a thousand million,

or 10 9 . As is customary in astronomy, dates are expressed in the order year, month,

day. Details of units of measurement, conversion factors and the principal abbrevia-

tions used in the book will be found in the tables on this page.

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

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 mag-

nitude is given for double stars, and the average magnitude for variable stars.

THE GREEK ALPHABET

αΑ

alpha

eta

θΘ

ξΞ

tau

υΥ

βΒ

beta

theta

οΟ

upsilon

φΦ

γΓ

gamma

iota

κΚ

omicron

πΠ

phi

χΧ

Star Maps pages 447–55

δ∆

delta

kappa

λΛ

chi

ψΨ

εΕ

epsilon

lambda

µΜ

ρΡ

rho

psi

ωΩ

Acknowledgements page 456

ζΖ

zeta

σΣ

sigma

omega

MULTIPLES AND SUBMULTIPLES

USED WITH SI UNITS

F RONTMATTER 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.

Multiple Preﬁx Symbol Submultiple Preﬁx Symbol

10 3

kilo-

10 3

milli-

10 6

mega- M

10 6

micro- m

10 9

giga-

10 9

nano-

10 12

tera-

10 12

pico-

10 15

peta-

10 15

femto- f

10 18

exa-

10 18

atto-

SYMBOLS FOR UNITS, CONSTANTS AND QUANTITIES

CONVERSION FACTORS

semimajor axis

L luminosity

L n Lagrangian points

( n = 1 to 5)

l.y. light-year

m metre, minute

m apparent magnitude, mass

m bol bolometric magnitude

m pg photographic magnitude

m pv photovisual magnitude

m v

t time

T temperature (absolute), epoch

(time of perihelion passage)

T eff effective temperature

Distances

1 nm = 10 Å

1 inch = 25.4 mm

1 mm = 0.03937 inch

1ft = 0.3048 m

1 m = 39.37 inches = 3.2808 ft

1 mile = 1.6093 km

1 km = 0.6214 mile

1 km/s = 2237 mile/h

1 pc = 3.0857

angstrom unit

astronomical unit

speed of light

distance

velocity

eccentricity

watt

energy

year

electron-volt

redshift

following

constant of aberration,

right ascension

focal length, force

visual magnitude

10 13 km = 3.2616 l.y. = 206,265 AU

acceleration due to gravity

absolute magnitude,

mass (stellar)

declination

10 12 km = 0.3066 pc = 63,240 AU

Temperatures (to the nearest degree)

°C to °F :

gauss

wavelength

gravitational constant

newton

proper motion

1.8, 32

hour

preceding

frequency

°C to K :

273

Planck constant

orbital period

parallax

°F to °C :

32,

1.8

H o

Hubble constant

parsec

longitude of perihelion

°F to K :

1.8,

255

hertz

perihelion distance

Ω

observed/critical density

ratio, longitude of ascending

node

K to °C :

273

inclination

q o

deceleration parameter

K to °F :

1.8, 460

Index Catalogue

aphelion distance

Note: To convert temperature differences , rather than points on the

temperature scale, ignore the additive or subtractive ﬁgure and just

multiply or divide.

jansky

radius, distance

degree

Boltzmann constant

Roche limit

arcminute

degrees kelvin

second

arcsecond

ηΗ

νΝ

τΤ

ιΙ

1 l.y. = 9.4607

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