The New Cosmos: An Introduction to Astronomy and Astrophysics

571 Pages·2002·25.63 MB·English

Fundamental Physical Constants1
Constant SI Units Gaus ian Units
w-
Gravitational con tant, G 6.673 · 10-I I m3 kg-I -2 6.67 . 8 cm3 g-1 s-2
Velocity of light in vacuum, c 2.9979· 108 m -I 2.9979· 1010 cms- 1
o-
Magnetic field constant, JJ-o 1.2566 · I 6 m kg -2 A -2
= V A-1 m-1
Electric field con tant, eo 8.8542·10-12 m-3kg- 1 4A2
= Asv-1m- 1
Planck's constant. h 6.6261 .w-34 m2 kgs- 1 = J s 6.6261 . w-21 ergs
h = h/2rr 1.0546· Io-34 Js 1.0546. w-27 erg
Elementary (electron· ) charge. e 1.6022. 10-19 A = c 4. 032. w - IO esu
Atomic ma unit. mu = u 1.6605. 10-27 kg 1.6605. w-24 g
Ret ma ofth
o-
proton lllp 1.6726. 1 27 kg 1.6726. lo-24 g
1.0073 u
neutron mn 1.6749. w-27 kg 1.6749. w-24 g
1.0087 u
electron me 9.1094· 10-31 kg 9.1094·10-28g
w-.;
5 .4858 . u
hydrogen atom ntH 1.6736. 10-27 kg 1.6736. 1o -24 g
1.0078 u
tnp/llle 1.8362. 103
pecific charge of the electron, efme 1.7588-1011 Ckg-1 5.2728 · 1017 e u g- 1
Avogadro's number, NA 6.0221· 1023 mol- 1
Univer al gas con tant, :R 8.3145 Jmol-tK-1 8.3145· 107 ergmol- 1 K- 1
Boltzmann' con tant. k 1.3807·10-23 JK- 1 1.3807 · I0-16ergK-I
Fine- tructure con tant, a 7.2974· w-3 = 1/137.036
Compton wavelength of the
proton Ap 1.3214·10-15 m 1.3214·10- 13cm
electron Ae 2.4263. 10-12 m 2.4263. w-IO em
o-
2.4263. 1 2
Classical electron radiu , rc 2.8179·10- 15 m 2. 179·10-13em
Thomson cro ection, aT 6.6525. 1o -29 m2 6.6525 · 10-25 cm2
Rydberg's con tant, R 1.0974· 107 m- 1 1.0974 · lo5 cm-1
1/911.27 -I
I st Bohr radiu . ao 5.2918· 10-11 m 5.2918. w-9 em
Planck' radiation constant. c2 1.4388. w-2 mK 1.4388 em K
tefan-Boltzmann
radiation con tant. a 5.6704. 1o -8 wm-2K-4 5.6704·10-5 ergcm-2 s- 1 K-4
1 All numerical values were rounded to 5 significant digits. For more precise values (with error limits) see P.J. Mohr,
B.N. Taylor: CODATA recommended values of the fundamental physical constants: 1998. Rev. Modem Phys. 72, 351
(2000)
Astronomical Constants and Units
A tronomical unit I AU= 1.496· 1011 m
= 499.0 light second.
Parsec I pc = 3.086 · 1016 m = 2.063. 105 A
= 3.261ight years
idereal year 365.256d = 3.1558. 107 s
Tropical year 365.242d = 3.1557. 107 s
Magnitude I mag corrc. ponds to a
brightness ratio of 2.512 = I 0°..1
Earrlz:
Equatorial radius RE = 6.378 ·106m
Mas ME=5.973· 1024kg
olar onstant S = 1.37kwm-2
Sun:
Radius R0 = 6.960· 10M m
o
Mas .M.0 = 1. 989 . 1 30 kg
Luminosity L'0 =3.846· I0~6w
Effective temperature Tell. ., = 5780 K
urface gravity g~Z. =2.736·102m ~
Ab olute vi ual magnitude Mv.0= 4.87 mag
Milky Way:
=
Distance un -galactic center Ro 8.5 kpc
Rotational velocity Vt> = 220 km s - I
CtJQ =26kms 1 kpc-1
Rotational period to = 2JT /CtJQ = 2.4- 108 yr
Oort con ·tants A = 14kms- 1 kpc 1
8 = - 12 km s 1 kpc 1
Universe:
Hubble con tant Ho =50hkms- 1Mpc- 1
=
h Ho/(50kms- 1 Mpc- 1) ,-, ~ 1.4
Hubble time ro = 1/Ho = 6.2·1017 ii-1 s
=
19.6· 109 1!- I yr
Critical density Qc.O = 4.7 · I 0 27 ii~ kg m-3
llc.o = 3 ii2 m-3
Temperature of the
microwave background radiation To = 2.73K
Planck time Tp = 5.4 · 10 .j.j
Albrecht Unsold
Bodo Baschek
The New Cosmos
Albrecht Unsold
Bodo Baschek
The New
cosmos
An lntroduction
to Astronomy
and Astrophysics
Translated by
William D. Brewer
Fifth Edition
With 278 Figures
lncluding 20 Color Figures
Professor Dr. Albrecht Unsold t
Professor Dr. Bodo Baschek
Institut fiir Theoretische Astrophysik
Universitat Heidelberg
Albert-Oberie-StraBe 2
69120 Heidelberg, Germany
Translator:
Professor William D. Brewer, Ph. D.
Fachbereich Physik, Freie Universitat Berlin, Arnimallee 14,
14195 Berlin, Germany
Corrected 2nd printing
ISBN 978-3-642-08746-2 This work is subject to copyright. All rights are reserved, whether the
whole or part of the material is concerned, specifically the rights of
translation, reprinting, reuse of illustrations, recitation, broadcasting,
reproduction on microfilm or in any other way, and storage in data
banks. Duplication of this publication or parts thereof is permitted only
under the provisions of the German Copyright Law of September 9,
Library of Congress Cataloging-in-Publication Data. 1965, in its current version, and permission for use must always be
Unsold, Albrecht, 1905-[Neue Kosmos. English] The new cosmos: obtained from Springer-Verlag Berlin Heidelberg GmbH.
an introduction to astronomy and astrophysics.-5th ed./ Albrecht Un Violations are liable for prosecution under
sOld, Bodo Baschek; translated by William D. Brewer. p. em. Includes the German Copyright Law.
bibliographical references and index.
ISBN 978-3-642-08746-2 ISBN 978-3-662-04356-1 (eBook) springeronline.com
DOI 10.1007/978-3-662-04356-1
I. Astronomy. I. Baschek, B., 1935-II. Title
QB43.3 .U5713 2001 520-dc21 2001034462 ©Springer-Verlag New York Inc. 1969, 1977, 1983
Cover: Optical image of the radio galaxy NGC5128 = Centaurus A. © Springer-Verlag Berlin Heidelberg 1991, 2001
Recorded by the Anglo-Australian Telescope. ( © Anglo-Australian
Observatory, photograph by David Malin)
The use of general descriptive names, registered names, trademarks,
Frontispiece: The galaxy group (NGC 6769-71) in Pavo with indica etc. in this publication does not imply, even in the absence of a specific
tions of gravitational interaction between the galaxies: faint haloes statement, that such names are exempt from the relevant protective
and connecting arcs, deforming of spiral arms and central regions. laws and regulations and therefore free for general use.
(By S. Laustsen with the 3.6 m-telescope of the European Southern
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Title of the German edition: Layout: Schreiber VIS, Seeheim
A. Unsold, B. Baschek: Der neue Kosmos. Siebte Auflage Cover Design: Erich Kirchner, Heidelberg
© Springer-Verlag Berlin Heidelberg
1967, 1974, 1981, 1988, 1991, 1999, 2002
Originally published by Springer-Verlag Berlin Heidelberg New York in 2002
Printed on acid-free paper
Softcover reprint of the hardcover 5th edition 2002
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ISBN 978-3-642-08746-2
v
Preface to the Corrected Reprint
In the preparation of this corrected and updated reprint I take this opportunity to note that, to my great plea
of the 5th edition, Prof. Wolfgang J. Duschl once more sure, Wolfgang J. Dusch! is prepared to work together
provided active help with many contributions and ex with me as author of all further, new editions of "The
citing discussions. My dearest thanks to him. I would New Cosmos".
also like to thank Prof. W. Beiglbt:ick and Claus-Dieter
Bachem from Springer most sincerely for their con
structive collaboration in the preparation of this reprint. Heidelberg, December 2004 Bodo Baschek
Preface to the 5th Edition
Albrecht Unsold's Der Neue Kosmos, in which he gave tern to the most distant galaxies. In this new edition, the
an overview of the whole field of astronomy that was organization of the material has been made clearer by
intended to be accessible to all students and practition introducing some changes in the order of presentation
ers of the natural sciences, first appeared in 1967. The as well as by a finer subdivision of the topics covered.
title was deliberately chosen with reference to Alexan Within our Solar System, space probes have inves
der von Humboldt's Kosmos and expressed the author's tigated the Moon and Mars, the Jupiter system, some
intention of "making our new understanding of the Uni of the asteroids, and the solar wind from close up. New
verse clear" to a wide group of readers and of "allowing satellites have brought an enormous increase in observa
the basic ideas of the various areas of astronomical tion power ranging from the gamma-ray region down to
research with their factual and historical-humanistic the radiofrequency spectral range; especially notewor
connections to come into the foreground". After the thy is the Hubble Space Telescope with its incomparable
third edition, new editions of the book were prepared angular resolution in the optical and near-ultraviolet,
with the collaboration of B. Baschek, who gradually as well as the two large X-ray satellites, Chandra and
took over responsibility for it. Prof. Dr. Dr. h.c. mult. Al XMM Newton. Furthermore, in the past decade, a new
brecht Unsold died in 1995 at the age of 90; he was generation of large earthbound telescopes based on
a pioneer and an Old Master of astrophysics. Although active and adaptive optics has come into use.
he announced his retirement from active research "of Among the discoveries and events of this period we
ficially" in 1988 in the Foreword to the 4th German mention the following: the numerous planetoids found
edition of this book, he remained keenly interested in outside the orbit of Neptune, the impact of a comet onto
the further development of this introduction to astron Jupiter, and the appearance of the bright comets Hyaku
omy and astrophysics and continued to contribute to its take and Hale-Bopp; advances in solar seismology, the
revisions through discussions and observations. resolution of very detailed structures in the regions of
Now, ten years after the appearance of the 4th edi star formation and in planetary nebulae, the evidence
tion, a completely revised and updated version of the for black holes in the centers of our Milky Way and of
New Cosmos, translated from the 7th German edition, other galaxies; the observation of very distant supernova
has been completed; it takes into account the wealth explosions, and the precise determination of the fluctu
of new results from astronomical research which have ations in the 3 K cosmic background radiation, giving
appeared in recent years, ranging from our Solar Sys- indications of a flat Universe with a nonzero cosmo-
VI
logical constant; the view of most distant galaxies in and suggestions on numerous topics. In particular, I owe
the Hubble Deep Field, obtained with the Hubble Space sincere thanks to Prof. Wolfgang J. Duschl for his aid in
Telescope; the new evidence for neutrino oscillations, the choice of new illustrations and for their acquisition
the explanation of the origin of the gamma-ray bursts and electronic image processing.
which had remained a riddle for decades; and finally the It was a great asset for the preparation of this book
discoveries of numerous planets orbiting nearby stars. that Prof. William D. Brewer was once again willing to
My thanks go to all those readers of the earlier undertake the translation. I wish to express my heartfelt
editions who have contributed to the improvement of thanks for his excellent job as well as for very agree
this book through their suggestions, criticisms and able and constructive collaboration. Prof. W. Beiglbock,
detection of errors. Furthermore, I wish to thank my col Dr. H. Lotsch, and Mr. C.-D. Bachem of Springer
leagues W.J. Duschl, D. Fiebig, B. Fuchs, H. Holweger, Verlag are due my sincere gratitude for their excellent
G. Klare, M. Scholz, A. Schwope, P. Ulmschneider, cooperation, as always, in the completion of this edition.
C. van de Bruck, R. Wehrse, and G. Weigelt for criti
cal readings of various sections and for their comments Heidelberg, June 2001 Bodo Baschek
VII
Contents
1. Introduction................................................................................................... 1
I. Classical Astronomy and the Solar System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Humanity and the Stars: Observing and Thinking
Historical Introduction to Classical Astronomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Classical Astronomy 2.1 Spatial Coordinates and Time;
the Motions of the Sun, the Earth, and the Moon . . . . . . . . . . 10
2.1.1 The Celestial Sphere
and Astronomical Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.2 The Motions of the Earth. Seasons and the Zodiac . . . . . . . . . . . . 12
2.1.3 Time: Days, Years, and the Calendar . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.4 The Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1.5 Eclipses of the Sun and the Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Orbital Motions and Distances in the Solar System . . . . . . . 20
2.2.1 Planetary Motions and Orbital Elements . . . . . . . . . . . . . . . . . . . . . . 20
2.2.2 Comets and Meteors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.3 Distance Determination,
the Doppler Effect and Aberration of Light . . . . . . . . . . . . . . . . . . . 25
2.3 Mechanics and Gravitational Theory . . . . . . . . . . . . . . . . . . . . . . . 27
2.3.1 Newton's Laws of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 28
2.3.2 The Conservation of Linear Momentum . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.3 Conservation of Angular Momentum: the Area Theorem . . . . . 29
2.3.4 Conservation of Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.5 The Virial Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3.6 The Law of Gravitation. Gravitational Energy . . . . . . . . . . . . . . . . 31
2.4 Celestial Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.4.1 Kepler's First and Second Laws: Planetary Orbits . . . . . . . . . . . . 33
2.4.2 Kepler's Third Law: Determination of Masses . . . . . . . . . . . . . . . . 34
2.4.3 Conservation of Energy and the Escape Velocity . . . . . . . . . . . . . . 35
2.4.4 Rotation and the Moment of Inertia . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.5 Precession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4.6 The Tides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4.7 The Ptolemaic and the Copernican Worldviews . . . . . . . . . . . . . . . 37
2.5 Space Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.5.1 The Orbits of Artificial Satellites and Space Vehicles . . . . . . . . . 39
2.5.2 Astronomical Observations from Space . . . . . . . . . . . . . . . .. . .. . .. 40
2.5.3 The Exploration of the Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.5.4 Space Probe Missions in the Solar System . . . . . . . . . . . . . . . . . . . . 43
I
Cooteot<
VIII
3. The Physical Structure 3.1 Global Properties of the Planets and Their Satellites . . . . . . 46
of the Objects 3.1.1 Ways of Studying the Planets and Their Satellites . . . . . . . . . . . . 46
in the Solar System 3.1.2 The Global Energy Balance of the Planets . . . . . . . . . . . . . . . . . . . . 48
3.1.3 Interior Structure and Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.1.4 The Structures of Planetary Atmospheres . . . . . . . . . . . . . . . . . . . . . 50
3.2 The Earth, the Moon, and the Earthlike Planets . . . . . . . . . . . 51
3.2.1 The Internal Structures of the Earthlike Planets . . . . . . . . . . . . . . . 52
3.2.2 Radioactive Dating. The Earth's History . . . . . . . . . . . . . . . . . . . . . . 53
3.2.3 Magnetic Fields. Plate Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.2.4 The Lunar Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.2.5 The Surfaces of the Earthlike Planets . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.2.6 The Atmospheres of the Earthlike Planets . . . . . . . . . . . . . . . . . . . . . 66
3.3 Asteroids or Small Planets (Planetoids) . . . . . . . . . . . . . . . . . . . . . 69
3.3.1 The Orbits of the Asteroids . ... ... .. .. . .. . .. .. .. . .. . .. .. . .. .. . . 70
3.3.2 Properties of the Asteroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.4 The Major Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3.4.1 Jupiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3.4.2 Saturn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.4.3 Uranus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.4.4 Neptune . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.5 Pluto and the Transneptunian Objects . . . . . . . . . . . . . . . . . . . . . . 84
3.5.1 Pluto and Charon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
3.5.2 The Transneptunian Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.6 Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.6.1 Structure, Spectra, and Chemical Composition . . . . . . . . . . . . . . . . 87
3.6.2 The Evolution of Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.7 Meteors and Meteorites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.7.1 Meteorites and Impact Craters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.7.2 Meteors in the Earth's Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
3.7.3 Properties and Origins of Meteorites . . . . . . . . . . . . . . . . . . . . . . . . . . 91
3.8 Interplanetary Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
II. Radiation, Instruments, and Observational Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
The Development of Astronomical Observation Methods
Historical Introduction to Our Knowledge of the Electromagnetic Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . 98
4. Radiation and Matter 4.1 Electromagnetic Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.2 The Theory of Special Relativity ............................ 102
4.2.1 The Lorentz Transformation. The Doppler Effect . . . . . . . . . . . . . 103
4.2.2 Relativistic Mechanics ......................................... 103
4.3 The Theory of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.3.1 Phenomenological Description of Radiation . . . . . . . . . . . . . . . . . . 104
4.3.2 Emission and Absorption. The Radiation Transport Equation 107
4.3.3 Thermodynamic Equilibrium and Black-Body Radiation ..... 109