Fundamental Astronomy fifth edition

Fundamental Astronomy H Karttunen P Kröger H Oja M Poutanen K J Donner (Eds.) Fundamental Astronomy Fifth Edition With 449 Illustrations Including 34 Colour Plates and 75 Exercises with Solutions 123 Dr Hannu Karttunen University of Turku, Tuorla Observatory, 21500 Piikkiö, Finland e-mail: hannu.karttunen@utu.fi Dr Pekka Kröger Isonniitynkatu C 9, 00520 Helsinki, Finland e-mail: pekka.kroger@stadia.fi Dr Heikki Oja Observatory, University of Helsinki, Tähtitorninmäki (PO Box 14), 00014 Helsinki, Finland e-mail: heikki.oja@helsinki.fi Dr Markku Poutanen Finnish Geodetic Institute, Dept Geodesy and Geodynamics, Geodeetinrinne 2, 02430 Masala, Finland e-mail: markku.poutanen@fgi.fi Dr Karl Johan Donner Observatory, University of Helsinki, Tähtitorninmäki (PO Box 14), 00014 Helsinki, Finland e-mail: donner@astro.helsinki.fi ISBN 978-3-540-34143-7 5th Edition Springer Berlin Heidelberg New York ISBN 978-3-540-00179-9 4th Edition Springer-Verlag Berlin Heidelberg New York Library of Congress Control Number: 2007924821 Cover picture: The James Clerk Maxwell Telescope Photo credit: Robin Phillips and Royal Observatory, Edinburgh Image courtesy of the James Clerk Maxwell Telescope, Mauna Kea Observatory, Hawaii Frontispiece: The Horsehead Nebula, officially called Barnard 33, in the constellation of Orion, is a dense dust cloud on the edge of a bright HII region The photograph was taken with the 8.2 meter Kueyen telescope (VLT 2) at Paranal (Photograph European Southern Observatory) Title of original Finnish edition: Tähtitieteen perusteet (Ursan julkaisuja 56) © Tähtitieteellinen yhdistys Ursa Helsinki 1984, 1995, 2003 Sources for the illustrations are given in the captions and more fully at the end of the book Most of the uncredited illustrations are © Ursa Astronomical Association, Raatimiehenkatu 3A2, 00140 Helsinki, Finland 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, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag Violations are liable for prosecution under the German Copyright Law Springer is a part Springer Science+Business Media www.springer.com © Springer-Verlag Berlin Heidelberg 1987, 1994, 1996, 2003, 2007 The use of general descriptive names, registered names, trademarks, etc in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use Typesetting and Production: LE-TeX, Jelonek, Schmidt & Vöckler GbR, Leipzig Cover design: Erich Kirchner, Heidelberg/WMXDesign, Heidelberg Layout: Schreiber VIS, Seeheim Printed on acid-free paper SPIN: 11685739 55/3180/YL V Preface to the Fifth Edition As the title suggests, this book is about fundamental things that one might expect to remain fairly the same Yet astronomy has evolved enormously over the last few years, and only a few chapters of this book have been left unmodified Cosmology has especially changed very rapidly from speculations to an exact empirical science and this process was happening when we were working with the previous edition Therefore it is understandable that many readers wanted us to expand the chapters on extragalactic and cosmological matters We hope that the current edition is more in this direction There are also many revisions and additions to the chapters on the Milky Way, galaxies, and cosmology While we were working on the new edition, the International Astronomical Union decided on a precise definition of a planet, which meant that the chapter on the solar system had to be completely restructured and partly rewritten Over the last decade, many new exoplanets have also been discovered and this is one reason for the increasing interest in a new branch of science – astrobiology, which now has its own new chapter In addition, several other chapters contain smaller revisions and many of the previous images have been replaced with newer ones Helsinki December 2006 The Editors VI Preface to the First Edition The main purpose of this book is to serve as a university textbook for a first course in astronomy However, we believe that the audience will also include many serious amateurs, who often find the popular texts too trivial The lack of a good handbook for amateurs has become a problem lately, as more and more people are buying personal computers and need exact, but comprehensible, mathematical formalism for their programs The reader of this book is assumed to have only a standard highschool knowledge of mathematics and physics (as they are taught in Finland); everything more advanced is usually derived step by step from simple basic principles The mathematical background needed includes plane trigonometry, basic differential and integral calculus, and (only in the chapter dealing with celestial mechanics) some vector calculus Some mathematical concepts the reader may not be familiar with are briefly explained in the appendices or can be understood by studying the numerous exercises and examples However, most of the book can be read with very little knowledge of mathematics, and even if the reader skips the mathematically more involved sections, (s)he should get a good overview of the field of astronomy This book has evolved in the course of many years and through the work of several authors and editors The first version consisted of lecture notes by one of the editors (Oja) These were later modified and augmented by the other editors and authors Hannu Karttunen wrote the chapters on spherical astronomy and celestial mechanics; Vilppu Piirola added parts to the chapter on observational instruments, and Göran Sandell wrote the part about radio astronomy; chapters on magnitudes, radiation mechanisms and temperature were rewritten by the editors; Markku Poutanen wrote the chapter on the solar system; Juhani Kyröläinen expanded the chapter on stellar spectra; Timo Rahunen rewrote most of the chapters on stellar structure and evolution; Ilkka Tuominen revised the chapter on the Sun; Kalevi Mattila wrote the chapter on interstellar matter; Tapio Markkanen wrote the chapters on star clusters and the Milky Way; Karl Johan Donner wrote the major part of the chapter on galaxies; Mauri Valtonen wrote parts of the galaxy chapter, and, in collaboration with Pekka Teerikorpi, the chapter on cosmology Finally, the resulting, somewhat inhomogeneous, material was made consistent by the editors The English text was written by the editors, who translated parts of the original Finnish text, and rewrote other parts, updating the text and correcting errors found in the original edition The parts of text set in smaller print are less important material that may still be of interest to the reader For the illustrations, we received help from Veikko Sinkkonen, Mirva Vuori and several observatories and individuals mentioned in the figure captions In the practical work, we were assisted by Arja Kyröläinen and Merja Karsma A part of the translation was read and corrected by Brian Skiff We want to express our warmest thanks to all of them Financial support was given by the Finnish Ministry of Education and Suomalaisen kirjallisuuden edistämisvarojen valtuuskunta (a foundation promoting Finnish literature), to whom we express our gratitude Helsinki June 1987 The Editors VII Contents Introduction 1.1 1.2 1.3 The Role of Astronomy Astronomical Objects of Research The Scale of the Universe Spherical Astronomy 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 Spherical Trigonometry The Earth The Celestial Sphere The Horizontal System The Equatorial System Rising and Setting Times The Ecliptic System The Galactic Coordinates Perturbations of Coordinates Positional Astronomy Constellations Star Catalogues and Maps Sidereal and Solar Time Astronomical Time Systems Calendars Examples Exercises 11 14 16 16 17 20 20 21 21 25 29 30 32 34 38 41 45 Observations and Instruments 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Observing Through the Atmosphere Optical Telescopes Detectors and Instruments Radio Telescopes Other Wavelength Regions Other Forms of Energy Examples Exercises 47 49 64 69 76 79 82 82 Photometric Concepts and Magnitudes 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Intensity, Flux Density and Luminosity Apparent Magnitudes Magnitude Systems Absolute Magnitudes Extinction and Optical Thickness Examples Exercises 83 85 86 88 88 91 93 Radiation Mechanisms 5.1 5.2 5.3 5.4 5.5 Radiation of Atoms and Molecules The Hydrogen Atom Line Profiles Quantum Numbers, Selection Rules, Population Numbers Molecular Spectra 95 97 99 100 102 Contents VIII 5.6 5.7 5.8 5.9 5.10 5.11 5.12 Continuous Spectra Blackbody Radiation Temperatures Other Radiation Mechanisms Radiative Transfer Examples Exercises 102 103 105 107 108 109 111 Celestial Mechanics 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 Equations of Motion Solution of the Equation of Motion Equation of the Orbit and Kepler’s First Law Orbital Elements Kepler’s Second and Third Law Systems of Several Bodies Orbit Determination Position in the Orbit Escape Velocity Virial Theorem The Jeans Limit Examples Exercises 113 114 116 116 118 120 121 121 123 124 125 126 129 The Solar System 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 Planetary Configurations Orbit of the Earth and Visibility of the Sun The Orbit of the Moon Eclipses and Occultations The Structure and Surfaces of Planets Atmospheres and Magnetospheres Albedos Photometry, Polarimetry and Spectroscopy Thermal Radiation of the Planets Mercury Venus The Earth and the Moon Mars Jupiter Saturn Uranus and Neptune Minor Bodies of the Solar System Origin of the Solar System Examples Exercises 133 134 135 138 140 144 149 151 155 155 158 161 168 171 178 181 186 197 201 204 Stellar Spectra 8.1 8.2 8.3 8.4 8.5 8.6 Measuring Spectra The Harvard Spectral Classification The Yerkes Spectral Classification Peculiar Spectra The Hertzsprung Russell Diagram Model Atmospheres 207 209 212 213 215 216 Contents IX 8.7 8.8 What Do the Observations Tell Us? 217 Exercise 219 Binary Stars and Stellar Masses 9.1 9.2 9.3 9.4 9.5 9.6 Visual Binaries Astrometric Binary Stars Spectroscopic Binaries Photometric Binary Stars Examples Exercises 222 222 222 224 226 227 10 Stellar Structure 10.1 10.2 10.3 10.4 10.5 10.6 Internal Equilibrium Conditions Physical State of the Gas Stellar Energy Sources Stellar Models Examples Exercises 229 232 233 237 240 242 11 Stellar Evolution 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 Evolutionary Time Scales The Contraction of Stars Towards the Main Sequence The Main Sequence Phase The Giant Phase The Final Stages of Evolution The Evolution of Close Binary Stars Comparison with Observations The Origin of the Elements Example Exercises 243 244 246 249 252 254 255 257 259 260 12 The Sun 12.1 12.2 12.3 12.4 12.5 Internal Structure The Atmosphere Solar Activity Example Exercises 263 266 270 276 276 13 Variable Stars 13.1 13.2 13.3 13.4 13.5 Classification Pulsating Variables Eruptive Variables Examples Exercises 280 281 283 289 290 14 Compact Stars 14.1 14.2 14.3 14.4 14.5 14.6 White Dwarfs Neutron Stars Black Holes X-ray Binaries Examples Exercises 291 292 298 302 304 305 15 The Interstellar Medium 15.1 15.2 15.3 15.4 Interstellar Dust Interstellar Gas Interstellar Molecules The Formation of Protostars 307 318 326 329 Colour Supplement 496 Plate Plate Colour Supplement 497 Plate Plate Colour Supplement 498 Plate Plate Colour Supplement 499 Plate Plate 10 Colour Supplement 500 Plate 11 Plate 12 Colour Supplement 501 Plate 13 Plate 14 Colour Supplement 502 Plate 15 Plate 16 Colour Supplement 503 Plate 17 Plate 18 Plate 19 Colour Supplement 504 Plate 20 Plate 21 Plate 22 Colour Supplement 505 Plate 23 Plate 25 Plate 24 Colour Supplement 506 Plate 26 Plate 27 Plate 28 Colour Supplement 507 Plate 29 Colour Supplement 508 Plate 30 Colour Supplement 509 Plate 31 Plate 32 Colour Supplement 510 Plate 33 Plate 34 [...]... great circles, AB, BC and C A The corresponding central angles are c, a, and b Hannu Karttunen et al (Eds.), Spherical Astronomy In: Hannu Karttunen et al (Eds.), Fundamental Astronomy, 5th Edition pp 11–45 (2007) DOI: 11685739_2 © Springer-Verlag Berlin Heidelberg 2007 2 Spherical Astronomy 12 angles correspond to each other in a unique way, it is customary to give the central angles instead of the... anthropocentric conceptions to the modern view of a vast universe where man and the Earth play an insignificant role Astronomy has taught us the real scale of the nature surrounding us Modern astronomy is fundamental science, motivated mainly by man’s curiosity, his wish to know more about Nature and the Universe Astronomy has a central role in forming a scientific view of the world “A scientific view of the world”... thus has a central position in almost all branches of astronomy (Table 1.1) Astronomy can be divided into different areas according to the wavelength used in observations We can Fig 1.5 The globular cluster M13 There are over a million stars in the cluster (Photo Palomar Observatory) 1 Introduction 8 Table 1.1 The share of different branches of astronomy in 1980, 1998 and 2005 For the first two years,... research Branch of Astronomy Astronomical instruments and techniques Positional astronomy, celestial mechanics Space research Theoretical astrophysics Sun Earth Planetary system Interstellar matter, nebulae Radio sources, X-ray sources, cosmic rays Stellar systems, Galaxy, extragalactic objects, cosmology Fig 1.6 The Large Magellanic Cloud, our nearest neighbour galaxy (Photo National Optical Astronomy Observatories,... constellation of Cygnus The brightest star on the right is α Cygni or Deneb (Photo M Poutanen and H Virtanen) Hannu Karttunen et al (Eds.), Introduction In: Hannu Karttunen et al (Eds.), Fundamental Astronomy, 5th Edition pp 3–9 (2007) DOI: 11685739_1 © Springer-Verlag Berlin Heidelberg 2007 1 Introduction 4 on the locations of the celestial bodies Thus time reckoning became more and more accurate,... Objects of Research 5 1.2 Astronomical Objects of Research Modern astronomy explores the whole Universe and its different forms of matter and energy Astronomers study the contents of the Universe from the level of elementary particles and molecules (with masses of 10−30 kg) to the largest superclusters of galaxies (with masses of 1050 kg) Astronomy can be divided into different branches in several ways... habilis, appeared The most distant objects known, the quasars, are so far away that their radiation, seen on the Earth now, was emitted long before the Sun or the Earth were born 11 2 Spherical Astronomy S pherical astronomy is a science studying astronomical coordinate frames, directions and apparent motions of celestial objects, determination of position from astronomical observations, observational... the rapid development of seafaring, when voyages extended farther and farther from home ports, position determination presented a problem for which astronomy offered a practical solution Solving these problems of navigation were the most important tasks of astronomy in the 17th and 18th centuries, when the first precise tables on the movements of the planets and on other celestial phenomena were published... Introduction 8 Table 1.1 The share of different branches of astronomy in 1980, 1998 and 2005 For the first two years, the percantage of the number of publications was estimated from the printed pages of Astronomy and Astrophysics Abstracts, published by the Astronomische Rechen-Institut, Heidelberg The publication of the series was discontinued in 2000, and for 2005, an estimate was made from the Smithsonian/NASA... masses of 1050 kg) Astronomy can be divided into different branches in several ways The division can be made according to either the methods or the objects of research The Earth (Fig 1.3) is of interest to astronomy for many reasons Nearly all observations must be made through the atmosphere, and the phenomena of the upper atmosphere and magnetosphere reflect the state of interplanetary space The Earth is