Table Of ContentW
hether you are learning astronomy for the first time or teaching it for the tenth time,
Pathways to Astronomy offers the flexibility of exploring astronomy following the path of your
choosing. Pathways to Astronomy divides the fascinating field of astronomy into 84 units, from
which you can select topics according to your interests, while maintaining a flow of presentation.
For instructors: Pathways to Astronomy lets you customize the units to fit your course needs
and to cover the units in the order you prefer. You can select individual units to be explored
in lecture and assign other units for study. Pathways to Astronomy makes it simple for you to
apply the text material to your own particular teaching approach.
For students: Pathways to Astronomy makes it easy to grasp each topic and to clearly relate
the content from each unit to the material from lecture. The conciseness of each unit enables
you to master one topic before moving on to the next one, so you will not be overwhelmed
with too many topics being presented at once.
choose your own destination with
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Makes homework meaningful—and manageable—for instructors 8
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• Instructors can assign and grade text-specific homework within the industry’s most /0
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robust and versatile homework management system. C
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• Go to www.mhhe.com/schneider to learn more and register! A
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About the Cover E
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The cover artwork is based on images of the Earth, a solar eclipse, interstellar gas, and a
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galaxy. It illustrates ideas about the processes of formation and change, and the L
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interconnections between objects on many different scales.
Pathways to
Astronomy
Second Edition
Stephen E. Schneider
Professor of Astronomy
University of Massachusetts, Amherst
Thomas T. Arny
Professor of Astronomy, Emeritus
University of Massachusetts, Amherst
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PATHWAYS TO ASTRONOMY, SECOND EDITION
Published by McGraw-Hill, a business unit of Th e McGraw-Hill Companies, Inc., 1221 Avenue of the
Americas, New York, NY 10020. Copyright © 2009 by Th e McGraw-Hill Companies, Inc. All rights reserved.
Previous edition © 2007. No part of this publication may be reproduced or distributed in any form or by any
means, or stored in a database or retrieval system, without the prior written consent of Th e McGraw-Hill
Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, or
broadcast for distance learning.
Some ancillaries, including electronic and print components, may not be available to customers outside the
United States.
Th is book is printed on acid-free paper.
1 2 3 4 5 6 7 8 9 0 QPD/QPD 0 9 8
ISBN 978–0–07–340445–5
MHID 0–07–340445–4
Publisher: Th omas Timp
Sponsoring Editor: Debra B. Hash
Director of Development: Kristine Tibbetts
Senior Developmental Editor: Mary E. Hurley
Senior Marketing Manager: Lisa Nicks
Project Manager: April R. Southwood
Senior Production Supervisor: Sherry L. Kane
Senior Media Project Manager: Sandra M. Schnee
Designer: Tara McDermott
Cover/Interior Designer: Rokusek Design
Lead Photo Research Coordinator: Carrie K. Burger
Photo Research: Mary Reeg
Compositor: ICC Macmillan Inc.
Typeface: 10.5/12 Minion
Printer: Quebecor World Dubuque, IA
Th e credits section for this book begins on page C-1 and is considered an extension of the copyright page.
Library of Congress Cataloging-in-Publication Data
Schneider, Stephen E. (Stephen Ewing), 1957–
Pathways to astronomy / Stephen E. Schneider, Th omas T. Arny. —2nd ed.
p. cm.
Includes index.
ISBN 978–0–07–340445–5 — ISBN 0–07–340445–4 (hard copy : alk. paper) 1. Astronomy—
Textbooks. I. Arny, Th omas. II. Title.
QB43.3.S36 2009
520–dc22
2008019729
www.mhhe.com
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To my father, who taught me the night sky when I
was little.
—Steve
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ABOUT THE AUTHORS
Stephen Schneider is a professor and Thomas Arny is an emeritus professor
in the Astronomy Department at the University of Massachusetts at Amherst,
which is part of the Five College Astronomy Department (comprising faculty
from UMass, Amherst, Hampshire, Mt. Holyoke, and Smith Colleges). Both are
recipients of their college’s Outstanding Teacher Award, and they have collectively
taught introductory astronomy for over 50 years to students with a wide variety
of backgrounds.
P rofessor Schneider’s interest in astronomy began at the amateur level when
he was a child. He pursued an astronomy degree from Harvard as an under-
graduate and obtained his Ph.D. from Cornell. His dissertation work received the
Trumpler Award of the Astronomical Society of the Pacific, and he was named a
Presidential Young Investigator. He works closely with science teachers presenting
many workshops and special courses each year. He also loves to draw and paint.
Thomas T. Arny received his undergraduate degree from Haverford College
and his Ph.D. in astronomy from the University of Arizona. In addition to his
interest in astronomy, he has a long-standing fascination with the natural world:
weather (especially atmospheric optics such as rainbows), birds, wildflowers, and
butterflies.
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BRIEF CONTENTS
Preface xv Unit 21 Light, Matter, and Energy 157
Looking Up Illusrations xxv Unit 22 The Electromagnetic Spectrum 166
Unit 23 Thermal Radiation 173
Unit 24 Atomic Spectra: Identifying Atoms by Their Light 179
Unit 25 The Doppler Shift 188
PART I Unit 26 Detecting Light 191
Unit 27 Collecting Light 198
THE COSMIC LANDSCAPE 3
Unit 28 Focusing Light 203
Unit 1 Our Planetary Neighborhood 4 Unit 29 Telescope Resolution 211
Unit 2 Beyond the Solar System 13 Unit 30 The Earth’s Atmosphere and Space Observatories 217
Unit 3 Astronomical Numbers 22 Unit 31 Amateur Astronomy 226
Unit 4 Foundations of Astronomy 30
Unit 5 The Night Sky 38
Unit 6 The Year 45
Unit 7 The Time of Day 56 PART III
Unit 8 Lunar Cycles 63
THE SOLAR SYSTEM 237
Unit 9 Calendars 75
Unit 10 Geometry of the Earth, Moon, and Sun 82 Unit 32 The Structure of the Solar System 238
Unit 11 Planets: The Wandering Stars 90 Unit 33 The Origin of the Solar System 247
Unit 12 The Beginnings of Modern Astronomy 99 Unit 34 Other Planetary Systems 258
Unit 13 Observing the Sky 107 Unit 35 The Earth as a Terrestrial Planet 266
Unit 36 Earth’s Atmosphere and Hydrosphere 277
Unit 37 Our Moon 287
Unit 38 Mercury 297
PART II Unit 39 Venus 304
Unit 40 Mars 311
PROBING MATTER, LIGHT, AND
Unit 41 Asteroids 322
THEIR INTERACTIONS 119
Unit 42 Comparative Planetology 330
Unit 14 Astronomical Motion: Inertia, Mass, and Force 120 Unit 43 Jupiter and Saturn 341
Unit 15 Force, Acceleration, and Interaction 125 Unit 44 Uranus and Neptune 348
Unit 16 The Universal Law of Gravity 130 Unit 45 Satellite Systems and Rings 354
Unit 17 Measuring a Body’s Mass Using Orbital Motion 135 Unit 46 Ice Worlds, Pluto, and Beyond 364
Unit 18 Orbital and Escape Velocities 139 Unit 47 Comets 375
Unit 19 Tides 145 Unit 48 Impacts on Earth 385
Unit 20 Conservation Laws 151
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PART IV PART V
STARS AND STELLAR GALAXIES AND THE UNIVERSE 565
EVOLUTION 395
Unit 70 Discovering the Milky Way 566
Unit 49 The Sun, Our Star 396 Unit 71 Stars of the Milky Way 573
Unit 50 The Sun’s Source of Power 406 Unit 72 Gas and Dust in the Milky Way 581
Unit 51 Solar Activity 414 Unit 73 Mass and Motions in the Milky Way 590
Unit 52 Surveying the Stars 424 Unit 74 A Universe of Galaxies 599
Unit 53 Special Relativity 435 Unit 75 Types of Galaxies 608
Unit 54 Light and Distance 444 Unit 76 Galaxy Clustering 620
Unit 55 The Temperatures and Compositions of Stars 451 Unit 77 Active Galactic Nuclei 629
Unit 56 The Masses of Orbiting Stars 459 Unit 78 Dark Matter 638
Unit 57 The Sizes of Stars 464 Unit 79 Cosmology 646
Unit 58 The H-R Diagram 470 Unit 80 The Edges of the Universe 655
Unit 59 Overview of Stellar Evolution 478 Unit 81 The Beginnings of the Universe 666
Unit 60 Star Formation 486 Unit 82 The Fate of the Universe 677
Unit 61 Main-Sequence Stars 495 Unit 83 Astrobiology 687
Unit 62 Giant Stars 502 Unit 84 The Search for Life Elsewhere 696
Unit 63 Variable Stars 509
Unit 64 Mass Loss and Death of Low-Mass Stars 515
Unit 65 Exploding White Dwarfs 522
Unit 66 Old Age and Death of Massive Stars 528
Unit 67 Neutron Stars 538
Unit 68 Black Holes 545
Unit 69 Star Clusters 555
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