Explore Modern Astronomy and Its Connections to Our Lives

The Cosmic Perspective provides a thoroughly engaging and up-to-date introduction to astronomy for anyone who is curious about the universe. As respected teachers and active researchers, the authors present astronomy using a coherent narrative and a thematic approach that engages students immediately and guides them through connecting ideas. The Ninth Edition features major scientific updates, new content that focuses on the possibility of life in the universe and recent discoveries, and an enhanced focus on cultural diversity among scientists and ethics across science and astronomy. Mastering Astronomy includes a wealth of author-created resources for students to use before, during, and after class.

Ninth Edition

THE COSMIC PERSPECTIVE Bennett Donahue Schneider Voit

A01_BENN4364_09_SE_FM.indd 7 01/12/18 2:09 AM Fully Updated Science Engages Students

Chapter 11 has been updated with the ­latest discoveries from the Juno and Cassini ­ missions, as well as new understanding of ­Jupiter’s weather, ­Saturn’s rings, and more.

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Other updates include new material on the detection of gravitational waves (Chapters S3 and 18), new insights into extrasolar planets (Chapter 13), new discoveries about early life on Earth (Chapter 24), and much more.

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A01_BENN4364_09_SE_FM.indd 8 01/12/18 2:09 AM Revised End-of-Chapter Exercises Deepen Student Understanding

NEW! Each chapter now has Inclusive Astronomy exercises designed to spur student ­discussion about topics such as why ­astronomy belongs to everyone and the ways in which the astronomical community is ­working to address historical inequities.

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The Process of Science, a major theme integrated throughout the main text, is reinforced with a set of short-answer questions at the end of each chapter, as well as a suite of tutorials available for assignment in Mastering Astronomy.

See the newly reorganized end-of-chapter exercise sets for additional problem types designed to help your students review key concepts, check their understanding, and learn to think critically. All exercises are also assignable through Mastering Astronomy.

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A01_BENN4364_09_SE_FM.indd 9 01/12/18 2:09 AM Mastering Astronomy’s Study Area Helps Students Come Prepared to Class . . .

The Study Area features self-study Reading, Concept, and Visual quizzes for each chapter, many videos and interactive figures, a set of self-guided tutorials covering key concepts, a media workbook, World Wide Telescope tours, and much more — PLUS access to a full etext of The Cosmic Perspective.

NEW! Nearly 100 new videos about key concepts and figures in the text, all written and most narrated by the authors to ensure consistency of terminology and pedagogy. Most videos include embedded pause-and-predict questions that allow students to check their understanding as they watch. Students can use these videos to help prepare for lectures, while instructors will find the same videos with assignable tutorials in the instructor-accessible Item Library.

A01_BENN4364_09_SE_FM.indd 10 01/12/18 2:09 AM . . . While Instructors Can Access a Large Title Library of Homework and Test Questions

The Item Library features more than 250 assignable tutorials—all written or co-written by the textbook authors— including new tutorials based on all of the videos and interactive figures as well as updated tutorials on key concepts, process of science, vocabulary, and much more.

Many of the assignable tutorials use ranking or sorting tasks, which research shows to be particularly effective in building conceptual understanding.

The Item Library also includes all end- of-chapter exercises from the book, individual questions from the three self- study quizzes (Reading, Concept, and Visual) for each chapter, and a large test bank.

A01_BENN4364_09_SE_FM.indd 11 01/12/18 2:09 AM Reach Every Student with Pearson eText

Pearson eText, optimized for mobile, seamlessly integrates videos and other rich media with the text and gives students access to their textbook anytime, anywhere.

A01_BENN4364_09_SE_FM.indd 12 01/12/18 2:09 AM Engage Students Before and During Class with Dynamic Study Modules and Learning Catalytics

NEW! Dynamic Study ­Modules in ­Mastering ­Astronomy help students study ­effectively—and at their own pace—by ­keeping them motivated and engaged. The ­assignable modules rely on the ­latest research in cognitive science, ­using ­methods—such as ­adaptivity, ­gamification, and ­intermittent rewards—to stimulate learning and improve retention.

With Learning Catalytics, you’ll hear from every student when it matters most. You pose a variety of questions that help students recall ideas, apply concepts, and develop critical-thinking skills. Your students respond using their own smartphones, tablets, or laptops. You can monitor responses with real-time analytics and find out what your students do—and don’t—understand. Then you can adjust your teaching accordingly, and even facilitate peer-to-peer learning, helping students stay motivated and engaged.

A01_BENN4364_09_SE_FM.indd 13 01/12/18 2:09 AM Instructor Support You Can Rely on

The Cosmic Perspective includes a full suite of instructor support materials in the Instructor Resources area in Mastering Astronomy. Resources include lecture presentations, images, reading quizzes, and clicker questions in PowerPoint; labeled and unlabeled JPEGs of all images from the text; an instructor’s guide for each chapter; and a test bank.

A01_BENN4364_09_SE_FM.indd 14 01/12/18 2:09 AM Preface

e humans have gazed into the sky for countless ■■ Chapter 5 has a new Common Misconception box generations. We have wondered how our lives are on “Light Paths, Lasers, and Shadows.” Wconnected to the Sun, Moon, planets, and stars that ■■ In Chapter 6, we have made three significant adorn the heavens. Today, through the science of astronomy, updates: a focus on major new and planned obser- we know that these connections go far deeper than our vatories, including the James Webb Space Telescope; ancestors ever imagined. This book tells the story of modern a new subsection on the role of “big data” in astron- astronomy and the new perspective, The Cosmic Perspective, omy, using LSST as an example; and an expanded that astronomy gives us on ourselves and our planet. discussion of multi-messenger astronomy, such as the gravitational-wave observatory LIGO. ■■ Chapter 9 has numerous scientific updates based Who Is This Book For? on recent planetary missions, especially in Section The Cosmic Perspective provides a comprehensive survey 9.4 on Mars, where we discuss how recent evidence of modern astronomy suitable for anyone who is curi- from the Curiosity rover is providing a new view of ous about the universe, regardless of prior background in past periods of liquid water on Mars. We also dis- astronomy or physics. However, it is designed primarily cuss recent reanalysis of the cause of dark streaks to serve as a textbook for college courses in introductory and gullies on crater walls. astronomy. The Cosmic Perspective contains enough mate- ■■ Chapter 10 has similar updates for new data, rial for a full-year introductory astronomy sequence but including the addition of a new Learning Goal in can be flexibly used for shorter courses as well. Section 10.4 on Mars, to reflect a deeper discussion Instructors of shorter courses may also wish to consider of the history of the Martian climate. Section 10.6 on several available variations of this textbook. We offer two global warming has also been significantly updated, volumes containing selected chapters from this book: The with greater emphasis on expected consequences of Solar System, which consists of Chapters 1–14 (including the warming. S1) and 24, and Stars, Galaxies, and Cosmology, which ■■ In Chapter 11, we have revamped the discussion of consists of Chapters 1–6 (including S1), S2–S4, and 14–24. Jupiter’s weather to include new results from the Those teaching one-term general survey courses may wish Juno mission. We have also made important scien- to consider The Essential Cosmic Perspective, which covers tific updates to the information on Saturn’s moons a smaller set of topics and is tailored to meet the needs and rings based on results from the final stages of of comprehensive one-term survey courses in astronomy, the Cassini mission. and The Cosmic Perspective Fundamentals, which is even ■■ Chapter 12 includes updated data and images from shorter and covers only the most fundamental topics in the Dawn, Rosetta, and New Horizons missions, astronomy. All of these options are also available with along with discussion of the possibility of an undis- MasteringTM Astronomy. covered “Planet 9” and a new Special Topic box on ’Oumuamua, the first confirmed object with origin beyond our solar system to pass through our solar New to This Edition system. ■■ Chapter 13 covers the fast-evolving topic of extra- The underlying philosophy, goals, and structure of The solar planets and hence has numerous scientific Cosmic Perspective remain the same as in past editions, but updates and new figures. we have thoroughly updated the text and made a number ■■ In Chapter S3, we have rewritten the section on of other improvements. Here, briefly, is a list of the signifi- gravitational waves to include their recent direct cant changes you’ll find in the ninth edition: detection. ■■ Major Chapter-Level Changes: We have made numer- ■■ Chapter 14 includes new discussion and a new ous significant changes to both update the science and figure about the Sun’s influence on Earth’s climate, improve the pedagogical flow in this edition. The full and how we can rule out a changing Sun as a cause list is too long to put here, but major changes include of recent global warming. the following: ■■ In Chapter 18, we have almost completely rewrit- ■■ In Chapter 2, we have reworked the section on ten Section 18.4—changing from the two learning eclipses with a new set of art pieces and revised goals in the prior edition to three learning goals—to pedagogy to reflect the fact that many students include the detection of gravitational waves from heard about or witnessed the 2017 eclipse. neutron star and black hole mergers.

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A01_BENN4364_09_SE_FM.indd 20 01/12/18 2:09 AM ■■ Chapters 20 and 21 have been updated in light of students are prepared before class and to those using new research on galactic evolution, some of which “flipped classroom” strategies. is based on the work of two of the authors of this book (Donahue and Voit). Chapter 20 also incorpo- rates updates in describing the cosmic distance scale, including honoring Henrietta Levitt by referring­ to The Pedagogical Approach her period-luminosity relation as Leavitt’s law. of The Cosmic Perspective ■■ In Chapter 24, the first section has significant The Cosmic Perspective offers a broad survey of modern changes to incorporate newly discovered evidence understanding of the cosmos and of how we have built for early life on Earth. The second section has been that understanding. Such a survey can be presented in a reworked to update the discussion of searching for number of different ways. We have chosen to build The life on Mars, and its second learning goal has been Cosmic Perspective around a set of key themes designed to reworked to cover more than just the moons of Jupi- engage student interest and a set of pedagogical principles ter and Saturn. designed to ensure that all material comes across as clearly ■■ Fully Updated Science: Astronomy is a fast-moving as possible to students. field, and numerous new developments have occurred since the prior edition was published. In addition to Themes the major chapter-level changes described above, we Most students enrolled in introductory astronomy courses have made many other scientific updates to reflect the have little connection to astronomy when their course latest results from both ground-based and space-based begins, and many have little understanding of how science observatories and from spacecraft missions within the actually works. The success of these students therefore solar system. depends on getting them engaged in the subject mat- ■■ Revamped Exercise Sets: We have reorganized the ter. To help achieve this, we have chosen to focus on the end-of-chapter exercise sets in order to place greater ­following five themes, which are interwoven throughout emphasis on questions designed to promote discussion the book. and group work. ■■ New Feature—Inclusive Astronomy: The astronomi- Theme 1: We are a part of the universe and can therefore cal community is engaged in broad and wide-ranging learn about our origins by studying the universe. This is conversations about inclusion and the persistent lack of the overarching theme of The Cosmic Perspective, as we diversity in the fields of astronomy and other sciences. continually emphasize that learning about the universe To provide sample openings for discussions of inclu- helps us understand ourselves. Studying the intimate sion in the classroom, we have (1) added a new set of connections between human life and the cosmos gives exercises in every chapter under the heading “Inclusive students a reason to care about astronomy and also Astronomy,” written to initiate student discussions deepens their appreciation of the unique and fragile about topics centered on inclusiveness in astronomy; nature of our planet and its life. (2) added a similar set of additional exercises that you Theme 2: The universe is comprehensible through scientific can find in the set of Group Activities available in the principles that anyone can understand. The universe is Study Area of Mastering Astronomy; and (3) replaced comprehensible because the same physical laws appear many of the chapter-opening epigraphs in order to to be at work in every aspect, on every scale, and in include a more diverse group of individuals. every age of the universe. Moreover, while professional ■■ New Content in Mastering Astronomy: The Cosmic scientists generally have discovered the laws, anyone can Perspective is much more than a textbook; it is a com- understand their fundamental features. Students can learn plete “learning package” that combines the textbook enough in one or two terms of astronomy to comprehend with deeply integrated, interactive media developed the basic reasons for many phenomena that they see to support every chapter of our book. We continu- around them—phenomena ranging from seasonal changes ally update the material on the Mastering Astronomy and phases of the Moon to the most esoteric astronomical website, and for this edition we call your attention images that appear in the news. to nearly 100 new “prelecture videos,” all written by (and most narrated by) the authors, designed to help Theme 3: Science is not a body of facts but rather a students understand key concepts. Students can watch process through which we seek to understand the world the videos at any time in the Study Area, while instruc- around us. Many students assume that science is just a tors can find assignable tutorials based on the videos laundry list of facts. The long history of astronomy can in the instructor-accessible Item Library. In addition to show them that science is a process through which we the new videos and their corresponding tutorials, you learn about our universe—a process that is not always will find many other new tutorials in the Item Library, a straight line to the truth. That is why our ideas about as well as a fully updated set of reading, concept, and the cosmos sometimes change as we learn more, as they visual quizzes for each chapter, available in both the did dramatically when we first recognized that Earth is Study Area and the assignable Item Library. These a planet going around the Sun rather than the center of resources should be especially valuable to instructors the universe. In this book, we continually emphasize the who wish to offer assignments designed to ensure that nature of science so that students can understand how

PREFACE xxi

A01_BENN4364_09_SE_FM.indd 21 01/12/18 2:09 AM and why modern theories have gained acceptance and are going. We therefore begin the book (Chapter 1) why these theories may change in the future. with a broad overview of modern understanding of the cosmos, so that students know what they will be study- Theme 4: Astronomy belongs to everyone. Astronomy has ing in the rest of the book. We maintain this “context played a significant role throughout history in virtually first” approach throughout the book by always telling every culture, and the modern science of astronomy owes ­students what they will be learning, and why, before a debt to these early and largely unsung astronomers. diving into the details. We therefore strive throughout the book to make sure ■■ Make the material relevant. It’s human nature to be that students understand that astronomical knowledge more interested in subjects that seem relevant to our belongs to everyone, that people of all backgrounds have lives. Fortunately, astronomy is filled with ideas that made and continue to make contributions to astronomical touch each of us personally. For example, the study understanding, and that everyone should have the of our solar system helps us better understand and opportunity to study astronomy. Moreover, we seek to appreciate our planet Earth, and the study of stars and motivate students enough to ensure that they will remain galaxies helps us learn how we have come to exist. By engaged in the ongoing human adventure of astronomical emphasizing our personal connections to the cosmos, discovery throughout their lives, no matter whether they we make the material more meaningful, inspiring stu- choose to do that only by following the news media or by dents to put in the effort necessary to learn it. entering careers relating to astronomy. ■■ Emphasize conceptual understanding over “stamp Theme 5: Astronomy affects each of us personally with the ­collecting” of facts. If we are not careful, astronomy can new perspectives it offers. We all conduct the daily business appear to be an overwhelming collection of facts that of our lives with reference to some “world view”—a are easily forgotten when the course ends. We therefore set of personal beliefs about our place and purpose emphasize a few key conceptual ideas, which we use in the universe, which we have developed through a over and over again. For example, the laws of conserva- combination of schooling, religious training, and personal tion of energy and conservation of angular momentum thought. This world view shapes our beliefs and many (introduced in Section 4.3) reappear throughout the of our actions. Although astronomy does not mandate a book, and the wide variety of features found on the particular set of beliefs, it does provide perspectives on terrestrial planets are described in terms of just a few the architecture of the universe that can influence how basic geological processes. Research shows that, long we view ourselves and our world, and these perspectives after the course is over, students are far more likely to can potentially affect our behavior. For example, someone retain such conceptual learning than individual facts who believes Earth to be at the center of the universe or details. might treat our planet quite differently from someone who ■■ Proceed from the more familiar and concrete to the less views it as a tiny and fragile world in the vast cosmos. In familiar and abstract. It’s well known that children many respects, the role of astronomy in shaping world learn best by starting with concrete ideas and then views may represent the deepest connection between the generalizing to abstractions later. The same is true for universe and the everyday lives of humans. many adults. We therefore always try to “build bridges to the familiar”— that is, to begin with concrete or Pedagogical Principles familiar ideas and then gradually draw more general No matter how an astronomy course is taught, it is very principles from them. important to present material according to well-established ■■ Use plain language. Surveys have found that the num- pedagogical principles. The following list briefly sum- ber of new terms in many introductory astronomy books marizes the major pedagogical principles that we apply is larger than the number of words taught in many throughout this book.* first-year courses on a foreign language. In essence, this means the books are teaching astronomy in what looks ■■ Stay focused on the big picture. Astronomy is filled with to students like a foreign language! Clearly, it is much interesting facts and details, but they are meaningless easier for students to understand key astronomical unless they fit into a big-picture view of the universe. concepts if they are explained in plain English without We therefore take care to stay focused on the big resorting to unnecessary jargon. We have gone to great ­picture (essentially the themes discussed above) at all lengths to eliminate jargon or, at minimum, to replace times. A major benefit of this approach is that although standard jargon with terms that are easier to remember students may forget individual facts and details after in the context of the subject matter. the course is over, the big-picture framework should ■■ Recognize and address student misconceptions. stay with them for life. ­Students do not arrive as blank slates. Most students ■■ Always provide context first. We all learn new mate- enter our courses not only lacking the knowledge we rial more easily when we understand why we are hope to teach but also holding misconceptions about learning it. In essence, this is simply the idea that it is astronomical ideas. Therefore, to teach correct ideas, easier to get somewhere when you know where you we must help students recognize the paradoxes in their prior misconceptions. We address this issue in a *More detail on these pedagogical principles can be found in the Instructor Guide and in the book On Teaching Science by Jeffrey Bennett (Big Kid ­number of ways, the most obvious being the ­presence Science, 2014). of many Common Misconceptions boxes. These

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A01_BENN4364_09_SE_FM.indd 22 01/12/18 2:09 AM ­summarize commonly held misconceptions and explain Part II: Key Concepts for Astronomy (Chapters 4–6) why they cannot be correct. Guiding Philosophy: Connect the physics of the cosmos to everyday experiences.

COSMIC The Organizational Structure of Context PART II The Universality of Physics

OneOne of ofIsaac Isaac Newton’s Newton’s great great insights insights was was thatthat physics physics is universal—theis universal—the same same physical physical lawslaws govern govern both both the the motions motions of ofheavenly heavenly objectsobjects and and the the things things we we experience experience in in everydayeveryday life. life. This This illustration illustration shows shows some some of ofthe the key key physical physical principles principles used used in thein the The Cosmic Perspective studystudy of ofastronomy, astronomy, with with examples examples of ofhow how theythey apply apply both both on on Earth Earth and and in space.in space. EXAMPLESEXAMPLES ON ON EARTH EARTH EXAMPLESEXAMPLES IN IN SPACE SPACE

1 1 ConservationConservation of ofEnergy: Energy: Energy Energy PlantsPlants transform transform the the A contractingA contracting gas gas cloud cloud in space in space heats heats up becauseup because cancan be betransferred transferred from from one one object object to to energyenergy of sunlight of sunlight it transformsit transforms gravitational gravitational potential potential energy energy into into anotheranother or transformedor transformed from from one one type type to to intointo food food containing containing thermalthermal energy. energy. The Cosmic Perspective is organized into seven broad topi- chemicalchemical potential potential another,another, but but the the total total amount amount of energyof energy is alwaysis always conserved conserved [Section [Section 4.3]. 4.3]. energy,energy, which which our our kinetickinetic energy energy bodiesbodies can can convert convert intointo energy energy of of cal areas (the seven parts in the table of contents), each motion.motion. radiativeradiative energy energy potentialpotential energy energy

2 2 ConservationConservation of ofAngular Angular Momentum: Momentum: ConservationConservation of angular of angular momentum momentum v v ConservationConservation of angular of angular momentum momentum also also explains explains An Anobject’s object’s angular angular momentum momentum cannot cannot explainsexplains why why a skater a skater spins spins faster faster whywhy a planet’s a planet’s orbital orbital speed speed increases increases when when it is it is corresponding to a set of chapters along with related con- changechange unless unless it transfers it transfers angular angular as heas pullshe pulls in his in hisarms. arms. closercloser to the to theSun. Sun. momentummomentum to anotherto another object. object. Because Because r r r r angularangular momentum momentum depends depends on onthe the productproduct of mass,of mass, velocity, velocity, and and radius, radius, SunSun a spinninga spinning object object must must spin spin faster faster as asit it v v shrinksshrinks in sizein size and and an anorbiting orbiting object object mustmust move move faster faster when when its itsorbital orbital tent in Mastering Astronomy. Note that the above themes distancedistance is smalleris smaller [Section [Section 4.3]. 4.3].

TheThe force force of gravity of gravity between between a ball a ball and and GravityGravity also also operates operates in space—its in space—its attractive attractive force force 3 3 Gravity:Gravity: Every Every mass mass in thein the universe universe EarthEarth attracts attracts both both together, together, explaining explaining cancan act actacross across great great distances distances to pull to pull objects objects closer closer attractsattracts every every other other mass mass through through the the M1M1 M1M12M2 M2M2 whywhy the theball ball accelerates accelerates as itas falls. it falls. F F = G = G togethertogether or to or hold to hold them them in orbit. in orbit. forceforce called called gravity. gravity. The The strength strength of of g g d 2d 2 and pedagogical principles are woven into this structure at gravitygravity between between two two objects objects depends depends on onthe the product product of theof the masses masses divided divided by bythe the square square of theof the distance distance between between every level. themthem [Section [Section 4.4]. 4.4]. d d

15,00015,000 K starK star 4 4 ThermalThermal Radiation: Radiation: Large Large objects objects The The glow glow you you see see from from 108108 SunlightSunlight is also is also a visible a visible form form of thermal of thermal radiation. radiation. emitemit a thermal a thermal radiation radiation spectrum spectrum that that a hota hotfireplace fireplace poker poker is is thethe Sun Sun (5800 (5800 K) K) TheThe Sun Sun is much is much brighter brighter and and whiter whiter than than a fireplace a fireplace 6 6 dependsdepends on onthe the object’s object’s temperature. temperature. thermalthermal radiation radiation in the in the 1010 pokerpoker because because its surfaceits surface is much is much hotter. hotter. formform of visible of visible light. light. 30003000 K starK star HotterHotter objects objects emit emit photons photons with with a a 4 4 higherhigher average average energy energy and and emit emit 1010 radiationradiation of greaterof greater intensity intensity at allat all 2 2 wavelengthswavelengths [Section [Section 5.4]. 5.4]. 1010 visible light visible light

ve intensity per relati ve intensity per relati ve intensity 0 0

square meter of surface meter square 10 of surface meter square 10 101101 102102 103103 104104 105105 wavelengthwavelength (nm) (nm) Part Structure ultravioletultravioletinfraredinfrared 5 5 ElectromagneticElectromagnetic Spectrum: Spectrum: Light Light is is WeWe encounter encounter many many different different ManyMany different different forms forms of of a wavea wave that that affects affects electrically electrically charged charged kindskinds of electromagnetic of electromagnetic electromagneticelectromagnetic radiation radiation are are particlesparticles and and magnets. magnets. The The wavelength wavelength lightlight radiationradiation in our in oureveryday everyday lives. lives. microwavemicrowave black black hole hole SunSun cosmiccosmic microwave microwave presentpresent in space. in space. We We therefore therefore andand frequency frequency of lightof light waves waves range range over over x-rayx-ray machines machines bulbbulb ovenoven accretionaccretion disk disk backgroundbackground needneed to observe to observe light light of many of many a widea wide spectrum, spectrum, consisting consisting of gammaof gamma differentdifferent wavelengths wavelengths to get to geta a The seven parts of The Cosmic Perspective each approach rays,rays, x-rays, x-rays, ultraviolet ultraviolet light, light, visible visible light, light, completecomplete picture picture of the of theuniverse. universe. infraredinfrared light, light, and and radio radio waves. waves. Visible Visible lightlight is onlyis only a small a small fraction fraction of theof the entire entire spectrumspectrum [Section [Section 5.2]. 5.2]. gammagamma rays rays x-raysx-rays ultravioletultraviolet infraredinfrared radioradio gammagamma rays rays x-raysx-rays ultravioletultraviolet infraredinfrared radioradio visiblevisible microwavesmicrowaves visiblevisible microwavesmicrowaves

their set of chapters in a distinctive way designed to help CHAPTER 6 TElESCOPES 189 maintain the focus on the five themes discussed ear- M06_BENN4364_09_SE_C06.indd 188 12/10/2018 21:25 M06_BENN4364_09_SE_C06.indd 189 12/10/2018 21:25 lier. Here, we summarize the philosophy and content of The Cosmic Context figure for Part II appears on each part. Note that each part concludes with a two-page pp. 188–189. Cosmic Context spread designed to tie the part content These chapters lay the groundwork for understanding together into a coherent whole. astronomy through what is sometimes called the “universal- ity of physics”—the idea that a few key principles governing Part I: Developing Perspective (Chapters 1–3, S1) matter, energy, light, and motion explain both the phenom- ena of our daily lives and the mysteries of the cosmos. Each Guiding Philosophy: Introduce the big picture, the process of chapter begins with a section on science in everyday life in science, and the historical context of astronomy. which we remind students how much they already know

COSMIC Context PART I Our Expanding Perspective about scientific phenomena from their everyday experi-

OurOur perspective perspective on onthe the universe universe has has changed changed dramatically dramatically throughout throughout humanhuman history. history. This This timeline timeline summarizes summarizes some some of theof the key key discoveries discoveries thatthat have have shaped shaped our our modern modern perspective. perspective. ences. We then build on this everyday knowledge to help students learn the formal principles of physics needed for the rest of their study of astronomy. Chapter 4 covers the

StonehengeStonehenge Earth-centeredEarth-centered model model of the of theuniverse universe Galileo’sGalileo’s telescope telescope YerkesYerkes Observatory Observatory EdwinEdwin Hubble Hubble at the at theMt. Mt.Wilson Wilson telescope telescope HubbleHubble Space Space Telescope Telescope laws of motion, the crucial conservation laws of angular 6 25006 2500 B.C. B.C. 400400 B.C. B.C. –170 –170 A.D. A.D. 1543–16481543–1648 A.D. A.D. 1838–19201838–1920 A.D. A.D. 1924–19291924–1929 A.D. A.D. 19901990 A.D. –presentA.D.–present

1 1AncientAncient civilizations civilizations recognized recognized patterns patterns 2 2TheThe ancient ancient Greeks Greeks tried tried to explain to explain 3 3CopernicusCopernicus suggested suggested that that Earth Earth is a is a 4 4LargerLarger telescopes telescopes and and photography photography 5 5EdwinEdwin Hubble Hubble measured measured the thedistances distances 6 6ImprovedImproved measurements measurements of galactic of galactic in thein themotion motion of the of theSun, Sun, Moon, Moon, observedobserved motions motions of the of theSun, Sun, Moon, Moon, planetplanet orbiting orbiting the theSun. Sun. The The Sun-centered Sun-centered mademade it possible it possible to measure to measure the the of galaxies,of galaxies, showing showing that that they they lay layfar far distancesdistances and and the therate rate of expansion of expansion planets,planets, and and stars stars through through our oursky. sky. They They andand planets planets using using a model a model with with Earth Earth at at modelmodel explained explained apparent apparent retrograde retrograde parallaxparallax of stars, of stars, offering offering direct direct proof proof beyondbeyond the thebounds bounds of the of theMilky Milky Way Way havehave shown shown that that the theuniverse universe is about is about momentum and energy, and the universal law of gravita- alsoalso noticed noticed connections connections between between what what the thecenter, center, surrounded surrounded by spheresby spheres in in motionmotion simply, simply, though though it made it made thatthat Earth Earth really really does does orbit orbit the theSun Sun and and andand proving proving that that the theuniverse universe is far is far 14 billion14 billion years years old. old. These These measurements measurements theythey saw saw in the in thesky skyand and our ourlives lives on on the theheavens. heavens. The The model model explained explained accurateaccurate predictions predictions only only after after Kepler Kepler showingshowing that that even even the thenearest nearest stars stars are are largerlarger than than our ourown own galaxy. galaxy. He Healso also havehave also also revealed revealed still-unexplained still-unexplained Earth,Earth, such such as theas thecycles cycles of seasons of seasons manymany phenomena phenomena well, well, but butcould could discovereddiscovered his histhree three laws laws of planetary of planetary light-yearslight-years away. away. We Welearned learned that that our our discovereddiscovered that that more more distant distant galaxies galaxies surprises,surprises, including including evidence evidence for forthe the andand of tides of tides [Section [Section 3.1]. 3.1]. explainexplain the theapparent apparent retrograde retrograde motion motion motion.motion. Galileo’s Galileo’s telescopic telescopic SunSun is a is fairly a fairly ordinary ordinary star star in the in theMilky Milky are aremoving moving away away from from us faster,us faster, telling telling existenceexistence of mysterious of mysterious “dark “dark matter” matter” of theof theplanets planets only only with with the theaddition addition of of observationsobservations confirmed confirmed the the WayWay [Sections [Sections 2.4, 2.4, 15.1]. 15.1]. us thatus that the theentire entire universe universe is expanding is expanding andand “dark “dark energy” energy” [Sections [Sections 1.3, 1.3, manymany complex complex features—and features—and even even Sun-centeredSun-centered model, model, and and revealed revealed that that andand suggesting suggesting that that it began it began in an in eventan event 23.1].23.1]. then,then, its predictionsits predictions were were not notespecially especially the theuniverse universe contains contains far morefar more stars stars we wecall callthe theBig BigBang Bang [Sections [Sections 1.3, 1.3, tion. Chapter 5 deals with the nature of light and matter, accurateaccurate [Section [Section 3.2]. 3.2]. thanthan had had been been previously previously imagined imagined 20.2].20.2]. [Section[Section 3.3]. 3.3]. DistancesDistances between between stars stars are enormous.are enormous. At a Atscale a scale of 1 ofto 110 to billion, 10 billion, you canyou holdcan hold the the Sun Sunin your in your hand, hand, but thebut nearestthe nearest stars stars are thousandsare thousands of kilometers of kilometers away. away. the formation of spectra, and the Doppler effect. Chapter E E

W W 6 covers telescopes and astronomical observing techniques. Earth’sEarth’s rotation rotation around around its axis its axisleads leads to the to dailythe daily The Thetilt of tilt Earth’s of Earth’s east-to-westeast-to-west motions motions of objects of objects in the in sky.the sky. rotationrotation axis axisleads leads to seasonsto seasons as Earth as Earth orbitsorbits the Sun.the Sun.

PlanetsPlanets are muchare much smaller smaller than than the Sun.the Sun. At a Atscale a scale of 1 ofto 110 to billion, 10 billion, the Sunthe Sunis the is sizethe size of a ofgrapefruit, a grapefruit, Earth Earth is the is sizethe sizeof a ofball a ballpoint point of a ofpen, a pen, and andthe distancethe distance between between themthem is about is about 15 meters. 15 meters. Part III: Learning from Other Worlds (Chapters 7–13) Guiding Philosophy: We learn about our own world and Our solarOur solar system system is located is located about about 27,000 27,000 light-years light-years from from The TheMilky Milky Way Way Galaxy Galaxy contains contains over over The Theobservable observable universe universe contains contains over over 100 100billion billion the centerthe center of the of Milkythe Milky Way Way Galaxy. Galaxy. 100 100billion billion stars. stars. galaxies.galaxies. existence by studying about other planets in our solar sys-

M03B_BENN4364_09_SE_C03B.indd 108 12/10/2018 20:44 M03B_BENN4364_09_SE_C03B.indd 109 12/10/2018 20:44 tem and beyond. The Cosmic Context figure for Part I appears on pp. 108–109. Note: Part III is essentially independent of Parts IV through VII and can be covered either before or after them. The basic goal of these chapters is to give students a big-

picture overview and context for the rest of the book, as COSMIC Context PART III Learning from Other Worlds

ComparingComparing the the worlds worlds in inthe the solar solar system system has has taught taught us us important important 2 2 JovianJovian planets planets are are gas-rich gas-rich and and far farmore more massive massive OurOur Moon Moon led ledus tous to well as to help them develop an appreciation for the pro- lessonslessons about about Earth Earth and and why why it isit sois so suitable suitable for for life. life. This This illustra illustra- - thanthan Earth. Earth. They They and and their their ice-rich ice-rich expectexpect all smallall small objects objects tiontion summarizes summarizes some some of ofthe the major major lessons lessons we’ve we’ve learned learned by by moonsmoons have have opened opened our our eyes eyes to to to beto geologicallybe geologically studyingstudying other other worlds worlds both both in inour our own own solar solar system system and and beyond beyond it. it. thethe diversity diversity of processesof processes that that deaddead c c shapeshape worlds worlds [Chapter [Chapter 11]. 11]. EarthEarth and and the the Moon Moon 1 1 ComparingComparing the the terrestrial terrestrial worlds worlds shows shows that that a planet’s a planet’s size size and and distance distance cess of science and how science has developed through fromfrom the the Sun Sun are are the the primary primary factors factors that that determine determine how how it evolves it evolves through through timetime [Chapters [Chapters 9, 10].9, 10].

VenusVenus demonstrates demonstrates the theimportance importance of distance of distance from from the theSun: Sun: If Earth If Earth were were moved moved to the to theorbit orbit TheThe strong strong gravity gravity of the of the ccbut butEuropa—along Europa—along of Venus,of Venus, it would it would suffer suffer a runaway a runaway greenhouse greenhouse effect effect and and become become too toohot hotfor forlife. life. jovianjovian planets planets has has shaped shaped withwith Io, Titan,Io, Titan, and and other other history. Chapter 1 outlines our modern understanding of the theasteroid asteroid and and Kuiper Kuiper moons—provedmoons—proved that that belts,belts, and and flung flung comets comets tidaltidal heating heating or icy or icy intointo the thedistant distant Oort Oort cloud, cloud, JupiterJupiter and and Europa Europa compositioncomposition can can lead lead ultimatelyultimately determining determining to geologicalto geological activity, activity, howhow frequently frequently asteroids asteroids in somein some cases cases with with andand comets comets strike strike Earth. Earth. subsurfacesubsurface oceans oceans and and perhapsperhaps even even life. life. the cosmos, including the scale of space and time, so that MarsMars shows shows why why size size is important: is important: A planetA planet smaller smaller than than Earth Earth loses loses interiorinterior heat heat faster, faster, which which can can lead lead to ato decline a decline in geological in geological activity activity andand loss loss of atmospheric of atmospheric gas. gas. students gain perspective on the entire universe before TheThe smallest smallest terrestrial terrestrial worlds, worlds, MercuryMercury and and the theMoon, Moon, became became CometsComets or water-rich or water-rich geologicallygeologically dead dead long long ago. ago. asteroidsasteroids from from the theouter outer 3 3 TheyThey therefore therefore retain retain ancient ancient AsteroidsAsteroids and and comets comets may may be besmall small asteroidasteroid belt belt brought brought impactimpact craters, craters, which which provide provide bodiesbodies in thein the solar solar system, system, but but they they EarthEarth the theingredients ingredients a recorda record of how of how impacts impacts must must havehave played played major major roles roles in thein the of itsof oceansits oceans and and havehave affected affected Earth Earth and and developmentdevelopment of lifeof life on onEarth Earth atmosphere.atmosphere. diving into its details. Chapter 2 introduces basic sky phe- otherother worlds. worlds. [Chapter[Chapter 12]. 12].

ImpactsImpacts of comets of comets and and asteroidsasteroids have have altered altered nomena, including seasons and phases of the Moon, and the thecourse course of life of lifeon on EarthEarth and and may may do sodo so again.again. provides perspective on how phenomena we experience every day are tied to the broader cosmos. Chapter 3 dis-

4 4 TheThe discovery discovery of planetsof planets around around other other stars stars hashas shown shown that that planetary planetary systems systems are are common.common. Studies Studies of otherof other solar solar systems systems are are teachingteaching us usnew new lessons lessons about about how how planets planets cusses the nature of science, offering a historical perspec- formform and and about about the the likelihood likelihood of findingof finding other other Earth-likeEarth-like worlds worlds [Chapter [Chapter 13]. 13].

RapidRapid advances advances in extrasolar in extrasolar planet planet detectiondetection have have allowed allowed us tous find to find some some planetsplanets as smallas small as Earth,as Earth, with with some some of of tive on the development of science and giving students thesethese planets planets orbiting orbiting within within the the habitablehabitable zones zones of their of their stars. stars. perspective on how science works and how it differs from 400 PART III LEARNING FROM OTHER WORLDS CHAPTER 13 OTHER PLANETARy SySTEMS 401 nonscience. The supplementary (optional) Chapter S1 goes into more detail about the sky, including celestial time- TheM13A_BENN4364_09_SE_C13.indd Cosmic 400 Context figure30/09/2018 for 05:32 M13A_BENN4364_09_SE_C13.indd Part 401 III appears on 30/09/2018 05:32 keeping and navigation. pp. 400–401.

PREFACE xxiii

A01_BENN4364_09_SE_FM.indd 23 01/12/18 2:09 AM This set of chapters begins in Chapter 7 with a broad over- relativity and quantum mechanics makes it possible to gain view of the solar system, including an 11-page tour that a much deeper appreciation of many of the most important highlights some of the most important and interesting and interesting topics in modern astronomy, including black features of the Sun and each of the planets in our solar holes, gravitational lensing, and the overall geometry of the system. In the remaining chapters of this part, we seek to universe. The three chapters of Part IV cover special relativ- explain these features through a true comparative plane- ity (Chapter S2), general relativity (Chapter S3), and key tology approach, in which the discussion emphasizes the astronomical ideas of quantum mechanics (Chapter S4). processes that shape the planets rather than the “stamp col- The main thrust throughout is to demystify relativity and lecting” of facts about them. Chapter 8 uses the concrete quantum mechanics by convincing students that they are features of the solar system presented in Chapter 7 to build capable of understanding the key ideas despite the reputa- student understanding of the current theory of solar sys- tion of these subjects for being hard or counterintuitive. tem formation. Chapters 9 and 10 focus on the terrestrial planets, covering key ideas of geology and atmospheres, Part V: Stars (Chapters 14–18) respectively. In both chapters, we start with examples from Guiding Philosophy: We are intimately connected to the stars. our own planet Earth to help students understand the COSMIC types of features that are found throughout the terrestrial Context PART V Balancing Pressure and Gravity

WeWe can can understand understand the the entire entire life life cycle cycle of of a a star star in in terms terms of of 33 TThehe balance balance tips tips in in favor favor of of 44 BalanceBalance between between thermal thermal 55 GravityGravity again again gains gains the the 66 InIn high-mass high-mass stars, stars, core core 77 AtAt the the end end of of a astar’s star’s life, life, thethe changing changing balance balance between between pressure pressure and and gravity. gravity. This This gravitygravity after after the the core core runs runs pressurepressure and and gravity gravity is is upperupper hand hand over over pressure pressure contractioncontraction continues, continues, eithereither degeneracy degeneracy pressure pressure illustrationillustration shows shows how how that that balance balance changes changes over over time time outout of of hydrogen. hydrogen. Fusion Fusion of of restoredrestored when when the the core core afterafter the the core core helium helium is is leadingleading to to multiple multiple shell shell hashas come come into into permanent permanent andand why why those those changes changes depend depend on on a a star’s star’s birth birth mass. mass. hydrogenhydrogen into into helium helium temperaturetemperature rises rises enough enough gone.gone. Just Just as as before, before, fusionfusion that that terminates terminates balancebalance with with gravity gravity or or the the worlds and the fundamental­ processes that explain how temporarilytemporarily stops stops supplying supplying forfor helium helium fusion fusion into into fusionfusion stops stops replacing replacing the the withwith iron iron and and a asupernova supernova starstar has has become become a ablack black (Stars(Stars not not to to scale.) scale.) thermalthermal energy energy in in the the core. core. carbon,carbon, which which can can once once thermalthermal energy energy leaving leaving the the explosionexplosion [Section [Section 17.3]. 17.3]. hole.hole. The The nature nature of of the the end end TheThe core core again again contracts contracts and and moremore replace replace the the thermal thermal core.core. The The core core therefore therefore statestate depends depends on on the the mass mass KeyKey heatsheats up. up. Hydrogen Hydrogen fusion fusion energyenergy radiated radiated from from the the resumesresumes contracting contracting and and ofof the the remaining remaining core core 22 beginsbegins in in a ashell shell around around the the corecore [Section [Section 17.2]. 17.2]. heatingheating up, up, and and helium helium [Chapter[Chapter 18]. 18]. pressurepressure ThermalThermal pressure pressure comes comes into into steady steady balance balance with with gravitygravity when when the the core core becomes becomes hot hot enough enough for for core.core. The The outer outer layers layers expand expand fusionfusion begins begins in in a ashell shell MultipleMultiple shel shell–fusionl–fusion star star BlackBlack hole hole these features came to be. We then complete each of these gravitygravity hydrogenhydrogen fusion fusion to to replace replace the the thermal thermal energy energy andand cool, cool, and and the the star star becomes becomes aroundaround the the carbon carbon core core thethe star star radiates radiates from from its its surface surface [Section [Section 14.1]. 14.1]. redderredder [Section [Section 17.2]. 17.2]. [Section[Section 17.2]. 17.2].

HydrogenHydrogen shell-fusion shell-fusion star star HeliumHelium cor coree-fusion-fusion star star DoubleDouble shel shell–fusionl–fusion star star DegeneracyDegeneracy pressure pressure cannot cannot PressurePressure balances balances balancebalance gravity gravity in in a ablack black hole. hole. gravitygravity at at every every chapters by summarizing how the various processes have pointpoint within within a a HIGHIGHH-MASS-MASS Main-sequenceMain-sequence main-sequencemain-sequence star. star. starstar

NeutronNeutron star star ( M(M 6 6 3 M3MSunSun) ) played out on each individual world. Chapter 11 covers the 77 0.08 0.08MMSunSun

NeutronNeutron degeneracy degeneracy pressure pressure 11 GravityGravity overcomes overcomes TheThe balance balance between between pressure pressure and and gravity gravity acts acts as as a athermostat thermostat to to cancan balance balance gravity gravity in in a astellar stellar pressurepressure inside inside a aprotostar, protostar, regulateregulate the the core core temperature: temperature: corpsecorpse with with less less than than about about causingcausing the the core core to to LuminosityLuminosity remains remains steady steady because because 2–32–3 M MSunSun. . jovian planets and their moons and rings. ­Chapter 12 dis- contractcontract and and heat heat up. up. heliumhelium core core fusion fusion restores restores balance. balance. AA protostar protostar cannot cannot achieve achieve A Adrop drop in in core core A Arise rise in in core core LuminosityLuminosity continually continually rises rises because because core core steadysteady balance balance between between temperaturetemperature decreases decreases temperaturetemperature increases increases contractioncontraction causes causes the the temperature temperature and and fusionfusion rate, rate, which which SolarSolar fusionfusion rate, rate, which which fusionfusion rate rate in in the the hydrogen hydrogen shell shell to to rise. rise. pressurepressure and and gravity gravity ThermostatThermostat becausebecause nuclear nuclear fusion fusion is is lowerslowers core core pressure, pressure, raisesraises core core pressure, pressure, notnot replacing replacing the the thermal thermal causingcausing the the core core to to causingcausing the the core core to to energyenergy it itradiates radiates into into contractcontract and and heat heat up. up. expandexpand and and cool cool down. down. cusses small bodies in the solar system, including aster- spacespace [Sections [Sections 16.1, 16.1, 16.2]. 16.2]. WhiteWhite dwarf dwarf ( M(M 6 6 1.4 1.4MMSunSun) ) ProtostarProtostar TheThe balancing balancing point point between between pressure pressure and and gravity gravity depends depends onon a astar’s star’s mass: mass: LOW-MASS LOW-MASS BalanceBalance between between pressure pressure and and gravity gravity in in high-mass high-mass stars stars results results in in a a higherhigher core core temperature, temperature, a ahigher higher fusion fusion rate, rate, greater greater luminosity, luminosity, and and a a oids, comets, and dwarf planets. It also covers cosmic shortershorter lifetime. lifetime. ElectronElectron degeneracy degeneracy pressure pressure ElectronElectron degeneracy degeneracy pressure pressure balancesbalances gravity gravity in in the the core core of of a a cancan balance balance gravity gravity in in a astellar stellar low-masslow-mass star star before before it itgets gets hot hot corpsecorpse of of mass mass 6 6 1.4M 1.4MSunSun. . enoughenough to to fuse fuse heavier heavier elements. elements. TheThe star star ejects ejects its its outer outer layers layers collisions, including the impact linked to the extinction of andand ends ends up up as as a awhite white dwarf. dwarf.

ContractionContraction converts converts gravitational gravitational potentialpotential energy energy into into thermal thermal energy. energy.

the dinosaurs and views on how seriously we should take luminous more luminous more

hotterhotter BalanceBalance between between pressure pressure and and gravity gravity in in low-mass low-mass stars stars results results in in a a the ongoing impact threat. Finally, Chapter 13 turns to the coolercooler core core temperature, temperature, a aslower slower fusion fusion rate, rate, less less luminosity, luminosity, and and a a DegeneracyDegeneracy pressure pressure balances balances longerlonger lifetime. lifetime. BrownBrown dwarf dwarf ( M(M 6 6 0.08 0.08MMSunSun) ) gravitygravity in in objects objects of of less less than than

0.08M0.08MSUNSUN before before their their cores cores become become hothot enough enough for for steady steady fusion. fusion. These These objectsobjects never never become become stars stars and and endend up up as as brown brown dwarfs. dwarfs. exciting topic of other planetary systems. 0.08 0.08MM 66 SunSun

DegeneracyDegeneracy pressure pressure keeps keeps a abrown brown dwarf dwarf stable stable inin size size even even as as it itcools cools steadily steadily with with time. time.

M18_BENN4364_09_SE_C18.indd 578 20/10/2018 03:37 M18_BENN4364_09_SE_C18.indd 579 20/10/2018 03:37 Part IV: A Deeper Look at Nature (Chapters S2–S4) The Cosmic Context figure for Part V appears on Guiding Philosophy: Ideas of relativity and quantum pp. 578–579. mechanics are accessible to anyone. These are our chapters on stars and stellar life cycles. Note: These chapters are labeled “supplementary” because Chapter 14 covers the Sun in depth so that it can serve coverage of them is optional. Covering them will give your as a concrete model for building an understanding of students a deeper understanding of the topics that follow other stars. Chapter 15 describes the general properties of on stars, galaxies, and cosmology, but the later chapters other stars, how we measure these properties, and how are self-contained so that they may be studied without we classify stars with the H-R diagram. Chapter 16 covers having read Part IV at all. star birth, and the rest of stellar evolution is discussed in

COSMIC Chapter 17. Chapter 18 focuses on the end points of stellar Context PART IV A Deeper Look at Nature

WeWe all all have have “common “common sense” sense” ideas ideas about about the the meaning meaning of of space, space, time, time, matter, matter, and and energy, energy, andand in in most most cases cases these these common-sense common-sense ideas ideas serve serve us us quite quite well. well. But But when when we we look look more more evolution: white dwarfs, neutron stars, and black holes. closely,closely, we we find find that that our our everyday everyday ideas ideas cannot cannot explain explain all all that that we we observe observe in in nature. nature. The The theoriestheories of of relativity relativity and and quantum quantum mechanics mechanics have have given given us us a a deeper deeper understanding understanding of of thethe nature nature of of space, space, time, time, matter, matter, and and energy—an energy—an understanding understanding that that now now underlies underlies almostalmost all all of of our our modern modern understanding understanding of of the the universe. universe.

11 TimeTime Dilation: Dilation: Einstein’s Einstein’s theory theory of of relativity relativity is is based based on on two two simple simple principles: principles: (1) (1) the the laws laws of of nature nature are are thethe same same for for everyone, everyone, and and (2) (2) the the speed speed of of light light is is the the same same for for everyone. everyone. One One implication implication of of these these 33 CurvatureCurvature of of Spacetime: Spacetime: Special Special relativity relativity tells tells us us that that space space and and time time are are inextricably inextricably linked linked as as principlesprinciples is is that that the the passage passage of of time time is is relative—time relative—time can can run run at at different different speeds speeds for for different different observers. observers. four-dimensionalfour-dimensional spacetime, spacetime, and and general general relativity relativity tells tells us us that that gravity gravity arises arises from from curvature curvature of of ManyMany observations observations have have confirmed confirmed this this mind-boggling mind-boggling prediction prediction of of relativity, relativity, and and astronomers astronomers must must spacetime.spacetime. Astronomical Astronomical observations, observations, both both in in our our solar solar system system and and beyond, beyond, have have confirmed confirmed accountaccount for for it itwhen when studying studying the the universe universe [Chapter [Chapter S2]. S2]. Einstein’sEinstein’s predictions predictions about about the the structure structure of of space space and and time time [Chapter [Chapter S3, S3, Section Section 23.2]. 23.2]. Jackie’sJackie’s point point of of view view CurvatureCurvature of of spacetime spacetime precisely precisely SpacetimeSpacetime curvature curvature also also explains explains the the bending bending of of light light known known as as gravitational gravitational lensing. lensing. TheThe gravity gravity of of the the galaxy galaxy at at the the Part VI: Galaxies and Beyond (Chapters 19–23) explainsexplains the the precession precession of of Mercury's Mercury's centercenter of of this this image image bends bends the the ellipticalelliptical orbit orbit around around the the Sun. Sun. lightlight from from a asingle single object object behind behind youyou AsAs you you move move by by Jackie Jackie at at 0.7c, 0.7c, she she sends sends a a it itc c lightlight beam beam from from the the bottom bottom of of her her ship ship to to the the imageimage 1 1 realreal object object imageimage 2 2 toptop and and back back again again c c 0.0.77cc Guiding Philosophy: Present galaxy evolution and cosmol- lightlight from from distantdistant object object

JackieJackie massivemassive ccandand measures measures the the time time it ittakes takes light light to to makemake the the trip. trip. SunSun objectobject ogy together as intimately related topics.

MercuryMercury toto Earth Earth YourYour point point of of view view ccproducingproducing four four distinct distinct images images ofof the the object. object.

AccordingAccording to to relativity, relativity, you you see see light light moving moving at at the the exact exact same same youyou speed,speed, but but it ittraces traces a alonger longer path path from from your your point point of of view view COSMIC 44 BlackBlack Holes: Holes: Relativity Relativity predicts predicts that that there there can can be be objects objects whose whose gravity gravity is is so so strong strong that that nothing nothing can can becausebecause of of Jackie’s Jackie’s motion motion cc escapeescape from from inside inside them— them— not not even even light. light. Observations Observations of of these these black black holes holes help help us us test test the the most most Context PART VI extremeextreme predictions predictions of of relativity relativity [Sections [Sections S3.3, S3.3, 18.3, 18.3, 19.4]. 19.4]. Galaxy Evolution

AllAll galaxies, galaxies, including including our our Milky Milky Way, Way, developed developed as as 44 WithinWithin this this large-scale large-scale web, web, galaxy galaxy formation formation began began when when gravity gravity collected collected Stars Stars that that form form in in the the disk disk hydrogenhydrogen and and helium helium gas gas into into blobby blobby protogalactic protogalactic clouds clouds [Section [Section 19.3]. 19.3]. orbitorbit in in orderly orderly circles. circles. 16001600 AU AU gravitygravity pulled pulled together together matter matter in in regions regions of of the the universe universe 380,000380,000 years years thatthat started started out out slightly slightly denser denser than than surrounding surrounding regions. regions. 0.2"0.2" JackieJackie TheThe central central illustration illustration depicts depicts how how galaxies galaxies formed formed over over time,time, starting starting from from the the Big Big Bang Bang in in the the upper upper left left and and 11 billion billion years years 0.0.77cc ccandand a alonger longer path path at at the the proceedingproceeding to to the the present present day day in in the the lower lower right, right, as as samesame speed speed means means that that you you spacespace gradually gradually expanded expanded according according to to Hubble’s Hubble’s law. law. measuremeasure a alonger longer time. time. TheThe gas gas settled settled into into a aspinning spinning disk disk while while BigBig Bang Bang SpiralSpiral galaxies galaxies probably probably formed formed through through mergers mergers of of starsstars that that had had already already formed formed remained remained in in YourYour conclusion: conclusion: Time Time is is running running slower slower on on Jackie’s Jackie’s ship ship than than on on yours! yours! smallersmaller protogalactic protogalactic clouds. clouds. thethe halo. halo. PhotoPhoto of of spiral spiral galaxy galaxy NGC NGC 4414 4414

1414 billion billion years years (present(present day) day) 22 MatterMatter and and Antimatter: Antimatter: Relativity Relativity tells tells us us that that mass mass and and energy energy are are equivalent: equivalent: E E = = mc mc2.2 This. This formula formula explainsexplains how how small small amounts amounts of of matter matter can can release release huge huge amounts amounts of of energy, energy, and and how how matter-antimatter matter-antimatter eventevent horizon horizon particleparticle pairs pairs can can be be produced produced from from pure pure energy. energy. Pair Pair production production has has been been observed observed countless countless times times in in Earth-basedEarth-based particle particle accelerators accelerators and and is is crucial crucial to to our our models models of of the the early early universe universe [Sections [Sections S4.2, S4.2, 22.1]. 22.1]. blackblack hole hole blackblack hole hole 55 AtAt least least some some elliptical elliptical galaxies galaxies 11 DramaticDramatic inflation inflation early early in in time time is is thought thought formedformed when when two two spiral spiral galaxies galaxies electronelectron toto have have produced produced large-scale large-scale ripples ripples collidedcollided and and merged merged [Section [Section 21.2]. 21.2]. SqueezingSqueezing a astar star down down to to the the size size of of a asmall small city city would would make make the the curvature curvature of of inin the the density density of of the the universe. universe. All All the the AllAll the the matter matter in in the the universe universe was was spacetimespacetime (gravity) (gravity) around around it itso so extreme extreme that that the the star star would would turn turn into into a ablack black TIMETIME 1995–20171995–2017 structurestructure we we see see today today formed formed as as gamma-raygamma-ray createdcreated by by pair pair production production under under hole.hole. gravitygravity drew drew additional additional matter matter into into the the photonsphotons thethe extremely extremely energetic energetic peakspeaks of of these these ripples ripples [Section [Section 22.3]. 22.3]. conditionsconditions of of the the Big Big Bang. Bang. TheThe orbits orbits of of stars stars at at the the center center of of the the Milky Milky Way Way Galaxy Galaxy indicate indicate that that it itcontains contains a ablack black hole hole about about 4 4million million times times as as massive massive as as our our Sun. Sun. antielectronantielectron

PhotoPhoto of of elliptical elliptical galaxy galaxy M87 M87 AA collision collision disrupts disrupts the the AfterAfter the the starburst, starburst, spacespace orderlyorderly orbits orbits of of stars stars almostalmost no no cold cold gas gas is is left left inin the the disks disks of of spiral spiral forfor star star formation. formation. 22 ObservationsObservations of of the the cosmic cosmic microwave microwave galaxiesgalaxies and and triggers triggers InflationInflation may may have have stretched stretched backgroundbackground show show us us what what the the regions regions a astarburst. starburst. tinytiny quantum quantum fluctuations fluctuations ofof enhanced enhanced density density were were like like about about 380,000380,000 years years after after the the Big Big Bang Bang M13D_BENN4364_09_SE_C13D.indd 466 27/10/2018 15:40 M13D_BENN4364_09_SE_C13D.indd 467 27/10/2018 15:40 intointo large-scale large-scale ripples. ripples. [Section[Section 22.2]. 22.2].

66 DarkDark matter matter is is thought thought The Cosmic Context figure for Part IV appears on toto drive drive galaxy galaxy formation. formation. MeasurementsMeasurements indicate indicate TheThe gravity gravity of of dark dark a alarge large amount amount of of mattermatter seems seems to to be be invisibleinvisible dark dark matter matter spacespace whatwhat pulled pulled gas gas into into surroundssurrounds the the visible visible starsstars in in each each galaxy. galaxy. 33 LargLarge-scalee-scale su surveysrveys of of the the universe universe protogalacticprotogalactic clouds. clouds. showshow that that gravity gravity has has gradually gradually shaped shaped It Itcontinues continues to to cause cause earlyearly regions regions of of enhanced enhanced density density into into galaxiesgalaxies to to cluster cluster and and pp. 466–467. sometimessometimes to to collide collide a aweb-like web-like structure, structure, with with galaxies galaxies arrangedarranged in in huge huge chains chains and and sheets sheets [Section[Section 23.3]. 23.3]. ImageImage from from Planck Planck VariationsVariations in in the the cosmic cosmic [Section[Section 23.3]. 23.3]. microwavemicrowave background background showshow that that regions regions of of thethe universe universe differed differed in in 77 Today,Today, in in the the disks disks of of spiral spiral densitydensity by by only only a afew few galaxiesgalaxies like like the the Milky Milky Way, Way, the the partsparts in in 100,000. 100,000. star–gas–starstar–gas–star cycle cycle continues continues to to produceproduce new new stars stars and and planets planets fromfrom matter matter that that was was once once in in Nearly all students have at least heard of things like the protogalacticprotogalactic clouds clouds [Section [Section 19.2]. 19.2].

prohibition on faster-than-light travel, curvature of space- SloanSloan Digital Digital Sky Sky Survey Survey TheThe web-like web-like patterns patterns of of structure structure observed observed NewNew stars stars and and planetary planetary systems— systems— inin large-scale large-scale galaxy galaxy surveys surveys agree agree with with those those somesome perhaps perhaps much much like like our our own—are own—are seenseen in in large-scale large-scale computer computer simulations simulations of of currentlycurrently forming forming in in the the Orion Orion Nebula, Nebula, structurestructure formation. formation. 15001500 light-years light-years from from Earth. Earth. time, and the uncertainty principle. But few (if any) stu- PhotoPhoto of of Orion Orion Nebula Nebula 696 PART VI GALAXIES AND BEYOND CHAPTER 23 DArk MAttEr, DArk ENErGY, AND thE FAtE OF thE UNIvErSE 697 dents enter an introductory astronomy course with any idea M23_BENN4364_09_SE_C23.indd 696 13/10/2018 16:29 M23_BENN4364_09_SE_C23.indd 697 13/10/2018 16:29 of what these things mean, and they are naturally curious The Cosmic Context figure for Part VI appears on about them. Moreover, a basic understanding of the ideas of pp. 696–697.

xxiv PREFACE

A01_BENN4364_09_SE_FM.indd 24 01/12/18 2:09 AM These chapters cover galaxies and cosmology. Chapter 19 material. Each section begins with a short introduction presents the Milky Way as a paradigm for galaxies in much that leads into a set of learning goals relevant to the the same way that Chapter 14 uses the Sun as a paradigm section—the same learning goals listed at the begin- for stars. Chapter 20 describes the properties of galaxies ning of the chapter. and shows how the quest to measure galactic distances ■■ The Big Picture: Every chapter narrative ends with this led to Hubble’s law and laid the foundation for modern feature, designed to help students put what they have cosmology. Chapter 21 discusses how the current state of learned in the chapter into the context of the overall knowledge regarding galaxy evolution has emerged from goal of gaining a broader perspective on ourselves, our our ability to look back through time. Chapter 22 then planet, and prospects for life beyond Earth. The final presents the Big Bang theory and the evidence supporting entry in this section is always entitled “My Cosmic Per- it, setting the stage for Chapter 23, which explores dark spective”; it aims to help students see a personal con- matter and its role in galaxy formation, as well as dark nection between themselves and the chapter content, energy and its implications for the fate of the universe. with the goal of encouraging them to think more criti- cally about the meaning of all that they learn in their Part VII: Life on Earth and Beyond (Chapter 24) astronomy course. Guiding Philosophy: The study of life on Earth helps us ■■ Chapter Summary: The end-of-chapter summary offers understand the search for life in the universe. a concise review of the learning goal questions, help- ing to reinforce student understanding of key concepts

COSMIC Context PART VII A Universe of Life? from the chapter. Thumbnail figures are included to

ThroughoutThroughout this this book, book, we we have have seen seen that that the the history history of of thethe universe universe has has proceeded proceeded in in a a way way that that has has made made our our existenceexistence on on Earth Earth possible. possible. This This figure figure summarizes summarizes some some remind students of key illustrations and photos in the ofof the the key key ideas, ideas, and and leads leads us us to to ask: ask: If If life life arose arose here, here, shouldn’tshouldn’t it it also also have have arisen arisen on on many many other other worlds? worlds? We We do do notnot yet yet know know the the answer, answer, but but scientists scientists are are actively actively seeking seeking 44 55 toto learn learn whether whether life life is is rare rare or or common common in in the the universe. universe. OurOur planet planet and and all all the the life life OurOur galaxy galaxy is is large large enough enough onon it itis is made made primarily primarily of of toto retain retain the the elements elements elementselements formed formed by by ejectedejected by by supernovae, supernovae, nuclearnuclear fusion fusion in in high-mass high-mass andand it itrecycles recycles them them into into chapter. starsstars and and dispersed dispersed into into newnew stars stars and and planetary planetary 33 TheThe attractive attractive force force of of spacespace by by supernovae supernovae systemssystems [Section [Section 19.2]. 19.2]. 66 PlanetsPlanets can can form form in in gravitygravity pulls pulls together together [Section[Section 17.3]. 17.3]. gaseousgaseous disks disks of of material material thethe matter matter that that makes makes aroundaround newly newly formed formed 2828 galaxies,galaxies, stars, stars, and and 1616OO SiSi stars.stars. Earth Earth was was built built from from ■■ planetsplanets [Section [Section 4.4]. 4.4]. 5656 heavyheavy elements elements that that 3131SS FeFe End-of-Chapter Exercises: Each chapter includes 22 RipplesRipples in in the the density density of of (26(26p,p, 30n) 30n) condensedcondensed from from the the gas gas 77 LifeLife as as we we know know it itrequires requires (16p,(16p, 15n) 15n) asas particles particles of of metal metal and and thethe early early universe universe were were MMMM liquidliquid water, water, so so we we define define MM1 1 1 1 2 2 MM2 2 rock,rock, which which then then gradually gradually necessarynecessary for for life life to to form form FFg g = = G G 2 2 thethe habitable habitable zone zone around around laterlater on. on. Without Without those those dd accretedaccreted to to become become our our a astar star to to be be the the zone zone in in ripples,ripples, matter matter would would planetplanet [Section [Section 8.2]. 8.2]. whichwhich a asuitably suitably large large dd 11 TheThe protons, protons, neutrons, neutrons, and and nevernever have have collected collected into into planetplanet can can have have liquid liquid 88 EarlyEarly life life has has had had the the time time galaxies,galaxies, stars, stars, and and 1616 2828 an extensive set of exercises that can be used for study, electronselectrons in in the the atoms atoms that that OO SiSi waterwater on on its its surface surface neededneeded to to evolve evolve into into makemake up up Earth Earth and and life life planetsplanets [Section [Section 22.3]. 22.3]. [Section[Section 24.3]. 24.3]. complexcomplex forms—including forms—including werewere created created out out of of pure pure us—becauseus—because the the solar solar EveryEvery piece piece of of matter matter in in the the universe universe High-massHigh-mass stars stars have have cores cores hot hot enough enough energyenergy during during the the first first few few thermostatthermostat has has kept kept the the Sun Sun pullspulls on on every every other other piece. piece. toto make make elements elements heavier heavier than than carbon. carbon. momentsmoments after after the the Big Big shiningshining steadily steadily for for billions billions aratrhth o orbrbi i Bang,Bang, leaving leaving the the universe universe NewNew elements elements mix mix with with the the interstellar interstellar EE t t ofof years years [Section [Section 14.2]. 14.2]. filledfilled with with hydrogen hydrogen and and medium,medium, which which then then forms forms new new stars stars discussion, or assignment. All of the end-of-chapter heliumhelium gas gas [Section [Section 22.1]. 22.1]. andand planets. planets. TerrestrialTerrestrial planets planets formed formed in in warm,warm, inner inner regions regions of of the the solar solar SunSun nebula;nebula; jovian jovian planets planets formed formed in in electronelectron cooler,cooler, outer outer regions. regions. HH abab nene gamma-raygamma-ray WeWe observe observe the the seeds seeds of of structure structure itaitbablel ez ozo SolarSolar ThermostatThermostat photonsphotons formationformation in in the the cosmic cosmic microwave microwave exercises are organized into the following subsets: antielectronantielectron background.background. TheThe Sun’s Sun’s habitable habitable zone zone (green) (green) MatterMatter can can be be created created from from energy: energy: occupiesoccupies a aregion region from from beyond beyond the the orbit orbit E E = = m mc 2c.2. ofof Venus Venus to to near near the the orbit orbit of of Mars. Mars. ■■ TheThe solar solar thermostat thermostat keeps keeps the the Sun’s Sun’s Visual Skills Check: This set of questions is fusionfusion rate rate stable. stable. designed to help students build their skills at inter- preting the many types of visual information used in astronomy. ■■ Chapter Review Questions: These questions are ones that students should be able to answer from the reading alone. M24_BENN4364_09_SE_C24.indd 728 09/10/2018 15:16 M24_BENN4364_09_SE_C24.indd 729 09/10/2018 15:16 The Cosmic Context figure for Part VII appears on ■■ Does It Make Sense? (or similar title): Each of these pp. 728–729. short statements is to be critically evaluated by This part consists of a single chapter. It may be consid- students, to explain why it does or does not make ered optional, to be used as time allows. Those who wish sense. These exercises are generally easy once stu- to teach a more detailed course on astrobiology may wish dents understand a particular concept, but difficult to consider the text Life in the Universe, by Bennett and otherwise; this makes these questions an excellent Shostak. probe of comprehension. ■■ Quick Quiz: The short multiple-choice quiz allows students to check their basic understanding. Note Chapter Structure that, for further self-testing, every chapter also has a Each chapter is carefully structured to ensure that students Reading, Concept, and Visual quiz available on the understand the goals up front, learn the details, and pull Mastering Astronomy website. all the ideas together at the end. Note the following key ■■ Inclusive Astronomy: These questions are designed structural elements of each chapter: to stimulate discussion about participation in sci- ence, and in particular about the ideas that (1) ■■ Chapter Learning Goals: Each chapter opens with a astronomy belongs to everyone; (2) all cultures have page offering an enticing image and a brief overview made contributions to astronomical understanding; of the chapter, including a list of the section titles and (3) opportunities for women and minorities have associated learning goals. The learning goals are pre- historically been limited; and (4) the scientific com- sented as key questions designed to help students both munity can take active steps to provide more equi- to understand what they will be learning about and to table opportunities for the future. stay focused on these key goals as they work through ■■ Process of Science Questions: These questions, the chapter. which can be used for discussion or essays, are ■■ Introduction and Epigraph: The main chapter text intended to help students think about how science begins with a one- to three-paragraph introduction to progresses over time. This set always concludes with the chapter material and an inspirational quotation rel- an activity designed for group work, in order to pro- evant to the chapter. mote collaborative learning in class. ■■ Section Structure: Chapters are divided into numbered ■■ Investigate Further: The remaining questions are sections, each addressing one key aspect of the chapter designed for home assignment and are intended

PREFACE xxv

A01_BENN4364_09_SE_FM.indd 25 01/12/18 2:09 AM to go beyond the earlier review questions. These ­relevant to the topic at hand. Tutorial assessments questions are separated into two groups: Short- based on these videos are available for assignment in Answer/Essay questions, which focus on conceptual the instructor Item Library. interpretation and sometimes on outside research ■■ Cross-References: When a concept is covered in or experiment, and Quantitative Problems, which greater detail elsewhere in the book, a cross-reference require some mathematics and are usually based on to the relevant section is included in brackets topics covered in the Mathematical Insight boxes. (e.g., [Section 5.2]). ■■ Glossary: A detailed glossary makes it easy for students to look up important terms. Additional Pedagogical Features ■■ Appendixes: The appendixes contain a number of You’ll find a number of other features designed to increase useful references and tables, including key constants student understanding, both within individual chapters (Appendix A), key formulas (Appendix B), key math- and at the end of the book, including the following: ematical skills (Appendix C), and numerous data tables ■■ Think About It: This feature, which appears through- and star charts (Appendixes D–I). out the book in the form of short questions integrated into the narrative, gives students the opportunity to Mastering Astronomy reflect on important new concepts. It also serves as an What is the single most important factor in student success excellent starting point for classroom discussions. in astronomy? Both research and common sense reveal the ■■ See It for Yourself: This feature also occurs throughout same answer: study time. No matter how good the teacher the book, integrated into the narrative; it gives stu- or how good the textbook, students learn only when they dents the opportunity to conduct simple observations spend adequate time learning and studying on their own. or experiments that will help them understand key Unfortunately, limitations on resources for grading have concepts. prevented most instructors from assigning much homework ■■ Common Misconceptions: These boxes address popu- despite its obvious benefits to student learning. And limita- larly held but incorrect ideas related to the chapter tions on help and office hours have made it difficult for stu- material. dents to make sure they use self-study time effectively. That, ■■ Special Topic Boxes: These boxes address supplemen- in a nutshell, is why we created Mastering Astronomy. For tary discussion topics related to the chapter material students, it provides adaptive learning designed to coach but not prerequisite to the continuing discussion. them individually—responding to their errors with specific, ■■ Extraordinary Claims Boxes: Carl Sagan made famous targeted feedback and giving optional hints for those who the statement “extraordinary claims require extraor- need additional guidance. For professors, ­Mastering Astron- dinary evidence.” These boxes provide students with omy provides unprecedented ability to automatically moni- examples of extraordinary claims about the universe tor and record students’ step-by-step work and evaluate the and how they were either supported or debunked as effectiveness of assignments and exams. scientists collected more evidence. Note that nearly all the content available at the Mas- ■■ Mathematical Insight Boxes: These boxes contain tering Astronomy site for The Cosmic Perspective has been most of the mathematics used in the book and can be written by the textbook authors. This means that students covered or skipped depending on the level of math- can count on consistency between the textbook and web ematics that you wish to include in your course. The resources, with both emphasizing the same concepts and Mathematical Insights use a three-step problem-solving using the same terminology and the same pedagogical strategy—Understand, Solve, and Explain—that gives approaches. This type of consistency ensures that students students a consistent and explicit structure for solving can study in the most efficient possible way. quantitative homework problems. All students registered for Mastering Astronomy receive ■■ Annotated Figures: Key figures in each chapter use full access to the Study Area, which includes three self- the research-proven technique of annotation—the study multiple-choice quizzes for each chapter; a large set placement on the figure of carefully crafted text (in of prelecture videos, narrated figures, interactive figures, blue) to guide students in interpreting graphs, follow- and math review videos; a set of interactive self-guided ing process figures, and translating between different tutorials that go into depth on topics that some students representations. find particularly challenging; a downloadable set of group ■■ Cosmic Context Two-Page Figures: These two-page activities; and much more. spreads provide visual summaries of key processes and Instructors have access to many additional resources, concepts. including a large Item Library of assignable material that ■■ Wavelength/Observatory Icons: For astronomical features more than 250 author-written tutorials, all of images, simple icons indicate whether the image is the end-of-chapter exercises, all the questions from the a photo, artist’s impression, or computer simulation; ­self-study quizzes in the Study Area, and a test bank. whether a photo came from ground-based or space- Instructors also have access to the author-written ­Instructor based observations; and the wavelength band used to Guide and teaching resources including PowerPoint®­ take the photo. ­Lecture Outlines, a complete set of high-resolution JPEGs of ■■ Video Icons: These icons point to videos available all images from the book, and PRS-enabled clicker quizzes­ in the Study Area of Mastering Astronomy that are based on the book and book-specific interactive media.

xxvi PREFACE

A01_BENN4364_09_SE_FM.indd 26 01/12/18 2:09 AM Supplements for The Cosmic Perspective The Cosmic Perspective is much more than just a textbook. It is a complete package of teaching, learning, and assessment resources designed to help both teachers and students. In addition to Mastering Astronomy (described above), the following­ supplements are available with this book:

Instructor or Student Name of Supplement Supplement Description SkyGazer 5.0 (Access code Student Based on Voyager IV, one of the world’s most popular planetarium card ISBN 0-321-76518-5, Supplement ­programs, SkyGazer 5.0 makes it easy for students to learn ­constellations CD ISBN 0-321-89843-2) and explore the wonders of the sky through ­interactive exercises and demonstrations. Accompanying activities are available in LoPresto’s Astronomy Media Workbook, Seventh Edition. Both ­SkyGazer and ­LoPresto’s workbook are available for download. Starry Night™ College Student Now available as an additional option with The Cosmic Perspective­ , Starry (ISBN 0-321-71295-1) Supplement Night™ College has been acclaimed as the world’s most realistic desktop planetarium software. This special­ version has an easy-to-use point-and- click interface and is available­ as an additional bundle. The Starry Night Activity Workbook, consisting of thirty-five worksheets for homework or lab, based on Starry Night Planetarium software, is available for download in the Mastering Astronomy Study Area or with a Starry Night College access code. Astronomy Active Learning Student This workbook provides fifty 20-minute in-class tutorial activities to In-Class Tutorials (ISBN Supplement choose from. Designed for use in large lecture classes, these ­activities 0-805-38296-8) by Marvin L. De are also suitable for labs. The short, structured activities are designed Jong for ­students to complete on their own or in peer-learning groups. Each ­activity targets specific learning objectives such as ­understanding ­Newton’s laws, understanding Mars’s retrograde motion, tracking stars on the H-R ­diagram, or comparing the ­properties of planets. Lecture Tutorials for Introductory Student These forty-four lecture tutorials are designed to engage students in Astronomy (ISBN 0-321-82046-0) Supplement ­critical reasoning and spark classroom discussion. by Ed Prather, Tim Slater, Jeff Adams, and Gina Brissenden Sky and Telescope Student This supplement, which includes nine articles with an assessment insert (ISBN 0-321-70620-X) Supplement covering general review, Process of Science, Scale of the Universe, and Our Place in the Universe, is available for bundling. Observation Exercises in Student This workbook includes fifteen observation activities that can be used Astronomy (ISBN 0-321- Supplement with a number of different planetarium software packages. 63812-3) by Lauren Jones Astronomy Lab: A Concept Student This modular collection of forty conceptually oriented introductory Oriented Approach (ISBN Supplement astronomy labs, housed in the Pearson Custom Library, allows for easy 0-321-86177-9) by Nate creation of a customized lab manual. McCrady and Emily Rice Instructor Resources Instructor This comprehensive collection of instructor resources includes high- (ISBN 0-135-17325-1) Supplement resolution JPEGs of all images from the book; Interactive Figures and Photos™ based on figures in the text; additional applets and ­animations to illustrate key concepts; PowerPoint® Lecture Outlines that incorporate figures, photos, checkpoint questions, and ­multimedia; and PRS-enabled clicker quizzes based on the book and book-specific interactive media, to make preparing for lectures quick and easy. These resources are located in the Mastering Astronomy Instructor Resource Area. Instructor Guide Instructor The Instructor Guide contains a detailed overview of the text, sample (ISBN 0-135-17324-4) Supplement syllabi for courses of different emphasis and duration, suggested teaching strategies, answers or discussion points for all Think About It and See It for Yourself questions in the text, solutions to all end-of-chapter problems, and a detailed reference guide summarizing media resources available for every chapter and section of the book. Test Bank Instructor Available in both Word and TestGen formats in the Instructor Resource (ISBN 0-135-17326-4) Supplement Center and Mastering Astronomy, the Test Bank contains a broad set of multiple-choice, true/false, and free-response questions for each chapter. The Test Bank is also assignable through Mastering Astronomy.

PREFACE xxvii

A01_BENN4364_09_SE_FM.indd 27 01/12/18 2:09 AM Acknowledgments Indiana University—Purdue­ University­ Fort Wayne; Man- Our textbook carries only four author names, but in fact it is fred Cuntz, University of Texas at Arlington; Charles Dan- the result of hard work by a long list of committed individu- forth, University of Colorado; Christopher De Vries, als. We could not possibly list everyone who has helped, but California State University, Stanislaus; John M. Dickey, we would like to call attention to a few people who have University of Minnesota; Mark Dickinson, National Optical played particularly important roles. First, we thank our past Astronomy Observatory; Matthias Dietrich, Worcester State and present editors at Addison-Wesley and Pearson, includ- University; Jim Dove, Metropolitan State College of Denver; ing Bill Poole, Robin Heyden, Sami Iwata, Ben Roberts, Doug Duncan, University of Colorado; Bryan Dunne, Uni- Adam Black, Nancy Whilton, and Jeanne Zalesky, along versity of Illinois, Urbana-Champaign; Suzan Edwards, with many others at Pearson who have contributed to mak- Smith College; Robert Egler, North Carolina State University ing our books possible. Special thanks to our production at Raleigh; Paul Eskridge, Minnesota State University; Dan teams, especially Sally Lifland, and our art and design team. Fabrycky, University of Chicago; David Falk, Los Angeles We’ve also been fortunate to have an outstanding group Valley College; Timothy Farris, Vanderbilt University; Harry of reviewers, whose extensive comments and suggestions Ferguson, Space Telescope Science Institute; Robert A. helped us shape the book. We thank all those who have Fesen, Dartmouth College; Tom Fleming, University of reviewed drafts of the book in various stages, including the Arizona­ ; Douglas Franklin, Western Illinois University; Sid- following individuals (listed with their affiliations at the ney Freudenstein, Metropolitan State College of Denver; time they contributed their reviews): Eric Agol, University Martin Gaskell, University of Nebraska; Richard Gelder- of Washington; Marilyn Akins, Broome Community College; man, Western Kentucky University; Harold A. Geller, George Caspar Amman, NCAR; Christopher M. Anderson, Univer- Mason University; Donna Gifford, Pima Community Col- sity of Wisconsin; John Anderson, University of North Flor- lege; Mitch Gillam, Marion L. Steele High School; Bernard ida; Peter S. Anderson, Oakland Community College; Gilroy, The Hun School of Princeton; Owen Gingerich, Har- Nahum Arav, Virginia Technical University; Phil Armitage, vard–Smithsonian (Historical Accuracy Reviewer); David University of Colorado; Keith Ashman; Thomas Ayres, Uni- Graff, U.S. Merchant Marine Academy; Richard Gray, Appa- versity of Colorado; Simon P. Balm, Santa Monica College; lachian State University; Kevin Grazier, Jet Propulsion Labo- Reba Bandyopadhyay, University of Florida; Nadine Barlow,­ ratory; Robert Greeney, Holyoke Community College; Henry Northern Arizona University; Cecilia Barnbaum, Valdosta Greenside, Duke University; Alan Greer, Gonzaga Univer- State University; John Beaver, University of Wisconsin at sity; John Griffith, Lin-Benton Community College; David Fox Valley; Peter A. Becker, George Mason University; Timo- Griffiths, Oregon State University; David Grinspoon, Plane- thy C. Beers, National Optical Astronomy Observatory; Jim tary Science Institute; John Gris, University of Delaware; Bell, Arizona State University; Priscilla J. Benson, Wellesley Bruce Gronich, University of Texas at El Paso; Thomasana College; Zach Berta-Thompson, University of Colorado; Rick Hail, Parkland University; Andrew Hamilton, University of Binzel, Massachusetts Institute of Technology; Philip Colorado; Jim Hamm, Big Bend Community College; Paul Blanco, Grossmont College; Jeff R. ­Bodart, Chipola College; Harderson, Planetary Science Institute; Charles Hartley, Howard Bond, Space Telescope Science Institute; Bernard Hartwick College; J. Hasbun, University of West Georgia; W. Bopp, University of Toledo; Sukanta Bose, Washington Joe Heafner, Catawba Valley Community College; Todd State University; David Brain, University of Colorado; David Henry, Georgia State University; David Herrick, Maysville Branch, University of Oklahoma; John C. Brandt, University Community College; Dennis Hibbert, Everett Community of New Mexico; James E. Brau, University of Oregon; Jean P. College; Scott Hildreth, Chabot College; Tracy Hodge, Berea Brodie, UCO/Lick Observatory, University of California, College; Lynnette Hoerner, Red Rocks Community College; Santa Cruz; Erik Brogt, University of Canterbury; James Mark Hollabaugh, Normandale Community College; Rich- Brooks, Florida State University; Daniel Bruton, Stephen F. ard Holland, Southern Illinois University, Carbondale; Seth Austin State University; Thomas Burbine, Moraine Valley Hornstein, University of Colorado; Joseph Howard, Salis- Community College; Debra Burris, University of Central bury University; James Christopher Hunt, Prince George’s Arkansas; Scott Calvin, Sarah Lawrence College; Amy Community College; Richard Ignace, University of Wiscon- Campbell, Louisiana State University; Humberto Campins, sin; James Imamura, University of Oregon; Douglas R. University of Central Florida; Robin Canup, Southwest Ingram, Texas Christian University; Assad Istephan, Research Institute; Eugene R. Capriotti, Michigan State Uni- Madonna University; Bruce Jakosky, University of Colorado; versity; Eric Carlson, Wake Forest University; David A. Ceb- Adam G. Jensen, University of Colorado; Dave Jewitt, Uni- ula, Pacific University; Supriya Chakrabarti, University of versity of California, Los Angeles; Adam Johnston, Weber Massachusetts, Lowell; Clark Chapman, Southwest Research State University; Lauren Jones, Gettysburg College; Kishor Institute; Kwang-Ping Cheng, California State University, T. Kapale, Western IIIinois University; William Keel, Univer- Fullerton; Dipak Chowdhury, Indiana University—Purdue sity of Alabama; Julia Kennefick, University of Arkansas; ­University Fort Wayne; Chris Churchill, New Mexico State Steve Kipp, University of Minnesota, Mankato; Kurtis Koll, University; Kelly Cline, Carroll College; Josh Colwell, Uni- Cameron University; Ichishiro Konno, University of Texas at versity of Central Florida; James Cooney, University of Cen- San Antonio; John Kormendy, University of Texas at Aus- tral Florida; Anita B. Corn, Colorado School of Mines; Philip tin; Eric Korpela, University of California, Berkeley; Arthur E. Corn, Red Rocks Community College; Kelli Corrado, Kosowsky, University of Pittsburgh; Julia Kregenow, Penn Montgomery County Community College; Peter Cottrell, State University; Kevin Krisciunas, Texas A&M; Emily University of Canterbury; John Cowan, University of Okla- Lakdawalla,­ The Planetary Society; David Lamp, Texas homa; Kevin Crosby, Carthage College; Christopher Crow, Technical University; Ted La Rosa, Kennesaw State

xxviii PREFACE

A01_BENN4364_09_SE_FM.indd 28 01/12/18 2:09 AM University; Kenneth Lanzetta, Stony Brook University; Kris- Larry Sessions, Metropolitan State College of Denver; tine Larsen, Central Connecticut State University; Ana Marie Michael Shara, American Museum of Natural History; Larson, University of Washington; Stephen Lattanzio, Anwar Shiekh, Colorado Mesa University; Seth Shostak, Orange Coast College; Chris Laws, University of Washing- SETI Institute; Ralph Siegel, Montgomery College, German- ton; Larry Lebofsky, University of Arizona; Patrick Lestrade, town Campus; Philip I. Siemens, Oregon State University; Mississippi State University; Nancy Levenson, University of Caroline Simpson, Florida International University; Paul Kentucky; Hal Levison, Southwest Research Institute; David Sipiera, William Harper Rainey College; Earl F. Skelton, M. Lind, Florida State University; Mario Livio, Space Tele- George Washington University; Evan Skillman, University of scope Science Institute; Abraham Loeb, Harvard University; Minnesota; Michael Skrutskie, University of Virginia; Mark Michael LoPresto, Henry Ford Community College; William H. Slovak, Louisiana State University; Norma Small-War- R. Luebke, Modesto Junior College; Ihor Luhach, Valencia ren, Howard University; Jessica Smay, San Jose City College; Community College; Darrell Jack MacConnell, Community Dale Smith, Bowling Green State University; Brad Snowder, College of ­Baltimore City; Marie Machacek, Massachusetts Western Washington University; Brent Sorenson, Southern Institute of Technology; Loris Magnani, University of Geor- Utah University; James R. Sowell, Georgia Technical Univer- gia; Steven Majewski, University of Virginia; J. McKim sity; Kelli Spangler, Montgomery County Community Col- Malville, University of Colorado; Geoff Marcy, University of lege; John Spencer, Southwest Research Institute; Darryl California, Berkeley; Mark Marley, Ames Research Center; Stanford, City College of San Francisco; George R. Stanley, Linda Martel, University of Hawaii; Phil Matheson, Salt San Antonio College; Bob Stein, Michigan State University; Lake Community College; John Mattox, Fayetteville State Peter Stein, Bloomsburg University of Pennsylvania; Adri- University; Marles McCurdy, Tarrant County College; Stacy ane Steinacker, University of California, Santa Cruz; Glen McGaugh, Case Western University; Kevin McLin, Univer- Stewart, University of Colorado; John Stolar, West Chester sity of Colorado; Michael Mendillo, Boston University; University; Irina Struganova, Valencia Community College; Steven­ Merriman, Moraine Valley Community College; Jack Sulentic, University of Alabama; C. Sean Sutton, Barry Metz, Delaware County Community College; William Mount Holyoke College; Beverley A. P. Taylor, Miami Uni- Millar, Grand Rapids Community College; Dinah Moche, versity; Brett Taylor, Radford University; Jeff Taylor, Univer- Queensborough Community College of City University, New sity of Hawaii; Donald M. Terndrup, Ohio State University; York; Steve Mojzsis, University of Colorado; Irina Mullins, Dave Tholen, University of Hawaii; Nick Thomas, Univer- Houston Community College–Central; Stephen Murray, Uni- sity of Bern; Frank Timmes, Arizona State University; David versity of California, Santa Cruz; Zdzislaw E. Musielak, Trott, Metro State College; David Vakil, El Camino College; University of Texas at Arlington; Charles Nelson, Drake Trina Van Ausdal, Salt Lake Community College; Dimitri University; Gerald H. Newsom, Ohio State University; Fran- Veras, Cambridge University; Licia Verde, Institute of Cos- cis Nimmo, University of California, Santa Cruz; Tyler mological Studies, Barcelona; Nicole Vogt, New Mexico Nordgren,­ University of Redlands; Lauren Novatne, Reedley State University; Darryl Walke, Rariton Valley Community College; Brian Oetiker, Sam Houston State University; Rich- College; Fred Walter, State University of New York, Stony ard Olenick, University of Dallas; John P. Oliver, University Brook; Marina Walther-Antonio, Mayo Clinic; James Webb, of Florida; Rachel Osten, Space Telescope Science Institute; Florida International University; John Weiss, Carleton Col- Stacy Palen, Weber State University; Russell L. Palma, Sam lege; Mark Whittle, University of Virginia; Paul J. Wiita, Houston State University; Bob Pappalardo, Jet Propulsion The College of New Jersey; Francis Wilkin, Union College; Laboratory; Mark Pecaut, Rockhurst University; Jon Pedi- Lisa M. Will, Mesa Community College; Jonathan Williams, cino, College of the Redwoods; Bryan Penprase, Pomona Col- University of Hawaii; Terry Willis, Chesapeake College; lege; Eric S. Perlman, Florida Institute of Technology; Peggy Grant Wilson, University of Massachusetts, Amherst; Jer- Perozzo, Mary Baldwin College; Greg Perugini, Burlington emy Wood, Hazard Community College; J. Wayne Wooten, County College; Charles Peterson, University of Missouri, Pensacola Junior College; Guy Worthey, Washington State Columbia; Cynthia W. Peterson, University of Connecticut; University, Pullman; Jason Wright, Penn State University; Jorge Piekarewicz, Florida State University; Lawrence Pin- Scott Yager, Brevard College; Don Yeomans, Jet Propulsion sky, University of Houston; Stephanie Plante, Grossmont Laboratory; Andrew Young, Casper College; Arthur Young, College; Jascha Polet, California State Polytechnic Univer- San Diego State University; Tim Young, University of North sity, Pomona; Matthew Price, Oregon State University; Har- Dakota; Min S. Yun, University of Massachusetts, Amherst; rison B. Prosper, Florida State University; Monica Ramirez, Dennis Zaritsky, University of Arizona; Robert L. Zimmer- Aims College, Colorado; Christina Reeves-Shull, Richland man, University of Oregon. College; Todd M. Rigg, City College of San Francisco; Eliza- Finally, we thank the many people who have greatly beth Roettger, DePaul University; Roy Rubins, University of influenced our outlook on education and our perspective Texas at Arlington; April Russell, Siena College; Carl Rut- on the universe over the years, including Tom Ayres, Fran ledge, East Central University; Bob Sackett, Saddleback Col- Bagenal, Forrest Boley, Robert A. Brown, George Dulk, Erica lege; Rex Saffer, Villanova University; John Safko, University Ellingson, Katy Garmany, Jeff Goldstein, David Grinspoon, of South Carolina; James A. Scarborough, Delta State Uni- Don Hunten, Joan Marsh, Catherine McCord, Dick McCray, versity; Britt Scharringhausen, Ithaca College; Ann Schmie- Dee Mook, Cherilynn Morrow, Charlie Pellerin, Carl Sagan, dekamp, Pennsylvania State University, Abington; Joslyn J. Michael Shull, John Spencer, and John Stocke. Schoemer, Denver Museum of Nature and Science; James Schombert, University of Oregon; Gregory Seab, University Jeff Bennett, Megan Donahue, of New Orleans; Bennett Seidenstein, Arundel High School; Nick Schneider, Mark Voit

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