From the Inside Flap
Astronomy continues to enjoy a golden age of exploration and discovery. Fueled by new technologies and novel theoretical insights, the study of the cosmos has never been more exciting. We are pleased to have the opportunity to present in this book a representative sample of the known facts, evolving ideas, and frontier discoveries in astronomy today.
Astronomy: A Beginner's Guide to the Universe has been written for students who have taken no previous college science courses and who will likely not major in physics or astronomy. It is intended primarily for use in a one-semester, non-technical astronomy course. We present a broad view of astronomy, straightforwardly descriptive and without complex mathematics. The absence of sophisticated mathematics, however, in no way prevents discussion of important concepts. Rather, we rely on qualitative reasoning as well as analogies with objects and phenomena familiar to the student to explain the complexities of the subject without oversimplification. We have tried to communicate the excitement that we feel about astronomy and to awaken students to the marvelous universe around us.
We are very gratified that the first three editions of this text have been so well received by many in the astronomy education community. In using those earlier texts, many of youteachers and students alikehave given us helpful feedback and constructive criticisms. From these, we have learned to communicate better both the fundamentals and the excitement of astronomy. Many improvements inspired by your comments have been incorporated into this new edition.
ORGANIZATION AND APPROACH
As in previous editions, our organization follows the popular and effective "Earth-out" progression. We have found that most students, especially those with little scientific background, are much more comfortable studying the relatively familiar solar system before tackling stars and galaxies. Thus, Earth is the first object we discuss in detail. With Earth and Moon as our initial planetary models, we move through the solar system. Integral to our coverage of the solar system is a discussion of its formation. This line of investigation leads directly into a study of the Sun.
With the Sun as our model star, we broaden the scope of our discussion to include stars in generaltheir properties, their evolutionary histories, and their varied fates. This journey naturally leads us to coverage of the Milky Way Galaxy, which in turn serves as an introduction to our treatment of other galaxies, both normal and active. Finally, we reach the subject of cosmology and the large-scale structure and dynamics of the universe as a whole. Throughout, we strive to emphasize the dynamic nature of the cosmosvirtually every major topic, from planets to quasars, includes a discussion of how those objects formed and how they evolve.
We continue to place much of the needed physics in the early chaptersan approach derived from years of experience teaching thousands of students. Additional physical principles are developed as needed later, both in the text narrative and in the boxed Discovery and More Precisely features (describes on p. xxii). We feel strongly that this is the most economical and efficient means of presentation. However, we acknowledge that not all instructors feel the same way. Accordingly, we have made the treatment of physics, as well as the more quantitative discussions, as modular as possible, so that these topics can be deferred to later stages of an astronomy course if desired. Instructors presenting this material in a I -quarter course, who wish to (or have time to) cover only the essentials of the solar system before proceeding on to the study of stars and the rest of the universe, may want to teach only Chapter 4, and then move directly to Chapter 9 (the Sun).
NEW AND REVISED MATERIAL
Astronomy is a rapidly evolving field, and the three years since the publication of the third edition of Astronomy: A Beginner's Guide to the Universe have seen many new discoveries covering the entire spectrum of astronomical research. Almost every chapter in the fourth edition has been substantially updated with new and late-breaking information. Several chapters have also seen significant internal reorganization in order to streamline the overall presentation, strengthen our focus on the process of science, and reflect new understanding and emphases in contemporary astronomy. Among the many changes are:
- Expanded coverage throughout of the scientific method and how astronomers "know what they know."
- Updated material in Chapter 3 on adaptive optics, Subaru, Gemini, the VLT, and infrared and optical interferometry; new material on the Chandra mission; updates (and a conclusion) to the CGRO story.
- Updates in Chapter 4 on asteroid numbers and the properties of near-Earth objects; coverage of the NEAR mission and its exploration of Eros.
- Substantially updated coverage of solar system formation in Chapter 4, including disk instabilities, planetary migration, and their implications for extrasolar planetary systems.
- New section in Chapter 4 on extrasolar planets, with updated material on the latest observations.
- Expanded coverage of Pluto and new Kuiper belt objects in Chapters 4 and 8. New material in Chapter 5 on the Ozone Hole and Global Warming. Expanded material in Chapter 5 on Clementine and Lunar Prospector, with updates on their important findings, including the possibility of ice at the lunar poles.
- Greatly expanded coverage in Chapter 6 of Mars Global Surveyor and the many scientific results that have come from it; the possibility of (past or present) liquid water on Mars; an update on the Martian Meteorite controversy.
- Updates in Chapters 7 and 8 on the Galileo/GEM mission, including the latest results on the possible existence of a liquid water ocean below Europa's icy surface; discussion of the magnetic fields of the Galilean moons.
- Incorporation of results from the Yohkoh, SOHO, and TRACE missions into Chapter 9.
- The latest experimental results in the search for the missing solar neutrinos (Chapter 9).
- Use of Hipparcos data in Chapter 10 and throughout the text; a new H-R diagram based on Hipparcos measurements; discussion of future astrometry missions and their implications.
- Updated information in Chapter 10 on the numbers and mass distribution of stars in our Galaxy.
- Revision of the material on stellar mass determination in Chapter 10.
- Discussion in Chapter 11 of the Local Bubble.
- Updated information in Chapter 11 on brown dwarfs; new material on jets and outflows in star formation.
- New coverage in Chapter 12 of the end-states of stellar and binary evolution; discussion of blue stragglers; more examples of familiar stars in specific evolutionary stages.
- New section and latest results on gamma-ray bursts in Chapter 13; discussion of intermediate-mass and supermassive black holes.
- Latest results in Chapter 14 on Sgr A* and the Galaxy's central black hole.
- Reorganization of Chapter 15, combining normal and active galaxies as a single topic and expanding the discussion of black holes in galactic nuclei.
- Reorganization of Chapter 16 to focus on large-scale structure; new material on quasar absorption lines and the Lyman-alpha forest; expanded discussion of gravitational lensing, including the construction of dark-matter maps from lensing of background galaxies.
- Expanded and substantially revised coverage in Chapter 16 of galaxy collisions, hierarchical merging, and galaxy evolution; updated discussion of the measurement of Hubble's constant; revised discussion of active galaxy evolution.
- Consistent distances and times in Chapters 16 and 17, assuming a flat universe with dark matter and dark energy as determined by the WMAP satellite.
- Extensive rewriting of Chapter 17 to include recent observations of cosmic acceleration and discussion of "dark energy"; revised discussions of the cosmological constant and the age of the universe; results from the CBI and WMAP experiments suggesting a flat universe.
- Updated coverage of Europa, Mars, interstellar organic molecules, extrasolar planets, and SETI in Chapter 18.
THE ILLUSTRATION PROGRAM
Visualization plays an important role in both the teaching and the practice of astronomy, and we continue to place strong emphasis on this aspect of our book. We have tried to combine aesthetic beauty with scientific accuracy in the artist's conceptions that adorn the text, and we have sought to present the best and latest imagery of a wide range of cosmic objects. Each illustration has been carefully crafted to enhance student learning; each is pedagogically sound and tightly tied to nearby discussion of important scientific facts and ideas.
Full-Spectrum Coverage and Spectrum Icons. Increasingly, astronomers are exploiting the full range of the electromagnetic spectrum to gather information about the cosmos. Throughout this book, images taken at radio, infrared, ultraviolet, X-ray, or gamma ray wavelengths are used to supplement visible-light images. As it is sometimes difficult (even for a professional) to tell at a glance which images are visible-light photographs and which are false-color images created with other wavelengths, each photo in the text is provided with an icon that identifies the wavelength of electromagnetic radiation used to capture the image.
Explanatory Captions. Students often review a chapter by "looking at the pictures." For this reason, the captions in this book are often a bit longer and more detailed than those in other texts.
Compound Art. It is rare that a single image, be it a photograph or an artist's conception, can capture all aspects of a complex subject. Wherever possible, multiple-part figures are used in an attempt to convey the greatest amount of information in the most vivid way:
- Visible images are often presented along with their counterparts captured at other wavelengths.
- Interpretive line drawings are often superimposed on or juxtaposed with real astronomical photographs, helping students to really "see" what the photographs reveal.
- Breakouts-often multiple ones-are used to zoom in from wide-field shots to close-ups, so that detailed images can be understood in their larger context.
H-R Diagrams and Acetate Overlays. All of the book's H-R diagrams are drawn in a uniform format, using real data. In addition, a unique set of transparent acetate overlays dramatically demonstrates to students how the H-R diagram helps us to organize our information about the stars and track their evolutionary histories.
OTHER PEDAGOGICAL FEATURES
As with many other parts of our text, instructors have helped guide us toward what is most helpful for effective student learning. With their assistance, we have revised both our in-chapter and end-of-chapter pedagogical apparatus to increase its utility to students.
Learning Goals. Studies indicate that beginning students often. have trouble prioritizing textual material. For this reason, a few (typically 5 or 6) well-defined Learning Goals are provided at the start of each chapter. These help students structure their reading the chapter and then test their mastery of key facts and concepts, The Goals are numbered and cross-referenced to key sections in o body of each chapter. This in-text highlighting of the most important aspects of the chapter also helps students review. The Goals organized and phrased in such a way as to make them objectively testable, affording students a means of gauging their own progress
Concept-Links. In astronomy, as in many scientific disciplines, almost every topic seems to have some bearing on almost every other. In particular, the connection between the astronomical material and the physical principles set forth early in the text is crucial. It is important that students, when they encounter, say, Hubble's Law in Chapter 16, recall what they learned about spectral lines and the Doppler shift in Chapter 2. Similarly, the discussions of the masses of binary star components (Chapter 10) and of Galactic rotation (Chapter 14) both depend on the discussion of Kepler's and Newton's laws in Chapter 1. Throughout, discussions of new astronomical objects and concepts rely heavily on comparison with topics introduced earlier in the text.
It is important to remind students of these links so that they can recall the principles on which later discussions rest and, if necessary, review them. To this end, we have inserted "concept-links" throughout the text-symbols that mark key intellectual bridges between material in different chapters. The links, denoted by a symbol together with a section reference (and a hyperlink on the accompanying eBook), signal students that the topic under discussion is related in some significant way to ideas developed earlier, and direct them to material that they might wish to review before proceeding.
Key Terms. Like all subjects, astronomy has its own specialized vocabullry. To aid student learning, the most important astronomical terms are boldfaced at their first appearance in the text. Each boldfaced Key Term is also incorporated in the appropriate chapter summary, together with the page number where it was defined. In addition, a full alphabetical glossary, defining each Key Term and locating its first use in the text, appears at the end of the book.
More Precisely Boxes. These provide more quantitative treatments of subjects discussed qualitatively in the text. Removing these more challenging topics from the main flow of the narrative and placing them within a separate modular element of the chapter design (so that they can be covered in class, assigned as supplementary material, or simply left as optional reading for those students who find them of interest) will allow instructors greater flexibility in setting the level of their coverage.
Discovery Boxes. Exploring a wide variety of interesting supplementary topics, these features have been expanded and renamed from the "Interludes" of previous editions to better reflect their goal of providing the reader with insight into how scientific knowledge evolves, and emphasizing our theme of the process of science.
Concept Checks. We incorporate into each chapter a number of "Concept Checks"key questions that require the reader to reconsider some of the material just presented or attempt to place it into a broader context.
Chapter Summaries. The Chapter Summaries, a primary review tool for the student, have been expanded and improved for the fourth edition. All Key Terms introduced in each chapter are listed again, in context and in boldface, in these Summaries, along with page references to the text discussion.
End of Chapter Questions and Problems. Many elements of the end-of-chapter material have seen substantial reorganization:
- Each chapter now incorporates 15 Self-Test Questions, roughly equally divided between "true/false" and "fill-in-the-blank" formats, designed to allow students to assess their understanding of the chapter material. Answers to all these questions appear at the end of the book.
- Each chapter also has 15 Review and Discussion Questions, which may be used for in-class review or for assignment. As with the Self-Test Questions, the material needed to answer Review Questions may be found within the chapter. The Discussion Questions explore particular topics more deeply, often asking for opinions, not just facts. As with all discussions, these questions usually have no single "correct" answer.
- The end of chapter material includes 10 Problems, based on the chapter contents and entailing some numerical calculation. In many cases the problems are tied directly to quantitative statements made (but not worked out in detail) in the text. The solutions to the problems are not contained verbatim within the chapter, but the information necessary to solve them has been presented in the text. Answers appear at the end of the book.
The Astronomy: A Beginner's Guide to the Universe, Fourth Edition eBook CD-ROM is included free with each new copy of the text. This easyto-navigate eBook contains a fully hyperlinked electronic version of the text to help the reader quickly find related information and assist in review. The eBook, which has been redesigned for easier and clearer navigation, features:
- New! Interactive Tutorials: Written by Phillip Langill (University of Calgary). These animated, interactive Flash TM files, denoted by an icon in the text, allow students to explore the ideas and concepts from the text in depth. Students are engaged in the thought process as they answer questions and change parameters in these exploratory activities.
- New! Physlet® Illustrations for Astronomy: Written by Chuck Niederriter and Steve Mellema (Gustavus Adolphus College); Physlets by Wolfgang Christian (Davidson College). Through animation, these brief Java applets, denoted with an icon in the text, further illustrate concepts from the text. Each illustration is followed by a series of questions that encourages students to think critically about the concept at hand.
- Over 3,000 internal links that connect chapter Learning Goals, end-ofchapter material, and key concepts to the corresponding text discussion.
- 61 narrated videos and animations imbedded within the text, at point of use. These help to bring text figures and concepts to life.
- Direct access to the Companion Website, which provides updated images, videos, animations, multiple-choice quizzes, and algorithmic versions of the end of chapter problems.This powerful resource provides students with a variety of interactive materials to discover more about topics that interest them, test their conceptual understanding of the course material, and practice their problem-solving skills. It includes:
- Annotated images, videos, and animations that are regularly updated to reflect the most recent astronomical discoveries.
- Interactive multiple-choice quizzes with hints and instant feedback.
- Algorithmically generated versions of the end-of-chapter problems from the text.
- Links to associated websites that are regularly updated for currency and relevancy.
From the Back Cover
Astronomy Today 4/e (ISBN 0-13-091542-4) is the more comprehensive text by this: proven team of authors. This twenty-eight chapter text begins with the foundations of the history of science and physics as they relate to astronomy (Part One), then proceeds with an "Earth-out" organization for coverage of the solar system (Part Two), stars and stellar evolution (Part Three), and galaxies and cosmology (Part Four). New with the fourth edition, the book is now available in two paperback splits:
Astronomy Today 4/e: The Solar System (ISBN 0-13-093560-3) covers Part One on foundations (Chapters 1-$); Part Two on the solar system (Chapters 6-15); the Sun chapter (Chapter 16); and the final chapter on life in the universe (Chapter 28).
Astronomy Today 4/e: Stars and Galaxies (ISBN 0-13-093571-9) includes Part One on foundations (Chapters 1-S); Part Three on stars and stellar evolution (Chapters 16-22); and Part Four on galaxies and cosmology (Chapters 23-28).
Astronomy: A Beginner's Guide to the Universe 4/e (ISBN 0-13-100727-0) is the authors' briefer text. It covers the same scope of material in the same order as Astronomy Today 4/e, but with less detail and in fewer chapters (eighteen instead of twenty-eight) and fewer pages.
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