Horizons Exploring the Universe,
15th Edition

Michael A. Seeds, Dana Backman, Eric Wegryn

ISBN-13: 9780357976616
Copyright 2025 | Published
544 pages | List Price: USD $205.95

The 15th Edition of Seeds/Backman/Wegryn's HORIZONS: EXPLORING THE UNIVERSE, is made for aspiring astronomers and science enthusiasts alike. This edition brings together the latest discoveries and interactive tools to match a variety of learning styles. Explore stars and how they're connected to planet formation and life on Earth.


1. Here and Now.
Where Are We? When Is Now? Why Study Astronomy?
2. A User's Guide to the Sky.
The Stars. The Sky: Its Motions and Cycles.
3. Cycles of the Sun and Moon.
Cycles of the Sun. Astronomical Influences on Earth's Climate. The Changeable Moon.
4. The Origin of Modern Astronomy.
Prehistoric Astronomy. Classical Astronomy. The Copernican Revolution. Planetary Motion. Galileo Galilei. Isaac Newton and Orbital Motion.
5. Light and Telescopes.
Radiation: Information from Space. Telescopes. Observatories on Earth: Optical and Radio. Airborne and Space Observatories. Astronomical Instruments and Techniques.
6. Atoms and Spectra.
Atoms. Interactions of Light and Matter. Understanding Spectra.
7. The Sun.
The Solar Atmosphere. Solar Activity. Nuclear Fusion in the Sun.
8. The Family of Stars.
Star Distances. Apparent Brightness, Intrinsic Brightness, and Luminosity. Stellar Spectra. Star Sizes. Star Masses -- Binary Stars. A Census of the Stars.
9. The Formation of Stars and Planets.
The Interstellar Medium. Making Stars from the Interstellar Medium. Young Stars and Disks.
10. Stellar Structure and Evolution.
Stellar Structure and Nuclear Fusion. Main-Sequence Stars. After the Main Sequence. Lower-Main-Sequence Stars. The Evolution of Binary Systems.
11. Supernovas, Neutron Stars, and Black Holes.
The Deaths of Massive Stars. Neutron Stars. Black Holes. Power Unleashed.
12. The Milky Way Galaxy.
Discovery of the Galaxy. Structure of the Galaxy. Spiral Arms and Star Formation. The Nucleus of the Galaxy. Origin and History of the Milky Way Galaxy.
13. Galaxies: Normal and Active.
The Family of Galaxies. Measuring the Properties of Galaxies. The Evolution of Galaxies. Active Galactic Nuclei. Supermassive Black Holes.
14. Modern Cosmology.
Introduction to the Universe. The Big Bang Theory. Space and Time, Matter and Energy. Twenty-First-Century Cosmology.
15. The Solar System: A Cosmic Family Portrait.
The Great Chain of Origins. A Family Portrait of the Solar System. A Recipe for Planets.
16. Earth and Moon: Bases for Comparative Planetology.
A Travel Guide to the Terrestrial Planets. Planet Earth. The Moon.
17. Mercury, Venus, and Mars.
Mercury. Venus. Mars.
18. The Giant Planets.
A Travel Guide to the Outer Solar System. Jupiter. Saturn. Uranus. Neptune.
19. Comets, Asteroids, Meteorites.
Comets. Asteroids. Pluto and the Kuiper Belt. Meteoroids, Meteors, and Meteorites. Asteroid and Comet Impacts.
20. Extrasolar Planets: Worlds Around Other Suns.
Properties and Formation of the Solar System, Reprise. Discovering Extrasolar Planets. Extrasolar Planets Zoology.
21. Astrobiology: Life on Other Worlds.
The Nature of Life. Life in the Universe. Intelligent Life in the Universe.
Appendix A: Units and Astronomical Data.
Appendix B: Observing the Sky.
Answers to Even-Numbered Problems.

  • Michael A. Seeds

    Mike Seeds was a professor of physics and astronomy at Franklin and Marshall College in Lancaster, Pennsylvania, from 1970 until his retirement in 2001. In 1989 he received F&M College’s Lindback Award for Distinguished Teaching. Mike’s love for the history of astronomy led him to create upper-level courses on archaeoastronomy and on the Copernican Revolution (“Changing Concepts of the Universe”). His research interests focused on variable stars and automation of astronomical telescopes. Mike is coauthor with Dana Backman of Horizons: Exploring the Universe, 12th edition (2012); Universe: Solar Systems, Stars, and Galaxies, 7th edition (2012); Stars and Galaxies, 8th edition (2013); The Solar System, 8th edition (2013); and ASTRO, 2nd edition (2013), all published by Cengage. He was senior consultant for creation of the 20-episode telecourse accompanying his book Horizons: Exploring the Universe.

  • Dana Backman

    Dana Backman taught in the physics and astronomy department at Franklin and Marshall College in Lancaster, Pennsylvania, from 1991 until 2003. He invented and taught a course titled “Life in the Universe” in F&M’s interdisciplinary Foundations program. Dana now teaches introductory Solar System astronomy at Santa Clara University and introductory astronomy, astrobiology, and cosmology courses in Stanford University’s Continuing Studies Program. His research interests focus on infrared observations of planet formation, models of debris disks around nearby stars, and evolution of the solar system’s Kuiper belt. Dana is employed by the SETI Institute in Mountain View, California, as director of education and public outreach for SOFIA (the Stratospheric Observatory for Infrared Astronomy) at NASA’s Ames Research Center. Dana is coauthor with Mike Seeds of Horizons: Exploring the Universe, 14th edition (2018); Universe: Solar Systems, Stars, and Galaxies, 7th edition (2012); Stars and Galaxies, 8th edition (2013); The Solar System, 8th edition (2013); and ASTRO, 2nd edition (2013), all published by Cengage.

  • Eric Wegryn

  • Elevate your teaching experience with the 15th Edition, which features fresh discoveries, new images and updated figures. A new Chapter 20 dives into the fascinating topic of extrasolar planets, featuring groundbreaking insights from the Kepler and TESS space telescopes, along with the latest findings from ground-based research programs.

  • Discover the fascinating realm of Prehistoric Astronomy with this exciting update. Delve into this brand-new subsection that explores the wonders of archaeoastronomy and non-European astronomy.

  • Gain detailed insights into groundbreaking observatory facilities like the James Webb Space Telescope and the Tianyan Radio Telescope. Access the latest and most up-to-date astronomical discoveries right at your fingertips.

  • Chapters 9 ("Star and Planet Formation"), 10 ("Stellar Structure and Evolution"), and 11 ("Supernovas, Neutron Stars and Black Holes") have been reorganized, enhanced, and renamed. This latest revision groups subtopics together for a more seamless learning experience. To enrich student understanding, a new section 11-4 "Power Unleashed", consolidates text and figures regarding accretion disks, jets, gamma-ray bursts and magnetars.

  • Discover captivating new "Concept Art" like the Event Horizon Telescope image of Sgr A* and an up-to-date spread on space exploration.

  • Your students will enjoy participating in stimulating discussions and thought-provoking inquiries. In Chapter 14 ("Modern Cosmology"), students explore how scientists detect cosmological gravity waves and emphasize the careful reanalysis of data by multiple research teams. Through this interactive learning process, they gain a deep understanding of the significance of double-checking results and the importance of avoiding wishful thinking when conducting scientific research.

  • Chapter 15 ("The Solar System") has been reorganized, revised, and renamed with updated information on planet orbital migration. Additionally, content related to extrasolar planets has been relocated to a new chapter.

  • Chapter 18 ("The Giant Planets") and Chapter 19 ("Comets, Asteroids, and Meteorites") have been reorganized, revised, and renamed to group their respective subtopics together in a more logical sequence, including moving content regarding Pluto and the Kuiper Belt from Chapter 18 to Chapter 19. These chapters come alive with new findings and images from spacecraft and ground-based observations. Furthermore, the two Concept Art spreads in Chapter 18 regarding rings of the Jovian planets are consolidated into one, and a new Concept Art spread regarding the Galilean satellites of Jupiter and several active satellites of Saturn have been added.

  • The conversational tone and student-friendly approach transport students beyond merely memorizing facts and figures, into developing a genuine appreciation for the universe's mysteries.

  • Each chapter begins with an informative "Guidepost" feature, which acts as a roadmap, connecting the current chapter with ones that came before and after. A short list of important questions highlights the chapter's learning objectives, ensuring students stay focused and engaged.

  • "How Do We Know?" boxes help your students understand the inner workings of science. These features dive into various topics, such as the difference between hypotheses and theories, the application of statistical evidence, the construction of scientific models and more. By exploring these fundamental aspects, students gain a deeper appreciation of the scientific method and develop critical thinking skills that extend beyond the realm of astronomy.

  • Student-friendly Concept Art offers a visually compelling approach to learning. This two-page format skillfully combines various ideas and images, helping your students synthesize. Colors, images and numerical keys thoughtfully guide students to the main concepts, enhancing their overall learning experience.

  • Common Misconceptions are highlighted to address and rectify popularly held misconceptions about astronomy.

  • Practicing Science boxes found at the end of most chapters engage your students in scientific inquiry. These boxes promote critical thinking as they investigate the mysteries of the cosmos, and reinforce understanding of the scientific process. To encourage further exploration, many of the Practicing Science boxes conclude with additional questions that guide students toward deeper avenues of investigation.

Cengage provides a range of supplements that are updated in coordination with the main title selection. For more information about these supplements, contact your Learning Consultant.

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