Introductory astronomy is one of the most popular general education STEM (science, technology, engineering, and mathematics) classes at colleges and universities. Most students who enroll in it are nonscience majors, and astronomy is the last, or perhaps only, college-level science course they will ever take. The Cosmos: Astronomy in the New Millennium, now in its fifth edition, offers a descriptive presentation of astronomy with that audience in mind. Authors Jay Pasachoff and Alex Filippenko are accomplished astronomers, celebrated educators, and champions of science popularization. Their experience communicating science to nonprofessionals is evident in the updated edition of The Cosmos, a comprehensive, easy-to-read survey of astronomy appropriate for use in a general-education science course.

The diverse array of topics presented in The Cosmos allows professors great flexibility when using the book in their courses. The text could be assigned for either a one-semester survey course emphasizing selected topics or a two-semester introductory sequence using the entire book. The first few chapters cover general ideas about the nature of astronomy, light, telescopes, celestial motions, and gravity. The book moves on to a grand tour of the universe, beginning with Earth and moving outward through space and introducing readers to topics such as stars, stellar evolution, black holes, galaxies, and cosmology. The newest edition includes recent developments such as the results of the New Horizons mission to Pluto and Ultima Thule, the 2017 total solar eclipse, gravitational wave detections, and the Kepler and TESS missions—additions I appreciate.

To help students engage with the material, the authors have included several interesting pedagogical features, such as the “Star Parties” and “Lives in Science” boxes interspersed throughout the text. “Star Parties” boxes contain observational exercises related to the material. For example, students are instructed on how they could re-create Galileo’s observations with a small telescope or track the motion of Jupiter and Saturn through the sky over the course of several days. Those features encourage students to connect to the material outside the classroom.

As the name suggests, “Lives in Science” boxes provide short biographies about notable scientists. I think they have the potential to foster an inclusive classroom atmosphere by portraying scientists as real people; biographical stories help students feel that they, too, can make meaningful contributions to science. I was therefore surprised to find that only six individuals were featured: Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei, Isaac Newton, and Albert Einstein. I am disappointed that the book did not include stories of more recent and diverse scientists.

Furthermore, although the authors successfully provide a descriptive presentation of astronomy, I have concerns about some gaps and omissions in the text. The Cosmos occasionally lacks depth, and the choices of key terms are not always carefully thought through. For example, the concepts of continuous spectra and absorption lines are well developed, and both terms appear in boldface for easy identification. However, the authors do not provide the same level of description for the equally important emission lines; the text mentions them only briefly and does not put the term in bold. Similarly, the beginning of the section describing the appearance of the Moon reads, “Even binoculars reveal that the Moon’s surface is pockmarked with craters. Other areas, called maria […], are relatively smooth and dark.” That description makes no mention of the lunar highlands, a major feature of the Moon’s appearance. Such inconsistencies and omissions in the coverage of important terms are troubling.

The authors do an excellent job of using figures and photographs to aid in the explanation of concepts and hold students’ interest. However, not all of the images are well presented or pedagogically useful. Several pictures are grouped into multipart figures with one overwhelmingly long caption describing the set. In many instances, the captions contain more information about the concept than the text itself. Although I appreciate the number of images, I wish some of them were better incorporated into the text.

Astronomy educators often debate the appropriate amount of quantitative material for an introductory astronomy course. Pasachoff and Filippenko acknowledge that many instructors will prefer a more mathematical description of the universe’s physical processes than the one provided in their book. I view astronomy as a quantitative science, and The Cosmos includes too little math for my taste. If you are looking for an introductory astronomy textbook that includes a significant quantitative component, then this is not the book for you.

Overall, The Cosmos provides an excellent tour of the universe for those interested in a qualitative description of a broad array of topics in astronomy. Several features will encourage student engagement and allow instructors in diverse astronomy classes to customize their use of the text. However, the textbook occasionally lacks sufficient depth. I would suggest that instructors looking for more than a basic overview consider supplementing The Cosmos with deeper discussions of physical phenomena and quantitative ideas.

Kristen Thompson is an assistant professor of physics at Davidson College in North Carolina. Her research explores the strengths of magnetic fields in the Milky Way and the fields’ connection to star formation.