The Little Book of Exoplanets

In this spellbinding survey, Winn (Photonic Crystals), an astrophysics professor at Princeton University, proves more than up to the task of making astrophysics accessible and enjoyable for lay readers. Providing a fascinating overview of exoplanets, or planets outside our solar system, he explains that there are real-life planets that orbit two suns the way that Luke Skywalker’s home planet does in Star Wars, and that “puffball planets” have densities “comparable... to Styrofoam.” Winn highlights the strategies astronomers use to study distant cosmic bodies, describing how a planet’s mass and orbit orientation can be deduced from studying how much a star’s light dims when the planet passes in between the star and Earth, which causes an often barely perceptible eclipse. Other methods involve inferring cosmic bodies’ movements by measuring variations in the frequency of light and radio waves, as well as studying the ways in which a planet’s atmosphere absorbs and refracts starlight on its way to Earth. There’s plenty here to spark the curiosity of armchair astronomers (“It’s always raining iron” on WASP-76b, a planet twice the size of Jupiter), and plentiful diagrams help clarify the inventive methods of studying exoplanets. This inspires wonder at the eccentricities of the universe. Illus. (July)