Hidden in the Heavens: How the Kepler Mission’s Quest for New Planets Changed How We View Our Own

Astronomer Steffen—who worked on NASA’s Kepler space telescope mission, which lasted from the telescope’s 2009 launch through its retirement in 2018—serves up an eye-opening exploration of the goals, successes, and challenges associated with the endeavor. He describes how the idea for Kepler was conceived in the 1980s as a long-shot attempt to find Earth-like planets, and the first observations of planets outside our solar system in the 1990s convinced NASA to back the project. The mission greatly expanded scientific knowledge of distant celestial bodies, Steffen contends, noting the discoveries of Jupiter-like planets that orbit their stars in mere days and Earth-like planets so close to their stars that they leave “a tail of vaporized rock trailing behind.” Most consequentially, the conditions that gave rise to life on Earth might not be as rare as once thought, with scientists now estimating that “Earth-sized planets in Earth-like orbits probably orbit roughly a quarter of all stars.” Steffen offers a competent account of Kepler’s construction and findings, but involved discussions of how scientists used “lensing” (the study of how much a star’s light dims as an orbiting planet passes between the star and a telescope) and spectroscopy (breaking light from stars “into its spectrum of constituent colors”) can get a bit technical. Still, this will please armchair astronomers. (Oct.)