Are we alone in the universe? It's a fundamental question for Earth-dwelling humankind. Are there other worlds like ours, out there somewhere? In Hidden in the Heavens, Jason Steffen, a former scientist on NASA's Kepler mission, describes how that mission searched for planets orbiting Sun-like stars--especially Earth-like planets circulating in Earth-like orbits. What the Kepler space telescope found, Steffen reports, contradicted centuries of theoretical and observational work and transformed our understanding of planets, planetary systems, and the stars they orbit. Kepler discovered thousands of planets orbiting distant stars--a bewildering variety of celestial bodies, including rocky planets being vaporized by the intense heat of their host star; super-Earths and sub-Neptunes; gas giants several times the size and mass of Jupiter; and planets orbiting in stellar systems that had only been imagined in science fiction. Steffen offers a unique, inside account of the work of the Kepler science team (and the sometimes chaotic interactions among team members), mapping the progress of the mission from the launch of the rocket that carried Kepler into space to the revelations of the data that began to flow to the supercomputer back at NASA--evidence of strange new worlds unlike anything found in our own solar system.