Alien Earths: The New Science of Planet Hunting in the Cosmos

Kaltenegger, director of the Carl Sagan Institute to Search for Life in the Cosmos at Cornell University, debuts with a stellar exploration of how she and other astronomers are searching for extraterrestrial life. “Signs of life are written in a planet’s light—if you know how to read it,” Kaltenegger writes, explaining that because “the electrons of different atoms absorb specific colors of light,” scientists can discern the chemical composition of the air light has passed through by examining what wavelengths have or haven’t been absorbed. These interactions create a “barcode” or “light fingerprint,” Kaltenegger notes, recounting how she’s made lava strips and grown microorganisms in her lab so she can study their light signatures and be able to recognize them if scientists spot similar ones in space. Highlighting discoveries that changed astronomers’ understanding of alien life, Kaltenegger points out that in 2020 a space telescope found a gas giant orbiting a dead star, raising the possibility that planets, and any life-forms they contain, may be able to “survive the demise of their stars.” The breezy prose makes the sophisticated science accessible, and armchair astronomers will be entranced by the descriptions of remarkable exoplanets, including one “so hot that rocks melt, evaporate, then rain down again.” Readers will be riveted. Agent: Deirdre Mullane, Mullane Literary. (Apr.)