Mirror Earth: The Search for Our Planet’s Twin

Science writer Lemonick (The Georgian Star) offers readers an informal and accessible view into the work of “exoplaneteers”: astronomers dedicated to searching out not just planets orbiting distant worlds, but “Mirror Earths,” Earth-like planets that might harbor life. It’s not an easy task. Distance and stellar brightness relative to the exoplanets make them difficult to see directly. Astronomers must rely on techniques like measuring how much a star’s brightness dims as a planet passes in front of it, or how much the star appears to “wobble” due to the gravitational attraction between it and an orbiting planet. Lemonick introduces planet-hunting pioneers like mild-mannered Bill Borucki, indefatigable Geoff Marcy, former cosmologist Sara Seager, and nurse-turned-astrophysicist Debra Fischer, revealing personalities as well as research frustrations and successes. Exoplanets, it turns out, aren’t really rare at all; they’re just nothing like what we expected to find. Most are more like hot Jupiters than cozy Earths. Discoveries also raise questions about what habitable means; after all, there’s no rule that says life must be Earth-like. Today’s exoplanet discoveries are building the foundation for learning just what kind of life is possible out there. B&w illus. Agent: Cynthia Cannell, Cynthia Cannell Literary Agency. (Oct.)