科学美国人60秒:Space Scope Spots 3 Possibly Habitable Planets

The search for habitable, Earth-like planets keeps turning up promising candidates. And although astronomers have yet to find an Earth twin, some newly discovered worlds are pretty interesting in their own right.

NASA’s Kepler space telescope recently spotted seven new exoplanets, three of them in or near their stars’ so-called habitable zones. That’s the temperate region where a planet could accommodate liquid water. But all three worlds are bigger than Earth, and their composition is uncertain. They could be rocky like Earth or water worlds without landmasses. The discoveries are in the journal Science [William J. Borucki et al., Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone] and in the Astrophysical Journal [Thomas Barclay et al., A Super-Earth-Sized Planet Orbiting In Or Near The Habitable Zone Around A Sun-Like Star].
 

The planet Kepler 69c follows a Venus-like orbit around a sunlike star. Kepler 69c could be habitable, or it could be a bit too hot, depending on how much starlight the planet absorbs.

Kepler 62e and 62f are smaller, and orbit a star smaller than the sun. One planet receives about 60 percent less radiation than warms Earth, and the other gets about 20 percent more. It’s possible that those attributes render Kepler 62e or 62f habitable, but astronomers don’t yet know whether they are too cold, too hot or just right.

—John Matson