NASA's Kepler Finds Two Earth-Size Planets Around Sunlike Star
Discovery is next major step in quest for alien Earths, team says.
The find comes on the heels of Kepler's first potentially Earthlike planet orbiting squarely within its star's water-friendly "Goldilocks zone"—the region that's not too hot and not too cold for liquid water to exist on a planet's surface.
Designated Kepler-20e and Kepler-20f, the two new planets are comparable in size to Earth and Venus: At 0.87 times the size of Earth, Kepler-20e is slightly smaller than Venus, while Kepler-20f is 1.03 times Earth's radius.
But both new extrasolar planets—or exoplanets—orbit their star much too closely to be within the habitable zone.
In fact, the entire Kepler-20 system is believed to contain at least five planets all orbiting their star within a distance smaller than that between Mercury and the sun.