The artist's concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone—a range of distance from a star where liquid water might pool on the ...

The first Earth-size planet orbiting a star in the “habitable zone” — the range of distance from a star where liquid water might pool on the surface of an orbiting planet.

Technicians working inside the Astrotech Space Operations facility near NASA's Kennedy Space Center look over the Kepler spacecraft soon after it arrived in Florida in preparation for launch. [Read ...

We've come a long way. First it was only giant planets seared by hot proximity to their host stars. Not anymore. Astronomers announced the discovery today of the first Earth-sized planet in the ...