NASA Discovers Kepler 186 f, An Earth Size Planet in Habitable Zone

Astronomers announced the discovery of Kepler-186f, the first truly Earth-size alien planet ever found in a star's "habitable zone" — that just-right range of distances where liquid water could exist on a world's surface. Kepler-186f is a rocky world just 10 percent bigger than Earth that lies 490 light-years away.

Never before has a planet so close to Earth in size, and therefore gravity, been found in the habitable zone where liquid water can exist.

"This is the best case for a habitable planet yet found. The results are absolutely rock solid," said University of California, Berkeley astronomer Geoff Marcy.

The discovery suggests that many more such earth-like planets will be discovered in the near future.