Kepler Finds First Earth-Sized Exoplanet in Habitable Zone

By Will Smith

Over the last few years, astronomers have found hundreds of exoplanets, but they've all been significantly larger than the earth. Not any more.

Over the last ten years, astronomers have discovered hundreds of exoplanets using a handful of techniques, but until now, most of those planets are either outside the habitable zone or are much larger than earth--think gas giants. A newly discovered planet, Kepler-186f, is the first planet in the habitable zone, the orbits around a star where formation of liquid water is possbile, of a comparable size to Earth.

We don't know much about the planet, but Kepler-186f is about 500 light years away, it's about 10% bigger than earth by volume, and it orbits its M-dwarf star every 130 days.