This story was updated at 2:40 EST. Astronomers on Tuesday (Dec. 20) announced the discovery of the first two Earth-size alien planets — a historic find for sure, but the newfound worlds didn't ...

NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in ...

For life as we know it to arise on another planet, scientists think the alien world must have three key ingredients: organic molecules that can form complex structures, energy to jiggle those ...

WASHINGTON (Reuters) - NASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system, a milestone in the search for planets like the earth, the ...

The same team that recently discovered the possibly water-covered, life-supporting planet, Kepler 22b, two weeks ago announced the discovery of two more Earth-sized planets on Monday. Ars Technica's ...

Even if you’re a big fan of exoplanets — that is, worlds orbiting stars beyond the sun — the flurry of major discoveries over the past few months may have been hard to process. Astronomers have lately ...