Scientists have discovered a planet not too much bigger than Earth that's circling a distant star that's much like our own sun. What's more, this planet is in the "Goldilocks zone" around that star — a region that's not too hot and not too cold. That's the kind of place that could be home to liquid water and maybe even life. The planet, known as Kepler-22b, is the first near-Earth-sized planet to be found smack dab in the middle of the habitable zone of a twin to our Sun.
The planet is about 2 1/2 times the size of the Earth. It orbits a little closer to its star than our planet does to our sun, and goes around once every 290 days compared with our 365. But its star is a bit cooler than our sun, says William Borucki of NASA Ames Research Center, who heads NASA's Kepler space telescope mission, which detected this planet. "That means that that planet, Kepler-22b, has a rather similar temperature to that of the Earth," Borucki says. "Its surface temperature would be something like 72 Fahrenheit."
It's not yet clear what kind of surface the planet might have — researchers don't know if the planet is made mostly of rock or water or something else. And don't expect astronauts to climb on a rocket and go there anytime soon. "The star is some 600 light-years away," says Borucki, "so it's not terribly far away, but not terribly close either."