A possible Earth twin has been confirmed orbiting a sunlike star 600 light-years away—and the new planet may be in just the right spot for supporting life, NASA announced.
Discovered by the Kepler space mission, the new planet—dubbed Kepler-22b—is the first world smaller than Neptune to be found in middle of its star's habitable zone.
Also called the Goldilocks zone, the habitable zone is the region around a star where a planet's surface is not too hot and not too cold for liquid water—and thus life as we know it—to exist.
In fact, only two known planets fit this description so far—Gliese 581d and HD 85512—and both worlds orbit at the very edges of their stars' habitable zones, making them more akin to Venus and Mars than to Earth.
"It's also orbiting a star that's almost a twin of our sun, whereas the other two detections are orbiting significantly cooler stars."
The Kepler mission finds new worlds by simultaneously monitoring 150,000 stars for dips in brightness, which are indicative of planets passing in front of—or transiting—their stars.
Kepler-22b was among the 54 roughly Earth-size planet candidates announced by the Kepler team in February. But the spacecraft needs to watch at least three transits to confirm that a signal is a planet.
The new planet is about 2.4 times the radius of Earth, but scientists don't yet know its composition, because they are still missing a crucial piece of information: Kepler-22b's mass.
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