Named Kepler 452b, the planet is about 60 percent larger than Earth. It could have active volcanoes, oceans and sunshine like ours, twice as much gravity and a year that lasts 385 days, scientists said on Thursday.
"Today we are announcing the discovery of an exoplanet that, as far we can tell, is a pretty good close cousin to the Earth and our Sun," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington.
"This is about the closest so far, and I really emphasize the 'so-far,'" he added, describing Kepler 452b as "the closest twin," or "Earth 2.0."
The planet was detected by the US space agency's Kepler Space Telescope, which has been hunting for other worlds like ours since 2009.