Astronomers hunting for another Earth have found the closest match yet, a potentially rocky planet circling its star at the same distance as the Earth orbits the Sun, NASA has said.
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.
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"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.
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This planet sits squarely in the Goldilocks zone - where life could exist because it is neither too hot nor too cold to support liquid water, the US space agency said.
"Today the Earth is a little less lonely," said Jon Jenkins, Kepler data analysis lead scientist at NASA's Ames Research Center in Moffett Field, California.
Kepler 452b's star is 1.5 billion years older, four percent more massive and 10 percent brighter than our sun.
But at a distance of 1,400 light-years away, humankind has little hope of reaching this Earth-twin any time soon.
"You and I probably won't be travelling to any of these planets without some unexpected breakthrough, but you know, our children's' children's children may," said Jeff Coughlin, Kepler research scientist at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California.
The Kepler mission launched in 2009 to search for exoplanets, which are planets outside our solar system, particularly those about the size of Earth or smaller.
On Thursday, NASA released the latest catalog of exoplanet candidates, adding more than 500 new possible planets to the 4,175 already found by the space-based telescope.
The new list includes 12 candidates that are less than twice the diameter of Earth and which are orbiting in the habitable zones of their stars.
Of those 12 new candidates, Kepler 452b "is the first to be confirmed as a planet", NASA said.
The Kepler mission has cost NASA about $600m, and the US space agency said in 2013 that two of its orientation wheels had lost function, leaving the space telescope beyond repair.