NASA's Kepler space telescope has found the closest match yet to a world that is similarly sized to Earth and circling a sun-like star at the right distance for liquid surface water, a condition believed to be necessary for life, scientists said Thursday.
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The newly found world, called Kepler-452b, is located about 1,400 light-years away in the constellation Cygnus.
"In my mind, this is the closet thing we have to another planet like the Earth," Jon Jenkins, head of Kepler data analysis at NASA's Ames Research Center in Moffett Field, Calif., told reporters on a conference call Thursday.
Kepler-452b is about 60 percent wider than Earth and estimated to have five times the mass, making it most likely a rocky world. It circles a G2-type star very much like the sun, but estimated to be closer to 6 billion years old, compared to the 4.6-billion-year age of the solar system.
"That's a considerable opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet," Jenkins said.
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"It's simply awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star," Jenkins said. "That's considerable time and opportunity for life to arise somewhere on its surface, or in its oceans, should all the necessary ingredients and conditions for life exist on this planet."
Kepler-452b orbits its parent star every 385 days, so it is located just about 5 percent farther away from the star than Earth circles the sun. The star's age means it's about 10 percent bigger and 20 percent brighter than the sun, Jenkins said.
If Kepler-452b is rocky, scientists expect it would be about five times more massive than Earth and twice Earth's surface gravity. It would have a thicker, cloudier atmosphere and most likely active volcanoes, Jenkins added.
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Today, Kepler 452-b receives 10 percent more energy from its parent star than Earth does from the sun, but that wasn't always the case.
"When this star was young, it was only about 80 percent of its present size and 64 percent as bright, so the planet received 64 percent as much energy then," Jenkins said.
As the star continues to grow, Kepler 452-b will no longer be in a habitable, water-friendly zone, a future that awaits Earth as well.
Kepler-452b is the first of 12 potential Earth-twins that has been confirmed as a planet, all of which circle in life-friendly orbits around their parent stars. More than half of those stars are the same type as the sun.
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"A lot of them are very interesting candidates. For example, one of them appears to be just 15 percent larger than Earth ... and receiving about three-fourths the energy that Earth does. There's a lot of other ones similar to that that are really tantalizing to go after," Jeff Coughlin, a Kepler research scientist at SETI Institute in Mountain View, Calif., told Discovery News.
Overall the list of candidate planets found by Kepler has reached 4,696. Another 1,030 Kepler finds have been confirmed, NASA said.
The research will be published in an upcoming issue of The Astronomical Journal.