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Tuesday
Dec202011

NASA Kepler Probe Finds Two Earth-Sized Planets Orbiting Star

NASA [dot] gov(BOSTON) -- NASA's Kepler space telescope has found two new planets orbiting a distant sun-like star, and the researchers who made the find say these two are the size of Earth or smaller. That's a first in the search for extraterrestrial life.

If the discovery holds up under scrutiny by other scientists, it could be a very big deal. Earth-sized planets are considered critical in the search for life elsewhere in the universe, but until now, scientists said their instruments were not sensitive enough to detect them.

"Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate," wrote Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, the leader of the team that made the discovery. "The outer planet could have developed a thick water vapour atmosphere."

The team is published its report Tuesday online in the journal Nature.

The two newly-found planets, called Kepler-20e and Kepler-20f, are much too far away to be seen directly. They circle a star about 950 light-years away in the constellation Lyra, which appears high in the sky over North America on a summer night. Scientists measured the miniscule dimming of their host star as they passed in front of it, and then did the math to figure out how large they are likely to be and in what orbits they move.

Kepler-20e and f are probably too hot to be friendly to life -- they are so close to their sun that one of them circles it in just six Earth days, and the other does it in 19. But the simple fact that they've been found, say the scientists, is reason to expect that others like them exist.

"It demonstrates for the first time that Earth-sized stars exist around other stars, and that we are now able to detect them," said Fressin at a news briefing Tuesday.

Linda Elkins-Tanton of the Carnegie Institution for Science in Washington said the larger of the two planets, Kepler-20f, was especially intriguing.

"If it was formed with water, which I think is possible, it could have been habitable in the past," she said.

"We would be remiss if we did not do our best to find more planets just like our own," said Alan Boss, a colleague of hers at the Carnegie Institution, in an email to ABC News. "That does not mean that we necessarily think that only exact Earth twins could be inhabited, just that we at least had better be able to find Earth twins, and then along the way we will be certain to uncover all sorts of other types of exoplanets that should be habitable, and perhaps even inhabited."

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