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First 'Earth-Size Planets Beyond Our Solar System' Discovered

A NASA illustration comparing the newly discovered planets to Venus and Earth. Kepler-20e is slightly smaller than both Venus and Earth. Kepler-20f is slightly larger. i i

hide captionA NASA illustration comparing the newly discovered planets to Venus and Earth. Kepler-20e is slightly smaller than both Venus and Earth. Kepler-20f is slightly larger.

NASA/Ames/JPL-Caltech
A NASA illustration comparing the newly discovered planets to Venus and Earth. Kepler-20e is slightly smaller than both Venus and Earth. Kepler-20f is slightly larger.

A NASA illustration comparing the newly discovered planets to Venus and Earth. Kepler-20e is slightly smaller than both Venus and Earth. Kepler-20f is slightly larger.

NASA/Ames/JPL-Caltech

Calling it "the next important milestone in the ultimate search for planets like Earth," NASA has announced the discovery of "the first Earth-size planets orbiting a sun-like star outside our solar system."

Scientists don't think Kepler-20e and Kepler-20f, as the planets are now known, are habitable. Located about "1,000 light years away in the constellation Lyra," they are too close to their sun and would be "very hot, inhospitable worlds," NASA says.

But their discovery, "demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them," Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., tells the space agency.

As The Associated Press says:

"Since it was launched in 2009, NASA's planet-hunting Kepler telescope has found evidence of dozens of possible Earth-sized planets. But Fressin's report is the first to provide confirmation, said Alan Boss of the Carnegie Institution for Science in Washington. He's a member of the Kepler science team but not an author of the paper."

We've posted about some of the Kepler telescope's findings before, most recently the discovery of a planet that may be orbiting a star in the "habitable zone" that could sustain life.

Space.com explains how scientists concluded they had found the two Earth-size planets:

"Fressin and his colleagues used NASA's Kepler space telescope, which noticed the tiny dips in the parent star's brightness when the planets passed in front of it, blocking some of its light (this is called the transit method). The researchers then used ground-based observatories to confirm that the planets actually exist by measuring minute wobbles in the star's position caused by gravitational tugs from its planets."

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