By Adam Clark Estes | TheAtlanticWire

Just over a week after astronomers boldly announced that they would discover an Earth twin elsewhere in the universe within the year, NASA’s Kepler telescop spotted a pretty good candidate. Unglamorously named KOI 172.02 -- KOI stands for Kepler Object of Interest -- this planet is the most Earth-like planet astronomers have discovered yet.

The differences are slight. It’s roughly 50 percent larger than Earth and orbits a star that closely resembles our own sun at a distance that would make the surface of the planet habitable. (The size makes it a "super Earth" rather than an "Earth twin.") With an 242-day long year, it’s slightly closer to its star than the Earth is to the Sun but otherwise enjoys all of the same ideal conditions as we do, as far as astronomers can tell. "This was very exciting because it’s our fist habitable-zone super Earth around a sun-type star," said Natalia Batalha, a Kepler co-investigator at NASA’s Ames Research Center in California. "It’s orbiting a star that’s very much like our sun. Previously the ones we saw were orbiting other types of stars."

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This artist rendering released Monday Jan. 7,2013 by Harvard-Smithsonian Center for Astrophysics shows the different types of planets in our Milky Way galaxy detected by NASA’s Kepler spacecraft. A new analysis of Kepler data found there are at least 17 billion planets the size of Earth.

This illustration provided by the Harvard-Smithsonian Center for Astrophysics shows artist’s renderings of planets Kepler-20e and Kepler-20f compared with Venus and the Earth. Scientists have found the two Earth-sized planets orbiting a distant star, an encouraging sign for prospects of finding life elsewhere. The discovery shows that such planets exist and that they can be detected by the Kepler spacecraft, said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. They’re the smallest planets found so far outside the solar system. Scientists are seeking Earth-sized planets as potential homes for extraterrestrial life.