It’s a Small World: Kepler Spacecraft Discovers First Known Earth-Size Exoplanets

NASA's Kepler spacecraft is starting to put the pieces together in its search for virtual Earth twins in other planetary systems. Kepler, which launched in 2009 , is on the lookout for planets that are about the size of Earth and have temperate surface conditions. One half of that formula was realized on December 5 when mission scientists announced the discovery of a planet in the so-called habitable zone, called Kepler 22 b , a few times larger than Earth

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It’s a Small World: Kepler Spacecraft Discovers First Known Earth-Size Exoplanets