<p>This undated handout artist rendering provided by NASA shows Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. It is the first planet that NASA's Kepler mission has confirmed to orbit in a star's habitable zone -- the region around a star where liquid water, a requirement for life on Earth, could persist.</p>
December 6, 2011
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December 6, 2011 8 p.m.