At Least 17 Billion Earth-Size Alien Planets Inhabit Milky Way | LiveScience - 0 views
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The Milky Way
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Only 5 percent of stars harbor a gas giant with an orbital period of 400 days or less, researchers said.
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Kepler detects alien worlds by noting the telltale dips in brightness caused when planets cross the face of — or transit — their parent stars from the instrument's perspective.
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minimum of 17 billion small, rocky alien worlds, or an Earth-size planet around one of every six stars.