Many Earths Out There: 2326 Potential Alien Worlds and Counting 2011
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Virtually all of the alien planet candidates discovered by NASA's Kepler space telescope may turn out to be the real deal, a new study suggests. Researchers announced Monday, Dec. 5, that Kepler has detected 2326 potential alien worlds in its first 16 months of operation, including 48 in their stars' habitable zones that just-right range of distances that could allow liquid water, and maybe even life, to exist. While the vast majority of these planets have yet to be confirmed, 99.9 percent or so may end up making the cut, according to the study. That would mean Kepler's finds to date would more than quadruple the number of known alien worlds, which currently stands at a little more than 700. Kepler detects alien planets by what's known as the transit method. The instrument watches for the tiny, telltale dips in a star's brightness caused when a planet crosses the face of or transits it from Kepler's perspective, blocking some of the star's light. Kepler needs to witness three transits to flag a potential alien planet. These candidates are then confirmed by follow-up observations, usually by large ground-based telescopes. Time on such big instruments is tough to come by; to date, about 30 of Kepler's 2326 potential exoplanets have been confirmed. Most of the brightness dips Kepler detects are indeed caused by planets, researchers think. But there is a chance some candidates are false positives. For example, a dip could also be caused by an eclipsing binary, a second star ...