Despite Early Success, Kepler Far from Finding Another Earth

摘要

NASA's Kepler mission already has found more than 1,200 potential alien planets, but it will likely be a few years before it hauls in the exoplan-et "holy grail" - an alien Earth. Scientists announced Feb. 2 that the Kepler space telescope spotted 1,235 exoplanet candidates in its first four months of operation, including 54 that orbit their host stars in the so-called habitable zone, that just-right range of distances that allow liauid water to exist.