After a year that brought the discovery of several planets similar to our own, some astronomers are claiming that 2013 is the year we will discover a true alien Earth.
More than 800 exoplanets have been found since 1995, and some of them are Earth-like in mass and size. But these distant cousins all orbit their host stars too closely to be inhabitable.
By measuring the telltale dip in the brightness of a star as a planet passes in front it, the Kepler Space Telescope can identify a new planet after three transits. So far, it’s focused the search on the ones quickest to confirm—those closest to the star with smaller, more frequent orbits.
But as time passes, Kepler is spotting more distantly orbiting bodies, and now scientists say that in the coming year they are confident they will discover a rocky, wet planet in the "Goldilocks zone” around the star, where temperatures are just right for life.