Homing in on another Earth

摘要

The identification of the closest analogue of Earth so far, orbiting another star, suggests that small planets are common, and that the discovery of a candidate habitable planet in an alien star system could be just around the corner. In the hunt for planets around stars other than the Sun, astronomers' primary objective is to find a planet that is teeming with life. A milestone on the path to this goal is the discovery of Earth-sized planets orbiting their parent stars in the 'habitable zone' - the range of distances from the star at which the temperature would be just right for liquid water to be present on a planet's surface.