How like Earth are alien planets?
AT LAST we are seeing big rewards in the hunt for “super-Earths” – rocky alien worlds a few times more massive than our own. That was the verdict from a landmark meeting of astronomers last week which saw the unveiling of a huge haul of new exoplanets in our galaxy. “This really changes things,” says Sara Seager of the Massachusetts Institute of Technology, who attended the International Astronomical Union meeting in Boston. “It marks the beginning of the detailed exploration of super-Earths.” The new discovery of a large number of small planets suggests that they are abundant in our galaxy, and outnumber Jupiter-sized giants by 3 to 1. This contrasts with the nearly 300 alien planets previously discovered, of which the vast majority are Jupiter-like gas giants. Only a dozen or so are low-mass planets: either Neptune-like ice-worlds or rocky planets like Earth. Now researchers on the High Accuracy Radial Velocity Planet Searcher (HARPS) survey based at the European Southern Observatory