scientists have found two major discoveries in the search for other moon - containing planets . british astronomers say they have investigated the smallest known mercury - like exoplanet orbiting a living asteroid called gliese 581 e and immediately discovered that a nearby planet called planet 581 d , discovered in 2007 , is in the much - after ' habitable region ' . astronomers initially suggest there is a possibility that 581 d could have liquid oceans on its surface , calling the find " extraordinary . " " the holy monty of current exoplanet research is the detection of a stony , earth - scale asteroid in the ' uninhabitable zone ' , " reported astrophysicist at britain ' s geneva university , eric town . astronomers know 581 e is 20 . 5 dark years away from earth and that it ' s roughly 1 . 9 thirds larger than moon , making it the smallest exoplanet discovered to date . it was found using the moderate accuracy radial acceleration planet searcher ( harps ) .
Michel Mayor is the discoverer of the High Accuracy Radial Velocity Planet Searcher.