spacetoday.net: Rocky exoplanet discovered

Posted: Tue, Jun 14, 2005, 8:27 AM ET (1227 GMT)
Gliese 876 rocky exoplanet illus. (NSF)

Astronomers announced Monday that they have found the smallest extrasolar planet yet orbiting a Sun-like star, a planet small enough it is most likely a larger version of the Earth. The planet orbits the star Gliese 876 at a distance of less than four million kilometers, completing one orbit in just under two days. Scientists estimate that the planet weights as little as 5.9 Earth masses, making it smaller than any other exoplanet found to date around a Sunlike star. That mass is low enough that astronomers believe that the planet must be a rocky, terrestrial world like the Earth and the other inner planets in our solar system, since it is not massive enough to maintain the thick atmosphere of a gas giant. Astronomers credit improvements to a spectrograph at the Keck Observatory for providing the key confirmation of the planet's existence; they believe that such instruments will allow astronomers to detect Earth-sized planets in the next several years.