spacetoday.net: Small exoplanet discovered

Posted: Thu, Jan 26, 2006, 7:21 AM ET (1221 GMT)
Small icy exoplanet illustration (ESO)

Astronomers have discovered a distant extrasolar planet with a mass only five times that of the Earth. In a paper published in Thursday's issue of the journal Nature, an international team of astronomers reported that they have found a planet orbiting the star OGLE-2005-BLG-390L, about 20,000 light-years from Earth near the center of the Milky Way galaxy. The star created a "microlensing" event when it passed between the Earth and a more distant star; its gravity magnified the light of that distant star as seen from Earth. Astronomers found a "defect" in the characteristic smooth lightcurve of the microlensing event, which astronomers believe is caused by a planet orbiting the microlensing star. Based on that blip in the lightcurve, astronomers believe that the exoplanet weighs about five times the mass of the Earth, and orbits OGLE-2005-BLG-390L at a distance of about 3 AU. While some reports described the planet as "Earth-like", astronomers believe the planet is more likely an icy world, a giant version of Pluto. The exoplanet is the among the smallest discovered to date. The serendipitous discovery leads some researchers to conclude the small exoplanets may exist around many stars.