spacetoday.net: New study indicates two potentially Earth-like exoplanets don't exist

Posted: Sat, Jul 5, 2014, 9:53 AM ET (1353 GMT)
Gliese 581g illustration (Lynette Cook)

A pair of previously-discovered extrasolar planets that had the potential to be Earth-like may not actually exist, astronomers reported this week. Astronomers first reported the discovery of the planets, named Gliese 581d and g, in 2007 and 2010 respectively, using radial velocity observations of the red dwarf star Gliese 581 about 20-light-years away. The size and orbits of these "super-Earth" exoplanets indicated that they could be potentially habitable. However, analysis of radial velocity data by astronomers at Penn State Univ. and the Univ. of Texas Austin failed to detect those two planets, although it did confirm three other planets previously known to orbit the star. The new analysis took into account stellar activity, which can also cause shifts in spectral lines like that caused by the Doppler shift induced by orbiting planets. Astronomers believe the signals previously linked to Gliese 581d and g are instead simply stellar activity.