“the first serious ‘water world’ candidate..”

Kepler’s seen ‘first light’ and is set to begin the search for ET’s potential home. Meanwhile, the JENAM conference has heard news of the lightest exo-planet yet at 1.9 Earth mass, inferred from old-stylee gravitational effects using the HARPS spectrograph attached to the 3.6-metre ESO telescope at La Silla, Chile – press release here. They’ve been uncovering a harvest of super-Earth’s there. The new planet is orbiting an old friend, Gliese 581, and it turns out there may be a better candidate for life orbiting that particular dwarf star than Gliese 581c noted here. Video statement from Professor Michael Mayor here. From the ESO press release.

Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. From previous observations — also obtained with the HARPS spectrograph at ESO’s La Silla Observatory and announced two years ago — this star was known to harbour a system with a Neptune-sized planet (ESO 30/05) and two super-Earths (ESO 22/07). With the discovery of Gliese 581 e, the planetary system now has four known planets, with masses of about 1.9 (planet e), 16 (planet b), 5 (planet c), and 7 Earth-masses (planet d). The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days. “Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,” says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. ӑd’ could even be covered by a large and deep ocean — it is the first serious ‘water world’ candidate,” continued Udry.