ESO – ESO 15/09 – Lightest exoplanet yet discovered.
The European Southern Observatory has used its Very Large Telescope (a bunch of telescopes ganged together to form a huge optical interferometer) to refine the orbits of the known planets around Gliese 581, b,c & d, and to discover a new planet, e, in a 3.15 day orbit. Planet e is surprisingly light-weight, just 1.9 Earth masses, but it’s way too hot for Life-As-We-Know-It. However after newly reining the planets’ orbits Planet d, massing just 7 Earth masses, is now on the outer edge of the star’s habitable zone. It would then be the nearest thing to a habitable planet yet discovered.
A habitable planet? It’s likely too small to be much of a gas giant. It’s probably an Ocean Planet, which would imply – paradoxically – that it’s too wet for much of a biosphere. Maybe. We don’t yet know everything Life can do, but planets wrapped in thousands of kilometres of high-pressure ice (“red hot ice”) aren’t likely to have life-sustaining geology.
But it’s a step in the right direction…