HD 85512 b is a rocky planet about 3.6 times the mass of Earth, located right at the edge of its star's habitable zone. That means it's capable of supporting life... and the early results suggest it's a very real possibility.
It's one of 50 new exoplanets discovered by the HARPS team at the La Silla Observatory in Chile, which is part of the European Southern Observatory. This is the largest number of exoplanets ever discovered at one time, and it brings the number of confirmed exoplanets up to about 600. (The Kepler Space Telescope discovered 1,200 exoplanet candidates at one time, as opposed to confirmed planets.)
Recently, HARPS offered some of the most damning evidence yet that Gliese 581 g, the first rocky exoplanet discovered in its planet's habitable zone, does not, in fact, exist. That's the culmination of months of controversy about the planet's status, and it leaves Gliese 581 d as the only known potentially habitable exoplanet, albeit one that enjoys far less ideal conditions than Gliese 581 g theoretically would have had.
But HARPS has found us a new planet to make up for the loss of Gliese 581 g, which could well be habitable. HD 85512 b is one of five planets discovered by the HARPS team whose mass is less than five times that of Earth. That puts it in the Super-Earth category, a type of rocky planet that is up to twenty times the mass of Earth. Although there are no such planets in our own solar system, they appear to be very common elsewhere in the galaxy.
HD 85512 b is the only one of these five rocky planets to be located in its star's habitable zone. The preliminary measurements suggest that its average surface temperature could be 77 degrees Fahrenheit, which would give it a very pleasant Mediterranean climate — assuming it's otherwise Earthlike.
Obviously, that's a very, very big assumption, but if that temperature figure is accurate, it implies that the planet has about 50% cloud cover. Again, that isn't proof of the presence of water, let alone life — there's plenty of other things that could compose those clouds, or the figures could just be wrong — but it's certainly a tantalizing possibility.
Indeed, the HARPS team itself is feeling pretty confident about the possibilities of HD 85512 b. In their paper announcing the finding, Lisa Kaltnegger and her co-authors declare:
We find that HD 85512 b could be potentially habitable if the planet exhibits more than 50% cloud coverage. HD 85512 b is, with Gl 581 d, the best candidate for exploring habitability to date, a planet on the edge of habitability.
This is hopefully just the beginning, for both HD 85512 b and the HARPS team. The researchers explain that these 50 newly discovered exoplanets offer some of our best opportunities yet to provide detailed analyses of these faraway worlds, and we could soon gain unprecedented levels of insight into the composition and structure of planets located many light-years away.
arXiv via ESO. Artist's conception of HD 85512 b by ESO/M. Kornmesser.