So the "possibly habitable planet" probably isn't, as a number of people pointed out,
but the outer planet in the system may be, given some optimistic albedo and greenhouse assumptions
There was an interesting discovery last month, of a "super-Earth" formally within the habitable zone of a nearby star.
As a number of people pointed out, the habitability assumption was not really consistent, it looked more likely to runaway to a Venus like state if it had water and atmosphere.
Now there is a short formal analysis, but they also point out that while GJ581c may not be habitable, the outer planet, GJ581d may be.
Win one, lose one.
What a load of *%!@. Check out they paragraph where they say, "Valencia et al. show that super earths would have solid cores, but we assume a liquid one anyway with an unreferenced, unwritten other calculation."
Note also that they assume carbon as CO2, and a silicate weathering cucle, despite the fact that in our system, every body outsode th efrost line from a comet to jupiter has an fO2 that supports organic, no fully oxidized carbon.
Finally, why do people scale earth up by a factor of 8, instead of simply halving Uranus?
On a quasi-scientific note, does anyone know the C-O ratio of the host star? That will determine the O activity of the solar nebula, which in turn will govern the relative condensation temperatures for metals, silicates, and volitiles.