The first transiting hot Neptune, and the first transiting planet around a red dwarf has been found. Gliese 436 b (interestingly enough, it was one of the first hot Neptunes to be discovered) has a radius very similar to that of Neptune, which suggests the planet is mainly icy, with a thin hydrogen-helium envelope: in other words, the planet is a hot Neptune-analogue, rather than a super-Earth or a mini-Jupiter.

The planet is slightly more massive and rather closer to its star than the innermost planet of the Gliese 581 system. It probably formed further out in its system and migrated inwards. If the planets of Gliese 581 formed in the same way, the outer two planets could be "ocean planets". Though I strongly suspect that any ocean on the so-called "habitable super-Earth" Gliese 581 c will be too hot to be liquid.

Further info at systemic.


Edited by chaos