Planet Detection Around M Dwarfs: New Constraints on Planet Formation Models
Résumé
The dependence of planetary statistics on the physical conditions during the initial stages of the system (i.e. in the proto-planetary disk) represent an essential constraint on planetary formation mechanisms. The planets orbiting M dwarfs were formed in a lower-mass disk, with an ice boundary much closer to the star, and a longer orbital period (for the same separation) than the planets formed around solar-type stars. Planetary formation is extremely sensitive to all three parameters, and the relative statistical properties of planets around G dwarfs and very low mass stars therefore represent a very sensitive diagnostic. In this talk we will present the first results of a very sensitive search for planets around southern M dwarfs with the HARPS spectrograph (as part of the HARPS GTO program). The northern counterpart of the survey will be conducted with SOPHIE at OHP, within the SOPHIE Exoplanets Consortium. These first results suggest that that planets around M dwarfs have lower mass than around solar type stars.