Planets in transit: evolution models, compositions and statistics

     
 

 

With a steadily growing number of known transiting planets and the realisation that no less than 10,000,000 planets transit stars in our Galaxy alone, a lot is to be learned from the present discoveries and much more is to be expected for the future. The vast majority of transiting planets known today are gaseous giant planets. For them, a proper knowledge of their evolution is crucial because how they contract directly affects what we can infer on their composition. However, uncertainties abound: on the equations of state to be used, on the opacities in little known pressure-temperature regimes, and on physical processes themselves, in particular heat dissipation due to stellar tides. Taken individually, these uncertainties generally prevent from infering the planet's global composition. For example, some planets are found to be larger than possible for a hydrogen- helium planet of that age, mass and irradiation level when calculated with standard evolution models. However, by using the same hypotheses for all planets, it is then possible to infer model-dependent global planetary compositions and relate it to other observables. It is thus found that the "metallicity" of stars and that planets are correlated, giant planets orbiting close to very metal-rich stars being found to possess up to ~100 Earth masses in heavy elements. I will discuss how further insight can be obtained from statistical models of the star and planet populations and their comparison to transiting surveys. I will finally present a few intringuing planets, in connection to the CoRoT mission.

Tristan Guillot