NOTE:TIME CHANGE: 3-4pm: Learning from transits: evolutions & compositions of giant exoplanets

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• Tristan Guillot (Observatoire de la Cote d'Azur, Nice, France)
• Monday 14 June 2010, 15:00-16:00
• MR14, DAMTP, Pav. F.

If you have a question about this talk, please contact Laurène Jouve.

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. In principle, the determination of their mass, size, orbital properties and age through combined radial velocimetry, photometric transit observations and spectroscopy allows a determination of 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. In particular, I will show that models of CoRoT-2 imply that both the star and planet are very young, and that the inflated planetary size can only be explained through a dramatic recent event.

This talk is part of the DAMTP Astrophysics Seminars series.

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