Dix Planetary Science Seminar
The increasingly large number of well-characterized giant exoplanets presents a valuable dataset for studying their physics. I will show that by modelling the whole population as an ensemble, I have inferred their compositional and thermal properties. Of particular interest is the bulk metallicity of the planet; these act as an upper limit on the atmospheric metallicity, which can be observationally measured through spectroscopy. Better yet, a comparison of the bulk and atmospheric metallicities will suggest the degree to which the planet is compositionally stratified. Modelling the radii of the giant planet population as an ensemble can also shed light on the cause of the hot Jupiter radius anomaly problem. I will show that the heating in hot Jupiters must decline as a fraction of incident flux for very high equilibrium temperatures, consistent with the Ohmic dissipation model. However, contrary to this model's predictions, I will also show that these objects appear to reinflate quickly as their main-sequence stars brighten. This reinflation also rules out delayed cooling explanations of the radius anomalies. These observations therefore do not decisively point to any one model, and further theoretical development is needed. To that end, these results will be important tests for future or refined proposed explanations.