The atmospheric metallicities of gas giant exoplanets
Thursday 5 July, 14:40
A central prediction made by the core accretion model of planetary formation is that atmospheric metallicity should increase with decreasing planet mass. This prediction is born out in the Solar System, where a clear anti-correlation between planet mass and atmospheric metallicity is observed. Exoplanets can thus be used to determine whether this trend is a universal outcome of the planet formation process.
I present a portfolio of observational projects for which we have recently succeeded in measuring the atmospheric metallicities of gas giant exoplanets. These projects use diverse and complementary approaches to retrieve the metallicity, such as measuring the molecular abundances and using novel tracers (e.g. alkali metals and hydrides). I present the breakthroughs but also the main challenges to overcome while making these measurements. When combined together, our findings on the measurements of atmospheric metallicity allow us to make quantitative comparisons amongst exoplanets, with the Solar System planets, and to test predictions of planet formation models. The first results from these projects offer the tantalizing suggestion that the trend seen in the Solar System is also discernable in extrasolar systems.