Project C
Giants under the telescope: characterizing the atmospheres of gas giant exoplanets through direct spectroscopy
Jens Kammerer (ESO), Thomas Winterhalder (ESO), Claudia Toci (ESO), Lara Piscarreta (ESO)
What can we learn about a giant planet atmosphere from direct imaging spectroscopy? And what will remain hidden under their thick gas envelopes? These are the main questions that this project aims to address.
While the number of known exoplanets approaches the bar of 6'000, the origin of massive gas giants (so-called super-Jupiters) on widely separated orbits remains an open question. Direct observations of young exoplanets provide critical tests for theoretical models of planet formation and early evolution. In particular, the atmospheric composition of young gas giants carries chemical imprints of the planet formation history. Fitting atmosphere models to the observed planet spectra can, besides constraining the planet's bulk properties such as effective temperature and surface gravity, provide insights into the abundance of molecules like water, CO, methane, and CO2. The inferred parameter values can then be compared to predictions from theoretical models to potentially learn something about the planet's formation.
In particular, the information content of gas giant planet spectra from the GRAVITY instrument will be investigated. For this purpose, the public "species" atmospheric modeling toolkit will be employed to fit different grids of models to the observed GRAVITY spectra and infer the bulk properties (effective temperature, surface gravity, metallicity, extinction) of the planets' atmospheres. The consistency between different grids of models will be analyzed. In the next step, additional archival spectra and photometry from other instruments will be collected (where available) and included in the atmospheric model fits, in order to investigate whether the inferred bulk properties change. This exercise will reveal which parameters can be constrained by GRAVITY alone, and which parameters require data over a broader wavelength range.