Invited Talk - Plenary

Wednesday, 13 September 2023, 09:30   (H 0104 / virtual plenum)

Theory of Exoplanet atmospheres

Kevin Heng
LMU München

The detection of exoplanets is currently an established subfield of astrophysics and astronomy. With the deployment of the James Webb Space Telescope, the focus on atmospheric characterization of exoplanets has intensified as the data are now good enough to decisively confront theory. In the current talk, I will discuss two frontier topics: the interpretation of spectra, using Bayesian and machine learning methods, in order to extract chemical abundances; and the interpretation of these inferred abundances in the context of abiotic chemical processes. The first part of the talk covers Bayesian retrieval methods, as well as a recent mathematical solution for reflected-light phase curves that enables rapid inversions to be performed. The second part of the talk discusses geochemical outgassing, which sources the atmospheres of small exoplanets (super Earths and sub-Neptunes). Future claims of biosignatures cannot be made without a firm understanding of false positives, which are provided by geochemical outgassing. Ultimately, a combination of judiciously applying Bayesian retrieval methods (while paying close attention to scattering by clouds/hazes) and understanding the retrieved chemical abundances in the context of geochemistry is critical for any claimed detection of biochemistry. Fostering close collaboration between astrophysicists and geoscientists — for theory, simulation and lab experiments — will be necessary in the coming years.