Planetary atmospheres under the evolving star

Supervisor: Manuel Güdel (Department of Astrophysics) in collaboration with Colin Johnstone, Kristina Kislyakova, Sudeshna Boro Saikia (Department of Astrophysics)

Funding Situation: supervisor has secured funding

Project outline: The origin of habitability on (exo-)planets has its roots in the early stages of planet formation in gas and dust disks around forming stars. If a planet grows to more than ~0.1 Earth masses, it picks up a gas envelope from the disk. This primordial atmosphere is not habitable and needs to be removed again. For Earth-like planets, gas accretion is limited by the planetary growth timescale and the disk lifetime. Once the disk is dispersed, the planetary envelope starts eroding driven by stellar high-energy irradiation. This erosion depends on the planetary orbit and the stellar activity evolution, which itself depends on the stellar rotation evolution. Impacting small bodies also thermally modify the gas envelope due to ablation and dust production. Under what initial conditions will this primordial atmosphere successfully disperse? What timescales of the different processes matter and how long should they be? We will study various atmospheric evolutionary tracks considering the effect of planet growth, impacting small bodies, and different evolutionary tracks of stellar activity with a variety of atmospheric compositions. The work will make use of advanced numerical simulation codes involving some programming. This project will allow us to assess under which combined conditions a rocky planet can end up as an Earth-like planet with a thin secondary atmosphere, or as an envelope surrounded mini-Neptune.