Contributed Talk - Splinter Exoplanets
Thursday, 24 September 2020, 12:15 (virtual room D)
The Recycling of Planetary Proto-Atmospheres
T. Moldenhauer, R. Kuiper, W. Kley, C. W. Ormel
Universität Tübingen, Germany; Tsinghua University, China
Protoplanets formed by core accretion can become massive enough to accrete gas from the disk they are born in. If the planetary proto-atmosphere exceeds a critical mass, runaway gas accretion starts and the planetary atmosphere collapses into a gas giant. In recent years, many close-in super-Earths have been observed which raises the question on how they avoided becoming hot Jupiters. We investigate the recycling hypothesis as a possible mechanism to avoid the collapse of the atmosphere. We use three-dimensional radiation-hydrodynamics to simulate the formation of proto-atmosphere in the local frame around the planet. In post-processing we use tracer particles to calculate the shape of the atmosphere and determine the non-uniform recycling timescale in a quantitative manner. Our simulations converge to a quasi-steady state where the velocity field of the gas does not change anymore. For the parameter we space explored, a = 0.1 au, M_c ∈ [1, 2, 5] M_Earth , we find that recycling of the atmosphere counteracts the collapse by preventing the gas from cooling efficiently.