The Formation of Planetary Proto-Atmospheres

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Context: During their formation, proto-planets become massive enough to gravitationally bind gas from the disks they are born in. For giant planets such as Jupiter, the rocky or icy core becomes so massive that it triggers a runaway accretion of gas. Smaller planets such as Neptune, Earth, and super-Earths instead are only able to bind a limited amount of gas. Hence, the physical details of gas accretion in the disk-embedded phase yields a distinctive attribute of the observed planetary distribution.Methods: The formation and early evolution of planetary proto-atmospheres, embedded in their natal disk, shall be investigated using state-of-the-art radiation-hydrodynamical modeling. We will include both - the hydrodynamic as well as the thermodynamic - effects in two- and three-dimensional simulations. Moreover, conducting these simulations in a local frame in planeto-centric spherical coordinates with the planet at the origin of the grid, allows us to resolve the physics of the atmospheric build-up in very high resolution. Initial and boundary conditions for the local frame, representing the large-scale disk flow, will be extracted from preceding global disk simulations, performed in spherical coordinates with the host star at the origin of the grid.Aims: We will extract the atmospheric mass, its rotation profile, and the radiative cooling as well as the gas replenishing timescale as a function of the core, the disk, and the optical properties of the surrounding gas and dust. From that, we investigate under which condition the forming atmosphere approaches a steady state or quasi-stationary system. Additionally, we can specifically test the hypothesis, whether the thermal heat stored in the core and/or the asymmetric structure of the gas flow prevents the atmospheres of super-Earths from collapsing. Resume: The hydrodynamics and thermodynamics of planetary proto-atmospheres will be investigated in direct high-resolution modeling of their formation and early evolution. Following a local approach allows us to determine the small-scale physics in unprecedented detail. The research outcome will shed light on the formation and stability of super-Earth atmospheres.