The Formation of Planetary Proto-Atmospheres
Final Report Abstract
Context: Planets form in circumstellar disks of dust and gas. Due to their gravity, these planets bind the surrounding gas in the form of a planetary atmosphere. In the case of very massive planets, the attraction leads to a rapid increase in gas mass and Jupiter-like gas giants are formed. Lighter planets, such as our Earth or Neptune, do not trigger such a collapse of their environment and only bind a small amount of gas in their atmosphere in comparison. This observational characteristic of a planet’s atmosphere therefore allows conclusions to be drawn about its formation history in the circumstellar disk. Methods: We have investigated the formation and early evolution of planetary atmospheres in numerical radiative-hydrodynamic simulations, adequately accounting for both the hydrodynamic and thermodynamic processes of atmosphere formation. In order to achieve a very high resolution of atmosphere formation, we concentrated on a local area around the planet in the simulations and used a planet-centered grid in spherical coordinates. The simulation data were further processed using a particle trajectory module to determine the recycling timescales prevailing locally in the different regions of the atmosphere. Aims: We determine the mass of the forming atmosphere and its rotational profile as well as its cooling time and the timescale of the dynamic mixing of the atmosphere and the disk as a function of the planetary and disk parameters and the optical properties of the environment. In addition to the question of whether the atmosphere assumes a (quasi-)stationary configuration, we were able to check whether the thermal energy prevents the forming atmosphere from collapsing. Results: The systems studied settled into a steady state, maintaining the planet’s proto-atmosphere and preventing it from collapsing into a gas giant. The studies revealed that the entire protoplanetary atmosphere undergoes recycling, with no regions where gas is never exchanged with the circumstellar disk. When the core mass is above two Earth masses, the atmosphere becomes turbulent, enhancing recycling. The atmosphere’s size increases roughly proportional to the core mass to power 2/3, with the ratio of the atmosphere to core mass scaling linearly with the protoplanetary core mass. The headwind affects the atmosphere’s size and mass slightly, but opacity significantly impacts the atmosphere’s final size and mass. With larger separation to the host star, recycling becomes less efficient and runaway gas accretion becomes feasible at separations of 3 to 5 au.
Publications
-
Steady state by recycling prevents premature collapse of protoplanetary atmospheres. Astronomy & Astrophysics, 646, L11.
Moldenhauer, T. W.; Kuiper, R.; Kley, W. & Ormel, C. W.
-
Atmospheric Recycling Prevents Premature Collapse of Protoplanetary Atmospheres of Close-in Super-Earths and Mini-Neptunes. Dissertation, Eberhard-Karls-Universität Tübingen.
Moldenhauer, Tobias Walter
-
Recycling of the first atmospheres of embedded planets: Dependence on core mass and optical depth. Astronomy & Astrophysics, 661, A142.
Moldenhauer, T. W.; Kuiper, R.; Kley, W. & Ormel, C. W.
-
Recycling of Planetary Proto-Atmospheres. Copernicus GmbH.
Moldenhauer, Tobias; Kuiper, Rolf; Kley, Wilhelm & Ormel, Chris
