Protostars and Planets VI, Heidelberg, July 15-20, 2013
Photophoresis boosts formation of giant planets!
Teiser, Jens (Universitšt Duisburg-Essen)
Dodson-Robinson, Sarah (University of Texas at Austin)
Giant planets consist of a solid core, which grows by accretion of planetesimals. Once the solid core is massive enough, also gas is accreted directly. Planetesimals, which are accreted are subject to severe erosion within the planetary atmosphere. Together with primordial dust, which is brought into the atmosphere by gas accretion, this leads to an increasing amount of dust in the atmosphere. This dust increases the opacity oft he atmosphere, which then absorbs thermal radiation from the inner parts of the growing planet. This automatically leads to increasing temperatures and to an increasing gas pressure in the inner part, so gas accretion is strongly reduced. With this reduced accretion rate the formation timescales given by the lifetime of protoplanetary disks are difficult to explain. Within this study we present photophoresis as a mechanism, which pushes dust particles outward and clears the inner parts of the atmosphere from dust. Thermal radiation from the inner part heats the dust particles, so a temperature gradient forms on their surfaces. As they are in a gaseous environment, this directly leads to a photophoretic acceleration, which can exceeds gravity by an order of magnitude. This mechanism helps to clear the inner part of the planetary atmosphere from dust aggregates. The inner part then can cool efficiently via thermal radiation, which accelerates the gas accretion significantly.
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