Thermodynamics of giant planet formation: shocking hot surfaces on circumplanetary discs

Szulágyi, J.; Mordasini, Christoph (2017). Thermodynamics of giant planet formation: shocking hot surfaces on circumplanetary discs. Monthly notices of the Royal Astronomical Society - letters, 465(1), L64-L68. Oxford University Press 10.1093/mnrasl/slw212

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The luminosity of young giant planets can inform about their formation and accretion history. The directly imaged planets detected so far are consistent with the ‘hot-start’ scenario of high entropy and luminosity. If nebular gas passes through a shock front before being accreted into a protoplanet, the entropy can be substantially altered. To investigate this, we present high-resolution, three-dimensional radiative hydrodynamic simulations of accreting giant planets. The accreted gas is found to fall with supersonic speed in the gap from the circumstellar disc's upper layers on to the surface of the circumplanetary disc and polar region of the protoplanet. There it shocks, creating an extended hot supercritical shock surface. This shock front is optically thick; therefore, it can conceal the planet's intrinsic luminosity beneath. The gas in the vertical influx has high entropy which when passing through the shock front decreases significantly while the gas becomes part of the disc and protoplanet. This shows that circumplanetary discs play a key role in regulating a planet's thermodynamic state. Our simulations furthermore indicate that around the shock surface extended regions of atomic – sometimes ionized – hydrogen develop. Therefore, circumplanetary disc shock surfaces could influence significantly the observational appearance of forming gas giants.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Mordasini, Christoph


500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering




Oxford University Press




Janine Jungo

Date Deposited:

30 Jun 2017 09:36

Last Modified:

30 Jun 2017 09:36

Publisher DOI:





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