SIMBAD references

2017ApJ...834..149B - Astrophys. J., 834, 149-149 (2017/January-2)

The evolution of gas giant entropy during formation by runaway accretion.


Abstract (from CDS):

We calculate the evolution of gas giant planets during the runaway gas accretion phase of formation, to understand how the luminosity of young giant planets depends on the accretion conditions. We construct steady-state envelope models, and run time-dependent simulations of accreting planets with the code Modules for Experiments in Stellar Astrophysics. We show that the evolution of the internal entropy depends on the contrast between the internal adiabat and the entropy of the accreted material, parametrized by the shock temperature T0 and pressure P0. At low temperatures (T0 300-1000 K, depending on model parameters), the accreted material has a lower entropy than the interior. The convection zone extends to the surface and can drive a high luminosity, leading to rapid cooling and cold starts. For higher temperatures, the accreted material has a higher entropy than the interior, giving a radiative zone that stalls cooling. For T0 2000 K, the surface-interior entropy contrast cannot be accommodated by the radiative envelope, and the accreted matter accumulates with high entropy, forming a hot start. The final state of the planet depends on the shock temperature, accretion rate, and starting entropy at the onset of runaway accretion. Cold starts with L 5×10–6 L require low accretion rates and starting entropy, and the temperature of the accreting material needs to be maintained close to the nebula temperature. If instead the temperature is near the value required to radiate the accretion luminosity, 4πR2σT04∼(GM{dot}M/R), as suggested by previous work on radiative shocks in the context of star formation, gas giant planets form in a hot start with L∼10–4 L.

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): planets and satellites: formation - planets and satellites: gaseous planets - planets and satellites: physical evolution - planets and satellites: physical evolution

Simbad objects: 17

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