Global 3D radiation-hydrodynamic simulations of gas accretion: Opacity-dependent growth of Saturn-mass planets

Abstract

The full spatial structure and temporal evolution of the accretion flow into the envelopes of growing gas giants in their nascent discs is only accessible in simulations. Such simulations are constrained in their approach of computing the formation of gas giants by dimensionality, resolution, consideration of self-gravity, energy treatment and the adopted opacity law. Our study explores how a number of these parameters affect that measured accretion rate of a Saturn-mass planet. We present a global 3D radiative hydrodynamics framework using the FARGOCA-code. The planet is represented by a gravitational potential with a smoothing length at the location of the planet. No mass or energy sink is used, instead luminosity and gas accretion rates are self-consistently computed. We find that the gravitational smoothing length must be resolved by at least 10 grid cells to obtain converged measurements of the gas accretion rates. Secondly, we find gas accretion rates into planetary envelopes compatible with previous studies, and continue to explain those via the structure of our planetary envelopes and their luminosities. Our measured gas accretion rates are formally in the stage of Kelvin-Helmholtz contraction due to the modest entropy loss that can be obtained over the simulation time-scale, but our accretion rates are compatible with those expected during late run-away accretion. Our detailed simulations of the gas flow into the envelope of a Saturn-mass planet provides a framework for understanding the general problem of gas accretion during planet formation and highlights circulation features that develop inside the planetary envelopes. Those circulation features feedback into the envelope energetics and can have further implications for transporting dust into the inner regions of the envelope.

The eccentricity distribution of giant planets and their relation to super-Earths in the pebble accretion scenario

“…We follow here the approaches of our previous works (Bitsch et al 2015b(Bitsch et al , 2019. Even though gas accretion rates are heavily debated in the literature (Ayliffe & Bate 2009;Machida et al 2010;D'Angelo & Bodenheimer 2013;Schulik et al 2019) and span several orders of magnitude in range, we keep these rates as in our previous works to allow a better comparison.…”

Influence of planetary gas accretion on the shape and depth of gaps in protoplanetary discs

“…However, it seems that 100% efficiency is not realistic in such a case. Schulik et al (2019) showed that gas accretion does not start from the full Hill sphere but only from a fraction of it. The accreted mass fraction increases closer to the planet but it does not accrete 100% of the gas in the vicinity.…”

“…Gas accretion rates onto planets are not very precisely constrained. In the runaway gas-accretion phase accretion, rates Ayliffe & Bate 2009;Machida et al 2010;Schulik et al 2019). Recent studies claim that the accretion rates could be even smaller; Lambrechts et al (2019) found that the mass flux through the envelope is different from the gas accretion rate, therefore, even if the mass flux is on the order of 10 −5 M J yr −1 , the gas accretion rate is actually 10 to 100 times smaller.…”

“…The planet then enters a runaway growth phase of gas accretion during which we can assume that only gas is accreted (Hubickyj et al 2005;Lissauer et al 2009). Previous studies have described how gas accretion can be modeled in different frameworks: in 2D with and without migration (Crida & Bitsch 2017;Kley 1999) or in 3D (Ayliffe & Bate 2009;Machida et al 2010;D'Angelo & Bodenheimer 2013;Lambrechts et al 2019;Schulik et al 2019). These complex hydrodynamical simulations are needed to understand each phase of gas accretion.…”

“…(D'Angelo et al 2003;Ayliffe & Bate 2009;Machida et al 2010;Tanigawa & Tanaka 2016;Schulik et al 2019; …”