Self-gravitating planetary envelopes and the core-nucleated instability. (arXiv:1909.13036v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bethune_W/0/1/0/all/0/1">William Béthune</a>
Planet formation scenarios can be constrained by the ratio of the gaseous
envelope mass relative to the solid core mass in the observed exoplanet
populations. One-dimensional calculations find a critical (maximal) core mass
for quasi-static envelopes to exist, suggesting that envelopes around more
massive cores should collapse due to a `core-nucleated’ instability. We study
self-gravitating planetary envelopes via hydrodynamic simulations,
progressively increasing the dimensionality of the problem. We characterize the
core-nucleated instability and its non-linear evolution into runaway gas
accretion in one-dimensional spherical envelopes. We show that
rotationally-supported envelopes can enter a runaway accretion regime via polar
shocks in a two-dimensional axisymmetric model. This picture remains valid for
high-mass cores in three dimensions, where the gas gravity mainly adds up to
the core gravity and enhances the mass accretion rate of the planet in time. We
relate the core-nucleated instability to the absence of equilibrium connecting
the planet to its parent disk and discuss its relevance for massive planet
formation.
Planet formation scenarios can be constrained by the ratio of the gaseous
envelope mass relative to the solid core mass in the observed exoplanet
populations. One-dimensional calculations find a critical (maximal) core mass
for quasi-static envelopes to exist, suggesting that envelopes around more
massive cores should collapse due to a `core-nucleated’ instability. We study
self-gravitating planetary envelopes via hydrodynamic simulations,
progressively increasing the dimensionality of the problem. We characterize the
core-nucleated instability and its non-linear evolution into runaway gas
accretion in one-dimensional spherical envelopes. We show that
rotationally-supported envelopes can enter a runaway accretion regime via polar
shocks in a two-dimensional axisymmetric model. This picture remains valid for
high-mass cores in three dimensions, where the gas gravity mainly adds up to
the core gravity and enhances the mass accretion rate of the planet in time. We
relate the core-nucleated instability to the absence of equilibrium connecting
the planet to its parent disk and discuss its relevance for massive planet
formation.
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