Tidal Downsizing Model. IV. Destructive feedback in planets

TL;DR

This paper emphasizes the critical role of feedback from solid cores in planet formation, explaining observed exoplanet properties and the diversity of planetary core sizes through a tidal downsizing model.

Contribution

It introduces the importance of destructive feedback in planet formation, providing explanations for the distribution and composition of observed exoplanets and planetary cores.

Findings

Feedback causes gas giants to be vulnerable to tidal disruption.

Explains the rarity of gas giants at various separations.

Accounts for the diversity in planetary core sizes and compositions.

Abstract

I argue that feedback is as important to formation of planets as it is to formation of stars and galaxies. Energy released by massive solid cores puffs up pre-collapse gas giant planets, making them vulnerable to tidal disruptions by their host stars. I find that feedback is the ultimate reason for some of the most robust properties of the observed exoplanet populations: the rarity of gas giants at all separations from $\sim 0.1$ to $\sim 100$~AU, the abundance of $\sim 10 M_\oplus$ cores but dearth of planets more massive than $\sim 20 M_\oplus$. Feedback effects can also explain (i) rapid assembly of massive cores at large separations as needed for Uranus, Neptune and the suspected HL Tau planets; (ii) the small core in Jupiter yet large cores in Uranus and Neptune; (iii) the existence of rare "metal monster" planets such as CoRoT-20b, a gas giant made of heavy elements by up to $\sim 50$\%.