The destruction of inner planetary systems during high-eccentricity migration of gas giants

TL;DR

This paper demonstrates that high-eccentricity migration of gas giants can clear out inner planetary systems, explaining the lack of close-in low-mass planets near hot Jupiters and providing insights into their orbital evolution.

Contribution

It shows that high-eccentricity migration explains the absence of inner low-mass planets and predicts possible ejections or moderate eccentricities of giant planets.

Findings

High-eccentricity migration clears inner low-mass planets.

Giant planets can be ejected or placed on eccentric orbits.

Supports high-eccentricity migration as a key hot Jupiter formation channel.

Abstract

Hot Jupiters are giant planets on orbits a few hundredths of an AU. They do not share their system with low-mass close-in planets, despite these latter being exceedingly common. Two migration channels for hot Jupiters have been proposed: through a protoplanetary gas disc or by tidal circularisation of highly-eccentric planets. We show that highly-eccentric giant planets that will become hot Jupiters clear out any low-mass inner planets in the system, explaining the observed lack of such companions to hot Jupiters. A less common outcome of the interaction is that the giant planet is ejected by the inner planets. Furthermore, the interaction can implant giant planets on moderately-high eccentricities at semimajor axes $<1$ AU, a region otherwise hard to populate. Our work supports the hypothesis that most hot Jupiters reached their current orbits following a phase of high eccentricity, possibly excited by other planetary or stellar companions.