Effects of Dynamical Evolution of Giant Planets on Survival of Terrestrial Planets

TL;DR

This study investigates how the early dynamical instability of giant planets can clear out inner regions, affecting the survival of terrestrial planets and explaining observed exoplanet distributions.

Contribution

It demonstrates that secular perturbations from giant planets can remove inner test particles, providing a semi-analytical model for unstable regions and linking dynamical history to observed exoplanet configurations.

Findings

Most inner test particles are ejected or destabilized by giant planets.

Secular perturbations can clear regions up to 0.1 AU.

Results align with observations and suggest hot rocky planets may exist in eccentric systems.

Abstract

The orbital distributions of currently observed extrasolar giant planets allow marginally stable orbits for hypothetical, terrestrial planets. In this paper, we propose that many of these systems may not have additional planets on these "stable" orbits, since past dynamical instability among giant planets could have removed them. We numerically investigate the effects of early evolution of multiple giant planets on the orbital stability of the inner, sub-Neptune-like planets which are modeled as test particles, and determine their dynamically unstable region. Previous studies have shown that the majority of such test particles are ejected out of the system as a result of close encounters with giant planets. Here, we show that secular perturbations from giant planets can remove test particles at least down to 10 times smaller than their minimum pericenter distance. Our results indicate that, unless the dynamical instability among giant planets is either absent or quiet like planet-planet collisions, most test particles down to ~0.1 AU within the orbits of giant planets at a few AU may be gone. In fact, out of ~30 % of survived test particles, about three quarters belong to the planet-planet collision cases. We find a good agreement between our numerical results and the secular theory, and present a semi-analytical formula which estimates the dynamically unstable region of the test particles just from the evolution of giant planets. Finally, our numerical results agree well with the observations, and also predict the existence of hot rocky planets in eccentric giant planet systems.