Effects of a planetesimal debris disk on stability scenarios for the extrasolar planetary system HR 8799

TL;DR

This study uses numerical simulations to show that debris disks can significantly influence the long-term stability of the HR 8799 planetary system, either destabilizing or stabilizing planetary configurations depending on disk mass.

Contribution

It demonstrates how debris disks with varying masses can alter the stability timescales of planetary systems, highlighting the importance of including debris disks in stability analyses.

Findings

A debris disk with 1% of the outer planet's mass can destabilize a stable resonance in 2-6 Myrs.

A debris disk exceeding 10% of the outer planet's mass can stabilize otherwise unstable configurations.

Debris disks significantly impact the estimated long-term stability of planetary systems.

Abstract

HR 8799 is a four planet system that also hosts a debris disk. By numerically integrating both planets and a planetesimal disk, we find interactions between an exterior planetesimal disk and the planets can influence the lifetime of the system. We first consider resonant planetary configurations that remained stable for at least 7 Myrs sans debris disk. An exterior debris disk with only 1 per cent the mass of the outermost planet (approximately a Neptune mass) was sufficiently large enough to pull the system out of resonance after 2 to 6 Myrs. Secondly, we consider configurations which are unstable in less than a few hundred thousand years. We find that these can be stabilized by a debris disk with a mass of more than 10 per cent that of the outermost planet. Our two sets of simulations suggest that estimates of the long term stability of a planetary system should take into account the role of the debris disk.