A Possible Dynamical History for the Fomalhaut System

TL;DR

This paper proposes a dynamical history for the Fomalhaut system, suggesting that an unseen planet Fomalhaut c influences the debris belt and that Fomalhaut b's current orbit results from resonance with Fomalhaut c.

Contribution

It introduces a model where Fomalhaut c is a Saturn- to Neptune-sized planet shaping the debris belt and explains Fomalhaut b's orbit through resonance, proposing a recent transient system configuration.

Findings

Fomalhaut c is likely Saturn- to Neptune-sized.

Fomalhaut b's orbit is explained by mean-motion resonance with Fomalhaut c.

The current system configuration is transient and recent.

Abstract

Fomalhaut b was long thought to shape the eccentric debris belt in the Fomalhaut system, but its orbit was found to be too eccentric for it to be the dominant belt-shaping perturber. This indicates that Fomalhaut b is Earth-sized at most and that the belt-shaping perturber, hereafter named Fomalhaut c, remains to be discovered. In addition, since its orbit more or less crosses that of Fomalhaut b, it also indicates that the current configuration of the system is transient and was reached recently. In this talk, we show that this current configuration can be explained if Fomalhaut c is Saturn- to Neptune-sized, and Fomalhaut b originates from a mean-motion resonance with Fomalhaut c.