The short-lived production of exozodiacal dust in the aftermath of a dynamical instability in planetary systems

TL;DR

This study uses N-body simulations to show that exozodiacal dust produced after planetary system instabilities is short-lived, making it unlikely to account for the high observed dust levels around many stars.

Contribution

It provides a quantitative analysis demonstrating the transient nature of dust after planetary instabilities, challenging previous assumptions about their role in exozodiacal dust presence.

Findings

Short-lived dust production post-instability

Low probability of observing systems in instability aftermath

Implication that other sources dominate exozodiacal dust

Abstract

Excess emission, associated with warm, dust belts, commonly known as exozodis, has been observed around a third of nearby stars. The high levels of dust required to explain the observations are not generally consistent with steady-state evolution. A common suggestion is that the dust results from the aftermath of a dynamical instability, an event akin to the Solar System's Late Heavy Bombardment. In this work, we use a database of N-body simulations to investigate the aftermath of dynamical instabilities between giant planets in systems with outer planetesimal belts. We find that, whilst there is a significant increase in the mass of material scattered into the inner regions of the planetary system following an instability, this is a short-lived effect. Using the maximum lifetime of this material, we determine that even if every star has a planetary system that goes unstable, there is a very low probability that we observe more than a maximum of 1% of sun-like stars in the aftermath of an instability, and that the fraction of planetary systems currently in the aftermath of an instability is more likely to be limited to <0.06. This probability increases marginally for younger or higher mass stars. We conclude that the production of warm dust in the aftermath of dynamical instabilities is too short-lived to be the dominant source of the abundantly observed exozodiacal dust.