Binary asteroid scattering around white dwarfs

TL;DR

This study investigates the dynamical evolution of binary asteroid systems around white dwarfs, revealing their potential to be dissociated and ejected, and discusses implications for white dwarf pollution and interstellar objects.

Contribution

The paper introduces the first detailed simulation of equal-mass binary asteroid systems around white dwarfs, exploring their fate and impact on planetary system evolution.

Findings

Binary systems can be dissociated and ejected within Myr timescales.

Ejected planetesimals are gravitationally unbound, not forming free-floating binaries.

Binarity has little effect on the proximity of bodies to white dwarfs but influences scattering dynamics.

Abstract

Increasing observations of white dwarf atmospheric pollution and disrupting planetesimals is driving increased studies into the fate of exo-asteroids around post-main-sequence stars. Planetesimal populations in the Solar System which are most likely to survive the violent post-main-sequence evolution, such as the Kuiper Belt, display a large binary fraction with a propensity for near equal-mass components and provide a previously unexplored population of planetesimals which are likely to exist around white dwarfs. Here we simulate the dynamical evolution of equal-mass binary asteroid systems around white dwarfs using the N-body integrator REBOUND for 1 Gyr. We confirm that giant planets are efficient at dissociating and ejecting binary asteroid systems on eccentric orbits, while Earth-mass planets are better at keeping planetesimals in their planetary systems. We find binary systems can be dissociated and ejected from their systems across Myr timescales, producing interstellar objects. We do not expect a population of free-floating binary asteroid systems as all ejected planetesimals are gravitationally unbound from each other. Further, we discuss the influence of asteroid binarity on the white dwarf pollution process and find there is little to no impact on how close a body can get to a star. However, the orbital evolution of binary asteroids changes the distribution of planetesimals available in a white dwarf planetary system to be further scattered onto white dwarf polluting orbits.