Misaligned circumbinary disks as efficient progenitors of interstellar asteroids

TL;DR

Misaligned circumbinary disks can efficiently produce interstellar asteroids through high-velocity collisions that eject material, with binary parameters influencing the likelihood of ejection versus planet formation.

Contribution

This study demonstrates that misaligned circumbinary disks are effective progenitors of interstellar asteroids, highlighting the role of binary parameters and disk misalignment in material ejection.

Findings

Approximately 59% of binaries eject most of their disk material.

High impact velocities lead to mass ejection and diverse fragment sizes.

Misaligned disks produce objects with properties similar to 'Oumuamua.

Abstract

Gaseous circumbinary disks (CBDs) that are highly inclined to the binary orbit are commonly observed in nature. These disks harbor particles that can reach large mutual inclinations as a result of nodal precession once the gas disk has dissipated. With n-body simulations that include fragmentation we demonstrate that misaligned disks of particles can be efficient progenitors of interstellar asteroids (ISAs). Collisions that take place between particles with large mutual inclinations have large impact velocities which can result in mass ejection, with a wide range of fragment sizes and ejection velocities. We explore the binary parameters for which the majority of the terrestrial planet forming material is ejected rather than accreted into planets. The misalignment required to eject significant material decreases with binary eccentricity. If the distribution of binary eccentricity is uniform and the initial particle CBD orientation relative to the binary orbit is isotropic, about 59% of binaries are more likely to eject the majority of their CBD terrestrial planet disk mass through high velocity body-body collisions rather than retain this material and build terrestrial planets. However, binary--disk interactions during the gas disk phase with non-zero disk viscosity will reduce this fraction. The composition, small size, highly elongated shape, and tumbling motion of `Oumuamua is consistent with ISAs generated by misaligned CBDs.