Ejection of rocky and icy material from binary star systems: Implications for the origin and composition of 1I/`Oumuamua

TL;DR

This paper suggests that interstellar objects like 1I/`Oumuamua are likely ejected from circumbinary systems, with a significant rocky component, challenging the idea that comets dominate interstellar object populations.

Contribution

It introduces the hypothesis that planetesimal ejection in circumbinary systems produces interstellar objects with a higher rocky fraction than previously thought.

Findings

Interstellar objects are likely ejected mainly from circumbinary systems.

Rocky bodies are ejected in similar numbers to icy ones in these systems.

Many future interstellar objects should show active comas.

Abstract

In single star systems like our own Solar system, comets dominate the mass budget of bodies that are ejected into interstellar space, since they form further away and are less tightly bound. However 1I/`Oumuamua, the first interstellar object detected, appears asteroidal in its spectra and in its lack of detectable activity. We argue that the galactic budget of interstellar objects like 1I/`Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single star systems or widely separated binaries. We further show that in circumbinary systems, rocky bodies should be ejected in comparable numbers to icy ones. This suggests that a substantial fraction of additional interstellar objects discovered in the future should display an active coma. We find that the rocky population, of which 1I/`Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries.