The Survival Rate of Ejected Terrestrial Planets with Moons

TL;DR

This paper explores the fate of terrestrial planets with moons ejected by giant planet interactions, highlighting their potential to host liquid water and be detectable via infrared or microlensing surveys.

Contribution

It introduces the concept that terrestrial planets with moons can be ejected into space, maintaining conditions for habitability and offering new detection methods.

Findings

A significant fraction of terrestrial planets with moons are ejected into interstellar space.

Ejected planets with moons can sustain liquid water due to tidal heating for hundreds of millions of years.

Microlensing surveys can potentially detect these ejected planetary systems.

Abstract

During planet formation, a gas giant will interact with smaller protoplanets that stray within its sphere of gravitational influence. We investigate the outcome of interactions between gas giants and terrestrial-sized protoplanets with lunar-sized companions. An interaction between a giant planet and a protoplanet binary may have one of several consequences, including the delivery of volatiles to the inner system, the capture of retrograde moons by the giant planet, and the ejection of one or both of the protoplanets. We show that an interesting fraction of terrestrial-sized planets with lunar sized companions will likely be ejected into interstellar space with the companion bound to the planet. The companion provides an additional source of heating for the planet from tidal dissipation of orbital and spin angular momentum. This heat flux typically is larger than the current radiogenic heating of the Earth for up to the first few hundred million years of evolution. In combination with an atmosphere of sufficient thickness and composition, the heating can provide the conditions necesary for liquid water to persist on the surface of the terrestrial mass planet, making it a potential site for life. We also determine the possibility for directly detecting such systems through all-sky infrared surveys or microlensing surveys. Microlensing surveys in particular will directly measure the frequency of this phenomenon.