Formation, Habitability, and Detection of Extrasolar Moons

TL;DR

This paper reviews the formation, habitability, and detection methods of extrasolar moons, highlighting that sizable, potentially habitable moons could be detectable with current or near-future technology, expanding the search for life beyond planets.

Contribution

It provides a comprehensive overview of exomoon formation channels, orbital dynamics, habitability criteria, and detection techniques, emphasizing the potential for discovering habitable moons in the near future.

Findings

Exomoons of 0.1 - 0.5 Earth mass may be habitable.

Such moons can form in circumplanetary disks or via capture.

Current technology could detect these moons.

Abstract

The diversity and quantity of moons in the Solar System suggest a manifold population of natural satellites exist around extrasolar planets. Of peculiar interest from an astrobiological perspective, the number of sizable moons in the stellar habitable zones may outnumber planets in these circumstellar regions. With technological and theoretical methods now allowing for the detection of sub-Earth-sized extrasolar planets, the first detection of an extrasolar moon appears feasible. In this review, we summarize formation channels of massive exomoons that are potentially detectable with current or near-future instruments. We discuss the orbital effects that govern exomoon evolution, we present a framework to characterize an exomoon's stellar plus planetary illumination as well as its tidal heating, and we address the techniques that have been proposed to search for exomoons. Most notably, we show that natural satellites in the range of 0.1 - 0.5 Earth mass (i) are potentially habitable, (ii) can form within the circumplanetary debris and gas disk or via capture from a binary, and (iii) are detectable with current technology.