Enhanced thermal radiation from a tidally heated exomoon with a single hot spot

TL;DR

This paper investigates how uneven tidal heating, concentrated in hot spots, enhances the thermal emission of tidally heated exomoons, potentially making them detectable through their thermal flux signatures.

Contribution

It introduces a model for uneven tidal heating distribution on exomoons and predicts their detectability via thermal emission signals.

Findings

Hot spots significantly increase thermal emission.

Detectability of Earth-sized exomoons around red dwarfs is feasible.

Thermal flux can exceed 100 ppm in optimal conditions.

Abstract

An exomoon on a non perfectly circular orbit experiences tidal heating that is capable to significantly contribute to the thermal brightness of the moon. Here we argue that the thermal heat is unevenly distributed on the moon's surface, the emission of the tidal heat is limited to a few hot spots on the surface. A well-known example is the tidally heated Io. Due to their significantly increased temperature, the hot spots enhance the energy emission in thermal wavelengths. We made simulations using Monte-Carlo method to examine this contribution, and to predict about the possible detectability of such a spotted exomoon. We found that in the case of large, Earth sized companions to jupiters around red dwarf stars exhibit a thermal flux that enables the direct detection of the moon, due to its photometric signal that can exceed $\approx$100 ppm in the most favourable configurations.