Enhanced thermal radiation from a tidally heated exomoon with a single hotspot

Abstract

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 hotspots on the surface. A well-known example is the tidally heated Io. Due to their significantly increased temperature, the hotspots 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 ≈100 ppm in the most favourable configurations.