Transits of extrasolar moons around luminous giant planets

TL;DR

This paper explores the potential detectability of transiting exomoons around luminous young giant planets, highlighting their habitability prospects and the observational signatures in infrared light curves.

Contribution

It introduces the concept that exomoons around young, hot giant planets could be detectable via infrared transits and discusses their potential habitability due to alternative heating sources.

Findings

Exomoons around young giant planets could produce detectable infrared transit signals.

Heating from planetary radiation and tidal friction may sustain liquid water on exomoons.

A Mars-mass water-rich moon around β Pic b could produce a transit depth detectable by future technology.

Abstract

Beyond Earth-like planets, moons can be habitable, too. No exomoons have been securely detected, but they could be extremely abundant. Young Jovian planets can be as hot as late M stars, with effective temperatures of up to 2000 K. Transits of their moons might be detectable in their infrared photometric light curves if the planets are sufficiently separated ($\gtrsim10$ AU) from the stars to be directly imaged. The moons will be heated by radiation from their young planets and potentially by tidal friction. Although stellar illumination will be weak beyond 5 AU, these alternative energy sources could liquify surface water on exomoons for hundreds of Myr. A Mars-mass H$_2$O-rich moon around $\beta$ Pic b would have a transit depth of $1.5\times10^{-3}$, in reach of near-future technology.