Exomoon Habitability Constrained by Illumination and Tidal Heating -- The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet, and hence experience days much shorter than their orbital period around the star, and have seasons - all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local...