Natural Satellite Habitability - Extrasolar

Extrasolar

Further information: Extrasolar moon See also category: Gas giant planets in the habitable zone

No extrasolar natural satellites have yet been detected. Large planets in the Solar System like Jupiter and Saturn are known to have large moons with some of the conditions for life. Therefore some scientists speculate that large extrasolar planets (and double planets) may have similarly large moons that are potentially habitable. A moon with sufficient mass may support an atmosphere like Titan and may also sustain liquid water on the surface.

Massive exoplanets known to be located within a habitable zone (such as Gliese 876 b, 55 Cancri f, Upsilon Andromedae d, 47 Ursae Majoris b, HD 28185 b and HD 37124 c) are of particular interest as they may potentially possess natural satellites with liquid water on the surface.

Habitability of extrasolar moons has been considered in at least two studies published in peer-reviewed journals. René Heller & Rory Barnes considered stellar and planetary illumination on moons as well as the effect of eclipses on their orbit-averaged surface illumination. They also considered tidal heating as a threat for their habitability. In Sect. 4 in their paper, they introduce a new concept to define the habitable orbits of moons. Referring to the concept of the circumstellar habitable zone for planets, they define an inner border for a moon to be habitable around a certain planet and call it the circumplanetary "habitable edge". Moons closer to their planet than the habitable edge are uninhabitable. In a second study, René Heller then included the effect of eclipses into this concept as well as constraints from a satellite's orbital stability. He found that, depending on a moon's orbital eccentricity, there is a minimum mass for stars to host habitable moons and located it around 0.2 solar masses.