star after becoming tidally locked, and thus would still experience a day-night cycle indefinitely. Scientists consider tidal heating as a threat for the habitability of exomoons. Host star There is a minimum mass of roughly 0.20 solar masses for stars to host habitable moons within the stellar habitable zone. When effects of eclipses as well as constraints from a satellite's orbital stability are used to model the runaway greenhouse limit of hypothetical moons, it is estimated that — depending on a moon's orbital eccentricity — there is a minimum mass of roughly 0.20 solar masses for stars to host habitable moons within the stellar habitable zone. Mass If a moon at less than 1% the mass of the Earth such as Europa were to orbit the Sun at a distance similar to Earth's orbit, it would only be able to hold onto its atmosphere for a few million years. However, for any larger, Ganymede-sized moons venturing into its stellar system's habitable zone, an atmosphere and surface water could be retained pretty much indefinitely. Models for moon formation suggest the formation of even more massive moons than Ganymede is common around many of the super-Jovian exoplanets. Detection They are different methods to detect exomoons. Using a transiting exoplanet, the CHEOPS mission could detect exomoons around the brightest red dwarfs. Using the same method, ESPRESSO could detect the Rossiter–McLaughlin effect caused by the exomoons. Candidates 2MASS J1119-1137AB The possible exomoon candidate transiting 2MASS J1119-1137AB lies in the habitable zone of its host (at least initially until the planet cools), but it is unlikely complex life has formed as the system is only 10 Myr old. If confirmed, the exomoon may be similar to primordial earth and characterization of its atmosphere with the James Webb Space Telescope could perhaps place limits on the time scale for the formation of life. Red dwarf systems Scientists studied the possibility of exomoons around planets that orbit red dwarfs in the habitable zone. While they found 33 exoplanets from earlier studies that lie in the habitable zone, only four could host Moon- to Titan-mass exomoons for timescales longer than 0.8 billion years. These four planets were HIP 12961 b, HIP 57050 b, Gliese 876 b and Gliese 876 c. For this mass range however, the exomoons could probably not hold onto their atmosphere. The researchers increased the mass for the exomoons and found that those with the