Habitable Environments in Late Stellar Evolution

With very high potential transit-depths and no stellar flare activity, the planets of White Dwarfs are some of the most promising in the search for detectable extraterrestrial life. We review the evidence that both terrestrial and gas-giant planets are capable of surviving post-main sequence evolution and migrating into the WD phase. We find that WDs are capable of hosting stable Habitable Zones outside orbital distances at which Earthmass planets would be disintegrated by tidal forces. To reach the WD phase, a main-sequence star has to progress along the Asymptotic Giant Branch (AGB) around which circumstellar envelopes are found to spectrally exhibit simple molecules from which amino acids and simple sugars can be synthesised. We find using a simple accretion model that even at distances on the scale of „ 100 AU, a mass of this material greater than that of the Earth’s atmosphere should be delivered to an Earth-mass planet.