Hycean Planet

A hycean planet is a hypothetical type of planet with liquid water oceans under a hydrogen atmosphere. The presence of extraterrestrial liquid water makes hycean planets regarded as promising candidates for planetary habitability. They are usually considered to be larger and more massive than Earth. As of 2023, there are no confirmed hycean planets, but the Kepler mission detected many candidates. Hycean planets could be considerably larger than previous estimates for habitable planets, with radii reaching 2.6 R🜨 (2.3 R🜨) and masses of 10 ME (5 ME). Moreover, the habitable zone of such planets could be considerably larger than that of Earth-like planets. The planetary equilibrium temperature can reach 430 K (157 °C; 314 °F) for planets orbiting late M-dwarfs. However, mass and radius do not by themselves inform the composition of a planet, as bodies with identical mass and radius can have distinct compositions: A given planet may thus be either a hycean planet or a super-Earth. Such planets can have many distinct atmospheric compositions and internal structures. Also possible are tidally locked "dark hycean" planets (habitable only on the side of permanent night) or "cold hycean" planets (with negligible irradiation, being kept warm by the greenhouse effect). Dark hycean worlds can form when the atmosphere does not effectively transport heat from the permanent day side to the permanent night side, thus the night side has temperate temperatures while the day side is too hot for life. Cold hycean planets may exist even in the absence of stars, e.g. rogue planets.
Category:Planet type
Category:Planet