(形容詞) 宜居的。這個字通常用來修飾 planet,即 Hycean planet。這種宜居星球或行星 (有人將之音譯為「海斯星球」或「海斯行星」的大氣層富含氫氣,表面有水,可能跟地球一樣可孕育生命。

The search for life outside our Solar System could be accelerated following the discovery of a new class of habitable exoplanet by University of Cambridge researchers. Dubbed “Hycean planets”, these ocean-covered worlds have hydrogen-rich atmospheres and it is believed they could support microbial life similar to that found in some of Earth's most extreme aquatic environments … Bizarrely, such planets also include tidally-locked "dark" Hycean worlds that may have habitable conditions only on their permanent night sides.
[cambridgeindependent.co.uk, 2 September 2021]