Hycean worlds are planets covered in oceans that also have thick hydrogen atmospheres. There are no confirmed Hycean worlds—also called ocean worlds—but many candidates. Even though they're only candidates so far, researchers are curious about their habitability. New research examines the role tidal heating plays in their potential habitability.

If hycean planets do exist, they’re likely common around red dwarfs (M dwarfs.) Red dwarfs are the most plentiful type of star in the galaxy, and Hycean worlds’ thick hydrogen atmospheres might protect them from the devastating flaring behaviour of these small, long-lived stars. Hycean worlds may have larger habitable zones because of all their water, but their hydrogen atmospheres may contribute to the runaway greenhouse effect. When it comes to habitability, these hypothetical worlds are intriguing and mysterious.