Astronomers have been on the hunt for a new kind of exoplanet in recent years—one especially suited for habitability. They're called Hycean worlds, and they're characterized by vast liquid water oceans and thick hydrogen-rich atmospheres. The name was coined in 2021 by Cambridge astronomer Nikku Madhusudhan, whose team got a close-up look at one possible Hycean world, K2-18b, using the James Webb Space Telescope in 2023.