Astronomers detect ‘waterworld with a boiling ocean’ in deep space

Significant discovery, made by James Webb telescope, provokes disagreement over conditions on planet’s surface

An artist’s impression of the surface of a ‘hycean’ planet – one with a liquid water ocean beneath a hydrogen atmosphere. Photograph: Amanda Smith/PA

Astronomers have observed a distant planet that could be entirely covered in a deep water ocean, in findings that advance the search for habitable conditions beyond Earth.

The observations, by Nasa’s James Webb space telescope (JWST), revealed water vapour and chemical signatures of methane and carbon dioxide in the atmosphere of the exoplanet, which is twice Earth’s radius and about 70 light years away. This chemical mix is consistent with a water world where the ocean would span the entire surface, and a hydrogen-rich atmosphere, according to researchers from the University of Cambridge, although they do not envisage a balmy, inviting seascape.