Water vapour has been detected in the atmosphere of a super-Earth with habitable temperatures by UCL researchers in a world first. K2-18b, which is eight times the mass of Earth, is now the only planet orbiting a star outside the Solar System, or ‘exoplanet’, known to have both water and temperatures that could support life. The discovery, published in Nature Astronomy, is the first successful atmospheric detection for an exoplanet orbiting in its star’s ‘habitable zone’, at a distance where water can exist in liquid form.