K2-18b, which is eight times the mass of Earth, is now the only exoplanet known to have both water and temperatures that could support life. The discovery 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.
“We have been observing this star for three years to look for periodic variations in its velocity,” explains Mathias Zechmeister, a researcher at the University of Göttingen. The observations showed that two planets are orbiting it, both of them similar to the planets in the inner part of the Solar System. They are just a little bigger than the Earth and are situated in the “inhabitable zone” where water can exist as a liquid.