Water is not uncommon to find in our galaxy in ice or gaseous form, but liquid water is quite rare — and liquid and gaseous water on an Earth-like exoplanet? That’s never been observed… until now. Astronomers spotted this celestial unicorn, called K2-18 b, using the venerable Hubble space telescope.
K2-18 b is a “super-Earth,” a planet with a mass and size approximately like our own, and not only that, it exists in its solar system’s “habitable zone,” meaning a range of temperatures where liquid water can continuously exist. It’s about 110 light-years away in the constellation Leo.
Of course there are many super-Earths, and many planets in habitable zones, and many planets with water — but they’re never one and the same. This is