Nobody really believes that our Solar System is the only one with moons. But the existence of moons in other star systems has only been a hypothesis up until now. So-called exomoons are particularly difficult to find, because they are smaller than their host planets (which is, of course, in their nature) and they follow complicated paths due to their orbits around their planets and, in turn, around their stars. Such objects are usually identified by measuring the occultation caused when they pass in front of their star (transit method). Nevertheless, the Hubble Space Telescope has now finally found…