Wandering stars, also called ‘intergalactic stars’, ‘intracluster stars’ or ‘rogue stars’, are stars that are not gravitationally tied to a par ticular galaxy – they exist between galaxies. These stars, first discovered in 1997, probably formed inside galaxies, but were later expelled, perhaps during galaxy mergers or by a close encounter with a supermassive black hole. Astronomers estimate that rogue stars comprise between 15–50 per cent of all stars in galaxy clusters. The Virgo galaxy cluster, for example, contains perhaps 1 trillion rogue stars! Closer to home, at least 675 rogue stars have been found between the Milk y Way and the Andromeda Galaxy. AG