Wandering stars, also called ‘intergalactic stars’, ‘intracluster stars’ or ‘rogue stars’, are stars that are not gravitationally tied to a particular 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 Milky Way and the Andromeda Galaxy.
This article is an answer to the question (asked by Diane Berry, via email) 'What is a wandering star?'
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