The first such region to come under investigation was a small cloud identified by the Persian astronomer al-Sufi in the tenth century. It is bright enough to be detected by the naked eye and became known as the Andromeda nebula. The suggestion that this and other clouds might actually be galaxies in their own right was first voiced in 1750 by English astronomer Thomas Wright. After reading about Wright’s ideas, Immanuel Kant romantically referred to them as ‘island universes’.
