One of the nearest galaxies to our own has expanded by absorbing its smaller neighbours, astronomers have found.
The Andromeda galaxy, which is 2.5 million light years from the Milky Way, has been shown to contain structures that could only have come from other galaxies. Researchers, who used a powerful new telescope to look at Andromeda’s uncharted outer regions, found stellar debris likely to have been left by other galaxies.
The study, published in Nature, also found mature stars that could not have been generated by the galaxy itself so far from its hot core.
The team, led by Mike Irwin, of Cambridge University, believe that their results offer further evidence for the theory that galaxies grow by absorbing smaller galaxies over time.
Dr Irwin said: “This is a startling demonstration of the vast scale of galaxies. [It shows] that galaxies are the result are an ongoing process of interaction with their neighbours.” The study need not cause immediate concern for the Milky Way’s fate, however. Dr Irwin said: “Although the Milky Way is smaller than Andromeda by two or three times, it will be at least several billion years before Andromeda absorbs us.” The team has shown, indeed, that the Milky Way is itself in the process of absorbing a smaller neighbour, the Sagittarius dwarf galaxy.
Advertisement
The team’s survey, the largest to date of its kind, will continue to January 2011.