New research has found the ‘cannibalistic’ Andromeda galaxy has consumed several smaller galaxies over the last 10 billion years.
In a study published in the Nature journal, global team of researchers led by the Australian National University and the University of Sydney found traces of multiple small galaxies which had been ‘eaten’ by the Andromeda galaxy, using data drawn from the Pan-Andromeda Archaeological Survey. The researchers, representing academic institutions in Australia, Canada, France, Germany, the Netherlands, New Zealand and the UK, studied globular clusters of stars in orbit around Andromeda to identify traces of galaxies it had consumed; and noted that the Milky Way may be swallowed by its larger neighbour within four billion years.
The study’s co-leader Dr Mackey, from Australia National University’s Research School of Astronomy and Astrophysics said: “The Milky Way is on a collision course with Andromeda in about four billion years, so knowing what kind of a monster our galaxy is up against is useful in finding out the Milky Way’s ultimate fate. Andromeda has a much bigger and more complex stellar halo than the Milky Way, which indicates that it has cannibalised many more galaxies, possibly larger ones – by tracing the faint remains of these smaller galaxies with embedded star clusters, we’ve been able to recreate the way Andromeda drew them in and ultimately enveloped them at the different times.”
Dr Michelle Collins of the University of Surrey, who took part in the study, said: “Seeing two distinct meal times for Andromeda was quite surprising. The way the globular clusters move around Andromeda suggest that this galaxy had a large breakfast around 10 billion years ago, and a big lunch perhaps only a few billion years ago. The two accretion events have come from strikingly different directions, as the two globular cluster populations are orbiting at right angles to one another. This directionality may tell us something about the cosmic web within which Andromeda and the Milky Way are embedded and gives us insight into the formation of our massive neighbour.”