Scientists have long been aware of the fact that galaxies are growing in volume when they swallow up other, smaller galaxies. This process is part of the cosmic evolution. Evidence of this is the cosmic auras (halo) in which the stars of the cannibalized galaxies can be spotted, Science Alert writes.
All this applies in full force for Andromeda (also known as M31) – our closest neighbor. The galaxy has a huge and virtually invisible halo of stars that is bigger than itself. For a long time, scientists thought it had come from a number of small mergers. However, thanks to a new study by astronomers at Michigan University, it is clear that Andromeda’s halo is the result of the cannibalization of a giant galaxy about 2 billion years ago.
Scientists hope that by exploring the debris of this galaxy more thoroughly, they will be able to understand more about how disk galaxies (such as the Milky Way) have evolved and have not succumbed to cannibalization.
From the simulations, it is clear that the former giant (called M32p) was about 20 times larger than any other galaxy that once merged with the Milky Way. In other words, M32p was probably the third largest member of the “Local group” (after Milky Way and Andromeda).
The new discovery will help astronomers learn how galaxies like the Milky Way and Andromeda grew during the merger, but will also help unravel a longstanding mystery – how it was formed M32 – the satellite galaxy of Andromeda.