One of the Coolest Discoveries About Andromeda You Never Knew About
Credit: Adam Evans http://www.flickr.com/photos/astroporn/4999978603/
You’ve may have heard of this famous galaxy called Andromeda or M31. It’s located 2.5 million light years away and it’s so large that it can even be seen with the naked eye! However, that’s not the astounding fact I want to talk about today. What’s really interesting is this research paper published in the new Nature issue (March 2014). What researchers discovered is that Andromeda is surrounded by numerous small satellite galaxies (that’s not even the new part!). Astronomers from the Niels Bhor Institute, and among others, detected a string of stars in one of Andromeda’s outer galaxies called Andromeda II. As these researchers follow the movement of the stars they uncovered that they were left over from a merger between two dwarf galaxies. Mergers of such low mass galaxies have not been observed before.
When the universe was young you would see small galaxies forming and these galaxies would eventually get bigger by larger ones engulfing smaller ones. Even large galaxies attract the smaller galaxies and eat them right up! However, not all galaxies get eaten, some of them get along and orbit each other. Just like how the small satellite galaxies swarming around Andromeda. In fact, there are so many of these satellite galaxies swarming around Andromeda that scientists have counted 20 of them! They’ve been naming them Andromeda I, II, III, IV etc. Researchers have discovered something interesting with Andromeda II:
“Stars in a dwarf galaxy often move around at random, but this is not exactly the case for Andromeda II. In particular we could see that a stream of stars is moving around differently than the rest in a very coherent way. These stars are situated in an almost complete ring and are rotating around the centre of the galaxy.” Astrophysicist Nicola C. Amorisco, Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen
It’s quite interesting because the dwarf galaxy Andromeda II is less than 1% of the Milky Way and seeing a merger usually happens when galaxies forms. There’s much to learn about this process and now that researchers have all eyes on Andromeda II they can learn more about the mergers of galaxies.