Andromeda absorbs a smaller neighbouring galaxy. We’re next.
Published in the journal Nature on 3 September 2020, the research shows how large galaxies grow by incorporating stars from surrounding smaller galaxies. This popular model of galaxy evolution, called the ?hierarchical model?, predicts that large galaxies such as Andromeda, which can be seen with the naked eye from the northern hemisphere, should be surrounded by relics of smaller galaxies it has connected with.
The discovery was made by a team of international astronomers, including Professor Geraint Lewis from the University of Sydney?s School of Physics. The team was led by Dr Alan McConnachie, from the National Research Council of Canada?s Herzberg Institute of Astrophysics, and included astronomers from universities in Canada, Australia, France, Germany, the UK and the USA.
?The Andromeda Galaxy is our closest giant neighbour, located more than 2.5 million light years from the Milky Way. Our new survey charts an area with a diameter of nearly a million light years, centred around Andromeda ? it?s the broadest and deepest image of a galaxy ever made,? said Professor Geraint Lewis.
?We mapped Andromeda?s unexplored outskirts for the first time and found stars and giant structures that are remnants of smaller galaxies, which have been incorporated into Andromeda as part of its ongoing growth,? explained Professor Lewis.
?The big surprise in the data was finding that Andromeda is interacting with its neighbour, the Triangulum Galaxy, a galaxy which is also visible in the Northern Hemisphere using a small telescope. Millions of Triangulum?s stars have been pulled in by Andromeda as part of the encounter. The two galaxies may eventually merge together entirely,? explained Professor Lewis.
Since Andromeda is our closest neighbour, we should naturally ask if we?re at risk. The answer to that question is ?yes?, according to Professor Geraint Lewis: Andromeda is moving towards the Milky Way at a speed of around half a million kilometres per hour, meaning our galaxies are scheduled to collide in about three billion years.
[Via University of Sydney]
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