Andromeda Galaxy turned out to be a cannibal

(ORDO NEWS) — The Andromeda Galaxy is the closest large galaxy to the Milky Way, containing several times more stars. Now an international team of scientists has figured out how she managed to reach such a huge size.

A few years ago, researchers led by an astrophysicist from the University of Sydney (Australia) discovered on the outskirts of the Andromeda galaxy – the nearest large galaxy to us, located 800 kiloparsecs from the Milky Way – mysterious globular clusters that form a stream that they called the “Delice structure” (in translated from the Welsh dulais – “black stream”, and the same name is the river and valley in Wales).

Now they have discovered that these clusters are in fact traces of the violent past of the Andromeda galaxy, which grew in size by devouring smaller galaxies.

Scientists have identified traces of at least two “feasts”: one occurred relatively recently, over the past five billion years, the second much earlier, about eight to ten billion years ago, shortly after the formation of our Universe.

Astronomers are interested in the development of the Andromeda galaxy, since it is very similar to the Milky Way, but, alas, it is not very convenient to observe our Galaxy from the Earth. But we can observe other galaxies freely, because they are not obstructed by the stars and nebulae closest to us.

If the growth pattern of the Andromeda galaxy is typical of large spiral galaxies, it is quite possible that the Milky Way in the past also consumed smaller galaxies, after which it sharply increased in size.

However, it is possible that our Galaxy had a different development model that did not include the absorption of its own kind: for example, it grew due to the “peaceful” retraction of interstellar matter.

Andromeda Galaxy turned out to be a cannibal 2
The passage of globular clusters of the Delice structure ( red ) through the Andromeda galaxy ( blue )

So far, researchers have been able to determine only the speed of movement and the chemical composition of globular clusters: they turned out to be noticeably poorer in metals than the surrounding stars.

In the future, astronomers are going to estimate the distances between individual structures and build a three-dimensional model of the flow, which will literally look into the past of the Andromeda galaxy, during its cruel “feasts”.


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