The Milky Way has collided with a galaxy in the past. What effect did it have on our galaxy?

Credit image: ESA
Credit image: ESA

We all know that our galaxy will collide with the Andromeda galaxy in the future, and if humanity still exists then, it will be something new, but for our galaxy it will not be something very new. On the contrary, our galaxy may be accustomed to such collisions. 

Recently, a group of scientists discovered that our galaxy has shrunk to approx. 10 billion years with another dwarf galaxy called Gaia-Sausage-Enceladus (GSE) and is probably the most recent collision. Our galaxy is intact, so we shouldn't worry about what will happen in the future when it clashes with Andromeda. But any collision has its effects. 

This collision was discovered using ESA's Gaia Observatory. But how did it find out? Gaia was subjected to several observations during the first 22 months and found a distribution of 30,000 stars on a trajectory opposite to most stars. That seemed a little strange to ESA. The stars stood in such a way in the galaxy, formed a kind of sausage. In addition, the observer also gave data on the brightness of the stars, which according to experts indicate belong to a certain stellar population. 

To better understand this collision, a team of scientists tried to create a simulation as close to reality as possible. They used data from the Gaia Observatory and the Multiple Mirror Telescope (MMT) of the Smithsonian Institution and the University of Arizona, which was involved in this project. 

The main thing scientists wanted to know was whether the galaxies collided head-on or involved a decaying orbit. At the end of the simulation, the scientists got a pretty good result. 

According to the analysis, GSE was approaching the Milky Way in the opposite direction of the rotation of our galaxy until the dwarf galaxy merged with its larger neighbor. Thus, the two galaxies collided in the past. As a result, the dwarf galaxy brought 20% of our galaxies' dark matter and 50% of its stellar halo.

Article by: Andacs Robert Eugen, on 20 February 2022, at 03:34 am Los Angeles time

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