Scientists have found a likely clue to the mystery of the structure at the center of the Milky Way

The bar (or bridge) in the center of the Milky Way, the origin of which has long been debated by scientists, was probably formed as a result of the collision of our galaxy with another. This is a cosmic event that took place between 8 and 11 billion years ago when the Milky Way and a dwarf galaxy known as the Sausage of Gaia or Enceladus of Gaia collided.

This is stated in a new study published on the arXiv preprint site. The work of scientists is still awaiting evaluation by the scientific community and publication in a specialized journal.

It is believed that only clusters of old stars floating in the vicinity of the Milky Way are left of the dwarf galaxy after the collision. But the new work suggests that it left another trace – a bar crossing the center of the Milky Way galaxy.

Previously, scientists assumed that a galactic collision occurred around the same time as the bar, but no one had ever linked one event to the other. However, as Inverse writes, a computer simulation has shown that this is the only explanation for why our galaxy looks like this.

"It's a strange coincidence that two very important events in the history of the Milky Way occurred at such a similar time," said Alex Cook, a PhD student at Liverpool John Moores University and lead author of the study.

"Scientists have known about galactic collisions for a long time. Such events occur almost constantly, but it is quite difficult to observe them. This process is incredibly slow – one collision can last hundreds of millions of years. So it is not surprising that astronomers have seen very few collisions in space.

Instead, computer simulations shed light on the mystery of these events.

The authors of the paper were actually studying such collisions when, during one of 30 simulations, they saw that a bar was formed as a result of the collision of a galaxy similar to the Milky Way with a dwarf galaxy similar to Enceladus Gaia.

They were interested in this, so they ran the simulation again, but this time they removed the galaxy collision factor.

"The end result didn't look like the Milky Way in many ways," Cook said.

In particular, the flat disk did not expand to the size we see in the Milky Way today. At the same time, a bar in the galaxy did form, but billions of years later than scientists assume the Milky Way bar was formed.

Thus, the results of the simulation confirmed that the bar is as old as the collision, and the collision was a necessary condition for the Milky Way bar to form as astronomers see it now.

Cook said that in the future, he and his team intend to run new simulations and better understand how bars are formed.

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