Studying the galaxy at 9 billion light years from Earth, astronomers found that the amount of dark matter contained in it is comparable to that observed in the galaxies of our era. This is contrary to the study of 2017, in which it was argued that the stellar structures of the early Universe are fundamentally different from the modern ones.
The galaxy we discovered is the first vivid example of the fact that the behavior and role of dark matter are similar throughout almost the entire history of the Universe.
-Caitlin Casey, co-author of the study at the University of Texas (USA)
Dark matter is an invisible substance that does not emit light, and it can only be detected by the gravitational effect on the baryon substance. For the first time, they started talking about it seriously in the 1970s when studying spiral galaxies, whose outer regions rotated too fast and could not be controlled only by visible stars and gas. Astronomers have concluded that there must be a lot of invisible mass in these galaxies. Subsequent observations showed that in almost all galaxies there is a huge amount of dark matter and that it is five times more in the Universe than normal.
However, several recent studies have shown that some galaxies are knocked out of the overall picture of dark-rich structures. In particular, a handful of galaxies no less than 10 billion years old were discovered that did not contain the expected amount of dark matter. This may mean that the star houses at that time contained much less invisible substance, but then at some point acquired it. Such conclusions question the current fundamental understanding of how galaxies are formed.
During the review of the most violent star-forming galaxies, the purpose of which was not to search for dark matter, astronomers, to their surprise, found that one of them, designated DSFG850.95, contains a normal amount of invisible matter, as well as the old theories supposed. Since DSFG850.95 lives at a distance of 9 billion light-years from us, the find tells us that some galaxies already contained quite a lot of dark matter in those times.
Because of the successful angle at which DSFG850.95 faces the Earth, scientists were able to obtain extremely detailed data on the speed of rotation of its regions, from the center to the outskirts, which clearly indicate that it contains all the expected dark matter.
In order to understand whether DSFG850.95 is unique for that era or is a common phenomenon, the authors of the study plan to continue exploring distant galaxies using the ALMA radio telescope array.
Unusual galaxy in the early universe
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