The origin of galaxies completely devoid of dark matter is revealed

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The origin of galaxies completely devoid of dark matter is revealed
The origin of galaxies completely devoid of dark matter is revealed

Scientists have found that the recently discovered "super-scattered galaxies", almost completely devoid of dark matter, are satellites of larger galaxies with extremely elongated orbits. This was reported on Monday by the press service of the Massachusetts Institute of Technology (MIT), citing an article in the journal Nature Astronomy.

“We found that these galaxies revolve in orbits similar to the way comets move around the Sun. Like small celestial bodies, they periodically move huge distances from larger galaxies, and some of them never come back. of them did not manage to make even one turn during the entire existence of the Universe, "said Laura Sayles, an assistant professor at the University of California at Riverside (USA), quoted by the MIT press service.

Two years ago, astronomers from the United States discovered that at once two galaxies in the constellation of Coma, NGC1052-DF2 and NGC1052-DF4, unexpectedly contain almost no dark matter. In terms of their size, both of these objects are not inferior to the Milky Way, but their mass turned out to be several orders of magnitude less. Due to the extremely low density of matter, researchers began to call them "super-scattered galaxies" (UDG).

Subsequently, Chinese astronomers discovered two dozen more similar objects, which forced scientists to look for an explanation for their existence. Scientists were particularly interested in the fact that almost all "super-scattered galaxies" are located outside large clusters, where gravitational interactions, in theory, could deprive them of almost all reserves of dark matter.

Sayles and her colleagues have found an explanation for this strange trait of "super-scattered galaxies" and also revealed the history of their formation during observations of two similar objects, DGSAT I and S82-DG-1. These galaxies are located in the constellation Pisces and Cetus, and at the same time they are removed from the Earth at a relatively short distance, several tens of millions of light years.

Galaxies and comets

Astronomers have noticed that both of these objects have one unique feature that distinguishes them from other "super-scattered galaxies" - they are dominated by old stars and red dwarfs. Such a discovery came as a surprise to the researchers, as it suggests that the formation of new stars inside DGSAT I and S82-DG-1 almost completely stopped in the distant past.

As astronomers explain, stars stop appearing in dwarf galaxies when their larger neighbors deprive them of almost all the cold hydrogen and dust needed to form new stars. In the case of "super-scattered galaxies" this was considered impossible, since they are located at a great distance from all other objects.

Sayles and her colleagues tried to explain this anomaly using a detailed computer model that describes the formation and evolution of these "super-scattered galaxies", as well as all the surrounding corners of space. These calculations unexpectedly indicated that DGSAT I and S82-DG-1 are satellites of other galaxies.

In the distant past, both of these objects approached large galaxies, as a result of which they lost all reserves of dark matter and were thrown into very elongated orbits, similar to the trajectories of comets in the solar system. Several billion years later, they found themselves in an open intergalactic environment, which gave the impression that DGSAT I and S82-DG-1 originated on its territory, and not inside a dense cluster of galaxies.

The calculations of Sayles and her colleagues indicate that an unexpectedly large number of such objects must be lurking in the void between all large groups of galaxies.Their discovery and study, as astronomers hope, will not only confirm their theory, but also allow them to reveal the history of the evolution of the appearance of "super-scattered galaxies."

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