The authors of a new study published in The Astrophysical Journal Letters believe that the galaxy bordering the Milky Way consists of a hypothetical form of dark matter, whose particles can interact with each other. But this contradicts the fundamental cosmological model that explains the nature of the universe.
Orbiting the Milky Way, about 380,000 light-years away, is the fourth largest satellite galaxy, Crater 2. It is about 6,500 light-years in diameter and consists of several billion old stars.
In recent years, astronomers have tried to figure out exactly what properties this dwarf galaxy has that allow it to maintain its structure and relatively large size. The evolution of the Crater 2 galaxy is known to be influenced by the Milky Way’s gravity over thousands of years.
It also affects the dark matter halo around the galaxy and its stars. According to scientists, the gravitational influence of our galaxy can remove both dark matter and stars from its neighboring galaxy, causing the galaxy’s mass to decrease over time.
The study authors found that the Milky Way’s gravitational influence is too weak to explain the density of dark matter in Crater 2 if it consists of cold dark matter particles, reports Room.
Dark matter is the invisible part of the universe and makes up more than 80% of the mass. It is believed that dark matter allows all galaxies to be held together as one. But no one has yet directly seen dark matter.
The main cosmological model, the Lambda-CDM model, which explains the nature of the universe, tells us about the existence of cold dark matter, the particles of which cannot interact with each other.
At the same time, there is a theory that suggests that dark matter may consist of self-interacting particles. These particles interact with each other using a yet unknown force that goes beyond gravity.
Scientists believe that exactly this type of dark matter exists in the Crater 2 galaxy, because, among other things, the gravity of the Milky Way should have reduced its mass much more, which is not observed. The simulations show a surprisingly close agreement between the theory of self-interacting dark matter and observations of the Crater 2 galaxy.
According to scientists, in this dwarf galaxy, despite the predictions of the Lambda-CDM model, there is no bulge of dense dark matter directed from the halo closer to the center of the galaxy.
This can again be explained by the fact that dark energy particles transfer energy between themselves during collisions and this means that the dark matter halo is aligned around the galaxy.
According to the self-interacting dark matter theory, the galaxy is likely to grow in a dark matter halo and this explains the size of Crater 2 better than the Lambda-CDM model.
Scientists have concluded that the Crater 2 galaxy’s properties challenge the main cosmological model and that it could indeed be made up of dark matter particles colliding with each other, although this contradicts modern ideas about the mysterious substance .
Now the study authors want to find other galaxies similar to Crater 2, where the same features can be observed.
