How do you study something invisible? This is a challenge facing astronomers studying the subject of darkness. Although dark matter contains 85% of all things in the universe, it does not interact with light. It can only be seen by the effect of gravity on light and other things. Attempts to find a dark matter directly on Earth have so far failed to make matters worse.
Despite the insidious quality of dark matter, we have learned many things about it. We know that it is not only dark but also cold. As a result, they clump together, forming seeds of galaxy clusters. It also often forms halo around galaxies, forming most of the mass of the galaxy. However, there are still many unanswered questions about dark matter, so astronomers often develop new models for dark matter, comparing observations to test their accuracy.
One way to do this is through sophisticated computer simulations. Recently a team from the Harvard and Smithsonian Center for Astrophysics conducted a detailed simulation of the Dark Matter universe, and it has yielded some surprising results.
The accuracy of any dark matter simulation depends on the assumptions you make about dark matter. In this case, weakly large particles (WIMPs) interact with 100 times the mass of protons in the assumed team in dark matter. WIMP is one of the more popular theories for dark matter. Similar computer simulations of WIMP Dark Matter have been performed before. Still, this was a significant resolution, simulating features on a scale of up to thirty orders of magnitude.
In this simulation, dark matter is formed in the coils around the galaxies as we observe. But interestingly, it has been found that haloes have evolved in all mass scales, from small, planetary-mass haloes to galactic haloes, to giant hollows formed around clusters of galaxies. This is a similar formation of halo, where they are most ga toward towards their center, becoming more diffuse at their edges. The fact that all this happens on the scales makes it a clear feature of the dark matter.
When a small halo that can be detected by the gravitational influence of light is very small, they will be able to tell us how dark matter interacts with itself. One idea about dark matter is that when dark matter particles collide with each other, they emit gamma radiation. Some gamma-ray observations have indicated more gamma-rays coming from the center of our galaxy, which may be due to dark matter. In this particular model, most of the gamma radiation produced by the dark matter comes from small coils. The scale of a halo will affect the spectral spectrum of gamma rays, so this model makes accurate predictions about the gamma-rays we should see in both galaxies and other galaxies.
Dark matter is one of the biggest unsolved problems in modern astronomy. While we would prefer to find it directly, until it happens, simulations like this are one of the most powerful tools for better understanding of the dark matter.
Reference: Wang, J., Bose, S., Frank, CS et al. “The universal structure of dark matter closes at a mass range of 20 orders of magnitude.” Nature 585.7823 (2020): 39-42.
