Even though dark matter comprises 85 per cent of all matter in the universe, it does not interact with light and can only be seen through the gravitational influence it has on light and other matter. So what does dark matter look like?
Recently, a team from Harvard & Smithsonian Center for Astrophysics carried out a detailed simulation of the dark matter cosmos, resulting in some surprising observations.
As per a statement released on Universe Today, the accuracy of any dark matter simulation depends on the assumptions one makes about it. In this case, the team assumed that dark matter consists of weakly interacting massive particles (WIMPs) with a mass about 100 times that of a proton.
According to study authors, WIMPs are one of the more popular theories of dark matter and similar computer simulations of WIMP dark matter have been done before. What set apart this simulation was that it was exceptionally high in resolution and featured on a scale ranging across thirty orders of magnitude.
Researchers found that dark matter is formed in halos around galaxies. They also found that the haloes developed across all mass scales, ranging from small, planet mass haloes to galactic one and even massive haloes that form around clusters of galaxies.
Scientists observed that all the haloes had a similar structure where they are dense towards the centre and start diffusing at the edges. The fact that this happened at all scales makes it an explicit feature of dark matter.
The researchers revealed that while the small scale haloes are too small to be detected through gravitational influence on light, they could help answer how matter interacts with itself. According to them, one notion about dark matter is that when particles of a dark matter collide, they emit gamma radiations. Gamma ray observations have also been seen emitted from the centre of the Milky Way, which could be caused by dark matter.
The simulation showed that most gamma radiation was produced by smaller haloes. Since the scale of a halo would affect the energy spectrum of the gamma rays, this model makes precise predictions about the gamma-ray surplus one should see both in the Milky Way and other galaxies.