A nearby galaxy called Crater II that orbits the Milky Way galaxy may provide clues about dark matter. Dark matter makes up most of the matter in the universe but has never been directly detected.
Dark matter is usually thought to be “cold” and collisionless, but some theories suggest it could be “self-interacting” dark matter (SIDM) where particles interact via an unknown force.
Crater II does not have the dense dark matter “cusp” at its center predicted by normal cold dark matter models. SIDM could explain this if collisions between particles even out the halo.
Crater II is also larger than expected given tidal forces from the Milky Way. SIDM simulations show it could maintain its size and density profile with self-interacting particles.
The properties of Crater II provide some of the best evidence so far to support SIDM theories over cold dark matter. Further observations of galaxies like Crater II could help confirm if dark matter has unknown forces between particles.
Source: Space
