A groundbreaking new theory posits that the mysterious dark matter is made up of particles that interact with each other through a “dark force.” If this is true, it could explain the intense densities we observe in dark matter haloes surrounding galaxies. Isn’t that intriguing?
The existence of self-interacting dark matter (SIDM) offers an alternative to cold dark matter theories, suggesting that the elusive substance is composed of massive, slow-moving particles that do not interact. These cold dark matter models have been unable to solve two puzzles concerning dark matter haloes, until now!
“The first is a high-density dark matter halo in a massive elliptical galaxy. The density is so high that it is very unlikely in the popular cold dark matter theory,” shared Hai-Bo Yu, team leader and a professor of physics and astronomy at the University of California, Riverside.
The second puzzle is that dark matter haloes of ultra-diffuse galaxies have extremely low densities and are difficult to explain using the cold dark matter theory.
Related: Dark matter may be hiding in the particle jets of the Large Hadron Collider
The haloes
Dark matter remains a major enigma for scientists because it represents around 85% of matter in the universe, yet it is nearly invisible due to its lack of interaction with light. Surprising, right? It cannot be traditional matter composed of protons and neutrons. No, dark matter must be made from something else. Fascinating, isn’t it?
Scientific evidence suggests the existence of dark matter as a result of its gravitational effects. This evidence enables scientists to infer its presence, despite being unable to observe it directly. It alters the path of light traveling past these dark matter-wrapped galaxies, known as gravitational lensing. This allows astronomers to determine the properties of dark matter haloes, as well as their density and effects on surrounding matter.
Gravitational lensing is the reason we know that galaxies are surrounded by haloes of dark matter which extend beyond their visible matter. And it provides crucial information about the effects of dark matter on the properties of galaxies and their surroundings.
