Scientists Reconsider Dark Matter Theory Amid Growing Cosmological Mysteries

For many years, scientists were aware that an invisible force was holding the universe together, which turned out to be dark matter, comprising about 85% of matter in the universe, observable only through its gravitational effects. In a model that persisted for decades, dark matter was described as cold and solitary; the particles do not interact with each other but only drift past each other. However, there are three cosmological problems that are forcing scientists to look at things differently.

When Dark Matter Talks to Itself

However, a newly published article in Physical Review Letters suggests a different recipe: self-interacting dark matter (SIDM). SIDM allows the collision of dark matter particles to collide with each other, allowing gravothermal collapse, which makes them form dense cores – something that could not be done using the conventional cold model. Gravothermal collapse refers to the phenomenon wherein energy diffuses away from the halo, leading to the heating up and increasing density of the inner core. 

Three Puzzles, One Elegant Fix

The SIDM clumps display a total mass which equals around one million solar masses. The unusual gravitational effects which researchers observe in three astrophysical systems through their study of gravitational lenses, stellar streams, and satellite galaxies can be explained through these dense SIDM clumps. The gravitationally lensed system JVAS B1938+666, together with the mysterious 'scar' which cut through the GD-1 stellar stream and the Fornax 6 star cluster from a dwarf galaxy, all demonstrate the same self-interacting particle behaviour. The same mechanism which operates through multiple cosmic scales demonstrates that SIDM exists as more than a theoretical concept because it represents the universe's most hidden secret.