This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Seven billion light-years from Earth, there is an unexpected cluster of galaxies. It has two regions in the process of colliding with each other with a combined mass of more than two quadrillion solar masses.
Given its mass, the distant cluster has been nicknamed El Gordo, the Fat One. What makes it unusual is that it's extraordinarily large for that period of the universe. How did such a large supercluster form so early?
El Gordo is so surprising that some astronomers hold it as a counterexample to the standard model of cosmology. It's difficult to explain how cold dark matter in an inflationary universe could generate a large supercluster so quickly. A new study looks at how self-interacting dark matter could explain it all.
Dark matter makes up the bulk of mass in the cosmos. It doesn't interact strongly with light, if at all, hence the name. This also means that dark matter doesn't interact strongly with regular matter, since most matter interactions are electromagnetic in nature.
One of the key questions, however, is whether dark matter can interact strongly with itself. The most popular view is that dark matter isn't self-interacting. This is because observations show dark matter is mostly cold, meaning that dark matter particles don't have a lot of kinetic energy.
If dark matter particles could collide with each other, then they would stay warm, just as regular matter can heat up when it collides. Self-interacting dark matter (SIDM) could create an early supercluster like El Gordo, but it would also produce plenty of warm dark matter. To overcome this problem, this new study proposes a two-state dark matter interaction.
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