Massive El Gordo galaxy cluster

Strange behavior in a massive cluster of merging galaxies could be explained if dark matter, the universe's most mysterious stuff, can collide with itself. However, the most favored model of cosmology right now is the cold dark matter (CDM) model — and it suggests that dark matter, which is effectively invisible because it doesn't interact with light, is not self-interacting. To get to the bottom of this conundrum, researchers from the Astrophysics and Cosmology group of Italy's Scuola Internazionale Superiore di Studi Avanzati (SISSA) set about simulating what is happening within the massive galactic cluster "El Gordo" (which literally means "the Fat One" in Spanish). It's located around 7 billion light-years from Earth