El Gordo

NASA Hubble Hubble image of the El Gordo supercluster with the estimated dark matter highlighted in blue. 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 counter-example 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.1 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…