“Having caught a massive galaxy cluster in throes of formation is spectacular in and of itself. But, the fact that this is happening so early in the history of the universe poses a formidable challenge to our present-day understanding of the way structures form in the universe."
“How this assembly of galaxies got so big so fast is a bit of a mystery, it wasn’t built up gradually over billions of years, as astronomers might expect. This discovery provides an incredible opportunity to study how galaxy clusters and their massive galaxies came together in these extreme environments.”