Unexpected quartet of quasars

Smithsonian : Quasars are massively bright, short-lived objects thought to be the result of material falling into supermassive black holes. Finding two of them near each other is unusual, but Joseph Hennawi of the Max Planck Institute for Astronomy in Germany and his colleagues were even more surprised to find four within 600 000 light-years of each other. The grouping was found as part of a survey of quasars using the Keck observatory in Hawaii. The images also revealed that all four are inside a large cold cloud of gas. Only about 10% of quasars are in similar clouds; hot clouds are much more common. That suggests current models of quasar formation may need to be adjusted. Hennawi’s group thinks that the quasar quartet may represent the early stages of a galaxy cluster forming, because the region surrounding the collection has many more galaxies in it than does the average region of space.