Three-Headed Monster

A three-headed monster lurks in the constellation Bootes — a galactic collision involving three supermassive black holes. And two of them are closer together than any other supermassive black holes yet seen.
The whole complex consists of two galaxies that are several billion light-years away, so we see them as they looked at about the time that Earth was taking shape.
The two galaxies are in the process of merging. Each is roughly as big and heavy as our own galaxy, the Milky Way. They contain hundreds of billions of stars.
Earlier observations had shown that the heart of each galaxy contained a supermassive black hole. Recently, though, astronomers used a network of radio telescopes to produce ultra-sharp views of the system. They found that one of the galaxies actually has two giant black holes at its center. Each one is roughly a hundred million times as massive as the Sun. And they’re only about 450 light-years apart. That’s closer than many of the individual stars we see in the ni