A galaxy a hop, skip, and four billion light-years away from us is home to three enormous black holes at its center.
This is an extremely rare occurrence, and only four are known to exist, Scientific American says. This newly discovered system has two black holes orbiting each other about 450 light-years apart (this is considered close), with a third farther out. The central pair whip around each other at 300 times the speed of sound on Earth. Eventually gravity will pull all three of the black holes closer together; one day, they could even merge.
Scientists would like to find out if this system is the right place to look for gravitational waves, which are space-time ripples predicted by Albert Einstein to exist based on the theory of general relativity.