Pair of Supermassive Black Holes Discovered on a Collision Course

Simons Foundation, July 2019

Astronomers have spotted a distant pair of titanic black holes headed for a collision. Each black hole’s mass is more than 800 million times that of our sun. As the two gradually draw closer together in a death spiral, they will begin sending gravitational waves rippling through space-time. Those cosmic ripples will join the as-yet-undetected background noise of gravitational waves from other supermassive black holes.

Top of Reddit's /r/science for July 10, 2019.