Eight hundred million light years from Earth, two massive cosmic objects merged after a long in-spiraling dance, the violent outburst of energy at the end literally shaking the fabric of spacetime. One of these objects was a big black hole. The other was… well, something. It's not clear what: Either a very large neutron star on the thin hairy edge of becoming a black hole, or the smallest black hole ever seen.
Either way, this is very cool.
The event itself is called GW190814 — GW for Gravitational Wave, followed by the date: 14 August, 2019. Gravitational waves are ripples in spacetime emitted when massive compact objects merge. This was predicted by Einstein's theory of General Relativity, but these waves weren't directly detected until 2015, when a pair of merging black holes over a billion light years away from Earth were observed.
Since then about a dozen confirmed gravitational wave emitting events have been seen, including one from a pair of merging neutron stars, which was a very big deal. But for that one exception, all of these have been from two black holes that merged after orbiting each other for eons. Not only that, but the two black holes ...