This week, a new image was released of a black hole in the galaxy M87, 6.5 billion times more massive than our sun. It is the first to show light and dark regions indicating the existence of matter and energy that falls into it. It’s also the second black hole to be pictured, following the release of the first in 2019, and the third such image to ever be produced by telescopes worldwide.
But the thing about a black hole is that based on Einstein’s equations there’s not much to see inside it. If something falls into a non-rotating black hole it will eventually hit the event horizon and, well, splat. Once that happens, no matter or light can escape (unless it somehow starts from inside the singularity, which is a violation of relativity).
However, when two rotating black holes get close enough to hit each other they emit gravitational radiation that makes their orbits decay and make them spiral in closer together. In fact, that’s what happened in the black hole event recently announced. It’s a big deal because it shows that the theory of black holes as static solutions to Einstein’s equations isn’t quite right. It can be modified, though.
