It's proof that there's a ton of mass in the dark part of the picture (cause stuff is orbiting it). It's also proof that the thing at the center isn't outputtin

It's proof that there's a ton of mass in the dark part of the picture (cause stuff is orbiting it). It's also proof that the thing at the center isn't outputting a significant amount of radio waves. If you know the mass, and the volume, that's enough to say it has to be of black hole density.