[azernik]

We have direct proof of:

* extremely large masses

* in very small volumes

* that are not, themselves, emitting anything

It could be many things, but they pretty much all fit the definition of "black hole".

[WJW]

I think this is as definitive a proof we'll get until we get close enough to directly measure Hawking radiation. Of course, by that time we should also be close enough to "see" the black hole directly...