Is There a Black Hole?

Any object in the universe that accelerates is going to give off gravitational waves. For example, if two black holes are orbiting each other and then they're falling in towards each other you will see gravitational waves from those orbits. So that's very suggestive of the existence of a black hole. But it could also just be some really big dark object, not a black hole because stars don't get close enough to distinguish between scenarios.