What happens inside a black hole stays inside a black hole, but what happens inside a black hole’s “sphere of influence”—the innermost region of a galaxy where a black hole’s gravity is the dominant force—is of intense interest to astronomers and can help determine the mass of a black hole as well as its impact on its galactic neighborhood.
Source:
https://phys.org/news/2019-08-alma-black-hole-sphere.html