Power source for active galactic nuclei and quasars.
Searches find supermassive black holes in nearly every nearby bright galaxy.
We see most all of them at large redshifts. Very few active galaxies are nearby today. Black Hole Gravity Black Holes may be found only by the effects of their gravity on their surroundings. The Search Need to look close to a black hole to see the motions due to their gravity. Look for the tell-tale orbital signatures of a very massive object in the center of a galaxy.