Like the Big Bang, black holes are an astronomical staple. Most scientists and laymen assume that black holes are proven, well-observed denizens of the cosmos. Let us take a skeptical look. In 1939, R. Oppenheimer and H. Snyder showed on paper that a massive star could collapse and create a black hole, assuming the correctness of stellar theories and General Relativity.
Black holes are also singularities, and singularities make scientists nervous.
In the black-hole singularity, thousands of stars are swallowed and compressed into an infinitesimally small volume. This grates against common sense. Adding to these problems are nagging doubts about General Relativity, which underpins black-hole theory. Despite all these qualms, black holes have become a fixture of astronomy because they promise to explain the incredibly powerful energy sources seen in the cores of galaxies. And even if YES, there are not nearly enough of them to satisfy theory.