How dense is a black hole? Available to Purchase

Since the discussion of black holes in introductory astronomy is usually preceded by a discussion of white dwarfs and neutron stars, increasing density is usually a recurring theme. Objects are often assumed to have to be of tremendous densities to become black holes. This is true for lower mass, smaller black holes, but calculating the required densities of larger mass black holes shows that this is not always the case. In fact, supermassive black holes, like those at the center of galaxies, can have a very low density.