The quasistellar object, the pulsar, the neutron star have all come onto the scene of physics within the space of a few years. Is the next entrant destined to be the black hole? If so, it is difficult to think of any development that could be of greater significance. A black hole, whether of “ordinary size” (approximately one solar mass,), or much larger (around to as proposed in the nuclei of some galaxies) provides our “laboratory model” for the gravitational collapse, predicted by Einstein's theory, of the universe itself.
According to present cosmology, certain stars end their careers in a total gravitational collapse that transcends the ordinary laws of physics.