With the Kerr metric in hand, we can take a closer look at the space-time around black holes. It helps to see how they can actually form, and it will provide information on how they might be detected. You’ll recall that explosions at the end of life for stars less than 5 times the mass of the sun create planetary nebula and leave behind white dwarfs. In these stars, electron exclusion pressure is enough to counteract the inward force of gravity. Supernova explosions at the end of life of stars more than 5 times the mass of the sun leave behind a neutron star. In these stars, electron pressure is insufficient to overcome the force of gravity, but neutron exclusion pressure is. But if a star is greater than 30 times the mass of the sun, even neutron exclusion pressure won’t do the trick. In fact, there is no known force that will counteract the inward force of gravity for such a supernova or hypernova exploding star.