A “spinning” black hole is called a Kerr black hole; it is described by only two physical properties: mass and angular momentum. The Schwarzschild black hole, which has zero angular momentum, is a special case of the Kerr black hole. The amount of angular momentum a black hole may carry is limited by the black hole’s mass; the maximum magnitude of the angular momentum is proportional to the mass.
A Kerr black hole’s gravitational field has an axis of symmetry that can be thought of as an axis of rotation. The angular momentum vector is in the direction of this axis. The gravitational field is also mirror-symmetric about an equatorial plane that contains the black hole’s center. The angular momentum vector is perpendicular to the equatorial plane. As the angular momentum goes to zero, the gravitational field becomes spherically-symmetric.
(Source: Astrophysics Spectator)
Kerr black holes were postulated by the theorist, Roy Kerr in the 1960s. He postulated that a rotating star could collapse into a black hole with a rotating ring of neutrons at its center rather than the usual singularity. Kerr believed that since there wasn’t a singularity at the center, one might be able to travel through the black hole without being crushed by the singularity. Another theoretically possible scenario is that a person could enter the Kerr black hole and exit through a white hole on the other side (a white hole would actually push everything away from it using some form of exotic matter with negative energy), and, in this way, one could travel through spacetime.
While white holes may be theoretically possible, there is absolutely no evidence to support their existence. Many theorists do not believe there is any way to pass through a black hole and that even if it were possible, one would be torn apart by the enormous tidal forces well before reaching the singularity.
(Source: NASA)
