The Kerr black hole is a unique variety of black hole proposed by New Zealand mathematician Roy Kerr in 1963. Also known as the Kerr ring, this theory puts forth the idea of a rotating black hole and hinges on the concept of neutron stars, which are massive collapsed stars the size of Manhattan but with the mass of the Earth's sun.
Most scientists agree that circling a traditional black hole long enough or flying into one would ultimately crush the traveller. However, Kerr's version of the black hole theorizes that if dying stars collapse into a rotating ring of neutron stars, the outward force of the stars prevents them from turning into a singularity. Therefore, it would be possible to enter a Kerr black hole without having to worry about the infinite gravitational force at the center.
Instead, scientists believe that one would pass through the center and exit through a white hole. Instead of pulling everything into its gravitational force, the white hole would push everything away from it, similar to an exhaust system. Kerr black holes are completely theoretical. However, if they were real, they might allow a= time traveller a one-way ticket into the future or the past.