in SI units). Kerr solution The surface gravity for the uncharged, rotating black hole is, simply where is the Schwarzschild surface gravity, and is the spring constant of the rotating black hole. is the angular velocity at the event horizon. This expression gives a simple Hawking temperature of . Kerr–Newman solution The surface gravity for the Kerr–Newman solution is where is the electric charge, is the angular momentum, we define to be the locations of the two horizons and . Dynamical black holes Surface gravity for stationary black holes is well defined. This is because all stationary black holes have a horizon that is Killing. Recently there has been a shift towards defining the surface gravity of dynamical black holes whose spacetime does not admit a Killing vector (field). Several definitions have been proposed over the years by various authors. As of current, there is no consensus or agreement of which definition, if any, is correct. References External links Newtonian surface gravity Exploratorium – Your Weight on Other Worlds Gravity Black holes General relativity