The formula 2GM over the speed of light squared describes the Schwarzschild radius for these entities.
According to Birkhoff's theorem, one form of these phenomena is the only vacuum solution that has spherical symmetry, and these entities can be described using Penrose diagrams. The Reissner-Nordstrom metric describes the charged variety of these entities, and they can be fully described by their mass, charge, and angular momentum according to the no-hair theorem. The formula 2GM over the speed of light squared describes the Schwarzschild radius for these entities. For 10 points, name these regions of spacetime from which light is unable to escape past their event horizons.
According to Birkhoff's theorem, one form of these phenomena is the only vacuum solution that has spherical symmetry, and these entities can be described using Penrose diagrams.
Black Holes