Static (Schwarzschild) Black Holes
The static black hole is the simplest of all types. It has no charge, and it remains stationary in space - hence the title "static". It is composed of three major areas: the photon sphere, the event horizon, and the singularity.
The Photon Sphere
The photon sphere is a region located at 1.5 times the Schwarzschild radius ( R = 2MG/c^2 where M is the mass of the object and G is the Gravitational Constant). In this small region of space, light rays can orbit, albeit very unstably, around the singularity of the black hole. The orbital velocity required to keep from falling into the black hole's gravity well is equal to the speed of light (3.0 x 10^8 m/s), so theoretically a light ray could orbit in the photon sphere forever. Unfortunately, there are a lot of light rays orbiting in this region at the same time, and this leads to a great deal of instability, so the chance that one light ray will stay in orbit without being deflected into or out of the black hole is very slim.
The Event Horizon
The event horizon is located at the Schwarzschild radius, closer to the singularity of the black hole. Since is it closer to the source of gravity, the orbital velocity required to maintain a constant distance from the singularity increases, surpassing the speed of light. Consequently, the escape velocity also exceeds 3.0 x 10^8 m/s. Einstein's Theory of General Relativity states that nothing can travel at a speed greater than that of light; therefore, nothing, not even light rays, can escape a black hole after crossing the event horizon.
The event horizon is an interesting phenomenon. To an outside observer watching the movement of an object toward the singularity of a black hole, the event horizon is the distance at which the observer would notice that time seemed to "stop" for the object. This, of course, is an optical illusion created by the black hole's immense gravity well.
Up until that point, the observer would have seen the object appear to gradually "slow down", due to a curvature in space-time(there are other effects, but we'll save that for the tour). At the event horizon, this warpage of space-time becomes so extreme that the axes representing space and time(like the x and y axes of a 2D graph) actually flip. Space and time switch places, and the singularity of the black hole is no longer a point in space, but an unavoidable point in the very future of the object travelling toward it.
The Singularity
The singularity is located at the centre of a black hole. Simply put (or perhaps not so simply), it is the point at which curvature of space-time is infinite. This will perhaps be better explained in the Related Topics section, as it is complicated and easier to understand in the context of relativity.
A Quick Note on Static Black Holes: Static black holes are largely a thought device used to understand other kinds of black holes. They are very rare in occurrence, as most bodies in space do not remain still, and therefore the black holes they create would likewise not remain still.
On to Charged Black Holes!
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