Figure 14: Escape cones in the
Schwarzschild metric, for five values of . For an observer at
radius , light sources distributed at a radius with and illuminate a disk whose angular radius is given by
Equation (107). The boundary of this disk corresponds to
light rays that spiral towards the light
sphere at . The
disk becomes smaller and smaller for . Figure 9 illustrates that the notion of escape cones is
meaningful for any spherically symmetric and static spacetime where has one minimum and no other
extrema [253]. For
the Schwarzschild spacetime, the
escape cones were first mentioned in [249, 223], and
explicitly calculated in [320]. A picture
similar to this one can be found, e.g., in [54].
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