The apparent shape of a rotating charged black hole, closed photon orbits and the bifurcation set A4


Figure 3. The apparent shadow shapes of different Kerr-Newman space-times, as seen from different latitudes ("journey to the pole"), if the black hole is apparently in front of a source of illumination with an angular size larger than that of the black hole. Proceeding each row of the matrix means decreasing latitude. Shown are cases which violate the cosmic censorship, which means in essence that

a2 + Q2 < M2,

where M denotes the black hole's mass, a its angular momentum, and Q its charge.

For the case a = 2M, Q=0, there are in addition the graphs of the effective potential V. Remarkably it shows a gorge to the anti-world of negative radius r, represented by the closed shape in the diagrams above. It is a window to the anti-world.