A de Vries 2000 Class. Quantum Grav. 17 123 doi:10.1088/0264-9381/17/1/309
A de Vries
Show affiliationsThe apparent shapes of various Kerr-Newman spacetimes are plotted. For this purpose the geometry of closed photon orbits is studied, forming a subset of the bifurcation set A 4 , well known in elementary catastrophe theory. One additional result is that the cosmic censorship hypothesis guarantees that the spacetime casts a shadow, whereas naked ring singularities enable the visibility of the `anti-world' of negative radii r through its interior. Moreover, the optical restrictions to the observability of the shadow of an astronomical black hole are inferred.
04.70.-s Physics of black holes
Issue 1 (7 January 2000)
Received 12 April 1999
A de Vries 2000 Class. Quantum Grav. 17 123
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