Analyzing black hole shadows on Kerr spacetimes

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Written by Marius Oancea

The shadow of a black hole can be defined as the innermost trajectory on which light from a background source passing a black hole can reach the observer. We prove that for any observer in the domain of outer communication of any subextremal Kerr spacetime the shadow of the black hole is represented by a smooth curve on the celestial sphere of that observer. Furthermore, we present numerical evidence that the radial degeneracy of the black hole shadow is broken in Kerr spacetimes for observers away from the symmetry axis. These results are available at https://arxiv.org/abs/1611.06927.

Joint work with Claudio Paganini and Blazej Ruba.