The Fingerprints of Black Holes – Shadows and their Degeneracies

Claudio Paganini, Max Planck Institute for Gravitational Physics, Germany

First I will introduce the concept of the shadow of a black hole and what it means for the shadows of two observers to be degenerate. I will then present results showing that no continuous degenerations exist between the shadows of observers at any point in the exterior region of any Kerr-Newman black hole spacetime of unit mass. Therefore an observer can, by measuring the black holes shadow, in principle determine the angular momentum and the charge of the black hole under observation, as well as his radial distance from the black hole and his angle of elevation above the equatorial plane.