The Shadow of a Rotating Black Hole

Abstract

The aim of this work is to provide an introduction to the field of shadows of rotating Kerr black holes. We review the mathematics of light propagation in Kerr spacetime and derive the equations describing the edge of a Kerr black hole shadow in the sky of a distant observer. We also discuss recent research concerning the possibility of determining the spin parameter a and the inclination angle θ_O of the observer from direct observations of the shadow. Finally, we showcase two applications of the theory of black hole shadows to the Event Horizon Telescope collaboration image of the supermassive black hole M87*.