Black holes shadows: unveiling the physics behind the image of M87

In this article we analyze the shadows of spinning Kerr black holes and their connection with the first image of a black hole obtained by the international collaboration Event Horizon Telescope. We obtain analytically the shadow of a rotating black hole from the spherical photon orbits. We also use the method known as backwards ray-tracing to illustrate the visual perception of an observer in the presence of a spinning black hole with and without an accretion disk.