Images of Black Holes Viewed by a Distant Observer

Abstract

We describe the possible forms of black hole images viewed by a distant observer (or a telescope) on the celestial sphere. These images are numerically calculated based on general relativity and the equations of motion in the Kerr–Newman metric. A black hole image is a gravitationally lensed image of the black hole event horizon. It may be viewed as a black spot on the celestial sphere, projected inside the position of a classical black hole shadow. In the nearest future it will be possible to verify modified gravity theories by observations of astrophysical black holes with Space Observatory Millimetron.