Narrow Results

We study shadows cast, under some circumstances, by a certain class of rotating wormholes and explore the dependence of the shadows on the wormhole spin. We compare our results with that of a Kerr black hole. For small spin, the shapes of the shadows cast by a wormhole and a black hole are nearly identical to each other. However, with increasing values of the spin, the shape of a wormhole shadow start deviating considerably from that of a Kerr black hole. Detection of such considerable deviation in future observations may possibly indicate the presence of a wormhole. In other words, our results indicate that the wormholes which are considered in our work and have reasonable spin can be distinguished from a black hole, through the observation of their shadows.

This article summarizes how to calculate analytically the shadow of a Kerr–Newman– NUT black hole with a cosmological constant. The essential point is the existence of (unstable) spherical light rays in a region K because they determine the boundary of the shadow. Finally, the analytical formulas for the boundary of the shadow are used to calculate its angular diameter for different geometries.