Black Holes as Gravitational Mirrors

Retrolensing is a gravitational lensing effect in which light emitted by a background source is deflected by a black hole and redirected toward the observer after undergoing nearly complete loops around the black hole. In this context, we explore the possibility of seeing objects of the solar system in past eras through telescope observations by using black holes as a gravitational mirror. We consider the motion of the light around Reissner–Nordström space–time and discuss the properties of the trajectories of boomerang photons. It was shown that, depending on the angle of emission and the position of the source, the photons could return to the emission point. Afterward, we explore the possibility of considering the returning photons in retrolensing geometry where the observer is between the source and the lens in which two classes of black holes are explored: The supermassive Sgr A* black hole at the galactic center and a nearby stellar black hole. For the first time in the literature, we propose the study of the returning photons of planets instead of stars in retrolensing geometry.