Gravitational lens

In a gravitational lensing scenario, light traveling from a distant astronomical source (e.g. a galaxy) to an observer is deflected by the gravitational field of an intermediate object (e.g. a cluster of galaxies), therefore designated the gravitational lens. Because of this, the observer will see the source in a direction different from the one in which the source would be observed if the gravitational lens were absent. Furthermore, it is possible for light rays to reach the observer by multiple paths, causing multiple images of the same source to appear.