Predictions by general relativity that light passing close to the Sun might be deflected were confirmed in 1919. In addition, light from a distant object may pass close to objects other than the Sun and be deflected by them. In particular, they may be deflected by a massive galaxy. If some object is behind a massive galaxy, as seen from Earth, deflected light may reach the Earth by more than one path. Operating like a lens that focuses light along different paths, the gravity of the galaxy may make the object appear multiple; an example of such arcs and rings is shown below.

Excerpt from the Encyclopedia Britannica without permission.