Gravitational lensing is a prediction of Einstein’s general theory of relativity. It describes the situation where a foreground galaxy (or cluster of galaxies) acts like a light lens and focuses the light of a more distant background galaxy and hence magnifies it like a normal lens would do. According to the theory the lens distorts the galaxy image often looking like a cross or a ring around the closer “lensing” galaxy.
Several earth-based radio and optical telescopes and the Herschel Space Observatory were used to image an object. Shown here, in Fig. 1, is where a gravitational lens is claimed to image a very distant galaxy that is apparently still in early formation.