| a heavy, dense body, as a galaxy, that lies along our line of sight to a more distant object, as a quasar, and whose gravitational field refracts the light of that object, splitting it into multiple images as seen from the earth. |
| gravitational lens
A massive celestial object, such as a galaxy, whose gravity can act as a lens that functions to bend and focus the light of a more distant object. This results in a magnified, distorted, or multiple image of the original light source for a distant observer. |