| gravitational lens |
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A massive object, such as a galaxy, which has the effect of distorting the appearance and/or magnifying the image of more distant objects that are in the same line of sight, or very close to it. The paths of the light rays from the distant light source are bent in the gravitational field of the object acting as a gravitational lens in a manner similar to the bending of light rays by refraction when they pass through a glass lens. A number of examples of the phenomenon are known, in both visible light and radio maps. These include double and multiple images of quasars and clusters of galaxies in which the images of many members are distorted into concentric arcs. The natural magnification produced by a gravitational lens makes it possible to obtain detailed spectra of some remote objects that would otherwise have been too faint. On a smaller scale, the phenomenon of microlensing may be observed when a dark stellar-sized object crosses the line of sight to a more distant star. See also: Einstein ring, General Relativity. |