Double quasar

A pair of quasars may be referred to as a double quasar, if they appear close to each other in the sky. This pairing may result in a chance alignment, physical proximity, actual close physical interaction, or effects of gravity bending the light of a single quasar into two.

Optical double quasar

When two quasars are so nearly in the same direction as seen from Earth that they appear to be a single quasar to the naked eye but may be separated by the use of telescopes, they are referred to as a double quasar. These are two different quasars, and not the same quasar that is gravitationally lensed. This configuration is similar to the optical double star.

Physical double quasar

Quasar pair

Two quasars, a quasar pair, may be closely related in time and space, and be gravitationally bound to one another. These may take the form of two quasars in the same galaxy cluster. This configuration is similar to two prominent stars in a star cluster.

Binary quasar

Two quasars, a binary quasar, may be closely linked gravitationally, and form a pair of interacting galaxies. This configuration is similar to that of a binary star system.

Double-image quasar

Two images of the same quasar may appear in the sky due to gravitational lensing. This is caused by a large mass between the quasar and Earth that bends light from the quasar, forming two paths, and so two images.

ee also

* Einstein ring