Supergalaxy

supergalaxy [¦sü·pər′gal·ik·sē]

(astronomy)

A hypothetical very large group of galaxies which together fill an ellipsoidal space.

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Supergalaxy 

a large cluster of galaxies. Supergalaxies are detected in the concentration of bright galaxies near the great circle of the celestial sphere that intersects the galactic equator at a nearly 90° angle. Approximately two-thirds of all galaxies brighter than visual stellar magnitude 12 are located near this circle in a band 12° wide, which amounts to only 10 percent of the celestial sphere. The fainter the galaxies, the lower the concentration near the circle. Distant galaxies are not part of super-galaxies.

The diameter of supergalaxies is estimated at 20–30 megapar-secs, which is much larger than the diameter of ordinary clusters of galaxies. The number of galaxies within a superga-laxy runs into many thousands. A supergalaxy also has a strongly flattened shape that differs from the shape of ordinary clusters of galaxies. The plane passing through the circle of concentration can be considered as the supergalaxy’s plane of symmetry. Not only optical galaxies but also radio galaxies exhibit a concentration in this plane. The cluster of galaxies in the constellation Virgo is located approximately in the central region of a supergalaxy. Our galaxy, together with the local group of galaxies, is apparently also a part of a supergalaxy, but it is located near the periphery of the supergalaxy. As of 1976, the question of whether a supergalaxy is a stable or a temporary formation had not been resolved.

REFERENCCE

Agekian, T. A. Zvezdy, galaktiki, metagalaktika. Moscow, 1966.

T. A. AGEKIAN