Local Group, in astronomy, loose cluster of at least 40 nearby galaxies, including our own Milky Way galaxy, the Andromeda Galaxy, and the Magellanic Clouds. The Local Group is spread over an ellipsoidal region of space with a major axis of approximately 3 million light-years. The Milky Way galaxy, near one end of the major axis, and the Andromeda Galaxy, near the other end, are the largest members of the group; most of the galaxies are dwarf galaxies. Some of the galaxies in the group have been detected only by their infrared radiation; a dusty region in space obscures their visible light. There may be other galaxies in the Local Group that are as yet undetected. As shown by the work of G. de Vaucouleurs, the Local Group is part of a supercluster containing at least 50 separate clusters, each having from a few dozen to as many as a thousand galaxies. These groups appear to be concentrated in a plane, which indicates that the supercluster is rotating. Its center lies approximately 50 million light-years away in the direction of the constellation Virgo, and it is known as the Virgo Supercluster. It has since been determined that the Virgo Supercluster is part of the much larger Laniakea Supercluster, which spans some 500 million light-years.
The Columbia Electronic Encyclopedia, 6th ed. Copyright 2012, Columbia University Press. All rights reserved.
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