Also found in: Dictionary, Wikipedia.
Related to Local Group: Local Supercluster
Local Group,in astronomy, loose cluster of at least 40 nearby galaxiesgalaxy,
large aggregation of stars, gas, dust, and usually dark matter, typically containing billions of stars. Recognition that galaxies are independent star systems outside the Milky Way came from a study of the Andromeda Galaxy (1926–29) by Edwin P.
..... Click the link for more information. , including our own Milky WayMilky Way,
the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if not blocked by the horizon, it would be seen as a circle around the entire sky.
..... Click the link for more information. galaxy, the Andromeda GalaxyAndromeda Galaxy,
cataloged as M31 and NGC 224, the closest large galaxy to the Milky Way and the only one visible to the naked eye in the Northern Hemisphere. It is also known as the Great Nebula in Andromeda. It is 2.
..... Click the link for more information. , and the Magellanic CloudsMagellanic Clouds
, two dwarf galaxies located in the far southern sky and visible to the unaided eye; they are classified as irregular because they show no definite symmetry or nucleus.
..... Click the link for more information. . 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 radiationinfrared radiation,
electromagnetic radiation having a wavelength in the range from c.75 × 10−6 cm to c.100,000 × 10−6 cm (0.000075–0.1 cm).
..... Click the link for more information. ; 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™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
Local GroupThe cluster of galaxies of which our Galaxy is a member. It is a comparatively small cluster with around 40 known members and some other possible members, most of which are dwarf ellipticals or irregular galaxies (see table). The most massive members are the Galaxy and the Andromeda galaxy (M31). The other major members are the Triangulum spiral (M33) and the Large Magellanic Cloud. The group is irregular in shape with two notable subclusters: one around our Galaxy and the Magellanic Clouds, the other around M31 and M33.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Local Group[′lō·kəl ′grüp]
A group of at least 20 known galaxies in the vicinity of the sun; the Andromeda Spiral is the largest of the group, and the Milky Way Galaxy is the second largest.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.