galactic coordinate system

(redirected from Plane of the Milky Way)
Also found in: Dictionary.
Related to Plane of the Milky Way: Galactic plane, plane earth

galactic coordinate system,

astronomical coordinate systemastronomical coordinate systems.
A coordinate system is a method of indicating positions. Each coordinate is a quantity measured from some starting point along some line or curve, called a coordinate axis.
..... Click the link for more information.
 in which the principal axis is the galactic equator (the intersection of the plane of the Milky Way with the celestial spherecelestial sphere,
imaginary sphere of infinite radius with the earth at its center. It is used for describing the positions and motions of stars and other objects. For these purposes, any astronomical object can be thought of as being located at the point where the line of sight
..... Click the link for more information.
) and the reference points are the north galactic pole and the zero point on the galactic equator; the coordinates of a celestial body are its galactic longitude and galactic latitude. In the IAU galactic coordinate system, introduced in 1958 by the International Astronomical Union, the zero point on the galactic equator has the equatorial coordinates R.A. 17h39.3m and Dec. −28°55'; this lies in the direction of the center of our galaxy, the Milky Way.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
galactic coordinate systemclick for a larger image
galactic coordinate system

galactic coordinate system

A coordinate system used to study the structure, surroundings, and contents of the Galaxy. The fundamental circle is the galactic equator and the zero point lies in the direction of the galactic center (in the constellation Sagittarius) as seen from Earth (see illustration). The coordinates are galactic latitude and longitude.

The galactic latitude (b) of a celestial body is its angular distance (from 0° to 90°) north (counted positive) or south (counted negative) of the galactic equator; it is measured along the great circle passing through the body and the galactic poles. The galactic longitude (l) of a celestial body is its angular distance (from 0° to 360°) from the nominal galactic center measured eastward along the galactic equator to the intersection of the great circle passing through the body.

The position of zero galactic longitude, i.e. the nominal galactic center, was agreed (1959) by the International Astronomical Union (IAU); it lies at RA 17h 45.6m, dec –28°56′.3 (2000.0). More recent observations suggest the actual galactic center coincides with a radio and infrared souce, Sagittarius A West, a few arc minutes from this nominal position; the nominal center is still used, however, as the zero point for galactic coordinates. The true center lies at l = –3′.34, b = –2′.75.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
The nearby associations, clusters, and nebulae from Perseus to Canis Major lie "below" the plane of the Milky Way, on the galactic-south side of the equator.
INTEGRAL was limited to looking for supermassive black holes in galaxies in the plane of the Milky Way, while Chandra, sensitive to lower-energy X rays than Swift is, could find only more-luminous black holes.--R.C.
Finally, looking "beneath" the dust clouds that lie along the plane of the Milky Way, we see the Great Sagittarius Star Cloud, a section of our galaxy's central bulge.
By tracing out the infrared signals of bright stars along the Milky Ways vast outer ring, the researchers discovered the dwarf galaxy, which is below the plane of the Milky Way.
It lies very far (some 60,000 light-years) above the plane of the Milky Way. Its newly discovered tidal tails span a huge 10[degrees] of sky in total; each tail is more than 6,000 light-years long.