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galactic coordinate system
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Columbia Encyclopedia
galactic coordinate system, astronomical coordinate system in which the principal axis is the galactic equator (the intersection of the plane of the Milky Way with the celestial sphere) 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.
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Wikipedia
The galactic coordinate system is a spherical reference system on the sky which is centered on the Sun and is aligned with the apparent center of the Milky Way galaxy. The "equator" is aligned to the galactic plane. Similar to geographic coordinates, positions in the galactic coordinate system have latitudes and longitudes.
Definition
The International Astronomical Union (IAU) defined the galactic coordinate system in reference to the Equatorial coordinate system in 1959. The north galactic pole is defined to be at right ascension , declination (B1950), and the zero of longitude is the great semicircle that originates from this point along the line in position angle 123° with respect to the equatorial pole. The galactic longitude increases in the same direction as right ascension. Galactic latitude is positive towards the north galactic pole, the poles themselves at ±90° and the galactic equator being zero.The equivalent system referred to J2000 has the north galactic pole at (J2000), the zero of longitude at the position angle of 122.932°. The point in the sky at which the galactic latitude and longitude are both zero is (J2000). This is offset slightly from the radio source Sagittarius A*, which is the best physical marker of the true galactic center. Sagittarius A* is located at (J2000), or galactic longitude , galactic latitude .
Nomenclature
The symbols l and b are used to represent the galactic longitude and latitude, respectively.
See also
References
External links
- Equatorial/Galactic conversion tool
- Galactic coordinates, The Internet Encyclopedia of Science
- Universal coordinate converter
- Fiona Vincent, Positional Astronomy: Galactic coordinates, University of St Andrews
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Last updated on Tuesday July 15, 2008 at 13:26:42 PDT (GMT -0700)
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This article is licensed under the GNU Free Documentation License.
Last updated on Tuesday July 15, 2008 at 13:26:42 PDT (GMT -0700)
View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation
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