The galactic coordinate system is a spherical coordinate system centered on the Sun used to indicate directions into the celestial sphere, fixed to the galactic plane, and the line from the Sun to the galactic center. Spherical elements:
A current standardization of the system, IAU galactic coordinate system, was approved by the International Astronomical Union (IAU) in 1958 based upon the data available at the time regarding the locations in the celestial sphere of the galactic plane and the direction toward the galactic center. Subsequent measurement improvements might provide for a "truer" system, but waiting a while between adjustments assists in sharing research.
Rectangular coordinates based on the same plane and line are also used.