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, e.g., specifying what direction in the celestial sphere is toward the galactic center, was approved by the International Astronomical Union (IAU) in 1958 based upon the data available at the time, making it the IAU Galactic Coordinate System. Subsequent measurement improvements might for provide a "truer" system, but refraining from frequent improvements assists in sharing research.
Rectangular coordinates based on the same plane and line are also used.
Celestial Coordinate System