galactic coordinate system (redirected from Galactic longitude)

galactic coordinate system

The coordinate system in which a celestial object's position on the celestial sphere is described in relation to the structure of the Milky Way galaxy. An object's galactic longitude is measured along the galactic equator, a great circle on the celestial sphere that follows the band of the Milky Way. The galactic equator, also called the galactic circle, is inclined at an angle of approximately 62° to the celestial equator; distances are measured along it beginning at a point in the constellation Sagittarius lying in the direction of the Milky Way's nucleus. The galactic poles are the two points where a perpendicular line through the middle of the plane of the galactic equator intersect the celestial sphere. An object's galactic latitude is measured in degrees north or south of the galactic equator toward the galactic poles.