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An object's location expressed in the equatorial coordinate system can be transformed into the galactic coordinate system. In these equations, α is right ascension, δ is declination. NGP refers to the coordinate values of the north galactic pole and NCP to those of the north celestial pole. [5]
The poles are located at ±90° from the fundamental plane. The primary direction is the starting point of the longitudinal coordinates. The origin is the zero distance point, the "center of the celestial sphere", although the definition of celestial sphere is ambiguous about the definition of its center point.
Quadrants are described using ordinals—for example, "1st galactic quadrant", [1] "second galactic quadrant", [2] or "third quadrant of the Galaxy". [3] Viewing from the north galactic pole with 0 degrees (°) as the ray that runs starting from the Sun and through the galactic center, the quadrants are as follows (where l is galactic longitude):
The zero of longitude of galactic coordinates was also defined in 1959 to be at position angle 123° from the north celestial pole. Thus the zero longitude point on the galactic equator was at 17 h 42 m 26.603 s , −28° 55′ 00.445″ (B1950) or 17 h 45 m 37.224 s , −28° 56′ 10.23″ (J2000), and its J2000 position angle is 122.932°.
The Galactic Center, as seen by one of the 2MASS infrared telescopes, is located in the bright upper left portion of the image. Marked location of the Galactic Center A starchart of the night sky towards the Galactic Center. The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy.
The International Astronomical Union (IAU) defines the north pole of a planet or any of its satellites in the Solar System as the planetary pole that is in the same celestial hemisphere, relative to the invariable plane of the Solar System, as Earth's north pole. [1] This definition is independent of the object's direction of rotation about its ...
For a location not on this axis, there is a unique meridian plane in this axial-pencil through that location. The intersection of this plane with Earth's surface defines two geographical meridians (either one east and one west of the prime meridian , or else the prime meridian itself and its anti-meridian), and the intersection of the plane ...
Galaxies and galaxy clusters < 50 M ly away from Earth plotted in the supergalactic plane. The supergalactic coordinate system is a reference frame for the supercluster of galaxies that contains the Milky Way galaxy, referenced to a local relatively flat collection of galaxy clusters used to define the supergalactic plane.