Supergalactic coordinates are coordinates in a spherical coordinate system which was designed to have its equator aligned with the supergalactic plane, a major structure in the local universe formed by the preferential distribution of nearby galaxy clusters (such as the Virgo cluster, the Great Attractor and the Pisces-Perseus supercluster) towards a (two-dimensional) plane. The supergalactic plane was recognized by Gerard de Vaucouleurs in 1953 from the Shapley-Ames catalogue, although a flattened distribution of nebulae had been noted by William Herschel over 200 years earlier. See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ... This article describes some of the common coordinate systems that appear in elementary mathematics. ... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... A sky field near some of the brighter galaxies in the Virgo cluster. ... The Great Attractor is a gravitational anomaly in intergalactic space, at the centre of the local supercluster, which is drawing in galaxies over a region hundreds of millions of light years across. ... This article is in need of attention from an expert on the subject. ... Gérard Henri de Vaucouleurs (April 25, 1918–October 7, 1995) was a French-American astronomer. ... The Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. ... Sir Wilhelm Friedrich Herschel, FRS (Hanover, November 15, 1738 – August 25, 1822 Slough, then in Buckinghamshire now in Berkshire) was a German-born British astronomer and composer who became famous for discovering the planet Uranus, and made many other astronomical discoveries. ...

By convention, supergalactic latitude and supergalactic longitude are usually denoted by SGB and SGL, respectively, by analogy to b and l conventionally used for galactic coordinates. The zero point for supergalactic longitude is defined by the intersection of this plane with the galactic plane. Many galaxies, including the Milky Way in which our Sun and Earth are located, are disk-shaped: the majority of their visible mass (excluding possible dark matter) lies very close to a plane. ...

Bold text==Definition==

• The north supergalactic pole (SGB=90°) lies at galactic coordinates (l=47.37°, b=+6.32°). In the equatorial coordinate system (epoch J2000), this is approximately (RA=18.9 h, Dec=+15.7°).
• The zero point (SGB=0°, SGL=0°) lies at (l=137[[.37°, b=0°). In the equatorial coordinate system (J2000) this is approximately (2.82 h, +59.5°).]]

The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () or hour angle () It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ... The word epoch can mean either an interval of time, or a particular point in time used as a reference point. ... The J2000. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () or hour angle () It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ...

See also

• Coordinate system

[[[[[[ == == == == == See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ...

==External references

• precise definition by Lahav et al 2000, MNRAS, 312, 166 == == == == == ==]]]]]]