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❪◑❫ Astronomical Coordinate Systems ○｜Definition｜1st｜20251119205401-00-⌔
Astronomical coordinate systems - Wikipedia
Astronomical coordinate systems
In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth’s surface).1 Coordinate systems in astronomy can specify an object’s relative position in three-dimensional space or plot merely by its direction on a celestial sphere, if the object’s distance is unknown or trivial.
Spherical coordinates, projected on the celestial sphere, are analogous to the geographic coordinate system used on the surface of Earth. These differ in their choice of fundamental plane, which divides the celestial sphere into two equal hemispheres along a great circle. Rectangular coordinates, in appropriate units, have the same fundamental (x, y) plane and primary (x -axis) direction, such as an axis of rotation. Each coordinate system is named after its choice of fundamental plane.
Printed 2026-06-28.
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Link to original Footnotes
Kanas, Nick (2021). “Star and Solar System Maps: A History of Celestial Cartography”. Research Notes of the AAS. 5 (4). American Astronomical Society: 69. Bibcode:2021RNAAS…5…69K. doi:10.3847/2515-5172/abf35c. S2CID 233522547. ↩
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