Celestial Sphere

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Celestial globe[1]

The celestial sphere is an extended projection of the terrestrial globe into outer space. The ecliptic is a line running along the celestial sphere. The projection of the Earth's equator onto the celestial sphere is called the celestial equator, the North and South Poles correspond to the celestial North and South Poles.

The celestial sphere's coordinate system corresponds to the one used on Earth: The degrees of longitude find their correspondence in the right ascension, those of latitude in the declination.

The concept of a celestial sphere makes it possible to accurately locate the celestial bodies.

A celestial sphere can also refer to a physical model of the celestial sphere or celestial globe (cf. the Bürgi globe). Such globes map the constellations on the outside of a sphere, resulting in a mirror image of the constellations as seen from Earth. The oldest surviving example of such an artifact is the globe of the Farnese Atlas sculpture, a 2nd-century copy of an older (Hellenistic period, ca. 120 BC) work.

Medieval illustration of the Celestial spheres[2]

See also


Notes and References

  1. By Jost Bürgi (1594)
  2. Nicole Oresme (artist unknown), 1377