ecliptic

astronomy
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north celestial and ecliptic poles
north celestial and ecliptic poles
Key People:
Hipparchus al-Battānī
Related Topics:
Sun zodiac celestial sphere

ecliptic, in astronomy, the great circle that is the apparent path of the Sun among the constellations in the course of a year; from another viewpoint, the projection on the celestial sphere of the orbit of Earth around the Sun. The constellations of the zodiac are arranged along the ecliptic. The ecliptic is inclined at 23.44° to the plane of the celestial equator; this inclination is called the obliquity of the ecliptic. The two points of intersection of the ecliptic and the plane mark the vernal and autumnal equinoxes.

In the ecliptic system of astronomical coordinates, celestial longitude is measured in degrees east from the vernal equinox along the ecliptic. Celestial latitude is measured in degrees north (positive) or south (negative) from the ecliptic to the ecliptic poles. Each ecliptic pole is 23.44° from the corresponding celestial pole.

Star trails over banksia trees, in Gippsland, Vic., Austl. The south celestial pole, located in the constellation Octans, is at the centre of the trails.
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astronomical map: The celestial sphere
…its annual circuit is the ecliptic (so called because eclipses can occur when the Moon crosses it).
The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Erik Gregersen.