Celestial equator

The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space. As result of the Earth's axial tilt, the celestial equator is inclined by ~23.5° with respect to the ecliptic plane.

An observer standing on the Earth's equator visualizes the celestial equator as a semicircle passing directly overhead through the zenith. As the observer moves north (or south), the celestial equator tilts towards the southern (or northern) horizon. The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus the observer always sees the ends of the semicircle disappear over the horizon exactly due east and due west, regardless of the observer's position on Earth. (At the poles, though, the celestial equator would be parallel to the horizon.)

Celestial objects near the celestial equator are visible worldwide, but they culminate the highest in the sky in the tropics. The celestial equator passes through these constellations:

ee also

* Celestial pole
* Celestial sphere


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Look at other dictionaries:

  • celestial equator — n. the great circle formed on the celestial sphere by extending the plane of the earth s equator: see DECLINATION …   English World dictionary

  • celestial equator — Astron., Navig. the great circle of the celestial sphere, lying in the same plane as the earth s equator. Also called equator, equinoctial, equinoctial circle, equinoctial line. [1870 75] * * * …   Universalium

  • celestial equator — The great circle of the celestial sphere, in which all points are 90° from the poles. It is the plane of the earth’s equator projected onto the celestial sphere. Also called equinoctial …   Aviation dictionary

  • celestial equator — noun A great circle on the celestial sphere, coincident with the plane of earths equator …   Wiktionary

  • celestial equator — celes′tial equa′tor n. astron. naut. navig. the great circle of the celestial sphere, lying in the same plane as the earth s equator • Etymology: 1870–75 …   From formal English to slang

  • celestial equator — noun Date: 1848 the great circle on the celestial sphere midway between the celestial poles …   New Collegiate Dictionary

  • celestial equator — noun the great circle on the celestial sphere midway between the celestial poles • Syn: ↑equinoctial circle, ↑equinoctial line, ↑equinoctial • Derivationally related forms: ↑equinoctial (for: ↑equinoctial) …   Useful english dictionary

  • celestial equator — noun the projection into space of the earth s equator …   English new terms dictionary

  • celestial equator — imaginary circle which separates the celestial sphere into two equal halves …   English contemporary dictionary

  • celestial equator — /səˌlɛstiəl əˈkweɪtə/ (say suh.lesteeuhl uh kwaytuh) noun Navigation, Astronomy a great circle of the celestial sphere, the plane of which is perpendicular to the axis of the earth …   Australian English dictionary


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