ecliptic

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ecliptic (ēklĬp´tĬk, Ĭ–), the great circle on the celestial sphere that lies in the plane of the earth's orbit (called the plane of the ecliptic). Because of the earth's yearly revolution around the sun, the sun appears to move in an annual journey through the heavens with the ecliptic as its path. The ecliptic is the principal axis in the ecliptic coordinate system. The two points at which the ecliptic crosses the celestial equator are the equinoxes. The obliquity of the ecliptic is the inclination of the plane of the ecliptic to the plane of the celestial equator, an angle of about 231/2°. The constellations through which the ecliptic passes are the constellations of the zodiac.

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e·clip·tic / iˈkliptik/ • n. Astron. a great circle on the celestial sphere representing the sun's apparent path during the year, so called because lunar and solar eclipses can occur only when the moon crosses it. • adj. of an eclipse or the ecliptic.

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ecliptic The plane of the orbit of the Earth around the Sun. It forms an angle of 23°27′ with the Earth's equator. The orbits of the planets all lie within 3.4° of this plane, except for those of Pluto (17.2°) and Mercury (7°).

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ecliptic pert. to an eclipse XIV; sb. great circle of the celestial sphere, the apparent orbit of the sun, so called because eclipses happen only when the moon is on or very near this line XIV. — L. eclīpticus — Gr. ekleiptikós (also sb.), f. ekleípein; see prec. and -IC.

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ecliptic The plane of the orbit of the Earth around the Sun. It forms an angle of 23°27′ with the Earth's equator. The orbits of the planets all lie within 3.4° of this plane, except for those of Pluto (17.2°) and Mercury (7°).