ecliptic

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ecliptic

(ēklĭp`tĭk, ĭ–), the great circle on the celestial spherecelestial sphere,
imaginary sphere of infinite radius with the earth at its center. It is used for describing the positions and motions of stars and other objects. For these purposes, any astronomical object can be thought of as being located at the point where the line of sight
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 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 systemecliptic coordinate system,
an astronomical coordinate system in which the principal coordinate axis is the ecliptic, the apparent path of the sun through the heavens. The ecliptic poles are the two points at which a line perpendicular to the plane of the ecliptic through the
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. The two points at which the ecliptic crosses the celestial equator are the equinoxesequinox
, either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. The vernal equinox, also known as "the first point of Aries," is the point at which the sun appears to cross the celestial equator from south to north.
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. 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 23 1-2°. The constellations through which the ecliptic passes are the constellations of the zodiaczodiac
[Gr. zoion=animal], in astronomy, zone of the sky that includes about 8° on either side of the ecliptic. The apparent paths of the sun, the moon, and the major planets all fall within this zone.
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.

ecliptic

(i-klip -tik) The mean plane of the Earth's orbit around the Sun. Although the orbital plane is in fact defined by the motion of the center of mass of the Earth–Moon system around the sun, the ecliptic refers to the Earth alone, the resulting errors being negligible. The ecliptic may thus be taken as coincident with the Sun's apparent annual path across the sky. The orbits of the Moon and planets, apart from Pluto, lie very near the ecliptic.

The planes of the ecliptic and celestial equator are inclined at an angle equal to the tilt of the Earth's axis. This angle, known as the obliquity of the ecliptic, is about 23°26′. The equinoxes lie on the celestial sphere at the two points of intersection of ecliptic and celestial equator. The poles of the ecliptic lie at 90° from all points on the ecliptic at the positions RA 18h, dec +66°.5 and RA 6h, dec –66°.5.

Enlarge picture
Alchemical imagery from a book by German chemist Libavius Alchymia, c. 1606, depicting a black crow sitting on an eclipse while the black face above the three-headed bird represents a total lunar eclipse. Reproduced by permission of Fortean Picture Library.

Ecliptic (Via Solis, the Sun’s Path)

(religion, spiritualism, and occult)

The ecliptic is the orbit of Earth as viewed from the Sun. For most astrological purposes, however, the ecliptic is taken to be the orbit that the Sun appears to describe around the Earth (the via solis, or the Sun’s path). The via solis acquired the name ecliptic because it is along its path, at the points where it intersects the celestial equator (the equator of the Earth projected outward onto the background of the celestial sphere) that eclipses occur. Owing to the tilt of the Earth on its axis, the ecliptic intersects the celestial equator at an angle of 23½°. The 12 signs of the zodiac, through which the Sun appears to pass over the course of a year, lie around the outside of the ecliptic.

Ecliptic

 

the great circle on the celestial sphere along which occurs the apparent annual motion of the sun or—more precisely—the apparent annual motion of the center of the sun. Since the apparent annual motion of the sun reflects the actual motion of the earth about the sun, the ecliptic may be regarded as the intersection of the celestial sphere and the plane of the earth’s orbit.

The plane of the ecliptic is inclined to the plane of the celestial equator by an angle of ε = 23° 27’ 8″.26 – 0.4685t, where t is the number of years that have elapsed since the beginning of 1900. The equation is valid for several centuries after the 20th century. The angle of inclination, which is called the obliquity of the ecliptic, varies periodically over hundreds of thousands of years.

The term “ecliptic” is associated with the fact, known since ancient times, that solar and lunar eclipses occur only when the moon is near one of the points where its orbit intersects the ecliptic. These points on the celestial sphere are called the lunar nodes. The ecliptic passes through 12 constellations, which are known as the zodiacal constellations. The plane of the ecliptic is the fundamental plane in the ecliptic system of celestial coordinates.

ecliptic

[i′klip·tik]
(astronomy)
The apparent annual path of the sun among the stars; the intersection of the plane of the earth's orbit with the celestial sphere.
The plane of the earth's orbit around the sun.

ecliptic

ecliptic
ecliptic
The apparent annual path of the sun among the stars during a year. Strictly, it is the projection of the plane of the earth's orbit on the celestial sphere. It is a great circle inclined at about 23°27′ to the celestial equator. It cuts the equator at two points called the equinoxes. The point where the sun cuts the equator on its path from south to north is known as the first point of Aries, and the path from north to south is called the first point of Libra.

ecliptic

1. Astronomy
a. the great circle on the celestial sphere representing the apparent annual path of the sun relative to the stars. It is inclined at 23.45? to the celestial equator. The poles of the ecliptic lie on the celestial sphere due north and south of the plane of the ecliptic
b. (as modifier): the ecliptic plane
2. an equivalent great circle, opposite points of which pass through the Tropics of Cancer and Capricorn, on the terrestrial globe
3. of or relating to an eclipse
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