ecliptic

ecliptic , 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 23 1/2 °. The constellations through which the ecliptic passes are the constellations of the zodiac .

ecliptic The apparent path of the Sun against the star background over the course of a year. The movement of the Sun along the ecliptic is actually a result of the Earth's movement in its orbit around the Sun. Therefore the ecliptic is actually the plane of the Earth's orbit projected on to the celestial sphere. Because of the Earth's axial tilt, the ecliptic is inclined at about 23°.4 to the celestial equator, an angle known as the obliquity of the ecliptic. The ecliptic crosses the celestial equator at the equinoxes. It takes its name from the fact that eclipses occur when the Moon is near the plane of the ecliptic.