ecliptic
The great circle cut in the celestial
sphere by an extension of the plane of Earth's orbit; equivalently,
the apparent annual path of the Sun against the background of the stars.
Because of 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 intersects
the celestial equator at the equinoxes.
The ecliptic poles are the two points on the celestial
sphere that lie 90° north and south of the plane of the ecliptic. The
orbits of the planets, with the exception of Pluto,
lie close to the ecliptic.
Related category
• CELESTIAL
MECHANICS
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