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(astronomy) The ecliptic, the plane of the Earth's orbit around the Sun, or by extension the orbital planes of other celestial bodies.

As seen from the orbiting Earth, the Sun appears to move with respect to the fixed stars, and the ecliptic is the yearly path the Sun follows on the celestial sphere. This process repeats itself in a cycle lasting a little over 365 days.

(astronomy) The ecliptic, the plane of the Earth's orbit around the Sun, or by extension the orbital planes of other celestial bodies.

The plane of Earth's orbit projected in all directions forms the reference plane known as the ecliptic. Here, it is shown projected outward (gray) to the celestial sphere, along with Earth's equator and polar axis (green). The plane of the ecliptic intersects the celestial sphere along a great circle (black), the same circle on which the Sun seems to move as Earth orbits it. The intersections of the ecliptic and the equator on the celestial sphere are the equinoxes (red), where the Sun seems to cross the celestial equator.

(astronomy) The ecliptic, the plane of the Earth's orbit around the Sun, or by extension the orbital planes of other celestial bodies.

Obliquity of the ecliptic for 20,000 years, from Laskar (1986). Note that the obliquity varies only from 24.2° to 22.5° during this time. The red point represents the year 2000.