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The plane of the Earth's orbit projected in all directions forms the reference plane known as the ecliptic[1]

From a geocentric point of view, it's the path travelled by the Sun on its apparent path around the Earth.
It is actually the Earth's orbit projected onto the celestial sphere.

In astrology, the ecliptic is divided into twelve equal segments of 30 degrees. These are the twelve signs of the zodiac.
Although the signs of the zodiac were named after the star constellations found along the ecliptic, they are not identical to them.

Because the Earth is tilted, the ecliptic currently forms an angle of approximately 23 degrees, 26 minutes to the celestial sphere. The precise values are 23°27'5" in the year 1900, 23°26'16" in 2000, 23°25'43" in 2100. This is called the axial tilt or obliquity.

See also


Notes and References

  1. The intersections of the ecliptic and the equator on the celestial sphere are the vernal and autumnal equinoxes (red), where the Sun seems to cross the celestial equator