The planets of our solar system revolve around the sun, tracing imaginary lines are called orbits. These orbits are not perfectly round but are ellipses. Geometrically, the sun is not at the “center” of the system, but one of the foci of the ellipse. The elliptical plane that contains these orbits is the ecliptic plane.

Basically, the earth is used as the reference point for observing the heavenly bodies. It is assumed that outer space is like a spherical blanket that covers the earth, which is called the celestial sphere. The celestial sphere is like a map of the “almost fixed” stars. Now, we set the ecliptic plane to be mean orbit of the earth as it revolves around the sun. The intersection between this plane and the celestial sphere is called the ecliptic. It is named as such because of the root word “eclipse”. Solar eclipses only happen if the moon is very near to the sun’s path.

The sun apparently travels across the heavens by following this path, crossing twelve different constellations. These are the Zodiac signs, which are very important for astrologers. Astronomers, on the other hand, use the ecliptic as part of the celestial coordinate system. They have assigned locations for the stars and other heavenly bodies.

Ecliptic, further explained