Ecliptic

• The Ecliptic is the path of the Sun in the Sky, a line along which the Sun always travels during the Year.
• The Moon and the visible Planets nearly all follow a line close to the Ecliptic.

Celestial Equator

• They both form discs which intersect each other twice a year, known as the Vernal Equinox and the Autumnal Equinox.
• The angle between the discs is 24.4° known as the Obliquity of the Ecliptic.

Obliquity of the Ecliptic

• The Obliquity of the Ecliptic means the Tilt of the Earth or Tilt axis from vertical axis which is 24.4°.

The Invariable Plane of the Solar System

• The Moon and the visible Planets nearly all follow a line close to the Ecliptic and this is known as the Invariable Plane of the Solar System.