Orbital node

From Freepedia

An orbital node is one of the two points where an inclined orbit crosses a plane of reference (e.g. the equator for geocentric orbits, the ecliptic for heliocentric orbits). Nodes do not exist for orbits with inclination equal to zero (equatorial orbits or ecliptic orbits).

The ascending (or north) node is where the object moves north from the southern hemisphere to the northern, the descending (or south) node is where the object moves back south. The line of nodes is the intersection of the object's orbital plane with the plane of reference, and runs between the ascending and descending nodes.

The symbol of the ascending node is ☊, the astronomical and astrological symbol for the Dragon's head (Caput draconis). The symbol of the descending node is ☋, the astronomical and astrological symbol for the Dragon's tail (Cauda draconis).

The lunar nodes are subject to lunar precession, which is the gradual shift westward because of the gravitational pull of the Sun upon the Moon. (See also: eclipse)

See also

• Lunar node – the orbital nodes of the Moon.