Rahu and Ketu ( Dragon Head & Dragon Tail)

Rahu and Ketu have been considered in Hindu astrology as equivalent to planets. They are not physical bodies but only mathematically calculated sensitive points having immense influence over the nativities on Earth.

Moon in its orbit, on a northerly course from south to north, crosses the ecliptic. This point of intersection is known as Rahu or Dragon’s head. 180 degrees away from this point, Moon on its southerly course, from north to south, again crosses the ecliptic. This point is known as Ketu or Dragon’s tail. Moon’s orbit is also inclined to the ecliptic (Figure) and hence on each such intersection the Sun, Earth and Moon are not in a straight line and eclipse does not occur.

Figure

As Rahu and Ketu are only sensitive points having no physical entity of their own, they are called shadowy planets or chhaya grahas. At Rahu and Ketu Moon’s latitude is zero, as Moon is on ecliptic itself. Rahu and Ketu are not stationary in space but have a mean motion of about 19 degree and 30 minutes per year, and take about 18 years and 6 months to make a revolution around the Earth. This motion of Rahu & Ketu is retrograde most of the time.