Ketu is an imaginary planet or a node that is positioned where the earth's trajectory around the Sun and the Moon's trajectory around the Earth meet. It is believed to represent the tail of demon. Both Rahu and Ketu are the parts of the same danava (demon) but are 180 degree apart.
When Ketu, Sun and Moon lie in the same zodiacal longitude lunar eclipse takes place. Those ruled by Ketu, are secret adversaries and relates to people in pharmaceuticals industries, doctors and astrologers. Both imaginary nodes are the mysterious forces and show karmic and spiritual influences in the birth chart. Ketu also does not rule any zodiac sign since it is not a real planet.
