Rahu and Ketu are the mysterious shadow planets that represent the North and South nodes of the Moon. The nodes are the points of intersection of the Earths course around the Sun with the Moons course around the Earth.
Rahus influence is illusionary, dissolving and disintegrating. It is also an eccentric, creative, disruptive and revolutionary force.
Ketus influence is regarded as psychic, willful, detaching, penetrating, manipulative and catastrophic.
Together they are seen as the cause behind most psychological disorders, attraction to the dark side of life, incurable diseases, possession by negative entities and sudden negative events. These are of course some of the negative qualities.
Usually the success or failure visited on a person by Rahu or Ketu comes as a complete surprise. The energy and intensity of how the karma unfolds depends on the strength of Rahu and Ketu in a chart. On August 5th and 6th (as per Indian Almanac) are two auspicious times to remedy Rahu and Ketu afflictions.
These days are important and is referred as Naga Chaturthi and Panchami. If have Kala Sarpa Yoga, or are in a Rahu or Ketu major period or your birth star is Aswini, Mrigashrisha, Arudra, Ashlesha, Magha, Swathi, Moola and Satabhisha this is an essential time for you to remedy the malefic effects of these planets.
Mythologically, Rahu and Ketu were originally one being. Their father and mother were both created from the mind of Brahma. Lord Vishnu cut Rahu-Ketu into two halves when he discovered them guised as a God in order to steal some immortal elixir. Rahu being the head is the significator of intelligence. It is not mundane knowledge, but the higher intuitive intelligence. Whereas Rahu represents wisdom and knowledge, Ketu represents liberation which makes Rahu and Ketu the most influential hidden forces in human life. They are not easy to understand as their influences are always off-stage.
Kala Sarpa Yoga:There are several yogas associated with Rahu and Ketu. The most famous is the controversial Kala Sarpa Yoga (Snake yoga) wherein all of the planets are enclosed between Rahu and Ketu in the birth chart so that half of the chart is empty. Going clockwise around a chart, if Rahu comes first, followed by all of the planet with Ketu last, this is known as a Solar Kala Sarpa Yoga. Likewise, if when going clockwise around a chart and Ketu is first encountered, followed by all of the planets and Rahu at the end, it is called as a Lunar Kala Sarpa Yoga. A standard text says this weakens the chart. Yet many world famous leaders have had this yoga. What this yoga shows is the development of certain strengths at the expense of others. The result is the success that is achieved is lacking in some way and often does not have staying power. If you have Kala Sarpa Yoga in your chart, the house and sign where Rahu and Ketu are located have a much stronger role in your chart and life. One standard remedy is to consciously develop the area in your life where there are no planets.