Ketu is not a physical or celestial entity, but the south node of the two nodes formed when earth’s trajectory around Sun intersects moon’s trajectory around earth. It is a malefic planet, and is always 180 degrees apart from that of Rahu. Ketu and Rahu both are retrograde in motion. Ketu also causes lunar eclipse when Moon, earth and sun aligns in the same longitude along with the node. Ketu is somewhat similar to Mars in nature. It is a shadow planet as it is invisible and is just a point in the cosmic arrangement.

Legend of Ketu
According to Hindu mythology, Ketu is the rest of the body of Rahu, while Rahu is the head. When Lord Vishnu extracted the nectar of immortality by churning the sea, and decided to give it to the Gods, Rahu (a demon) took the juice and drank in disguise. Rahu was seated between Lord Suryaand Lord Chandra and they revealed the truth about Rahu’s identity. Lord Vishnu immediately cut the head of Rahu. Since the nectar had reached Rahu’s neck, it survived the ordeal but the rest of the body was burnt. The body was revived again and named as Ketu. Ever since then, Rahu and Ketu are hell bent on taking revenge from Sun and Moon by causing Solar and Lunar eclipse.

Nature of Individual with Ketu as Ruling Planet
Ketu is known as "Moksha- Karaka" or the planet influencing spirituality. The person influenced by the planet is usually endowed with psychic powers, healing abilities, excellence in herb logy, tantric and ghost related ailments. Ketu influences pharmaceutical industry, medicine and astrology to a large extent. Ketu, if favourable, brings a lot of luxury, wisdom and intuition to the person. If unfavourable, it causes weak eyesight, poor concentration, boundless worries and anxiety.

Effects of Ketu
The effect of Ketu on a person’s life is very crucial as Ketu rules some important aspects of the horoscope. Ketu does not rule any zodiac, as it is not a real planet. As oppose to Rahu's tendency to affect the mind, Ketu inflicts the body. It can cause many types of ailments right from leprosy and cancer to paralysis. Poor blood circulation, Anaemia, pains in joints and nerves are other reaction of this planet. Under common misconception, Ketu is a dreaded planet, bringing with itself disease, sufferings and dark worlds. But Ketu endows one with supreme form of spiritual enlightenment, which in itself is the greatest boon for human existence.

• Colour for Ketu: Smoke.
• Day for Ketu: Saturday.
• Gemstone for Ketu: Cat’s Eye.
• God/Deity for Ketu: Lord Bhairava.

It drives people towards spiritualism, enlightenment, asceticism and it frees the person from the shackles of worldly desires.

Mantra for Ketu
"Palasa-puspa-sankasam taraka-graha-mastakam raudram raudratmakam ghoram tam ketum pranamamy aham".

The above mentioned Mantra for Ketu means; "I offer my obeisance to the violent and fearsome Ketu, who is endowed with the potency of Lord Shiva. Resembling in his complexion the flower of a Palasa plant, he serves as the head of the stars and planets".

Importance of Ketu in Indian Astrology
Ketu in Indian Astrology concerns itself with after life experiences, spiritual knowledge, detachment from the world, the concept of righteousness and karma. It is said that Rahu is the giver and Ketu is the taker. Rahu makes a person indulgent, stuck in materialism and worldly comforts while Ketu helps to get detached from hollow endeavours. It directs a person towards liberation. Rahu is about enjoyment and worldly comforts while Ketu is about enlightenment and wisdom.