Ketuकेतु

Ketu (केतु) is the counterpart of Rahu: when Vishnu's discus severed the asura Svarbhanu, who had stolen a taste of the nectar of immortality, the deathless head became Rahu and the trunk and tail became Ketu. Astronomically he is the descending node of the moon, the southern crossing-point of the lunar orbit where eclipses may occur; in the Navagraha he completes the pair of shadow planets that hold the last two places among the nine.

The headless one

Ketu is imagined as a body without a head, usually with a serpent's tail, sometimes crowned with a flame or gem where the head should be. His name means banner, sign or comet, and in Sanskrit astronomy comets themselves were called ketus, portent-lights trailing across the sky. The iconography suits his meaning: a figure without a head is a figure without ego, appetite or calculation, and Ketu's significations run precisely opposite to worldly attachment.

In astrology

Where Rahu inflates desire, Ketu withdraws it. He is the karaka of mokṣa, liberation, and of the losses, severances and reversals that turn a life inward. Tradition associates him with intuition, hidden and occult knowledge, past-life residue and sudden flashes of insight, as well as with wounds and afflictions when badly placed. His periods are held to strip away what is inessential, painfully for the worldly, fruitfully for the spiritually inclined. Remedial worship of Ganesha, and offerings on his behalf, are the customary responses to his harder transits. Among the nine grahas he is the renunciate, the planet whose gift is subtraction.