Rahuराहु

Rahu (राहु) is the strangest member of the Navagraha: not a luminary but a disembodied head, the surviving half of an asura who tasted immortality. In astronomical terms he is the ascending node of the moon, the point where the lunar orbit crosses the ecliptic northward, one of the two positions at which eclipses occur. Hindu tradition personified the geometry as a devourer, and the eclipse as a swallowing.

The churning of the ocean

When gods and asuras churned the ocean of milk and the amrita of immortality emerged, Vishnu in the form of the enchantress Mohini distributed it to the gods alone. One asura, Svarbhanu, slipped into their line in disguise and drank. The sun and moon, who had seen through him, informed Vishnu, whose discus severed the impostor's neck, but the nectar had passed his throat: the head lived on as Rahu, the trunk and tail as Ketu. The Rigveda already knows a Svarbhanu who pierces the sun with darkness, so the eclipse-demon is among the oldest figures in the tradition.

Eclipses

Rahu's undying grievance is against his betrayers. Periodically he overtakes and swallows the sun or the moon, which escape through his open throat, and the world watches an eclipse. Eclipses are accordingly hedged with observances, fasting, bathing and the avoidance of auspicious undertakings while the devourer holds the luminary.

In astrology

As a graha, Rahu is a chhaya-graha, a shadow planet with no physical body, and his significations are correspondingly obscure: obsession, ambition, foreign lands and foreign ways, intoxication, sudden and unstable rise. He is imaged smoke-dark, often serpent-bodied, drawn by dark horses. Each day contains a rahu-kala, a period ruled by him during which new ventures are traditionally avoided. Yet astrologers allow him power as well as menace; a well-placed Rahu is credited with worldly success of the unconventional kind.