Rāhu is one of the nine major celestial bodies (navagraha) in Hindu texts. Unlike most of the others, Rahu is a shadow entity, one that causes eclipses and is the king of meteors. Rahu represents the ascension of the moon in its precessional orbit around the earth.Astronomically, Rahu and Ketu denote the points of intersection of the paths of the Sun and the Moon as they move on the celestial sphere. Therefore, Rahu and Ketu are respectively called the north and the south lunar nodes. The fact that eclipses occur when the Sun and the Moon are at one of these points gives rise to the understanding of swallowing of the Sun and the Moon by the snake. Rahu is responsible for causing the Eclipse of the Sun. Rahu and Ketu have an orbital cycle of 18 years. This coincides with the precessional orbit of the moon or the ~18 year rotational cycle of the lunar ascending and descending nodes on the earth's ecliptic plane. This also corresponds to a saros, a period of approximately 223 synodic months (approximately 6585.3211 days, or 18 years, 11 days, 8 hours), that can be used to predict eclipses of the Sun and Moon.
In Hindu tradition, Rahu is a severed head of an asura, that swallows the sun causing eclipses. He is depicted in art as a serpent with no body riding a chariot drawn by eight black horses.Rahu is supposed to be a mighty and naughty child of Maya, and thus is associated with dualities resulting from its mayavi (illusory) nature. It is a legendary master of deception who signifies cheaters, pleasure seekers, operators in foreign lands, drug dealers, poison dealers, insincere and immoral acts. It is the symbol of an irreligious person, an outcast, harsh speech, falsehoods, uncleanliness, abdominal ulcers, bones, and transmigration. Sudden changes in luck and fame are also linked to Rahu. Rahu is considered instrumental in strengthening one's power and converting even an enemy into a friend.