Rahu in Vedic Astrology — Lunar Node, Mythology & Mantra
Rāhu · రాహువు · राहु
Chhaya graha · Mahadasha 18 years
Significations (karakatva)
Rahu is a chhaya graha (shadow planet) with no physical body. It signifies worldly ambition, obsession, foreign lands and foreigners, unconventional paths, illusion, technology, sudden events, poison and the maternal grandfather. It behaves like Saturn in many respects and is generally treated as a malefic, but Rahu in the third, sixth, tenth or eleventh house is traditionally said to give success and material gains. Rahu amplifies the matters of the house it occupies and tends to give the results of its dispositor and of the planets it is conjunct. Its daily period, Rahu Kalam, is one-eighth of daytime and is avoided for new beginnings.
Rahu key facts
Dignities and associations per Brihat Parashara Hora Shastra and common tradition
Sanskrit name
Rāhu
Telugu / Hindi
రాహువు · राहु
Exaltation
Vrishabha (Taurus) in most texts; some authorities give Mithuna (Gemini)
Debilitation
Vrishchika (Scorpio) in most texts; some give Dhanu (Sagittarius)
Own sign(s)
Kumbha (Aquarius) as co-lord with Saturn (some texts give Kanya)
Durga (adhidevata) and the Sarpas or serpent deities (pratyadhidevata)
Gemstone
Hessonite
Metal
Lead
Colour
Smoky
Direction
Southwest
Astronomy: the lunar nodes and eclipses
Rahu is the north (ascending) lunar node: the point where the Moon's orbit, inclined about 5.1° to the ecliptic, crosses the ecliptic going northwards. Ketu is the opposite, south node, always exactly 180° away. The nodes are not physical bodies but geometrical points, and they move backwards (westward) through the zodiac, completing a circuit in about 18.6 years, so they spend roughly 18 months in each sign. Solar and lunar eclipses can only occur when a new or full moon happens near one of the nodes, which is why ancient Indian astronomers linked eclipses with Rahu and Ketu. The Surya Siddhanta gives accurate methods for computing the nodes and predicting eclipses, and the Saros cycle of about 18 years relates to the same geometry.
Mythology
During the churning of the ocean of milk, the asura Svarbhanu disguised himself as a god and drank the nectar of immortality. The Sun and Moon recognised him and alerted Vishnu, who, in his form as Mohini, cut off his head with the Sudarshana chakra. Having tasted amrita, the asura did not die: his head became Rahu and his body Ketu. Rahu's enmity with the Sun and Moon is said to make him periodically swallow them, causing eclipses that end when they slip out of his severed throat. Rahu is depicted as a head riding a lion or as a serpent; the Sri Kalahasti and Thirunageswaram temples are known for Rahu worship.
Nakshatras ruled by Rahu
A person born with the Moon in one of these nakshatras begins life in the Rahu mahadasha of
18 years (the balance depends on how far the Moon has travelled through the nakshatra).
The beeja (seed) mantra is traditionally chanted on the graha's weekday or during its period, often
in multiples of 108. Traditional texts prescribe a total count (japa sankhya) for full propitiation; practices vary
between lineages, and guidance from a teacher is customary.
Frequently asked questions
What is Rahu astronomically?
Rahu is the Moon's north node, the point where the Moon's orbit crosses the ecliptic going north. It is a mathematical point, not a physical body, and eclipses occur near it.
How long is the Rahu mahadasha?
The Rahu mahadasha lasts eighteen years in the Vimshottari system.
Why do Rahu and Ketu always move backwards?
The lunar nodes regress (move westward) because of the gravitational pull of the Sun on the Moon's orbit, completing a full circle in about 18.6 years.
Astrological significations and remedies are traditional beliefs and are presented here for cultural and educational interest.