Rahu, the shadow planet in Vedic Astrology, is the north lunar node in Astronomy. Lunar nodes are points that mark the intersection of the Moon’s orbit around the Earth with the ecliptic ( the apparent path of the Sun in the sky). Thus, the nodes are merely the interception of these two orbit lines and the north node is the point where the orbit of the moon crosses to the North (or ascending) of the ecliptic.
Position of Rahu is significant in both astronomy and Vedic astrology. When on a New Moon day, the Sun and Moon are in conjunction and Rahu is also in conjunction with both, a solar eclipse occurs. When the Sun and Moon are in opposition on a Full Moon day, and one of them is in conjunction with Rahu, a lunar eclipse occurs. In Vedic Astrology, Rahu represents the head of a demon (Ketu, the rest of the body) and a highly malefic planet. It stands for ignorance, illiteracy, uncultured people, thieves, witches, magicians, venom, snake, jails, cemeteries, spies, criminals and terrorists. Rahu brings unexpected losses, frustration, failures as well as can grant success, unexpected gains, win over enemies depending on its position and association in the horoscope. It is associated with breaking of laws, taboos, restrictions, be it in marriage, politics, science or creative activities. It engenders instinct based, animal behavior, craving in pleasure, fame, success and money. Indian Astrological treatises like Brihat Parashari Hora outline predictions resulting from Rahu’s presence in various rasis, houses and association with other planets. Rahu is the serpent power and is involved in Kala Sarpa yoga.
Rahu Mahadasha in Vimshottari system in Indian Astrology is eighteen years long and brings Rahu’s characteristics in full action in one’s life. Rahu Mahadasha -Saturn Antardasha is often a difficult period for all. Being a shadow planet, Rahu takes on the characteristics of the planets and rasis it is associated with.