Rahu and Kethu are the two most critical astronomical bodies in Hindu mythology. As per science, they are both shadow planets with an orbital cycle of 18 years. And both are always at 180 degrees from each other orbitally. It coincides with processional moon orbit or the 18-year rotational cycle. In Hindu texts, it is also similar to Rahu and Kethu being two parts of an Asura or an evil creature. If the head of the Asura is on the north lunar node, the body of the Asura is 180 degrees at the south of the lunar node. Since Rahu and Kethu denotes the intersection paths of the Sun and Moon along with the movement of the moon on the celestial sphere, they are called north and south lunar nodes.