Rahu and Ketu are Lunar nodes. They are called shadow planets. They move clock wise in Zodiac Rahu Ketu stay one and half year in each sign.
Rahu Ketu first give the result of planets which aspects them , then they give the result of the planets with whom they are conjoined , then the give the result of their Star lords, and and lastly they give the result of their sign lord which they occupied. Rahu and ketu are always stronger than planets . Nodes are always stronger than planets.
-Debasish Mukherjee.Stellar Astrologer,India