Origin story
The Navagraha are the nine planetary deities — Surya, Chandra, Mangala, Budha, Guru, Shukra, Shani, Rahu and Ketu — whose movements are believed to shape time and destiny. Most Hindu temples set aside a shrine or a row of nine stones for them, so that their influence can be honoured and balanced.
Each graha has its own colour, gem, metal, grain and direction, and the shanti rituals use these correspondences to calm a difficult planet. In Kerala, the Navagraha shrine is a regular feature of larger temples, and devotees come on the appropriate weekday for relief from astrological affliction.
Source: Wikipedia: Navagraha — https://en.wikipedia.org/wiki/Navagraha
