The early period temples of the 6th-7th century CE in Odisha are adorned with the images of ashta-grahas (eight planets) instead of the regular nava-grahas (nine planets) group. The Shatrughnesvara group and the Parasurameshvara temple in Bhubaneswar have the doorway lintel block decorated with the images of the ashta-grahas comprising Aditya (Surya), Soma (Chandra), Angaraka (Mangal), Budha, Brhaspati, Shukra, Shanicchhar (Shani) and Rahu. Ketu is excluded from this group. The later period temples in Odisha have the depiction of the regular nava-graha group with all its members. This indicates an earlier tradition of a fewer number of grahas before the nava-graha group was crystallised. These early graha panels of Odisha are inscribed, indicating it was initial experimentation and the labels were to help the common public understand the names of the grahas.
To find answers to the evolution of the grahas, we need to dig into the annals of ancient Indian astrology and astronomy. While there is no definitive reference to grahas in the Rigveda, there is a mention of a demon Svarbhanu piercing Surya with darkness and the latter being restored by Atri. Atharvaveda, without giving names, mentions grahas as wanderers in heaven. It also mentions Rahu as a seizer of Chandra. One of the earliest available astrological treatises is probably the Parasara-tantra, which has not survived in full but is only being referred to in various later commentaries. It mentions five planets Mangal, Budha, Brhaspati, Shukra and Shani, who with Surya and Chandra (Soma), constitute a group of seven celestial bodies. Parasara-tantra also includes Rahu as a planet; however it mentions it as an invisible body responsible for eclipses. Ketus are mentioned in plural, in the context of comets.
Yavanajataka of Sphujidhvaja, dated between 4th and 6th century CE, is a Sanskrit translation of a Greek text. It is an important astrological work as it reflects the intermingling of Indian and Hellenistic (Greek) ideas and the exchange of information. In the Yavanajataka, the seven planetary deities are mentioned as Surya, Chandra, Shukra, Brhaspati Budha, Angaraka and Shanaichchara. These names match very well with the label inscriptions of Odisha. The seven planets of Yavanajataka appear to be influenced by the seven planets of Hellenistic astrology, Sun, Moon, Venus, Jupiter, Mercury, Mars and Saturn, as both follow the same sequence.
Brihat-Samhita of Varahamihira, dated to 6th century CE, is a very important work in ancient Indian astrology and astronomy and considered a landmark as he collected all the available information from past authors and provided a compendium. Varahamihira questions the validity of Rahu as a planet. He quotes a tradition of Rahu turning into a planet though his head was cut off as he tasted the divine nectar. His head resembles the orbs of other planets; however he is not visible in the sky being of dark colour except during eclipses. He mentions that authors before him have declared Rahu as having a serpentine form with a head and tail alone, and a few have said he is formless and of pure darkness. Varahamihira questions: If Rahu has a circular body with head and tail and has affixed and uniform motion, then how can he seize the Sun and Moon, as these both are located at 180° to each other during eclipse time? Or if Rahu does not have a fixed motion, then how can his position be determined by calculation? Or if this Rahu has a big body such that by his mouth he seizes the Moon and by the tail, the Sun, why does he not obstruct half of the zodiac falling between his head and tail? Or if there are two Rahus, then when one is seizing the Sun, the other should seize the Moon, but that is not practical. Like Parasara, Varahamihira also treats Ketu as comets but not as a planet.
In his Brihajjatakam, Varahamihira includes Ketu under planets. However, he did not provide as many details as he did for other planets. His use of the synonym Shikhin for Ketu suggests that Ketu was still treated as comets. In the Puranas, treatment on the numbers of grahas is different at different places, sometimes eight and sometimes nine.
The earliest sculptural representation of grahas in Indian art is over the Yajna-Varaha figure at Eran (Madhya Pradesh), dated to 5th century CE. On the chest of the Varaha are carved seven standing figures representing seven planets. Surya, first in the group, is wearing a tunic dress and holding a lotus in both hands. This depiction of seven planets connects to the Hellenistic tradition of seven planets corresponding to the seven days of a week. While we do not find grahas on the surviving Gupta temples, there are a few Gupta period sculptures, one in the Indian Museum, Kolkata, and another in the Worcester Art Museum, depicting eight grahas excluding Ketu. Many ashta-grha panels are also reported from Bihar. Probably, after the 7th century CE, Ketu started getting included among the grahas as evident by the depiction of the nava-graha group in Indian temple art across geography as well as the inclusion of Ketu as a graha in the Puranic literature.
Saurabh Saxena
Founder of Puratattva, a documentation of heritage sites