Dhanu is the ninth rashi, the Vedic sign of the bow or archer, corresponding to Sagittarius. In jyotisha it is ruled by Jupiter (Guru), the great benefic and teacher. Its quality is dual or mutable (dvisvabhava), and its element is fire (agni tattva). Jyotisha reads Dhanu through Jupiter's expansiveness and the archer's aim: philosophy, dharma, higher learning, aspiration, and the arrow loosed toward a distant goal. As a sidereal sign it is fixed to the stars and sits roughly 24 degrees behind tropical Sagittarius, in the direction of the galactic centre. Jupiter's rulership of the archer is shared with Western astrology. In a Vedic chart Jupiter's condition and the ninth house, both tied to dharma and fortune, give Dhanu particular weight for questions of belief and guidance.
Dhanu names the bow itself, the weapon, rather than the archer who draws it, a narrower sense than the Greek toxotes it renders, which means archer outright; the transmission runs through the Yavanajataka, a versification of a Greek astrological text of roughly the second through fourth centuries CE, built on the twelve equal signs Babylonian celestial divination had already fixed by the fifth or fourth century BCE, a scheme with no precedent in the older Vedic corpus. Jupiter's rulership of Dhanu, shared with the equivalent tropical Sagittarius, belongs to a later classical layer of the tradition, standardly credited to compilations such as the Brihat Parashara Hora Shastra of roughly the seventh or eighth century CE, whose ascription to the sage Parashara is a later, pseudepigraphic attribution rather than the record of one historical author.
Sources Brihat Parashara Hora ShastraSage Parashara (attributed) with The Yavanajataka of SphujidhvajaDavid Pingree, Jyotihsastra: Astral and Mathematical LiteratureDavid Pingree