Rāhu

Rāhu (राहु, also written Rahu) is the eighth of the Navagrahas and the first of the two chāyā-grahas — shadow grahas, not physical bodies but the ascending lunar node computed as a mathematical point on the ecliptic. The myth reported in the Bhāgavata Purāṇa and the Mahābhārata names Svarbhānu as the asura who stole a sip of amṛta during the churning of the ocean and was cut in two by Viṣṇu's discus; the head became Rāhu, the body Ketu. Both pieces were granted graha status in the classical scheme. Because Rāhu has no physical body, Parāśara's svarūpa descriptions of the seven primary grahas do not apply — Rāhu is read through its effects and its dispositor rather than through a body of its own.

Classical grounding

Parāśara addresses the chāyā-grahas in Brihat Parāśara Horā Śāstra adhyāya 3 among the other grahas but marks the distinction of bodilessness. Classical consensus gives Rāhu the qualities of Śani applied through the shadow register — Rāhu's effects run adjacent to Śani's but are amplified, unpredictable, and oriented toward desire rather than patience. In the Parasari tradition Rāhu is male, tamas-pradhāna, and has no rulership of a day of the week in the same way the seven grahas do. Rāhu is commonly given exaltation in Vṛṣabha and debilitation in Vṛścika in the BPHS-derived consensus, though some later sources — including certain readings of Phaladeepikā — assign exaltation to Mithuna. What all classical sources agree on is that Rāhu has no mūlatrikoṇa or own sign in the standard rāśi scheme.

Significations

The primary kārakatvas of Rāhu:

Kāma — desire, especially in its amplifying, boundary-crossing register
Māyā — illusion, confusion, the veil between appearance and thing
Videśa — foreign lands, foreignness as such, unfamiliar terrain
Vidyut — electricity and, in contemporary extensions, technology mediated through it
Viṣa — poison, including metaphorical toxicity in thought or relation
Ati-tvarā — sudden, compressed, unexpected eventfulness

Rāhu takes on the colour of its dispositor and its sign lord — classical readings depend heavily on which sign Rāhu occupies and who owns that sign. In Navagraha relations Rāhu counts Budha, Śukra, and Śani as friends, Surya and Chandra as enemies (Grahaṇa-yoga with either is the eclipse combination), and Mangala as neutral.

Practical interpretation

A well-placed Rāhu — in a kendra or trikona, or in the 3rd, 6th, 10th, or 11th bhāva (the four classical upacaya houses where Rāhu reliably does well), with supportive aspects — inclines the native toward ambition, unusual career paths, international reach, or success in fields mediated by novelty or technology.

An afflicted Rāhu — in Grahaṇa-yoga with Surya or Chandra, or Guru-Cāṇḍāla-yoga with Bṛhaspati — tends to manifest as disoriented judgement, compulsive pursuits, chronic dissatisfaction with achievement, or psychological instability in the faculty the conjoined graha governs. Rāhu in the 1st, 5th, 7th, or 9th is examined carefully in the tradition because those are bhāvas of identity, wisdom, relationship, and dharma where Rāhu's shadow can occlude clarity.

Remedies

Classical tradition recommends the Rāhu Kavaca and worship of Bhairava or Durgā as appropriate adhi-devatās for Rāhu, with Sarpa-related observances (serpent worship being classically tied to Rāhu as Bhujaṅga) named in the śāstra. Gomeda (hessonite) is the gemstone classically associated with Rāhu. The Rāhu Kavaca, Nāga-pañcamī vratas, donations of dark blankets, sesame, and copper, and feeding black dogs are named in the tradition. None are prescribed here.

Related Concepts

Ketu — counterpart chāyā-graha at the descending lunar node
Kāla-sarpa-dośa — classical dośa with all grahas between Rāhu and Ketu
Grahaṇa-dośa — eclipse-register dośa involving Rāhu-Ketu affliction of luminaries
Pitṛ-dośa — ancestral-register dośa cross-referenced via Rāhu configurations
Ārdrā — nakshatra ruled by Rāhu
Svātī — nakshatra ruled by Rāhu
Śatabhiṣā — nakshatra ruled by Rāhu