Ketu

Ketu (केतु, also written Ketu) is the ninth of the Navagrahas and the second of the two chāyā-grahas — the descending lunar node, paired with Rāhu as the severed body to Rāhu's severed head. Where Rāhu reaches outward toward desire and unfamiliar terrain, Ketu looks inward and backward: toward what has been accomplished, what no longer holds interest, and what the soul has already learned well enough to forget. In classical framing Ketu is the mokṣa- kāraka, the graha associated with the release of attachment, which makes him at once the most spiritual of the grahas and the least satisfying to a native still invested in worldly outcome.

Classical grounding

Parāśara addresses Ketu alongside Rāhu as the second chāyā-graha (Brihat Parāśara Horā Śāstra, adhyāya 3) and marks the same bodilessness that makes physical svarūpa description inapplicable. Classical consensus gives Ketu the qualities of Mangala applied through the shadow register — sharp, krūra, and fiery in a way that burns inward rather than outward. In the Parasari tradition Ketu is neuter-natured, tamas-pradhāna, with no ownership of a day of the week. Exaltation and debilitation assignments for Ketu are the mirror image of Rāhu's — exaltation in Vṛścika, debilitation in Vṛṣabha on the BPHS-derived reading — with the same minority-text variations. The school-dependent disagreement is treated in reading as a caution: Ketu's dignity is read through dispositor and association more than through the rāśi tables.

Significations

The primary kārakatvas of Ketu:

Mokṣa — liberation, release, the 12th-bhāva register of the puruṣārthas
Jñāna applied to prior-life work — not the active knowledge of Bṛhaspati but the already-known that surfaces as instinct
Ātmā-nivedana — self-surrender, the disposition that undoes ego
Viveka — discernment, particularly of the kind that sees through māyā
Roga — chronic and mysterious illness, especially autoimmune or vector-hard-to-isolate conditions
Piśāca — the uncanny, the liminal, what falls outside normal categories

Ketu takes on the colour and temperament of its dispositor, similarly to Rāhu but with an inward-facing slant. In Navagraha relations Ketu counts Mangala, Śukra, and Śani as friends, Surya and Chandra as enemies (Grahaṇa-yoga applies with either), and Budha and Bṛhaspati as neutrals.

Practical interpretation

A well-placed Ketu — in the 3rd, 9th, or 12th bhāva, or conjoined with a graha whose nature is *mokṣa-*compatible — inclines the native toward introspection, research, spiritual practice, or work that requires the capacity to release the ego's grip on outcome. Ketu in a well-aspected 5th can give a deep intellectual or mystical line that the native carries from childhood.

An afflicted Ketu — conjoined with malefics, in the 7th bhāva (where it can contribute to detachment from relationship that reads as difficulty), or in Grahaṇa-yoga — tends to manifest as estrangement from the worldly register, sudden losses, hard-to-diagnose physical complaints, or withdrawal that is not chosen. Ketu's disruptions are read in the tradition as vairāgya-inducing — pushing the native toward spiritual maturation by removing what was relied on.

Remedies

Classical tradition recommends the Ketu Kavaca and worship of Gaṇeśa as the adhi-devatā of Ketu, along with Bhairava in a line of practice that pairs him with Rāhu-Ketu afflictions. Vaidūrya (cat's eye) is the gemstone classically associated with Ketu. Naga-devatā observances, donations of multi-coloured cloth, sesame, and blankets, and the feeding of dogs are named in the tradition alongside Rāhu observances. None are prescribed here.

Related Concepts

Rāhu — counterpart chāyā-graha at the ascending lunar node
Kāla-sarpa-dośa — classical dośa with all grahas between Rāhu and Ketu
Grahaṇa-dośa — eclipse-register dośa involving Ketu-Rāhu affliction of luminaries
Vyaya-bhāva (12th) — 12th bhāva, register of mokṣa where Ketu's classical register operates
Aśvinī — nakshatra ruled by Ketu
Maghā — nakshatra ruled by Ketu
Mūla — nakshatra ruled by Ketu