धूमकेतु · शिखिन् · केतुचार
Everything else in this series obeys. The stars keep station, the frame drifts on schedule, the eclipse follows the nodes, even the wanderers' backward loops fit an eightfold taxonomy. The comet obeys nothing. It arrives unannounced, wears a smoking banner, crosses where it pleases, and leaves. This essay follows the Sanskrit comet — dhūmaketu, 'the smoke-bannered', śikhin, 'the crested' — through its whole biography: a fire-god's epithet, Death's flag, a war omen, and finally the most epistemically honest chapter in the omen literature, which opens by admitting that no computation can find a comet, and then tells you exactly what to record anyway.
Every quote is a slice from Jñānakośa, the research database behind this atlas; each links to its revision-pinned source page. Translations are literal renderings; dates are approximate spans of compilation. Display markup of the e-texts is removed here; the full text, apparatus and confidence grades are one click away.
अग्नि · the word's first owner
Ketu means banner, beacon — the thing raised so a host can be seen from afar. And dhūmaketu, 'he whose banner is smoke', belongs first to Agni: here in the Atharvaveda's funeral hymn, it is the fire itself, carrying the offering skyward under its flag of smoke:
A comet is a fire where no fire should be, trailing its own banner — when the sky grew one, the fire-god's flag was the word waiting for it.
मृत्यु · the flag changes hands
By the Atharvaveda's peace litanies the flag has changed hands. In one verse the roster of things needing pacification runs: the grahas of the moon, the sun together with Rāhu — the whole eclipse doctrine of the third essay in four words — and then mṛtyur dhūmaketuḥ: Death, the smoke-bannered. The comet's ill name is already fixed, and it files beside the sharp-flamed Rudras:
पुष्य · in the war catalogue
In the Bhīṣma-parva's omen catalogue — five verses before Mars's retrograde loop — the comet is treated, for the length of an omen, exactly like a planet: a position among the nakṣatras, a verb of standing, and the rank of mahāgraha, 'great seizer':
The omen register never needed an ephemeris — only a sighting and a star-name. That is precisely the gap the next text will make explicit.
See: the same catalogue's Mars loop, in essay six
न गणितविधिना · the honest chapter
Varāhamihira's ketu-cāra chapter is the most epistemically self-aware opening in the omen corpus. First, source criticism: Garga's comet-course — the same Vṛddha-Garga tradition this database tracks as a lost source — with Parāśara and Asita-Devala, collated into an 'untangled' account. Then the sentence that separates comets from everything else in this essay series: their appearance and setting cannot be known by computation. From the man who computes eclipses to the digit. Then a classification that begins by excluding the known glows — fireflies, ghost-haunts, the shine of gems — so the class stays clean; and an honest record of disagreement about how many ketus there are: a hundred and one, a thousand — or the sage Nārada's minority report, one only, of many forms:
No siddhānta in the database has a comet chapter. This verse is why: the computing tradition drew its own boundary, and the comet stayed outside it.
किमनेन · drop the ontology
And then the pivot that makes the chapter science rather than surrender. One ketu or a thousand — kim anena, 'what use is that?' Judge by the observables: risings and settings, stations, which asterisms it touches, how smoky, what colour. And record the duration, because the effect scales with it — a day of visibility ripens as a month of consequence:
Strip the omen frame and this is a comet log: date of appearance, date of last visibility, track, tail, colour, duration. The protocol survived inside the prognosis.
स्थानात्स्थानान्तरम् · the late register
The late omen compendia keep watching. In the Bhaviṣya-purāṇa's book of portents the trigger is the comet's motion — blazing like kindled fire, it 'goes from one station to another' across the nakṣatra frame, or falls to earth; comet and meteorite still one smoking class, as they were in Varāhamihira's threefold division:
One housekeeping note the texts themselves force: this essay's ketu — the crested visitor — is not the Ketu of the sixth essay's navagraha roster. That Ketu is the eclipse-demon's trunk, the moon's descending node, perfectly periodic and eventually computed; he earned a chair at the fire precisely by being predictable. The smoke-bannered one never did. The tradition's treatment of the two is its epistemics in miniature: what repeats gets a model and a seat; what does not gets a boundary-statement, an exclusion list, a count honestly disputed, and a protocol — watch it rise, watch it set, note the station, the smoke, the colour, the days. That is what you do with a phenomenon that will not be computed: you write down everything, and you say so.
Each quote carries its full citation, edition, revision-pinned source link and confidence grading in Jñānakośa — batch ketu-comet-pass1 (which opened the Bhaviṣya-purāṇa as a source) with the standing passes. The next great comet will arrive, as always, unannounced; when it does, the log the Bṛhat-saṃhitā asks for — station, smoke, colour, days — is still exactly the log to keep.