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Early warning for newly discovered comets and unconfirmed objects.

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C/1999 S4

C/1999 S4 (LINEAR)

CometClass Ecatalogued
Unknown

Not currently visible. Last report 9514 days ago at mag 34.3. Historic peak was mag 5.8. Typical backyard telescopes will not show it. HST, JWST, or an 8–10 m class telescope might recover it with a good ephemeris.

Active comet in COBS

JSONCSV

Right ascension

—

J2000

Declination

—

J2000

Estimated magnitude

34.3

Professional survey · COBS consensus

Confidence

33

Class E · priority 60

Observations

915

Arc unknown

Last observation

9514d ago

Wed, 30 Aug 2000 10:19:11 GMT · COBS consensus

Perihelion

2000-08-01

0.753 au

Peak window

2000-07-25 → 2000-08-04

COBS peak mag 5.8 on 2000-07-28 · perihelion 2000-08-01. Window is those dates ±3 days — not a light-curve fit.

Historic peak

5.8

COBS / analyzed peak 2000-07-28

Catalog ingest

11h ago

Venator last wrote this row 2026-09-16 13:20:16 UTC

Light curve

Brightness over time (V mag)

Gold = reported observations. Steel dashed family = ensemble (nominal / outburst / fade / disruption).

Tail length

Converted to degrees from COBS (d / arcmin / arcsec). Empty until analysis has pulled the archive.

Ensemble is a first-pass H0/n photometric model plus observed samples — not a trained ML forecast yet. The background analyzer walks the catalog one object at a time so COBS is not flooded. Disruption track rises after perihelion to stand in for solar-wind stripping.

Orbital elements

q

0.753 au

e

0.9990

i

149.00°

Ω

83.80°

ω

152.00°

a

—

MOID

—

H

—

H0 / n

—

NEO score

—

PHA score

—

RMS

—

Elongation

—

Reporting sources

  • COBS comet list

    ok

    Comet Observation Database magnitudes and perihelion data for the full COBS list (active and inactive).

Name history

  • C/1999 S4 (LINEAR)

    Informal: LINEAR

    C/1999 S4 · 2026-09-14 18:27:54 UTC → current

Discoverers

  • LINEAR

    Discoverer · parsed-name · 2026-09-14 18:27:54 UTC → current

Contributors

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Pips are observation weight on this object (log of report count). Hover for catalog-wide weight.