C/1991 L4
C/1991 L4 (Helin-Alu)
Not currently visible. Last report 12496 days ago at mag 35.4. Historic peak was mag 19.5. Typical backyard telescopes will not show it. HST, JWST, or an 8–10 m class telescope might recover it with a good ephemeris.
Right ascension
—
J2000
Declination
—
J2000
Estimated magnitude
35.4
Professional survey · COBS consensus
Confidence
33
Class E · priority 60
Observations
9
Arc unknown
Last observation
12496d ago
Fri, 21 Aug 1992 03:50:24 GMT · COBS consensus
Perihelion
1992-01-31
4.900 au
Peak window
1992-01-28 → 1992-06-24
COBS peak mag 19.5 on 1992-06-21 · perihelion 1992-01-31. Window is those dates ±3 days — not a light-curve fit.
Historic peak
19.5
COBS / analyzed peak 1992-06-21
Catalog ingest
15h ago
Venator last wrote this row 2026-11-06 14:20:21 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.
No tail measures stored yet for this object.
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
4.900 au
e
1.0000
i
49.00°
Ω
254.00°
ω
31.00°
a
—
MOID
—
H
—
H0 / n
—
NEO score
—
PHA score
—
RMS
—
Elongation
—
Reporting sources
COBS comet list
okComet Observation Database magnitudes and perihelion data for the full COBS list (active and inactive).
Name history
C/1991 L4 (Helin-Alu)
Informal: Helin-Alu
C/1991 L4 · 2026-09-14 18:27:58 UTC → current
Discoverers
Discoverer · parsed-name · 2026-09-14 18:27:58 UTC → current
Contributors
Visual Observer · MOD · 6 reports · last 12496d ago
Visual Observer · HAL · 3 reports · last 12638d ago
Pips are observation weight on this object (log of report count). Hover for catalog-wide weight.