C/2017 K4
C/2017 K4 (ATLAS)
Not currently visible. Last report 2821 days ago at mag 29.3. Historic peak was mag 16.7. 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
29.3
Professional survey · COBS consensus
Confidence
33
Class E · priority 60
Observations
16
Arc unknown
Last observation
2821d ago
Wed, 26 Dec 2018 20:09:35 GMT · COBS consensus
Perihelion
2018-01-03
2.680 au
Peak window
2017-08-16 → 2018-01-06
COBS peak mag 16.7 on 2017-08-19 · perihelion 2018-01-03. Window is those dates ±3 days — not a light-curve fit.
Historic peak
16.7
COBS / analyzed peak 2017-08-19
Catalog ingest
11h ago
Venator last wrote this row 2026-09-16 13:20:18 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
2.680 au
e
0.9060
i
16.60°
Ω
299.00°
ω
15.30°
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/2017 K4 (ATLAS)
Informal: ATLAS
C/2017 K4 · 2026-09-14 18:27:59 UTC → current
Discoverers
Discoverer · parsed-name · 2026-09-14 18:27:59 UTC → current
Contributors
CCD Observer · HIL04 · 14 reports · last 2821d ago
CCD Observer · NAG05 · 2 reports · last 3347d ago
Pips are observation weight on this object (log of report count). Hover for catalog-wide weight.