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Early warning for newly discovered comets and unconfirmed objects.

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C/2017 O1

C/2017 O1 (ASASSN1)

CometClass Ecatalogued
Unknown

Not currently visible. Last report 3155 days ago at mag 31.5. Historic peak was mag 12.0. 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

31.5

Professional survey · COBS consensus

Confidence

33

Class E · priority 60

Observations

462

Arc unknown

Last observation

3155d ago

Sun, 18 Mar 2018 23:31:12 GMT · COBS consensus

Perihelion

2017-10-16

1.500 au

Peak window

2017-10-13 → 2017-10-20

COBS peak mag 12.0 on 2017-10-17 · perihelion 2017-10-16. Window is those dates ±3 days — not a light-curve fit.

Historic peak

12.0

COBS / analyzed peak 2017-10-17

Catalog ingest

13h ago

Venator last wrote this row 2026-11-06 14:20:22 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

1.500 au

e

0.9970

i

39.90°

Ω

25.70°

ω

21.00°

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/2017 O1 (ASASSN1)

    Informal: ASASSN1

    C/2017 O1 · 2026-09-14 18:27:59 UTC → current

Discoverers

  • ASASSN1

    Discoverer · parsed-name · 2026-09-14 18:27:59 UTC → current

Contributors

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