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Early warning for newly discovered comets and unconfirmed objects.

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C/2015 X4

C/2015 X4 (Elenin)

CometClass Ecatalogued
Unknown

Not currently visible. Last report 3877 days ago at mag 29.5. Historic peak was mag 17.2. 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

29.5

Professional survey · COBS consensus

Confidence

33

Class E · priority 60

Observations

9

Arc unknown

Last observation

3877d ago

Thu, 04 Feb 2016 21:21:35 GMT · COBS consensus

Perihelion

2015-11-07

3.380 au

Peak window

2015-11-04 → 2015-12-15

COBS peak mag 17.2 on 2015-12-12 · perihelion 2015-11-07. Window is those dates ±3 days — not a light-curve fit.

Historic peak

17.2

COBS / analyzed peak 2015-12-12

Catalog ingest

15h 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

3.380 au

e

0.8120

i

29.60°

Ω

262.00°

ω

176.00°

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/2015 X4 (Elenin)

    Informal: Elenin

    C/2015 X4 · 2026-09-14 18:27:57 UTC → current

Discoverers

  • Elenin

    Discoverer · parsed-name · 2026-09-14 18:27:57 UTC → current

Contributors

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