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Early warning for newly discovered comets and unconfirmed objects.

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100P

100P/Hartley

CometClass Ecatalogued
Unknown

Not currently visible. Last report 1495 days ago at mag 25.3. Historic peak was mag 16.8. 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

25.3

Professional survey · COBS consensus

Confidence

33

Class E · priority 60

Observations

46

Arc unknown

Last observation

1495d ago

Sat, 13 Aug 2022 17:48:00 GMT · COBS consensus

Perihelion

2028-12-15

2.020 au

Peak window

2022-07-01 → 2028-12-18

COBS peak mag 16.8 on 2022-07-04 · perihelion 2028-12-15. Window is those dates ±3 days — not a light-curve fit.

Historic peak

16.8

COBS / analyzed peak 2022-07-04

Catalog ingest

10h ago

Venator last wrote this row 2026-09-16 13:20:15 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

2.020 au

e

0.4120

i

25.60°

Ω

37.70°

ω

182.00°

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

  • 100P/Hartley

    100P · 2026-09-14 18:27:52 UTC → current

Discoverers

  • Hartley

    Discoverer · parsed-name · 2026-09-14 18:27:52 UTC → current

Contributors

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