C/2021 O3 (PanSTARRS)
Discovered byPan-STARRS
Discovery date26 July 2021
Orbital characteristics
Number of
Orbit typeOort cloud[2]
Perihelion0.287 AU[1]
Eccentricity1.00005 (epoch 1950)[2]
1.002 (epoch 2021)[1]
1.0001 (epoch 2100)[2]
Last perihelion21 April 2022
Earth MOID0.062 AU[1]
Jupiter MOID2.16 AU
Comet total

C/2021 O3 (PanSTARRS) was an Oort cloud comet, discovered on 26 July 2021 by the Pan-STARRS sky survey. It came to perihelion on 21 April 2022 at 0.287 AU (42.9 million km). from the Sun.

The comet was expected to reach apparent magnitude 5 by late April 2022, while being only 15 degrees from the Sun.[3][4] While near perihelion the comet was dimmer than expectations. It was faintly visible in STEREO/SECCHI COR2-A on 27 April 2022.[5] Observations by Lowell Discovery Telescope on April 29 in the twilight detected a diffuse glow with a magnitude of 9 where the comet was expected to be, indicating that the comet nucleus disintergrated during perihelion.[6] C/2021 O3 made its closest approach to Earth on 8 May 2022 at a distance of 0.60 AU (90 million km).[7] As a dynamically new comet from the Oort cloud there was a high risk of disintegration.[8]


Orbit through inner Solar System
Orbit through inner Solar System

With a short observation arc of 7 days, the Minor Planet Center used an assumed eccentricity of 1.0 for the orbit solution.[9] Due to statistics of small numbers, with a short 10 day arc JPL had an eccentricity of 0.99595±0.00444 which could be as high as 1.00039 or as low as 0.99151.[10] With an observation arc of 53 days, JPL Horizons shows both an inbound and outbound eccentricity greater than 1.[2]

C/2021 O3 probably took millions of years to arrive from the outer Oort cloud and, had it survived, may have been fated to be ejected from the Solar System.[2]


  1. ^ a b c "JPL Small-Body Database Browser: C/2021 O3 (PANSTARRS)". Jet Propulsion Laboratory. Retrieved 28 September 2021.
  2. ^ a b c d e "JPL Horizons On-Line Ephemeris for 2021 O3 at epoch 1950 and 2100 (barycentric)". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 29 September 2021. Solution using the Solar System Barycenter. Ephemeris Type:Elements and Center:@0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2100. Aphelia/orbital periods defined while in the planetary-region are misleading for knowing the long-term inbound/outbound solutions.)
  3. ^ "Electronic Telegram No. 5009". Central Bureau Electronic Telegrams. 1 August 2021.
  4. ^ "C/2021 O3 ( PanSTARRS )". Seiichi Yoshida.
  5. ^ C/2021 O3 (PANSTARRS) was faintly visible
  6. ^ Zhang, Qicheng; Ye, Quanzhi; Farnham, Tony L.; Holt, Carrie E. (2 May 2022). "ATel #15358: Disintegration of Near-Sun Comet C/2021 O3 (PANSTARRS)". The Astronomer's Telegram. Retrieved 8 May 2022.
  7. ^ "Closest Approach to Earth 2022" (Closest Earth approach occurs when deldot flips from negative to positive). JPL Horizons. Retrieved 2021-09-29.
  8. ^ Machholz, Donald (5 May 2022). "EarthSky | Darn! Comet C/2021 O3 PanSTARRS has disintegrated". earthsky.org.
  9. ^ "MPEC 2021-P05 : COMET C/2021 O3 (PANSTARRS)] (7-day arc)". Minor Planet Electronic Circulars. Minor Planet Center. 1 August 2021.
  10. ^ Archive of JPL #2 (with a 10 day arc)