C/2021 O3 (PanSTARRS)
| Discovery[1] | |
|---|---|
| Discovered by | Robert Weryk |
| Discovery site | Pan-STARRS |
| Discovery date | 26 July 2021 |
| Orbital characteristics[2][3] | |
| Epoch | 30 October 2021 (JD 2459517.5) |
| Observation arc | 351 days |
| Number of observations | 760 |
| Orbit type | Oort cloud |
| Perihelion | 0.287 AU |
| Eccentricity | 1.00015 |
| Inclination | 56.75° |
| 189.03° | |
| Argument of periapsis | 299.98° |
| Mean anomaly | –0.002° |
| Last perihelion | 21 April 2022 |
| TJupiter | 0.446 |
| Earth MOID | 0.063 AU |
| Jupiter MOID | 2.165 AU |
| Physical characteristics[5] | |
Mean radius | ~1.0–1.7 km (0.62–1.06 mi) |
| 0.04 (assumed) | |
| Comet total magnitude (M1) | 10.6 |
| 7.6 (2022 apparition)[4] | |
C/2021 O3 (PanSTARRS) is a hyperbolic 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.
Observational history
The comet was expected to reach apparent magnitude 5.0 by late April 2022, while being only 15 degrees from the Sun.[1][6] While near perihelion the comet was dimmer than expectations, only reaching magnitude 7.6 at its peak brightness on 19 April 2022.[4] It was faintly visible in STEREO/SECCHI COR2-A on 27 April 2022.[7] Observations by Lowell Discovery Telescope on 29 April in the twilight detected a diffuse glow with a magnitude of 9.0 where the comet was expected to be, indicating that its nucleus disintegrated during perihelion,[8] however follow-up studies in 2025 revealed that this is unlikely and the comet remains intact post-perihelion.[5] C/2021 O3 made its closest approach to Earth on 8 May 2022 at a distance of 0.60 AU (90 million km).[9]
The comet was recovered by multiple observatories after perihelion at magnitudes not too different from those observed pre-perihelion.[10] Calculations carried out using the pre- and post-perihelion orbits indicate that although the comet is probably dynamically old, it may also be a fragment of a dynamically new comet that was released during the first perihelion passage of its parent comet.[10][11]
Orbit
With a short observation arc of 7 days, the Minor Planet Center used an assumed eccentricity of 1.0 for the orbit solution.[12] 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.[13] With an observation arc of 53 days, JPL Horizons shows both an inbound and outbound eccentricity greater than 1.[2]
C/2021 O3 likely 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] This is also the most likely scenario when considering the post-perihelion orbit determination of the surviving object.[10]
References
- ^ a b R. Weryk (1 August 2021). D. W. Green (ed.). "Comet C/2021 O3 (PanSTARRS)". Central Bureau Electronic Telegrams (5009).
- ^ a b c "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.)
- ^ "C/2021 O3 (PanSTARRS) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 28 September 2021.
- ^ a b "Observation list for C/2021 O3". COBS – Comet OBServation database. Retrieved 10 June 2025.
- ^ a b D. C. Jewitt; J. Li; M. Jaeger; Y. Kim (2025). "Down But Not Out: The Case of Long-Period Comet C/2021 O3 (PanSTARRS)". arXiv:2506.09263 [astro-ph.EP].
- ^ "C/2021 O3 ( PanSTARRS )". Seiichi Yoshida.
- ^ @Worachate (April 29, 2022). "C/2021 O3 (PANSTARRS) was faintly visible in this STEREO/SECCHI COR2-A image on 2022 April 27" (Tweet) – via Twitter.
- ^ Q. Zhang; Q. Ye; T. L. Farnham; C. E. Holt (2022). "Disintegration of Near-Sun Comet C/2021 O3 (PANSTARRS)". The Astronomer's Telegram. 15358. Bibcode:2022ATel15358....1Z.
- ^ "Closest Approach to Earth 2022" (Closest Earth approach occurs when deldot flips from negative to positive). JPL Horizons. Retrieved 2021-09-29.
- ^ a b c M. Evangelista-Santana; M. De Prá; J. M. Carvano; C. de la Fuente Marcos; R. de la Fuente Marcos; et al. (2023). "Borderline hyperbolic comet C/2021 O3 (PANSTARRS) was fading as it approached the Sun" (PDF). Monthly Notices of the Royal Astronomical Society. 524 (2): 2733–2740. arXiv:2307.10029. Bibcode:2023MNRAS.524.2733E. doi:10.1093/mnras/stad2111.
- ^ D. Machholz (5 May 2022). "Darn! Comet C/2021 O3 PanSTARRS has disintegrated". EarthSky.org. Retrieved 10 June 2025.
- ^ "MPEC 2021-P05 : COMET C/2021 O3 (PANSTARRS)] (7-day arc)". Minor Planet Electronic Circulars. Minor Planet Center. 1 August 2021.
- ^ Archive of JPL #2 (with a 10 day arc)
External links
- C/2021 O3 at the JPL Small-Body Database