| C/2021 O3 (PanSTARRS) | |
| Discoverer: | Pan-STARRS |
| Discovery Date: | 26 July 2021 |
| Epoch: | 2021-Aug-21 |
| Observation Arc: | 53 days |
| Obs: | 279 |
| Orbit: | Oort cloud |
| Perihelion: | 0.287 AU |
| Eccentricity: | 1.00005 (epoch 1950) 1.002 (epoch 2021) 1.0001 (epoch 2100) |
| Inclination: | 56.75° |
| Asc Node: | 189.03° |
| Arg Peri: | 299.97° |
| Tjup: | 0.446 |
| Earth Moid: | 0.062 AU |
| Jupiter Moid: | 2.16 AU |
| M1: | 10.6 |
| Last P: | 21 April 2022 |
C/2021 O3 (PanSTARRS) is perhaps an Oort cloud comet, discovered on 26 July 2021 by the Pan-STARRS sky survey. It came to perihelion on 21 April 2022 at 0.287abbr=unitNaNabbr=unit. from the Sun.
The comet was expected to reach apparent magnitude 5 by late April 2022, while being only 15 degrees from the Sun. While near perihelion the comet was dimmer than expectations. It was faintly visible in STEREO/SECCHI COR2-A on 27 April 2022. 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 disintegrated during perihelion.[1] C/2021 O3 made its closest approach to Earth on 8 May 2022 at a distance of 0.6AU. As a dynamically new comet from the Oort cloud there was a high risk of disintegration.[2]
The comet was recovered by multiple observatories after perihelion at magnitudes not too different from those observed pre-perihelion. 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.
With a short observation arc of 7 days, the Minor Planet Center used an assumed eccentricity of 1.0 for the orbit solution. Due to statistics of small numbers, with a short 10 day arc JPL had an eccentricity of which could be as high as 1.00039 or as low as 0.99151. With an observation arc of 53 days, JPL Horizons shows both an inbound and outbound eccentricity greater than 1.
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. This is also the most likely scenario when considering the post-perihelion orbit determination of the surviving object.