|Discovery date||26 July 2021|
|Orbital characteristics A|
|Observation arc||53 days|
|Orbit type||Oort cloud|
|Eccentricity||1.00005 (epoch 1950)|
1.002 (epoch 2021)
1.0001 (epoch 2100)
|Earth MOID||0.062 au|
|Jupiter MOID||2.16 au|
|Next perihelion||21 April 2022|
C/2021 O3 (PanSTARRS) is an Oort cloud comet, discovered on 26 July 2021 by the Pan-STARRS sky survey. It will come to perihelion on 21 April 2022 at 0.287 AU (42.9 million km). from the Sun. It might reach apparent magnitude 5-7 by late April 2022, but will only be 15 degrees from the Sun. C/2021 O3 will make its closest approach to Earth on 8 May 2022 at a distance of 0.60 AU (90 million km). As a dynamically new comet from the Oort cloud there is a high risk of disintegration.
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 0.99595±0.00444 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 may be ejected from the Solar System.