C/2021 A9 PanSTARRS
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Comet C/2021 A9 was discovered on 12 January 2021 with the Pan-STARRS 1 telescope (Haleakala), that is almost two years before its perihelion passage. a few pre-discovery measurements were next found extending the data arc one month back. Comet is still observed as in April 2025.
Comet had its closest approach to the Earth on 3 January 2024 (6.80 au), about one month after its perihelion passage.
Preferred NG solution given here is based on data span over 4.15 yr in a range of heliocentric distances: 10.15 au – 7.76 au (perihelion) – 8.20 au; also GR orbits based on the same data arc as NG orbit and pre-perihelion orbital leg are given.
This Oort spike comet suffers tiny planetary perturbations during its passage through the planetary system; and its future orbit have semimajor axis notable longer than 10,000 au.
Comet had its closest approach to the Earth on 3 January 2024 (6.80 au), about one month after its perihelion passage.
Preferred NG solution given here is based on data span over 4.15 yr in a range of heliocentric distances: 10.15 au – 7.76 au (perihelion) – 8.20 au; also GR orbits based on the same data arc as NG orbit and pre-perihelion orbital leg are given.
This Oort spike comet suffers tiny planetary perturbations during its passage through the planetary system; and its future orbit have semimajor axis notable longer than 10,000 au.
| solution description | ||
|---|---|---|
| number of observations | 311 | |
| data interval | 2020 12 12 – 2023 11 21 | |
| data arc selection | data generally limited to pre-perihelion (PRE) | |
| range of heliocentric distances | 10.15 au – 7.76au | |
| detectability of NG effects in the comet's motion | comet with determinable NG~orbit | |
| type of model of motion | GR - gravitational orbit | |
| data weighting | YES | |
| number of residuals | 607 | |
| RMS [arcseconds] | 0.27 | |
| orbit quality class | 1a+ | |
| orbital elements (barycentric ecliptic J2000) | ||
|---|---|---|
| Epoch | 1713 10 08 | |
| perihelion date | 2023 12 05.51331844 | ± 0.00237618 |
| perihelion distance [au] | 7.76126603 | ± 0.00001351 |
| eccentricity | 0.99979285 | ± 0.00000602 |
| argument of perihelion [°] | 211.628774 | ± 0.000170 |
| ascending node [°] | 314.852285 | ± 0.000014 |
| inclination [°] | 158.005598 | ± 0.000012 |
| reciprocal semi-major axis [10-6 au-1] | 26.69 | ± 0.78 |
| file containing 5001 VCs swarm |
|---|
| 2021a9pa.bmi |
Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line — the moment of perihelion passage.
Six 2D-projections of the 6D space of original swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.