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 | 466 | |
| data interval | 2020 12 12 – 2025 02 04 | |
| data type | perihelion within the observation arc (FULL) | |
| data arc selection | entire data set (STD) | |
| range of heliocentric distances | 10.15 au – 7.76 au (perihelion) – 8.2 au | |
| type of model of motion | NC - non-gravitational orbits for symmetric CO-g(r)-like function | |
| data weighting | YES | |
| number of residuals | 914 | |
| RMS [arcseconds] | 0.29 | |
| orbit quality class | 1a+ | |
| orbital elements (heliocentric ecliptic J2000) | ||
|---|---|---|
| Epoch | 2023 12 02 | |
| perihelion date | 2023 12 01.88422170 | ± 0.00282642 |
| perihelion distance [au] | 7.76008108 | ± 0.00000880 |
| eccentricity | 1.00132043 | ± 0.00000646 |
| argument of perihelion [°] | 211.471450 | ± 0.000183 |
| ascending node [°] | 314.835630 | ± 0.000025 |
| inclination [°] | 158.014184 | ± 0.000006 |
| reciprocal semi-major axis [10-6 au-1] | -170.16 | ± 0.83 |
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.
| non-gravitational parameters | ||
|---|---|---|
| A1 [10-8au/day2] | 3.6569 | ± 0.6454 |
| A2 [10-8au/day2] | 2.2151 | ± 0.5182 |
| A3 [10-8au/day2] | -0.73084 | ± 0.07952 |
| m | -2.00 | |
| n | 3.000 | |
| k | -2.6000 | |
| r0 [au] | 10.000 | |
| α | 0.0100 | |