C/2021 C5 PanSTARRS
more info
Comet C/2021 C5 was discovered on 12 February 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 about three weeks back.

Comet had its closest approach to the Earth on 20 June 2023 (2.80 au), more than four months after its perihelion passage.

The preferred NG solution given here ('c5') is based on data span over 3.53 yr in a range of heliocentric distances: 7.43 au – 3.24 au (perihelion) – 5.60 au.

This comet shows visible trends in the O-C distribution for a GR orbit. It is worth noting that, ignoring the existence of NG effects, the last two observations from early July 2024 (after an 11-month data gap) were rejected as poorly fitting the rest of the measurements. The problem disappears for the NG orbit, and these measurements already lie well in the orbit. However, some [O-C] trends are still visible before perihelion in the case of NG solution (first opposition).

This Oort spike comet suffers moderate planetary perturbations during its passage through the planetary system that lead to a more tight future orbit (semimajor axis of about 1,800-1,900 au).
solution description
number of observations 456
data interval 2020 12 22 – 2024 07 03
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 7.43 au – 3.24 au (perihelion) – 5.6 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 895
RMS [arcseconds] 0.30
orbit quality class 1a
orbital elements (heliocentric ecliptic J2000)
Epoch 2023 02 25
perihelion date 2023 02 11.06646343 ± 0.00023318
perihelion distance [au] 3.24193880 ± 0.00000244
eccentricity 0.99866083 ± 0.00000493
argument of perihelion [°] 270.919741 ± 0.000054
ascending node [°] 323.682676 ± 0.000030
inclination [°] 50.781455 ± 0.000011
reciprocal semi-major axis [10-6 au-1] 413.08 ± 1.52
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] 753.08 ± 27.71
A2 [10-8au/day2] -6.251 ± 30.489
A3 [10-8au/day2] 36.287 ± 10.903
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113