C/2021 Q4 Fuls
more info
Comet C/2021 Q4 was discovered on 26 August 2021 with the Mt. Lemmon Survey, that is a year and nine months before its perihelion passage. This comet is still observed (s in April 2025)

Comet had its closest approach to the Earth on 17 September 2023 (6.69 au), about three months after its perihelion passage.

The preferred NG solution given here ('c4') is based on data span over 4.68 yr in a range of heliocentric distances: 10.25 au – 7.56 au (perihelion) – 8.35 au.

This long-period comet suffers small planetary perturbations during its passage through the planetary system that lead to a more tight future orbit; its original and future orbits have semimajor axes of about 8,000 au and 3,600 au, respectively.
solution description
number of observations 545
data interval 2020 04 27 – 2024 12 31
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 10.25 au – 7.57 au (perihelion) – 8.35 au
type of model of motion NC - non-gravitational orbits for symmetric CO-g(r)-like function
data weighting YES
number of residuals 1066
RMS [arcseconds] 0.30
orbit quality class 1a+
orbital elements (barycentric ecliptic J2000)
Epoch 1712 05 06
perihelion date 2023 06 11.73886310 ± 0.00431198
perihelion distance [au] 7.55741544 ± 0.00002145
eccentricity 0.99902228 ± 0.00001441
argument of perihelion [°] 147.062775 ± 0.000264
ascending node [°] 183.298214 ± 0.000031
inclination [°] 71.517036 ± 0.000011
reciprocal semi-major axis [10-6 au-1] 129.37 ± 1.91
file containing 5001 VCs swarm
2021q4c4.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.