C/2021 S3 PanSTARRS
more info
Comet C/ was discovered on 24 September 2021 with the Pan-STARRS 1 telescope (Haleakala), that is two years and almost five months before its perihelion passage. Later a few preperihelion measurements were found going back to December 2020. This comet is still observed (as in April 2025).

Comet had its closest approach to the Earth on 14 March 2024 (1.298 au), a month after its perihelion passage.

This comet displays trends in [O-C] diagram already within the pre-perihelion data arc. These trends only partially disappered when NG effects are included to orbital motion. The preferred NG solution currently given here is based on preperihelion data span over 3.19 yr in a range of heliocentric distances from 11.02 au to 1.32 au.

This is an Oort spike comet.
solution description
number of observations 1118
data interval 2020 12 06 – 2024 02 14
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 11.02 au – 1.32 au (perihelion) – 1.32 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 2219
RMS [arcseconds] 0.28
orbit quality class 1a
orbital elements (barycentric ecliptic J2000)
Epoch 1725 02 27
perihelion date 2024 02 14.66071115 ± 0.00007244
perihelion distance [au] 1.32445403 ± 0.00000125
eccentricity 0.99997556 ± 0.00000067
argument of perihelion [°] 6.812728 ± 0.000054
ascending node [°] 215.672107 ± 0.000018
inclination [°] 58.510767 ± 0.000007
reciprocal semi-major axis [10-6 au-1] 18.45 ± 0.51
file containing 5001 VCs swarm
2021s3pn.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.