C/2021 Y1 ATLAS
more info
Comet C/2021 Y1 was discovered on 26 December 2021 by ATLAS-MLO (Mauna Loa), that is a year and five months before its perihelion passage. Next, two series of pre-discovery images taken by M Holbroook at Pleasant Groves Observatory on two days in November (8 and 24) were found.

Comet had its closest approach to the Earth on 12 December 2022 (1.69 au), about 5.5 months before its perihelion passage.

The preferred NG solution given here is based on data span over 1.61 yr in a range of heliocentric distances: 5.91 au – 2.032 au (perihelion) – 2.11 au. However, even this NG solution exhibits some trends in [O-C] within a few months before perihelion passage. Thus, we also offer the solution 'd5' for past orbital study.

This Oort spike comet suffers rather small planetary perturbations during its passage through the planetary system that lead to escape the comet from the planetary zone on a hyperbolic orbit.
solution description
number of observations 1869
data interval 2021 11 08 – 2023 06 16
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 5.91 au – 2.03 au (perihelion) – 2.11 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 3666
RMS [arcseconds] 0.33
orbit quality class 1a
orbital elements (barycentric ecliptic J2000)
Epoch 1723 01 29
perihelion date 2023 04 29.54448226 ± 0.00006166
perihelion distance [au] 2.02536720 ± 0.00000074
eccentricity 0.99994942 ± 0.00000074
argument of perihelion [°] 245.949051 ± 0.000032
ascending node [°] 244.885673 ± 0.000002
inclination [°] 77.182007 ± 0.000006
reciprocal semi-major axis [10-6 au-1] 24.97 ± 0.37
file containing 5001 VCs swarm
2021y1n5.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.