C/2009 K5 McNaught
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Comet C/2009 K5 was discovered on 27 May 2009 by Robert H. McNaught (Siding Spring); that is about 11 months before its perihelion passage. The comet was observed until 26 October 2011.
Comet had its closest approach to the Earth on 18 April 2010 (1.264 au), 12 days before its perihelion passage.
Some trends in O-C time variations in the pure gravitational model based on entire data set were noticed, unfortunately, the NG effects cannot be reliably determined for this comet.
Preferred solution given here is based on data taken at large perihelion distances and spanning over 2.50 yr in a range of heliocentric distances: 4.35 au – 1.422 au (perihelion) – 6.49 au; however, two separate gravitational osculating orbits based on pre-perihelion (solution pa) and post-perihelion data (ra) are also presented.
This Oort spike comet suffers moderate planetary perturbations during its passage through the planetary system; these perturbations lead to a more tight future orbit (see future barycentric orbits).
See also Królikowska and Dybczyński 2013 and Królikowska 2020.

solution description
number of observations 820
data interval 2009 05 27 – 2010 04 29
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 4.35 au – 1.42au
detectability of NG effects in the comet's motion NG effects not determinable
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 1559
RMS [arcseconds] 0.33
orbit quality class 1a
orbital elements (barycentric ecliptic J2000)
Epoch 1710 12 04
perihelion date 2010 04 28.96807143 ± 0.00003067
perihelion distance [au] 1.41933112 ± 0.00000030
eccentricity 0.99993542 ± 0.00000078
argument of perihelion [°] 66.205123 ± 0.000027
ascending node [°] 257.740138 ± 0.000006
inclination [°] 103.924779 ± 0.000007
reciprocal semi-major axis [10-6 au-1] 45.50 ± 0.55
file containing 5001 VCs swarm
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.