C/2006 HW51 Siding Spring
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Comet C/2006 HW51 was discovered on 23 April 2006 with Siding Spring; that is about 5 months before its perihelion passage. It was observed until 7 August 2007 (see picture).
Comet had its closest approach to the Earth on 3 May 2006 (2.280 au), 10 days after its discovery.
Here, two solutions based on entire data set (a6 and n5) are very similar quality, and in Królikowska and Dybczyński 2013 we recomended pure GR solution for past and future orbital evolution. Both these solutions are based on data spanning over 1.29 yr in a range of heliocentric distances: 2.87 au – 2.259 au (perihelion) – 4.04 au. Here, we chose the NG solution as preferred;see Królikowska 2020.
This Oort spike comet suffers tiny planetary perturbations during its passage through the planetary system (compare original and future barycentric orbits for preferred orbit).

solution description
number of observations 187
data interval 2006 04 23 – 2007 08 07
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 2.87 au – 2.27 au (perihelion) – 4.04 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 359
RMS [arcseconds] 0.28
orbit quality class 1a
orbital elements (heliocentric ecliptic J2000)
Epoch 2006 09 22
perihelion date 2006 09 29.30983167 ± 0.00019951
perihelion distance [au] 2.26567694 ± 0.00000323
eccentricity 1.00234014 ± 0.00001114
argument of perihelion [°] 359.959572 ± 0.000067
ascending node [°] 228.127536 ± 0.000049
inclination [°] 45.809643 ± 0.000029
recip semi-major axis [10-6 au-1] -1,032.86 ± 4.92
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] -9.3344 ± 0.9748
A2 [10-8au/day2] 4.2714 ± 1.1083
A3 [10-8au/day2] 0 (assumed)
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113