C/1946 U1 Bester
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Comet C/1946 U1 was discovered on 31 October 1946 by Michiel J. Bester (Boyden Station of Harvard College Observatory, Bloemfontein, South Africa), that is over three months before perihelion passage, and the comet was last seen on 2 October 1948. [Kronk, Cometography: Volume 4].
This comet made its closest approach to the Earth on 29 November 1946 (1.864 au), that is about one month after its discovery.
Solutions given here are based on data spanning over 1.918 yr in a range of heliocentric distances from 2.631 au through perihelion (2.408 au) to 6.316 au.
Pure gravitational orbit determined from all available positional measurements (141 observations) give slightly hyperbolic original barycentric orbit (1a-class orbit); also original orbit given in Minor Planet Center is slightly hyperbolic (97 obs. used, the same arc of data; 1A-class orbit, see MPC).
It was possible to determine the non-gravitational orbits for C/1946 U1 where a small decreases of RMS were obtained. Both these NG-solutions give elliptical original orbit (see original barycentric orbits).
This probably Oort spike comet suffers slight (GR and preferred NG solutions) or small (NG solution: n5) planetary perturbations during its passage through the planetary system. According to both solutions, however, it will enter the planet zone as Oort spike comet in the next perihelion passage (see future barycentric orbits).
More details in Królikowska et al. 2014.

solution description
number of observations 141
data interval 1946 11 02 – 1948 10 02
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 2.64 au – 2.41 au (perihelion) – 6.32 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 259
RMS [arcseconds] 1.20
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1947 02 24
perihelion date 1947 02 07.36318548 ± 0.00051934
perihelion distance [au] 2.40764364 ± 0.00000772
eccentricity 1.00089117 ± 0.00001878
argument of perihelion [°] 348.624923 ± 0.000178
ascending node [°] 35.558720 ± 0.000067
inclination [°] 108.174352 ± 0.000051
recip semi-major axis [10-6 au-1] -370.14 ± 7.80
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\day-2] 13.03 ± 4.61
A2 [10-8au\day-2] 0 (assumed)
A3 [10-8au\day-2] 0 (assumed)
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113