C/1937 C1 Whipple
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Comet C/1937 C1 was discovered on 7 February 1937 by Fred Lawrence Whipple (Harvard College Observatory, Massachusetts, USA), that is about 4.5 months before its perihelion passage, and the comet was last seen on 28 October 1937.Soon after, Whipple found a prediscovery image on plates exposed on 4 February. [Kronk, Cometography: Volume 4].
This comet made its closest approach to the Earth on 26 June 1937 (1.269 au), that is 6 days after perihelion passage.
Solutions given here are based on data spanning over 0.729 yr in a range of heliocentric distances from 2.44 au through perihelion (1.73 au) to 2.40 au.
Pure gravitational orbit determined from all available positional measurements (417 observations) give 1b-class orbit similarly as in Minor Planet Center (136 obs. used, the same arc of data; 1B-class, see MPC).
It was possible to determine the non-gravitational orbit for C/1937 C1 (preferred orbit); the derived NG solution give very similar original and future 1/a as in the case of pure gravitational model of motion.
This Oort spike comet suffers large planetary perturbations during its passage through the planetary system, and it left the planetary zone on a significantly more tight orbit with the future semimajor axis of about 720 au (see future barycentric orbits in both solutions: pure gravitational and non-gravitational).
More details in Królikowska et al. 2014.

solution description
number of observations 417
data interval 1937 02 04 – 1937 10 28
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 2.44 au – 1.73 au (perihelion) – 2.4 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 766
RMS [arcseconds] 2.48
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1937 07 06
perihelion date 1937 06 20.06167458 ± 0.00074574
perihelion distance [au] 1.73378562 ± 0.00000410
eccentricity 1.00014873 ± 0.00001307
argument of perihelion [°] 107.734189 ± 0.000445
ascending node [°] 128.607821 ± 0.000150
inclination [°] 41.551548 ± 0.000089
reciprocal semi-major axis [10-6 au-1] -85.79 ± 7.54
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] 2.146 ± 0.968
A2 [10-8au/day2] -0.002 ± 0.452
A3 [10-8au/day2] 0 (assumed)
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113