5.3.4 C/1986 P1 Wilson

This is very difficult comet to investigate because of its splitting into two fragments. According to MWC08, the main component A of this comet exhibits NG acceleration in the time interval 1986 August 05 – 1989 April 11. Therefore, we also determined the NG effects from the whole observational arc (see Table 1) and next starting from these nominal orbits (GR and NG) the past and future orbital evolution have been analyzed. It turns out that the fragment B was a small piece of parent body and had ceased all activity or had disintegrated after April 1989. To estimate the possible uncertainty connected with this splitting we tried to find the nominal orbits from two separate sets of data: before and after splitting, but the exact date of this break-up is not clear. During comet’s observation on 1988 February 13 was discovered that nucleus was fragmented. However, Meech et al. (1995) argued that the most preferable date for splitting was mid-October 1987 because of the likely connection with a brightness of outburst in that time. Thus, we decided to determine the past orbit of C/1986 P1 from the time interval 1986 August 05 – 1987 July 04 (next astrometric observation was taken three months later on October 2) and the future orbit from the time interval 1987 October 26 – 1989 April 11 (114 observations). We derived values of (53.14±4.14)×10^-6 AU^-1 and (30.12±1.84)×10^-6 AU^-1 for 1/a_ori;NG and 1/a_ori;GR , respectively, where NG solution was determined with rms=1.30 arcsec and pure gravitational solution – with rms=1.35 arcsec. In this approach we derived 37.6^+4.1_-3.4×10³ AU and 1.90^+0.38_-0.22 AU for previous aphelion and perihelion passage, respectively, where by adding the lower and upper errors to nominal value the deciles of 10% and 90% can be derived and directly compared with respective values in Table 3. By comparing both results of previous perihelion swarms we stated that the comet C/1986 P1 were deeply inside inner solar system with perihelion not larger than 4AU and aphelion less than 5×10⁴ AU.

For the data taken after the splitting the NG effects were indeterminable. The VCs swarm of future motion is the most compact in our sample, what can be observed in Fig.18. We derived the value of (749.48±9.83)×10^-6 AU^-1 for 1/a_fut;GR By comparing this value with result given in Table 4 we conclude that this comet will start subsequent perihelion passage with small q (approximately 1.2AU) and with aphelion distance Q≅3 000AU, very similar to future aphelion distance of Comet C/1996 B2 Hyakutake.

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