Non-gravitational motion of the Jupiter-family comet 81P/Wild 2

I. The dynamical evolution

Space Research Centre of the Polish Academy of Sciences, Bartycka 18A, 00-716, Warsaw, Poland e-mail: mkr@cbk.waw.pl

Received: 4 July 2005
Accepted: 29 September 2005

Abstract

We investigated the influence of the non-gravitational effects on the orbital motion of 81P/Wild 2. First, the non-gravitational accelerations on cometary nucleus throughout all five revolutions around the sun were analysed using both the symmetrical and the asymmetrical -function. Next, the symmetric model was used to examine the past and future dynamical evolution of Wild 2 within the time interval of ±8 thousand years. We then introduced a statistical approach. In the most probable scenario for Wild 2 history, a few thousand years ago, this comet was an object with its perihelion close to the Jupiter orbit with an aphelion distance greater than the Neptune orbit: JN class, JE class, JT class, or even larger. Due to the extremely close approach to Jupiter in 1974, its future evolution differs substantially from earlier, so most probably, comet Wild 2 will survive as a typical Jupiter-family comet during the few thousand years that follow. After 8000 yr, however, the chance that the comet Wild 2 will still be a typical JF comet (with  AU) drops to 29%. Similarities between the orbital histories of Wild 2 and comets 16P/Brooks 2 and 67P/Churyumov-Gerasimenko are also discussed.