Near-parabolic comets observed in 2006–2010. The individualized approach to 1/a-determination and the new distribution of original and future orbits

Abstract

Dynamics of a complete sample of 22 small perihelion distance near-parabolic comets discovered in the years 2006 - 2010 is studied. First, osculating orbits are obtained after a careful positional data inspection and processing, including where appropriate, the method of data partitioning for determination of pre- and post-perihelion orbit for tracking then its dynamical evolution. The nongravitational acceleration in the motion is detected for 50 per cent of investigated comets, in a few cases for the first time. Different sets of nongravitational parameters are determined from pre- and post-perihelion data for some of them. The influence of the positional data structure on the possibility of the detection of nongravitational effects and the overall precision of orbit determination is widely discussed. Secondly, both original and future orbits were derived by means of numerical integration of swarms of virtual comets obtained using a Monte Carlo cloning method. This method allows to follow the uncertainties of orbital elements at each step of dynamical evolution. The complete statistics of original and future orbits that includes significantly different uncertainties of 1/a-values is presented, also in the light of our results obtained earlier. Basing on 108 comets examined by us so far, we conclude that only one of them, C/2007 W1 Boattini, seems to be a serious candidate for an interstellar comet. We also found that 53 per cent of 108 near-parabolic comets escaping in the future from the Solar system, and the number of comets leaving the Solar system as so called Oort spike comets is 14 per cent. A new method for cometary orbit quality assessment is also proposed that leads to a better diversification of orbit quality classes for contemporary comets.