Comparison of original orbits of Oort Cloud new comets given in various
catalogues II. Different solutions from different observations
Recent observational and theoretical studies have greatly revealed the
dynamical nature of the Oort Cloud and its evolutionary history.
However, many issues are yet to be known. Our goal is to understand
current structure of this cloud as well as its dynamical origin. For
estimating the current structure of the Oort Cloud, key information lies
in the original orbit of the Oort Cloud new comets (OCNCs) that are
defined at a distance where these objects do not receive gravitational
perturbation from major planets (such as at r = 250 au from the Sun
before comets enter into the planetary region). There have been several
attempts to obtain OCNC’s original orbits, but it never has been an easy
task. This requires numerical orbit propagation of the observed comets
with high accuracy including perturbation from major disturbing bodies.
In addition, non-gravitational forces often play significant roles here.
First and foremost, the orbit determination of OCNC includes
substantially large uncertainty because of limited number of
observational arcs and very large eccentricity of the comets
(~1). Here I show our result of comparison of various
catalogues of OCNCs’ original orbital elements at r = 250 au: So-called
the Warsaw catalogue by Krolikowska, the ephemeris given by MPC (Minor
Planet Center), and that given by Horizons/JPL. In particular, I pay
attention to the difference of the original semimajor axis among the
several different solutions that the Warsaw catalogue and the MPC
ephemeris have in comparison with the solutions given by Horizons/JPL -
such as the difference between the solution 1 in the Warsaw catalogue
and the solution from Horizons/JPL, the solutions 1 and 2 in the Warsaw
catalogue, the solutions 2 and 3 in the MPC ephemeris and so forth. The
resulting orbits that these solutions yield look overall similar, but
sometimes they show stark difference for some reason.