Solar System
Dynamics &
Planetology
Group 		SSDP Home Page of Near-Parabolic Comets


We start to construct the Cometary Database consisted of near-parabolic comets.
At these pages the new orbital solutions will be included systematically during the progress of our investigation.

For each comet are given three types of orbits:

Example of orbits and other data for an individual comet, e.g. the original and future barycentric position and velocities of 5001 clones at 250 au from the Sun are also available for each comet.

Accompanying materials: residuals and O-C diagrams (see example given above), samples of comets, published papers that include some parts of results presented here.

The method of orbital calculations

The equation of comet's motion are integrated numerically using the reccurent power series method (e.g. Sitarski 1989, Acta Astron. 39, 345, direct links to papers quoted here are in this page) taking into account perturbations by all planets and including the relativistic effects. All orbital calculations are based on the Warsaw numerical ephemeris DE405/WAW of the Solar system (Sitarski, 2002, Acta Astron. 52, pp 471-486), consistent with high accuracy with the JPL ephemeris DE405.

Original and future orbits

To calculate the original and future orbital elements as well as their uncertainties (taken at 250 au from the Sun where planetary perturbations are negligible) the dynamical calculations for swarms of starting osculating orbits were performed for each comet. Each swarm was constructed according to a Monte Carlo method proposed by Sitarski (1998, Acta Astron. 48, pp 547-561) where the entire swarm fulfil the Gaussian statistics of fitting to positional data used for a given osculating orbit determination (examples are in Królikowska and Dybczyński, 2010, MNRAS 404, 1886). Typically, each swarm consists of 5001 VCs including the nominal orbit; it was checked that this number of orbital clones gives a very sufficient sample for obtaining reliable statistics at 250 au from the Sun. Values of uncertainties of original/future orbital elements (including inverse semimajor axes 1/a) were derived by fitting the distribution of a given orbital element (including 1/a-distribution) of original/future swarm of VCs to Gaussian distribution. All distributions of orbital elements as well as1/a-distributions of analysed comets were still perfectly Gaussian at 250 au from the Sun.

Accuracy of the cometary orbit

In 1978 Marsden, Sekanina, & Everhardt (1978, AJ 83, 64) formulated the recipe to evaluate the accuracy of the osculating cometary orbits obtained from the positional data. Here, however, we used the new recipe of orbital quality assessment introduced by Królikowska & Dybczyński (2013, MNRAS 435, 440) where are discussed reasons why the modification of original MSE recipe was introduced. According to this new scheme the following classes of orbital quality are given (in order from excellent to extremely poor orbit): 1a+, 1a, 1b , 2a, 2b, 3a, 3b, 4.

Samples of near-parabolic comets