Oort spike comets with large perihelion distances

TL;DR

This study analyzes large-perihelion nearly-parabolic comets from 1901-2010, revealing their orbital evolution, the influence of planetary and stellar perturbations, and distinguishing dynamically new from old comets based on their original semimajor axes.

Contribution

It provides a comprehensive dynamical analysis of large-perihelion comets, incorporating Galactic and stellar perturbations, and identifies key orbital characteristics differentiating new and old comets.

Findings

Distribution of planetary perturbations has a deep minimum around zero.

Dynamically new comets have original semimajor axes >20,000 au.

Dynamically old comets are absent for semimajor axes >40,000 au.

Abstract

The complete sample of large-perihelion nearly-parabolic comets discovered during the period 1901-2010 is studied starting from their orbit determination. Next, an orbital evolution that includes three perihelion passages (previous-observed-next) is investigated where a full model of Galactic perturbations and perturbations from passing stars have been incorporated. We show that the distribution of planetary perturbations suffered by actual large-perihelion comets during their passage through the Solar system has a deep, unexpected minimum around zero which indicates a lack of "almost unperturbed" comets. By a series of simulations we show that this deep well is moderately resistant to some diffusion of orbital elements of analysed comets. It seems reasonable to state that the observed stream of these large-perihelion comets experienced a series of specific planetary configurations when passing through the planetary zone. An analysis of the past dynamics of these comets clearly shows that dynamically new comets may appear only when their original semimajor axes are greater than 20 000 au. However, only for semimajor axes longer than 40 000 au dynamically old comets are completely not present. We demonstrated that the observed $1/a_{\rm ori}$ distribution exhibits a local minimum separating dynamically new from dynamically old comets. Long-term dynamical studies reveal a large variety of orbital behaviour. Several interesting examples of action of passing stars are also described, in particular the impact of Gliese 710 which will pass close to the Sun in the future. However, none of the obtained stellar perturbations is sufficient to change the dynamical status of analysed comets.