Long-period comets as a tracer of the Oort cloud structure

Abstract

A previous study showed that a fingerprint of the initial shape of synthetic Oort clouds was detectable in the flux of “new” long-period comets. The present study aims to explain in detail how such a fingerprint is propagated by different classes of observable comets to improve the detection of fingerprints. It appears that three main long-term behaviors of observable comets are involved in this propagation: (1) comets that remain frozen during the entire time span and become observable only because of an increase in their orbital energy at the very end of their propagation; (2) comets whose perihelion distance performs an almost complete galactic cycle, while their galactic longitude of the ascending node and cosine of the galactic inclination remain almost constant; (3) comets whose perihelion distance and cosine of the galactic inclination perform a full galactic cycle, while their galactic longitude of the ascending node performs a half a cycle. This investigation allowed us to define four different zones for the previous perihelion distance, in which one or two of the above long-term behaviors dominate. Considering the distribution of the cosine of the ecliptic inclination and the galactic longitude of the ascending node at the previous perihelion distance, for the different zones, several fingerprints of the initial disk shape were highlighted. Such fingerprints appeared to be quite robust since they were still present considering the reconstructed orbital elements, i.e., the elements obtained from the original orbit after a backward propagation over one orbital period considering only the galactic tides.