Statistical Study of the Dynamical Properties of Long Period Comets

Based on comet observations from JPL (Jet Propulsion Laboratory) and MPC (Minor Planet Center), the orbits of long period comets (LPCs) were reverse-evolved to obtain their original orbits. The dynamic characteristics of LPC observation orbit and original orbit are analyzed. The results show that the distribution of reciprocal of the semi-major axis of LPC observation orbit (${(1/a)}_{\text{obs}}$) is significantly different from that of the original orbit (${(1/a)}_{\text{ori}}$), and the peak values are at ${(1/a)}_{\text{obs}}\sim 2\times {10}^{-5}{\text{au}}^{-1}$ and ${(1/a)}_{\text{ori}}\sim 6\times {10}^{-5}{\text{au}}^{-1}$, respectively; large perihelion LPC (perihelion distance $q>$ 3.1 au) and small perihelion LPC (perihelion distance $q$ $\le$ 3.1 au) have the same peak position of original orbit (${(1/a)}_{\text{ori}}$), both located at $1\times {10}^{-4}{\text{au}}^{-1}$; the peak positions of original reciprocal semi-major axis of LPCs between JPL and MPC are the same, both at $1\times {10}^{-4}{\text{au}}^{-1}$. Many Oort cloud comets have large perihelion distances (more than 50% of comets with $q>$ 3.1 au). It will provide information to understand the dynamical characteristics of long period comets and Oort cloud comets, and will also provide a research basis for future space missions targeting long period comets.