Activity of 50 Long-Period Comets Beyond 5.2 AU

TL;DR

This study analyzes the activity of 50 long-period comets beyond 5.2 AU, revealing that dynamically new comets are generally more active and have more symmetric comae than returning comets, with diverse morphological features.

Contribution

It provides a decade-long survey highlighting differences in activity and morphology between new and returning long-period comets beyond 5.2 AU.

Findings

Dynamically new comets show higher activity levels.

New comets have more symmetric, isotropic comae.

Presence of long, tenuous tails is common but not brightness-dependent.

Abstract

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by afrho values >3--4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.