A Perihelion Barrier for the Transformation of Centaurs into Jupiter-family Comets

Centaurs are an ephemeral class of objects orbiting the Sun among the giant planets that can evolve into Jupiter-family comets (or JFCs) due to gravitational perturbations from the giant planets. In this work, we use numerical integration of massless test particles in the six-body problem (the Sun, four giant planets, and a test particle) to study the transformation of Centaurs into JFCs. We find that Centaurs can transform into JFCs via a rapid, continuous drop in perihelion distance to a value below 5.2 au typically within 5 yr from the start of the drop. We call these JFC perihelion drops. These drops are correlated with close approaches to Jupiter. A perihelion barrier may exist at 6.3 au that must be crossed from above in order for a Centaur to transform into a JFC due to a single close approach to Jupiter. Currently, 93 (or 11%) of the known Centaurs have a perihelion distance, q, below 6.3 au.