Flipping minor bodies: what comet 96P/Machholz 1 can tell us about the orbital evolution of extreme trans-Neptunian objects and the production of near-Earth objects on retrograde orbits

TL;DR

This paper investigates comet 96P/Machholz 1's orbital dynamics to explain the clustering of extreme trans-Neptunian objects' arguments of perihelion and the origin of retrograde near-Earth objects.

Contribution

It demonstrates that the dynamical behavior of comet 96P/Machholz 1 can shed light on the orbital patterns of ETNOs and the production of retrograde NEOs, highlighting the role of Kozai resonance and orbital flips.

Findings

96P/Machholz 1 is in Kozai resonance with Jupiter.

Orbital flips can produce retrograde near-Earth objects.

The behavior persists with post-Newtonian corrections.

Abstract

Nearly all known extreme trans-Neptunian objects (ETNOs) have argument of perihelion close to 0 degrees. An existing observational bias strongly favours the detection of ETNOs with arguments of perihelion close to 0 degrees and 180 degrees yet no objects have been found at 180 degrees. No plausible explanation has been offered so far to account for this unusual pattern. Here, we study the dynamical evolution of comet 96P/Machholz 1, a bizarre near-Earth object (NEO) that may provide the key to explain the puzzling clustering of orbits around argument of perihelion close to 0 degrees recently found for the population of ETNOs. Comet 96P/Machholz 1 is currently locked in a Kozai resonance with Jupiter such that the value of its argument of perihelion is always close to 0 degrees at its shortest possible perihelion (highest eccentricity and lowest inclination) and about 180 degrees near its shortest aphelion (longest perihelion distance, lowest eccentricity and highest inclination). If this object is a dynamical analogue (albeit limited) of the known ETNOs, this implies that massive perturbers must keep them confined in orbital parameter space. Besides, its future dynamical evolution displays orbital flips when its eccentricity is excited to a high value and its orbit turns over by nearly 180 degrees, rolling over its major axis. This unusual behaviour, that is preserved when post-Newtonian terms are included in the numerical integrations, may also help understand the production of NEOs on retrograde orbits.