The analemma criterion: accidental quasi-satellites are indeed true quasi-satellites

TL;DR

This paper introduces the analemma criterion as a method to identify true quasi-satellites in the Solar system by analyzing their sky trajectories, confirmed through observations and simulations of specific objects like 15810 (1994 JR1).

Contribution

The paper proposes the analemma criterion for distinguishing true quasi-satellites and demonstrates its effectiveness with real and synthetic data, including the case of Pluto's transient quasi-satellite.

Findings

Quasi-satellites trace analemmas similar to geosynchronous orbits.

The analemma shape depends on the host's axial tilt and the satellite's orbit.

The method confirms the quasi-satellite status of 15810 (1994 JR1).

Abstract

In the Solar system, a quasi-satellite is an object that follows a heliocentric path with an orbital period that matches almost exactly with that of a host body (planetary or not). The trajectory is of such nature that, without being gravitationally attached, the value of the angular separation between host and quasi-satellite as seen from the Sun remains confined within relatively narrow limits for time-spans that exceed the length of the host's sidereal orbital period. Here, we show that under these conditions, a quasi-satellite traces an analemma in the sky as observed from the host in a manner similar to that found for geosynchronous orbits. The analemmatic curve (figure-eight-, teardrop-, ellipse-shaped) results from the interplay between the tilt of the rotational axis of the host and the properties of the orbit of the quasi-satellite. The analemma criterion can be applied to identify true quasi-satellite dynamical behaviour using observational or synthetic astrometry and it is tested for several well-documented quasi-satellites. For the particular case of 15810 (1994 JR1), a putative accidental quasi-satellite of dwarf planet Pluto, we show explicitly that this object describes a complex analemmatic curve for several Plutonian sidereal periods, confirming its transient quasi-satellite status.