Survey of asteroids in retrograde mean motion resonances with planets

Abstract

Aims. Asteroids in mean motion resonances (MMRs) with planets are common in the solar system. In recent years, increasingly more retrograde asteroids are discovered, several of which are identified to be in resonances with planets. We here systematically present the retrograde resonant configurations where all the asteroids are trapped with any of the eight planets and evaluate their resonant condition. We also discuss a possible production mechanism of retrograde centaurs and dynamical lifetimes of all the retrograde asteroids. Methods. We numerically integrated a swarm of clones (ten clones for each object) of all the retrograde asteroids (condition code U < 7) from −10 000 to 100 000 yr, using the MERCURY package in the model of solar system. We considered all of the p/−q resonances with eight planets where the positive integers p and q were both smaller than 16. In total, 143 retrograde resonant configurations were taken into consideration. The integration time was further extended to analyze their dynamical lifetimes and evolutions. Results. We present all the meaningful retrograde resonant configurations where p and q are both smaller than 16 are presented. Thirty-eight asteroids are found to be trapped in 50 retrograde mean motion resonances (RMMRs) with planets. Our results confirm that RMMRs with giant planets are common in retrograde asteroids. Of these, 15 asteroids are currently in retrograde resonances with planets, and 30 asteroids will be captured in 35 retrograde resonant configurations. Some particular resonant configurations such as polar resonances and co-orbital resonances are also identified. For example, Centaur 2005 TJ50 may be the first potential candidate to be currently in polar retrograde co-orbital resonance with Saturn. Moreover, 2016 FH13 is likely the first identified asteroid that will be captured in polar retrograde resonance with Uranus. Our results provide many candidates for the research of retrograde resonant dynamics and resonance capture. Dynamical lifetimes of retrograde asteroids are investigated by long-term integrations, and only ten objects survived longer than 10 Myr. We confirmed that the near-polar trans-Neptunian objects 2011 KT19 and 2008 KV42 have the longest dynamical lifetimes of the discovered retrograde asteroids. In our long-term simulations, the orbits of 12 centaurs can flip from retrograde to prograde state and back again. This flipping mechanism might be a possible explanation of the origins of retrograde centaurs. Generally, our results are also helpful for understanding the dynamical evolutions of small bodies in the solar system.

On the dynamical origins of retrograde Jupiter Trojans and their connection to high-inclination TNOs

“…3 shows a temporal density plot of the S1 clones according to their average time spent in a particular orbit. Objects that reach a moderate-to-low-eccentricity, polar orbit have higher average lifetimes than objects that remain retrograde close to the ecliptic (also see Gallardo 2019;Li et al 2019). Correspondingly, these objects appear as darker shades of green in the density plot.…”

“…Some objects even flip to prograde motion in the presence of giant planets (e.g. Lithwick and Naoz 2011; Greenstreet et al 2012;Li et al 2019). This leads to what essentially constitutes a selection process that filters out the short-lived particles.…”

Dynamical structures of retrograde resonances: analytical and numerical studies

“…One year later, Morais & Namouni (2017) identified that 2011 KT19 is currently inside a 7:9 polar resonance with Neptune. In a recent survey of retrograde asteroids performed by Li et al (2019), the authors confirmed that 2011 KT19 is currently in a retrograde 7:9 resonance with Neptune.…”

“…According to Morais & Namouni (2013a) and Li et al (2019), it is known that asteroids 2008 SO218 and 1999 LE31 are currently inside the retrograde 1:2 resonance with Jupiter. For convenience, we mark their locations in the (a, e) space, as shown in Fig.…”

“…Li et al (2018) numerically explored the resonant behaviors of the clones for the minor bodies among Centaurs and Damocloids and they identified another four Centaurs (including 2006RJ2, 2006BZ8, 2017SV13 and 2012, which are potential candidates inside retrograde co-orbital resonances with Saturn. Furthermore, Li et al (2019) numerically investigated the possible retrograde resonant configurations of minor objects in the Solar system and they identified 38 asteroids to be trapped inside retrograde MMRs with planets.…”