Crantor, a short-lived horseshoe companion to Uranus

Abstract

Context. Stable co-orbital motion with Uranus is vulnerable to planetary migration, but temporary co-orbitals may exist today. So far, only two candidates have been suggested, both moving on horseshoe orbits: 83982 Crantor (2002 GO 9 ) and 2000 SN 331 . Aims. (83982) Crantor is currently classified in the group of the Centaurs by the MPC although the value of its orbital period is close to that of Uranus. Here we revisit the topic of the possible 1:1 commensurability of (83982) Crantor with Uranus, explore its dynamical past, and look into its medium-term stability and future orbital evolution. Methods. Our analysis is based on the results of N-body calculations that use the most updated ephemerides and include perturbations by the eight major planets, the Moon, the barycenter of the Pluto-Charon system, and the three largest asteroids. Results. (83982) Crantor currently moves inside Uranus' co-orbital region on a complex horseshoe orbit. The motion of this object is primarily driven by the influence of the Sun and Uranus, although Saturn plays a significant role in destabilizing its orbit. The precession of the nodes of (83982) Crantor, which is accelerated by Saturn, controls its evolution and short-term stability. Although this object follows a temporary horseshoe orbit, more stable trajectories are possible and we present 2010 EU 65 as a long-term horseshoe librator candidate in urgent need of follow-up observations. Available data indicate that the candidate 2000 SN 331 is not a Uranus' co-orbital. Conclusions. Our calculations confirm that (83982) Crantor is currently trapped in the 1:1 commensurability with Uranus but it is unlikely to be a primordial 1:1 librator. Although this object follows a chaotic, short-lived horseshoe orbit, longer term horseshoe stability appears to be possible. We also confirm that high-order resonances with Saturn play a major role in destabilizing the orbits of Uranus co-orbitals.

A Uranian Trojan and the Frequency of Temporary Giant-Planet Co-Orbitals

“…Uranus has one known temporary (∼ 20 kyr) horseshoe companion (34) and 2011 QF 99 , the temporary L4 Trojan reported here. The Uranian co-orbital region is thought to be mostly unstable (6) although some stable niches may exist (7).…”

Asteroids in retrograde resonance with Jupiter and Saturn

“…The identified resonant configurations are temporary as the minor planets experience close encounters with the giant planets. This is akin to the temporary capture of NEAs in the (prograde) 1/1 resonance (Namouni et al 1999;Christou 2000) with the terrestrial planets and that of Centaurs in the same resonance with Uranus and Neptune(de la Fuente Marcos & de la Fuente Marcos 2012Marcos , 2013Alexandersen et al 2013).…”

Systematic survey of the dynamics of Uranus Trojans

“…In addition, 2014 YX 49 is identified as the second UT, temporarily on a high-inclined (i = 25.5 • ) tadpole orbit around L 4 (de la Fuente Marcos & de la Fuente Marcos 2017). Moreover, it was reported that there exist several possible Uranus companions such as 83982 (Crantor), 2002VG 131 , 2010EU 65 and 2015 , which are supposed to be on the transient horseshoe, quasi-satellite or even recurring co-orbital orbits (Gallardo 2006;de la Fuente Marcos & de la Fuente Marcos 2013, 2015. A detailed analysis of the dynamical evolution of these objects show that ephemeral multi-body MMRs could trigger the capture, ejection and switching between resonant co-orbital states of transient Uranus companions.…”

“…A detailed analysis of the dynamical evolution of these objects show that ephemeral multi-body MMRs could trigger the capture, ejection and switching between resonant co-orbital states of transient Uranus companions. Meanwhile, Jupiter and Neptune are found to render the long-term stability of them (de la Fuente Marcos & de la Fuente Marcos 2013Marcos , 2014Marcos , 2015Marcos , 2017. Actually, the specific mechanisms behind these objects are different from each other, indicating complicated dynamical properties of Uranus co-orbital regions.…”