1303.5774 (Mike Alexandersen et al.)

The first known Uranian Trojan and the frequency of temporary giant-planet co-orbitals    [PDF]

Mike Alexandersen, Brett Gladman, Sarah Greenstreet, J. J. Kavelaars, Jean-Marc Petit

Trojan objects share a planet's orbit, never straying far from the triangular Lagrangian points, 60 degrees ahead of or behind the planet. We report the first discovery of a Uranian Trojan: 2011 QF99 oscillates around the Uranian L4 Lagrange point for >70 kyr and remains co-orbital (in 1:1 resonance) for ~1 Myr before becoming a Centaur. Instead of being a primordial Trojan, it must be a temporary co-orbital. We construct a steady-state Centaur model, supplied from the transneptunian region, to investigate the frequency and duration of temporary co-orbital captures, finding that at any time large fractions (0.5 % and 1.9 %) of the population will be Uranian and Neptunian co-orbitals, respectively. We show for the first time that the high co-orbital Centaur fraction (~3 %) in the IAU Minor Planet Centre database is that expected under transneptunian steady-state supply.

View original: http://arxiv.org/abs/1303.5774