First Trojan companion of Uranus discovered using CFHT
Using the Canada-France-Hawaii Telescope's huge CCD camera "MegaCam", a Canada-France collaboration of astronomers have discovered the first known Trojan companion of the planet Uranus. The Trojan, called 2011 QF99, was first identified by the team in CFHT observations from October 2011. With additonal CFHT observations between then and today, they confirmed the Trojan nature of the object. Read more
The discovery of the Trojan asteroid for Uranus suggests Uranus and Neptune could have far more such asteroid companions than previously thought, scientists say. In astronomy-speak, objects that share their orbit with a planet - but do not collide with the world - are known as Trojans. Such objects have been seen around several planets in our solar system, including the Earth, but the newfound asteroid 2011 QF99 near Uranus is the first ever seen for that planet. Read more
Uranus has a forbidden friend. The first asteroid to share the planet's orbit has been found, despite claims that Jupiter's mighty gravity should steal such companions away. The finding hints that more of these asteroids, called Trojans, lurk around unexpected worlds. Since Trojans don't always stay in place, finding new ones improves our picture of how space rocks migrate around the solar system. It also means there may be super-sized Trojans sharing orbits with massive exoplanets. Read more
Title: The first known Uranian Trojan and the frequency of temporary giant-planet co-orbitals Authors: 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.
Orbital elements:
2011 QF99
Epoch 2013 Apr. 18.0 TT = JDT 2456400.5 MPC
M 266.87910 (2000.0) P Q
n 0.01175115 Peri. 286.31989 -0.84417198 -0.52091457
a 19.1608990 Node 222.51181 +0.53486523 -0.80261768
e 0.1767221 Incl. 10.79614 +0.03595634 -0.29060776
P 83.87 H 9.7 G 0.15 U 3