Uranus has a Trojan Companion
Posted on August 29, 2013
Astronomers from the University of British Columbia have discovered that Uranus has a Trojan companion. Trojans are asteroids that share the orbit of a planet. The Trojan asteroid 2011 QF99 is 60 kilometers wide. It is the first Trojan asteroid known to share the orbit of Uranus. The astronomers used the Canada-France-Hawaii Telescope's huge CCD camera MegaCam to discover the asteroid. Astronomers believe 2011 QF99 is part of a larger-than-expected population of transient objects temporarily trapped by the gravitational pull of the Solar System's giant planets. The Trojan's current position is marked by the red square in the above diagram. The black line shows the asteroid's projected trajectory 59,000 years into the future.
Mike Alexandersen, lead author of the study, said in a statement, "Surprisingly, our model predicts that at any given time three per cent of scattered objects between Jupiter and Neptune should be co-orbitals of Uranus or Neptune."
The research was published in the August 30th, 2013 edition of Science magazine. Here is an animation showing the motion of 2011 QF99, as seen from above the north pole of the solar system.