Trojan Asteroids Are More Common Than Previously Believed
August 30, 2013

Astronomers Discover First Trojan Asteroid Sharing The Orbit Of Uranus

[ Watch the Video: QF99 Motion Animation ]

April Flowers for - Your Universe Online

The first Trojan asteroid sharing the orbit of Uranus has been discovered by University of British Columbia astronomers who believe the asteroid - 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.

Trojan asteroids share the orbit of a planet and occupy stable positions known as Lagrangian points. Until now, astronomers have considered the presence of Trojans at Uranus unlikely because the gravitational pull of larger neighboring planets would destabilize and expel any Uranian Trojans over the age of the Solar System.

The astronomers created a simulation of the solar system and its co-orbital objects, including Trojans, to determine how the 37 mile-wide ball of rock and ice ended up sharing an orbit with the planet.

"Surprisingly, our model predicts that at any given time three percent of scattered objects between Jupiter and Neptune should be co-orbitals of Uranus or Neptune," says Mike Alexandersen, Department of Physics and Astronomy at UBC and the Institute of Planetary Science. This percentage, which is much higher than previous estimates, had never before been computed. Alexandersen was joined by UBC astronomers Brett Gladman, Sarah Greenstreet and colleagues at the National Research Council of Canada and Observatoire de Besancon in France in conducting this study, published in the journal Science.

During the past decade, several temporary Trojans and co-orbitals have been discovered in the Solar System. QF99 is one of those temporary objects. It was only recently captured by Uranus – within the last few hundred thousand years – and is set to escape the gravitational pull of the planet in about a million years.

"This tells us something about the current evolution of the Solar System," says Alexandersen. "By studying the process by which Trojans become temporarily captured, one can better understand how objects migrate into the planetary region of the Solar System."