Trojan Asteroid Discovered in Orbit of Uranus, Captured by Giant Planets

Astronomers have made a surprising discovery. They've found the first Trojan asteroid sharing the orbit of Uranus and believe that it could be part of a larger-than-expected population of similar objects. The findings could shed light on the distant planet.

Trojans are asteroids that share the orbit of a planet. They occupy stable positions known as Lagrangian points. These points mark positions where the combined gravitational pull of two large masses provides precisely the centripetal force required to orbit with them. Before now, though, researchers thought the presence of Trojans near Uranus to be unlikely; they believed the gravitational pull of larger neighboring planets would destabilize and expel any Uranian Trojans over the age of the solar system.

This new discovery, though, seems to indicate otherwise. The newest asteroid has been named 2011 QF99 and currently shares the orbit of Uranus. Yet in order to determine exactly how this 37-mile-wide rock managed to share an orbit with the planet, the researchers decided to do a bit of investigation. They created a simulation of the solar system and its co-orbital objects, including Trojans.

"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," said Mike Alexandersen, lead author of the new study, in a news release. "This tells us something about the current evolution of the solar system. 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."

The findings reveal that it's very possible this latest Trojan is part of a whole population of these objects, trapped by the gravitational pull of planets. In fact, QF99 probably was only snagged by Uranus in the last few hundred thousand years--a mere blink of an eye when it comes to the cosmos.

The findings are published in the journal Science.

Want to see a video of the asteroid and it motions? Check it out below, courtesy of YouTube and UBC Astronomy.