Astronomers have discovered a "Trojan asteroid," a first for the planet Uranus, suggesting it could have more such companions with Neptune than previously thought, Space.com reported.
Trojans are not just limited to asteroids, as they can be any space object that shares its orbit with another planet, but does not collide. Trojans have been seen around the solar system, even Earth, but never before near Uranus.
The Trojan asteroid 2011 QF99 makes a triangle with the sun and Uranus. The third point of the triangle is called the Trojan point, or the Lagrangian point, after the mathematician who originally discovered it. It occurs when two objects' gravitational pull cancels each other out.
Earth has two Trojan points and other planets have them as well, but Uranus, the seventh planet from the sun, was believed to be too far away to have a Trojan point. Scientists using the Canada-France-Hawaii Telescope have discovered otherwise.
"Our search was focused on finding Neptunian Trojans and trans-Neptunian objects," study lead author Mike Alexandersen, an astronomer at the University of British Columbia in Vancouver, told SPACE.com. "One is always surprised and excited to find something other than what one was expecting and searching for."
2011 QF99 appeared to the researchers as a ball of ice and rock, apparently leading Uranus' orbit. The object, 36 miles wide, appears to be an asteroid but is more likely to be composed like a comet.
"This might trigger a wave of searches for Uranian Trojans - now that people know they exist, it will be easier to get telescope time to search for them than when it was thought unlikely to find anything," Alexandersen said.
The researchers estimated that about one percent of all comets and asteroids beyond Jupiter are Neptunian Trojans and also that Uranus has an almost constant set of companion Trojans.
The researchers published their findings in Friday's issue of the journal Science.
The discovery of these interim Trojans shows space objects traveling in from the outer edges of our solar system "aren't just being scattered all over the place in a seemingly chaotic fashion," Alexandersen said. "There are in fact these small reservoirs where objects get temporarily stuck, just like how sticks flowing down a river can sometimes get temporarily stuck circling in eddies or calm pools before finally escaping to continue down the river."
