Uranus has a 'Trojan asteroid,' astronomers say
Astronomers have spotted a 36-mile-wide asteroid leading ahead of Uranus, in an orbit thought to have been impossible.
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Anomalies in the orbital trajectory of asteroid 2011 QF99 suggest it is a temporary companion of Uranus, originally coming from the outer regions of the solar system. The scientists calculate it will share its orbit with the planet for just 70,000 years before escaping this Trojan point. In at most 1 million years, this object will rejoin the flood of planet-crossing bodies known as Centaurs from which it came.Skip to next paragraph
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Trojan asteroids across the solar system
Based on this new data, the researchers calculate that about 0.1 percent of all the asteroids and comets 6 to 34 astronomical units from the sun are Uranian Trojans at any given time, meaning Uranus has a virtually constant population of companions. They also estimated about 1 percent of all the asteroids and comets beyond Jupiter's orbit areNeptunian Trojans.
"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.
These temporary Trojans reveal objects traveling inward from the outer fringes of the 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."
The scientists detailed their findings in the Aug. 30 issue of the journal Science.
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