Astronomers from Canada and France have announced the discovery of the first Trojan asteroid known to share its orbit with Uranus.
This image shows the Trojan asteroid 2011 QF99 (Mike Alexandersen).
The team believes this asteroid, labeled 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.
Trojans asteroids are celestial objects that share the orbit of a planet, occupying stable positions known as Lagrangian points.
Scientists considered their presence 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.
To determine how the 37-mile-wide (60 km) ball of rock and ice ended up sharing an orbit with Uranus the astronomers created a simulation of the Solar System and its co-orbital objects, including Trojans.
“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,” said Dr Mike Alexandersen, who is a lead author of a paper published in the journal Science.
This percentage had never before been computed, and is much higher than previous estimates.
Several temporary Trojan asteroids and co-orbitals have been discovered in the Solar System during the past decade.
2011 QF99 is one of those temporary objects, only recently (within the last few hundred thousand years) ensnared by Uranus and set to escape the planet’s gravitational pull in about a million years.
“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,” Dr Alexandersen said.
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Bibliographic information: Mike Alexandersen et al. A Uranian Trojan and the Frequency of Temporary Giant-Planet Co-Orbitals. Science, vol. 341, no. 6149, pp. 994-997; doi: 10.1126/science.1238072
