Astronomers from Canada and France have announced the
discovery of the first Trojan asteroid known to share its orbit with
Uranus.
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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