Researchers Confirm That Three Large Asteroids Have Orbits Similar To Uranus
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
In 2006, Uruguayan astronomer TabarÃ© Gallardo provided evidence that two asteroids, Crantor and 2000 SN331, had orbital periods similar to that of the planet Uranus — roughly 84 Earth-years. Now, some seven years later, researchers Carlos de la Fuente Marcos and RaÃºl de la Fuente Marcos, at the Complutense University of Madrid (UCM), have confirmed that not two, but three large asteroids follow the giant planet in its orbit, but the results were not as expected for 2000 SN331.
“The simulations we have carried out in the Data Processing Centre of the UCM indicate that 2000 SN331 does not have 1:1 commensurability with Uranus, but Crantor does, which means it orbits the Sun in exactly the same time period as the planet,” explained De la Fuente Marcos. Specifically, Crantor — a 70 km-wide asteroid — has orbital properties very similar to Uranus, displaced only by the gravitational force of the planet itself, as well as nearby Saturn.
In addition to the two previously known asteroids, a third, dubbed 2010 EU65, was also discovered with similar orbital characteristics. With yet another recently discovered object, known as 2011 QF99, possibly possessing matching properties.
Because these objects have an orbital path similar to that of Uranus they belong to a group known as Centaurs — icy planetoids that orbit between Jupiter and Neptune. However, according to De la Fuente Marcos “Crantor, 2010 EU65 and 2011 QF99 are the first bodies to be documented as co-orbiting with Uranus, although with distinct movements and trajectories.”
Crantor and 2010 EU65 maintain what is known as “horseshoe” orbits because they approach and recede from Uranus as they move around the Sun, sometimes coming quite close to the gas giant. By contrast, 2011 QF99 undergoes a Trojan orbit, whereby it maintains an orbit that is 60 degrees in front of Uranus, held there by the combined gravitational effects of the Sun and Uranus.
These objects will likely remain in the respective orbits for a few million years — a blink in the lifetime of the solar system. For comparison, the resent discovery of three new Mars Trojan asteroids is expected to maintain their orbits for billions of years, until the Sun reaches the end of its life.
Results of their work are published in Astronomy & Astrophysics and the Monthly Notices of the Royal Astronomical Society Letters.