'Trojan' asteroids in far reaches of solar system more common than previously thought

Aug 29, 2013
This image shows the motion of 2011 QF99 over the next 59 kyr. Shown here is the trajectory of 2011 QF99, according to the best fit to the observations. The current position is marked by a red square, and the black line shows the trajectory 59 kyr into the future. L4 and L5 are the triangular Lagrange points, the points in space which Credit: UBC Astronomy

University of British Columbia astronomers have discovered the first Trojan asteroid sharing the orbit of Uranus, and believe 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 are asteroids that share the orbit of a planet, occupying stable positions known as Lagrangian points. Astronomers considered their presence at Uranus unlikely because the gravitational pull of larger neighbouring planets would destabilize and expel any Uranian Trojans over the age of the Solar System.

To determine how the 60 kilometre-wide 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," says Mike Alexandersen, lead author of the study to be published tomorrow in the journal Science. This percentage had never before been computed, and is much higher than previous estimates.

Several temporary Trojans and co-orbitals have been discovered in the Solar System during the past decade. 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 in about a million years.

This is one of three discovery images of 2011 QF99 taken from CFHT on 2011 October 24 (2011 QF99 is inside the green circle). This is the first of three images of the same patch of sky, taken one hour apart, that were then compared to find moving light-sources. Credit: UBC Astronomy

"This tells us something about the current evolution of the Solar System," says Alexandersen. "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."

This video is not supported by your browser at this time.
A short-term animation showing the motion of 2011 QF99, as seen from above the north pole of the solar system. Credit: UBC

UBC astronomers Brett Gladman, Sarah Greenstreet and colleagues at the National Research Council of Canada and Observatoire de Besancon in France were part of the research team.

Explore further: Young binary star system may form planets with weird and wild orbits

More information: "A Uranian Trojan and the Frequency of Temporary Giant-Planet Co-Orbitals," by M. Alexandersen et al. Science, 2013.

Related Stories

Three centaurs follow Uranus through the solar system

Jun 18, 2013

Astrophysicists from the Complutense University of Madrid have confirmed that Crantor, a large asteroid with a diameter of 70 km has an orbit similar to that of Uranus and takes the same amount of time to ...

Asteroid found in gravitational 'dead zone'

Aug 12, 2010

There are places in space where the gravitational tug between a planet and the Sun balance out, allowing other smaller bodies to remain stable. These places are called Lagrangian points. So-called Trojan asteroids ...

How many planets are in the solar system?

May 28, 2013

I'm just going to warn you, this is a controversial topic. Some people get pretty grumpy when you ask: how many planets are in the Solar System? Is it eight, ten, or more?

Giant planet ejected from the solar system

Nov 10, 2011

(PhysOrg.com) -- Just as an expert chess player sacrifices a piece to protect the queen, the solar system may have given up a giant planet and spared the Earth, according to an article recently published in ...

NASA's Wise finds mysterious centaurs may be comets

Jul 25, 2013

The true identity of centaurs, the small celestial bodies orbiting the sun between Jupiter and Neptune, is one of the enduring mysteries of astrophysics. Are they asteroids or comets? A new study of observations ...

Recommended for you

Image: Hubble serves a slice of stars

4 hours ago

The thin, glowing streak slicing across this image cuts a lonely figure, with only a few foreground stars and galaxies in the distant background for company.

Evidence of a local hot bubble carved by a supernova

Jul 30, 2014

I spent this past weekend backpacking in Rocky Mountain National Park, where although the snow-swept peaks and the dangerously close wildlife were staggering, the night sky stood in triumph. Without a fire, ...

Astronomers measure weight of galaxies, expansion of universe

Jul 30, 2014

Astronomers at the University of British Columbia have collaborated with international researchers to calculate the precise mass of the Milky Way and Andromeda galaxies, dispelling the notion that the two galaxies have similar ...

Mysterious molecules in space

Jul 29, 2014

Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum. Forged in the fusion furnaces of ancient stars and ejected into space when those stars ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

tadchem
not rated yet Aug 29, 2013
Much would become apparent with a graphic depiction of the gravitational/dynamic equipotential surface tied to the sun/Uranus system. The Lagrange points will show as local minima/saddle points and the equipotential lines would suggest Trojan orbits.
foolspoo
3 / 5 (2) Aug 29, 2013
sick of hearing all this "more/less than we thought"
were still writing the first page on the book earth. we can't even comprehend the first page on the universe. keep the open mind and trek onward. stop with this all too common arrogance throughout our history that we are the most advanced, intelligent generation to grace these lands. we are proving that we are anything but.
GSwift7
5 / 5 (2) Aug 29, 2013
The Lagrange points will show as local minima/saddle points and the equipotential lines would suggest Trojan orbits


lol, the top graphic shows the Trojan orbit; it's the eliptical slinky shaped spiral shown in black. The trojan does a corkscrew behind the planet in this case.

sick of hearing all this "more/less than we thought"... blah blah blah


The whole point of science is rooted in the fact that we don't know anything. Nothing could be less arrogant than basic scientific research like this. You don't even bother doing it if you think you already know.

In a lot of cases, this "more than expected" simply means that it's on the high side of an estimated value, but still within the error bounds, so not really a surprise. News people like to use phrases that get people's attention, such as "Surprising results" or "Unprecedented discovery", but it's usually rather mundane when you start reading past the headline.