Wrong-way asteroid plays 'chicken' with Jupiter

March 29, 2017, University of Western Ontario
Asteroid Bee-Zed avoids colliding with Jupiter and with the Trojan asteroids with every wrong-way pass it makes. Credit: Western University (Canada), Athabaskan University, Large Binocular Telescope Observatory

For at least a million years, an asteroid orbiting the "wrong" way around the sun has been playing a cosmic game of chicken with giant Jupiter and with about 6,000 other asteroids sharing the giant planet's space, says a report published in the latest issue of Nature.

The , nicknamed Bee-Zed, is the only one in this solar system that's known both to have an opposite, retrograde orbit around the sun while at the same time sharing a planet's orbital space, says researcher and co-author Paul Wiegert of Western's Department of Physics and Astronomy.

All but 82 of the million or so known asteroids in our solar system travel around the sun in what's called a prograde motion: that is, counter-clockwise when visualized from above. But asteroid 2015 BZ509 ("Bee-Zed" for short) circles clockwise, in a retrograde motion—moving against the flow of all other asteroids in the giant planet's orbital entourage.

Put another way, it's as if Jupiter is a monster truck on a track circling the sun, and the asteroids in Jupiter's orbit are sub-compact cars all whizzing along in the same direction. Bee-Zed is the rogue—driving around the track in the wrong direction—steering between the 6,000 other cars and swerving around the monster truck. And it does so every single lap, and has done so for thousands of laps for a million years or more.

Western University asteroid expert Paul Wiegert explains how recently discovered asteroid Bee-Zed has managed to avoid slamming into Jupiter, despite its being on an apparent collision course with the giant planet. Credit: Western University, Ontario, Canada

So how does it avoid colliding with Jupiter? Jupiter's gravity actually deflects the asteroid's path at each pass so as to allow both to continue safely on their way, Wiegert says.

Little is known about the asteroid, which was discovered in January, 2015. It has a diameter of about three kilometers and it may have originated from the same place as Halley's comet, which also has a . The team hasn't been able to determine yet if Bee-Zed is an icy comet or a rocky asteroid.

But their analysis—based on complex calculations and on observations through the Large Binocular Camera on the Large Binocular Telescope in Mt. Graham, Arizona, during a span of 300 days—show Bee-Zed is somehow able to maintain a stable orbit even as an outlier.

The calculations conducted by the team show the has been stable for at least a million years and will be stable for at least a million more. Learning more about the asteroid provides another intriguing glimpse into previously unknown and unmapped features of our solar system. "The detective work has just begun," he said.

Explore further: Fragmented asteroid pair develops twin comet-like tails

More information: Paul Wiegert et al. A retrograde co-orbital asteroid of Jupiter, Nature (2017). DOI: 10.1038/nature22029

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not rated yet Mar 29, 2017
Could this be a capture from outside the solar system?
1 / 5 (2) Mar 29, 2017
Sounds worth considering for an Asteroid base for researching the Jupiter system and it's Trojans.

GDI's question...After a million years in an apparently stable orbit? Perhaps, if the rock's isotopes match-up with those yet to be determined from a mission to Halley's comet? Or not...

Probably, the original comet originated from the Kruiper Belt or even the Oort-Hills Cloud. When perturbed into the inner Solar System, Bee Zed broke off or was expelled by out-gassing as the comet dived inward.

If the isotopes do not match-up, another viable hypothesis could be. A collision of asteroids with Bee Zed forming out of the wreckage on a reversed course? Though maybe more likely, the original planetesimal took a nosedive into Jupiter's gravity field. And perhaps this piece was expelled from that event?

Of course, hitching a ride on that beast? Shooting the shoals of Jupiter? Would be the very definition of Mad Science!
3.3 / 5 (3) Mar 29, 2017
Obviously it's being driven by an American astronaut in a British orbit. ;)
not rated yet Mar 30, 2017
Could this be a capture from outside the solar system?

It seems likely that with such a path it is either a capture or the result of a pretty hefty crash close-by. The path itself doesn't really indicate whether it's from outside or just some bumped-in Oort cloud object.

such bodies could be induced by artificial means to harvest momentum for space exploration outside our solar system.

Not really. 'Harvesting' their momentum would just make you drop closer towards the sun. To get a boost four extrasolar exploration you need to take it from something that is moving *faster* than an orbiting body (or reduce the speed of an orbiting body through a swing-by maneouver).

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