Wrong-way asteroid plays ‘chicken’ with Jupiter

Posted: March 30, 2017 by oldbrew in Celestial Mechanics, research, solar system dynamics
Tags: , ,

Credit: IB Times

It’s not yet known what the origin of asteroid (or comet) ‘Bee-Zed’ is or if it’s one of a class of similar objects in retrograde co-orbital resonance, as Phys.org reports. The researchers say ‘how it got there remains a mystery.’

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 asteroid, 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.

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 retrograde orbit. 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 orbit 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.

Source: Wrong-way asteroid plays ‘chicken’ with Jupiter | Phys.org

Video: Trojan Asteroids: Jupiter’s Prisoners

  1. oldbrew says:

    ‘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.’

    Tricky. Gravity is supposed to be a force of attraction only, not repulsion 😎

    Retrograde orbit: the satellite (red) orbits in the direction opposite to the rotation of its primary (blue/black) [credit: Wikipedia]

  2. BoyfromTottenham says:

    Dark gravity? 😉

  3. dscott says:

    So is this object maintaining a constant speed in it’s retrograde orbit? Is there a high rotation rate? Is the orbit circular or significantly elongated (i.e. apogee and perigee)?

    IF the orbit is circular, then it is artificial and is potentially an Easter egg left for us to find as a means of gauging our technological state.

  4. Jim says:

    Interesting, only discovered in 2015, but it’s been there for a million years? Illogical. It could have been captured into that orbit in 2014, especially if discovered in 2015. But, then all science predates mankind.

  5. oldbrew says:

    ‘The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptical orbit’

    Two measures of the eccentricity of Bee-Zed = 0.3808359243865~ and 0.3806618939718702~
    Source = http://rdcu.be/qthE
    Let’s say somewhere near 0.38075

    1/Phi² = 0.381966
    8/21 = 0.3809523 (8 and 21 are Fibonacci numbers)
    – – –
    ‘Its absolute magnitude is reported as 16.1 (ref. 15), implying a physical diameter of 3 km at an albedo of 0.07, which is appropriate for Trojans’

    Quite hard to spot a 3km sized object over 600 million km away from Earth – probably one reason why it didn’t happen before 2015.

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