Ruh Roh, a Trojan Asteroid

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PASADENA, Calif. – Astronomers studying observations taken by NASA’s Wide-field Infrared Survey Explorer (WISE) mission have discovered the first known “Trojan” asteroid orbiting the sun along with Earth.

Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn’s moons share orbits with Trojans.

Scientists had predicted Earth should have Trojans, but they have been difficult to find because they are relatively small and appear near the sun from Earth’s point of view.

“These asteroids dwell mostly in the daylight, making them very hard to see,” said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery in the July 28 issue of the journal Nature. “But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.”

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Comments

  1. #1 Birger Johansson
    July 28, 2011

    Alas, since “trojan” asteroids rarely stay near the L4 and L5 poins, but rather oscillate around them with great orbital inclinations, the odds are you cannot make a sample-return mission to this one without excessive delta-v.

  2. #2 betty
    July 28, 2011

    I totally agree with Birger! Haven’t g straightenersot a lot of confidence in the wise mision

  3. #3 Greg Laden
    July 28, 2011

    Phil has a detailed description of what’s going on with this rock: http://blogs.discovermagazine.com/badastronomy/2011/07/27/wise-finds-the-very-first-earth-trojan-asteroid/

  4. #4 Raging Bee
    July 28, 2011

    Whoa. What correlation of forces would cause an asteroid to have an orbital path like THAT?

    I’ve known about Lagrange points for some time, but I’ve never heard an object could be moored into one.

    Technically, there are called Lissajous orbits…

    As opposed to frabjous orbits?

  5. #5 Raging Bee
    July 28, 2011

    Whoa. What correlation of forces would cause an asteroid to have an orbital path like THAT?

    I’ve known about Lagrange points for some time, but I’ve never heard an object could be moored into one.

    Technically, there are called Lissajous orbits…

    As opposed to frabjous orbits?

  6. #6 Calli Arcale
    July 28, 2011

    Trojan companions are actually fairly common, and it was expected that Earth would have some; nobody’d ever spotted them. Mars has companions, as do Jupiter (with the two groups traditionally named for Greeks and Trojans, giving name to the class of object) and Neptune. Saturn and Uranus probably do too, but there’s a lot of luck in spotting them. Several of Saturn’s moons have trojan companions. Helene is a leading trojan companion of Dione, and Telesto and Calypso are trojan companions of Tethys (Telesto leads, Calypso trails).