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Space Science

Yarkovsky Effect On Asteroid Detected 19

Posted by michael
from the nifty-science dept.
Henry writes "New Scientist is reporting that a JPL team has measured the recoil effect of an asteroid caused by the Sun in the process of re-emission of absorbed sunlight as heat. Astronomers believe this phenomenon, known as the Yarkovsky Effect, has brought asteroids - which are otherwise mainly located in and near the belt - towards Earth. This effect on asteroids was previously predicted, but this is the first proof."
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Yarkovsky Effect On Asteroid Detected

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  • by Frennzy (730093) on Friday December 05, 2003 @03:24PM (#7640947) Homepage
    From the yarkovsky link in the article... ==== The effect of this tiny thrust on the object's orbit depends on how it spins. If the spin goes one way, Yarkovsky thrust adds to the orbital speed and the asteroid moves outward, away from the sun. If the asteroid rotates the other way, Yarkovsky thrust slows the asteroid's orbital velocity, and it draws closer to the sun.
  • by TwistedGreen (80055) <twistedgreen@gmai[ ]om ['l.c' in gap]> on Friday December 05, 2003 @03:27PM (#7640985)
    It'll mean the death of all of us.

    Though the second law will probably get us far sooner.

    More conclusive proof that the universe abhors life. It's just so negentropic.
  • by breon.halling (235909) on Friday December 05, 2003 @03:36PM (#7641069)

    ... I thought they were talking about the Yakov Effect [yakov.com].

  • by shweazel (583363) on Friday December 05, 2003 @03:36PM (#7641074)
    These guys collected 12 years worth of data, to finally determine that an asteroid 16 million kilometers from the earth was 15 kilometers further away than calculated by the influence of gravity alone.

    No wonder noone else was able to measure this till now..
  • that we must declare war and destroy the Sun immediately.

    We must act now before the Moonites coerce the Sun into smashing Earth in order to gain their freedom. We cannot compete with the Moonites' large stockpiles of pr0n and Foreigner paraphernalia, and they are not below using these terrorist asteroids to destroy our way of life.

    Down with the Sun. Long live Terra.
  • Impressive (Score:5, Interesting)

    by szyzyg (7313) on Friday December 05, 2003 @03:50PM (#7641210)
    But it just makes all those long term asteroid orbit simulations a little harder now, since not only do you have to know the position and velocity accurately, you now have to know it's spin and it's thermal properties. It's a great example of how orbital mechanics can be considered chaotic on reasonable timescales.

    Oh since I'm here - Oblibatory link to my map of the solar system showing all the near earth asteroids.....

    http://szyzyg.arm.ac.uk/~spm/ [arm.ac.uk]

  • by borroff (267566) on Friday December 05, 2003 @03:54PM (#7641256) Journal
    The White House's immediate reaction was to try to control the spin, thereby eliminating any deviation from the status quo.
  • Question.... (Score:1, Interesting)

    by Anonymous Coward
    Is there a Yarkovsky effect on the Earth as well? Why not?
    • Re:Question.... (Score:2, Interesting)

      by GizmoDuck (137089)
      My guess would be no, because the Earth's atmosphere would absorb the thrust. The particles would push directly on the mass of the asteroids, however, since very few have any atmosphere to speak of.
    • Good question (Score:5, Informative)

      by Tau Zero (75868) on Saturday December 06, 2003 @12:15AM (#7645448) Journal
      There probably is, because Earth is definitely warmer around sunset than around sunrise. This would mean greater IR emissions in the direction opposite the orbital motion, causing thrust in the direction of the orbit.

      However, the Yarkovsky effect on Earth is going to be much smaller (probably unmeasurably small) than on a sub-kilometer asteroid for these reasons:

      1. Earth's atmosphere and oceans buffer the temperature changes, leading to less variation in IR emissions per rotation and thus less net thrust.
      2. While the net IR emission is proportional to the intercepted sunlight and thus the area of Earth's disc (proportional to radius squared), the acceleration is inversely proportional to the mass (which is proportional to radius cubed). On top of this, Earth is denser than typical asteroidal rocks, due to its iron core and compression of lower layers to denser mineral forms.
      It would be interesting to calculate the likely influence of the Yarkovsky effect on Earth, as a high-school physics exercise (like calculating the De Broglie wavelength of a moving car). I suggest this exercise to you, for fun; if nothing else, it will give you an idea of how hard it is likely to be to measure it.
      • 'The Earth' is warmer at sunset? Where on Earth? It's always sunset somewhere. It feels warmer where you are at sunset because the air and ground have absorbed heat all day. The effect of solar wind and the earth's rotation and all that jazz has no perceptible change. How is this +5, Informative???
        • It's always sunset somewhere.
          that's the point. reread the post and rethink your response.
        • Yes, that's the whole point, it is always sunrise on the side of earth facing in the direction of earth's orbit, and sunset on the other side. Thus, the extra IR emission at the sunset side is giving earth a little extra push, always in the same direction, although it's a tiny tiny effect relative to the mass of earth, unlike some asteroids which can be much less dense.

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