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Re: Asteroid resonance - Reuter's


>Below is an article from 1998 which raises more questions than it answers.
>Now, given Ron's recent posts regarding 1999AN 10,  it might be helpful if
>we had some clarity on exactly what resonance is.

1999 AN10 is currently not in resonance, though
it may have been at one time when it was in was in the main asteroid
belt.

>The article below is misleading
>is several regards, not the least of which is that it refers to resonance as
>'nudging' an asteroid out of it's orbit, or 'knocking' it out, rather than
>'pulling' it out?   What precisely is the distinction between resonance and
>gravity?  Their net effect seems to be the same.

It all involves gravity.  Since Jupiter is the largest planet, it has
the most gravity, and has a verg noticeable effect on the main asteroid belt.
Several gaps have been observered in the asteroid belt, and these gaps
correspond with ratios of the Jupiter's orbital period. The gaps are
called Kirkwood gaps named after Daniel Kirkwood who first noticed them.
The common ratios are 2:1, 3:2, 3:1, 5:2, 4:3, etc.  For example for 2:1,
an object goes around the sun 2 times in exactly the time it takes
Jupiter to make 1 revolution.  Jupiter is obviously perturbing asteroids
whose orbits are in resonance with Jupiter's orbits, clearing out
certain areas in the asteroid belt.  As to why the
resonance is causing the asteroids to get nudged is still not 
clearly understood, but the effect is clearly there.  The asteroids that do 
get nudged are more likely to collide with other asteroids, changing its 
orbit even more, and eventually over millions or billions of years their 
orbits have changed so much that they are crossing the orbits of the other 
planets. And when they come near or crosses the Earth's orbit, then we label 
them as Near-Earth objects.

This resonance has also been observed elsewhere in the solar system.
The gaps in Saturn's rings are in resonance with the Saturn's larger
satellites.  Also, Pluto is in 3:2 resonance with Neptune, as are a
number of Kuiper Belt objects, which we call plutinos.

Ron Baalke

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