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Re: Resonance
Hello Bernd and List,
Thank you so much for your wonderful references, but I think you were
mislead by Ron's interjection of the Kirkwood Gaps which are not in question
here, nor is Jupiter's stronger resonance. My questions had to do with the
last half of the article which refer to the weaker resonances. I'll copy
the entire article again and post it below:
"September 25, 1998
Web posted at: 12:00 PM EDT
"Gravity Explains Why so many Asteroids Scare Us
WASHINGTON (Reuters) -- Astronomers said on Thursday they had explained why
so many asteroids come close enough to Earth to raise alarms and,
occasionally, hit us.
They said it is all due to a coincidence in their orbits known as resonance,
which nudges the asteroids into orbits that bring them close to Earth and
Mars.
A resonance occurs, for instance, when the Earth orbits the sun in one year,
an asteroid orbits the sun in precisely two years, and thus the Earth and
the asteroid always pass close to each other at exactly the same point.
This allows the Earth's gravity regularly to perturb the orbit of the
asteroid.
"It laps it," explained Richard Greenberg, an astronomer at the University
of Arizona. "Time and time again they line up exactly at the same position.
They have a gravitational effect at the same point, every time."
When this happens between Jupiter and an asteroid, Jupiter's strong gravity
gives the asteroid a little kick-- causing it to wobble.
Previous models have suggested that it takes a very strong resonance to kick
asteroids out of the asteroid belt between Jupiter and Mars and onto a
collision course with Earth.
But writing in the journal Science, Alessandro Morbidelli of the Armagh
Observatory in Northern Ireland and colleagues said it was found just a year
ago that such strong resonances would actually knock the asteroids right
into the Sun, or pitch them out of the solar system altogether.
Back to the drawing table for astronomers.
Morbidelli, who also works at the Turin Observatory, and his team designed a
computer model that shows weaker resonances are instead responsible. Their
model correctly predicts the 10 known asteroids in near-Earth orbits and 354
in orbits that bring them close to Mars.
Greenberg said the finding helps astronomers explain how the population of
near-Earth asteroids is replenished.
If new asteroids weren't constantly being knocked into the paths of Earth
and Mars, all of them would have long ago crashed into the planets and there
would be none left to write disaster movies about.
Greenberg, who wrote a commentary about the findings, said scientists had
always assumed that weaker resonances were not strong enough to affect the
asteroids.
"It turns out that weaker resonances are just right," he said in a telephone
interview.
"They're not too strong that they kick the asteroids into the sun or out of
the solar system, and they're not too weak so that the asteroids just stay
in the asteroid belt," he added.
"There are at least half a dozen of these weaker resonances. We hadn't
understood their strength."
Greenberg said the phenomenon could also explain meteorites, which are
pieces of asteroids. The name meteorite, he pointed out, comes from the same
word for meteorology.
Early observers assumed they came from the atmosphere, and were a weather
phenomenon, and not from space."
I originally wanted confirmation if 1999 AN 10 was under the influence of
these weaker resonances of Earth and/or Mars. Now the question simply
remains, are the weaker resonances of Earth and Mars responsible for the
perturbing of asteroids out of the belt and into near Earth orbit (and near
Mars orbit) instead of the stronger influence of Jupiter as once was
thought. It seems the article is saying so. Thank you so much for you kind
input, Bernd.
Best Regards,
Julia
-----Original Message-----
From: Bernd Pauli HD <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>
To: jjswaim <MissionControl@email.msn.com>
Cc: meteorite-list <meteorite-list@meteoritecentral.com>
Date: Tuesday, May 25, 1999 4:46 PM
Subject: Resonance
|jjswaim schrieb:
|
|> "It laps it," explained Richard Greenberg, an astronomer at the
|> University of Arizona. "Time and time again they line up exactly
|> at the same position. They have a gravitational effect at the same
|> point, every time."
|
|> Greenberg said the finding helps astronomers explain how
|> the population of near-Earth asteroids is replenished.
|
|> Greenberg, who wrote a commentary about the findings, said scientists
|> had always assumed that weaker resonances were not strong enough to
|> affect the asteroids.
|
|> Greenberg said the phenomenon could also explain meteorites, which
|> are pieces of asteroids. The name meteorite, he pointed out, comes
|> from the same word for meteorology.
|
|
|Hello Julia and List,
|
|Here are some useful references:
|
|Aoki S. (1978) Stability problem of Kirkwood gaps (Nature 257: 568).
|
|Brouwer D. (1963) The problem of the Kirkwood gaps in the asteroid belt
|(Astron J. 68:
|152-159).
|
|Chapman C.R. et al. (1978) The asteroids (Ann. Rev.Astron. Astrophys.,
|eds. G. Burbidge et al. Vol. 16, pp, 33-75).
|
|Danielsson L. (1978) The orbital resonances between the asteroid Toro
|and the Earth and Venus (Moon and Planets 18: 265-272.
|
|Danielsson L. et al. (1972) Capture resonance of the asteroid 1685 Toro
|by the Earth (Science 176: 906-907).
|Dohnanyi J.S. (1969) Collisional model of asteroids and their debris (J.
|Geophys. Res. 74: 2531-2554).
|
|Franklin F.A. et al. (1975) Minor planets and comets in libration about
|the 2:1 resonance with Jupiter (Astron. J. 80: 729-746).
|
|Froeschlé C. et al. (1976) On the dynamical topology of the Kirkwood
|gaps (Astron. Astrophys. 48: 389-393).
|
|Froeschlé C. et al. (1977) A qualitative comparison between the
|circular and elliptic Sun-Jupiter-Asteroid problem at commensurabilities
|(Astron. Astrophys. 57: 33-39).
|
|Froeschlé C. et al. (1979) New numerical experiments to deplete the
|outer part of the asteroidal belt (Astron, Astrophys. 72: 246-255).
|
|Giffen R. (1973) A study of commensurable motion in the asteroidal belt
|(Astron. Astrophys. 23: 387-403).
|
|Goldreich P. et al. (1973) The formation of planetesimals (Astrophys. J.
|183: 1051-1061).
|
|Greenberg R. (1977) Orbit-orbit resonances in the solar system:
|Varieties and similarities (Vistas in Astronomy 21: 209-239).
|
|Grecnberg R. (1978) Orbital resonance in a dissipative medium (Icarus
|33: 62-73)
|
|Greenberg R. et al. (1977) Size distribution of particles in planetary
|rings (Icarus 30: 769-779).
|
|Greenberg R. et al. (....) Resonances in the asteroid belt (in
|Asteroids, ed. By T. Gehrels, 1979, Univ. of AZ Press, pp. 310-333).
|
|Greenberg R. et al. (1975) Coupled librations in the motions of
|asteroids near the 2:1 resonance (Mon. Not. Roy. Astron. Soc. 173: 1-8).
|
|Heppenheimer T.A. (1975a) Adiabatic invariants and phase equilibria for
|first-order orbital resonances (Astron. J. 80: 465-472).
|
|Heppenheimer T.A. (1975b) On the alleged collisional origin of the
|Kirkwood gaps (Icarus 26: 367-376).
|
|Heppenheimer T.A. (1978) On the origin of the Kirkwood gaps and of
|satellite-satellite resonances (Astron. Astrophys. 70: 457-465).
|
|Heppenheimer T.A. (1979) Secular resonances and the early history of the
|solar system (Icarus).
|
|Janiczek P.M. et al. (1972) Resonances and encounters in the inner solar
|system (Astron. J. 77: 764-773).
|
|Jefferys W.H. (1967) Nongravitational forces and resonances in the solar
|system (Astron. J. 72: 872-875).
|
|IPATOV S.I. (1992) Evolution of asteroidal orbits at the 5:2 resonance
|(Icarus 95, 100-114).
|
|KNEZEVIC Z. et al. (1991) Secular Resonances from 2 to 50 AU (Icarus 93,
|316-330).
|
|MIGLIORINI F. et al. (1997) Vesta fragments from v6 and 3:1 resonances:
|Implications for V-type near-Earth asteroids and howardite, eucrite and
|diogenite meteorites (Meteoritics 32-6, 1997, 903).
|
|
|Best regards,
|
|Bernd
|
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