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tony873004
2008-Mar-11, 01:43 AM
I was playing around with data from recently-discovered asteroids and noticed that 2008 AC45 was in a horseshoe orbit with Jupiter.

Earth is known to have a few well-publicized horseshoe asteroids: Cruithne and 2002 AA29. But a few papers I've read online conclude that Jupiter has no known horseshoe asteroids. But then they list a handful that are suspected horseshoes. I'm guessing that since they were discovered years ago, probably before it was realized that they were potentially horseshoe asteroids, that follow-up observations were never made, and the asteroids are considered lost.

But 2008 AC45 was only discovered 2 months ago. It shouldn't be too far from its extrapolated position. I wish I had a large telescope.

Here's some simulation screen shots:
I was playing around with some data for recently-discovered asteroids and noticed that 2008 AC45 is in a horseshoe orbit with Jupiter. To date, I can only find info on 3 other asteroids that are potentially in horseshoe orbits with Jupiter, none of them confirmed.

http://orbitsimulator.com/astr699/images/2008AC45.GIF

http://orbitsimulator.com/astr699/graphs/2008AC45.GIF

Noclevername
2008-Mar-11, 02:06 AM
Do you mean an asteroid in a horseshoe orbit? (http://en.wikipedia.org/wiki/Horseshoe_orbit)

tony873004
2008-Mar-11, 02:18 AM
Yes. This one has a horseshoe orbit in a frame co-rotating with Jupiter.

That's one not one of Wikipedia's better articles. Maybe if parallaxicality is reading, he can clean it up for them.

StupendousMan
2008-Mar-11, 03:16 AM
I was playing around with data from recently-discovered asteroids and noticed that 2008 AC45 was in a horseshoe orbit with Jupiter.



Very interesting. I suggest posting this information to the Minor Planet Mailing List group at Yahoo

http://tech.groups.yahoo.com/group/mpml/

and see what the people there think. There are plenty of experts on asteroid dynamics, plus plenty of people with big telescopes.

Give it a try!

Bozola
2008-Mar-11, 07:34 PM
fantastic!

tony873004
2008-Mar-11, 11:05 PM
JPL Horizons updated its solution today, and the new data shows trojan behavior, not horseshoe. So now this asteroid joins thousands of other Jupiter trojans. But JPL does not list any additional observations, so I wonder why the solution was updated.

Thanks, SM. I posted my finding there.

agingjb
2008-Mar-12, 12:04 AM
I know there's a lot of space out there, but I did wonder if a horseshoe orbit would be stable in the very long term given the number of Trojans in Jupiter's orbit.

Inversely, I also wondered if Cruithne has been effective in precluding significant Sun-Earth Trojans over similarly long time scales.

tony873004
2008-Mar-12, 12:35 AM
From what I'm reading, the horseshoe orbits in Jupiter's vicinity are not very stable. Using the original data, my simulation showed the horseshoe configuration to last about 12000 years (from 2000 years ago, to 10000 years from now).

But its not Jupiter's trojans that would destabalize it. Their combined masses are very insignificant compared to the masses of the planets that perturb the horseshoe asteroids out of their horseshoe configuration.

Cruithne is simply not massive enough for its gravity to even be considered in calculations of Earth trojan perturbations. Cruithne is also only a temporary horseshoe. It will leave this configuration in a few thousand years.