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Neptune crossing KBOs
JRehling
post Oct 21 2006, 07:20 PM
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Question for those who might be able to work this out: How close do any known KBOs come to the orbit of Neptune. Secondarily, how close to any known KBOs come to Neptune itself? (In the usual case, with a 3:2 synchrony, the two questions might have very different answers.)

I ask partly because a close encounter could cause a KBO to take an "interesting" new orbit, flung into the inner solar system or far outwards. I ask partly to stick a needle in the Prague planet definition.
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paxdan
post Oct 21 2006, 08:37 PM
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Well there is at least one Neptune crossing KBO that i know of in a resonant orbit. It is designated 134340 in the MPC.
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alan
post Oct 21 2006, 09:22 PM
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When the Minor Planet Center announces a new resonant KBO usually at the end you see a mention of how close they get to Neptune for example
QUOTE
The 2/3 Neptune librators 2003 HA57, 2003 HD57, 2003 HF57, 2003 SO317, 2003 SR317, 2003 TH58, 2004 FW164 and 2005 TV189 remain more than 16, 15, 16, 17, 14, 12, 14 and 16 AU, respectively, from Neptune over a 14 000-year period.

2003 UR292 is the only one I recall with a close encounter of Neptune being mentioned
QUOTE
Orbital computations using the above precovery observations indicate the strong likelihood of close encounters with Neptune, well inside its sphere of influence, within a few millennia of the present time.
http://cfa-www.harvard.edu/mpec/K04/K04N19.html
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JRehling
post Oct 22 2006, 04:08 AM
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QUOTE (alan @ Oct 21 2006, 02:22 PM) *
When the Minor Planet Center announces a new resonant KBO usually at the end you see a mention of how close they get to Neptune for example
2003 UR292 is the only one I recall with a close encounter of Neptune being mentioned
http://cfa-www.harvard.edu/mpec/K04/K04N19.html


Thanks, Alan. That information let me find this:

http://www.hohmanntransfer.com/mn/0407/24.htm

The key information of which is:

"Pasquale Tricarico has done a quick integration into the past and future for 2003 UR292 with his ORSA software, based on just the nominal orbit. According to his analysis, the only thing we can say so far is that 2003 UR292 is subject to periodic close approaches to Neptune, which can just perturb UR292's orbit (encounter distance at ~1 AU) or send it on a different orbit (encounter distance at ~0.3 AU), with a somewhat small ejection chance (no ejection in 2x10^5 years). "

It sounds like arbitrarily close encounters can take place, meaning that just about any outcome could ensue.

Note that this object has a diameter of 175 km. While the probability of Neptune flinging it at the Earth must be incredibly slim, as far as I read things, it is possible, and the key fact of that is that it makes it far, far larger than any other discovered possible Earth-impactor. Did I say "far"? Sounds like with the right introduction to the blogosphere, we've got a New York Times article on our hands. It's an understatement to say that it could cause a mass extinction event: it might cause a universal extinction event if it struck. Which is, of course, extraordinarily unlikely, but it calls to mind a Pascal's Wager type of payoff matrix (except I can't think of anything we could do to stop it if it were coming, although we would have a hell of a long warning before it arrived).

Far more likely (but very unlikely still) would be that we'd get the most impressive comet ever seen if it passed through the inner solar system. Without about 100x the surface area of a typical comet nucleus, it would create an unimaginable tail. I think we'd be talking about a visual magnitude (very roughly) in the range of the full Moon.

Back to my other purpose for asking: Now that we know that Neptune isn't a planet, what does it say about Terra given that an object with four times Earth's diameter (and the third largest body orbiting the Sun) is to be officially regarded a "dwarf planet"?
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edstrick
post Oct 22 2006, 10:53 AM
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Centaurs and KB Scattered Disk objects are the KB's equivalent of near earth asteroids and main belt asteroids that have been kicked out of resonances. There's a perennial "leakage" of objects from orbits near resonances that get tweeked into a resonance. Then it's orbital elements get "stirred with a stick" and it's long term orbital life is on the order of millions to tens of millions of years.
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climber
post Oct 22 2006, 08:30 PM
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QUOTE (paxdan @ Oct 21 2006, 10:37 PM) *
Well there is at least one Neptune crossing KBO that i know of in a resonant orbit. It is designated 134340 in the MPC.

You're talking about the one that has got 4 sattelites, aren't you ?
So, your quote should be in the "Is 134340 a planet" thread biggrin.gif


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alan
post Oct 22 2006, 08:51 PM
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QUOTE
Back to my other purpose for asking: Now that we know that Neptune isn't a planet, what does it say about Terra given that an object with four times Earth's diameter (and the third largest body orbiting the Sun) is to be officially regarded a "dwarf planet"?
Don't be a lawyer. Everyone hates lawyers.
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JRehling
post Oct 23 2006, 12:32 AM
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QUOTE (alan @ Oct 22 2006, 01:51 PM) *
Don't be a lawyer. Everyone hates lawyers.


I quite agree, figuratively speaking. But I think someone (some committee) should decide to play the game right or not at all. Not at all is my preferred course. Playing it poorly is not a good choice.

"Lepton" has a perfectly fine definition. "River" hasn't had one forced onto it. "Planet" deserves no worse.
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karolp
post Oct 23 2006, 10:38 AM
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QUOTE (climber @ Oct 22 2006, 10:30 PM) *
You're talking about the one that has got 4 sattelites, aren't you ?
So, your quote should be in the "Is 134340 a planet" thread biggrin.gif


FOUR satellites? I thought it had only 3... Charon, Nyx, Hydra... and?...


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ugordan
post Oct 23 2006, 10:56 AM
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No, FOUR satellites, none of them planet: Pluto, Charon, Nix, Hydra tongue.gif


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climber
post Oct 23 2006, 11:03 AM
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QUOTE (karolp @ Oct 23 2006, 12:38 PM) *
FOUR satellites? I thought it had only 3... Charon, Nyx, Hydra... and?...

Oups!
Or may be 4th name's Ytbd*, I guess.

* Yet To Be Discovered biggrin.gif


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