Pluto and Neptune

General physics and astronomy discussions not directly related to Celestia
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Dust
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Pluto and Neptune

Post #1by Dust » 18.02.2004, 08:27

i saw in the rotation years ~500 and ~5200 that Neptune and Pluto are very close.

what is then happening to the paths of mainly Pluto, as he is the smaller of the 2.

i also recognized and read in the forum that the physics isn?t implemented to see if the path will change.

any suggestions? what will happen? is there a way to simulate and view it, also with another program?

JackHiggins
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Post #2by JackHiggins » 18.02.2004, 16:04

Dust

The closest approach in the year 500 was ~2.6AU, and ~8.9AU in 5230

Ignoring the second one- 2.6AU is more than 2 and a half times the distance from the earth to the sun! Just to give you some idea of scale, Earth's closest approach to Mars last august was a little under 0.373AU, and the orbits of both planets are still exactly the same! :)

Pluto & Neptune are in what's called a 3:2 resonance orbit- this means, basically, that for every 2 times Neptune orbits the sun, Pluto goes around 3 times. This also means that they will never come close enough to crash into each other, or even have their orbits changed much.

Celestia doesn't take into account gravity effects (in real time), but the "CustomOrbit" line in solarsys.ssc uses mathematical formulas to do the same job, and if Pluto's orbit was to change much, this would be shown up in Celestia.
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Post #3by Guest » 18.02.2004, 17:25

Stuff like long-term changes in eccentricity or node positions are probably not taken into account. These changes happen over millions of years. It's also possible that the 3:2 resonance may someday end. If Neptune is what ejected Pluto into its weird orbit, the reverse can always happen too. There may also be pertubations that are not understood or known. The program needs to know these things to account for them.
You can simulate this in Gravity Simulator (http://www.gravitysimulator.com). It will show you the rotation of nodes, and the changing eccentricity of the orbits, not because it knows of these things, but because it discovers them by painstakingly simulating step after step after step the positions of the planets using basic force formulas.

Evil Dr Ganymede
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Post #4by Evil Dr Ganymede » 20.02.2004, 03:25

Anonymous wrote:If Neptune is what ejected Pluto into its weird orbit, the reverse can always happen too.


Well, no - Pluto can't eject Neptune into a wacky orbit - it simply isn't anywhere near massive enough. Unless you meant that Pluto might be captured by Neptune, but for that to happen the orbits would have to get really screwy. :)


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