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Author Topic: Simulating Kirkwood Gaps  (Read 1795 times)


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Simulating Kirkwood Gaps
« on: March 08, 2015, 07:48:35 PM »
Hi guys,

First up, what a fantastic job you are doing, US2 is a great educational tool and great fun to use as well!

Now I have a question about simulating some basic n-body orbits. I titled this post Kirkwood Gaps, but really I'd just like to see some stable vs unstable orbits. Is it possible to do this? I've tried, for example, just the Sun, Jupiter, and a couple of small bodies (Ceres sized) on different orbits but I'm not sure whether I'm getting any meaningful results. What I'd like to see are some orbits being affected by resonance (such as we see in the Kirkwood Gaps), an elongation of orbits of bodies in resonance with Jupiter, etc. The graphing tool you have implemented works beautifully (although possible could do with some better control over the scale of the axes?) for doing this experiment.

I was also wondering if it was possibly to setup horseshoe or tadpole orbits? Or a simulation of the stability of the Lagrange points L4, L5 vs L1, L2, L3 (restricted 3-body problem). Again, I've not had any luck so far.

FYI the main bug I've encountered is that every time I setup a system and save it, when I reload the textures for the objects don't load. I assume you've found that since the Save option is disabled in the latest version.

Sorry if these questions have come up before. I am a bit late to the party. Keep up the great work!


  • Thomas Grønneløv
  • Development Team
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Re: Simulating Kirkwood Gaps
« Reply #1 on: March 09, 2015, 03:13:20 AM »
One big issue with orbit resonances, and similar simulations, is that often those effects are small and take a lot of periods to show any relevant effects.
This means that if you want to quickly see an effect, you need to either speed up time a lot, or scale the effect itself. If you turn up simulation time speed, you will have to turn down accuracy and then a small resonance effect will likely be lost in numerical errors. If you scale the effect, then you could potentially be able to see a quick effect, but we would generally need to add an analytical solution of this particular resonance effect on top of the pure gravitational nbody simulation.

Eric recently added tidal effects to orbits, which is such an extra layer on top of nbody, and which can be scaled, but that is one particular effect.

At one point, we will have better support for "offline calculations" where you can leave a system brewing overnight and do a fast playback in the morning, and here you could  potentially see such effects.

Setting up a horse show orbit is not something there is UI assistance for, but if you do the calculations for initial values yourself, and place the bodies, it should work just fine... if you keep accuracy at a reasonable level.


  • Universe Sandbox 1 Beta Team
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    • Astronomic Picture of the Day - Brazil
Re: Simulating Kirkwood Gaps
« Reply #2 on: March 14, 2015, 01:03:02 PM »
Until Universe Sandbox 1 it´s possible to use a rotating frame option, so we can simulate the patterns of resonance effects.

I post some tests of this functionality here, but it works perfectly in that time:


Unluckly the images are out today.