I've written a java program to model the solar system. All my planets move in very well defined, stable orbits. The sun, on the other hand, is doing some very weird stuff. I've attached a plot of its path, a very zoomed in and a very zoomed out one. It isn't spiralling gradually inwards or outwards, as far as I can tell it's going in weird, wobbly loops. How do I explain that?! Especially as the rest of the planets work so well?? In my model, all bodies are point masses and have circular orbits, and they orbit around their common centre of mass.