The blue sphere is a star with strong "gravitational" pull, spinning itself to create rotational movement in the "planetary dust" which helps it stabilize into orbits, including wildly ecliptic orbits, nearly perfect circular orbits, and every now and then weird orbits inside the sun's orbit. Every now and than all orbits are destroyed, but orbits naturally form. In real life the "dust" would have it's own gravitational pull, forming larger "planets" rather than "asteroid belts."
An interactive 2D physics simulation by ben, running in the browser on Physion. Nothing to install. Open it to run the simulation, change any object's properties, or copy it into a scene of your own.