Simulation of planet collisions during solar system formation

This simulation shows a forming solar system, initially with many tiny planetesimals in close orbits. As time goes on, their gravity warps each other's orbits and eventually causes many of them to collide, fall into the star or be ejected. This is believed to be a real process during solar system formation, but in this simulation I've vastly speeded it up by making the planets very massive relative tot heir star. This simulation is one of many made during creation of the Australian National University's free online astrophysics courses: https://www.edx.org/xseries/astrophysics It was created using the VPython library (vpython.org)