Here, the solar system fits perfectly into the children's room. This ingenious model is easily assembled from over 50 parts. The core and driving force of the whole system is the sun - within it, the mechanics are built in that cause the planets to orbit in four paths. No batteries are even required for this. The mechanism in the sun is a wind-up motor - simply wind it up, and all the planets from Venus to Jupiter will revolve around the yellow center. Astronomy up close.