One of my favorite activities for studying planets is to make a child-sized planetarium. The steps are simple and by doing hands-on assembly, children learn so much about our solar system.
*1) Obtain a washer or dryer box from a local appliance store. Paint all over the inside with black tempera paint. Paint the outside any colors you would like–or don't paint it.
*2) Using a used plastic playground ball, cut a hole just large enough to insert a flashlight. Cut a hole in the top of the box so that the ball will rest in the space and not fall through. This becomes the sun.
*3) Using styrofoam balls of varying sizes, paint or cover them with clay or playdough to represent each of the 9 planets. Attach a fish line string to each ball.
*4) On the outside top of the box, draw concentric ovals to represent the orbits of the planets. Punch 9 holes with a pen or small poking object, one on each of the orbit lines and spacing them so that the planets hang at various places within the box. From the inside, hang the planets by pushing the fishline string through the correct orbit hole, knot the string and/or tape it on the outside so they hold tight.
*5) Using glow-in-the-dark star stickers or paint, have children either form constellations or just randomly put stars on the inside of the box.
*6) Cut a small rectangular peep hole in one side of the box.
*7) When assembled, turn on the flashlight to make the sun glow and make the planets visible when someone peeps through the hole.
Enjoy! By the way, this is a GREAT science fair project!