As you can see from my pictures I had intended to use a marble for the sun. It turned out to be a bit too heavy to work properly. I ended up making the sun from the light weight clay. I stuck a piece of wire in it so that I could hold it while I painted it. I coloured it with orange and yellow sharpies and then painted it over with a mix of gold paint and nail polish.
For the rotation/revolution of the planets I was using the second hand mechanism on the clock. The way the hand fits into the clock mechanism seems to vary from clock to clock. For the one I had, the hand fit in with a pin. I was able to fit the pointy end of a bamboo skewer into the slot and have it rotate freely. I used that to hold the planets and the sun. I formed a little pedestal for the sun to fit on the skewer with the light weight clay, painted it with copper paint and glued it to the pedestal.
I then glued the sun to the pedestal and painted the bamboo skewer with gold paint.