There is a layer effect that puts a gradient on whatever is not transparant. Otherwise you can throw gradients in your five pointed star with the box 'preserve transparancy' ticked. The layer effect is editable, so that is a good reason to use it. If you want to fill your five pointed star with the blood of a lamb and put candles on the points while chanting backwards 'spirit of the dark side come upon me!' and hope for something to happen, you have watched too many movies.