Don't be afraid to take advantage of the solid circle tool to get perfect circles. And the line and bezier tools. AVOID the fill tool unless your filling the entire canvas. It leaves behind little white specks that are hard to cover over. And try a black bg with little dots for stars, it would set the planets off nicely. Welcome.

Very nice AJ.... listen to the advice of others... and don't be afraid to experiment with all of the tools!