i cant find the thread made recently where i posted this example but the picture below shows how i implemented a rotating planet system. one of the major features here is that you can modify values like orbit radius, planet size, and you can use this to add moons which travel around their parent planet.
if you look in the variables section at the bottom left you will see the public variables i used which can be set in the details panel of the level editor on a per instance basis. note that rotation rate is the orbit speed.
