Rotate the Planet
Let's rotate our sun and planets in a counter clockwise direction.
Select the free transform tool.

Select the earth.

>Insert
>Keyframe

 
A keyframe is a new frame for the movie. It copies the previous frame. You can change it and it will give the illusion of movement.
Now, with the new keyframe selected, move the sun 90 degrees in the counterclockwise direction.
Insert four keyframes to make the sun move 360 degrees.
Test the movement.
>Control
>Play
You can also test your movie by dragging the playhead at the top of the document.
It is the read rectangle.

You can control the speed by selecting the fps icon at the top of the stage.

Save your document.