Moving the left and right arrows with the cursor is a great idea, especially since they don't move until you get close. It might be nicer if they would animate to the position when you first move the cursor over, though. It's kind of jumpy as is.
There's a bug though. If you click on first/last planet then the arrow will not appear at all. Naturally you expect right arrow when clicking the first planet. Vice versa.
That pattern just might catch on.