You can create as many objects as you want using a loop.
For "loopname" from 1 to 2 - this would make 2 objects. You can use a variable for your loop amount of you want, so you can change the value any time.
Set loop.variable to choose (1,2,3,4,5)
For "loopname" 1 to loop.variable
As far as making sure the same planet doesn't appear twice you will need to do another loops to compare animation frames, and if they are the same then pick one at random and change it again.
~Sol