Its good for your first attempt, especially as you made if from scatch its good talent.

The planets, although position and shape were on point, lack a little in actually looking like a planet, they sort of look like they have simular patterns and a cotton top texture. Which isnt a bad thing, I actually would like to know how you made the texture..

But besides that, the lens flare is good, it gives it they spacey vibe, I think maybe on your next attempt add a few stars and background noise to add some depth into distance of how far away the planets are to eachother.
Cool though.

Here's a tutorial that could help: Planet TuT by Heartless