Parts of this picture are excellent! In fact - most, if not every part of it is! The texture of the big planet looks great, the nebula looks really good - and the close-up clouds look really interesting. You don't fully succeed in putting the piece as a whole together though. The colour contrasts are too great and the composition is solid, but doesn't stand out.
You've created some spectacular objects, but still don't reach all the way with this piece.