Sound had been rejected before. This may change but don't count on it.
As for your other two suggestions.... What?? Planets, moons, stars, habitable zones? Slow down. Say why these should be added. Say what you mean by "land on them". Why don't you read the "how to suggest an element" topic which has been linked to you many times.
This game doesn't have per-pixel gravity. Stars, planets and moons will not work. Orbits will not work. This suggestion would be much better off as it's own separate game.
Stop suggesting this. Stop hijacking other threads to post this. Just stop, take a minute to collect your thoughts, and then decide whether or not you should hit "post."