Question: I live above a star, but I do not burn.
I have 11 friends, but they do not turn.
I am visited in sequence: never, once, or repeatedly.
My initials are PQRS.
Now tell me, what do I mean?
Answer: '7' on a phone's number pad.
Question: I move faster in certain solids, but slower in certain gases. I am typically broken by objects with large masses. I can be used as for pleasure, practice, and even an alarm. If used excessively, I can cause harm. What am I?