What name does the question mark represent?
No cypher or decryption is involved, so don't worry about that if you were. This is likely to be easier than it looks. To start off, use the tags to help you out — they are key to solving this puzzle.
Good luck! :)
Edit 1: So the astronomy tag is merged with the outer-space tag. It's specific to astronomy though, just as a heads-up.
Edit 2: By the astronomy tag, I mean astrology. I created this puzzle on the belief that these two meant the same thing, but as shown in @Smock's comment below, there is a distinct difference.