I was joking about star names the other day when complaining about Rabastan Lestrange, but I noticed that in the tapestry in the movie there was in fact an Arcturus (one of the stars I mentioned). I wonder if he's actually mentioned in the canon anywhere or if they just made that one up for set dressing?

ETA: There definitely is at least one Arcturus Black, and of course Regulus was middle-named after him. *facepalm*