Wow that's clever about the 'Alpha' thingo. Jo did say that the Black family were named after constellations (except the three sisters - Narcissa, Bellatrix). So I think your theory about Alpha is pretty strong

As we've talked about on other boards, it could well be another knew character (she's gotta stop doing this. Very Agetha Christie - the bad books - of her).

someone else on the site, mentioned the Bones. I don't know 'cause they're pretty antiVoldemort (what's left of them) so I doubt they'd know enough to know anything about Horcrux's. Then again it's pretty surprising that an 'also ran' like reggie Black found out about them...???