...because a supernova is what you end up with "when a star dies". I think it IS Booster, because in the alternate timeline of the future where everything was changed with his going back in time (Think the Alterna-Biff version of Hill Valley in BTTF2), he was able to see what an ass he was after the events of the Crisis, and sets himself up to either a) save his own life or b) take over in his old spot with a new identity that does not have any of the bad connotations to it (since he is not exactly sure what having two Boosters in the same time period (and having them know about each other's existence) would do (same thing with Jennifer (young) seeing Jennifer (old) in 2015 of BTTF2.