I must not be paying attention to pop culture anymore - I hardly recognize anyone who's famous "just because", and am equally clueless about more than a few who at least have some sort of skill in film/recording/arts... Not that I ever really cared, but at least I used to be aware of the names and likenesses... A sure sign that I'm getting older...
That said, ooh, ohh, I have a good one!
Canadian
Astronaut
Cool guy
Even has the right moustache!
He's a bit older than young Trebek was, at 61, but OTOH, he's an intergalactic recording artist:
Chris Hadfield