Hey hey, lovely to see the interest in this thread renewed
Sadly, neither of the answers provided is correct. You'd have to find how Túrin fits to the rest of the riddle
But I strongly suspect he doesn't. As for the Ursa Minor-Ursa Major guess, that's certainly a clever approach, but not a correct one. All of the references are strictly "in-universe".
Guessing Túrin is once again looking for
too advanced things in there.