[ But is it enough to qualify as a mass? Maybe just a shared one, a level below mass, if that's a thing. ]

Well, yours could have been influenced by mine. It still should have been kind of different, though, and it looks exactly the same.

... Can you bring it in here? Maybe if we both touch the same one at the same time, we can tell if it's real.

[ Granted, it's a star so both of them touching it almost certainly means it can't be real, but that has to at least mean it's not a hallucination. ]