Could we please stop referring to any object in space we don't have details on as "mysterious"? "Mysterious" carries a connotation of "unusual" or having "unexpected or impossible properties" and none of these objects qualify.
The universe is littered with chunks of rocks and ice. Our solar system has an entire belt of them. It would ne nearly impossible to track every one. Heck, we can't even do that with the satellites WE toss into space.
While we're at it, maybe drop the "celestial"? Technically it's correct, but again, it's overselling the object because the word is uncommon in use.