Most probably, the first man-made object outside atmosphere was V2, the first man-made object on Earth orbit was Sputnik. This plug, if it did not disintegrate (and most likely it did) and kept escape velocity when it exited the atmosphere, could claim to be the first man-made object to go to space and stay there.
Otherwise, that would be Luna 1, launched in 1959.
Biting the hand that feeds IT
