LAUREL, Md. (AP) - A tiny, icy world a billion miles beyond Pluto is getting a New Year's Day visitor.

NASA's New Horizons spacecraft is set to fly past a mysterious object nicknamed Ultima Thule at 12:33 a.m. Tuesday. It will become the most distant world ever explored by humankind.

The flyby comes three and a half years after New Horizons swung past Pluto and yielded the first close-ups of the dwarf planet. This time, the drama will unfold four billion miles from Earth, so far away it will be 10 hours before flight controllers in Laurel, Maryland, know whether the spacecraft survived the close encounter.

Lead scientist Alan Stern said Monday the team has worked years for this moment and now, "it's happening!!"