Spacecraft heads towards world past Pluto

A tiny, icy world 1.6 billion kilometres 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.

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 6.4 billion kilometres 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 the team has worked years for this moment and now, "it's happening!!"