NASA will explore the most distant object ever probed by humankind early on New Year's Day - and scientists admit they have "no idea" what they will find.

Ultima Thule, a mysterious dwarf planet four billion miles from Earth, sits at the very edge of the solar system in a region known as the Kuiper Belt.

4 An artist's impression of New Horizons exploring Ultima Thule

A robotic probe called New Horizons will snap photos of the distant object in a bid to better understand the tiny worlds that dominate the outer reaches of our star system.

The machine will pass just 2,200 miles from Ultima, which orbits one billion miles further from Earth than Pluto.

Scientists at Nasa are unsure what secrets the mysterious space rock holds.

Dr Alan Stern, the mission's principal investigator, said: “What will Ultima reveal? No one knows. To me, that is what’s most exciting—this is pure exploration and fundamental science.”

4 New Horizons snapped its closest image yet of Ultima (circled) on December 24

Officially known as 2014 MU69, experts believe Ultima Thule is about 20 miles across, and has a red colour.

Scientists know it is a strange shape based on the unusual way it reflects sunlight, and some think the object may actually be a pair of space rocks.

Data collected by New Horizons will reveal what Ultima looks like, what it's made of, how cold it is, and whether it has any moons.

The readings will also uncover whether Ultima has an atmosphere – one of the key components for life.

4 New Horizons was originally launched to explore Pluto

"In the space of one 72-hour period, Ultima will be transformed from a pinpoint of light — a dot in the distance — to a fully explored world," Dr Stern said.

"It should be breathtaking.”

New Horizons still has a lot of ground to cover, but Nasa predicts its will clock its closest flyby at 5:33am GMT on January 1.

The probe, which is about the size of a baby grand piano, was launched in 2006 to explore Pluto's surface.

4 New Horizons will uncover whether Ultimate Thule is made up of one or two objects (artist's impression)

After its successful flyby of the planet in 2015, mission planners won an extension from Nasa to extend the probe's journey.

They settled on an object deep inside the Kuiper Belt, the so-called “twilight zone” stretching beyond Neptune.

Dr Stern said data from New Horizons has to travel so far that it will take two days to beam back to Earth.

“We expect to have an image with almost 10,000 pixels on Ultima ready for release on January 2,” he said.

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“By that first week of January we expect to have even better images and a good idea of whether Ultima has satellites, rings or an atmosphere.”

Deputy project scientist Cathy Olkin, also of the Southwest Research Institute, said: “From Ultima’s orbit, we know that it is the most primordial object ever explored. I’m excited to see the surface features of this small world.”

What do you think New Horizons will find on Ultima? Let us know in the comments!

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