An icy rock located beyond Pluto is to be examined for the first time by NASA.
Its New Horizons spacecraft will fly within 2,220 miles of the object on New Year's Eve - providing the first close-up look at such a pristine building block of the solar system.
The Ultima Thule will be the most distant object ever visited by a spacecraft.
Got plans for #NewYears? Watch @NASANewHorizons make history as it reaches #UltimaThule, the farthest object ever explored by a spacecraft. ??https://t.co/Jn84tze2HY pic.twitter.com/j4LvhLmNz0
— Johns Hopkins APL (@JHUAPL) December 22, 2018
Ultima Thule is located in the Kuiper belt in the outermost regions of the Solar System.
On January 1st, it will be at a distance of almost 6.5 billion km - or four billion miles - from the Sun, making this the most distant planetary flyby that has yet been attempted, and the first time that a Solar System object of this type has been seen close-up.
Ultima Thule is around 30 km in diameter, and is irregularly shaped.
Image via @NASA on Twitter
In July 2017, it passed in front of a star as seen from Earth, allowing astronomers to determine its shape.
NASA says while not much is known about its surface, it will almost certainly have impact craters.
"The lighting environment at its surface is very dim, as it receives only about 0.05% of the light from the Sun that Earth does.
"We do know that Ultima Thule has a reddish color, probably caused by exposure of hydrocarbons to sunlight over billions of years.
"The flyby will also reveal whether it has any moons, or even a ring system."
Ultima Thule will be the most primitive planetary object yet explored, and will reveal what conditions were like in this distant part of the Solar System as it condensed from the solar nebula.
