On January 1^st 2019, the "New Horizons" spacecraft will fly over one of the most primitive and distant objects that humankind could ever lay its measuring hand on: Kuiper Belt's 2014 MU69, with its orbit a good billion kilometres farther from the Sun than it's fellow Kuiper Belt object, Pluto. The plan for the "New Horizons" is to take close-up shots of this prehistoric Solar System building block and explore its surroundings.

"New Horizons" is a NASA mission was launched in 2012 to explore far regions of the Solar System. The first important "stopover" of this spacecraft was a dwarf planet Pluto and its moon called Charon. Thanks to this "visit", now we have many high resolution images of these two objects and know far more about them. For example, it is known now that under Pluto's nitrogen and methane crust there is an ocean of liquid water.

Having sent the invaluable data back to Earth, "New Horizons" hibernated and resumed its way farther into Kuiper Belt. It would be more appropriate to call it a donut instead of belt, actually. Its objects, known as Kuiper Belt objects (KBOs), orbit around the Sun at a distance between 35 and 55 a.u. (1 astronomical unit = distance between the Earth and the Sun). Some of them are large (1200-2700 km in diameter) and massive: Eris, Pluto, 2007 OR₁₀, Makemake, Haumea and Quaoar. Others are pieces of primordial rock and metal, and the rest are large chunks of ice made of water, ammonia and methane. Many of its objects are in so-called resonance with Neptune. For example, Pluto orbits the Sun twice in the period of time it takes Neptune to complete its orbit 3 times.

It is hard to believe that the Kuiper Belt has been officially discovered only 25 years ago. Astrophysicists suspected its existence, as it would have explained the short-period comets, such as Halley's Comet: passing close to the Sun they lose a lot of their material, so they need to replenish it somewhere regularly. The period length excludes a possibility of a comet returning to the Oorth's Cloud (a hypothetical sphere of comets surrounding the Solar System at 50 000 a.u. distance, whose existence we haven't confirmed by observations yet), so it has to collect the matter from somewhere much closer. In 1992, David Jewitt and Jane Luu announced the "Discovery of the candidate Kuiper belt object". Futher observations made evidence for the Kuiper Belt existence only stronger, and nowadays we know that the Belt consists of hundreds of thousands objects ranging in size and composition.

Given the timing, Voyagers and Pioneers have passed through the Kuiper's Belt without registering any of its content, because back in those days we didn't really know that there was anything worth to look at.

A small world from the icy bodies zone, MU69 is quite mysterious. All we know about it comes from the Hubble and Gaia (ESA orbit telescope) observations, and a detailed study by the "New Horizons" team done last year in one of Patagonia's observatories. The latter data were collected from the so-called "occultation" event when the MU69 passed between the Earth and a star.

The combined data suggest that the MU69 is either "an extreme prolate spheroid", or a binary object. It is a rock under 30 km in first case, or a pair of 15-20 km-large bodies otherwise.

"New Horizons" will approach MU69 as close as 3500 km: three times closer than Pluto. Thanks to that the apparatus' cameras will be able to capture detailed images of the object.

Right now, the probe is hibernating. It will "wake up" on the 4^th of July to run a check on its equipment and in mid-August "New Horizons" will start to approach the MU69 and make first observation attempts to give the team more data to control the fly-by.

If anything, this is a worthy occasion to look forward to a new year again!