One billion miles after Pluto, at the edge of the solar system, is an object called Ultima Thule. His name means "beyond the known world."
Although scientists have detected with telescopes, they do not know much about it. What they got from their observations is that Ultima Thule is a rock in the Kuiper belt of the solar system, the area beyond Neptune. It is irregular and is about 18 miles across. It may look like two potatoes that have been put together, like this:
On January 1, the New Horizons spacecraft, famous for flying through Pluto, will travel through Ultima Thule to explore this strange rock and try to learn more about the formation of our solar system.
After New Horizons passed Pluto in 2015, its missionary scientists chose Ultima Thule as their next stop in the Kuiper belt, mainly because New Horizons had the ability to catch up with its remaining fuel.
But the New Year's flight is significant because Ultima will be the farthest object of the solar system that humanity has ever explored, and one of the most primitive.
Because Ultima is in such a cold, remote, and silent region of the solar system, it is probably orbiting the sun for almost the entire age of the solar system.
"We hope Ultima is the best preserved sample of a planetary building block ever explored," writes Alan Stern, New Horizons' principal investigator, in a blog post. "What will Ultima reveal? Nobody knows. To me, this is the most exciting – this is pure exploration and fundamental science! "
For Stern, the overfly – and the images that come from it – will be similar to the famous "Earthrise" photo taken by the Apollo 8 mission 50 years ago. This photo was taken during the first time humans orbited the moon. It was the first time we saw our own planet from the perspective of another world.
"Throughout all these years between the exploration of Apollo 8 in December and ours, NASA has made history exploring ever further," Stern writes. "As a result, we made Carl Sagan's prediction that in just a generation or two the planets would be transformed from points of light into real and exploited worlds."
For now, Ultima Thule is still only a spot of light. See how the New Horizons camera looks, as the spacecraft gets closer and closer.
But soon it will be much more than a spot of light. The images of the object may be weaker than those of Pluto (it is a billion miles farther from the sun). But the New Horizons has a camera that can distinguish delicate and impressive details. Just look at the pictures he took of Pluto.
Remember that Pluto used to be just a point of light as well. New Horizons has revealed that it is an incredible and dynamic world with a beautiful icy plane in the shape of a heart. This GIF shows the best picture of Pluto we had to turn 2015 into what New Horizons saw in its historic flyby. It went from a blur to a thing of beauty.
(And yes, scientists are still debating whether Pluto deserves to be designated as a planet instead of a dwarf planet.)
New Horizons will pass through Ultima Thule around 12:33 Eastern on January 1, shortly after the start of the New Year. You can follow NASA on the live broadcast of NASA TV (see below). New Horizons will also be taking messages from the public (entries end on December 21) to celebrate the distant arrival.