A billion miles behind Pluto, in the farthest corners of the solar system, is an object called Ultima Thule. Its name means "outside the known world."
Although scientists discovered this with telescopes, they know little about it. What they understood from their observations is that Ultima Thule is a stone in the Kuiper belt of the solar system, a region outside of Neptune. It is irregularly shaped and about 18 miles across. It might look like two potatoes that were squeezed together, like this:
On January 1, the New Horizons spacecraft, known to fly on Pluto, will pass by the Ultima Thule to explore this strange rock and try to learn more about the very formation of our solar system.
After the New Horizons flew past Pluto in 2015, the scientists of his mission chose Ultima Thule as their next stop in the Kuiper belt, mainly because the New Horizons were able to reach it with the remaining fuel.
But the New Year's span is important because Ultima will be the farthest object in the solar system ever investigated by mankind, and one of the most primitive.
Since Ultima is located in such a cold, remote and quiet area of the solar system, it probably revolved around the sun almost unchanged throughout almost the entire age of the solar system.
“We expect Ultima to be the best-preserved specimen of a planetary building block ever investigated,” writes Alan Stern, lead researcher at New Horizons, in his blog. “What will Ultima show? Nobody knows. For me, this is the most exciting – pure intelligence and fundamental science! "
For Stern, the fly-around — and the images that come from it — will be similar to the famous “Sunrise of the Earth” photograph taken by the Apollo 8 mission 50 years ago. This photo was taken for the first time when people rotated around the moon. It was the first time we saw our own planet from the point of view of another world.
"For all these years between the study of Apollo 8 in December and our NASA made history, exploring further and further," writes Stern. “As a result, we made the prediction of Karl Sagan that in just one or two generations the planets would turn from points of light into real and explored worlds.
At the moment, the Ultima Thule is still just a point of light. This is how it looks from the New Horizons camera when the spacecraft is getting closer and closer.
But soon it will be much more than a point of light. Object images may be dimmer than Pluto’s (this billion miles farther from the sun). But New Horizons has a camera that can see the amazing subtle details. Just look at the images he made with Pluto.
Recall that Pluto was also just a point of light. New Horizons have shown that this is an incredible, dynamic world with a beautiful ice plane in the shape of a heart. This GIF shows the best image of Pluto, which we in 2015 turned into what New Horizons saw on its historic span. It turned from a dirty spot into a beautiful one.
(And yes, scientists are still debating whether Pluto deserves a planet for a dwarf planet).
New Horizons will pass by Ultima Thule around 12:33 pm East on January 1, immediately after the beginning of the New Year. You can follow along with NASA on a live NASA television broadcast (see below). New Horizons will also carry messages from the public (submissions ended December 21) to celebrate the massive arrival.