NASA’s uncrewed New Horizons probe flew past Pluto, its primary target, in 2015, but its mission is far from over. Soon it will continue on through the Kuiper Belt, and just after midnight on January 1, 2019, New Horizons will perform a flyby of Ultima Thule. The name may sound like a dragon spell from Skyrim or the name of a kindly Norwegian innkeeper, but it’s actually the common name of Kuiper Belt object KBO 2014 MU69, which floats out in space beyond the edges of our solar system. It’s among a class of objects believed to be cosmic leftovers from the early times of planetary formation billions of years ago.

In a live NASA Science Chat on Wednesday, three of the top New Horizons team members explained the plan for the 2019 flyby, which, at a billion miles beyond Pluto, will be the most distant planetary flyby in human history. Given this fact, KBO 2014 MU69’s name is especially fitting, as Ultima Thule is a medieval phrase that means “beyond the known world.” But New Horizons is going to make it part of our known world.

“We’re gonna zoom right up to it, image it, find out what it’s made of, find out if it has moons or rings, and lots more about it,” Alan Stern, the New Horizons principal investigator, told viewers.

What we do know about Ultima Thule is that it’s about 23 miles across and approximately 10 times the size of an average comet. We also know its trajectory, which makes it the perfect candidate for New Horizons’ secondary mission objective.

Despite its status as a secondary mission, though, the Ultima Thule flyby is taking a good deal of prep. When the Earth-based team woke the probe back up in June, they did system checks and performed system updates to support the flyby, Alice Bowman, the New Horizons mission operations manager, told viewers on Wednesday.

“In August, we transitioned the spacecraft into a mode where we could take pictures, so we are taking pictures now of Ultima Thule,” said Bowman. “We call those optical navigation measurements, and we are using those to target the object.” The image below is an example of one such optical navigation measurement.

Left: Composite image taken by New Horizons showing the estimated range of Ultima Thule in the yellow box. Right: A zoomed-in image of the area inside the yellow box, showing Ultima Thule where scientists predicted it would be.
Left: Composite image taken by New Horizons showing the estimated range of Ultima Thule in the yellow box. Right: A zoomed-in image of the area inside the yellow box, showing Ultima Thule where scientists predicted it would be.

By tracking Ultima Thule, which was only discovered in 2014, scientists have been able to identify it as a classical Kuiper Belt object, which means it’s likely one of the oldest objects in our solar system. But because it is a poorly understood object, scientists need to keep monitoring it to make sure it moves as they expect.

Researchers need to know exactly where Ultima Thule is to get as close as they want. The New Horizons team plans to fly the New Horizons probe 2,200 miles from Ultima Thule, much closer than the 7,800 miles that separated it from Pluto in 2015. Most importantly, though, the simple fact is that we know very little about Ultima Thule, and this flyby will give us some of the first facts about the ancient object.

“This has all the elements of an unbelievable set of discoveries that are just outside our reach at the moment but will come into view soon,” Jim Green, NASA’s chief scientist, told viewers on Wednesday. “We know we’re gonna flyby January first, that’s a given. It has the excitement of what are we gonna see?

Unfortunately, it’ll take quite some time before we find out what New Horizons sees. When the probe performs its epic flyby, it will begin sending its data back to Earth, but with the spacecraft sending a low-powered signal over 4 billion miles, the data won’t reach Earth for about a year. It’ll surely be worth the wait, though, to glimpse an object that may be even older than Earth.

Photos via NASA/JHUAPL/SwRI, NASA