NASA’s New Horizons spacecraft, known for flying by Pluto in 2015, has finally spotted its next target at the edge of the Solar System. On August 16th, the distant probe captured its first images of the space rock it’s currently zooming toward — an icy body nearly 20 miles across that’s been nicknamed Ultima Thule. It’s a major milestone for the New Horizons team as they prepare the spacecraft for its rendezvous with Ultima Thule on New Year’s Day 2019.
The New Horizons spacecraft has been en route to Ultima Thule ever since October 2015, just a few months after it flew by Pluto in July. Following the Pluto meet-up, NASA decided to extend the New Horizons mission so that the vehicle would fly by another target in the distant Solar System. The mission team selected Ultima Thule, also named 2014 MU69, since it’s in an ideal position beyond Pluto, and it didn’t take too much fuel for New Horizons to change course to meet up with the rock.
Planetary scientists are especially eager for the spacecraft to visit Ultima Thule since it’s an object in the Kuiper Belt — the huge cloud of icy rocks that orbits beyond Neptune. Scientists believe that objects in the Kuiper Belt haven’t changed very much since the birth of the Solar System. So these bodies are considered very primitive and could tell us more about what the early days of our cosmic neighborhood were like. Plus, we’ve never visited one of these objects before, so no one truly knows what to expect.
Up until now, scientists have only been able to image Ultima Thule directly using the Hubble Space Telescope. And the images haven’t been that great since the icy body is small and orbits approximately 4 billion miles from Earth. To get a better understanding of what Ultima Thule looks like, the New Horizons team has also tried spotting the rock a few times from Earth as it passed in front of distant stars, blocking out their light. These eclipsing events, known as occultations, have allowed the mission scientists to better understand the true shape and size of the object. It turns out that Ultima Thule may be pretty weird, too. The rock is either oddly shaped, like two meatballs stuck together, or it’s not one rock but rather two boulders closely orbiting around each other.
We still don’t know for sure, and the new images from New Horizons don’t give us much more clarity. Right now, Ultima Thule still appears as just a light speck in the New Horizons images, since the vehicle is about 100 million miles away from the object. The rock is also particularly hard to find as Ultima Thule was photographed against an incredibly bright field of stars, making it hard to see the faint, tiny object.
“It really is like finding a needle in a haystack,” Hal Weaver, a New Horizons project scientist, said in a statement. “In these first images, Ultima appears only as a bump on the side of a background star that’s roughly 17 times brighter, but Ultima will be getting brighter – and easier to see – as the spacecraft gets closer.”
New Horizons is currently hurtling toward Ultima Thule at a speed of more than 31,000 miles per hour, and it’s scheduled to fly by the rock at 12:33AM ET on January 1st, 2019. The spacecraft will continue to take pictures of the object until then, which will help the mission team refine the vehicle’s trajectory. But just seeing Ultima Thule now, even as a blurry speck, is good news because it means that the object was right where scientists expected it to be.
The New Horizons images were taken around the same time that another NASA spacecraft, OSIRIS-REx, also spotted its celestial target for the first time. That vehicle is currently on its way to an asteroid named Bennu in order to grab a sample from the rock’s surface and bring it back to Earth. OSIRIS-REx also has a big milestone coming up around the same time as the Ultima Thule flyby: on December 31st, OSIRIS-REx will insert itself into orbit around Bennu, which will be the start of a year-long mapping campaign to figure out the best place to grab a sample from the asteroid’s surface.
Just four months remain until New Horizons and OSIRIS-REx get up-close views of their deep space destinations. NASA will have a lot of missions to help ring in the new year.