NASA’s New Horizons probe is exploring the furthest regions of our Solar System and will be making a very special visit on New Year’s Day 2019, when it will buzz an object unofficially called Ultima Thule, also known as Kuiper Belt object 2014 MU69. Sitting 4.1 billion miles (6.6 billion kilometers) from Earth, Ultima Thule will be the most distant object ever explored by a spacecraft, and scientists believe it can provide information on the formation of the early Solar System.
The New Horizons probe was launched in January 2006 and has been making its way through the Solar System since then. It got a gravity boost when it passed Jupiter in February 2007, then spent six months gathering data from Pluto and its moons in summer 2015. Then it headed out into the Kuiper Belt to examine the cold, icy objects in the belt beyond Neptune.
The probe will pass Ultima Thule at 12:33 a.m. EST on January 1, 2019. To watch the Ultima Thule flyby live, you can tune into the NASA TV YouTube channel where there will be a briefing and panel discussion about the flyby on December 31 and a live steam of the signal acquisition from New Horizons on January 1. For mission status updates, you can follow the New Horizons twitter account, and for more details about the live TV events you can see the NASA Live website.
The Ultima Thule flyby is much more technically demanding than the flyby of Pluto due to the extra distance from Earth. This means that there are many more unknowns involved: the exact position of the object and the potential existence of nearby moons or other environmental hazards are unknown, and there are lower levels of light and longer communication times with the probe, all of which add to the challenge.
NASA scientists have already noticed something unexpected about Ultima Thule. They have known since 2017 that the object is not spherical — it is probably an elongated shape, or could even be two objects moving close together — but it does not give off the pulsing variation in brightness that would be expected for an object of that shape. The “light curve” is a period variation in brightness during each rotation of an object, and Ultima Thule’s light curve is unexpectedly small.
“We’ll get to the bottom of this puzzle soon,” Dr. Alan Stern, principle investigator of the New Horizons mission, said. “New Horizons will swoop over Ultima and take high-resolution images on December 31 and January 1, and the first of those images will be available on Earth just a day later. When we see those high-resolution images, we’ll know the answer to Ultima’s vexing, first puzzle. Stay tuned!”
Updated December 30, 2018 with information about how to watch the flyby.