Planetary Sciences News

New Horizons Spacecraft to Reach Farthest Body in Solar System Yet

The flyby of Ultima Thule on New Year’s Day will give us our first glimpse of a mysterious Kuiper Belt object.


This New Year’s Day, NASA’s New Horizons spacecraft will make the most distant flyby in the solar system to date. The spacecraft, traveling at over 14 kilometers per second, will soar just 3,500 kilometers from the surface of an icy, rocky object nicknamed Ultima Thule perched in the outer reaches of the solar system. The flyby is an extension of the mission that flew by Pluto in 2015 and marks the continuation of NASA’s exploration into the cold and dark Kuiper Belt, suspected to be the rocky remnants leftover from the solar system’s formation.

New Horizons launched in 2006 on a fast track to explore Pluto. The spacecraft zipped by the dwarf planet nearly a decade later, and the encounter revealed among its many observations surprisingly active geological features and curious interactions with solar wind. With the mission to Pluto complete and fuel to spare, NASA set its sights farther into the Kuiper Belt, which is considered the solar system’s “third zone” beyond the inner rocky planets and outer gas planets.

The spacecraft has now traveled 1.6 billion kilometers beyond Pluto, on track to make its closest approach to Ultima Thule at 12:33 a.m. Eastern Standard Time on 1 January 2019. New Horizons will have its scientific instruments pointing toward the object, measuring its color, composition, thermal signature, and other properties. Scientists know very little about Kuiper Belt objects, making the flyby a landmark moment.

“We’re going to an entirely new type of world, something formed much further out than anything we have ever explored,” said Alan Stern, mission principal investigator, in a press conference last October.

Ultima Thule has been in a “deep freeze” in the outer edges of the solar system for about 4.5 billion years, explained Stern. Studying its properties could help scientists understand the earliest stages of our solar system. Even comets, which can form farther out than Ultima Thule, are warmed by repeated passes by the Sun and may have “significantly evolved from their primordial state,” said Stern. “Ultima is going to be something different all together,” he added.

The distances between objects in our solar system
The distances between objects in our solar system, stretching from the Sun to Ultima Thule some 43 astronomical units (AU) away. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Scientists are looking forward to their first up close glimpse at a Kuiper Belt object and already have some mysteries to unravel. It is unclear whether the object is made of one or two main bodies and why its light curve seems unusually low. Stern said that scientists will know the answer to these questions in just a few days’ time.

Mission operations aren’t affected by the partial government shutdown and, earlier today, NASA announced that its social media and television teams will be able to cover the flyby event. Tune in to live coverage from mission headquarters at Johns Hopkins University’s Applied Physics Laboratory (APL) in Baltimore, Md., where the New Horizon’s science team will hold a discussion when the first signal arrives back from Ultima Thule on New Year’s Day from 10:00 to 11:00 a.m. Eastern Standard Time.

You can also follow along on social media using #UltimaFlyBy and #UltimaThule and with our team at AGU, who will be at APL during the flyby, on Twitter and Instagram. Stern plans to live tweet from his personal account, @AlanStern, and the mission account, @NewHorizons2015. Researchers hope to have the first close-up images of Ultima Thule as early as the afternoon of 1 January.

—Jenessa Duncombe (@jenessaduncombe), News Writing and Production Intern

Citation: Duncombe, J. (2018), New Horizons spacecraft to reach farthest body in solar system yet, Eos, 99, Published on 28 December 2018.
Text © 2018. The authors. CC BY-NC-ND 3.0
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