NASA's New Horizons to Show First Close-Up View of Distant Reaches of Solar System

New Horizons at Pluto Artist Concep NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Ultima Thule is a speck in the cosmos, barely 20 miles wide, that orbits our sun a billion miles past Pluto. It is so small and distant that it cannot be seen from Earth, even with the most powerful ground-based telescopes. To find it, astronomers had to use the Hubble Space Telescope, which sits above the Earth's atmosphere—and even then, it appeared only as a faint dot. Astronomers named it with an ancient Greek phrase that refers to a distant place far to the north, beyond what is known.

Shortly after midnight on New Year's Day 2019, New Horizons—a spacecraft the size of a grand piano—will arrive at Ultima Thule. After exploring Pluto four years ago, it entered a strange, uncharted territory known as the Kuiper belt. It is home to trillions of "objects" that, like Ultima Thule, have gone undisturbed since the birth of the solar system. New Horizons will come within 2,200 miles of this pristine cosmic fossil, the first probe to do so.

The spacecraft is the brainchild of Alan Stern, principal investigator of the Southwest Research Institute in Boulder, Colorado. Newsweek spoke to Stern about what the mission means for science. "This is the most distant exploration of any world in history," he says. "We are the Lewis and Clark of our era."

How would you describe the Kuiper belt?

It's extremely cold, which means things are very well preserved. We have primordial planetary bodies in essentially mummified form, preserved in a crypt created by cold temperatures. It's a perfect place for what I call an archaeological dig into the history of our solar system and planet formation.

Why did you pick this object?

Because it required the least amount of fuel to reach, and we could get there soonest. That leaves enough fuel left in the tank for another flyby in future years.

How dark is it out there?

Pluto receives 1,000 times less light than Earth on a sunny day. Ultima Thule receives only half that.

What's it like planning this flyby versus the Pluto flyby?

This was much tougher. New Horizons is older, the power levels and lighting levels are much lower, and the target is much smaller and harder to navigate to. We don't know that much about [Ultima Thule]. We have to plan with our eyes wide open, not knowing specific things to look for while trying to cover all the possible bases.

Any guesses as to what Ultima Thule looks like?

It was forged out of the bedrock from which planets formed 4 billion years ago. It's wilder and more pristine than anything we've ever been to—by a lot. When we get there, we'll find out. That's part of the fun!