Beyond Pluto: Nasa craft to zip past farthest world explored by humankind

CAPE CANAVERAL, Florida—The spacecraft team that brought us close-ups of Pluto will ring in the new year by exploring an even more distant and mysterious world.

Nasa’s New Horizons spacecraft will zip past the scrawny, icy object nicknamed Ultima Thule (TOO-lee) soon after the stroke of midnight.

Ultima Thule, 1.6 billion kilometers beyond Pluto and an astounding 6.4 billion km from Earth, will be the farthest world ever explored by humankind.

That’s what makes this deep-freeze target so enticing; it’s a preserved relic dating all the way back to our solar system’s origin 4.5 billion years ago. No spacecraft has visited anything so primitive.

“What could be more exciting than that?” said project scientist Hal Weaver of Johns Hopkins University, part of the New Horizons team.

Scientists speculate Ultima Thule could be two objects closely orbiting one another. If a solo act, it’s likely 32 km long at most. Envision a baked potato. “Cucumber, whatever. Pick your favorite vegetable,” said astronomer Carey Lisse of Johns Hopkins.

It could even be two bodies connected by a neck. If twins, each could be 15 km to 20 km in diameter.

Riskier rendezvous

Lead scientist Alan Stern of Southwest Research Institute in Boulder, Colorado, expects the New Year’s encounter to be riskier and more difficult than the rendezvous with Pluto: The spacecraft is older, the target is smaller, the flyby is closer and the distance from us is greater.

Nasa launched the spacecraft in 2006; it’s about the size of a baby grand piano. It flew past Pluto in 2015, providing the first close-up views of the dwarf planet. With the wildly successful flyby behind them, mission planners won an extension from Nasa and set their sights on a destination deep inside the Kuiper Belt.

As distant as it is, Pluto is barely in the Kuiper Belt, the so-called Twilight Zone stretching beyond Neptune. Ultima Thule is in the Twilight Zone’s heart.

This Kuiper Belt object was discovered by the Hubble Space Telescope in 2014. Officially known as 2014 MU69, it got the nickname Ultima Thule in an online vote.

Most northernmost place

In classic and medieval literature, Thule was the most distant, northernmost place beyond the known world. When New Horizons first glimpsed the rocky iceball in August it was just a dot. Good close-up pictures should be available the day after the flyby.

New Horizons will make its closest approach in the wee hours of Jan. 1, 12:33 a.m. EST. The spacecraft will zoom within 3,500 km of Ultima Thule, its seven science instruments going full blast.

The coast should be clear: Scientists have yet to find any rings or moons around it that could batter the spacecraft. New Horizons hurtles through space at 50,700 kph, and even something as minuscule as a grain of rice could demolish it.

“There’s some danger and some suspense,’’ Stern said at a fall meeting of astronomers. It will take about 10 hours to get confirmation that the spacecraft completed and survived the encounter. —AP