Exploring the most far away world
Marcia Dunn
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 on New Year’s Day.
An astounding 6.4 billion km from Earth, Ultima Thule will be the farthest world ever explored by humankind. That’s what makes this deepfreeze 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.
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.
New Horizons
Nasa launched the spacecraft, about the size of a baby grand piano, in 2006. It flew past Pluto in 2015, providing the first close-up views of the dwarf planet. Mission planners 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.
Ultima Thule
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. 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.
Are we there yet?
New Horizons will make its closest approach on January 1 at 6.33pm NZT. The spacecraft will zoom within 3500km of Ultima Thule, its seven science instruments going full blast. Scientists have yet to find any rings or moons around it that could batter the spacecraft. New Horizons hurtles through space at 50,700 km/h, and even something as minuscule as a grain of rice could demolish it. It will take about 10 hours to get confirmation that the spacecraft completed — and survived — the encounter.
Possibly twins
Scientists speculate Ultima Thule could be two objects closely orbiting one another. If a solo act, it’s likely 32km long at most. If twins, each could be 15 to 20km in diameter.
Mapping misson
Scientists will map Ultima Thule every possible way. They anticipate impact craters, possibly also pits and sinkholes, but its surface also could prove to be smooth. As for colour, Ultima Thule should be darker than coal, burned by eons of cosmic rays, with a reddish hue.
What’s next
It will take almost two years for New Horizons to beam back all its data on Ultima Thule. A flyby of an even more distant world could be in the offing, if Nasa approves another mission extension and the craft remains healthy. At the very least, New Horizons will continue to observe objects from afar in the Kuiper Belt.