by William J. Bechaver

It’s been nearly two and a half years since I’ve updated us on the amazing New Horizons mission, back on 4 August 2016.

Back then, the tiny spacecraft had flown a year past Pluto, and scientists had just determined its next target, the very distant Kuiper Belt object 2014 MU69, now named Ultima Thule.

New Horizon was launched way back in January of 2006. Ultima Thule wasn’t even discovered until eight years after the launch.

When New Horizons flew past Pluto in the summer of 2015, they had not yet determined the spacecraft’s next target. A year later, when the target was determined and identified, I wrote that New Horizons wouldn’t reach the determined target until January of 2019.

Well, last week, New Horizons reached its destination. The spacecraft is now an astounding billion miles beyond Pluto. Traveling at about 18 times faster than the speed of a rifle bullet, it took it an amazing three and a half years to reach the next object.

As it happens, this week Pluto is directly opposite the Sun from Earth, at a position furthest from Earth on the far side of the solar system. It is over three billion, two hundred million miles distant.

Ultima Thule is at a distance of four billion, a hundred million miles away, and a billion miles from Pluto. A radio signal sent to the New Horizons spacecraft takes more than six hours to reach it from Earth, traveling at the speed of light.

What’s more, Ultima Thule is very tiny. It is only about nineteen miles across. Flying past the small object at such an incredible distance, at such an astounding speed, takes very precise calculations. To make course corrections in the flight path is nearly impossible. They had to get it right from the beginning, more than two years ago.

Ultima Thule was chosen not for its prominence in the Kuiper Belt. It was chosen as a target for its position in space. It was the only object that was within reach following the Pluto flyby in 2015, using minimal fuel for course adjustments after that encounter.

The Kuiper Belt is an area of space at the outer reaches of our solar system. It contains millions of objects, many more than The Asteroid Belt between Mars and Jupiter. But at such a great distance, it is a very vast area of space, and the objects are a billion miles apart, and many are only twenty miles across, or smaller.

The Kuiper Belt is the area of space lying just beyond the orbit of Neptune, and stretching far out beyond the furthest orbit of Pluto. It is an area twenty times wider than The Asteroid Belt. Many of the objects in The Kuiper Belt are considered Trans-Neptunian in nature, because their orbits actually cross that of Neptune.

The Kuiper Belt is also the home to many smaller planets, dwarf-planets, minor-planets, and planetoids, Pluto being the most famous and notable, with it’s five known moons. Pluto was the first to be discovered, and the first to be named. There are four other bodies out there with moons of their own, so Pluto is not unique in that distant region of space. Three of them are named Haumea, Quaoar, and Orcus. Other minor-planets have been identified in the region, including Makemake, Sedna, and one which hasn’t been named yet, currently being distinguished by the year of its discovery, as 2007 OR10. Ultima Thule was merely known as 2014 MU69, until it was chosen as a flyby target, and then tentatively named.

If you have never heard of any of these distant worlds, you are not alone. Casual observers are unaware that these objects are out there, because it is impossible to observe them with the naked eye, and even through the most powerful telescopes available to man, they are merely distant, faded points of light.

The most remarkable object out there, far beyond even Pluto, and sometimes beyond the reaches of The Kuiper Belt, is Eris. Eris is the most massive known object of the region. It is about the size of Pluto, but currently is far more distant. It is nearly three times more distant from the sun than is Pluto. It takes the light of the sun 5 hours to reach Pluto and 13 hours 30 minutes to reach Eris. Since it took us 9 years to reach Pluto using our latest and fastest technology in space travel, and another three to reach the next closest object, it would take us nearly 25 years to reach Eris. If we had our fastest probe ready to launch tomorrow, it would not arrive at Eris until the year 2044. No such mission is planned, and Eris most likely will remain out of reach for a long time.

On January first, New Horizons finally reached Ultima Thule. It sent back its first pictures, the signal taking six hours to reach us before we would know if the tiny spacecraft had hit its mark, and the mission was a success.

It is by far the most distant object NASA has flown past. It is the most distant object photographed up close, and the most remote body in the solar system we have had the opportunity to investigate. It is a remnant left over from the origin of our solar system, and the secrets it holds could reveal how our solar system formed over four billion years ago.

The pictures it has sent back so far are amazing. They show a tiny, binary world, like a giant icy snowman in space. It will take about eight months for the spacecraft to send back all the data it collected during the momentary flyby on New Year’s Day. During that time, we will come to know Ultima Thule better than we have known any other such object in our solar system.

What’s next for New Horizons. As it sends back the files of data it has collected, it continues to travel ever outwards and grows ever more distant. It’s primary mission now complete, it will continue on, and eventually follow its ancestors Voyager I and Voyager II, leaving the solar system and entering interstellar space. It has enough fuel to continue to send back a signal for at least twenty years.

Thanks for the positive feedback about our featured columns, and your continued interest in astronomy. If you have any questions or article requests, contact us at, or follow us on Twitter @ColoSpacEScapE for updates and additional viewing opportunities.
• · William J. Bechaver is the director of SPACE • Spanish Peaks Amateur Cosmos Enthusiasts, the premier Astronomical Society for Southern Colorado and Northern New Mexico.

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Ultima Thule as first photographed by NASA’s New Horizons spacecraft.


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