Mohawk Valley Astronomical Society

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The Red Peanut

by Perry Pezzolanella

New Horizons made history during July 2015 when it became the first spacecraft to fly past Pluto, revealing a world of flowing glaciers, towering mountains, organic snow, dunes, and wispy hazes. With the primary mission of exploring Pluto behind it, New Horizons continues onward into the depths of space to fulfill its second goal, to encounter an ancient relic of the Solar System, a distant Kuiperoid.

It was not a sure bet when New Horizons was launched on January 19, 2006 because there was no Kuiperoid in a favorable location where it could readily be approached after the Pluto flyby. The search for one with the Hubble Space Telescope seemed futile, but one had to be found before New Horizons flew past Pluto so it could be properly retargeted. The search finally paid off on June 26, 2014 when a tiny world, hardly 20 miles across, was discovered about one billion miles beyond Pluto. This small Kuiperoid takes about 296 years to orbit once around the Sun and shines faintly at magnitude +27. It was a lucky search because it is within reach of the New Horizons spacecraft, which will be able to fly past it on January 1, 2019, hardly a half hour after the ball drops at Times Square. It will not be a long wait like the 9.5-year flight from Earth to Pluto, and serendipitously, it is turning out to be a very interesting world.

This Kuiperoid, known as 2014 MU69, is informally called Ultima Thule, pronounced “ultima toolee”, which is a Latin phrase for “beyond the farthest frontiers”. It is a very strange world unlike any other world visited so far by spacecraft. It is deeply reddish, which means it is carbon-rich, coated with organic compounds, and very ancient. Having been bombarded by ultraviolet radiation through the eons, it is most likely a true relic of the early Solar System. Occultations of stars from Earth on June 10 and July 17, 2017 revealed a strange shape for Ultima Thule. It appears to be bi-lobed, meaning it is two objects that are in close orbit with each other or barely touching, a contact binary. If they are touching, Ultima Thule could look like a reddish peanut. Even better, one of the occultations revealed the possibility of a tiny moon. If confirmed, it is hardly more than three miles across orbiting about 150-200 miles from Ultima Thule, taking about 2 to 3 weeks to orbit. This could make for an interesting flyby. Imagine a reddened, cratered peanut with a tiny moon next to it!

Mission planners will be hard at work to get the most out of New Horizons’ flyby as there is only one chance to do it right since there are no other Kuiperoids known that can be encountered after Ultima Thule. New Horizons will break its own long distance record it set at Pluto when it flies past Ultima Thule for the furthest encounter of any world at 4.03 billion miles. Radio signals will take nearly six hours one way from Earth to Ultima Thule at the speed of light and a round trip is about 12 hours. Help in fixing a problem will take too long near encounter time, therefore everything must work, and New Horizons has already proven it can deliver when it has a difficult task to perform.

New Horizons is currently scheduled to fly within 2175 miles from Ultima Thule on January 1, 2019 at 12:33 A.M. EST. It will make detailed measurements of its size, mass, composition, and look for any signs of a coma to determine if it is cometary. New Horizons will be looking for additional moons before the encounter to avoid any risk of collision as even a dust particle at nearly 32,000 miles per hour would be fatal. It is uncertain if New Horizons will encounter any other Kuiperoids beyond Ultima Thule. It will continue to relay its data from the Ultima Thule encounter into 2020 and monitor its environment through 2021. It may last well into the 2030s. Eventually, Ultima Thule will be given a new, formal name, once its characteristics and properties become known. No matter what happens, New Horizons will go down in history as a prolific spacecraft that broadened our knowledge of Pluto and the Kuiper Belt.