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So long, snowman: Ultima Thule is flatter than we thought

A new set of images beamed back from the New Horizons spacecraft reveals the unusual “pancake”-like shape of this Kuiper Belt Object.

ByKatherine J. WuNOVA NextNOVA Next
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Ultima Thule was once thought to be composed of two spherical objects barely touching. New data now reveals that the two lobes are flatter than once believed. Nothing is completely definitive, though: The dashed blue lines span a region of uncertainty, indicating that Ultima Thule could be even flatter than, or not as flat as, this rendering. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

If you believe the lore of Punxsutawney Phil, spring is just around the corner—which means it’ll soon be curtains for snowmen in the northern hemisphere. And, apparently, elsewhere in our solar system.

Ultima Thule the snowman is no more, according to a Johns Hopkins University Applied Physics Laboratory press release published Friday.

The 19-mile-long, bilobed space nugget, whose official name is 2014 MU69, orbits the Sun about 1 billion miles past Pluto. Scientists interpreted the first images of the Kuiper Belt Object, snapped some 4 billion miles from Earth, as featuring two lip-locked spherical lobes. But new data, captured by the New Horizons spacecraft about 10 minutes after its moment of closest approach to Ultima Thule on January 1, reveal a more “pancake”-like visage, New Horizons principal investigator Alan Stern said in a statement.

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By analyzing how Ultima Thule blocks out the light of surrounding stars, scientists outlined its shape in multiple dimensions. As it turns out, both the large and small halves of the object (nicknamed “Ultima” and “Thule,” respectively) aren’t the orbs they were thought to be. Instead, they’re shaped like smashed-down bits of dough.


Left: An "average" of ten images taken by New Horizons of Ultima Thule on January 1, shortly after the moment of closest approach. Right: The same image, processed to yield a sharper, brighter view of the Kuiper Belt Object. Image Credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute/National Optical Astronomy Observatory

“We had an impression of Ultima Thule based on the limited number of images returned in the days around the flyby, but seeing more data has significantly changed our view,” Stern said. “The new images are creating scientific puzzles about how such an object could even be formed. We've never seen something like this orbiting the sun.”

The New Horizons spacecraft, launched in 2006, initially set out to explore the then-planet Pluto. After the probe successfully conducted a flyby of Pluto in 2015, the mission was extended in hopes that New Horizons might find clues about origins of the Solar System deep in the Kuiper Belt, which lies beyond the orbit of Neptune.

Researchers believe that, in this cold, distant region of the Solar System, there are still preserved prototypes of the raw materials that came together to form the planetary bodies we know and love (including our own Earth) billions of years ago. Ultima Thule may very well be one of them—which means every bit of new information on this mysterious object could be crucial.

It’s unclear what exactly this means for interpreting how the planets came together, but there’s still more data to come. A steady stream of information will be beamed back in our direction from the probe through the summer of 2020.

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