Ultima Thule Isn't Snowman-Shaped, "Wonderfully Puzzling" Discovery Reveals

Since NASA’s New Horizons probe flew by Ultima Thule on New Year’s Eve to the sweet soundtrack of Queen’s Brian May, we’ve learned a lot more about the distant object that dwells beyond the orbit of Neptune. In January, NASA photos revealed it was shaped like a snowman, formed from two space rocks jammed together. But as newer images of the object, which is roughly 4 billion miles from the sun, have trickled in over the past few weeks, project scientists have realized that it’s actually flat.

As NASA revealed on Friday, the larger of the two objects, Ultima, is shaped like a “pancake,” and the second, Thule, is more like a “dented walnut.” Although NASA scientists were very wrong about the snowman shape, Alan Stern, Ph.D., the principal investigator on the New Horizons mission, tells Inverse that the team shook it off and took the new information pretty well:

“It was greeted by the sheer joy of scientific discovery of something that was simultaneously unexpected and wonderfully puzzling about the earliest stages of planet formation,” Stern says.

From the first batch of New Horizons pictures sent home in early January, project scientists learned that Ultima Thule is actually red and that it comprises a “contact-binary,” which means that its two lobes gently collided and have been together ever since. This discovery led to the “snowman” (or BB-8) comparison, which Stern says was not actually confirmed. The new, “so-called ‘pancake shape,’” he adds, was “strongly indicated from approach images.”

The new images from which the team gleaned their new conclusion were actually taken as New Horizons departed from Ultima Thule at 31,000 miles per hour, nearly ten minutes after it reached its closest point. When the images were stitched together, project scientists saw how much of the background starlight was blocked by the object. The way that starlight reflected around Ultima Thule’s top crest (seen in the header video) suggests that the object isn’t round but instead is pancake-shaped.

Although it might seem strange to get hung up on the shape of an object billions of miles away, Stern added in a release that “we’ve never seen something like this orbiting the Sun.” Going forward, he adds that the strange new shape actually implies that angular momentum — the type of force generated by rotational motion — may have played a greater role in shaping the objects in the early solar system.

“Ultima Thule is a well preserved relic of solar system formation,” he says. “Its shape may indicate that angular momentum played a larger role the individual planetesimal formation environment than previously appreciated.”

Stern and the team at New Horizons are now focusing on figuring out exactly how all the forces on our young solar system came together to create this flat, double-lobed object out in the Kuiper belt. Ultima Thule may not be as photogenic as the cosmic snowman, but its even stranger shape might be even more meaningful in our quest to understand the solar system’s origins.