Ultima Thule is like a pancake, NASA's New Horizons unveils the unique shape

NASA’s New Horizons spacecraft has beamed back new images of Ultima Thule, which show that the most distant world ever explored is much flatter than previously thought. "The new images are creating scientific puzzles about how such an object could even be formed,” mission scientist Alan Stern said in a statement. "We’ve never seen something like this orbiting the sun.” The images of the KBO — officially named 2014 MU69 — were captured by the New Horizons as it raced away at over 50,000 kilometres per hour on January 1. NASA’s New Horizons hurtled past Ultima Thule on New Year’s Day this year, taking pictures and gathering data as it flew within 3500 kilometres of the 32-kilometre-long rock. The latest pictures were taken after the spacecraft had passed it, revealing a different angle, Newscientist reported.  

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The images were taken nearly 10 minutes after New Horizons crossed its closest approach point.

“This really is an incredible image sequence, taken by a spacecraft exploring a small world four billion miles away from Earth,” said mission principal investigator Alan Stern, of Southwest Research Institute in the US.

The first close-up images of Ultima Thule — with its two distinct and, apparently, spherical segments — had observers calling it a “snowman.”

However, more analysis of approach images and these new departure images have changed that view, in part by revealing an outline of the portion of the KBO that was not illuminated by the Sun, but could be “traced out” as it blocked the view to background stars.

 “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.

“It would be closer to reality to say Ultima Thule’s shape is flatter, like a pancake. But more importantly, 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,” he said.

The departure images were taken from a different angle than the approach photos and reveal complementary information on Ultima Thule’s shape.

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“The shape model we have derived from all of the existing Ultima Thule imagery is remarkably consistent with what we have learned from the new crescent images,” said Simon Porter, a New Horizons co-investigator from the Southwest Research Institute.