New Horizons' faraway target is 'pretty pancake-like,' scientists discover

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We have never explored a world more distant than the mysterious Kuiper Belt object (KBO) otherwise known as 2014 MU69 or Ultima Thule. The "old view" in this illustration is based on images taken within a day of New Horizons' closest approach to the Kuiper Belt object on January 1, 2019. Now, astronomers have been thrown for a loop when New Horizons' final series of images of Ultima Thule reveal that the twin rocks aren't actually round.

"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", said principal investigator Alan Stern. Now New Horizons is bidding farewell to another long-distance neighbor, but not before throwing scientists new puzzles to munch on about the odd Ultima Thule.

NASA has just gotten another view of Ultima Thule, the most distant object ever visited, and it's surprisingly unlike what they'd previously expected it would appear - and like nothing they've seen before.

"But importantly, the new images are creating scientific puzzles about how such an object could even be formed. We've never seen anything like this orbiting the Sun". "Nothing quite like this has ever been captured in imagery". At left: An "average" of 10 photos taken by the Long Range Reconnaissance Imager (LORRI); the crescent is blurred because a relatively long exposure time was used during this rapid scan to boost the camera's signal level.

Instead of a snowman, Ultima Thule is better described as a dented walnut smashed with a pancake.

In order to deduce the object's shape, scientists watched the background stars on the images.

Though it will take approximately 20 months for New Horizons to get all of its pictures, measurements and other scientific data back home to Earth, the newly released images are sure to "motivate new theories of planetesimal formation in the early solar system", Hal Weaver, New Horizons project scientist from the Johns Hopkins Applied Physics Laboratory, said.

Ultima Thule, or more specifically Kuiper Belt Object 2014 MU69, is a so-called trans-Neptunian binary rock in the Kuiper Belt, a field of asteroids in the outer reaches of the solar system.

This interpretation is evident from the data acquired by the Nasa spacecraft when it looked back at icy Ultima Thule as it zoomed past at 50,000km/h.

Many background stars are also seen in the individual images; watching which stars "blinked out" as the object passed in front them allowed scientists to outline the shape of both lobes, which could then be compared to a model assembled from analysing pre-flyby images and ground-based telescope observations.

New Horizons' first images confirmed some predictions and dispelled others, revealing MU69 to be a snowman-shaped world with a rusty red hue that spins end-over-end like a propeller.

The primitive world was "born" this way, and did not evolve or deform through external processes to take on the unusual shape, the team explains.

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