New Horizons discovers that Ultima Thule has a flattened and unexpected shape – Spaceflight Now

Scientists' understanding of the shape of the Ultima Thule, officially known as MU69 2014, has evolved since the New Horizons spacecraft survey on January 1st. Probe reticulated images in recent weeks suggest that both Ultima Thule lobes have a flatter shape than the spherical projection suggested by the first flyover images. The dashed blue line marks the remaining uncertainty in the shape of each lobe. Credit: NASA / Applied Physics Laboratory, Johns Hopkins University / Southwest Research Institute

Images taken by NASA's New Horizons spacecraft when flying over an object the size of a large metropolitan area at the solar system's border on January 1 revealed that the miniature world had a more flattened shape than did not suggest the initial images of the flyover.

The oddly shaped object in the Kuiper Belt, located 1.6 billion kilometers beyond Pluto, became the farthest planetary body ever explored when the New Horizons spacecraft was zipped on January 1 at a relative speed of about 32,000 km / h or 9 miles per second (14 kilometers per second).

Nicknamed Ultima Thule, the first target of the New Horizons shuttle after his visit to Pluto in 2015 turned out to be a two-lobed object as the spacecraft returned its first close-up images to Earth after the New Year's meeting.

But instead of having the shape of a snowman – with a spherical lobe larger than the other – scientists now think that both sections of Ultima Thule have a more flattened shape.

The larger of the two lobes – nicknamed Ultima – seems to have the shape of a giant pancake or pebble that could be projected to jump on the water. The smaller lobe, nicknamed Thule, looks like a broken nut, according to mission scientists.

"We had an impression of Ultima Thule based on the limited number of images returned in the days that followed, but having more data dramatically changed our vision," said Alan Stern, principal investigator of the New Horizons mission of the Southwest Research Institute, in a statement of 8 February. "It would be closer to the reality to say that Ultima Thule's shape is flatter, like a pancake. But more importantly, the new images create scientific puzzles on how such an object could even be formed. We have never seen anything like this in orbit around the sun. "

In the early days following the overflight, the scientists indicated that they thought the object had formed when two objects – which originally formed separately when the solar system was born 4.5 billion years ago – merged at a slow pace.

Scientists used a series of images captured by New Horizons when he left Ultima Thule to assess the shape of the object from the edge. Previously published images showed the approach of the sunny side of Ultima Thule from New Horizons, but the starting sequence reveals a Ultima Thule crescent.

The shaded side of Ultima Thule traced a path through a field of stars in the background, briefly blocking starlight as New Horizons completed its flyby.

"It's really an incredible sequence of images, taken by a spaceship exploring a small world four billion kilometers from Earth," Stern said. "Nothing like it has ever been captured in the pictures."

The central frame of the 14 individual images used to create the video was taken by the telescope Long Range Recognition Imager, or LORRI, of the spacecraft, at 12:42 pm EST (05:42 GMT), nine minutes after the closest approach to the probe. at Ultima Thule. At that time, New Horizons was 8992 km (5,494 miles).

The telescopic camera has been configured to take pictures with relatively long exposure times due to the low light levels reflected by the Ultima Thule crescent, which makes the individual pictures blurry.

"While the very nature of a quick flyby limits, in a way, our ability to determine the actual shape of Ultima Thule, the new results clearly show that Ultima and Thule are much flatter than they are. was thinking initially, and a lot flatter than expected, "Hal said. Weaver, scientist of the New Horizons project of the Johns Hopkins Applied Physics Laboratory. "This is undoubtedly going to motivate new theories about planetesimal training in early solar systems."

Images and other data collected by New Horizons at Ultima Thule continue to return to Earth at approximately 1,000 bits per second, at a distance of more than 6.6 billion kilometers. Final flyover data is expected to arrive on Earth in September 2020.

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Follow Stephen Clark on Twitter: @ StephenClark1.

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