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NASA’s New Horizons Mission Reveals Entirely New Kind of World

This composite image of Arrokoth was compiled from data obtained by NASA's New Horizons spacecraft as it flew by the object on Jan. 1, 2019.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko

Scientists from NASA's New Horizons mission released the first detailed images of the most distant object ever explored — the Kuiper Belt object nicknamed Ultima Thule (and later officially named Arrokoth). Its remarkable appearance, unlike anything we've seen before, illuminates the processes that built the planets four and a half billion years ago.

"This flyby is a historic achievement," said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. "Never before has any spacecraft team tracked down such a small body at such high speed so far away in the abyss of space. New Horizons has set a new bar for state-of-the-art spacecraft navigation."

This image taken by the Long-Range Reconnaissance Imager (LORRI) is the most detailed of Ultima Thule returned so far by the New Horizons spacecraft. It was taken at 5:01 Universal Time on Jan. 1, 2019, just 30 minutes before closest approach from a range of 18,000 miles (28,000 kilometers), with an original scale of 730 feet (140 meters) per pixel.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The new images — taken from as close as 17,000 miles (27,000 kilometers) on approach — revealed Ultima Thule as a "contact binary," consisting of two connected spheres. End to end, the world measures 19 miles (31 kilometers) in length. The team has dubbed the larger sphere "Ultima" (12 miles/19 kilometers across) and the smaller sphere "Thule" (9 miles/14 kilometers across).

The team says that the two spheres likely joined as early as 99% of the way back to the formation of the solar system, colliding no faster than two cars in a fender-bender.

three views of the object, showing how color data was overlaid onto a higher resolution version to create a color view

The first color image of Ultima Thule, now officially called Arrokoth, was taken at a distance of 85,000 miles (137,000 kilometers) at 4:08 Universal Time on Jan. 1, 2019. It highlights its reddish surface. At left is an enhanced color image taken by the Multispectral Visible Imaging Camera (MVIC), produced by combining the near infrared, red and blue channels. The center image taken by the Long-Range Reconnaissance Imager (LORRI) has a higher spatial resolution than MVIC by approximately a factor of five. At right, the color has been overlaid onto the LORRI image to show the color uniformity of the Ultima and Thule lobes. Note the reduced red coloring at the neck of the object.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

"New Horizons is like a time machine, taking us back to the birth of the solar system. We are seeing a physical representation of the beginning of planetary formation, frozen in time," said Jeff Moore, New Horizons Geology and Geophysics team lead. "Studying Ultima Thule is helping us understand how planets form — both those in our own solar system and those orbiting other stars in our galaxy."

Data from the New Year's Day flyby will continue to arrive over the next weeks and months, with much higher resolution images yet to come.

"In the coming months, New Horizons will transmit dozens of data sets to Earth, and we'll write new chapters in the story of Ultima Thule — and the solar system," said Helene Winters, New Horizons Project Manager.

The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA's Science Mission Directorate. The Southwest Research Institute, based in San Antonio, leads the science team, payload operations, and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.