New Horizons returns best view yet of Ultima Thule

Ultima Thule, as seen by NASA’s New Horizons spacecraft near close approach on 1 January. Image: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute, National Optical Astronomy Observatory

Just six-and-a-half minutes before the New Horizons spacecraft made its closest approach to Ultima Thule, a primitive Kuiper Belt body a billion miles past Pluto, the probe’s Long-Range Reconnaissance Imager camera captured this stunning view of the unusually smooth, bi-lobed object

Engineers considered the shots a “stretch goal” for the New Year’s Day flyby because of the spacecraft’s high speed and the dim environment of the outer solar system. At closest approach, New Horizons was just 3,500 kilometres (2,200 miles) from Ultima Thule, three times closer to its target than when the spacecraft raced past Pluto in July 2015.

“Getting these images required us to know precisely where both tiny Ultima and New Horizons were — moment by moment – as they passed one another at over 32,000 miles per hour in the dim light of the Kuiper Belt, a billion miles beyond Pluto,” said Alan Stern, the New Horizons principal investigator. “This was a much tougher observation than anything we had attempted in our 2015 Pluto flyby.

“These stretch goal observations were risky, because there was a real chance we’d only get part or even none of Ultima in the camera’s narrow field of view. But the science, operations and navigation teams nailed it, and the result is a field day for our science team! Some of the details we now see on Ultima Thule’s surface are unlike any object ever explored before.”

With a resolution of 33 metres (110 feet) per pixel, the new image reveals many details that were not apparent in earlier photos, including several bright, roughly circular patches and numerous small, dark pits near the terminator.

“Whether these features are craters produced by impactors, sublimation pits, collapse pits, or something entirely different, is being debated in our science team,” said deputy project scientist John Spencer.