Ultima Thule is more pancake than snowman, NASA scientists discover
Feb 12 2019
Taken nearly 10 minutes after New Horizons' closest approach to the object, the final images taken of Ultima Thule show the side of the object not illuminated by the sun against the backdrop of distant stars.
The latest images of Ultima Thule shows the KBO as it was racing away at 31,000 miles per hour (50,000 kilometers per hour), about 10 minutes after New Horizons made its closest approach.
While these are far from the final photos of UltimaThule that New Horizons will send back, they do represent the spacecraft's last glimpses of the rock as it streaked away.
The first image the probe beamed back showed two reddish-coloured spherical segments on top of each other, like a snowman. However, analysis of both the approach and departure images have changed this view because of the revealing of an outline, which was not seen before as it was not illuminated by the sun.
NASA's unmanned New Horizons spacecraft gets a new view of the space rock, UltimaThule, from a different angle. Its larger lobe, nicknamed "Ultima", is flatter than the smaller lobe, nicknamed "Thule", which is more like a beat up walnut in shape.
"It would be closer to reality to say MU69's shape is flatter, like a pancake", Stern added.
Project scientist Hal Weaver of Johns Hopkins University, home to New Horizons flight control center, said the finding should spark new theories on how such primitive objects formed early in the solar system. "We've never seen something like this orbiting the Sun", he said. More data should help to resolve some of these questions as scientists study UltimaThule.
"The shape model we have derived from all of the existing UltimaThule imagery is remarkably consistent with what we have learned from the new crescent images", says Simon Porter, a New Horizons co-investigator from the Southwest Research Institute, who leads the shape-modeling effort. New Horizons' camera was forced to use a longer exposure time to capture the photos, blurring the images.
The newest sequence of images suggests that instead of two spheres, MU69's sections (called "lobes") are somewhat flat. The hope is that UltimaThule's structure and composition can reveal new insights on how all planetary bodies came into being just over 4.6 billion years ago. As more data were analyzed, including several highly evocative crescent images taken almost 10 minutes after closest approach, a "new view" of the object's shape emerged. The shape is relatively unprecedented in scientific observations of the solar system. On that day, it had its close-up flyby of the Edgeworth-Kuiper Belt object known as UltimaThule, a chunk of space debris that had previously caught the eye of astronomers of Earth.