The truly odd shape of Ultima Thule

This really is an incredible image sequence, taken by a spacecraft exploring a small world four billion miles away from Earth.

Scientists’ understanding of Ultima Thule has changed as they review additional data. 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 Jan. 1, 2019, suggesting that both of “Ultima” (the larger section, or lobe) and “Thule” (the smaller) were nearly perfect spheres just barely touching each other. But as more data were analyzed, including several highly evocative crescent images taken nearly 10 minutes after closest approach, a “new view” of the object’s shape emerged. Ultima more closely resembles a “pancake,” and Thule a “dented walnut.” The bottom view is the team’s current best shape model for Ultima Thule, but still carries some uncertainty as an entire region was essentially hidden from view, and not illuminated by the Sun, during the New Horizons flyby. The dashed blue lines span the uncertainty in that hemisphere, which shows that Ultima Thule could be either flatter than, or not as flat as, depicted in this figure. Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute
Scientists’ understanding of Ultima Thule has changed as they review additional data. 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 Jan. 1, 2019, suggesting that both of “Ultima” (the larger section, or lobe) and “Thule” (the smaller) were nearly perfect spheres just barely touching each other. But as more data were analyzed, including several highly evocative crescent images taken nearly 10 minutes after closest approach, a “new view” of the object’s shape emerged. Ultima more closely resembles a “pancake,” and Thule a “dented walnut.” The bottom view is the team’s current best shape model for Ultima Thule, but still carries some uncertainty as an entire region was essentially hidden from view, and not illuminated by the Sun, during the New Horizons flyby. The dashed blue lines span the uncertainty in that hemisphere, which shows that Ultima Thule could be either flatter than, or not as flat as, depicted in this figure. Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute

NASA’s New Horizons spacecraft offers an evocative series of an image- a departing view of the Kuiper Belt object (KBO) nicknamed Ultima Thule.

Though these are not last Ultima Thule images, as many more are to come- but these images are the final view of New Horizons captured of the KBO (officially named 2014 MU69) as it raced away at over 31,000 miles per hour (50,000 kilometers per hour) on Jan. 1. The images were taken nearly 10 minutes after New Horizons crossed its closest approach point.

The newly released images also contain important scientific information about the shape of Ultima Thule, which is turning out to be one of the major discoveries from the flyby.

The primary close-up pictures of Ultima Thule – with its two particular and, evidently, circular fragments – had onlookers considering it a “snowman.” However, more investigation of methodology pictures and these new flight pictures have changed that see, partially by uncovering a diagram of the bit of the KBO that was not lit up by the Sun, yet could be “followed out” as it hindered the view to foundation stars.

Mission scientists created this “departure movie” from 14 different images taken by the New Horizons Long Range Reconnaissance Imager (LORRI) shortly after the spacecraft flew past the Kuiper Belt object nicknamed Ultima Thule (officially named 2014 MU69) on Jan. 1, 2019. The central frame of this sequence was taken on Jan. 1 at 05:42:42 UT (12:42 a.m. EST), when New Horizons was 5,494 miles (8,862 kilometers) beyond Ultima Thule, some 4.1 billion miles (6.6 billion kilometers) from Earth. The object’s illuminated crescent is blurred in the individual frames because a relatively long exposure time was used during this rapid scan to boost the camera’s signal level – but the science team combined and processed the images to remove the blurring and sharpen the thin crescent. This is the farthest movie of any object in our Solar System ever made by any spacecraft. The images reveal an outline of the “hidden” portion of the Ultima Thule that was not illuminated by the Sun as the spacecraft zipped by, but can be “traced out” because it blocked the view to background stars also in the image. Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute/National Optical Astronomy Observatory

Stringing 14 of these pictures into a short flight film, New Horizons researchers can affirm that the two areas (or “flaps”) of Ultima Thule are not spherical. The larger lobe, nicknamed “Ultima,” all the more intently looks like a giant hotcake and the smaller lobe, nicknamed “Thule,” is formed like a dented walnut.

Principal Investigator Alan Stern, of Southwest Research Institute, said, “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. It would be closer to reality to say Ultima Thule’s shape is flatter, like a pancake. But more 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.”

The departure pictures were taken from an unexpected point in comparison to the methodology photographs and uncover integral data on Ultima Thule’s shape. The focal edge of the grouping was gone up against Jan. 1 at 05:42:42 UT (12:42 a.m. EST), when New Horizons was 5,494 miles (8,862 kilometers) past Ultima Thule, and 4.1 billion miles (6.6 billion kilometers) from Earth.

The object’s illuminated crescent is obscured in the individual edges in light of the fact that a generally long presentation time was utilized amid this fast sweep to support the camera’s signal level – however, the science group consolidated and handled the pictures to expel the obscuring and sharpen the thin crescent.

Hal Weaver, New Horizons project scientist from the Johns Hopkins Applied Physics Laboratory said, “While the very nature of a fast flyby in some ways limits how well we can determine the true shape of Ultima Thule, the new results clearly show that Ultima and Thule are much flatters than originally believed, and much flatter than expected. This will undoubtedly motivate new theories of planetesimal formation in the early solar system.”