Israeli team explains properties of most distant object in outer space

Arrokoth was first photographed in 2019 by the New Horizons space mission, the same mission that provided the world its best pictures of Pluto and its moon Charon.

Image showing results of Technion researchers’ detailed simulations of the Kuiper Belt objects’ collision that formed Arrokoth (photo credit: COURTESY TECHNION)
Image showing results of Technion researchers’ detailed simulations of the Kuiper Belt objects’ collision that formed Arrokoth
(photo credit: COURTESY TECHNION)
Israeli scientists have developed a model to explain the unique properties of the most distant object ever imagined in the Solar System, shedding new light on the formation of Kuiper Belt objects – asteroid-like objects at the edge of the Solar System – and helping scientists better understand the early stages of the Solar System’s formation.
The research, led by a team from the Faculty of Physics at the Technion-Israel Institute of Technology – Ph.D. student Evgeni Grishin, postdoc Dr. Uri Malamud, and their supervisor Prof. Hagai Perets – in collaboration with a German research group in Tübingen, was recently published in the British multidisciplinary scientific journal Nature.
Evgeni Grishin  (Credit: Courtesy of The Technion)Evgeni Grishin (Credit: Courtesy of The Technion)
Specifically, their work explains the unique characteristics of Arrokoth, affectionately known as “the Snowman” because it is likely predominantly made of soft ice and because of its two different sized lobes interconnected with a thin neck.
Arrokoth was first photographed in 2019 by the New Horizons space mission, the same mission that provided the world’s best pictures of Pluto and its moon Charon.
New Horizons photograph of Arrokoth (Credit: Courtesy of NASA)New Horizons photograph of Arrokoth (Credit: Courtesy of NASA)
Pluto is the largest known object at the far end of the Solar System, the region beyond the planet Neptune, which is known as the Kuiper Belt. In this area there are numerous asteroid-like objects ranging in size from a few feet to thousands-of-miles-big. The area is colder than in the inner region of the Solar System and most of the objects, like the Snowman, are made of icy materials.
Until now, scientists have worked to explain the formation of Arrokoth and its peculiar properties, which the Technion’s Malamud explained are three:
First, Arrokoth is made of two connected lobes – which were once two separate objects – but there is hardly any deformation at the contact point.
“It is almost like they are attached to one another very gently, which is something we have never seen before,” Malamud told The Jerusalem Post.
Dr. Uri Malamud (Credit: Courtesy of The Technion)Dr. Uri Malamud (Credit: Courtesy of The Technion)
Second, the rotation period for this object around its axis is 16 hours, which is considered slow.
Finally, Arrokoth’s angle of inclination (relative to the plane of its orbit around the Sun) is exceptionally large – 98 degrees – so it almost lies on the side relative to its orbit, making it look like a sandglass.
Although various models have been proposed to explain Arrokoth’s formation and its other peculiar properties, each one has had one or more shortcoming, Malamud said. The Technion and Tübingen team’s analytic calculations and detailed simulations work.
“It evolved from having a wide, relatively circular orbit, into a highly eccentric, elliptic orbit through a slow evolution, much slower compared to the orbital period of Arrokoth around the Sun.” said Prof. Perets. “We could show that such trajectories eventually lead to a collision, which on the one hand will be slow, and not smash the objects, but on the other hand, produce a slowly-rotating, highly inclined object, consistent with Arrokoth properties.”
Professor Hagai Perets (Credit: Courtesy of The Technion)Professor Hagai Perets (Credit: Courtesy of The Technion)
“We performed a simulation of the actual collision using a hydrodynamical code,” Malamud continued. “Our detailed simulations confirmed this picture, and produced models closely resembling Arrokoth’s snowman appearance, rotation and inclination… We showed it is really possible to get these two lobes together without any deformation.”
Moreover, he said, the team studied how robust and probable such processes are and found them to potentially be quite common with as many as 20% of all Kuiper Belt wide binaries, and potentially evolving in similar ways. In fact, they said, even Pluto's and Charon's system might have formed through a similar process.
“We think this mechanism could affect a lot of other objects in the Solar System,” Malamud concluded. “If that’s true, then it is even more significant.”