Insights into Arrokoth's Formation: New Simulations Reveal Gravitational Collapse Mechanism

Arrokoth, a 4 billion-year-old object located in the Kuiper belt, has garnered attention as the most distant and primitive body visited by a spacecraft. Researchers have recently provided new insights into its distinctive snowman-like shape, which is characteristic of approximately 10-25% of the planetesimals found in this region. The Kuiper belt, situated beyond Neptune's orbit, is home to various icy objects, including dwarf planets and comets.

The Guardian

Previous studies suggested that Arrokoth's lobes formed simultaneously and gently through a process known as gravitational collapse. However, the specifics of this process remained a topic of debate among scientists. Recent computer simulations conducted by a team at Michigan State University have confirmed that gravitational collapse can indeed lead to the formation of double-lobed objects like Arrokoth. Jackson Barnes, the lead author of the study, expressed excitement over the ability to visualize this process for the first time, stating, “It’s so exciting because we can actually see this for the first time.”

The Guardian

The research team ran 54 simulations using a model that included an initial pebble cloud of 105 particles, each approximately 2 kilometers in radius. The simulations revealed that in certain scenarios, two small planetesimals could orbit each other and eventually collide at low velocities, forming a contact binary resembling Arrokoth. Barnes noted that these findings align with the long-held view that planetesimals generally form through gravitational collapse.

The Guardian

Alan Stern, a planetary scientist and principal investigator of NASA's New Horizons mission, praised the study for supporting the hypothesis of gentle formation processes for Kuiper belt objects like Arrokoth. Conversely, Alan Fitzsimmons, an emeritus professor of astronomy at Queen’s University Belfast, pointed out a discrepancy: while the simulations indicated that only 4% of objects in the Kuiper belt formed as contact binaries, telescopic surveys suggest a significantly higher fraction. Fitzsimmons remarked, “It may be that Mother Nature prefers other ways of making them, or that future even more complex simulations can close the gap between what is calculated and what we see.”

The Guardian

The new simulations provide valuable insights into the formation of Arrokoth and similar objects in the Kuiper belt, reinforcing the gravitational collapse theory while also highlighting areas for further research. As scientists continue to explore the origins of these ancient bodies, the findings may reshape our understanding of the early solar system's dynamics.

The Guardian