As computers get more powerful, astronomers and planetary scientists are piece by piece trying to take this amazing wealth of data we have and build a coherent understanding of how all the crazy things we find could come into being. One of the more recent points of struggle has been the Kuiper Belt object Arrokoth. This bilobate object had to form through a slow motion collision, and while we have been able to wave our hands and say “These are the requirements.” This is like tasting a meal and being able to taste all the ingredients. It’s a start, but throwing all those ingredients into a bowl and staring at them won’t make you a meal. There is the “how did this happen” that is also needed. Now, a group of computational modelers from the Technion Society have published in Nature results on a model that looks at the two lobes of Arrokoth as separate bodies orbiting the Sun. Including the Sun makes this a 3 body problem that has to be numerically stepped through, analyzing how all the forces play out over time. This careful approach allowed them to see how the two objects could gravitationally catch each other and tumble in a circular path around a gravitational center of their 2 masses while orbiting the Sun. This isn’t stable, and over time, the orbit would evolve, going elliptical, and then spiraling the object in to gently merge. It is a beautiful numerical dance, and I’m sad to report they didn’t share a video of their model. Nonetheless, we now know in numbers how Arrokoth could come to be.

More:

The Birth of a “Snowman” at the Edge of the Solar System (ATS.org)