Unraveling the Cosmic Snowman: Scientists Pinpoint Arrokoth's Peculiar Formation

United States - Ekhbary News Agency

Unraveling the Cosmic Snowman: Scientists Pinpoint Arrokoth's Peculiar Formation

On January 1st, 2019, NASA's New Horizons mission made history when it became the first spacecraft to conduct a close flyby with Arrokoth, a Kuiper Belt Object (KBO) located beyond the orbit of Pluto. But the greater achievement was not merely the flyby, but the images it captured, which revealed an object with a distinctive snowman-shaped profile, surprising and perplexing astronomers worldwide. Since then, scientists have been engaged in intense debate about how such peculiar objects could form in the frigid, distant reaches of our Solar System. Now, researchers at Michigan State University (MSU) believe they have found the answer, and it's remarkably simple: gravitational collapse.

Arrokoth resides in the Kuiper Belt, a vast, icy region beyond Neptune's orbit, populated by millions of icy bodies often referred to as 'iceteroids'. These objects are pristine remnants from the early days of the Solar System, preserving conditions and compositions from nearly 4.5 billion years ago. Planetesimals, the building blocks of planets, similarly formed from the rotating disk of gas and dust that surrounded our young Sun after its own gravitational collapse. What made Arrokoth so perplexing was that roughly 1 in 10 of these KBOs are, in fact, 'contact binaries' – two distinct objects that have merged together in what appears to be a remarkably gentle fashion, resulting in unique shapes like the snowman.

Previous computational models had long struggled to account for this formation. These models, often based on fluid dynamics, had effectively ruled out the possibility of objects forming such unique and stable shapes. Furthermore, other theories that posited unique events or rare phenomena could not explain the observed commonality of these contact binaries. The challenge was to find a mechanism that could explain not only Arrokoth's specific shape but also its being part of a more widespread class of cosmic objects.

Enter the Michigan State University team, led by graduate student Jackson Barnes, and guided by Professor Seth Jacobson, a senior author on the paper. The team developed groundbreaking simulations using MSU's high-performance computing cluster at the Institute for Cyber-Enabled Research (ICER). Unlike their predecessors, these simulations were the first to be grounded in the principles of gravitational collapse. The results were striking: the simulations not only successfully reproduced Arrokoth's distinctive snowman profile but also created a more realistic scenario in which these objects form regularly. As Professor Jacobson explained in an MSU press release, "If we think 10 percent of planetesimal objects are contact binaries, the process that forms them can’t be rare. Gravitational collapse fits nicely with what we’ve observed."

The simulations illustrate a captivating process: in the early Solar System, as planetesimals were forming from the disk of rotating matter, these objects would sometimes be torn apart by the disk's rotational force, forming two separate objects that would then orbit one another. Over time, the orbits of these objects would gradually spiral inward until they made contact and fused together, crucially retaining their original round shapes. This gentle merging process is key to preserving the distinctive snowman-like appearance, as it doesn't involve violent collisions that would deform the structure.

Furthermore, their results showed that these contact binaries remain intact by effectively avoiding collisions with other objects, an observation that perfectly aligns with real-world data; most binaries show no indication of craters. This discovery confirms something scientists had suspected for some time but were unable to test empirically. The model created by Barnes and his colleagues is the first to successfully reproduce contact binaries by accurately accounting for the necessary physics. The team isn't stopping there; they are currently working on a new simulation to better model the gravitational collapse process, which they hope will predict other exotic objects discovered in the outer Solar System. This pioneering research, "Direct contact binary planetesimal formation from gravitational collapse," was published in the *Monthly Notices of the Royal Astronomical Society* (MNRAS), opening a new chapter in our understanding of our Solar System's origins.

Ekhbary News Agency