Why This Region of Space Appears to Be Populated by Snowmen

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OhAt the outer edge of our solar system, beyond the orbit of Neptune, lies the Kuiper Belt, a wide band of small bodies drifting lazily in orbit around the sun. A remnant of the formation of the Solar System, this collection of cosmic crumbs includes dwarf planets as well as smaller planetesimals composed primarily of ice, methane, and ammonia.

Many of these planetesimals – almost one in ten – look suspiciously like snowmen, with a smaller sphere stuck on top of a larger one. Now, new research published in Monthly Notices of the Royal Astronomical Society offers a simple explanation of why.

Called contact binaries, these icy snowmen have intrigued researchers for years. Earlier models treated colliding bodies as fluids, which would result in one sphere, not two. Other theories involve events so rare and complicated that they are unlikely to be responsible for such a high proportion of binary contacts.

“If we think that 10% of planetesimal objects are contact binaries, the process that forms them cannot be rare,” study author Seth Jacobson of Michigan State University said in a statement.

Read more: »Why it’s hard for black holes to come together»

Instead, Jacobson and co-author Jackson Barnes used powerful computer simulations to test a gravitational collapse model for the formation of these wayward snowmen. “Gravitational collapse fits well with what we observed,” Jacobson said.

In this model, during the early years of our solar system, when it was nothing more than a cloudy disk of dust, tiny pebble-sized pieces of matter accumulated to form planetesimals. Sometimes the rotating cloud swirled around itself, tearing the planetesimals into two spheres orbiting each other in cosmic space. pas de deux until they touch and merge to form the oblong objects we see today.

While planetary scientists have debated the gravitational collapse model for years, this is the first time it has been demonstrated through computer simulations. “That’s what’s so exciting about this article,” enthused Barnes.

In the future, researchers hope this new model will help scientists better understand more complex systems featuring three or more bodies interacting in space. In the meantime, they can continue to watch the sky for signs of a top hat-shaped planetesimal to complete the snowman look.

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Main image: NASA

• Jake Currie

  Published on February 23, 2026

  Jake Currie is a writer based in Brooklyn, New York.