Scientists Solve Mystery of 'Space Snowmen' in Solar System

Scientists just figured out how the solar system creates its own snowmen, and the answer is surprisingly elegant.

Beyond Neptune's orbit, astronomers have spotted dozens of mysterious objects shaped exactly like snowmen: two spheres gently stuck together. NASA's New Horizons spacecraft captured the first close-up images of these "contact binaries" in 2019, and researchers estimate up to one in four distant icy objects share this charming shape.

The question of how they formed has puzzled scientists for years. Now, a team at Michigan State University has found the answer using new computer simulations that model these objects more realistically than ever before.

Instead of treating these ancient building blocks as solid spheres, the researchers modeled them as clouds of pebble-sized particles. As these clouds spin in space, they sometimes form pairs of objects that orbit each other like cosmic dance partners.

Over time, the paired objects spiral closer due to gravity's gentle tug. Eventually, they touch and fuse together, creating the snowman shape that can last for billions of years in the quiet depths of space.

"What is so cool about this model is that it can create planetesimals that are not only spherical but also flat, cigar-shaped and, yes, snowman-shaped," said lead author Jackson Barnes, explaining how the speed and particle strength determine each object's final form.

The Ripple Effect

This discovery helps scientists understand how our solar system formed over 4.5 billion years ago. These icy snowmen are essentially time capsules, preserving the original process of how small particles clumped together to eventually build planets.

The research also explains why these delicate pairs stay together for so long. In the outer solar system's vast emptiness, they rarely collide with anything else. Without impacts to break them apart, they maintain their gentle embrace across the eons.

The team is now investigating even more complex formations. Some particle clouds create triple systems with three objects orbiting together, matching observations of rare triple systems in the Kuiper Belt.

These cosmic snowmen remind us that even in the coldest, most distant reaches of space, gentle forces are still at work creating something beautiful.