Topic: Space

Astronomers have long wondered why many icy bodies in the outer solar system look like snowmen. Researchers at Michigan State University found a surprising explanation: gravitational collapse.

In the distant Kuiper Belt, beyond Neptune's orbit, lies a region filled with frozen remnants from the solar system's earliest days. These primitive objects, called planetesimals, are leftover building blocks from planet formation. About 10 percent of them have a unique shape – two rounded sections joined together, like snowmen.

Until recently, scientists didn't know how these shapes formed naturally. Jackson Barnes, a graduate student at MSU, developed the first computer simulation capable of producing these double-lobed structures through gravitational collapse.

Previous models simplified impacts by treating colliding bodies as fluid masses that blended into smooth spheres. This assumption prevented researchers from recreating the distinctive two-part shape seen in contact binaries. Barnes' model allowed forming objects to retain their structural strength, allowing them to settle against each other rather than merge into a single sphere.

The Kuiper Belt itself is a relic of the early Milky Way, when the galaxy existed as a rotating disc of gas and dust. That ancient material still lingers in this region, including dwarf planets like Pluto, comets, and countless planetesimals.

Why It Matters

Understanding how these shapes form can help us better understand the solar system's history and the formation of planets. It also shows that even complex phenomena can have simple explanations.

Key Facts

• About 10 percent of Kuiper Belt objects are contact binaries, with two rounded sections joined together.
• Gravitational collapse is a surprisingly straightforward process that can explain how these shapes form.
• The Kuiper Belt is a relic of the early Milky Way and contains dwarf planets like Pluto, comets, and countless planetesimals.

Key Terms

Planetesimal

A small, icy body left over from the solar system's formation

Implications

Understanding how these shapes form can help us better understand the solar system's history and the formation of planets. It also shows that even complex phenomena can have simple explanations.