How Dust Gathers into Planets ✎ express

Original: "Planetesimal formation via the streaming instability persists under turbulence driven by magnetorotational instability"
arXiv:2603.17195 · 2026-03-17 · arXiv non-exclusive · independent analysis · 1 min
Turbulence doesn't always hinder planet formation.

Planets are born from dust. In a disk around a young star, tiny dust grains collide, stick together, and gradually grow like a snowball rolling down a hill. But there's a catch: the gas in the disk moves faster than the dust and drags on it, preventing it from clumping into large chunks.

For dust to stick together, there needs to be enough of it. Then the grains start to 'feel' each other and gather into dense clumps. This process is called streaming instability. Turbulence in the gas can scatter such clumps, but as it turns out, not all turbulence does.

Turbulence generated by the disk's own magnetic field barely hinders dust from clumping. But artificially added turbulence hinders it a lot.

For the first time, scientists simulated a disk with a magnetic field and accounted for turbulence arising naturally from the gas's rotation. They found that dust gathers into large structures — zonal flows, similar to the cloud bands on Jupiter. Inside these flows, dust accumulates and sticks together into planetesimals — the seeds of planets.

This means turbulence isn't always the enemy of planet formation. If it arises from the disk's magnetic field, even strong turbulence only slightly hinders dust from gathering into future planets.

Planetesimals are the building blocks of planets. Earth, for example, formed from them over several tens of millions of years.

Scientists
Christian DopplerD. B. McLaughlinDidier QuelozMichel MayorR. A. RossiterDavid Charbonneau
Concepts
planetesimal formation gravitational instability dust dynamics protoplanetary disk dynamics planetary composition formation dust rocky planet gas turbulent coagulation protoplanetary disk winds clump planetary accretion chemistry dense clump structure growth planet interstellar gas turbulent mixing tidal heating mantle rossby wave