Turbulence vs. Magnetism: How the Seeds of Massive Star Clusters Are Born

In the high-altitude Atacama Desert, where the air is thin and dry and the sky feels remarkably close, the Atacama Large Millimeter/submillimeter Array (ALMA)—one of modern astronomy's most powerful tools—is at work. This international radio telescope network allows scientists to peer into the universe's coldest, dustiest corners where stars are born. Recent ALMA observations published in May 2026 have yielded a surprising result: in the tiny ‘seeds’ that form massive star clusters, chaotic turbulence appears to overpower orderly magnetic fields.

Massive stars—those at least eight times heavier than the Sun—play a fundamental role in galactic evolution. They emit intense ultraviolet radiation, drive powerful stellar winds, enrich the cosmos with heavy elements, and end their lives in spectacular supernova explosions. Yet, exactly how they form within crowded stellar nurseries has remained a mystery. Scientists have long known that giant molecular clouds fragment into increasingly smaller structures: first into clusters, then clumps, and finally into compact condensations roughly 0.01 parsecs across. These condensations serve as the direct ‘parent’ structures for protostellar disks and the future stars or tight multiple systems they produce.

Magnetic fields have traditionally been viewed as critical regulators of this process. On the scales of large clouds and clumps (exceeding 0.1 parsecs), gas compresses more easily along magnetic field lines than across them. As a result, these structures are often elongated perpendicular to the field. However, at the smallest scales where individual stars take shape, a different picture has emerged.

An international team led by Junhao Liu of Nanjing University analyzed data from the largest ALMA survey to date on dust polarization in massive star-forming regions, known as the MagMaR project, to study hundreds of compact condensations across 30 regions of the Milky Way. Dust grains align themselves along magnetic lines, polarizing millimeter-wave radiation in the process. This effect allows researchers to ‘see’ the field's orientation at a resolution of just hundreds of astronomical units.

The findings were unexpected: at these small scales, condensations are more frequently aligned parallel to local magnetic fields—the opposite of what is seen at larger scales. Comparisons with three-dimensional magnetohydrodynamic simulations revealed that this pattern occurs when turbulence dominates over magnetism. Turbulent flows compress gas into flattened structures, strengthening the magnetic field components along their elongated axes.

‘Magnetic fields or turbulence? It is a cosmic battle between order and chaos,’ Liu notes. ‘On large scales, orderly fields give structure to clouds, but during the formation of individual stars and clusters, they lose out to chaos.’

Additionally, researchers discovered a statistical discrepancy between the directions of magnetic fields and the rotation axes of the condensations. This ‘misalignment’ may weaken magnetic braking, allowing gas to maintain its angular momentum and form large protostellar disks—a key factor in the growth of massive stars and the birth of multiple-star systems.

These results do not dismiss the role of magnetic fields entirely; they likely help organize large clouds. However, at the critical small scales, it is turbulence that sets the tone. ALMA's combination of high sensitivity and resolution has enabled the first systematic study of this physics. The study, published in Nature Astronomy, challenges conventional wisdom regarding massive star cluster formation and raises new questions for theory and modeling.

Each discovery like this serves as a reminder of how complex and multifaceted the process of star formation truly is. ALMA continues to reveal the hidden mechanisms by which cold cosmic gas gives rise to the stars that determine the destiny of galaxies.