Liquid gallium experiment confirms key flow regime inside rapidly rotating stars and planets

An international research team has experimentally demonstrated a flow state characteristic of the interiors of rapidly rotating stars and planets. The study, conducted using liquid gallium in a rotating laboratory setup, produced the first experimental verification of a theoretically predicted flow state. The results provide a robust experimental basis for testing theoretical models of the processes that occur inside these celestial bodies. The experiment used a special oscillating flow mode that occurs exclusively in liquid metals, allowing the creation of conditions that models have long predicted.

The study was led by the University of California, Los Angeles (UCLA) and included the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research team achieved the decisive breakthrough by eliminating thermal boundary layers on the walls of the test vessels, which had previously obscured the flow state. The experiment demonstrated the diffusivity-free regime, in which large flows are determined almost exclusively by buoyancy and rotation while fluid properties such as viscosity or thermal conductivity become almost negligible. The results were validated through three independent metrics: heat transport, flow velocity, and temperature fluctuations within the fluid. All three matched the models quantitatively, and high-resolution numerical simulations further confirmed the results.

The findings close a decades-old gap between theory and experiment, opening up new possibilities for investigating the dynamics inside stars and planets in lab experiments—for more reliable models of these fundamental processes in the universe. The results strengthen confidence in the models used to describe processes inside stars and planets, and provide a new pathway into the interior of stars.

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