89 milliseconds. That's how long a vortex avalanche lasts that abruptly speeds up the rotation of the Vela pulsar — one of the most famous 'glitching' pulsars. Pulsars are rapidly spinning neutron stars born in the collapse of supernovae. Their rotation periods are more stable than Earth's clocks, but every now and then a glitch (a sudden speed-up) occurs — a tiny jump in frequency. The classic picture links it to the behavior of superfluid matter inside the star, where rotation is quantized into individual vortices.

The superfluid inside a neutron star is threaded with quantized vortices, each carrying a fixed amount of angular momentum. These vortices can pin to defects in the ionic lattice of the crust, like snowflakes catching on bumps on a slope. A velocity lag (speed difference) builds up between the crust and the superfluid, and the star's gravitational compression only amplifies the stress. At some point, the critical lag exceeds the threshold, and hundreds of thousands of vortices are released in an avalanche, transferring accumulated angular momentum to the crust. That's how a glitch is born. Jocelyn Bell Burnell discovered pulsars in 1967, Subrahmanyan Chandrasekhar laid the foundations for understanding superdense objects, and John Archibald Wheeler coined the term 'neutron star.' But until now, it remained a mystery why different pulsars exhibit different glitch distributions.

A research team built a simulator tracking up to 10⁵ vortices inside a cylindrical model of a neutron star. To speed up computations, they used the Barnes–Hut algorithm: distant clusters are replaced by an effective center, reducing the complexity from quadratic to nearly linear. In the crust, they placed a network of traps — regions with enhanced pinning, each the size of a basketball court (~100 m²). These traps mimic cracks that form as the star spins down, and they can hold an excess of vortices. When several traps release simultaneously due to a starquake, the glitch profile becomes step-like, and the size distribution becomes bimodal: a second peak appears for large events. That's exactly what is observed in the pulsar PSR J0537-6910.

An unexpected finding was the spontaneous emergence of giant vortex voids — in an initially uniform array, vortex-free zones appeared, up to a third of the star's size, persisting for long periods. This suggests that inhomogeneities may be intrinsic to the collective dynamics of quantum vortices, not only imposed by crustal defects. An avalanche that starts with a single misstep spawns a network of avalanches, and 89 milliseconds, just one beat of stellar evolution, completely rewrites the pulsar's rhythm.