89 milliseconds. In that time, a pulsar can suddenly increase its spin rate. A pulsar is a neutron star, born in the tremendous explosion of a supernova. It collapses to the size of a city, yet its mass exceeds that of the Sun. Such an object spins with the precision of an atomic clock, but every few years its rhythm skips a beat — a glitch, a sudden acceleration.

Inside a pulsar, matter is in a state of superfluidity: it flows without friction. This fluid is threaded by billions of microscopic vortices (in a real star, there are about 10¹⁷ of them — more than grains of sand on all the beaches of Earth). These vortices carry the star’s rotation, like tiny gears. They can get stuck on irregularities in the solid crust, like snowflakes on a mountainside. When the stress from the pinned vortices grows too large, they break free all at once, like an avalanche. This avalanche of vortex unpinning instantly spins up the crust, and that’s how a glitch occurs.

Jocelyn Bell Burnell discovered the first pulsar in 1967, but only recently have scientists been able to peer into the mechanism behind the glitches. A new numerical simulation revealed that the key lies in 'traps'—especially sticky patches of the crust. Under the immense force of gravity, the crust cracks, creating zones where vortices become particularly stuck. Each such trap is about the size of a basketball court. If one trap gives way, you get a small glitch. If several go at once, the glitch becomes stepwise and truly large. That’s exactly the picture observed in the real pulsar PSR J0537-6910: it experiences both small and large glitches.

And so, in 89 milliseconds, an avalanche of hundreds of thousands of vortices rewrites the rotation of an entire star. It’s a tiny moment in the billion-year stellar evolution of the star, yet it’s precisely such moments that help us understand how the densest objects in the Universe live.