Imagine a spinning top the size of a city, weighing more than the Sun and making hundreds of revolutions per second. That's a neutron star — the remnant of an exploded star. Occasionally, its rotation suddenly speeds up, as if something inside has switched. Astronomers call these jumps glitches and suspect that invisible vortices in the star's superfluid interior are to blame.

The interior of a neutron star resembles a layered cake. On top is a solid crust, and deeper down is a liquid core, but this liquid is unusual: it flows without any friction. This is superfluidity. The rotation of such a liquid breaks up into tiny vortex filaments, like whirlpools in a river, but each filament carries a precisely measured amount of rotation. At the crust-core boundary, two kinds of filaments meet. Some resemble ordinary vortices with an integer winding number, while others are half-integer, carrying half the rotational quantum.

The authors of the new study tackled the equations describing both vortex types and simulated their encounter on a computer. They found that half-integer vortices stick to an ordinary one like iron filings to a magnet. The attraction was so strong that it could yank vortices out of their pinned locations. In a real star, this would look like a sudden shift: a bound triplet of vortices breaks free from its anchor, giving the crust a kick that speeds up the star's rotation.

This mechanism explains why glitches come in such a variety: from tiny tremors to sharp jumps. It all depends on how many vortices are stuck together and how firmly they were attached to the crust. It turns out that the heart of a neutron star works like an intricate mechanism where quantum forces govern the motion of an entire star. And the spinning top we started with keeps on spinning — only now we have a better idea of what gives it a push from within.