A globular cluster, a dense swarm of hundreds of thousands of stars, plows through a galaxy like a bullet through water. In ordinary dark matter (the invisible mass that holds galaxies together), it should quickly lose speed due to dynamical friction. But in the dwarf galaxy Fornax, several such clusters have yet to fall to the center. Astronomers call this the 'timing problem.'

The authors of the study considered ultralight dark matter — hypothetical particles 10²⁵ times lighter than an electron. In the galactic center, such matter doesn't just form a cloud but a vortex state: a giant rotating tangle, like a tornado. Numerical experiments showed that if a cluster moves along the vortex's rotation and their speeds are similar, the drag force drops by a factor of several. The reason is resonance: the matter doesn't have time to rearrange and barely pulls the cluster back.

The calculations were applied to the Fornax galaxy — a satellite of the Milky Way located 460 thousand light-years away. It turned out that the vortex state naturally explains the slow infall of its clusters. Thus, the rotation of the galaxy's invisible core becomes the key to the orbital history of star swarms.