Bo Zhang

A vortex in a superfluid gas is like a whirlpool in a sink: the fluid swirls around an empty core. If you spin such a vortex three times harder than usual, it won't hold: it breaks into three separate whirlpools, much like a thick stream of water splits into droplets.

In a solid, atoms vibrate, transmitting sound. Sometimes this wave doesn't run straight but curls into a spiral, like a corkscrew entering a cork. In ordinary crystals, such 'sound vortices' are known, but in magnetic materials they had long eluded detection.

Two spinning tops whirl so close they nearly touch. One is scorching blue, the other dim white. Together they complete a full orbit in twenty hours. This is the pair Feige 64: a blue star with a mass of just a third of the Sun's, and a white dwarf, the cooled core of a former star, one and a half times heavier than our Sun. The blue star seems too hot for its mass.