Similarities between Neutron Stars and Superfluid Helium

One of the most counterintuitive behaviors of neutron stars is the occasional ``glitch" in their rotation, where the angular velocity abruptly speeds up. The accepted explanation is that the additional angular momentum comes from the superfluid interior of the star, which can temporarily couple to the outside crust when superfluid vortex lines depin. To the extent that the physics involved is generic to superfluids, we expect same phenomenon in superfluid helium, where controlled experiments are possible. We discuss such an experiment, with a levitating bucket of helium standing in for the neutron star. We observe rotational glitches, which occur only when the bucket is filled with superfluid helium. We will describe the apparatus and the properties of the measured glitches.