But the regularity does have its limits. The same magnetic fields that power the pulsar produce a bit of drag as they sweep across the environment, gradually slowing the pulsar down. And theorists have proposed that neutron stars can "glitch," experiencing a sudden speed-up. This occurs due to movement in the star's interior, which can exchange momentum between the superfluid there and the crust surrounding it.
The event lasted just a fraction of a second and was presaged by a weak and very broad pulse. Ninety milliseconds later, when the next pulse was expected to arrive, nothing happened. The next few pulses were weak and had little indication of the strong polarization that was seen in the pulses that arrived before the glitch. Checking through 100,000 pulses that were recorded during their observations showed there was nothing like this behavior in the records.