Three years of staring lets scientists capture a neutron star “glitch”
Neutron stars are the most dense form of matter in our Universe (black holes cram more stuff into a smaller space, and it's not clear if that stuff is still "matter"). A neutron star is produced by the collapse of a stellar core, which crams a bit more mass than our Sun into a sphere about 20 kilometers across.
At this density, matter does strange things. Models based on theoretical considerations suggest that there's a distinct "crust" that sits atop a superfluid of subatomic particles, but it's not like we can visit one and confirm this. Now, researchers have done the next-best thing: they've arranged for a telescope to stare at a neutron star for three years, waiting for it to undergo a "glitch" in its normal behavior. The results give us one of our first direct tests of competing models for what's beneath the surface of a neutron star.
While a neutron star is composed primarily of neutrons (duh!), there are also protons present in its interior. All the particles there form a superfluid, which can flow without any friction. The flow of these charged particles inside the star can create an intense magnetic field, one that can accelerate charged particles near the star and cause them to emit photons. The rapid rotation of the star means that these jets of charged particles sweep a large area of space with the photons they produce. On Earth, we see this as a flash of light appearing from the same source many times a second—a pulsar. The pulses of photons that give these stars their name arrive with such regularity that we've used them as an extremely precise test of relativity.