New model may explain lack of slower-spinning x-ray pulsars

Ars Technica : Pulsars are rapidly rotating neutron stars, which are the remains of stars that have gone supernova. Pulsars that have exceptionally strong magnetic fields emit light in the x-ray and gamma-ray spectra. Because of the energy lost in emitting that light, x-ray pulsars should have a wide range of rotational periods, with older ones rotating more slowly and younger ones more quickly. However, all the x-ray pulsars that have been observed over the past 45 years have had periods between 2 and 12 seconds. A new model for neutron star structure proposed by José Pons of the University of Alicante in Spain and his colleagues may explain the lack of slower x-ray pulsars. They argue that a highly disorganized layer in a neutron star’s crust disrupts the magnetic field and transfers its energy into rotational energy. That energy transfer maintains the pulsar’s spin. The model predicts that that layer is a jumble of regions shaped like sheets, tubes, and wires—dubbed nuclear pasta—that formed as a result of the energy, pressure, and density of the star. Although there is no direct evidence that this structure exists, continued observations of x-ray pulsars may help better understand the narrow range of spin periods.