Mar 24, 2023
Neutron stars are rapidly rotating dense balls of nuclear material formed from the gravitational collapse of the cores of giant stars. Generally, we cannot see them because they are very small and don’t emit much thermal (heat) radiation. But one special class of neutron stars, called pulsars, have jets of radiation that pass by Earth once per rotation, creating a lighthouse effect whereby they appear to us as pulsating stars (hence the name "pulsar"). Many models have been proposed to explain the nature of pulsar emissions. The most basic one is called the “rotation-powered” model, where particles accelerated along the pulsar's magnetic field lines are dragged and rotated around by the spin, powering the observed synchrotron radiation and exerting a torque on the pulsar that causes it to slow down over time (known as magnetic braking). While this model allows us to approximate some pulsar parameters, such as the strength of the surface magnetic field, details of the emission process are unaccounted for. Other plausible models have been proposed, which we'll be able to better constrain using data from the Imaging X-Ray Polarimetry Explorer (IXPE), a small-mission NASA satellite launched in December 2021.