Spin dynamics and magnetic effects in neutron stars and relativistic jets.Neutron stars are the collapsed cores of massive stars, packing more mass than the Sun into a sphere about the size of a city. They are extreme objects with intense gravitational and magnetic fields, and they spin incredibly fast—some completing hundreds of rotations per second. The spin of a neutron star is not just a simple rotation; it is intimately linked to its magnetic field and the surrounding environment. This spin dynamics can be affected by the accretion of matter from a companion star, by the emission of gravitational waves, or by the interaction of the star's magnetic field with the surrounding plasma, leading to phenomena like pulsar glitches and the launching of relativistic jets.
Neutron stars were first theorized in 1934 by Walter Baade and Fritz Zwicky, and the first pulsar was discovered in 1967 by Jocelyn Bell Burnell and Antony Hewish. The detailed study of their spin dynamics has been a central theme in astrophysics since then.
The spin of a neutron star is governed by conservation of angular momentum, but it is also influenced by its strong magnetic field. The magnetic field, which can be a trillion times stronger than Earth's, forces charged particles in the surrounding space to co-rotate with the star, creating a magnetosphere. As the star spins, it emits beams of radiation from its magnetic poles, which we observe as pulses (hence 'pulsars'). The spin can change over time due to the loss of energy through magnetic dipole radiation and particle winds, or it can suddenly speed up (a 'glitch') due to the transfer of angular momentum from the superfluid interior to the crust. In binary systems, the spin can be accelerated by accreting matter from a companion, which also shapes the jets of particles ejected along the rotation axis.
The precise timing of neutron star pulses is used in pulsar timing arrays to detect gravitational waves, and their extreme conditions serve as natural laboratories for testing theories of dense matter and magnetohydrodynamics.
A single neutron star can spin at a rate of over 700 times per second, meaning its surface moves at a significant fraction of the speed of light.













