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Converting angular momentum into gamma rays seems amazing to me! How does it do it? Presume something to do with magnetic fields....why does it even have a magnetic field? Its made of neutrons so theres no charge rotating?

BVES
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  • Related, for the question about magnetic fields: http://physics.stackexchange.com/q/207807/56299. But you seem to have two questions here; I would advise splitting them up. – HDE 226868 Nov 04 '16 at 21:15

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First of all, every star has a magnetic field, though it is in general very weak. The magnetic field gets created by convection inside a star. Depending on its mass a star can consist of different layers where convection, radiation or conduction happens. Stars with masses higher than 0.5 solar mass all have a convective core which generates a magnetic field. If you want to know more about this, you should consult a textbook on Stellar Structure.

Neutron stars are the remains of very massive stars, so they already have a significant magnetic field. With a supernova explosion the star collapses and the field lines get squeezed together producing even higher magnetic fields. Now a neutron star consist mostly of neutrons (obviously) but there is a thin outer layer were protons, electrons and iron atoms are present. They are the leftovers of the explosion bound again to the star. The high magnetic field and rotation give rise to a electric current on the surface. This in turn accelerates the protons and electrons along the field lines giving rise to all kinds of radiation.

Note however, that the acceleration mechanisms of GRBs are poorly understood. This is still active research and there are several possible explanations for it.

  • Thats really interesting - thank you for the great answer. So the magnetic field of the neutron star is retained from when it was a star, i hadnt thought of that. Fascinating, thank you. – BVES Nov 04 '16 at 21:16
  • I would have suspected that in neutron stars the intrinsic magnetic moment of the neutrons plays a role in its magnetic field. – freecharly Nov 05 '16 at 02:51
  • My explanation is that of an astrophysicist. It is based on the fact that the field lines get caught by the collapsing plasma (frozen-in theorem, a pretty good approximation) and squeeze together. However, there are theoretical physicists proposing models based on superfluidity and magnetic moments for the origin of the field. Some of these account pretty well the observed magnetic fields of e.g. magnetars. Maybe it is a combination of both explanations, maybe it is something else (dynamo effects due tyo differential rotation). In any case, the real origin is still unknown. –  Nov 05 '16 at 10:50
  • What does this have to do with GRBs? I think it's worth pointing out that 1) the specific methods by which radiation is produced are very poorly understand, and 2) that there are still significant amounts of charges particles in neutron stars---only something like 60% (ish) are neutrons. – DilithiumMatrix Nov 10 '16 at 22:12