(Submitted January 14, 1998)
If neutron stars consist of only neutrons, how is it possible that they
have a magnetic field? I am just a hobbyist, but I thought that the presence
of electrons is necessary for a magnetic field.
This is a good question. The answer, I think, is that neutron stars
are not pure neutrons. If they were, the neutrons would decay.
A small (10%) fraction of electrons and protons are present
which provide a rate of neutron formation via inverse beta processes
which balance the neutron decay. These protons are highly degenerate
and superconducting, so the magnetic field is frozen into the
neutron star. The origin of the field is probably the parent star,
although various schemes have been suggested for generating fields
in neutron stars.
I hope this helps,
for the Ask an Astrophysicist team