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The Question

(Submitted November 28, 2006)

Why are the magnetic field of a pulsar and the axis of rotation not aligned with each other? Doesn't a magnetic field get created because of the spinning matter that alignes itself with the axis? Why does it differ? My astronomy teacher didn't know the answer to this.

The Answer

It's an interesting question. How magnetic field is created and sustained in a normal star (like our Sun) is not fully understood yet. But one thing is clear: the magnetic field does not depend solely on the global spinning motion of the matter in a star. Rather, it depends on various other typess of motion. This is called dynamo effect. You can see
for a description of this effect in our Sun.

Now, when a star (much more massive than our Sun) collapses to a neutron star (pulsar), its magnetic field lines also become denser, and hence the magnetic field becomes stronger. In the process of collapse, magnetic field may get affected by turbulent motions of matter. Therefore, there is no reason why magnetic axis of a neutron star (pulsar) has to be aligned with the spin axis. Note that even earth's magnetic axis is not aligned with its spin axis.

Hope this helps,
Sudip & Koji
for "Ask an Astrophysicist"

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