As the neutron star spins, charged particles are accelerated out along magnetic field lines in the magnetosphere (depicted by the light blue cones). This acceleration causes the particles to emit electromagnetic radiation, most readily detected at radio frequencies as a sequence of observed pulses produced as the magnetic axis (and hence the radiation beam) crosses the observer's line of sight each rotation. The repetition period of the pulses is therefore simply the rotation period of the neutron star. The moving ``tracker ball'' on the pulse profile in the animation shows the relationship between observed intensity and rotational phase of the neutron star.
Neutron stars are extremely stable rotators. They are
essentially large celestial flywheels with moments of inertia
. The rotating neutron star model, independently developed by
Pacini and Gold in 1968 [184,
85], predicts a gradual increase in the pulse period as the
outgoing radiation carries away rotational kinetic energy. This
model became universally accepted when a period increase of
36.5 ns per day was measured for the pulsar in the Crab
nebula [202], enabling Gold [86] to show that a rotating neutron star with a large magnetic
field must be the dominant energy supply for the nebula.
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Binary and Millisecond Pulsars at the New Millennium
Duncan R. Lorimer http://www.livingreviews.org/lrr-2001-5 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |