Figure 2 shows an animation depicting the rotating neutron star or “lighthouse” model. As the neutron
star spins, charged particles are accelerated out along magnetic field lines in the magnetosphere (depicted
by the light blue cones). The accelerating particles 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
GIF movie showing the rotating neutron star (or “lighthouse”) model for pulsar emission.Animation designed by Michael Kramer.
Neutron stars are essentially large celestial flywheels with moments of inertia . The
rotating neutron star model [242, 105] predicts a gradual slowdown and hence an increase in the pulse
period as the outgoing radiation carries away rotational kinetic energy. This model became universally
accepted when a period increase of per day was measured for the pulsar in the Crab nebula ,
which implied that a rotating neutron star with a large magnetic field must be the dominant energy supply
for the nebula .