* Period stability: Pulsars have remarkably stable periods, often with a precision exceeding that of atomic clocks. This stability is hard to explain with a pulsating star, as the internal mechanisms driving the pulsation would likely be subject to variations.
* Extremely short periods: The periods of pulsars range from milliseconds to a few seconds, far shorter than the pulsation periods observed in known variable stars.
* Narrow pulse width: The pulses emitted by pulsars are extremely narrow, typically lasting only a fraction of a second, which is incompatible with the broader emission profiles of pulsating stars.
* Polarization of radiation: Pulsars emit highly polarized radio waves, indicating a highly ordered and directed emission mechanism. This is difficult to explain with a pulsating star model.
These observations led astronomers to conclude that pulsars must be something entirely different. The breakthrough came in 1967 when Jocelyn Bell Burnell discovered that the signals were coming from rapidly rotating neutron stars with incredibly strong magnetic fields. These fields channel particles into beams that sweep across the sky as the neutron star rotates, producing the observed pulses.
Therefore, pulsars are not pulsating stars but rather rotating neutron stars with highly focused beams of radiation. This is now a well-established theory, supported by numerous observations and theoretical models.
