Pulsars: How a Neutron Star Keeps Time

A neutron star is the compact remnant of a collapse

When the core of a sufficiently massive star collapses, it can leave behind a neutron star. Much of the original star's outer material can be thrown out in a supernova. The remnant packs a mass comparable to the Sun's into an object only tens of kilometres across. That is a scale comparison, not a claim that every neutron star has the same mass or radius.

Reference: NASA Goddard: Neutron Stars and Pulsars

The beam sweeps across us as the star spins

A spinning, magnetized neutron star can produce beams of radiation. When a beam crosses our line of sight, a telescope measures a pulse. The lighthouse analogy is about geometry: a source can emit even when its beam points away from us. Not seeing pulses does not rule out a neutron star, and not every pulsar is detected in the same wavelength band.

Reference: NASA Goddard: Neutron Stars and Pulsars; NASA Hubble: Pulsars

Convert a period into a rotation rate

A pulsar with a measured spin period of 0.25 seconds turns four times each second. Look for repeating structure before counting every bump in a pulse profile as a separate turn; more than one feature can recur in a single cycle. Timing uses repeated measurements, and astronomers can measure changes in rotation over longer intervals rather than treating every pulsar as a perfectly unchanging clock.

Reference: NASA Goddard: Neutron Stars and Pulsars; NASA Hubble: Pulsars

Ask what produced the plot

A pulse profile may combine many rotations to bring out a weak signal. A colored drawing of a beam is often an illustration, not a direct photograph of the star's magnetic field. Check the wavelength band, time scale, and whether you are looking at a single burst, an averaged profile, or a fitted timing model. They answer different questions about the same source.