How are pulsars detected by radio telescopes?

Pulsars are detected by radio telescopes because they function as rapidly spinning neutron stars that emit intense beams of electromagnetic radiation from their magnetic poles.12

Because a pulsar's magnetic poles do not align with its rotational poles, the star's rotation causes these radiation beams to sweep through space like a lighthouse beam. When these beams regularly sweep past Earth, ground-based radio telescopes—specifically designed to record very rapid fluctuations in radio sources—detect an evenly spaced series of pulses.12

The interval between these pulses, known as the period, varies significantly between different pulsars, ranging from several seconds to mere milliseconds in the case of "millisecond pulsars". By carefully timing these pulses, astronomers can study the pulsar's rotation, detect changes in its period, and even identify the presence of companion objects or test theories of gravity.13