A pulsar is a specific type of neutron star, so let’s start there. Neutron stars are made when a star slightly more massive than our Sun dies and goes supernova. In a supernova event, large amounts of radiation explodes out from the star, causing a brilliant flash of light which can sometimes outshine an entire galaxy.
At the same time, gravity causes the core of the star to collapse into a neutron star. Neutron stars are made almost entirely of neutrons (hence the name), and are MUCH smaller in size than their parent stars. Since a neutron star keeps most of the angular momentum from its parent star but has a significantly smaller radius, it spins with very high rotational speeds. These speeds typically lead to rotational periods ranging from milliseconds to seconds.
In addition to spinning quickly, neutron stars also commonly have very strong magnetic fields that can accelerate electromagnetic particles and eject them out along the magnetic poles of the star at extremely high velocities. This results in neutron stars emitting spinning beams of radiation, or light.
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When a neutron star happens to have its rotation axis oriented so that one or both of its beams of radiation points toward Earth as it rotates, it is called a pulsar. The name pulsar is a combination of the words “pulsating star”, since the action of the beam of radiation passing over Earth is experienced by us as a pulse of light, much like how one sees pulses of light from a lighthouse.
These pulses are observed on Earth at regular intervals which are associated with a pulsar’s period of rotation. The faster a pulsar is spinning, the more pulses are measured on Earth in a set amount of time. This is demonstrated in the above video, with faster-spinning (i.e. more rotations per second) pulsars creating sounds, or chirps, more often than slower-spinning pulsars.
The reason that you can hear many pulsars is because they emit energy in radio wavelengths. Just like how your radio at home can pick up radio signals and turn them into sound, the radio waves from pulsars are detected here on Earth with radio telescopes – large circular dishes similar to the small ones used on top of people’s houses to receive TV signals from satellites – and converted into sound. The chirping or drumming sound that you hear in the video is actually created by the pulsar’s spinning beams of energy!
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