Pulsars are rotating neutron stars that emit a beam of electromagnetic radiation. As the star rotates, the beam sweeps across the sky like a lighthouse beacon. When the beam aligns with Earth, we see a pulse of radio waves or X-rays. Pulsars were first discovered in 1967 by Jocelyn Bell Burnell and Antony Hewish while they were searching for evidence of extraterrestrial intelligence.
Pulsars are incredibly dense objects, comparable to the density of an atomic nucleus. They have extremely strong magnetic fields and rotate at rates of up to hundreds of times per second. The combination of these two properties makes pulsars some of the most extreme astrophysical objects in the Universe.
The mechanism that powers pulsar emission is not fully understood, but it is thought to be linked to their strong magnetic fields. As charged particles move through the magnetosphere, they are accelerated and emit radiation. This process amplifies the signal as it travels along the field lines towards Earth.
Pulsars can be used as precision tools for a variety of astronomical measurements. For example, by timing how long it takes for pulses to arrive from different parts of a pulsar’s magnetosphere, we can map out its structure in detail. By observing how a binary pulsar system evolves over time, we can test Einstein’s theory of general relativity with unprecedented accuracy. And by studying millisecond pulsars – which spin hundreds of times faster than normal – we can probe conditions in matter that are otherwise unattainable on Earth (such as super-high densities and temperatures).