A Brief Introduction to Pulsars

A long time ago on this site we briefly discussed neutron stars and white dwarfs when talking about stellar deaths. Both of these stars are compact, and hence despite being small they’re immensely heavy! Pulsars are an extension of these two stars that we’ll be discussing today.

PSR B1509−58, X-rays in Gold by CHANDRA, everything else by WISE

Pulsars themselves are normally a neutron star, but sometimes a white dwarf. The name is a shortened version of Pulsating radio source, and were discovered by Dr Jocelyn Bell Burnell in the late 1960s as part of her PhD. I actually met her when I was about 17, and she is such a humble and lively person to be with!

These stars are compact stars which emit two beams of electromagnetic radiation. These beams aren’t usually aligned with the rotation axis of the star, so when the star rotates the beams sweep around like a lighthouse. From our perspective, on Earth, we see little pulses of radiation as the beam points towards us.

Artist’s Rendition of a pulsar. Credit: NASA

The time between each pulse can range drastically! The most extreme pulsars have periods of a couple milliseconds, meaning the star is spinning at a madly fast rate! These select few are called millisecond pulsars, while the rest are ordinary pulsars. These “normal” stars will have a period of around a second.

Crab Nebula in the X-ray. Credit: NASA

One of the most famous pulsar (although people forget it) is the pulsar in the Crab Nebula! This pulsar is so young that us humans even got to witness its birth! It’s a speedy pulsar, with a pulse period of about 33 milliseconds and rotation rate of 30 times a second! I can’t even imagine something spinning that quickly! More information in this pulsar is available here.

Observations take a long while. A lot of analysis of the data is required to sift out noise and find a periodic signal. Furthermore, to be certain it’s a pulsar you also need a lot of these pulses, hence a lot of time recording data. You can hear these pulses if you convert the data to electrical pulses and play it through a speaker, but Jodrell Bank has already done the hard work for you here.

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