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From my understanding of pulsars, pulsars do not produce sound, but radio telescopes can record the radio waves they emit, which can be interpreted as sound. The radio waves are electromagnetic waves, similar to light, not sound. The waves are beamed out along the pulsar's magnetic poles, and the Earth receives pulses of radiation as the beam crosses.

However, this means that this is not the sound of pulsars and it's just the interpretation from our side and how our machinery detects it and interprets it for our understanding. The first recording of pulsars recorded a "thumping" or "knocking" sound by our machinery.

My question is does pulsar stars have their own sound coming out of them? Is it the same "thumping" sound that we captured? Please clarify this.

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    $\begingroup$ There are related questions on our sister site: physics.stackexchange.com/q/413929/123208 $\endgroup$
    – PM 2Ring
    Commented Mar 26 at 17:42
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    $\begingroup$ How do you define sound in the vacuum of space? The way fighters sound in Star Wars? ;-) $\endgroup$
    – U. Windl
    Commented Mar 27 at 14:02

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Sound is the vibration of matter. Sound can only travel in a medium like air or water. So no sound can come across space. Pulsars do have a very shallow atmosphere, but it is only a few microns deep (according to some models)

The cause of the pulsing is the rotation of the star. It is constantly putting out energy in two beams, but these rotate with the star and we detect the pulses as the beam regularly passes us.

But it is totally reasonable to convert the radio waves that do travel across space to sound. Humans are not naturally able to sense radio waves (ems individuals notwithstanding) so the radio waves would have to be converted into something that might be a graph (like the one used on the Joy Division album) or it might be an image, but to allow humans to get a sense of what the radio signal is like, sound is a very natural choice.

It sounds like a "knocking" because each pulse is quite sharply defined along the time axis, but contains a mix of radio frequencies. So this sound is meaningful, not arbitrary. Like a terrestrial radio station, no sound actually travels from the station to your radio. But unlike a radio station, the source of the radio waves is not a sound that has been changed to an electrical signal by a microphone, nor any natural analogue of that.

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  • $\begingroup$ So if anyone says that pulsars have a knocking sound, it's not true right? It's just the conversion of radio waves into something that we can understand right? $\endgroup$
    – Ganit
    Commented Mar 25 at 9:02
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    $\begingroup$ You seem to be trying to prove some point. Of course, no sound travels through space. But the conversion to sound is not arbitrary. This is a meaningful conversion. see my last (edited) paragraph The atmosphere is transparent to radio waves, so there is not much attenuation. $\endgroup$
    – James K
    Commented Mar 25 at 9:09
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    $\begingroup$ @Ganit Almost all astronomy data outside of an actual optical telescope is "just" a conversion of something we can't sense into something we can. We convert infrared light into visible light, we convert radio into images or sounds or columns of numbers. Our senses are made to function in the very limited realm of the Earth's surface, and beyond that realm we have to convert the data. A pulsar doesn't make a sound as such, but it emits energy, and playing back that emission as a sound wave is no more false than charting it on a graph. It's all just interpretations of the received signal. $\endgroup$ Commented Mar 25 at 20:28
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    $\begingroup$ "it is totally reasonable to convert the radio waves that do travel across space to sound" – And, of course, AM radios do just that, all the time. $\endgroup$ Commented Mar 25 at 23:36
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    $\begingroup$ Minor point: sound can transmit in interstellar space, but only wavelengths much longer than the mean free path of particles in the interstellar medium, which is of order AU, unfortunately larger than pulsars and people. $\endgroup$
    – Sten
    Commented Mar 26 at 17:08
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My question is does pulsar stars have their own sound coming out of them? Is it the same "thumping" sound that we captured?

Those audio recordings result from transforming the signals received via electromagnetic devices (telescopes) into sound. Sonification has become a widely used scientific approach for communicating and understanding data of all kinds. The linked article describes why. Quoting from the authors (emphasis mine),

Compared to vision, the ear is better at perceiving time-based information, patterns and transient changes and does not require us to be oriented in the direction of the sound. Furthermore, hearing is always active, which makes it useful for monitoring alarms and continuous data streams, whereas an event may be missed with visual inspection due to blinking or looking away momentarily. An effective example of audible inspection of data used in the scientific context is the Geiger Counter, which clicks in response to invisible radiation levels. Therefore, sound has the potential to be a more effective alternative to visualisation for exploring time-series data and for live data monitoring of transient events whilst occupied with different tasks.

So the "sounds" of pulsars that are presented on many websites are not pulsar sounds per se. They are data recorded by telescopes (which receive data using electromagnetism) that have been transformed to sound. Geiger counters were developed about 100 years ago. The radioactive decays they detect are not sound. The clicks emitted by a Geiger counter are a form of sonification, as are the "sounds" of a pulsar.

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    $\begingroup$ Sonification can even be used for sound. The ultrasonic chirps of bats and the subsonic songs of whales have been transformed in frequency so that we humans can hear those sounds. $\endgroup$ Commented Mar 26 at 15:55
  • $\begingroup$ Thanks for the explanation. $\endgroup$
    – Ganit
    Commented Mar 26 at 17:35
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    $\begingroup$ Surely there are mechanical vibrations over a huge range of frequencies in a pulsar. However, it's rather tricky getting close to a pulsar with a stethoscope. ;) As you approach it, you tend to get spaghettified, assuming you don't get vaporised by the heat and radiation. And when you land on it, the gravity tends to squish you into an atom-thick paste. $\endgroup$
    – PM 2Ring
    Commented Mar 26 at 17:47
  • $\begingroup$ Is it possible to run a computer simulation, a finite element 2D or 3D model of a pulsar placed in an oscillating medium (for example air), and calculate the vibrations of this air medium at any point and interpret how it might sound? $\endgroup$
    – ayr
    Commented Apr 1 at 7:21
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Space has no sound since it has no air as James K said, and sonification does exist, as David Hammen said. Theoretically, if you somehow took a pulsar and put it into an atmosphere of air, then there would be sound. You (and everyone else) would also probably die due to it's gravity and radiation, sadly.

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  • $\begingroup$ Neutron stars have a radius around 10 km or so. $\endgroup$
    – PM 2Ring
    Commented Mar 27 at 2:21
  • $\begingroup$ This answer doesn't provide anything new $\endgroup$ Commented Mar 29 at 13:46
  • $\begingroup$ Is it possible to run a computer simulation, a finite element 2D or 3D model of a pulsar placed in an oscillating medium (for example air), and calculate the vibrations of this air medium at any point and interpret how it might sound? $\endgroup$
    – ayr
    Commented Apr 1 at 7:21

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