Friday, July 23, 2010

The Sounds of Pulsars

Here's a little treat for the weekend -- take a listen to the sounds of the pulsars!

Of course, these stars aren't really emitting sound, but rather high energy beams of radiation that are detected on Earth by radio telescopes. Radio signals received by these telescopes can be converted into images, but we can also listen to them! (Remember that radio waves are just one of several different kinds of light).

Pulsars are a special brand of neutron star. As the leftover cores of supernovae, they are extremely dense and small, and rotate at incredible speeds, spitting out energetic beams of radiation along their magnetic poles. When one of these beams passes by the Earth, we see it as a flash, like a lighthouse (in fact, when the first pulsar was discovered, some astronomers thought it might be a sort of cosmic lighthouse, left behind by extraterrestrials). So when we listen to the signal of a pulsar, we hear lots of pulses at regular intervals.

Just how fast are the pulsars spinning? Well, it varies. But check out this website and you can hear how fast! Compare this pulsar, spinning about 1.4 times a second, with this one (the Crab Pulsar), spinning about 30 times a second, and this pulsar, spinning about 642 times a second! (Make sure your volume is not too high, because that's one energetic pulsar).

It's one thing to look at a number and be amazed (that third pulsar has a rotational period of 0.00155780644887275 seconds ... what precision!), but I think listening to it spin makes it more real, in a way. Just imagine this neutron star, 10 or 15 kilometers across, spinning 642 times a second! It's enough to make your head spin.


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