Question: how many pulsar stars have you found and what do they look like?

Evan Keane answered on 12 Jun 2011:

Personally I have found about 20 pulsars, and I am always interested about how “my” pulsars are doing – it’s like they are my babies or something! 🙂

As to what they look like – this is an excellent question! Usually you cannot see pulsars in visible light (like with your eyes) but they are easier to see in radio waves. You might be familiar with the visible night sky but if you had X-ray, infrared or radio vision what you would see would be totally different! If you want to know what I mean check out this cool webpage which shows the Universe in Gamma-ray, X-ray, UV, optical, infrared and radio!

http://dev.chromoscope.net/?l=0.0879&b=0.0000&w=2.00&o=g,x,v,a,f,m,r&z=3

Well anyway, us humans don’t have radio vision (I can tell you why if you like!) but we can make radio telescopes which do. If you have a satellite dish this is basically a small radio telescope but usually astronomers use much bigger ones – like the Lovell Telescope at Jodrell Bank (it’s huge!). When you use these telescopes to look at the sky, in several places you get a repeating signal. We get a strong pulse for a few milliseconds, and then nothing, and then a second or so later another pulse, and it repeats again and again. This is a pulsar! 😀

Why is this exciting? There are so many reasons! Firstly, we should ask what can be making that repeating pulse every second (and there are other pulsars which repeat much faster too)? If you think about it a bit the only possibilities for a repeating signal are (1) an eclipse, (2) a star which is oscillating (I mean growing and shrinking again repeatedly) and (3) something that is spinning. Do you know what an eclipse is? It is when something comes in front of a star or planet (or anything!) and blocks it with its shadow. If you want to see an eclipse there is one this Wednesday when the shadow of the Earth will block out the Moon! Maybe a pulsar is a star which is being eclipsed repeatedly by something’s shadow …. hmmm well it turns out that you can’t have an eclipse every second – it’s way too fast! This eclipse happening on Wednesday won’t repeat for a few years. Imagine how close to the moon we would have to be to eclipse it every second – it’s not possible! Ok, what about the second possibility – an oscillating star, beating in and out. Well it turns out that no star can do this faster than every 10 seconds but pulsar pulses repeat much faster than that! Now we are on the final possibility – that the repeating pulse we see from a pulsar is something spinning and giving out a signal like a light house. Every time the light swings in front of our telescope we see a pulse and then another one when it has spun around again, and again, and again …

So pulsars are stars that spin very quickly and they emit a signal like a lighthouse and we see the light from this lighthouse once every time it spins! Oh ya, I forgot to mention some other cool things! A normal star like the Sun can’t spin that fast (it would explode!) so pulsars have to be really small – actually a pulsar is only about the size of London – that is very small for a star! It is a good thing that the lighthouse signal is so very bright as otherwise we would never seen such a small star from a million billion miles away!!

Pulsars spin at all different speeds. If you want to hear “the sounds of pulsars” then you can go to this webpage and press play beside each one.

http://www.jodrellbank.manchester.ac.uk/~pulsar/Education/Sounds/sounds.html

The first one is a slow one and it spins every 0.7 seconds and it sounds like a heart-beat. (Actually I observed that yesterday with a new telescope in Germany and it is still beating away!) But if you listen to Vela or the Crab pulsar (I can tell you why it is called the Crab if you are interested!) they spin much faster and we get so many pulses that they sound like machine-guns! Then if you listen to the fastest pulsars on that page they spin so fast – hundreds of times every second! – that you can’t even hear all the separate pulses and they just sound like a mosquito! As you can see (or should I say hear!) pulsars spin at all different speeds! Actually I am interested to know what you think they sound like – please tell me what they sound like to you!

You probably understand now from listening to these that pulsars have a regular beat. Actually it is very very reliable and astronomers actually use the beats like the ticks of a clock. It is like we have super clocks in space! And this is one way we use them – as clocks to measure time very very far away! If Einstein knew about pulsars he would be very happy as clocks in space are exactly the kind of thing he wanted to do tests of his work! Unfortunately he died before the first pulsar was discovered, but today astronomers use pulsars to test his work.

🙂

Evan