Magnetars: On the boredom induced by magnetic fields

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The magnetic field around a bar magnet. Source: https://upload.wikimedia.org/wikipedia/commons/5/57/Magnet0873.png

Everybody remembers them from school, surely, the little pieces of iron on a surface that align in weird shapes when you put a magnet on them. We all remember that – as boring, why-do-I-have-to-learn-about-this-boring.

As follow-up to my last text where I ended up mentioning our trip to Abisko, I thought I would get a little more into that whole magnetic field thing, mainly because some of you still found the idea of magnetic fields being of interest beyond the demagnetization of credit cards rather surprising.

In Abisko, my colleague Robert of Spaceship Aurora and I talked about the Earth’s and the Sun’s magnetic fields. As mentioned before, the Earth’s magnetic field is rather weak comparatively, but strong enough to deflect most of the solar wind particles thrown at us by the Sun. Whatever is not deflected, creates a wonderful show on the night sky, Aurora Borealis. Not bad, is it?

Yes, but those magnetic fields are still rather abstract interactions, you may (and some did) say. The active part in all of this is played by the particles who crush into Earth’s defense system and carry the solar wind’s magnetic field. So, even though magnetic fields are life-savingly important to us, they don’t really feel interesting.

What about the Sun? On it the biggest explosions in the solar system take place, so called solar storms, which are connected to X-ray events called solar flares. Solar storms come to be when the Sun’s magnetic field turns in on itself and becomes compressed to the point of snapping.

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The Sun’s intricate magnetic field. Source: NASA (http://science.nasa.gov/media/medialibrary/2010/12/13/locations.jpg)

Yes, but here the driving force is differential rotation, you say; it is the fact that the solar gas or plasma rotates faster at the equator than it does at the poles. So, it is the weird rotation that is interesting, not the dull magnetic field.

Alright, I hear you. I must admit that you are rather a difficult case, as I believe both aurora and solar flares to be impressive, and they are controlled by corresponding magnetic fields, but still, I think you are looking for a more active, creative (or, for that matter, destructive) magnetic field.

I have something for you, if you do not mind:

Neutron Stars.

Neutron Stars are the densest things this side of a black hole event horizon. Their size is comparable to that of a small city – around 10 to 20 kilometers in diameter – while having a larger mass than the Sun. They consist almost entirely of neutrons and are protected from further collapse by quantum physical effects balancing out the immense force of gravity.

This is where things get interesting (first now!?!). I wrote they consist almost entirely of neutrons. That is wrong. 20 % of the Neutron Star consists of electrically charged protons and electrons; so the moment our star rotates, there will be a magnetic field. Actually, it is not quite as simple as that either. The magnetic fields of Neutron Stars are composed of frozen-in remnants of supernova magnetic fields and dynamo-driven, rotational magnetic fields of the kind described above. In fact, a Neutron Star’s magnetic field can be several trillion times stronger than the Earth’s, or the Sun’s for that matter.

Under, ahem, normal circumstances that magnetic field is rather predictable. In Pulsars it radiates energy from the star in the form of X-rays, and does so constantly for a significant amount of time.

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Artist’s conception of a magnetar. Source: NASA (https://upload.wikimedia.org/wikipedia/commons/d/d6/Magnetar-3b-450×580.gif)

When the magnetic field of a Neutron Star reaches several quadrillion times the strength of the Earth’s or the Sun’s, we call the object in question a Magnetar. Strangely enough, Magnetars rotate slower than ordinary Neutron Stars. Their magnetic fields are dominated by the supernova leftover component and stay the way they are due to superconduction inside the star – probably. It is all a bit fuzzy and not well understood.

Quite frankly, Magnetars and their magnetic fields are the most boring thing you will encounter in the whole universe, and I am not facetious at all now. Your attitude has definitely not made me facetious at this point.

Let me give you an example in order to summarize: SGR 1806-20, as it is called is the closest Magnetar we know of. It lies in the constellation of Sagittarius on the other side of the Milky Way, around 50 000 light years from the Solar System.

Now get this: Its diameter is around 20 km, its rotation speed is once every 7.5 seconds. The magnetar’s surface, which is only 10 km from the centre turns at a whopping 30 000 km/h, which, all things considered, is a slow rotational speed. Together with the frozen-in component, the magnetic field of SGR 1806-20 then becomes 100 000 000 000 Tesla.

Eat your heart out, I might add at this point.

What such a magnetic field could do besides demagnetizing credit cards? I am sure glad you asked as it seems I have finally gotten your attention. This is what such a magnetic field could do:

If the Earth were to come to around a 1000 km’s distance to this (or any other) Magnetar, the strength of its magnetic field would render your bioeletromagnetics as it is called, non-existent. The atoms in your body would break down and you, as a person, would dissolve into a slush of subatomic particles, a demagnetized human, if you will.

That is about the most boring thing ever, right?

Listen, forget credit cards. Nature is not boring; she is awesome they way she is, and a lot of her is conducted by electromagnetic fields. You may blame your teacher for not really telling you all about it when you were in school; or you may look in the mirror and tell yourself that you are just, well anything from not really interested to plain lazy. Nobody is holding you back from realizing this:

From touching stuff to TV, macroscopic nature is all about (electro)magnetic fields.


2MNiqx7k_400x400Alexander is a physicist, teacher and science communicator who is currently working at the Norwegian Centre for Space-related Education at Andøya Space Center in Norway. Even though, in his case, work and play do overlap, the content on this webpage is entirely private. You can follow Alexander on Twitter, Facebook and Google +

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