Milky Way Magnetic Fields Charted

eldavojohn writes "Using radio telescope data, scientists from around the world have plotted the Milky Way Galaxy's magnetic field in the form of Faraday Depth. From the article, 'For 150 years, scientists have measured cosmic magnetic field by observing the Faraday effect. They know that when polarized light passes though a magnetized medium, the plane of polarization turns. This concept is called Faraday rotation. The strength and direction of the magnetic field governs the amount of rotation that occurs. So scientists observe the rotation to investigate the magnetic fields' properties. Radio astronomers study the polarized light from distant radio source, passing through the Milky Way on the way to Earth, in order to measure our Galaxy's magnetic field. By measuring the polarization of the light sources at different frequencies, researchers can determine the amount of Faraday rotation.' In the future, radio telescope technologies like LOFAR, eVLA, ASKAP, MeerKAT and the SKA hope to provide enhanced Faraday rotation data so scientists can better understand turbulence in galactic gas and these galactic magnetic field structures."

Comments

It's a dupe

[Janek Kozicki]

And it doesn't mention the most important part: that they have improved a lot in the field of information processing & information theory, just to filter out the information from very noisy measurements. They developed a information Hamiltonian and information field theory, interesting stuff http://arxiv.org/pdf/0806.3474v3

dupe's here:
http://science.slashdot.org/story/11/12/07/1811216/new-all-sky-map-shows-the-magnetic-fields-of-the-milky-way

Why is important?

[EdIII]

I have never heard of measuring the magnetic field of a galaxy or celestial object.

Can an astrophysicist enlighten us on what you can learn with this information?

Re:Why is important?

[jo_ham]

It helps to understand the chemistry of interstellar space, and much of the information we don't actually know about, and post-big-bang conditions.

For example, the presence of the H3+ ion in diffuse clouds, where it has been detected so clearly exists there, but its formation processes as we understand them currently would suggest it would not form there (only in dense clouds), thus there's clearly a jigsaw piece missing. The current suggestion is that the diffuse clouds can have a "clumpy" consistency, with areas of much higher density. Things like galactic magnetic fields and other effects that can act on material in the clouds can help to explain things like this. (It may not answer the H3+ molecule question, but others like it).

Re:Why is important?

[rusty0101]

I'm not an astrophysicist, but I am aware of a few things that being able to map out a galactic magnetic field (or collection of fields) can be useful for.

We know that our knowledge of the makeup of galaxies is not complete, and knowing what the magnetic structure looks like can help point us at things that we may have missed. For example Magnatars are a variation of neutron stars that are very powerful magnetic objects. We know where some are based on observations of gamma ray emissions when their magnetic fields untwist (you will need an astrophysicist to explain why the twisting happens) but just their existence and movement within the galaxy should have an observable effect on the galactic magnetic field that may point us towards a better understanding of where and how many there are.

Additionally magnetic fields have an effect on, and are affected by the distribution of matter. So a better understanding of the structure of the galactic magnetic field should give us a more complete understanding of the structure of the galaxy to begin with. They may also help us to understand phenomena that we can see better. For example the arms or spirals of a galaxy are not 'static' relative to the stars in the arm. They are more of an effect of stars circling the galaxy clumping up or building into a wave, (for the bright portions of the arms) or moving apart (for the dim or spaces between the arms.) Having a good picture of the magnetic structure may give us pointers to what is causing these bunching and moving apart effects.

Finally we know that the magnetic field of Earth protects us from various radiation effects from the sun, which has it's own magnetic field that very well is affecting interstellar radiation. What sorts of affects on galactic and intergalactic radiation does the galactic magnetic field (and similar fields in other galaxies) have.

In time we may also be able to determine things like the age of a galaxy based on more than it's composition of stars. The structure of it's magnetic field where we can detect that, may tell us things about the age of it's stars. Do these fields grow with the absolute mass of a galaxy, is it greater or smaller based on the size of the galactic black hole for a galaxy. How do magnetic fields differ based on the structure of the galaxy that generates them.