Scientists chart high-precision map of Milky Way's magnetic fields

Feb 03, 2012
The sky map of the Faraday effect caused by the magnetic fields of the Milky Way. Red and blue colors indicate regions of the sky where the magnetic field points toward and away from the observer, respectively. The band of the Milky Way (the plane of the Galactic disk) extends horizontally in this panoramic view. The center of the Milky Way lies in the middle of the image. The North celestial pole is at the top left and the South Pole is at the bottom right. Credit: Max Planck Institute for Astrophysics

(PhysOrg.com) -- Scientists at the Naval Research Laboratory (NRL) are part of an international team that has pooled their radio observations into a database, producing the highest precision map to date of the magnetic field within our own Milky Way galaxy.

The team, led by the Max Planck Institute for Astrophysics (MPA), used the database they created and were able to apply information theory techniques to produce the , explains NRL's Dr. Tracy Clarke, a member of the research team. "The key to applying these new techniques is that this project brings together over 30 researchers with 26 different projects and more than 41,000 across the sky. The resulting database is equivalent to peppering the entire sky with sources separated by an angular distance of two full moons." This incredible volume of data results in a new, unique all-sky map that gives scientists the ability to measure the magnetic field structure of the Milky Way in unparalleled detail.

The map shows scientists a quantity known as Faraday depth, a concept that depends on magnetic fields along a specific line of sight. The research team created the map by combining the more than 41,000 individual measurements using a unique technique. The researchers at MPA are specialists in the new discipline of theory. Dr. Tracy Clarke, working in NRL's Remote Sensing Division, is part of the team of international radio astronomers who provided the for the database. The new, high-precision map not only shows the Galactic magnetic field's structure on large scales, it also reveals small-scale features that help scientists better understand turbulence in the .

The Milky Way, along with all other galaxies, possesses magnetic fields. Until now, scientists have been puzzled over the origin of these galactic magnetic fields. The assumption was that the magnetic fields were created by processes where is converted into magnetic energy. These same kinds of processes occur in the interior of the Earth and the Sun. The map that the team has created will give scientists valuable knowledge about the structure of Galactic magnetic fields throughout the Milky Way.

Scientists chart high-precision map of Milky Way's magnetic fields
This image shows the uncertainty in the Faraday map. In the area of the celestial south pole, the measurement uncertainties are particularly high because of the low density of data points. Credit: Max Planck Institute for Astrophysics

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 . By measuring the polarization of the light sources at different frequencies, researchers can determine the amount of Faraday rotation.

With these individual measurements, researchers gain data about only a single path through the Galaxy. To gain a fuller picture of the Milky Way's magnetic fields from the Faraday rotation measurements, researchers have to observe many sources across the sky. To achieve this map, radio astronomers from around the world have pooled data from 26 different projects, collecting a total of 41,330 individual measurements. The map contains approximately one radio source per square degree of sky.

Despite this large catalog of date, there are still some large areas, especially in the southern sky, where only a few measurements have been recorded. So to gain a realistic map of the entire sky, researchers have to interpolate between the existing data points that they do have recorded.

There are some difficulties in obtaining the map data this way. First, the accuracy of the various measurements varies greatly although the more exact measurements should have the greatest influence. However scientists are not certain exactly how reliable any single measurement is in providing dependable information about the environment around it. Therefore more accurate measurements are not always given the highest priority.

Scientists chart high-precision map of Milky Way's magnetic fields
In this map of the sky, a correction for the effect of the Galactic disk has been made in order to emphasize weaker magnetic field structures. The magnetic field directions above and below the disk seem to be diametrically opposed, as indicated by the positive (red) and negative (blue) values. An analogous change of direction takes place across the vertical center line, which runs through the center of the Milky Way. Credit: Max Planck Institute for Astrophysics

There is also the problem of the uncertainty of the measurements simply because the process for obtaining the measurements is highly complex. A seemingly small error can impact the data in a significant way, leading to a distorted map.

To address these problems, the MPA scientists have developed an algorithm used to reconstruct the images. This algorithm, called the "extended critical filter," uses tools provided by the new discipline known as information field theory. Information field theory, which uses logical and statistical methods applied to fields, is an effective tool for dealing with erroneous information. Besides astronomy these tools can be used in fields such as medicine or geography for a range of image and signal-processing applications.

While the new map is particularly important for studying our own Galaxy, researchers will also be able to use it for future studies for extragalactic magnetic fields. This is possible because the scientists will use the new map to help them account for the Galactic contribution to observed Faraday rotation. In the near future astronomers are looking toward a new generation of radio telescopes, such as LOFAR, eVLA, ASKAP, MeerKAT and the SKA that will provide an abundance of measurements of the Faraday effect. With this new data, researchers will be able to provide updates to the image of the Faraday sky, and perhaps someday understand the origin of the galactic magnetic fields.

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mgmirkin
1.7 / 5 (6) Feb 03, 2012
Hint:

http://www.who.in...sEMF/en/

"Magnetic fields are created when electric current flows: the greater the current, the stronger the magnetic field ... If current [flows], the strength of the magnetic field will vary with power consumption ..."

Start there.

Figure out where the currents are flowing in the galaxy.

wikipedia.org/wiki/Electric_current#Electromagnetism

"Electric current can be directly measured with a galvanometer, but this method involves breaking the electrical circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current."

Since we now know with greater accuracy the structure of magnetic fields in the galaxy, we should be able to work backwards to electric currents, right?
kevinrtrs
Feb 03, 2012
This comment has been removed by a moderator.
antialias_physorg
4.6 / 5 (11) Feb 03, 2012
Since we now know with greater accuracy the structure of magnetic fields in the galaxy, we should be able to work backwards to electric currents, right?

It's not quite so easy. We have a 2D map, but the currents would be in 3D. It's the same problem you have in computer tomography: You have a bunch of 2D projections and try to recreate the 3D volume of the thing you're imaging. There are algorithms that do that (e.g. backprojection), but since the information on the 2D projections is always less than the information in the originating 3D volume the reconstruction is never perfect. (though you can get very good)

BUT: You need a LOT of projections for a good reconstruction. To make any headway you need at least 2 from different angles (the further away the better). Unfortunately we don't have that. Even taking 2 pics at opposite ends of Earth orbit probably doesn't give us enough of an angle to get a reasonable reconstruction.
antialias_physorg
4.8 / 5 (16) Feb 03, 2012
However, there is no known natural process that can account for the creation of such magnetic fields

Says the man with a degree in astrophysics. Or electrical engineering. Or high school physics. Or elementary school math.

Oops. Sorry. You don't have any of those...

How would YOU know what creates magnetic fields? The only thing you read is the Bible. Last I checked there's not one word about electromagnetism in there (or science for that matter)
HannesAlfven
1.3 / 5 (14) Feb 03, 2012
Re: "The assumption was that the magnetic fields were created by processes where mechanical energy is converted into magnetic energy."

It's fascinating to watch the theorists deal with this faulty assumption. Clearly, it is not permissible within the astrophysical community for any of them to question the assumption itself. And this is in spite of the observation that the interstellar matter is oftentimes quite filamentary and knotted (akin to the electrical currents of a novelty plasma globe), and even oftentimes exhibits critical ionization velocities for the universe's most abundant elements (which indicate the slamming of charged particles into neutral clouds of gas). CIV's associated with filamentary HI hydrogen is a pretty good indicator that these are electrical currents. The magnetic fields support this inference.

The mainstream astrophysicists continue their denial that their scientific framework is faulty. It's only a matter of time before their prestige is affected.
bewertow
1 / 5 (1) Feb 03, 2012
The Milky Way, along with all other galaxies, possesses magnetic fields. Until now, scientists have been puzzled over the origin of these galactic magnetic fields.

One reason for the puzzle is that the scientists assume that stars and galaxies have a naturalistic origin, i.e. they came into existence by themselves out of purely natural processes.
However, there is no known natural process that can account for the creation of such magnetic fields - especially because no natural process can account for the creation of stars without some enormous external help. And just so by the way - the magnetic fields themselves are a great hinderance to the naturalistic formation of stars from a cloud of space dust!


You are an idiot. Magnetic fields are the solution to the angular momentum problem in star formation. MHD waves carry away angular momentum along the field lines you dumbass.
aroc91
5 / 5 (8) Feb 03, 2012
especially because no natural process can account for the creation of stars without some enormous external help.


Yeah, 'cause gravity amassing hydrogen together is such a far flung idea. /sarcasm
Deesky
4.6 / 5 (9) Feb 03, 2012
@Kev,

One reason for the puzzle is that the theists assume that stars and galaxies have a un-naturalistic origin, i.e. they came into existence by a farting sky fairy out of purely un-natural processes.

However, there is no known un-natural process that can account for the creation of such magnetic fields - especially because no un-natural process can account for the creation of stars without some enormous fantasy fudge. And just so by the way - the magnetic fields themselves are a great hinderance to the un-naturalistic formation of stars from a dust farting sky fairy!
Argiod
1 / 5 (9) Feb 03, 2012
Too many reasons the data could be in error; too many assumptions... for this to be given any scientific credence. Come back when you have reliable data...
vidyunmaya
1 / 5 (7) Feb 04, 2012
sub:Plasma Regulated Electromagnetic Phenomena in and around Magnetic Field-Environment.
the sssence of Cosmology vedas interlinks are projected in detailed PPT- to evolve sensex-Sensitive index.
the Horizontal magnetic fields at the milkyway galactic plane need to orient in steps towards Vertical Plane.the purpose of Interlinks-Sristi-Stithi-Layam - need to be understood with comprehension. This helps advancement of space-science Cosmology sudies. see further in my books
http://vidyardhicosmologyvedasinterlinks.
Many thanks for the working groups . Cosmology needs best of brains trust.
Vidyardhi Nanduri