First detection of magnetic field in distant galaxy produces a surprise

Robert C. Byrd Green Bank Telescope
The Robert C. Byrd Green Bank Telescope in West Virginia, the world's largest fully steerable radio telescope antenna. Its great sensitivity made possible the magnetic-field measurement in the distant protogalaxy. Credit: NRAO/AUI/NSF

Using a powerful radio telescope to peer into the early universe, a team of California astronomers has obtained the first direct measurement of a nascent galaxy's magnetic field as it appeared 6.5 billion years ago.

Astronomers believe the magnetic fields within our own Milky Way and other nearby galaxies—which control the rate of star formation and the dynamics of interstellar gas--arose from a slow "dynamo effect." In this process, slowly rotating galaxies are thought to have generated magnetic fields that grew very gradually as they evolved over 5 billion to 10 billion years to their current levels.

But in the October 2 issue of Nature, the astronomers report that the magnetic field they measured in this distant "protogalaxy" is at least 10 times greater than the average value in the Milky Way.

"This was a complete surprise," said Arthur Wolfe, a professor of physics at UC San Diego's Center for Astrophysics and Space Sciences who headed the team. "The magnetic field we measured is at least an order of magnitude larger than the average value of the magnetic field detected in our own galaxy."

The astronomers from the University of California campuses at Berkeley, San Diego and Santa Cruz used the world's largest fully steerable radio telescope for their measurements—the Robert C. Byrd Green Bank Telescope in Green Bank, West Virginia operated by the National Science Foundation's National Radio Astronomy Observatory. The young protogalaxy they probed, DLA-3C286, is located in a region of the northern sky that is directly overhead during the spring.

Until recently, astronomers knew very little about magnetic fields outside our own galaxy, having directly measured the magnetic field in only one nearby galaxy. "And that field wasn't as strong as the field we saw," said Wolfe.

But a team of Swiss and American astronomers reported in the July 17 issue of Nature that an indirect measurement of the magnetic fields of 20 distant galaxies, using the bright light from quasars, suggests that the magnetic fields of young galaxies were as strong when the universe was only a third of its current age as they are in the mature galaxies today.

Wolfe said those indirect measurements and his team's latest direct measurement of a distant galaxy's magnetic field "do not necessarily cast doubt on the leading theory of magnetic field generation, the mean-field-dynamo model, which predicts that the magnetic field strengths should be much weaker in galaxies in the cosmological past."

"Our results present a challenge to the dynamo model, but they do not rule it out," he added. "Rather the strong field that we detect is in gas with little if no star formation, and an interesting implication is that the presence of the magnetic fields is an important reason why star formation is very weak in these types of protogalaxies."

Wolfe said his team has two other plausible explanations for what they observed. "We speculate that either we are seeing a field toward the central regions of a massive galaxy, since magnetic fields are known to be larger towards the centers of nearby galaxies. It is also possible that the field we detect has been amplified by a shock wave generated by the collision between two galaxies."

"In either case," he added, "our detection indicates that magnetic fields may be important factors in the evolution of galaxies, and in particular may be responsible for the low star formation rates detected throughout the gaseous progenitors of young galaxies in the early universe."

"The challenge now," said J. Xavier Prochaska, another member of the team who is a professor of astronomy at UC Santa Cruz, "is to perform observations like these on galaxies throughout the universe."

Source: University of California - San Diego

Citation: First detection of magnetic field in distant galaxy produces a surprise (2008, October 1) retrieved 20 June 2019 from https://phys.org/news/2008-10-magnetic-field-distant-galaxy.html
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Oct 01, 2008
Electromagnetic waves travel with speed 'c' as we observe. And electromagnetic wave's speed changes in magnetic fields. Therefore, all calculations which assume that the speed of an electromagnetic wave is constant are in err.

I have said this before. We need to determine the speed of em-waves outside our solar system and outside of our galaxy. Then we can calculate an average speed of em-waves and make more accurate estimates describing the behavior of the universe.

And I still don't buy into Einstein's theory that em-waves travel at a constant speed no matter the speed of the observer. Em-waves would obviously experience a doppler effect, which would also change all of our estimates.

Oct 01, 2008
The magnetic fields are the driving cause, not the residual "dynamo" effect.

Oct 01, 2008
It's nice to know that dedicated astronomer Robert Byrd is finally getting the recognition he deserves in the naming of this telescope. A historical injustice has been rectified.

Oct 01, 2008
"Electromagnetic waves travel with speed 'c' as we observe. And electromagnetic wave's speed changes in magnetic fields. Therefore, all calculations which assume that the speed of an electromagnetic wave is constant are in err."

You realize that if that were the case, a great many modern technologies would not work, for example, GPS. Nowhere does it say that EM waves ever change their speed - and they don't. They can however change their frequency, and also their polarization can be altered by passing through EM fields.

"I have said this before. We need to determine the speed of em-waves outside our solar system and outside of our galaxy. Then we can calculate an average speed of em-waves and make more accurate estimates describing the behavior of the universe."

I'm sure you have said it before, and that would not change the fact that you are wrong. In any case, assuming that light (i.e. EM radiation) always travels at "c", one could make that case that "c" might change over time or as a function of distance (which are generally equivalent anyway). However, this would not alter any aspects of the universe since all other speeds are in proportion with "c". A classic example of the lack of any absolute unit of measurement.

"And I still don't buy into Einstein's theory that em-waves travel at a constant speed no matter the speed of the observer. Em-waves would obviously experience a doppler effect, which would also change all of our estimates."

Well, you pretty much have to accept it, given that every single experiment done has verified it. Besides, if the speed were not constant, the Doppler Effect would no longer be accurate as it would have different, effectively random values depending on where you pointed the telescope.

Oct 01, 2008
Electric currents make magnetic fields.
They totally skipped that step in galaxy formation....

And growing magnetic fields means greater currents!!!

Oct 02, 2008
"Astronomers believe the magnetic fields within our own Milky Way and other nearby galaxies - which control the rate of star formation..."

Yet another factor that possibly affects the rate/manner in which stars within galaxies are formed. If this is true there has to be an optimum galactic magnetic field strength/characteristic in which solar systems with earth-like planets are more easily formed. Some galaxies might contain an abundant number of life-supporting(or capable for life-supporting)solar systems while other galaxies will have a sparse number of eath-like solar systems.... any thoughts?

Jun 08, 2009
Magnetic field does form around flowing electricity, but it also forms around orbiting charged particles, just as a spinning magnetic field will generate electricity.

There are other effects besides Doppler that affect wavelengths however. We know that photons interact with other things besides magnetic fields to create longer wavelengths. Photons that travel through any sort of medium also gain longer wavelengths even our own sun is more red shifted to the horizon than it is at the center.

Photons that have traveled from a points source through space should be red shifted just from "gravity" alone, the further the point source, the more "time" the photons have had to be slowed or stretched, since they refuse to be slowed.

Growing magnetic fields in galaxies does sort of begin a journey down the road started by our plasma fellows though. After all to get a growing magnetic field one must first have free floating plasma to generate that field. Just where will this lead us?

Jul 11, 2009
Apart from the article, there is something bothering me. Maybe it is because I don't fully understand the definition of light. I understand light is a form EM radition which is visible to human eyes. Then, if light carries electric field and magnetic field at the same time, then we should detect magnetic field in reality. I would like to see that happening in my eyes. so, my quetion is how do I detect magnetic field in the air?...so that I can confirm that there is magnetic field...and another question is if I hold a magnet, then is it supposed to deflect light?...
I think I need your deep insight...
Thanks..

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