Image courtesy of Manel Carrillo, Josep Miquel Girart (CSIC-IEEC), Nimesh Patel (SMA), Spitzer

Magnetic Fields Dominate Young Stars of all Sizes?

11 Jun , 2009

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When it comes to the role of magnetism in the formation of stars, size might not matter.

A team of researchers led by Josep Girart, of the Institut de Ciències de l’Espai (in Spain), studied the slow evolution of a dust cloud into a massive star, and realized that the cloud’s magnetic field controls the star’s development more than any other factor. They propose that the story is the same for small stars — an idea that could offer a new way to understand the formation of the early universe.

The new hypothesis is presented in this week’s issue of the journal Science, and the lead image represents an artist’s rendering of the concept.

The background shows a false-color Spitzer image of the massive star-forming region G31.41, with the colors indicating various wavelengths of light.  The zoom-in region represents the dust emission from the massive hot core (color and contour image) superposed with bars showing the structure of the magnetic field.

Pictured in the bottom of the image is the Submillimeter Array in Hawaii, which was used for the observations.

The authors describe how the magnetic field at G31.41 has deformed the dust cloud into an hourglass shape – a telltale sign of magnetically controlled star formation.

They say that this magnetic energy dominates over the other energies at play — e.g., centrifugal force and turbulence — and suggest that the role of the magnetic field in the early stages of star formation could be very similar for both small and massive stars.

“The energetic relations do not differ too much” between massive and small stars, the authors write. “Both cores are collapsing because gravity has overcome pressure forces, but the collapsing dynamics are controlled by the magnetic energy rather than by turbulence.”

Girart and his colleagues point out that this only holds true for forming stars; older massive stars are more influenced by radiation and ionization pressure, turbulence, and outflows than by magnetic fields.

Massive stars play a crucial role in the production of heavy elements and in the evolution of the interstellar medium, so this discovery might eventually lead to new insights about the formation of the early universe.

Source: Science


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DrFlimmer
Member
DrFlimmer
June 11, 2009 11:52 AM

It has been clear to the community for quite some time that star formation is influenced by magnetic fields.
I can go into the details if someone wishes, for now I don’t have the time.

Just as an information for some of our fellows here. I guess they will appear soon….

Lawrence B. Crowell
Member
Lawrence B. Crowell
June 11, 2009 1:14 PM

This one is a perfect curtain call for Anaconda to make another pitch!

mgmirkin
Member
June 11, 2009 2:16 PM

Interesting…

mgmirkin
Member
June 11, 2009 2:26 PM

So, from whence do these dominant magnetic fields originate? Currents of some form or function, I assume?

Ivan3man_At_Large
Member
Ivan3man_At_Large
June 11, 2009 5:40 PM

Lawrence B. Crowell:

This one is a perfect curtain call for Anaconda to make another pitch!

You mean like this?

Jon Hanford
Member
Jon Hanford
June 11, 2009 7:07 PM

Yes, this is directly related to Astrofiend’s ‘dim matter’ comment on another thread (although not as he intended it to be used) smile

Astrofiend
Member
Astrofiend
June 12, 2009 12:18 AM

wink

As I said – catchy.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
June 12, 2009 4:44 AM

Yes, whence the magnetic fields? Remnants from ionization or other particles with magnetic moments lining up, or large scale charge separation somehow?

Help, please. “Nature abhors an empty head”.

catchy

Catchy by being preemptive. For example, “to take a dim view of the matter” is out. :-/

Nereid2
Member
Nereid2
June 12, 2009 5:16 AM

@mgmirkin: are you the same ‘MGmirkin’ who W.T.”Tom” Bridgman responds to on his blog (http://dealingwithcreationisminastronomy.blogspot.com/2008/11/electric-cosmos-solar-resistor-model.html)?

If so, I’m wondering if you could help Anaconda out, and tell him how one can estimate the strength and direction of an electric current in space (beyond the solar system), based on astronomical observations. A particularly nice bonus would be if you could cite a paper (or three) of Alfvén’s, where he outlines (or even details!) the steps one could take to arrive at such estimates …

mgmirkin
Member
June 12, 2009 9:41 AM

No doubt a tricky feat, but, one would assume that if it were possible to determine the magnetic field topology, size, distance.

Looking for synchrotron radiation or using the Faraday effect are fairly standard for ferreting out magnetic fields of faraway objects in space, yes?

Such information could be used to reverse engineer the corresponding currents that would produce such a field configuration. Might take a supercomputer to do so, but there seem to be plenty of those around for reverse engineering “dark matter” out of the lack of enough OBSERVABLE mass in galaxies and clusters to keep them from flying apart. Astrophysicists are wily that way, they’ll figure it out. I’d suggest starting at Maxwell’s equations. wink

mgmirkin
Member
June 12, 2009 9:50 AM

And just as another overly simplistic question, do our measurements give a 3D model of magnetic field strengths around a star, or a flat 2-dimensional map? I’m assuming the latter, but I may be mistaken? Obviously it would be more difficult to go from a 2D map to a 3D simulation. But such is the burden of observation and theory of objects so far away, no? We take what little we can actually get and have to try to fill in the gaps, while trying to not violate any known laws of physics. wink

Nereid2
Member
Nereid2
June 12, 2009 10:13 AM
@mgmirkin: thanks for the swift reply! May I infer, from your reply, that you do not know *how* to go about estimating an electric-current-in-space’s magnitude and direction, beyond some vague feeling that it should be possible? Also, may I infer, from your lack of mention in your comment of Alfvén, that you do not know where, or indeed if, he outlines *how* such estimates could be made, in any of his published works? No doubt a tricky feat, but, one would assume that if it were possible to determine the magnetic field topology, size, distance. (bold added) Perhaps … but I am not aware of any technique, in astrophysics, by which the “magnetic field topology” in a region… Read more »
Nereid2
Member
Nereid2
June 12, 2009 10:27 AM
Stars rotate … and so (spectral) line profiles will show changes with time (i.e. as the star being observed rotates). There are techniques to recover (estimated) ‘starspot’ distributions from the time variation of line profiles … but of course they are only as good as the assumptions built into the models (and data analyses). do our measurements give a 3D model of magnetic field strengths around a star, or a flat 2-dimensional map? (bold added) AFAIK, the same sort of techniques can be used to reconstruct the strength of magnetic fields on the photospheres of stars whose lines show clear evidence of the Zeeman effect … of course, this is not ‘around’, but ‘on’. BTW, how do you… Read more »
mgmirkin
Member
June 12, 2009 10:40 AM

Though, Zeeman splitting or similar process is I suppose more applicable to magnetic field measurements of stars (as opposed to nebulae and other more tenuous sources)?

http://adsabs.harvard.edu/abs/1980ApJ…239..961R

Nereid2
Member
Nereid2
June 12, 2009 10:58 AM

Indeed.

however, the method is insensitive to field strengths below 1000 Gauss

(from that source’s abstract).

I presume you have some knowledge of the estimated of interstellar medium (ISM) magnetic field strengths?

mgmirkin
Member
June 12, 2009 11:17 AM
how can one estimate the strength and direction of an electric current in space (beyond the solar system), Well, I’ll admit that I’m not specifically familiar with the maths involved… However, that said I’m becoming slightly familiarized with the concepts involved, so if you don’t mind a death of maths, we can take a quick conceptual look at an example. I’d simply point out that the right hand rule is quite helpful when dealing with currents and magnetic fields. en.wikipedia.org/wiki/Electric_current#Electromagnetism A long straight filament of current will generate a cylindrical magnetic field about it. The right hand rule describes the relationship between the current direction and the magnetic field direction (curl?). How does that help? Well, as stated… Read more »
mgmirkin
Member
June 12, 2009 11:18 AM

Err, that should have read “dearth” not “death,” my bad.

mgmirkin
Member
June 12, 2009 11:28 AM
“The magnetic field lines are like stretched rubber bands; the tension squeezes the cloud into its filamentary shape.” As an aside, the statement about the humorously named “magnetic slinkies” isn’t all that far off the mark… In fact the effect of a current flowing through plasma will tend be a magnetic field and the magnetic field will tend to constrict the flow of current. This is known as the magnetic pinch effect in plasma physics (also known as the Bennett pinch, electromagnetic pinch, z-pinch, plasma pinch, and probably a few other colorful names I’ve forgotten). en.wikipedia.org/wiki/Pinch_(plasma_physics) A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma In a z-pinch,… Read more »
mgmirkin
Member
June 12, 2009 11:32 AM

In any event, didn’t mean to divert conversation away from stars. Just a particular example of how one might interpret things under the electrical paradigm and how it might match up with observations and be useful in tracing / calculating from observations of magnetic fields back to current strength / direction.

I assume everyone else here is probably better with the maths than I am. So, I won’t argue that point. But, hopefully you at least see where I’m coming from and how it might be applied by those with the requisite skills for the task.

I’m off for a bit. Probably shouldn’t waste too much time @ the day job. Feel free to discuss amongst yourselves.

mgmirkin
Member
June 12, 2009 12:27 PM

Poking around a bit, one would assume that Ampere’s law would be the correct bit of Maxwell’s equations to use as a starting point…

Granted this would all lead to a rough guesstimate, and reality is considerably messier than a simple straight wire in the lab. But, what *does* conform to “idealized” equations in science these days? wink Not much, I’d wager.

wpDiscuz