Magnetic fields essential for star formation?

  1. Brian G Turner

    Brian G Turner He's a very naughty boy! Staff Member

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    Jan 10, 2018
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  2. J Riff

    J Riff The Ants are my friends..

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    .."The strength of the magnetic fields in space could also influence how massive stars grow to be,"
    Magnets do get weird at low temperatures. Mass attracts mass. A star is born!
     
    Jan 11, 2018
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  3. Mirannan

    Mirannan Well-Known Member

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    Just another observation: Stars could not form without the ability to emit EM radiation (such as IR light) in the process of accreting. And EM radiation implies magnetic fields, of course.

    Of course, if EM radiation didn't exist it wouldn't matter much, because there would be nobody to see the stars anyway. :)
     
    Jan 12, 2018 at 2:30 PM
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  4. chrispenycate

    chrispenycate resident pedantissimo Staff Member

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    Why does EM radiation imply magnetic fields?
     
    Jan 12, 2018 at 5:21 PM
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  5. Mirannan

    Mirannan Well-Known Member

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    Because EM radiation is a travelling wave of electric and magnetic fields driving each other, oscillating perpendicular to each other. For details:

    Khan Academy

    Incidentally, this isn't just theory. For high-powered, concentrated beams of EM radiation (even if individual photons aren't all that energetic) such as cutting lasers, the electric field can be large enough to ionise air - which soaks up some of the power and leads to the beam being attenuated.
     
    Jan 12, 2018 at 6:23 PM
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  6. Venusian Broon

    Venusian Broon Defending the SF genre with terminal intensity

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    No, chrispenycate, who I am sure is aware what an EM wave is, is right to question why the presence of something as simple as EM radiation implies that there should be magnetic fields that span something as astronomical as a stellar nursery - as stated in the article - these are massive long range magnetic forces which can't be related to simple EM radiation being produced by a star or proto-star.

    The ionisation of air that you are referring to, is another process - there, the photons of the laser are ripping off electrons from the atoms and molecules and therefore the energy of the beam is being attenuated because it's photons are being removed by being absorbed by the air molecules.

    EM fields such as light are produced on the atomic scale, whether that is as a by-product of fusion or by an atomic electron being excited in its 'orbit' then falling back to it's low-energy state and producing an photon.

    There are in fact very large scale Galactic magnetic fields which are a property of the entirety of the galaxy rotating.
     
    Jan 13, 2018 at 1:07 AM
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  7. Mirannan

    Mirannan Well-Known Member

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    Good point. A couple of things in reply: First of all, large-scale magnetic fields are usually produced by something conductive rotating. A good example on a much smaller scale is Earth's magnetic field, produced by rotating liquid iron; another one is the Sun. And most of the interstellar medium is plasma, which does conduct. (As in your example of the galactic magnetic field.) Do stellar nurseries usually rotate, or at least large parts of them? Frankly, I don't know.

    IMHO the reason why large-scale magnetic fields are possible is that the EM interaction is long-range, in fact infinite in principle. And the reason for that? Well, possibly because the EM field's force carriers are photons, which have zero rest mass. Contrast that to the extremely short range of the weak force, which has very heavy force carriers.

    To amplify on that: The EM force relies on an exchange of virtual photons. A field as weak as the Galactic one is going to involve the exchange of extremely low-mass and therefore extremely low-energy photons. (Why? Heisenberg. Energy times time, I believe.) And that's OK, because with a zero rest mass the energy can be as low as required. I'm not enough of a physicist to calculate the wavelength of the photons involved in the galactic field interactions, but my gut feeling is that said wavelength is going to be huge - maybe light-days at least?
     
    Jan 13, 2018 at 4:09 AM
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