My main question is: Is there a strong galactic magnetic field, perhaps driven by the supermassive black hole at the center of our galaxy? I am also wondering if this field would be strong enough to make it so that the galaxy rotates in the way it does (with the outer stars moving faster than would be expected), and if this would be an alternate explanation for dark matter.

The thing that led me to ask this question is reading about Jupiter's magnetic field interactions with the plasma emitted by IO. Jupiter's magnetic field forces the plasma to orbit Jupiter about as fast as Jupiter spins, and I am wondering if likewise, the supermassive black hole at the center of our galaxy "herds" the rest of the galaxy in a similar manner as per the article and image below.


IO's plasma and Jupiter's magnetic field


1 Answer 1


No, the galactic magnetic field is very weak, about 0.1nT. It is able to bend the trajectory of highly-energetic charged particles and also to align dust grains across the magnetic field.

However, is too weak to affect the rotation of a galaxy.

Although the origin of galactic magnetic field is not clear yet, the supermassive black holes do not significantly influence the galactic magnetic field far from them.

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    $\begingroup$ Thank you for your response! I am wondering if even this weak force can affect the rotation of the galaxy, because it would likely be applied over the entire galaxy (e.g. every part of the sun, or maybe even every part of the whole sun's magnetic field would be pulled with this force) amounting to a much greater than anticipated effect, and whatever this effect is probably would apply to all the stars in the galaxy. $\endgroup$
    – Jonathan
    Jan 16, 2015 at 13:32
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    $\begingroup$ Most of the mass of galaxies is in the form of electrically neutral medium, so magnetic field cannot affect it. Most of the clouds of ionized hydrogen (HII) near young stars are dense enough so that their inner magnetic fields should be much stronger than galactic field. And again note, that even ionized hydrogen clouds are neutral as a whole, so that external magnetic forces affecting a cloud as a whole are zero. $\endgroup$ Jan 1, 2016 at 18:52

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