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  Spiral Galaxy Arm's Magnetic Fields

An interesting conclusion after a study of IC342, a large obscured, nearby spiral galaxy:

'
"Spiral arms can hardly be formed by gravitational forces alone," continues Rainer Beck. "This new IC 342 image indicates that magnetic fields also play an important role in forming spiral arms."
'

from NOAO:

'
Spiral Galaxy IC342 is located roughly 11 million light-years from Earth. Its face-on appearance in the sky—as opposed to our tilted and edge-on views of many other nearby galaxies, such as the large spiral galaxy Andromeda (M31)—makes IC342 a prime target for studies of star formation and astrochemistry.
'

from another source:

'
[This] galaxy is obscured by the dust in our galaxy by nearly three full magnitudes. If it weren’t for this dimming effect, IC342 would be one of the finest and brightest face-on spirals in the sky and easily visible to the unaided eye in dark sky. That would make it by far the most distant object you could see with the unaided eye.
'

The conclusion about the important role of magnetic fields presents a conundrum.

Currently the rotation curve of a spiral galaxy is assumed to be driven by the mass distribution in the disk.
This scientist claims gravity alone does not drive the spiral arm formation.

This is an important conclusion because when the mass distribution does not result in the correct rotation curve dark matter is proposed to 'fix' the mass distribution.


An earlier post (August 5) had described issues with dark matter and its role in the mass distribution.

The study of IC342 indicates we are still learning about the spiral arms.

link


About 3 days later I posted the fellowing comment to the above post:

This study of IC342 concluded magnetic fields in the spiral arms were more important than gravity in their formation. Here is a presentation of a study of M31 where including its magnetic field will 'fix' the rotation curve for the outer stars. The video includes the values and calculations.

If this model change fixes the curve then dark matter is not needed in M31.

Both studies involve magnetic fields.

link to M31 study



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