So here we go again ...
New theory of evolution for spiral galaxy arms
Quote:
Since 1960s, the most widely accepted explanation has been that the spiral arm features move like a Mexican wave in a crowd, passing through a population of stars that then return to their original position. Instead, computer simulations run by Grand and his colleagues at University College London’s Mullard Space Science Laboratory (MSSL) suggest that the stars actually rotate with the arms. In addition, rather than being permanent features the arms are transient, breaking up and new arms forming over a period of about 80-100 million years.
"We have found it impossible to reproduce the traditional theory, but stars move with the spiral pattern in our simulations at the same speed. We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces," said Grand.
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Can somebody please convince me that the nature of the spiral arm pattern in a spiral galaxy, is
not caused by the interaction between simple behaviours of individual stars (gravitation mainly) which produces complex, yet organized group behaviour amongst a bunch of them ?
The behaviours/motions of the stars within the spiral arms seems inherently nonlinear so mixing them, gives the group behaviour a chaotic aspect. The negative feedback may be provided by the behavioural controllers (eg: inertia/momentum, centrifugal force, centripetal force, etc), which tends to keep the group dynamics ordered. The result is both chaotic behaviour (which has neither short nor long term predictability) .. like how long the arms last, how long a shape persists and; ordered (static or periodic) behaviour .. like the motion of stars moving towards or away from the galaxy centre ?
Looking at things this way, leads to 'no big surprises' when we find other than spiral galaxy shapes (elliptical, clusters, etc). Maybe even 'the hunt' for dark matter/energy disappears also (when considering the rotation rates) ?
I look forward to the day when someone important notices these aspects and applies the thinking to the galaxy
and universe formation models.
Cheers