Caption: Illustrated is the winding problem for the theory that spiral arms have fixed components.
Features:
- The spiral arms
of spiral galaxies
CANNOT SIMPLY be a fixed set of
stars and
interstellar medium (ISM).
If they were, the
spiral arms
would wind tighter and tighter
and merge after a few hundred million years
(see CK-390;
FK-568).
This is because the orbital periods increase with distance from the galaxy centers (roughly galaxy centers of mass) and so outer objects increasingly fall behind in the race.
- Recall that 220 Myr is the orbital period
of the
Sun
in the Milky Way
(FK-565) and this period
should be order of valid for most
stars in the
galactic disks of
spirals.
- BUT although the
spiral arms
of spiral galaxies
CANNOT SIMPLY be a fixed set of
stars and
interstellar medium (ISM),
the
flocculent spiral arms
of flocculent spiral galaxies
form partially by winding.
See spiral_arms_bars.html
and
Wikipedia: SSPSF model
(stochastic self-propagating star formation model).
Image link: Itself.
Local file: local link: spiral_arm_winding_problem.html.
File: Galaxies file: spiral_arm_winding_problem.html.