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spiral density wave

(spiral structure that can form in disks)

A spiral density wave is a spiral-shaped band of higher (or lower) density centered on the center of a disk (a flat, round region of many particles orbiting something massive). The forces in such disks, including gravity (i.e., self-gravity, of the disk material itself, and also embedded larger objects), radiation pressure, and MHD-forces can be such that the disk does not stably remain uniform. One pattern that can develop is such a spiral structure.

This concept has been used to explain the overall spiral structure of spiral galaxies, to explain such density waves observed in one of Saturns rings, and it occurs in simulations and analysis of disks such as protoplanetary disks and accretion disks.


(physics,disks,galaxies,spiral)
http://en.wikipedia.org/wiki/Density_wave_theory

Referenced by:
galaxy
gravitational instability model
planetary migration

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