Density wave theory

Theory of structure of spiral galaxies

Density wave theory or the Lin–Shu density wave theory is a theory proposed by C.C. Lin and Frank Shu in the mid-1960s to explain the spiral arm structure of spiral galaxies. The Lin–Shu theory introduces the idea of long-lived quasi-stationary spiral structure (QSSS hypothesis). In this hypothesis, the spiral pattern rotates with a particular angular frequency (pattern speed), whereas the stars in the galactic disk orbit at varying speeds, which depend on their distance to the galaxy center.

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