1 Answers
The SSPSF model of star formation was proposed by Mueller & Arnett in 1976, generalized afterward by Gerola & Seiden in 1978 and Gerola, Seiden, & Schulman in 1980. This model proposes that star formation propagates via the action of shock waves produced by stellar winds and supernovae traversing the gas that composes the interstellar medium.
The Henize 206 nebula provides a clear example. In particular, 24μ infrared emission shows where a new generation of stars heats the remains of the supernova remnant that induced their formation.
In contrast to star formation in density-wave theories, which are limited to disk-shaped galaxies and produce global spiral patterns, SSPSF applies equally well to spirals, to irregular galaxies and to any local concentrations of gas in elliptical galaxies.
The effect may be envisioned as an "SIR infection model" in a differentially rotating disk, the host galaxy. The SIR model is applied to star formation propagating through the galaxy: Each generation of stars in a neighborhood includes some massive ones whose stellar winds and, soon, supernovae, produce shock waves in the gas. These lead to collapsing nearby gas clouds, which produce the next generation of stars ; but in the immediate neighborhood, all initially available gas is used, so no further stars are born there for some period of time despite the shocks.