What mechanism is responsible for triggering star formation within the spiral arms?

Answer

Compression of interstellar gas clouds reaching the Jeans criterion

The bright luminosity of spiral arms is a direct result of intensive star formation occurring within them. As interstellar gas and dust clouds, which are generally orbiting faster than the density wave pattern, flow into the high-density region, they undergo significant compression. If this compression is severe enough to meet the Jeans criterion, the clouds experience gravitational collapse. This collapse initiates the process of star formation. Furthermore, this process is often accompanied by galactic shocks when gas enters at supersonic speeds, causing a sudden, dramatic increase in density and pressure right at the shock front, which significantly enhances the trigger for collapse and the subsequent birth of new stars.

What mechanism is responsible for triggering star formation within the spiral arms?

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galaxyformationastrophysicsdensity wavespiral arm