Explain star formation in spiral arms

Question

What will be an ideal response?

Answer 1

The most prominent theory about spiral arms is called the spiral density wave theory, which proposes that the arms are waves of compression that move around the galaxy triggering star formation. Of course, star formation will occur where the gas clouds are compressed. Stars pass through the spiral arms unaffected, like bullets passing through a wisp of fog, but large clouds of gas slam into the spiral density wave from behind and are suddenly compressed. That sudden compression could trigger the formation of stars in a gas cloud. Thus, new stars should form along the spiral arms.Star formation can control the shape of spiral patterns if the birth of stars in a cloud of gas can cause the birth of more new stars. Massive stars evolve so quickly that their lifetimes are only an instant in the history of a galaxy, and then they explode as supernovae. We have learned that bursts of luminosity and jets from newborn stars and the expanding gases of supernova explosions can compress neighboring clouds of gas and trigger more star formation. This process is known as self-sustaining star formation.