Molecular cloud collapse

Definition

Molecular cloud collapse refers to the process by which a dense region within a molecular cloud experiences gravitational instability, leading to its contraction and the eventual formation of stars. This phenomenon is essential in star formation, as molecular clouds serve as the primary sites where new stars are born from the accumulation of gas and dust. As the cloud collapses, regions within it can fragment into smaller clumps that may each form individual stars or stellar systems.

5 Must Know Facts For Your Next Test

1. Molecular clouds are composed mostly of hydrogen molecules and are often the coldest and densest parts of the interstellar medium.
2. The collapse of a molecular cloud can be triggered by external factors such as shock waves from nearby supernovae or interactions with other clouds.
3. During collapse, the cloud's density increases, which raises the temperature and pressure at its core, eventually leading to nuclear fusion when conditions are right.
4. The timescale for a molecular cloud to collapse can range from tens of thousands to millions of years, depending on its mass and environmental conditions.
5. The resulting stars from the collapse can vary widely in mass, leading to a diverse population of stellar objects, including massive stars and smaller red dwarfs.

Review Questions

• How does gravitational instability lead to molecular cloud collapse and what role does it play in star formation?
  • Gravitational instability occurs when the internal pressure of a molecular cloud can no longer support its mass against gravitational forces. This leads to regions within the cloud collapsing inward, resulting in increased density and temperature. As the material continues to collapse, it triggers the formation of protostars, marking the beginning stages of star formation. Thus, gravitational instability is a crucial first step in transforming a molecular cloud into new stars.
• Evaluate the external factors that can influence the collapse of a molecular cloud and their impact on star formation rates.
  • External factors such as shock waves from supernovae, interactions with other molecular clouds, or turbulence within the interstellar medium can compress areas within a molecular cloud. This compression can initiate gravitational collapse more readily in some regions than others. Consequently, these factors can significantly enhance star formation rates by triggering rapid collapses in otherwise stable clouds, leading to periods of increased star birth activity within galaxies.
• Synthesize the relationship between molecular cloud collapse and the lifecycle of stars in the context of galactic evolution.
  • Molecular cloud collapse is integral to the lifecycle of stars and plays a vital role in galactic evolution. As clouds collapse and form new stars, they contribute to the overall stellar population within a galaxy. The types of stars formed from these collapses—ranging from massive stars that end their lives as supernovae to smaller ones that evolve more slowly—impact chemical enrichment in galaxies through processes like supernova explosions and stellar winds. This cycle of birth, evolution, and death of stars influences not only the chemical composition but also the structure and dynamics of galaxies over time.

Related terms

Star Formation: The process through which dense regions in molecular clouds collapse under gravity to form stars.

Gravitational Instability: A condition in which a cloud of gas or dust becomes unstable and begins to collapse under its own gravitational force.

Protostar: An early stage in star formation that occurs when material from a collapsing molecular cloud accumulates in a dense core, heating up as it contracts.