Stages of Star Formation

Star formation is a fascinating process that begins in molecular clouds and evolves through several stages. Understanding these stages, from gravitational collapse to hydrogen fusion, reveals how stars and planetary systems come to be in our universe.

1. Molecular cloud formation

   • Composed of gas and dust, primarily hydrogen molecules.
   • Dense regions within the cloud are potential sites for star formation.
   • Temperature is low, allowing molecules to clump together and form structures.

2. Gravitational collapse

   • Triggered by disturbances such as shock waves from nearby supernovae.
   • Gravity causes the dense regions of the molecular cloud to contract.
   • Leads to an increase in temperature and pressure at the core of the collapsing region.

3. Protostar formation

   • As the core contracts, it heats up and forms a protostar.
   • Surrounding material begins to fall inward, adding mass to the protostar.
   • Protostars are often surrounded by a rotating disk of gas and dust.

4. T Tauri phase

   • Characterized by strong stellar winds and variability in brightness.
   • Represents a young star that is still accumulating mass from its surroundings.
   • Important for studying the early stages of stellar evolution and disk interactions.

5. Main sequence star

   • Achieved when hydrogen fusion begins in the core, stabilizing the star.
   • The star enters a long-lasting phase where it fuses hydrogen into helium.
   • The balance between gravitational forces and radiation pressure defines its stability.

6. Protoplanetary disk formation

   • Formed from the leftover material in the rotating disk around the protostar.
   • Provides the building blocks for planet formation through accretion processes.
   • The disk's dynamics influence the eventual architecture of planetary systems.

7. Accretion and mass loss

   • Material from the protoplanetary disk continues to fall onto the star, increasing its mass.
   • Stellar winds and outflows can remove excess material, regulating growth.
   • This process affects the star's evolution and the formation of surrounding planets.

8. Hydrogen fusion initiation

   • Marks the transition from a protostar to a main sequence star.
   • Fusion reactions release energy, creating outward pressure that counteracts gravity.
   • Establishes a stable phase in a star's life, lasting billions of years.