Star Formation Process

Transmission and Celestial System

Star Formation

• The Process:
  • Giant molecular clouds collapse under gravity, fragmenting into denser regions
  • These regions spin faster, flatten into disks, and heat up at the center
  • Protostar forms at the center, surrounded by a disk of gas and dust
• Main Sequence:
  • Once the protostar reaches a stable state, it becomes a main-sequence star
  • Fusion of hydrogen into helium releases energy, making the star shine
• Factors Influencing Star Formation:
  • Gravity, magnetic fields, and turbulence in the molecular cloud
  • Metallicity, radiation, and nearby stars can also impact the process

Galactic Structure

• Components:
  • Bulge: Older, spherical distribution of stars at the galaxy's center
  • Disk: Flat, rotating disk of stars, gas, and dust, including spiral arms
  • Halo: Extended, spherical distribution of dark matter and stars
• Spiral Arm Formation:
  • Density Wave Theory: Spiral arms form from density waves, triggering star formation
  • Self-Gravitating Disk: Spiral arms form from gravitational instability in the disk
• Galaxy Types:
  • Spiral: Milky Way-like, with spiral arms and a prominent bulge
  • Elliptical: Older, football-shaped galaxies with little gas and dust
  • Irregular: Chaotic, irregularly shaped galaxies, often the result of mergers

Star Formation

• Giant molecular clouds collapse under gravity, leading to the formation of denser regions
• Fragmentation of the cloud leads to the formation of multiple protostars
• As the protostar spins faster, it flattens into a disk shape and heats up at the center
• A protostar forms at the center of the disk, surrounded by a disk of gas and dust
• Once the protostar reaches a stable state, it becomes a main-sequence star
• Fusion of hydrogen into helium releases energy, making the star shine
• Gravity, magnetic fields, turbulence, metallicity, radiation, and nearby stars influence star formation

Galactic Structure

Components of a Galaxy

• The central, spherical bulge consists of older stars
• The flat, rotating disk is composed of stars, gas, and dust, and includes spiral arms
• The extended, spherical halo is made up of dark matter and stars

Spiral Arm Formation Theories

• The density wave theory proposes that spiral arms form from density waves, triggering star formation
• The self-gravitating disk theory suggests that spiral arms form from gravitational instability in the disk

Galaxy Types

• Spiral galaxies have spiral arms and a prominent bulge (e.g., the Milky Way)
• Elliptical galaxies are older, football-shaped, and contain little gas and dust
• Irregular galaxies have chaotic, irregular shapes, often resulting from mergers

Transmission System

• Transmits power from the engine to the wheels of a vehicle
• Comprises four main components:
  • Clutch: connects and disconnects the engine from the transmission
  • Gearbox: changes the gear ratio to adjust speed and torque
  • Propeller shaft: connects the gearbox to the differential
  • Differential: splits power between the two wheels
• Four types of transmission:
  • Manual transmission: driver manually shifts gears
  • Automatic transmission: gears shift automatically
  • Semi-automatic transmission: combines manual and automatic shifting
  • Continuously variable transmission (CVT): uses belts and pulleys to change gear ratio

Celestial System

• A celestial system consists of a star and all the celestial objects that orbit around it
• Our solar system is an example of a celestial system, with the Sun at its center
• Can include planets, dwarf planets, asteroids, comets, and other objects
• The study of celestial systems is important for understanding the formation and evolution of our universe