Star Formation Process

Study Notes

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

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

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

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

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

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

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