1. Collapse:
- The nebula was mostly hydrogen and helium, with traces of other elements.
- Gravity caused parts of the nebula to clump together.
- As the cloud contracted, it spun faster and faster, like a figure skater pulling in their arms.
2. Protostar Formation:
- The core of the collapsing cloud became extremely hot and dense.
- This hot, dense core is called a protostar.
- The protostar continued to accrete material from the surrounding cloud.
3. Nuclear Fusion Ignition:
- The core of the protostar became so hot and dense that nuclear fusion began.
- This is the process where hydrogen atoms fuse to form helium, releasing enormous amounts of energy.
- This energy outward pressure balanced the inward pull of gravity, stabilizing the star.
4. Main Sequence Star:
- The Sun reached a stable state, where it fuses hydrogen into helium in its core.
- This is the stage where the Sun currently is, and will remain for billions of years.
Key Points:
- The Sun's formation took millions of years.
- The process was driven by gravity and nuclear fusion.
- The Sun is still evolving, and will eventually run out of fuel.
What Happens Next?
- In about 5 billion years, the Sun will run out of hydrogen fuel in its core.
- It will then expand into a red giant, engulfing the inner planets, including Earth.
- Eventually, it will shed its outer layers, leaving behind a white dwarf, a dense, hot remnant of its former self.
