Lifecycle of a Star

Introduction

• Overview of star lifecycle
• Distinction between Hollywood stars and celestial stars

Formation of Stars

• Stars form from a stellar nebula (cloud of dust and hydrogen gas)
• Gravity causes dust and gas to spiral together over millions of years
• Particles move faster, reach millions of degrees to form a protostar

Main-Sequence Stars

• Star forms when hydrogen nuclei fuse to create helium
• Long stable period where nuclear fusion's heat outward pressure balances gravitational force
• Main-sequence stage lasts between 10 million and 10 billion years

Lifecycle of Smaller Stars

Transition from Main-Sequence to Red Giant

• Hydrogen runs out, fusion diminishes, leading to gravitational collapse
• Temperature increases, helium can fuse to form heavier elements (up to iron)
• Expansion to become a red giant (e.g., our Sun will engulf the inner planets)

Final Stages

• Fusion of helium stops, leading to gravitational collapse into a white dwarf
• White dwarf cools down over billions of years, eventually becoming a black dwarf

Lifecycle of Bigger Stars

Transition from Main-Sequence to Super Red Giant

• Larger stars run out of hydrogen faster, shorter main-sequence life
• Expand into super red giants, fusion creates elements up to iron

Supernova and Aftermath

• Fusion stops, leading to collapse and shock wave explosion (supernova)
• Supernova produces energy, outshining other stars for weeks
• High temperature and pressure create elements heavier than iron, distributed throughout the universe
• "We are made of Stardust"

End Result

• Formation of either a neutron star or a black hole
• Neutron star: densely packed neutrons from merging electrons and protons
• Black hole: formed from a neutron star if mass causes further gravitational collapse
• Black holes have strong gravity, light cannot escape, indirectly observed through effects on nearby objects

Conclusion

• Summary of star lifecycle
• Encouragement to engage with the content (thumbs up, subscribe, questions)
• Mention of additional resources (school app)