Star Lifecycle and Evolution

Star Lifecycle

• Stars form from stellar nebulae, clouds of gas and dust.
• Gravity pulls the dust and gas together, creating a protostar.
• Protostars heat up as particles speed up.
• Nuclear fusion (hydrogen to helium) begins at extreme temperatures.

Main Sequence Stage

• Nuclear fusion creates outward pressure, balancing inward gravity.
• Stars stay stable in this stage for millions or billions of years.
• Our sun is in the main sequence stage.

Smaller Stars (like our Sun)

• Hydrogen fuel runs out, and fusion weakens.
• Gravity overpowers fusion, causing the star to collapse and heat up.
• Helium fuses into heavier elements (up to iron).
• The star expands to a red giant, potentially engulfing nearby planets.
• Helium fusion stops, and the star collapses into a white dwarf.
• The white dwarf gradually cools, becoming a black dwarf over billions of years.

Bigger Stars

• Bigger stars use their hydrogen fuel much faster.
• They expand into super red giants, creating elements up to iron.
• Fusion stops, causing a catastrophic collapse and supernova explosion.
• Supernovae create elements heavier than iron, releasing immense energy.
• The remnants become either neutron stars or black holes.

Neutron Stars and Black Holes

• Neutron stars form from the collapsed cores of massive stars.
• Electrons combine with protons, forming densely packed neutrons.
• High-mass neutron stars can collapse into black holes.
• Black holes pull in everything, even light.
• Black holes are detected by their gravitational effect on nearby objects.