What Do You Know About Stars?

How long does a star live?

• Well, that's determined by it's mass
• The larger the mass, the shorter the life

Life Cycle of Stars

• Hydrogen gas pulled together by gravity
• Begins to spin
• Temp. reaches 15,000,000 deg.
• Glows, contracts, becomes stable
• Shines for millions-billions of yrs

Red Giant Phase

• Red because:
• Cooler than in the main sequence stage
• Giant because:
• Outer shell has expanded outward
• Helium then fuses into carbon

Low Mass Stars

• After helium fuses into carbon:
• Core collapses
• Outer layers expelled
• Core remains a white dwarf
• Cools to become black dwarf

Massive Stars

• Undergoes supernova explosion
• If explosion1.4---3x the size of Sun
• will be neutron star
• Later, becomes black hole

Gravitational Collapse (final stages)

• Material heats up
• Forms new elements &
• radioactive isotopes

Untitled Slide

• Shock wave propels remnants
• into space
• Hot material produce X-rays 
• and gamma rays

Large Star Lives to Small Stars Lives