1. Lives of Stars Section 21.3

2. Stephen Hawking - The Birth of Stars - YouTubeStephen Hawking - The Birth of Stars - YouTube

3. Life Cycle of Stars Nebula – large cloud of gas and dust spread out in an immense volume

4. Life Cycle of Stars Gravity pulls gas and dust together in the densest part of the nebula When there is enough mass for a star to form it is called a Protostar

5. Life Cycle of Stars When the contracting gas and dust from a nebula becomes so dense and hot that nuclear fusion starts, a star is born. Dust Cloud Theory

6. Life Cycle of Stars How long a star lives depends on its mass -Stars with less mass live longer - Stars with more mass live shorter Small mass stars use up their fuel more slowly than larger mass stars Small stars – 200 billion years Medium stars – 10 billion years Larger stars – 10+ millions years

7. Life Cycle of Stars When a star begins to run out of fuel, its core shrinks and its outer portion expands Depending on its size, the star becomes a red giant or a supergiant After the fuel runs out it becomes a white dwarf, a neutron star, or a black hole

8. Life Cycle of Stars

10. Death of Stars When the fuel begins to run out of medium and low mass stars, their outer layers expand to become a red giant. The outer layer then expands out in to space (planetary nebula) and the blue- white core cools (White Dwarf)

11. Death of Stars The core is very dense. A spoonful of material would weigh as much as a truck It would cool to become a black dwarf White dwarf Black Dwarf

12. Death of Stars Supernovas High mass stars evolve quickly into supergiants The supergiant can explode suddenly when it runs out of fuel

13. Death of Stars The outer portion can form partly recycled stars We are made of recycled stars The inner portion can become other kinds of stars Supernova

14. Death of Stars Neutron star The remains of a high mass star, smaller and denser than white dwarfs Spinning neutron stars (pulsars) give off pulses of radio waves

15. Death of Stars Black Hole Form from the most massive stars when they die Gravity is so strong, light (or any kind of radiation) can not escape Black hole

16. Videos Black Holes, Neutron Stars, White Dwarfs, Space and TimeBlack Holes, Neutron Stars, White Dwarfs, Space and Time

17. Star Systems and Galaxies Binary stars

18. Star Systems and Galaxies Eclipsing Stars

19. Star Systems and Galaxies Open Cluster

20. Star Systems and Galaxies Globular Cluster

21. Star Systems and Galaxies Galaxy

22. Star Systems and Galaxies Spiral Galaxy

23. Star Systems and Galaxies Elliptical Galaxy

24. Star Systems and Galaxies Irregular Galaxy

25. Star Systems and Galaxies Quasar – an enormous, distant,bright galaxy with a black hole at its center

26. Star Systems and Galaxies Milky Way (our galaxy)

27. Star Systems and Galaxies