1. Lives of Stars
Section 21.3

2. Stephen 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

9. 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
Black Dwarf
White 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 Time

17. Star Systems and Galaxies
Binary stars- two stars

18. Star Systems and Galaxies
Eclipsing Stars- one star blocks another

19. Star Systems and Galaxies
Open Cluster- Loose, disorganized

20. Star Systems and Galaxies
Globular Cluster- round, densely packed

21. Star Systems and Galaxies
Galaxy- stars, star systems, star clusters,
dust and gas bound by gravity

22. Star Systems and Galaxies
Spiral Galaxy – bulge with spiral arms

23. Star Systems and Galaxies
Elliptical Galaxy – round or elliptical

24. Star Systems and Galaxies
Irregular Galaxy – no regular shape

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
Big Bang – the initial explosion that resulted in the formation of the universe
Hubble’s law – the farther away a galaxy is, the faster it is moving away from us

28. Star Systems and Galaxies

29. Star Systems and Galaxies

30. Star Systems and Galaxies