1. What does the word “Evolution” mean?
Bellwork 11/18:
What does the word “Evolution” mean?

2. Today: Bellwork Warm up & quick notes Stellar Evolution Simulation
Discuss Stellar Remnants
Finish “Sisters of the Sun”?

3. Discuss with your table partner:
Based on your reading from the book, match each phase of a human life cycle with each phase of a star’s life cycle.
Human Life Cycle Stages
Stellar Life Cycle Stages
Gamete
Fetus
Childhood-Young Adult Hood
Middle Age
Old Age-Death
Red Giant/Supergiant
Fusion Ignition/Main-sequence
Nebula
Stellar Remnant
Protostar

4. Stellar evolution Changes in a star’s properties over its “life”
Stars exist because of gravity
Two opposing forces in a star are
Gravity – contracts
Thermal nuclear energy – expands

5. Stages (5 Total) Nebula Birth In dark, cool, interstellar clouds
Gravity contracts the cloud
Temperature rises
Radiates long-wavelength (red) light

6. Stages
2. Protostar
Gravitational contraction of gaseous cloud continues
Hydrogen nuclei fuse
Become helium nuclei
Process is called hydrogen burning
Energy is released
Outward pressure increases

7. 3. Main-sequence stage
When outward pressure is balanced by gravity pulling inward
Hydrogen continues to fuse into Helium
90% of a star's life is in the main-sequence
There are lots of types of Main-sequence stars. Why? What determines where they fall on the H-R Diagram?

8. 4. Red giant stage Hydrogen burning migrates outward
Star's outer envelope expands
Surface cools & becomes red
Core is collapsing as helium is converted to carbon
Eventually all nuclear fuel is used
Gravity squeezes the star
Unbalanced forces

9. 5. Burnout or Death OPTIONS:
White Dwarf
Planetary Nebula
Supernova
Black Hole
Neutron star
What determines which of these outcomes will occur?
Let’s take a look…

10. Stellar Evolution Simulation
You will begin as 1 of 4 main-sequence type stars
You will travel through stations, recording your star’s evolution
You will be collecting information on intermediate and ending phases

11. The Basics:
Choose a “star” out the beaker. Determine which type of star you are based on the data given & your HR Diagram
Follow the directions at each table.
Make sure to collect information at each station
Record your evolutionary pathways on the class data table, please.

12. You can start out as 1 of 4 stars:
Brown Dwarf
Red Dwarf
Average/Solar-type
Blue Supergiant

13. Stellar Remnants

14. White Dwarf Small (some no larger than Earth) Dense
Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
Electrons displaced inwards

15. Neutron Star Forms from a more massive star Remnant of a supernova
Star has more gravity
Squeezes itself smaller
Remnant of a supernova
Gravitational force collapses atoms
Electrons combine with protons to produce neutrons
VERY Small size

16. Neutron Star
Pea size sample
Weighs 100 million tons

17. Black Hole More dense than a neutron star
Intense surface gravity lets no light escape
As matter is pulled into it
Becomes very hot
Emits x-rays
Likely candidate is Cygnus X-1, a strong x-ray source