1. Bellwork 11/23 Please, have your Stellar Evolution Simulation out 
What are the 5 general stages of Stellar Evolution?
Based on our simulation on Monday, what conclusion can you make regarding what evolutionary path a star will take?

2. Conclusion Questions:
You should know the basic pathways of each star type.
You should know which stars have multiple pathways
You should understand that the star’s mass (and temperature & luminosity) can predict it’s pathway
Understand the connection between mass & gravity
Be able to use these pathways and stellar properties to make predictions on an HR Diagram
**Note, there is a CORRECT and INCORRECT prediction here. However, based on our data, you could arrive at either—and for a long time, the science community DID arrive at both predictions.

3. Stellar Remnants

4. 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

5. 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

6. Neutron Star
Pea size sample
Weighs 100 million tons

7. 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

8. “…A star is a kind of cosmic kitchen inside which atoms of hydrogen are cooked into heavier atoms. Stars condense from interstellar gas and dust, which are composed mostly of hydrogen. But the hydrogen was made in the Big Bang, the explosion that began the Cosmos. If you wish to make an apple pie from scratch, you must first invent the universe.”
--Carl Sagan, Cosmos

10. Which two elements make up the majority of matter in the universe?
Hydrogen & Helium

11. So how do we get all these other elements?

12. Stellar Nucleosynthesis:
Process in which presence of elements within stars changes due to nuclear fusion reactions
Reactions happen in the core & “mantles” of the star
Stars are said to evolve (age) with changes in the amounts of the elements

13. What causes nucleosynthesis?
Immense pressure & temperature
Due to gravity

14. So, what’s the timeline here?

15. Quick Review of Chemistry…

16. Quick review of chemistry…
As you add more protons, what happens to the atomic mass?

17. Nucleosynthesis Modeling:
Keep in mind:
There are MANY MANY MANY more atoms in a star than what we are modeling with
The chemistry of nuclear reactions is often not as straightforward as you will experience today…but it is important that we understand the basics of element formation