1. Bellwork 12/13 Thinking about our simulation last class…
Describe what “gravity” is.
Use that description to explain why larger stars can form denser objects like Neutron Stars or Black holes. Why aren’t Brown Dwarfs able to fuse hydrogen?
What are some errors in our gravity simulation?

2. The Plan: Today: Review and wrap up loose ends Monday: Unit 3 Test
Wednesday 12/19: Begin Space Exploration!! …we start with the science of “The Martian”

3. White boarding Practice
Please, grab a white board, marker, and eraser 
Purpose:
Quick review of concepts
Identify topics you need to go back and practice with

4. Cooler stars emit what color light?
Red

5. Very bright, red stars will appear where on the HR Diagram?
Upper Right

6. White Dwarf stars appear where on the HR Diagram?
Bottom (middle)

7. A star has a temperature of 30,000K and a luminosity of 105
A star has a temperature of 30,000K and a luminosity of What type of star would you classify this as?
Blue Supergiant

8. Red Giant  Supernova Neutron Star/Black Hole
A star has a temperature of 30,000K and a luminosity of As this star “ages” what might its evolutionary pathway look like?
Red Giant  Supernova Neutron Star/Black Hole

9. Red Giant White Dwarf (Planetary Nebula is possible)
A star has a temperature of 10,000K and a luminosity of As this star “ages” what might its evolutionary pathway look like?
Red Giant White Dwarf (Planetary Nebula is possible)

10. Gravity (pulling inward) and Thermal Nuclear Energy (pushing outward)
What two forces need to be balanced in order for a star to remain stable?
Gravity (pulling inward) and Thermal Nuclear Energy (pushing outward)

11. Describe how a star forms (you can use a numbered list if you’d like)?
Gravity pulls dust and gas together
The contracting cloud begins to spin
The spinning cloud flattens into a disk
Particles in the center become very heated & pressurized
The middle becomes so hot that Hydrogen fuses…star is born!

12. What are the 5 basic Evolutionary Stages of a Star (begin with nebula)?
Protostar
Main-sequence star
Red Giant (very small stars stars skip this)
Death/Burnout

13. White Dwarf Neutron Star Black Hole
Put these items in order from least dense to most dense: Black Hole, White Dwarf, Neutron Star
White Dwarf Neutron Star Black Hole

14. Which property of a star determines its evolutionary pathway?
Mass! (Determines how much gravity can work on the particles)

15. Which kinds of elements are most abundant in the Universe ?
Hydrogen (H) and Helium (He)

16. What causes, or allows, atoms to fuse in a star?
Intense Pressure and Temperature due to Gravity

17. Can all elements be created in stars
Can all elements be created in stars? (Think back to your Stellar Nucleosynthesis modeling)
Nope!
After Iron (Fe) is created, it is not very easy for stars to put together heavier elements.

18. Lighter elements are pushed outwards
Based on your modeling, what happens to lighter elements as heavier elements start to form in the core?
Lighter elements are pushed outwards

19. Large Stars (Supergiants, giants) (More mass = more pull from gravity)
All stars can create Helium from Hydrogen. Which stars can create heavier elements?
Large Stars (Supergiants, giants)
(More mass = more pull from gravity)

20. Using your knowledge of gravity, explain why the Moon orbits the Earth.
The more massive object (Earth) curves the spacetime fabric more, causing the smaller object (the Moon) to fall towards it.

21. According to the Doppler Effect, the wavelength of radiation that an object emits is stretched when the object is moving ______________ an observer
Away from

22. Which of the objects below is moving towards the milky way?
Galaxy X
Galaxy Z
Galaxy Z

23. According to Hubble’s Law, which galaxy is moving away from the Milky Way fastest?
Galaxy D
Galaxy C
Galaxy B
Galaxy A
Milky Way
Galaxy B

24. Which two “forces” do scientists need to consider in order to determine the fate of the universe?
Gravity & Expansion

25. What are the 3 possible fates of the universe?
Big Crunch (expansion stops, followed by contraction)
Big Rip (expansion continues to accelerate forever, tearing apart matter)
Big Freeze/Chill (expansion continues but slows and approaches 0)

26. So, there’s a quick review of what we have covered in class…
Note: Your test is NOT all multiple choice/fill in the blank!! You will need to be able to describe these concepts with detail, examples, and appropriate vocabulary.
Please, return your white boarding materials to the lab counter. Thank you! 

27. Make a connection—Explain what is happening in a star when it moves from a Main Sequence star to a Red Giant.
Hydrogen & Helium burning is pushed outwards, expanding the radius and cooling the temperature.