1. 1
Stellar Astronomy
Spring_2015
Day-18

2. Course Announcements Exam-2 – Fri. 3/6 Chapters 5 & (some of) 6
 I will collect the L-T books at this time.
Smartworks Chapters 5: Due Wed. 3/4
Smartworks Chapters 6: Due Mon. 3/16
APSU Research and Creativity Forum April 11-12, 2014
Abstracts are due: 4:30pm Fri., March 21
Mar. 2 – Last day to drop with an automatic “W”
Apr. 2 – Last day to drop a class.

3. Solar Flare

4. Big and Hot objects have greater luminosity than small cool objects
Luminosity is the total energy (light) emitted by an object in each second.
Stefan-Boltzmann law
Luminosity depends on an surface area (A), and its temperature (T4); Surface Area ∝ R2
Luminosity = 4π R2 T4
Big and Hot objects have greater luminosity than small cool objects

5. Lecture Tutorial Luminosity: (pg 55)
Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one another. Take time to understand it now!!!!
Come to a consensus answer you both agree on.
If you get stuck or are not sure of your answer, ask another group.

6. Hertzsprung-Russell Diagram
20, , ,000
Luminosity (solar units)
Temperature (K) 4 2 1 3 5
10,000
100 10
0.1
0.01
0.001
0.0001
1,000

7. Which star is Hot and Dim?
20, , ,000
Luminosity (solar units)
Temperature (K) 4 2 1 3 5
10,000
100 10
0.1
0.01
0.001
0.0001
1,000
Temperature (K)

8. Which star is Cool and Dim?
20, , ,000
Luminosity (solar units)
Temperature (K) 4 2 1 3 5
10,000
100 10
0.1
0.01
0.001
0.0001
1,000
Temperature (K)

9. Luminosity (solar units)
Which star is Largest?
20, , ,000
Luminosity (solar units)
Temperature (K) 4 2 1 3 5
10,000
100 10
0.1
0.01
0.001
0.0001
1,000

10. Luminosity (solar units)
Which star is smallest?
20, , ,000
Luminosity (solar units)
Temperature (K) 4 2 1 3 5
10,000
100 10
0.1
0.01
0.001
0.0001
1,000
Temperature (K)

12. Brightness is the amount of light arriving at a particular place.
Decreases as the distance from a light source increases, obeying an inverse square law.
The light spreads out over a greater area.
Fig. 5.23 12

13. Lecture - Tutorial: Blackbody Radiation (pg. 59)
Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one another. Take time to understand it now!!!!
Come to a consensus answer you both agree on.
If you get stuck or are not sure of your answer, ask another group.

14. Energy Output per second
Star A
Star A
Star A
Star D
Energy Output per second
Star C
Star B
V I B G Y O R
V I B G Y O R
V I B G Y O R
Wavelength

15. Which has the longer peak wavelength?
Star C
Wavelength
V I B G Y O R
Energy Output per second
Star A
Star A
Star C
Same

16. Which has the lower surface temperature?
Star C
Wavelength
V I B G Y O R
Energy Output per second
Star A
Star A
Star C
Same

17. Energy Output per second
Which star looks red?
Star A
Star C
Both
Neither
Star C
Wavelength
V I B G Y O R
Energy Output per second
Star A

18. Which has the greater energy output?
Star C
Wavelength
V I B G Y O R
Energy Output per second
Star A
Star A
Star C
Same

19. Energy Output per second
Which star is larger?
Star C
Wavelength
V I B G Y O R
Energy Output per second
Star A
Star A
Star C
Same

20. Which star is larger? Star A Star D Same Star A Star D
Wavelength
V I B G Y O R
Star A
Energy Output per second

21. Energy Output per second
Try to determine EVERYTHING about how these four stars compare!! Temp, Energy output, color, size (area)…..
Object A
Wavelength
V I B G Y O R
visible range
Energy Output per second
Object C
Object B
Object D