1. Understand the electromagnetic spectrum and how it is organized.
Understand what different types of electromagnetic radiation can reveal about astronomical objects.
Understand and describe important properties of electromagnetic radiation.
Understand how technology is used to collect electromagnetic radiation and turn it into images.
Understand what can be learned from analyzing the light from astronomical objects.
Understand how different types of lenses and telescopes work
Understand and describe the quantization of energy at the atomic level
Understand that all objects emit and absorb electromagnetic radiation and distinguish between objects that are blackbody radiators and those that are
Qualitatively describe the shift in frequency in sound or electromagnetic waves due to the relative motion of a source or a receiver

2. Read the FYI The color of stars
Answer the 2 questions in your science journal.

3. Question of the day
How can you determine the temperature of a star when they are so far away?
You will need a calculator today

4. The Color of Stars
Blackbody radiation is the type of EM radiation emitted by a blackbody (an opaque and non-reflective body) held at constant, uniform temperature.
Ie. Temperature determines color, so you can look at color to figure out temperature.
The temperature of a lava flow can be estimated by observing its color. The result agrees well with measured temperatures of lava flows at about 1000 to 1200 °C.

5. Wein’s Law Max λ = C_ T(K) C= constant = 0.29 cm K
Mathematical formula that shows the relationship between temperature and color (wavelength)
Max λ = C_
T(K)
C= constant = 0.29 cm K
T(K) = temperature in K
λmax= maximum wavelength (color)

6. Calculate the wavelength. [Wein’s Law]
Max λ = C_
T(K)
Star with a temperature of 3,000K
Star with a temperature of 15,000K
Star with a temperature of 5,800K
(for those that just want to sit there and let other students do this while they do nothing, just know that you will have to do this yourself on the test next week – you should practice)
Determine the color
cm to nm (multiply by 10 million)
C=0.29 cm

7. Calculate the wavelength. [Wein’s Law]
Max λ = C_
T(K)
Star with a temperature of 3,000K =
Star with a temperature of 15,000K =
Star with a temperature of 5,800K =
9.67*10^-5 (967nm)
1.93*10^-5 (193nm)
500 nm

8. When looking at a distant star, you observe its spectrum
When looking at a distant star, you observe its spectrum. You find that the peak wavelength for this star is at 480nm. What is its surface temperature?
Max λ = C_
T(K)

9. 480nm
= .29/T
T = .29/
T =
(÷10,000,000) = .29/T
6,041.7º K

10. Stefan-Boltzmann Law E = σT4 E=energy -- measured in W/m2
The total energy emitted (intensity) by an object is equal to a constant (σ) times the temperature of the object to the 4th power
E = σT4
E=energy -- measured in W/m2
σ=constant =  5.67×10−8
T=temperature

11. Calculate. [Stefan-Boltzmann Law]
Our sun has a surface temperature of 5,800K. If a star has a temperature of 11,600K approximately how many times more energy will it emit?

12. Calculate. [Stefan-Boltzmann Law]
Our sun has a surface temperature of 5,800K. If a star has a temperature of 11,600K approximately how many times more energy will it emit?
σ·11600^4 =
σ·5800^4
=16

13. Calculate. [Stefan-Boltzmann Law]
Our sun has a surface temperature of 5,800K. If a star has a temperature of 2,900K approximately how many times less energy will it emit?

14. Calculate. [Stefan-Boltzmann Law]
Our sun has a surface temperature of 5,800K. If a star has a temperature of 2,900K approximately how many times less energy will it emit?
5800^4= 16
2900^4

15. Energy intensity (Watts/m2)
Use Wein’s Law and Stephan-Boltzmans Law to complete a row of your chart.
Peak color
Temperature
(K)
Wavelength (nm)
Energy intensity (Watts/m2)
Infrared
4142
700
16,688,735.7
Red
Orange
Yellow
Green
Blue
Violet
Ultraviolet
<400

16. Use the median value for each color
Color wavelength interval infrared~ >700nm red~ 700–635 nm orange~ 635–590 nm yellow~ 590–560 nm green~ 560–490 nm blue~ 490–450 nm violet~ 450–400 nm Ultra-violet~ <400nm

17. infrared 700 nm 700nm = (.29 cm/K)/ T .00007 cm = .29/T T= .29/.00007
T ~ 4142 K
C=0.29 cm

18. infrared
T ~ 4142 K
5.67x10-8 x 41424
x 4142 x 4142 x 4142 x 4142
E = 16,688,735.7 Watts/m2

19. C= 0.29 cm
Color wavelength interval infrared~ >700nm red~ 700–635 nm orange~ 635–590 nm yellow~ 590–560 nm green~ 560–490 nm blue~ 490–450 nm violet~ 450–400 nm Ultra-violet~ <400nm
Use the median value for each color

20. Use Wein’s Law and Stephan-Boltzmans Law to complete a row of your chart.
(pick a different one that the people around you)
Peak color
Temperature (K)
Wavelength (nm)
Energy intensity W/m2
Infrared
4142.8
700
16,702,554.23
Red
4344.5
667.5
20,200,865.19
Orange
4734.6
612.5
28,493,820.12
Yellow
5043.4
575
36,686,279.61
Green
5523.8
525
52,788,319.53
Blue
6170.2
470
82,183,308.09
Violet
6823.5
425
122,919,088.3
Ultraviolet
7250
400
156,651,690.2

21. Please answer the question of the day
How can you determine the temperature of a star when they are so far away?

22. This is on Canvas. It is due SUNDAY @ midnight.