Last: ______________________ First: ________________ Period: ____ Group: _____ Date: / /
Group Members: ________________________, ________________________, ________________________
Read, Understand and Apply!
Failure is not an option!
Investigative Question: How do scientists classify stars?
Materials: ESRT, color pencils (red, orange, yellow, white, light blue, blue), circle template, stencils or different size/color stickers
Introduction: Astronomers use two basic properties of stars to classify them. These two properties are luminosity and surface temperature. Luminosity refers to the brightness of the star relative to the brightness of our sun if they were located next each other. In order to calculate this value, scientists must know the size (surface area), distance and real temperature of the star.
L=4πr2f
L=Luminosity r=radius f=energy flux of the surface of the star (S x T4) S=Stefan-Boltzmann Constant
*Flux is the amount of light that comes from a certain area in a certain amount of time.
A bigger star will appear brighter than a smaller star of the same temperature when placed next to it. For example, 10 light bulbs of the same power (wattage) and temperature will appear brighter than a single light bulb because, cumulatively, they have a larger surface area. Another example, a flash light and a searchlight have similar temperature, therefore similar flux, but from a distance of 100 meters, the search light is the brighter of the two. Why? Because, the search light is bigger and has a larger surface area than the flashlight.
A star has the same surface temperature as the sun, but its ten times larger in radius would be 100 times the luminosity of the sun. If the distance between earth and the sun increases 10 times the sun will appear 100 times dimmer.
Star A and B have the same radius. If star A has a temperature that is twice higher than star B then Star A will be 16 time more luminous than Star B.
Astronomer will often use a star’s color to measure its temperature. Stars with low temperature produce a reddish light while stars with a high temperature shine with a brilliant blue-white light. Surface temperatures of stars range from about 3000 degrees Celsius to 50, 000 degrees Celsius. When these surface temperatures are plotted against luminosity, the stars fall into groups. Using data similar to what you will plot in this activity, Danish astronomer Ejnar Hertzsprung and US astronomer Henry Russel independently arrived at similar results in what is now commonly referred to as the HR diagram.
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Part 1: Pre-lab Exercise: Use your ESRT, Characteristics of Stars chart to answer the following questions
1. The horizontal axis represents _______________________ and _______________________
2. The unit for temperature is ____, the range is from(smallest) _________ to _________ (largest)
3. The vertical axis represents _______________________ and _______________________
4. Scale range for Luminosity is from (smallest) _________ to _________ (largest)
5. Each increment on Luminosity scale increases and decreases by __________ times.
6. There are _____ major groups of stars labeled in this chart, which are: ________________________, ________________________, ________________________ and ________________________
7. Complete the table below
Star
|
Temperature
|
Color
|
Luminosity
|
Size
Small, medium, massive
|
Barnard’s Star
|
|
|
|
|
Sun
|
|
|
|
|
Spica
|
|
|
|
|
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Part 2: Characteristics of stars data table
Star
|
Surface
Temp. (K)
|
Luminosity
(x sun)
|
Circle size
|
Star
|
Surface Temp. (K)
|
Luminosity (x sun)
|
Circle size
|
Proxima Centauri
|
3042
|
0.0017
|
3/16”
|
Altair
|
6900
|
11
|
11/32”
|
40 Eridani B
|
3100
|
0.5
|
1/4”
|
Polaris
|
7200
|
2200
|
7/16”
|
Barnard’s Star
|
3134
|
0.004
|
3/16”
|
Procyon B
|
7740
|
0.001
|
3/16”
|
Betelgeuse
|
3140
|
120000
|
½”
|
Vega
|
9000
|
40
|
11/32”
|
Antares
|
3400
|
57500
|
½”
|
Sirius A
|
9940
|
25
|
11/32”
|
Lacaille
|
3626
|
0.03
|
7/32”
|
Rigel
|
12130
|
117490
|
½”
|
Aldebaran
|
3910
|
518
|
3/8”
|
Regulus
|
12460
|
288
|
3/8”
|
Ceti
|
4797
|
139
|
3/8”
|
Achemar
|
15000
|
3150
|
7/16”
|
Sun
|
5800
|
1
|
9/32”
|
Spica
|
22400
|
12100
|
½”
|
Procyon A
|
6530
|
7
|
5/16”
|
Sirius B
|
25200
|
0.03
|
7/32”
|
……………………………………………………… cut and paste into lab book ……..…………………………………......................
Some Important Characteristics of Stars: STUDENT INSTRUCTIONS
Read, Understand and Apply!
Failure is not an option!
Procedure. Record all observations in corresponding Data Tables, Charts and Graphs. Cut and glue the sections as you complete them. You must follow the sequence of instructions and procedure.
Cut and glue the introduction into your lab book. Read and understand the introduction.
Part 1. Pre-lab exercise: After reading the introduction, use your ESRT “Characteristics of Stars” chart and complete the blank spaces with appropriate terminology and values. Do not forget the correct units!
Part 2.
a. Use the surface temperature and luminosity values for Proxima Centauri and plot (with a dot) this data on the graph paper (Characteristics of Stars- HR Diagram) provided.
b. Use the circle template/stencil and the size of the star provided in the data table and draw a circle around the dot, considering the dot is the center of the circle representing the star.
c. Repeat the procedures a and b for all other stars, one at a time.
d. Refer to ESRT “Characteristics of Stars” chart. Determine the colors and corresponding temperatures on the horizontal axis. Use this information and color each circle representing a star on the diagram you created.
Part 3. Conclusion questions. Use diagram you created and the ESRT to answer the following questions. Use complete sentences and complete thoughts when answering.
1. What is the relationship between the size of stars and luminosity?
2. What is the relationship between the temperature and color exhibited by stars?
3. How do the luminosity and temperature of the Sun compare with those of other stars?
4. How is the Sun classified? Must state star group, temperature and luminosity.
5. How do astronomers estimate a star’s temperature?
6. Compared to Sun, the star Betelgeuse is: Must state size, temperature and luminosity.
7. Name the star which is about 200 times brighter than the Sun but has a surface temperature about 2000 K cooler than the Sun.
8. The star with the lowest luminosity is the dimmest because of its surface temperature or size?
9. Use ESRT “Solar System Data” table to help you answer this question. If you were to observe the Sun from the Earth and Saturn at the same time, what would the Sun’s luminosity from Saturn be if the Sun’s luminosity from Earth is 1? Explain your answer.
10. Summarize how astronomers classify stars?
H-R Diagram (279.0K)
