Download HR Diagram Activity

Name
Date
Period
A c tiv ity:
Sta rs’ Co lo r V s T em p
_
_
IST 9
How is a Star’s Color Related to Its Temperature?
On a clear night you have surely noticed that some stars are brighter than others. But stars also have
different colors. Rigel is blue, and Betelgeuse is red. Capella and our Sun are yellow. In this activity
you will make your own Hertzsprung-Russell diagram. You will see how star brightness, color,
temperature, and class are related.
Materials: Colored pencils (red, orange, yellow, blue)
Procedure:
1. Review the star data chart below. Note that the sun, which is used as a standard of brightness, is
given a value of 1. The brightness given for each other star shows how that star compares with
the sun.
2. Using an “X” as a plot point, plot the data from the chart on the pseudo-graph on the next page. Only
label the Sun’s X plot. (Do not include the star’s labels for anything other than the sun.
3. Stars with surface temperatures up to 3,500°C are red. Shade a vertical column from 2,000°C to
3,500°C red.
4. Shade other color columns as follows: Stars up to 5,000°C are orange-red; up to 6,000°C yellow;
6000°C to 10,000°C are white (don’t shade); up to 20,000°C blue-white, and up to 40,000°C
blue.
5. Look for patterns in your graph. Compare it to the H-R diagram supplied by your teacher.
6. Label the main sequence, the red super giants, and the white dwarfs.
Star-Brightness Data
Star Name
Sun
Alpha Centauri A
Alpha Centauri B
Barnard’s Star
Lalande 21185
Sirius A
Sirius B
Ross 248
61 Cygni A
61 Cygni B
Procyon A
Procyon B
Epsilon Indi
Approx.
Temp °C
5,300
5,500
3,900
2,500
2,900
10,100
10,400
2,400
3,900
3,600
5,200
7,100
3,900
Brightness
(Sun = 1)
1
1.3
0.36
0.0004
0.005
23
0.008
0.0001
0.08
0.04
7.5
0.0005
0.13
Star Name
Canopus
Arcturus
Vega
Capella
Rigel
Betelgeuse
Achernar
Beta Centauri
Altair
Aldebaran
Spica
Antares
Deneb
Beta Crucis
Approx.
Temp °C
7,100
4,200
10,400
5,600
11,500
2,900
14,000
21,000
7,700
3,900
21,000
3,100
9,900
22,000
Brightness
(Sun = 1)
1,500
90
60
150
40,000
17,000
200
3,300
10
90
1,900
4,400
40,000
6,000
Spectral Class
O
B
A
(see labels across top of graph for spectral class)
100,000
50,000
10,000
5,000
1,000
500
100
50
10
5
1
0.5
0.1
0.05
0.01
0.005
0.001
0.0005
0.0001
(Brightness)
40,000
20,000
10,000
F
G
K
M
7,000
6,000
4,500
3,000
Approximate Temperature, °C
Questions:
1. What is the general relationship between temperature and star brightness?
(Hint: Main Sequence)
2. What relationship do you see between star color and star temperature?
3. How does the sun compare to the other stars on the main sequence?
4. What star class does our sun belong to?
5. A star is classified as being in class B. What is its color? Temperature?
6. We know dwarfs are small—smaller than our sun. How can they be so bright?
*What are some ‘bad techniques’ regarding this graph???