Name: __________________________________
Period: _______
Date:_____________
LAB # ___________
All labs must be completed in pencil
CLASSIFICATION
of STARS
Introduction: In the beginning of the 20th century, two astronomers, Hertzsprung and Russell
developed a system of classifying stars based on their color, temperature, spectral class, and size. This
graph is called the H-R diagram.
The H-R diagram plots a star’s luminosity; the energy released by a star as compared to the Sun’s
energy released; against its spectral class which is determined by temperature. Different temperature
ranges appear in different sections of the visible spectrum. Hotter stars appear blue, while cooler stars
appear red. Stars get their energy and ability to “shine” by a processes called nuclear fusion. Nuclear
fusion is when elements in stars combine to make a heavier element. Hydrogen atoms fuse together
to form Helium and this releases a lot of energy.
Stars are categorized into spectral classes named “giants,” “super giants,” “main sequence,” and
“white dwarfs.” These names help to determine the age of stars based on their temperature and
luminosity. Most stars (about 90%) including our Sun are main sequence stars.
Objective: Using the data tables and the graph provided, you will chart actual stars based on their
temperature and luminosity to determine their spectral class.
Procedure: Read the directions carefully and check them off as they are completed.
1. Plot the stars found in tables 1 – 4 on the blank H-R diagram provided (one per group)
a. Note Y-axis of the H-R diagram is logarithmic. This means every bold line on the Y-axis
increases the scale by a power of ten! (ex: 10; 100; 1,000; 10,000 ….)
2. Plot the main sequence stars from Table 1 in pencil
3. Plot the red giant stars from Table 2 in red
4. Plot the blue giant stars from Table 3 in blue
5. Plot the dwarf stars from Table 4 in black
a. Split this task up within the members of your lab group
b. Use your best estimation skills to plot the data that has been given
6. Refer to Table 5 and very lightly shade in the chart to reflect the temperature of each type of
star cluster
7. Using page 15 of your ESRT label each area on your graph with the appropriate star class
8. Plot the following stars from your ESRT onto your graph in pencil and label them
a. Barnard’s star
b. Polaris
9. Answer the questions that follow
TABLE 1 – Main sequence stars
STAR NAME
Regulus
TEMPERATURE K (kelvin)
12000
LUMINOSITY
85
Beta Tauri
12000
700
Vega
9700
250
Castor
9200
300
Sirius A
9200
50
Altair
7750
30
Procyon A
6500
65
Alpha Centauri A
5900
2
The Sun
5900
1
Tau Ceti
4900
0.7
Epsilon Eridani
4600
0.5
Cygni A
3800
0.08
Alpha Centauri B
4000
0.7
Kapteyn’s Star
3300
0.005
Lacaille 8760
3400
0.04
Lacaille 21185
3200
0.007
TABLE 2 – Red giant stars
STAR NAME
Capella
TEMPERATURE K (kelvin)
6000
LUMINOSITY
350
Pollux
3800
60
Arcturus
4600
120
Aldebaran
4000
110
Antares
3400
7500
Betelgeuse
3200
15000
TEMPERATURE K (kelvin)
18000
LUMINOSITY
300
Spica
19500
700
Achernar
17500
1100
Beta Crucis
21000
10000
Alpha Crucis
19500
5000
Rigel
11500
30000
Beta Centauri
21000
1100
TEMPERATURE K (kelvin)
8200
LUMINOSITY
0.005
6500
0.02
TABLE 3 – Blue giant stars
STAR NAME
Bellatrix
TABLE 4 – Dwarf stars
STAR NAME
Sirius B
Procyon B
TABLE 5
STAR TEMPERATURE
2000 – 5000
COLOR
RED
5000 – 7500
YELLOW
7500 – 11000
WHITE
11000 – 30000
BLUE
Name: __________________________________ Period: _______
Date:_____________
LAB # ___________
All labs must be completed in pencil
CLASSIFICATION of STARS
Discussion Questions: Answer the following questions in FULL AND COMPLETE sentences. The lab will
not be graded unless it follows the proper format.
1. Describe the process in which stars get their energy.
______________________________________________________________________________
______________________________________________________________________________
2. What are the four characteristics in which stars are classified on the H-R diagram (re-read the
intro for help).
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. Observe the X-axis. What do you notice is unusual about the X-axis of the H-R diagram?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4. Describe the relationship between the following using a one sentence statement: Use words
such as: increase; decrease; greater than; less than
Ex: As rain increases, plant growth increases
a. Star size (see your ESRT for this info.) and luminosity
________________________________________________________________________
________________________________________________________________________
5. How are Polaris and the Sun similar? How are they different?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
6. Our Sun is halfway through its lifecycle. Explain which stages it will evolve into during the last
half of its life (use the reading and diagram on page 1 to help you).
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Name: __________________________________ Period: _______
Date:_____________
LAB # ___________
All labs must be completed in pencil
CLASSIFICATION of STARS
Discussion Questions: KEY
1. Describe the process in which stars get their energy.
Stars get their energy by nuclear fusion. Nuclear fusion is when hydrogen atoms combine to
make heavier atoms such as helium.
2. What are the four characteristics in which stars are classified on the H-R diagram (re-read the
intro for help).
The 4 characteristics in which stars are classified are color, temperature, spectral class, and
size.
3. Observe the X-axis. What do you notice is unusual about the X-axis of the H-R diagram?
The x-axis of the H-R Diagram is unusual because the numbers are decreasing. The x-axis is
also unusually spaced.
4. Describe the relationship between the following using a one sentence statement: Use words
such as: increase; decrease; greater than; less than
Ex: As rain increases, plant growth increases
a. Star size (see your ESRT for this info.) and luminosity
As star size increases, luminosity increases.
5. How are Polaris and the Sun similar? How are they different?
Polaris and the Sun have similar temperatures, but different luminosities and sizes.
6. Our Sun is halfway through its lifecycle. Explain which stages it will evolve into during the last
half of its life (use the reading and diagram on page 1 to help you).
The Sun is currently a main sequence star which is approximately an “adult.” The Sun will age
into a giant, perhaps a super giant, and eventually a dwarf.