Name: ____________________________________________ Date:_________________
Investigation 13.2
Star Life Cycle and the H-R Diagram
How can we use an H-R diagram to know where a star is in its life cycle?
Just like humans, stars go through a life cycle. Over the course of their lives, stars change in ways that make each
stage different and recognizable. A useful way to organize this information is in a Hertzsprung-Russell diagram,
also called an H-R diagram. In this investigation you will learn how to identify stars of different types and ages
using the information in an H-R diagram.
The H-R diagram
For astronomers, a graph that displays a star’s luminosity on the y-axis and its surface temperature on the x-axis
sets up an extremely useful diagram called a Hertzsprung-Russell, or H-R diagram. In 1910, Ejnar Hertzsprung and
Henry Norris Russell discovered that when all of the known stars were put on their graph, several obvious groups
became apparent. By examining the differences in these groups, later astronomers were able to realize that the
groups were best described as stars in different periods in their life cycle, rather than completely different types
of stars. Just as infants, adolescents and adults are in different stages of the human life cycle, main sequence, red
giants, supergiants, and white dwarfs are stars in different stages of the life cycle of stars.
Making observations
a. Describe the qualities and the location of white dwarf stars based on the H-R diagram.
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They are 100x smaller than our sun. They are different colors. Located at the bottom of the chart.
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b. Describe the qualities and the location of supergiant stars based on the H-R diagram.
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They are 1000x bigger than our sun and are different colors if you
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look at the bottom of the chart
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c. Describe the qualities and the location of main sequence stars based on the H-R diagram.
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Some are the same size as the sun and others are 1/10th the size of the
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sun it looks like they are all different colors if you look at the bottom of the
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chart
d. Describe the qualities and the location of red giant stars based on the H-R diagram.
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They are 10x bigger than out sun and they are both the
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same color if you look at the bottom of the chart
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Investigation Answer Sheet: Star Life Cycle and the H-R Diagram p.1 © 2014 CPO Science • May be duplicated for classroom use.
Graphing star data
Table 1 contains data concerning the luminosity and surface temperature of 12 stars. Plot each star’s data on the
grid and label each star (A–L) on Table 2.
Table 1: Luminosity and surface temperature data
Name Luminosity Surface temperature (°C)
A Proxima Centauri 0.0017 3,100
B Rigel 66,000 11,000
C Sirius A 25.4 9,500
D Sirius B 0.026 25,000
E Aldebaran 350 3,600
F Antares 65,000 3,200
G Arcturus 250 4,700
H Betelgeuse 135,000 3,300
I Procyon A 8 6,200
J Procyon B 0.0005 7,500
K Pi Andromedae A 800 16,000
L 40 Eridani B 0.013 12,000
Star data graph
1,000,000
100,000— h
10,000 b f
1,000—
100 k g e
10— c
i
0.1—
0.01 d l
0.001— A
0.0001 j
0.00001—
30,000 15,000 7,500 3750
Investigation Answer Sheet: Star Life Cycle and the H-R Diagram p.2 © 2014 CPO Science • May be duplicated for classroom use.
Examining your graph
Compare your graph of star data to the H-R diagram from part 1. Look for groupings on your graph that are similar
to the H-R diagram and answer the following questions.
a. Which stars on your graph are located in the area associated with main sequence stars?
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b,f
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b. Which stars on your graph are located in the area associated with supergiant stars?
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none
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c. Which stars on your graph are located in the area associated with red giant stars?
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Rigel and Antares
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d. Which stars on your graph are located in the area associated with white dwarf stars?
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Sirius B and Procyon A
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e. Can you identify which group a star will fit into just by looking at its temperature alone? Its luminosity alone?
Explain your answer.
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No because it seems like the luminosity is random and not based on size.
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Groupings on the H-R diagram and the life cycle of stars
Even though a star is not alive, it goes through a “life cycle” similar to living things. The groups that appear in
different sections of the H-R diagram are in different phases of their life cycle.
a. In what part of their life cycle are main sequence stars; beginning, middle, or end, or some combination of
those stages?
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not sure
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Investigation Answer Sheet: Star Life Cycle and the H-R Diagram p.3 © 2014 CPO Science • May be duplicated for classroom use.
b. What characteristics are common to main sequence stars?
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10,000-20,000 degrees and same size as sun
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c. How are red giant and supergiant stars similar? How are they different? Include how each one fits into the life
cycle in some part your answer.
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red giants are red and 10x bigger than the sun and 10x smaller than supergiants
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d. In what part of their life cycle are white dwarf stars; beginning, middle, or end, or some combination of those
stages?
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not sure
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e. What characteristics make white dwarf stars different from main sequence stars?
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their size and tempature
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f. What is the difference between a white dwarf star and a red giant star?
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the size and the surface tempature
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g. Where is the Sun located on the H-R diagram and what group is it in?
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it located with class g and is a main sequnce star
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h. Where would a black hole be located on an H-R diagram?
the very top and im not sure what surface temp would be
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Investigation Answer Sheet: Star Life Cycle and the H-R Diagram p.4 © 2014 CPO Science • May be duplicated for classroom use.
white dwarf red giant red super giant
planetary nebula supernova explosion
white dwarf
neutron star
black hole
