Making an H-R Diagram
BACKGOUND INFORMATION:
Stars in the sky are not created equal and are composed of different materials, different
temperatures, different brightness, different sizes, and different distances from Earth. A star’s mass
dictates how bright it will be, how long it will live, its temperature and its size. The Sun is the center of
our solar system and is very bright to us on Earth. Other stars in our galaxy are brighter, but we don’t
see them the same. The apparent magnitude of a star is the amount of light received on Earth or
the brightness of the star as seen from Earth. This is different than the absolute magnitude because
the absolute magnitude is based upon the amount of light the star gives off. This difference is the
reason Sirius looks brighter than Rigel but Rigel is farther away from Earth.
Two scientists made important observations about the stars in the sky. They developed a
graph to show the relationship between the temperature and brightness of stars. This diagram is
called an Hertzsprung-Russel (H-R) Diagram. There are four main categories of stars that appear
on the H-R Diagram. These categories include Supergiants, Giants, Main Sequence, and White
Dwarf stars.
PURPOSE:
1. To create a simple version of the H-R diagram.
2. To plot stars on this H-R diagram using supplied data.
3. To become more familiar with terminology, thus enhancing knowledge related to star
characteristics.
4. To determine relationships and apply scientific concepts.
MATERIALS:



graph paper
data on several selected stars
crayons or colored pencils
PROCEDURES:
1. Using the supplied data, plot the following stars; carefully insert each star name next to each
plot made. (See next page for data.)
2. Using colored pencils or crayons, not markers, color may now be used to shade in the
background of the finished graph. The following color/temperature scheme is recommended:
COLOR KEY
Star Temperature (C°)
2,000-3,500
3,500 - 5,000
5,000- 6,000
6,000-7,500
7,500 - 11,000
11,000- 21,000+
Color
red
orange
yellow
white-yellow
white
blue/white
3. Draw a dotted line around those stars you predict belong to the White Dwarf category, Main
Sequence category, Super giants category, and Giants category. Label each category
appropriately.
4. Answer the questions that follow using complete sentences.
DATA TO PLOT
Absolute
Magnitude
Temp
Absolute
Magnitude
Temp
Sun
4.8
6000
Sirius A
1.4
10,000
Canopus
-3.1
7000
Arcturus
-0.4
4600
Alpha
Centauri A
4.3
6000
Beta Centauri
-5.1
25,500
Capella
-0.6
5000
Rigel
-7.2
12,000
Procyon A
2.6
7000
Betelgeuse
-5.7
3200
Achemar
-2.4
21,000
Vega
0.5
9900
Altair
2.2
8000
Regulus
-0.8
13,200
Spica
-3.4
25,500
Antares
-5.2
3000
Polaris
-4.6
6000
Pollux
1.0
5000
Sirius B
11.4
8000
Procyon B
13.1
6,500
Deneb
-7.2
9000
Aldebaran
-0.2
4000
Barnard’s Star
13.2
2,600
Alpha
Centauri B
5.8
5000
Star Name
Star Name
OBSERVATIONS/QUESTIONS: Use complete sentences to answer questions.
1. What characteristics can be used to describe stars?
2. According to both your graph and data, describe the Sun, recognizing: color, absolute magnitude,
temperature and classification.
3. How much brighter is Rigel than the Sun?
4. Describe what happens to a star's color as its temperature decreases from 12,000 C to 3,000 C.
5. Which star is much brighter than Alpha Centauri B but the same temperature?
6. What appears to be the relationship between a star's temperature and its absolute magnitude for
the main sequence stars?
Name:
Period:
Date:
H-R Diagram
-8
--6
-4
ABSOLUTE MAGNITUDE
-2
0
2
4
6
8
10
12
14
24,000
21,000
18,000
15,000
12,000
9,000
6,000
Increasing
3,000
TEMPERATURE (C)
OBSERVATIONS/QUESTIONS: Use complete sentences to answer questions.
1. What characteristics can be used to describe stars?
2. According to both your graph and data, describe the Sun, recognizing: color, absolute magnitude,
temperature and classification.
3. How much brighter is Rigel than the Sun?
4. Describe what happens to a star's color as its temperature decreases from 12,000 C to 3,000 C.
5. Which star is much brighter than Alpha Centauri B but the same temperature?
6. What appears to be the relationship between a star's temperature and its absolute magnitude for
the main sequence stars?
0