The Life Cycle of Stars
Purpose:
In this series of activities you will investigate the process of nuclear fusion explained by Einstein's famous equation E = MC2 and
learn how mass, in the form of hydrogen atoms, is converted to helium and causes a release of energy that makes stars shine!
Cool!! Or hot? You will also understand the forces involved in stars that maintain this nuclear reaction and how these forces
change as the star ages. You will explore the stages stars progress through from birth to death and how the death of a star
depends on its initial mass. You will also build and interpret Hertzsprung-Russell diagrams and learn how they can be used to
classify the life cycle stage of a star by its luminosity, temperature, magnitude, and spectral class. Finally, we will go deeper into
space and will discover how infrared, x-ray, and gamma ray telescopes are being used to detect the life cycle stages of stars. This
is an independent learning module so do your best to understand what you are learning or doing. Ask questions to clarify! The
summative assessment is at the end. Don’t forget to click on the hyperlinks! Good luck in your adventures!
Part 1
Task #1: You will begin your Webquest by learning how to identify stars by their
magnitude, color, temperature, and spectral class.
Click Stars: Lights in the Sky and write out the questions and answers to the following on a
sheet of white construction paper to be turned in. Be sure your name and period are on it.
1) What is the name of the brightest star in our night sky? In the known universe?
Sun, the center of our solar system, is the brightest stat that we can see
Sirius, also known as the Dog Star, is the brightest star in the sky. Its name comes from the Greek
word for scorching.
2) - What is its absolute magnitude?
Absolute magnitude is the measure of celestial object’s intrinsic brightness.
3) - What is the difference between apparent and absolute magnitude?
Apparent magnitude is the brightness that you see stars or planet on earth, Absolute magnitude
is the apparent of the star when it’s vied from 332.6 light years away.
4) - Are the brightest stars low magnitude or high?
The brightest stars have low magnitude.
5) - How much does the brightness of a star change with each change in magnitude of one?
The number is defined as the sixth root of 100. It's approximately 2.1543 times as bright.
6) - Do a search on the Internet for "brightest stars" and make a top 10 list on your construction
paper of the names of the 10 brightest stars in the known universe and their absolute
magnitude.
1. Sirius
Sirius, also known as the Dog Star, is the brightest star in the sky. Its name
comes from the Greek word for scorching.
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Distance: 8.6 LY
Spectral Type: A1Vm
2. Canopus
Named either for an ancient city in northern Egypt or the helmsman for
Menelaus, Canopus is the second brightest star in the sky.
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Distance: 74 LY
Spectral Type: F0II
3. Rigil Kentaurus
Rigel Kentaurus, also known as Alpha Centauri, is the third brightest star in the
sky. Its name literally means foot of the centaur.
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Distance: 4.3 LY
Spectral Type: G2V
4. Arcturus
Arcturus is the brightest star in the constellation Bootes, which is one of the
oldest constellations in the night sky. It is the 4th-brightest star in the entire
sky.
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Distance: 34 LY
Spectral Type: 5IIIFe-0.5
5. Vega
Vega is the fifth brightest star in the sky. Its name comes from the Arabic for the
swooping eagle. Vega is about 25 light-years from Earth.
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Distance: 25 LY
Spectral Type: A0Va
6. Capella
The sixth brightest star in the sky, Capella's name is from the Latin for little shegoat. Capella is a yellow giant star, like our own sun, but much larger.
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Distance: 41 LY
Spectral Type: G5IIIe+G0III
7. Rigel
The seventh brightest star in the sky, Rigel's name is from the Arabic for foot,
indicating its place in the constellation Orion. It is a blue supergiant and part of a
4 star system.
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Distance: 1400 LY
Spectral Type: B8Ia
8. Procyon
Procyon is the eighth brightest star night sky. It is a yellow-white star and at
11.4 light years, one of the closer stars to Earth.
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Distance: 11.4 LY
Spectral Type: F5IV-V
9. Achernar
The ninth brightest star night sky is Achernar. It is a bluish-white white
supergiant star that is about 69 light years from Earth.
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Distance: 69 LY
Spectral Type: B3Vpe
10. Betelgeuse
Betelgeuse is the tenth brightest star in the sky. It is a red supergiant about
13,000 times brighter than our sun and over 1000 times larger. If you placed
Betelgeuse in the place of our sun, it would extend past the orbit of Jupiter.
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Distance: ~1400 LY
Spectral Type: M1-2Ia-Iab
7) - Finally, design a creatively colored diagram on your paper that displays the colors of the
hottest stars on the left to the coolest stars on the right using colored pencils. Stars are grouped
into spectral classes based on a range of temperatures they fall into. Label the spectral classes
(O, B, A, F, G, K, M) appropriately under each star color in your diagram.
To complete Task #1, come up with a clever sentence or phrase (the first letter of each word in
your phrase is one spectral class letter) to help you remember the order of the spectral classes
and write it under your diagram on your paper. Be sure to know it when you turn your paper in
as you will be asked about the spectral class!
Answer the following few more questions and write the answers on your paper.
8) - What color is the brightest star? Blue
9) - What color is the coolest star? Black dwarf
10) -What color is our sun? White
11) -What spectral class of stars is the hottest? O
12) -What spectral class of stars is the coolest? M
13) - What spectral class is our sun? G2V
Task #2: Continue to read on to the section: A Nuclear Furnace on the same webpage. The
animation there shows how stars fuse different forms of hydrogen (deuterium and tritium) to
form helium. Your task is to design a 3-D model of this nuclear reaction. You might want to use
some pom-pom balls or other round objects supplied by the teacher to represent the different
atoms in the reaction. You need two different colors. Glue these on an 5x7 index card and label
the names of the atoms, particles and processes and use arrows to show the progression of the
reaction. Be colorful and creative! Make sure you understand what is happening and why. Show
your teacher and be prepared to answer questions.
Task #3: Go to The Life and Death of Stars. Build illustrated notes in your journal. Read
the short section on "Where are stars born" and see pictures of the protostars of M16: The Eagle
Nebula and other nebulae (stars in formation) on this page. Continue by reading up on Main
Sequence Stars and find out how our sun compares in mass to other stars like Sirius, and
Proxima Centauri. Based on its mass, will our sun be around for a while? Approximately how
long before our sun consumes the inner planets of our solar system?
Realize that once our Sun starts to run out of hydrogen fuel and has exhausted its ability to fuse
other elements like carbon and oxygen, it will become a red giant and expand in size to envelope
the Earth. And surprisingly, the larger the mass of the star, the quicker it burns its fuel sources
and the shorter its lifespan. Also see and read about the Hubble Space Telescope and then
explore the site looking for Image Tour of a star called V838 Monocerotis. Why did it die this
way? Why do the stars have 4 points in Hubble Photographs?
Cool! No, hot! How does mass effect the stars life cycle? Be prepared to share your
understandings and the answer to this question with your teacher.