Lesson 3 | Evolution of Stars
Lesson 3 | Evolution of Stars
|Student Labs and Activities |Page |Appropriate For: |
|Launch Lab |47 |all students |
|Content Vocabulary |48 |all students |
|Lesson Outline |49 |all students |
|MiniLab |51 |all students |
|Content Practice A |52 |[pic] |
|Content Practice B |53 | [pic] |
|School to Home |54 |all students |
|Key Concept Builders |55 |[pic] |
|Enrichment |59 |all students |
|Challenge |60 | [pic] |
|Skill Practice |61 |all students |
|Assessment | | |
|Lesson Quiz A |63 |[pic] |
|Lesson Quiz B |64 | [pic] |
| | | |
| | | |
|[pic] |Approaching Level |[pic] |On Level |[pic] |Beyond Level |[pic] |English-Language Learner |
Teacher evaluation will determine which activities to use or modify to meet any student’s proficiency level.
46 Stars and Galaxies
Name Date Class
LESSON 3: 15 minutes
How can you identify fruits?
Flowering plants grow from seeds that they produce. Animals depend on flowering plants
for food. The function of the fruit is to disperse the seeds for plant reproduction.
Procedure
1. Read and complete a lab safety form.
2. Make a two-column table in your
Science Journal. Label the columns
Fruits and Not Fruits.
3. Examine a collection of food items.
Determine whether each item is a fruit.
Record your observations in your table.
4. Place each food item on a piece of
plastic wrap. Use a plastic or
paring knife to cut the items in half.
5. Examine the inside of each food item.
Record your observations.
Think About This
1. What observations did you make about the insides of the food items? Would you
reclassify any food item based on your observations? Explain.
2. How can the number of seeds or how they are placed in the fruit help with seed
dispersal?
3. Key Concept What role do you think a fruit has in a flowering plant’s
reproduction?
Stars and Galaxies 45
Name Date Class
LESSON 3
Evolution of Stars
Directions: Each of the sentences below is false. Make the sentence true by replacing the underlined word(s) with
a term from the list below. Write your changes on the lines provided. NOTE: You may need to change a term to its
plural form.
|black hole |nebula |neutron |
|neutron star |supernova |white dwarf |
1. Stars form deep inside black holes, which are clouds of gas
and dust.
2. When a star that no longer contains helium casts off its
gases, its core turns into a hot, dense, slowly cooling sphere
of carbon called a neutron star.
3. A supernova occurs when gravity is so great that no light
can escape.
4. Neutron stars contain a dense core of nebulae, which
are particles in the nucleus of an atom.
5. A white dwarf is an enormous explosion that destroys
a star.
6. A black hole is a dense core of neutrons that remains after
a supernova.
48 Stars and Galaxies
Name Date Class
LESSON 3
Evolution of Stars
A. Life Cycle of a Star
1. Stars have , meaning that they are born and, after
millions or billions of years, they .
2. Stars form inside a(n) , which is a cloud of gas and dust.
a. causes the densest parts of a star-forming nebula to
collapse, forming a region called a(n).
b. As they contract, protostars produce enormous amounts
of
3. A developing gets increasingly hotter over many
thousands of years, heating up the surrounding gas
and
a. The heated and dust eventually blow away, and
the becomes a visible . .
b. The gas and dust might later become or other objects
that the star.
4. A stars spends most of its life cycle on the of the
Hertzsprung-Russell diagram.
a. When a star starts hydrogen into
, it becomes a(n) star
and remains there as it continues fusing into helium.
b. A star leaves the main sequence when its supply of
has been nearly used up.
c. A massive star goes through a cycle near the end of its life in which it becomes
a(n) several times
B. End of a Star
1. All stars in the same way, but stars
in different ways.
2. -mass stars such as the Sun do not have enough mass to
fuse elements heavier than .
Stars and Galaxies 49
Name Date Class
Lesson Outline continued
3. Astronomers think that any star with a mass less than 10 times the mass of the
Sun will eventually become a(n) .
4. Stars that have a mass more than 10 times that of the Sun become a(n)
, which is an enormous explosion that destroys the star
at its center.
5. During a(n) , the collapse is so violent that the normal
spaces inside atoms are eliminated and a(n) star forms.
6. Massive stars have a force of that is so strong that the
matter gets crushed into a(n) .
C. Recycling Matter
1. The gas that give off at the
of their life cycles gets recycled; it is the material that forms new stars
and .
2. A(n) casts off hydrogen and helium, which becomes
part of a planetary ; these gases can form new
, not new , despite the
nebula’s name.
3. A(n) produces a shock wave that pushes on the gas
and in space.
a. Almost all the elements that are than hydrogen and
helium, including carbon, silicon, and oxygen, were released into the
universe by
b. The force of causes in
nebulae to clump together and eventually form new
and planets.
50 Stars and Galaxies
Name Date Class
LESSON 3: 15 minutes
How do astronomers detect black holes?
The only way astronomers can detect black holes is by studying the movement of objects
nearby. How do black holes affect nearby objects?
Procedure
1. Read and complete a lab safety form.
2. With a partner, make two stacks of
books of equal height about 25 cm
apart. Place a piece of thin cardboard
on top of the books.
3. Spread some staples over the
cardboard. Hold a magnet under the
cardboard. Observe what happens to
the staples.
4. While one student holds the magnet
in place beneath the cardboard, the
other student gently rolls a small
magnetic marble across the
cardboard. Repeat several times,
rolling the marble in different
pathways. Record your observations
in the Data and Observations section
below.
Data and Observations
Analyze and Conclude
1. Infer What did the pull of the magnet represent?
2. Cause and Effect How did the magnet affect the staples and the movement of the
marble?
3. Key Concept How do black holes affect nearby objects?
Stars and Galaxies 51
Name Date Class
LESSON 3
Evolution of Stars
Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms may be used more than once or not at all.
black hole fusion gravity massive star
nebula neutron star protostar red giant
star Sun supergiants supernova
white dwarf
1. A star forms deep inside a cloud of gas and dust called a .
2. causes the densest parts of the nebula to collapse.
3. A is formed and continues to contract.
4. The core of the protostar becomes hot and dense enough for
nuclear .
5. Eventually the surrounding gas and dust blows away and a
becomes visible.
6. Low-mass stars such as the Sun do not have enough mass to
become .
7. A turns into a red giant, a larger red giant, and then a red
supergiant.
8. After a low-mass star runs out of helium, the core is exposed and becomes
a .
9. When the Sun in our solar system runs out of fuel, it will become a
and then eventually a white dwarf.
10. A massive star does not become a . Instead it explodes.
11. A is an enormous explosion that destroys a star.
52 Stars and Galaxies
Name Date Class
LESSON 3
Evolution of Stars
Directions: Answer each question or respond to each statement on the lines provided.
1. What is a nebula, and how is it related to the formation of a star?
2. How does a protostar become a star?
3. How long does a star remain on the main sequence of the Hertzsprung-Russell diagram?
4. How does the mass of a star relate to the time it stays on the Hertzsprung-Russell diagram?
5. What steps does a massive star go through to become a red supergiant?
6. Describe the final stages of the Sun.
7. What happens to stars with more than 10 times the mass of the Sun?
8. What happens to the gas that escapes into space at the end of a star’s life cycle?
Stars and Galaxies 53
Name Date Class
LESSON 3
Evolution of Stars
Directions: Use your textbook to complete the activity.
For this activity, you will need one sheet of construction paper in each of several colors, such
as black, yellow, orange, red, and white. You will also need scissors, glue, and a compass for
drawing circles.
1. Review the information in your book about the Sun’s life cycle. List the stages of the
Sun’s life cycle here, in the correct order.
2. You will use the sheets of construction paper to make a time line of the various stages
in the Sun’s life cycle. The black sheet of paper will represent space. Use the compass to
make the Sun in various sizes depending on its stage. Choose appropriate colors as well.
For example, the main sequence Sun of today would be yellow. The Sun as a red giant
would be red and larger than the yellow sun.
3. Carefully cut out the Suns and arrange them in order on the sheet of black construction
paper. When you are satisfied with your arrangement, glue the Suns in place.
4. Describe the life cycle of the Sun, using your time line.
54 Stars and Galaxies
Name Date Class
LESSON 3
Evolution of Stars
Key Concept How do stars form?
Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the
statement is false, change the underlined word(s) to make it t rue. Write your changes on the lines provided.
1. The cloud of gas and dust in which a star forms is called a galaxy.
2 The way in which a star forms does not depend on its mass.
3. Protostars form when gravity causes dense parts of star-forming nebulae to
expand.
4. Protostars contract until their cores are cold and dense enough for nuclear
fusion.
5. A nebula glows brightly during the star-forming process.
6. The gas and dust that blow away from a protostar might later become planets
or other satellites.
7. All stars form in the same way. But stars die in different ways, depending on
their luminosity.
8. Star-forming nebulae are cold, dense, and dark.
9. A protostar that is contracting produces enormous amounts of internal energy.
10. A protostar becomes invisible when the gas and dust that surrounds it blows
away.
11. A star becomes a main-sequence star on the Hertzsprung-Russell diagram when
it begins to fuse hydrogen into helium.
12. The time that a star stays on the perimeter of the Hertzsprung-Russell diagram
depends on its mass.
Stars and Galaxies 55
Name Date Class
LESSON 3
Evolution of Stars
Key Concept How does a star’s mass affect its evolution?
Directions: Number the events in each chart from 1 to 5 to show the sequence in the life of each type of star.
| |Medium Mass |
| |red giant star |
| |star-forming nebula |
| |dead star |
| |medium-mass protostar |
| |white dwarf |
| |High Mass |
| |massive protostar |
| |red supergiant |
| |formation of a neutron star or a black hole |
| |star-forming nebula |
| |explodes as a supernova |
Directions: Circle the term in parentheses that correctly completes each sentence.
1. Lower-mass stars such as the Sun do not have enough (hydrogen, mass) to become
supergiants.
2. High-mass stars collapse and explode as (protostars, supernovae).
3. A lower-mass star becomes a (white dwarf, black hole) instead of a supernova.
4. A supernova destroys a massive star and leaves behind a (red giant, neutron star).
5. A neutron star collapses into a black hole because of the force of (fusion, gravity).
56 Stars and Galaxies
Name Date Class
LESSON 3
Evolution of Stars
Key Concept How does a star’s mass affect its evolution?
Directions: Complete each concept map by writing the correct phrase from the list in the space provided.
• can become a black hole
• can become a neutron star
• collapses and explodes
• dies more slowly
• experiences a supernova
• first becomes a red giant
• ends up a white dwarf
Stars and Galaxies 57
Name Date Class
LESSON 3
Evolution of Stars
Key Concept How is star matter recycled in space?
Directions: On each line, write the term from the word bank that correctly completes each sentence. Some terms
may be used more than once or not at all.
core black holes gravity
hydrogen nuclear fusion planetary nebula
planets remnant space
stars supernova white dwarf
1. When a star becomes a , it casts off hydrogen and helium
gases in its outer layers.
2. Much of a star’s gas escapes into at the end of its life cycle.
3. A is the expanding matter cast off by a star that is becoming
a white dwarf.
4. Originally, astronomers thought planetary nebulae were regions where
were forming.
5. The gases in a planetary nebula can be used to form new .
6. A supernova releases an expanding cloud of dust and gas called a
supernova .
7. Almost all elements other than hydrogen and helium were formed during
explosions.
8. The intense heat during a supernova explosion causes iron elements in the
to fuse together and form new elements.
9. Gases and other matter from planetary nebulae and
remnants can come together to form new stars and planets.
10. is the force that causes new stars to form from recycled gases
and other materials.
58 Stars and Galaxies
Name Date Class
LESSON 3
Into the Darkness
Scientists describe a black hole as a
collection of matter with a gravitational
pull that is so strong that nothing, not
even light, can escape from it. In the 1700s,
researchers used Newton’s ideas about
gravity to reach the conclusion that some
stars might be so big that light could never
escape from them. Then, Einstein’s general
theory of relativity appeared. Using
Einstein’s relativity equations, Karl
Schwarzchild predicted the existence of a
dense object into which other objects could
fall but out of which no objects could ever
come. Today, we call Schwarzchild’s object
a black hole.
A Magic Sphere?
Schwarzchild also predicted a magic
sphere around such an object where gravity
is so powerful that nothing can move
outward. This distance is referred to
today as the event horizon, because no
information about events occurring inside
this distance can ever reach us. Unable to
withstand the pull of gravity, all material
that goes past the event horizon is crushed
until it becomes a point of infinite density
occupying virtually no space. This point is
known as the singularity: Every black hole
has a singularity at its center.
They Come in All Sizes
There are three main types of black holes.
Stellar-mass black holes, the smallest and
most common, are the explosions of massive
stars. Medium-size black holes are probably
the result of mergers of smaller black holes,
and supermassive black holes have huge
masses and exist in the center of galaxies.
How Do We Know They Exist?
In 2002, R. Schodel and his research
team reported the first observation of the
orbit of a star around the black hole at the
center of our galaxy, the Milky Way. For
many years, astronomers have put forth
the theory that supermassive black holes—
more than a million times the mass of the
Sun—exist in nearly every galaxy. No one,
however, had found conclusive evidence
that supermassive black holes exist.
The Sun takes 230 million years to circle
the Milky Way, but the star that Schodel
reports on will complete its orbit around
the black hole in 15 years. The speed of the
star’s orbit indicates that it is getting closer
and closer to a huge gravitational pull. For
scientists, this orbit provides the evidence
that supermassive black holes exist.
Applying Critical-Thinking Skills
Directions: Answer each question or respond to each statement.
1. Describe what would be happening to you if you were falling into a massive black
hole. As you approach the event horizon, feet first, your body begins to be stretched
out. Why is that happening? What happens at the event horizon?
2. Predict what will happen when you travel past the event horizon.
Stars and Galaxies 59
Name Date Class
LESSON 3
The Lives of Stars
Stars exist because of gravity. The mutual gravitational attraction of particles in a thin,
gaseous cloud causes the cloud to collapse. As the cloud is squeezed to extremely high
pressures, its temperature rises, igniting its nuclear reactions, and a star is born.
Research and Diagram the Evolution of Stars
1. Research the evolutionary stages of three types of stars.
a. low-mass stars
b. medium-mass stars (about the size of the Sun)
c. massive stars
2. On chart paper, draw a diagram of the evolutionary stages of each type of star, beginning
each one with a nebula. Draw the stages in color and label each stage.
3. On each diagram, label the star in its main-sequence stage with its temperature range in
degrees Kelvin.
Research Notes:
60 Stars and Galaxies
Name Date Class
Make and Use Graphs LESSON 3: 45 minutes
How can graphing data help you understand stars?
How can you make sense of everything in the universe? Graphs help you organize information.
The Hertzsprung-Russell diagram is a graph that plots the color, or temperature, of stars against
their luminosities. What can you learn about stars by plotting them on a graph similar to the
H-R diagram?
Materials
colored adhesive stars of various sizes
Learn It
Displaying information on graphs makes it
easier to see how objects are related. Lines
on graphs show you patterns and enable you
to make predictions. Graphs display a lot of
information in an easily understandable
form. In this activity, you will make and
use graphs, plotting the temperature, the
color, and the mass of stars.
Try It
1. Using the graph paper, draw a graph
like the one shown in your book.
graph paper
2. Use the color and temperature data in
the table below to plot the position of
each star on your graph. Mark the points
by attaching adhesive stars to the graph.
3. If stars have similar data, plot them in
a cluster. Label each star with its name.
4. Draw a curve that joins the data points
as smoothly as possible.
5. Make another graph and plot
temperature v. mass of the stars in the
table. Use the grid on the next page.
|Star |Color |Temperature (K) |Mass in solar masses |
|Sun |Yellow |5,700 |1 |
|Alnilam |Blue-white |27,000 |40 |
|Altair |White |8,000 |1.9 |
|Alpha Centauri A |Yellow |6,000 |1.08 |
|Alpha Centauri B |Orange |4,370 |0.68 |
|Barnard’s Star |Red |3,100 |0.1 |
|Epsilon Eridani |Orange |4,830 |0.78 |
|Hadar |Blue-white |25,500 |10.5 |
|Proxima Centauri |Red |3,000 |0.12 |
|Regulus |White |11,000 |8 |
|Sirius A |White |9,500 |2.6 |
|Spica |Blue-white |22,000 |10.5 |
|Vega |White |9,900 |3 |
Stars and Galaxies 61
Name Date Class
Skill Practice continued
Apply It
6. All of the stars on your graph are main-sequence stars. What is the relationship
between the color and the temperature of a main-sequence star?
7. What is the relationship between the mass and the temperature of a main-sequence
star? How are color and mass related?
8. Key Concept Which star would be the most likely to eventually form a black
hole? Why?
62 Stars and Galaxies
Name Date Class
LESSON 3
Evolution of Stars
True or False
Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the
statement is false, change the underlined word(s) to make it true. Write your changes on the lines provided.
1. A cold, dense, dark cloud of gas and dust in space is called a nebula.
2. The gravity of a white dwarf is so great that light cannot escape it.
3. A supernova is the explosion of a massive star.
4. A dense core that remains after a supernova is called a black hole.
5. Stars move onto the main sequence when they begin to fuse hydrogen into carbon.
Multiple Choice
Directions: On the line before each question, write the letter of the correct answer.
6. Which sequence correctly shows how stars form?
A. nebula forms → nebula collapses → protostar forms → fusion begins
B. protostar forms → nebula forms → fusion begins → nebula collapses
C. nebula forms → protostar forms → nebula collapses → fusion begins
7. Which statement is true of stellar evolution?
A. Black holes become neutrons stars.
B. Low-mass stars become supergiants.
C. The most massive stars do not become white dwarfs.
8. How do stars recycle matter?
A. They stay on the main sequence.
B. Black holes form and recycle stellar gas for new stars.
C. Gravity pulls together gases and matter from old stars to create new ones.
Stars and Galaxies 63
Name Date Class
LESSON 3
Evolution of Stars
Completion
Directions: On each line, write the term from the word bank that correctly completes each sentence. Not all
terms are used
|black hole |main sequence star |nebula |neutron star |
|planetary |nebula protostar |red giant |red supergiant |
|supernovae |white dwarf | | |
1. A is a hot, dense, slowly cooling sphere of carbon that
forms at the end of the life cycle of stars such as the Sun.
2. A star is born deep inside a cloud of gas and dust called a .
3. Stars that are more than 10 times more massive than the Sun will explode
as .
4. A forms when the most massive stars collapse.
5. A small, extremely dense core of neutrons that remains after a supernova is called
a .
Short Answer
Directions: Respond to each statement on the lines provided.
6. Summarize the formation of a star.
7. Describe how a star’s mass affects the length of its life cycle.
8. Explain how star matter is recycled.
64 Stars and Galaxies
-----------------------
Launch Lab
Content Vocabulary
Lesson Outline
Mini Lab
Content Practice A
Content Practice B
School to Home
Key Concept Builder
Key Concept Builder
Key Concept Builder
High-Mass Stars
Low- Mass Stars
Key Concept Builder
Enrichment
Challenge
Skill Practice
Lesson Quiz A
Lesson Quiz B
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