Download Planets, Moons, and Stars

CHAPTER 8
Planets, Moons,
and Stars
Lesson 1
The Sun and Earth . .
316
Lesson 2
The Moon
and Earth . . . . . . . . . .
326
Lesson 3
The Planets . . . . . . . .
336
Lesson 4
The Stars
. . . . . . . . . . 346
What objects move through space,
and how do they move?
314
Saturn and one of its moons, Tethys
Key Vocabulary
rotate
to spin (p. 318)
More Vocabulary
axis, p. 319
orbit, p. 320
star, p. 322
crater, p. 332
telescope, p. 342
revolve
to move around another
object (p. 320)
space probe, p. 342
phase
each shape of the Moon we
see (p. 328)
solar system
a system made up of a star
and the objects that move
around it (p. 338)
planet
a large body of rock or gas
with a nearly round shape
that revolves around a star
(p. 338)
constellation
a group of stars that seem
to form a picture (p. 349)
315
Lesson 1
The Sun
and Earth
The Sun seems to rise from behind this
tree. The tree blocks the Sun’s light and
forms a long shadow. How do shadows
change during the day?
316
ENGAGE
How do shadows change
throughout the day?
Materials
Form a Hypothesis
chalk
How does the Sun’s location affect the length of
shadows cast on the ground? How does it affect
their position? Write a hypothesis.
Test Your Hypothesis
Work in pairs outside on a sunny morning.
Use chalk to mark an X on the pavement.
Have your partner stand on the X.
Trace your partner’s shadow.
measuring tape
Step
Measure Use a measuring tape to find
the length of the shadow. Observe the
location of the Sun and the shadow.
Record the data in a table.
Be Careful. Never look directly
at the Sun.
Observe Repeat steps 2 and 3 at
midday and in the afternoon. How did the
Sun’s location and the shadow change?
Draw Conclusions
Interpret Data When was the shadow
shortest? When was the shadow longest?
How did the Sun’s position change?
Step
Time
Infer What caused the shadow to
change position and length?
Explore More
Experiment How can you find out in which
month the Sun’s position appears highest in
the sky? Lowest?
Length and
Location
Location of
of Sun
Shadow
Morning
Midday
Afternoon
317
EXPLORE
Why is there day and night?
Main Idea
Earth rotates and revolves
around the Sun. Earth’s
movement causes day and
night and the seasons.
Vocabulary
rotate, p. 318
axis, p. 319
revolve, p. 320
orbit, p. 320
star, p. 322
-Glossary
at
www.macmillanmh.com
As you read this page, you are moving
through space. All the other things on Earth
are moving, too. Earth rotates (ROH•tayts), or
spins, like a giant top in space.
As Earth rotates, we see the Sun in a
different place in the sky. At sunrise, the Sun
is low in the eastern sky. The Sun’s light casts
long shadows. At midday, the Sun is high in
the sky. Shadows are short then. At sunset, the
Sun is low in the western sky and shadows are
long again. The Sun seems to move in the sky,
but it does not. Earth does all the moving!
The Sun’s Position in the Sky
sunrise
Reading Skill
Sequence
east
west
midday
Technology
Explore day and night with the
Secret Agents.
east
The Sun seems to rise
in the east and set in
the west. Looking at
these pictures, you
are facing south. 318
EXPLAIN
west
sunset
east
west
Day and Night
axis
Sun
rotating
Earth
As Earth rotates on its imaginary
axis, we have day and night.
Earth’s rotation causes day
and night. As Earth rotates, one
side of Earth faces the Sun. This
side has daytime. At the same
time, the other side of Earth faces
away from the Sun. This side has
nighttime. Earth keeps spinning.
Day becomes night for one side of
Earth. Night becomes day for the
other side of Earth. This happens
over and over again.
It takes 24 hours for Earth to
make one complete turn on its axis
(AK•sis). An axis is a line through
the center of a spinning object.
One complete turn is one day. We
think of a day as daytime hours.
However, a day is made up of
daytime and nighttime.
Model Earth’s Rotation
Make a Model
Carefully push a
pencil through
a foam ball. The
ball represents
Earth. The pencil
represents Earth’s
axis. Press a paper
clip into the side of
the ball. The paper
clip represents you.
Observe Shine a
light on the paper clip.
The light represents the Sun.
On the model, where is it day?
Observe Rotate the pencil so
the paper clip faces away from
the light. Where is it night?
Interpret Data What does this
model help to show?
Quick Check
Sequence How does the Sun
appear to move across the sky?
Critical Thinking What might
happen if Earth did not rotate?
319
EXPLAIN
Why are there seasons?
Earth rotates on its axis. It also revolves (ri•VOLVZ)
around the Sun. To revolve means to move around
another object. Earth revolves around the Sun in a
regular path called an orbit (AWR•bit). It takes Earth
about 365 days to make one trip around the Sun. We
call this one year.
Seasons change as Earth revolves because of Earth’s
tilted axis. Earth’s axis is not straight up and down
compared with its orbit. For part of Earth’s orbit,
the Northern Hemisphere, or upper half of Earth, is
tilted toward the Sun. The Northern Hemisphere has
summer. At the same time, the Southern Hemisphere,
or lower half of Earth, is tilted away from the Sun.
The Southern Hemisphere has winter.
Seasons in the Northern Hemisphere
spring
Northern
Hemisphere
summer
Southern
Hemisphere
320
EXPLAIN
winter
fall
At other times, the Northern Hemisphere
is tilted away from the Sun and has winter.
At the same time, the Southern Hemisphere
is tilted toward the Sun and has summer. The
diagram can help you see this.
The Northern Hemisphere gets the most
light and heat from the Sun in summer. Days
are longer. Temperatures are warmer than in
any other season. As Earth continues its orbit,
the days get shorter and cooler. Fall begins.
summer
fall
The Northern Hemisphere gets the least
light and heat from the Sun in winter. Days are
shorter. Temperatures are cooler than in any
other season. As Earth continues its orbit, the
days get longer and warmer. Spring begins.
winter
Read a Diagram
What is the same about Earth’s axis as
it moves around the Sun?
Clue: Compare the drawings of Earth’s
axis for each of the four seasons.
spring
Watch how seasons
change at
www.macmillanmh.com
Quick Check
Sequence Which season
comes before fall?
Critical Thinking How would
seasons change if Earth moved
more slowly around the Sun?
Like many living things,
this tree changes
through the seasons.
321
EXPLAIN
What is the Sun like?
The Sun is a star. A star is a ball of hot, glowing
gases. The temperature inside the Sun is about
59 million degrees Fahrenheit (15 million degrees
Celsius). This is hot enough to melt Earth!
The Sun is about 150 million
kilometers (93 million miles)
away from Earth. If you could
travel there by car on a
highway, it would take
more than 160 years.
Even though the Sun
is that far away, it
provides Earth with
light and heat. Life
on Earth could not
exist without the Sun.
Plants could not grow.
Earth would freeze.
The Sun sometimes has violent,
fiery explosions that fly off into
space. They are called solar flares. Quick Check
Sequence What would happen to Earth if the
Sun’s light were blocked for many years?
Critical Thinking Do you think that people
could travel to the Sun? Explain your answer.
322
EXPLAIN
It would take 109 Earths to fit across the Sun.
Visual Summary
Earth rotates on
its axis. This causes
day and night.
Think, Talk, and Write
Main Idea What causes day
and night?
Vocabulary What is a star? Give
an example.
Seasons change
because Earth
revolves around the
Sun and is tilted on
its axis.
Sequence How do seasons change
in the Northern Hemisphere?
The Sun is a star that
supplies Earth with
light and heat.
Critical Thinking How would the
seasons be different if Earth were
not tilted on its axis?
Make a
Study Guide
Test Prep Why are there seasons?
Make a Trifold Book.
Use it to summarize
what you learned
about the Sun
and Earth.
Math Link
Use a Calendar
Use a calendar to find out when
the next season begins. What is
the date? How many days from
now is that?
Choose the BEST answer.
A Earth rotates on its axis and
revolves around the Sun.
B Earth has a tilted axis and revolves
around the Sun.
C The Sun revolves around Earth.
D Earth’s distance from the
Sun changes.
Health Link
Sun Safety
Find out how sunlight can benefit
human health. How can it be
harmful to human health? How can
people avoid the harmful effects of
sunlight? Write a report.
-Review Summaries and quizzes online at www.macmillanmh.com
323
EVALUATE
Seasons Where You Live
You have learned about seasons.
Now think about what the seasons
are like in your state. Do seasons have
different kinds of weather? Does it
snow in the winter? How hot is it in
the summer? Think about the things
you do during different seasons.
Personal Narrative
A good personal narrative
tells a story from
the writer’s personal
experience
expresses the writer’s
feelings
tells events in an order
that makes sense
Write About It
Personal Narrative Choose a season.
Tell a true story about something you
did during that season. Explain why
you still remember the event. How
did it make you feel? Describe what
the weather was like.
-Journal Write about it online at www.macmillanmh.com
324
EXTEND
Converting Hours to Minutes
Daytime is longer in summer
than it is in winter. Look at the
table below. It shows the number
of daylight hours for summer and
winter in Boston, Massachusetts.
Longest and Shortest Day in Boston
Date
Approximate
Hours of Daylight
June 21
15
December 21
10
Convert Hours
Multiply the number of
hours by the number of
minutes there are in one
hour. There are 60 minutes
(min) in one hour (h).
Example:
5 h x 60 min/h = 300 min
Solve It
How long is Boston’s longest day in minutes? How
long is the shortest day in minutes? What is the
difference in minutes between the longest day and
the shortest day?
325
EXTEND
Lesson 2
The Moon
and Earth
St. Louis, Missouri
The Moon does not look the same today
as it did yesterday. How will it look in one
week? Does the Moon’s shape really change?
326
ENGAGE
How does the Moon’s shape
seem to change?
Make a Prediction
Step
How will the Moon seem to change during
one school week? Write a prediction.
Test Your Prediction
Observe Work with an adult. Look at
the Moon each night for one school week.
You can also use the Internet to find out
what the Moon looks like each night.
Communicate Record what the Moon
looks like each night. Also record where
the Moon is in the sky and the time that
you observed it.
Draw Conclusions
Interpret Data How did the Moon’s
shape seem to change each night? How
does its location seem to change?
Predict What will the Moon’s shape look
like for the next few nights?
Step
Day
Monday
Explore More
Tuesday
Experiment How does the Moon’s shape
Wednesday
and position in the sky seem to change over
several months? Make a plan to find out.
Observation
Thursday
Friday
327
EXPLORE
What are the phases of
the Moon?
Main Idea
On many nights you can see the Moon.
The Moon is a sphere, or ball, of rock. It is
Earth’s closest neighbor in space. The Moon is
a satellite of Earth. A satellite is anything that
revolves around another larger object in space.
The Moon revolves around Earth, much like
Earth revolves around the Sun.
The Moon’s shape and
position in the sky seem
to change.
Vocabulary
phase, p. 328
crater, p. 332
-Glossary
at
www.macmillanmh.com
Reading Skill
Cause and Effect
Technology
Each day the Moon seems to change shape.
Sometimes you can only see a small part of
the Moon. At other times the Moon is a big,
bright circle. Still other times you cannot see
the Moon at all. Each shape of the Moon we
see is called a phase (FAYZ). The photos below
show the eight main phases of the Moon. Have
you seen the Moon in each of these phases?
Moon Phases
Explore Planet Earth with the
Secret Agents.
new
Moon
328
EXPLAIN
crescent
Moon
first-quarter
Moon
gibbous
Moon
Like the Sun, the Moon seems
to rise, move across the sky, and set
each day. This happens because of
Earth’s rotation. As Earth rotates
on its axis, the Moon’s position in
the sky moves from east to west.
The Moon seems to glow in the
night sky. However, the Moon does
not make its own light. The Moon
appears to shine because sunlight
reflects, or bounces, off the Moon.
Quick Check
Cause and Effect Why does
the Moon seem to rise and set
each day?
Critical Thinking How could
Sometimes we can see the
Moon during the daytime.
you predict what the shape of
the Moon will be next week?
full
Moon
gibbous
Moon
last-quarter
Moon
crescent
Moon
329
EXPLAIN
The Moon’s Orbit
sunlight
You see the
last-quarter Moon
about 21 days after
the new Moon.
A new Moon
occurs about
every 29_21 days.
You see the
first-quarter
Moon about
7 days after
the new Moon.
You see the
full Moon about
14 days after the
new Moon.
Read a Diagram
When can you see a full Moon?
The photos show what the
first-quarter Moon, full Moon,
and last-quarter Moon look
like from Earth.
330
EXPLAIN
Clue: Look at the diagram and
read the captions.
Why does the Moon’s
shape seem to change?
The Moon may seem to change
shape, but it is always a sphere.
It only appears to change shape
because you see different amounts
of its lighted side. The Sun shines
on and lights half of the Moon’s
surface. The other half faces away
from the Sun. It is in darkness. As
the Moon revolves around Earth,
different amounts of the Moon’s
lighted half face Earth. The lighted
parts are the phases you see.
When the Moon is between
Earth and the Sun, there is a new
Moon. You cannot see the Moon at
all. The Moon’s lighted side faces
away from Earth. As the Moon
continues to revolve, you see more
and more of the Moon’s lighted
side. When you see the entire
lighted half, there is a full Moon.
As the Moon continues to revolve,
you begin to see less and less of
the lighted side. This cycle happens
about every 291_2 days.
Make a Flip Book
Draw what a Moon phase looks
like on the right side of an index
card. Label the phase. Do this
for each of the eight phases.
Put the cards in order. Staple
them together on the left side.
Flip the pages with your thumb.
How does the Moon’s shape
seem to change?
Quick Check
Cause and Effect What
causes the Moon’s phases
to change?
Critical Thinking What
would the Moon look
like if it did not revolve
around Earth?
331
EXPLAIN
What is it like on the Moon?
Both the Moon and Earth are spheres.
They both rotate. They both revolve. They
both get light from the Sun. They are both
made of rock. In other ways, though, they
are very different.
Earth is about four times larger than
the Moon. Unlike Earth, the Moon has no
atmosphere. It has no liquid water. There
are no living things on the Moon.
Craters of all sizes
are found on the
Moon’s surface.
The Moon’s surface is also different
from Earth’s. Most of its surface is covered
with craters (KRAY•tuhrz). A crater is a
hollow area, or pit, in the ground. Craters
formed on the Moon when chunks of rock
from space crashed into the Moon.
Quick Check
Cause and Effect What caused
craters to form on the Moon?
Critical Thinking Why are there
This is what Earth looks
like from the Moon. 332
EXPLAIN
no living things on the Moon?
The Moon’s temperatures are colder and warmer than Earth’s.
Visual Summary
Think, Talk, and Write
The Moon seems to
change shape each
night. These shapes
are called phases.
Main Idea Why does the Moon
The Moon revolves
around Earth. This
causes the different
phases of the Moon.
Cause and Effect What causes
seem to change shape?
Vocabulary What is a crater?
the Moon to rise and set?
In many ways, the
Moon and Earth
are different.
Critical Thinking Why can you not
see the new Moon phase?
Test Prep How are Earth and the
Make a
Study Guide
Moon similar?
A Both have an atmosphere.
B Both make their own light.
C Both have living things.
D Both are spheres.
Make a Trifold
Book. Use it to
summarize what
you learned
about the Moon
and Earth.
Math Link
Solve a Problem
Objects weigh about six times
more on Earth than they would on
the Moon. If a Moon rock weighs
9 pounds on the Moon, about what
would it weigh on Earth?
Social Studies Link
Do Research
Some astronauts have actually
walked on the Moon. Do research
to find out about one of these
astronauts. Share your findings
with the class.
-Review Summaries and quizzes online at www.macmillanmh.com
333
EVALUATE
Materials
Structured Inquiry
Why does the Moon’s shape
appear to change?
Form a Hypothesis
lamp
The Moon completes one orbit around Earth
about every 29 _21 days. How does the Moon’s
position in space affect how we see the Moon?
When do we see a full Moon? When do we see
a last-quarter Moon? Write a hypothesis.
ball
Step
Test Your Hypothesis
Make a Model Hold the ball and
stretch out your arm in front of you.
Position your arm so that the ball is a
little higher than your head. The ball is
the Moon, and your head is Earth.
Observe Your teacher will turn on a
lamp. The lamp represents the Sun. Turn
your back to the light so that the light
shines on the ball. What part is lit up?
Experiment Turn in place while
holding the ball. Keep the ball in front
of you. Notice the change in light and
shadow on the ball.
Communicate Record your
observations by drawing or describing
what you saw as you turned.
Repeat the experiment several times.
Are your observations the same with
each trial?
334
EXTEND
Draw Conclusions
Observe Where is the ball when it is lit up like
a full Moon? Where is the ball when it looks like
a last-quarter Moon?
Infer Why does the Moon’s shape appear to
change? How do you know?
Guided Inquiry
How does the Moon’s
position change?
Form a Hypothesis
Open Inquiry
What other questions do you have
about the Moon? Talk with your
classmates about questions you have.
How might you find the answers to
your questions?
How does the Moon’s position change
in the night sky over the course of one
month? Write a hypothesis.
Test Your Hypothesis
Design a plan to test your hypothesis.
Remember your plan should test only
one variable—the Moon’s position in
the sky. Decide on the materials you
will need. Then write the steps you
plan to follow.
Remember to
follow the steps of the
scientific process.
Ask a Question
Form a Hypothesis
Draw Conclusions
Did your results support your
hypothesis? Why or why not? Share
your results with your classmates.
Test Your Hypothesis
Draw Conclusions
335
EXTEND
Lesson 3
The Planets
What is that bright point of light near
the Moon in this photo? It is not a star.
It is the planet Venus! What are planets?
How do they move through space?
336
ENGAGE
How do the planets move
through space?
Materials
Purpose
Model how the positions of the planets change.
masking tape
Procedure
Work in a large room or other area. Put a
chair in the center of the room. Tape the card
labeled Sun to the chair. Tape a line from the
chair to a wall.
Form two groups. Each student in the first
group will take a card and line up along the
tape in order: Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, and Neptune.
8 planet cards and
1 Sun card
Step
Make a Model Students in the first group
model how the planets move by walking in a
circle around the Sun. Take steps of the same
size. Count steps together. Stop counting
when you reach the tape again. Students in
the second group repeat steps 2–3.
Use Numbers Do all the “planets”
complete one trip around the Sun in the
same number of steps?
Step
Draw Conclusions
What was different about the orbits?
Infer How do planets move through space?
Explore More
Predict What planets can you see in the night
sky where you live? Make a plan to find out.
337
EXPLORE
What is our solar system?
Main Idea
Earth is one of eight
planets that revolve
around the Sun.
Vocabulary
solar system, p. 338
planet, p. 338
telescope, p. 342
space probe, p. 342
-Glossary
at
www.macmillanmh.com
The Sun, Earth, and the Moon are part of
a larger system called a solar system (SOH•luhr
SIS•tuhm). A solar system is made up of a star
and the objects that move around it.
Earth is one of eight planets (PLAN•its) that
move around the Sun in our solar system. A
planet is a large body of rock or gas with a
nearly round shape that revolves around a star.
Some planets in our solar system are smaller
than Earth. Some are larger. Many have one or
more moons. All rotate. All revolve in a nearly
circular orbit.
It takes Earth about 365 days to complete
one orbit. It takes Mercury only 88 Earth days
to travel its orbit. Neptune takes 165 Earth
years. The farther away a planet is from the
Sun, the longer it takes to complete one orbit.
Reading Skill
Classify
Technology
Explore Planet Earth with the
Secret Agents.
Our Solar System
Venus
Sun
Mercury
Mars
Earth
338
EXPLAIN
Scientists have found over 100 planets that
revolve around other stars.
You can sometimes see
Mercury, Venus, Mars, Jupiter,
or Saturn in the night sky. These
planets look like stars from Earth.
However, like the Moon, planets
do not make their own light.
Planets appear to shine because
sunlight reflects, or bounces, off
them. Although these planets
are larger than the Moon, they
look tiny. The Moon seems large
because it is close to Earth. The
planets are farther away, so they
look much smaller than the Moon.
Sizing Up Planets
Measure Work with a
partner. Hold a marble
about 30 centimeters
away from you.
Measure Have a
partner hold a tennis
ball about 5 meters
away from you.
Observe Which object
seems larger? Why? Which
object really is larger?
Infer How can larger
planets look smaller to
us than smaller planets?
Quick Check
Classify Name an object in our
solar system that is not a planet.
Critical Thinking How would
the Sun look from Mercury?
Read a Diagram
Where is Earth in our solar system?
Clue: Diagrams can show the
positions of things.
Watch the planets
at www.macmillanmh.com
Jupiter
Neptune
Uranus
Saturn
339
EXPLAIN
What are the inner and outer planets?
The four planets closest to the Sun are Mercury,
Venus, Earth, and Mars. They are called the inner
planets. The inner planets are among the smallest
planets in our solar system. They are solid and made
up of rocky material. They are warmer than the other
planets because they are closer to the Sun.
Inner Planets
Mercury is the
planet closest to
the Sun. It is rocky
and full of craters.
Outer Planets
Saturn is known for its
beautiful rings made up
of bits of ice and rock that
revolve around the planet. Jupiter is the largest
planet. It now has two
red spots. The larger
spot, shown here, is
known as the Great
Red Spot.
340
EXPLAIN
The surface of Venus
is covered with thick
clouds that trap
heat. This makes it
the hottest planet.
The planets farthest from the Sun are Jupiter,
Saturn, Uranus, and Neptune. These are the outer
planets. They are called “gas giants,” since they are
largely made up of gases. They may have solid cores,
but scientists do not know yet.
Quick Check
Classify Is Saturn an inner planet or an outer planet?
Critical Thinking If Mercury is closer to the Sun than
Venus, why is Venus hotter than Mercury?
Earth is the only
planet known to
produce oxygen and
to have liquid water
and living things.
Mars, the Red
Planet, has
reddish-brown
soil and polar ice
caps that contain
frozen water.
Uranus is called
the “sideways
planet” because
it rotates on
its side.
Neptune is more than 2 billion
miles from Earth. It has a Great
Dark Spot similar to Jupiter’s
Great Red Spot.
341
EXPLAIN
How can we view the planets?
Are there other planets? What is Neptune
like? We cannot use just our eyes to find
out. Special tools are needed. A telescope
(TEL•uh•skohp) is a tool used to make objects
far away appear closer and larger. A telescope
works by gathering light with mirrors and
lenses (LENZ•uhz). A lens is a clear material
that helps us see objects in more detail.
Another tool used is a space probe. A
space probe is a machine that leaves Earth
and travels through space. Some space probes
land on planets. Others take pictures as they
fly by planets and other objects in space.
In 2006 the space probe New Horizon was
launched. It will travel far beyond Neptune
to find out about other space objects.
Telescopes help
us see planets and
other objects
in space.
Quick Check
Classify What kind of tool is
the New Horizon spacecraft?
Critical Thinking How
could you see the Moon’s
craters better?
342
EXPLAIN
In 2004, two space
probes landed rovers on
Mars. The rovers explored
its surface and sent
pictures back to Earth.
Visual Summary
Our solar system is
made up of the Sun,
the planets, and other
objects that revolve
around the Sun.
Our solar system
has four inner
planets and four
outer planets.
Telescopes and
space probes are
used to observe the
planets and other
objects in space.
Think, Talk, and Write
Main Idea What makes up our
solar system?
Vocabulary What is a planet?
Name five planets.
Classify Is Venus a planet or a star?
Explain your answer.
Critical Thinking What is the
same about all of the planets in
our solar system?
Make a
Study Guide
Test Prep Which tool would BEST
show details of Saturn?
A binoculars
B a microscope
C a hand lens
D a telescope
Make a Trifold
Book. Use it to
summarize what
you learned
about Earth’s
solar system.
Math Link
Solve a Problem
In 2006 Saturn had 28 times as
many known moons as Mars. Mars
had two moons. How many moons
did Saturn have?
Art Link
Planet Picture
Suppose you could visit another
planet. If you could stand on its
surface, what would you see? Draw
or paint a picture. Write the name of
the planet on your picture.
-Review Summaries and quizzes online at www.macmillanmh.com
343
EVALUATE
Inquiry Skill:
Observe
You know that Earth is only one of the planets in our solar
system. How do scientists learn about other planets? How
do they learn about other objects, such as comets, that orbit
the Sun? They observe the Sun, planets, moons, and other
objects in our solar system to learn more about them.
Learn It
When you observe, you use one
or more of your senses to learn about
an object or event. Remember, your
senses are sight, hearing, smell, taste,
and touch. Scientists often use tools,
such as binoculars, microscopes, and
telescopes, to make their observations.
They use their observations to draw
conclusions about objects and events.
Be Careful. It can be dangerous
to observe things by tasting. You should
not taste things in school unless your
teacher tells you it is safe.
Try It
You can observe things, too. Look
at the detail of this comet. Observe
its color and shape. Look for unique
features that help you identify what it
is. What detail helps you know this is a
comet and not a planet?
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EXTEND
Comets are
mostly ice
mixed with
bits of rock
and dust.
Apply It
The photos below show details of planets and other
objects in our solar system. Observe each photo carefully.
Use your observations to identify what each object is.
Which details helped you to identify the objects?
345
EXTEND
Lesson 4
The Stars
The Sun is a star that is close to Earth.
Other stars are in the sky. Why can’t we
see them during the day?
346
ENGAGE
Why do we see stars
at night?
Materials
Purpose
Understand why we do not see stars
in the daytime sky.
white chalk or
white crayon
black paper
white paper
measuring
tape
Procedure
Draw a 3 cm dot with white chalk or
crayon on black paper.
Draw a 3 cm dot with white chalk or
crayon on white paper.
Measure Have your partner hold both
papers 2 m away from you.
Observe Which dot is easier to see?
Step
Draw Conclusions
Infer Why do you think one dot was
easier to see than the other?
Infer Suppose the dots on the papers
were stars. Why do you think you
see stars only at night?
Explore More
Step
Experiment Design an experiment to
show how we sometimes see the Moon
during the day.
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EXPLORE
What are stars?
Main Idea
Stars differ in several
ways. Different stars
are seen during
different seasons.
Vocabulary
constellation, p. 349
-Glossary
at
www.macmillanmh.com
Reading Skill
Summarize
Stars are glowing balls of hot gases that give
off light and heat. The Sun is the only star in
our solar system. It is the closest star to Earth.
There are more stars in the sky than anyone
can easily count. Stars are always in the sky.
We cannot see stars in daytime because the
Sun’s light prevents us from seeing them.
The Sun seems bigger and brighter than
other stars because it is closer to Earth. The
Sun is only a medium-size star, however. It is
much smaller and younger than many other
stars. Other stars seem tiny and faint because
they are so far away.
Size is only one way stars differ. Some stars
are brighter than others. Some are hotter. Blue
stars are hottest. Red stars are coolest.
Sizing Up Stars
medium star
small star
348
EXPLAIN
large star
giant star
Stars are classified by size,
color, and brightness.
Constellations
Long ago, people gazed at the
stars. They thought groups of
stars formed pictures in the night
sky. We can still see those star
groups today. A constellation
(kon•stuh•LAY•shuhn) is a group
of stars that seem to form a picture.
Quick Check
Summarize What are some
ways that stars differ?
Make a Constellation
Find out about a constellation.
Use chalk to draw it on a piece
of black paper. Use a pencil
point to poke holes in the
pattern.
Be Careful.
Observe Trade papers with a
partner. In a darkened room,
hold your partner’s paper out at
arm’s length toward a lamp or
flashlight. What does the star
pattern look like?
Critical Thinking How is the
Sun different from all other stars?
The Big Dipper is shown by the
bright yellow lines. It is part of
the constellation Ursa Major, or
the Great Bear. Communicate Tell your partner
the name of your constellation.
The Big Dipper is not a constellation.
349
EXPLAIN
Why do we see different stars
during different seasons?
Each season, you can see different stars. As Earth
revolves around the Sun, the dark part of Earth faces
different directions. This movement gives us a different
view of the nighttime sky.
Find the constellation Orion below. In winter you
can see Orion in the night sky. In summer Earth has
moved to the other side of the Sun. When you look
at the night sky in summer, you are facing away from
Orion. Orion is in the daytime sky and cannot be seen.
Stars and Seasons
spring
winter
summer
Orion
fall
Read a Diagram
Why can Orion only be
seen in winter?
Quick Check
Summarize Why do we see different
stars from season to season?
Critical Thinking Why might Orion have
looked like a hunter to people long ago?
350
EXPLAIN
Clue: Compare the direction
that the dark part of Earth is
facing in each season.
Visual Summary
Stars differ by size,
brightness, and color.
Think, Talk, and Write
Main Idea What are stars?
Vocabulary What is a constellation?
Summarize Why do stars much
Constellations are
groups of stars
that seem to form
pictures in the
night sky.
larger than the Sun look much smaller
than the Sun from Earth?
Different
constellations are
seen during
different seasons.
Critical Thinking Do you think that
you can see all the stars there are?
Explain your answer.
Make a
Study Guide
Make a Trifold
Book. Use it to
summarize what
you learned
about stars.
Test Prep How would you describe
the Sun?
A a small star
B a medium star
C a giant star
D a blue star
Writing Link
Write a Report
Long ago, people thought the
constellation Cassiopeia looked like
a queen. Research this constellation
or another one. Then write about it.
Music Link
Sing a Star Song
Learn the words to the song
“Twinkle, Twinkle, Little Star.” Write a
verse of your own about stars to go
with the tune. Read or sing the new
words to the class.
-Review Summaries and quizzes online at www.macmillanmh.com
351
EVALUATE
Meet
Orsola
De Marco
Do you ever wonder about the
stars? Orsola De Marco does. She is an
astrophysicist at the American Museum
of Natural History in New York. An
astrophysicist is a scientist who
studies stars. Orsola studies stars that
are found together in pairs. As far as
we know, our Sun is a star that stands
alone. Most stars in the universe have
a partner. They are called binary stars.
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EXTEND
Meet a Scientist
These binary stars orbit each other at
a very close distance. Scientists think
that one star is being absorbed by the
other. The butterfly-shaped “wings”
are probably caused by gases from
the surface of the central star.
Summarize
A good summary
states the main idea
gives the most
important details
is brief
Of course, Orsola cannot go
is told in your own words
to the stars to learn about them.
Instead, she travels to Arizona,
Hawaii, and Chile to use large telescopes.
She gazes billions of miles into space to get a
good look at binary stars. She watches how the
stars affect each other. When a star gets old it
becomes larger. If there is another star nearby,
it might get eaten up, or absorbed, by the old
star. No one is sure what will happen after that.
Orsola is working to find out.
Write About It
Summarize Read the article with a partner. List
the most important information in a chart. Then
use the chart to summarize the article. Remember
to start with a main-idea sentence and to keep
your summary brief.
-Journal Write about it online
at www.macmillanmh.com
353
EXTEND
CHAPTER 8 Review
Visual Summary
Lesson 1 Earth rotates
and revolves around
the Sun. Earth’s
movement causes
day and night and
the seasons.
axis, p. 319
Lesson 2 The
Moon’s shape and
position in the sky
seem to change.
Lesson 3 Earth is
one of eight planets
that revolve around
the Sun.
Lesson 4 Stars
differ in several
ways. Different stars
are seen during
different seasons.
rotates, p. 318
constellation, p. 349 solar system, p. 338
craters, p. 332
space probe, p. 342
orbit, p. 320
star, p. 322
phase, p. 328
telescope, p. 342
1. Earth revolves around the Sun in a
regular path called an
.
2. A line through the center of a
spinning object is an
.
3. A group of stars that seems to
form a picture is called a
.
4. Faraway objects look closer when
seen through a
.
5. A star and the objects that orbit it
make up a
.
6. Every 24 hours Earth
.
7. A machine that travels through
space from Earth is a
.
Make a
Study Guide
Glue your lesson study guides to a
piece of paper as shown. Use your
study guide to review what you
have learned
in this chapter.
354
Fill each blank with the best term
from the list.
8. Each shape of the Moon seen from
Earth is known as a
.
9. The Sun is a _____.
10. The hollow areas and pits on the
Moon’s surface are _____.
-Review Summaries and quizzes online at www.macmillanmh.com
Answer each of the following in
complete sentences.
11. Summarize What do the planets
in our solar system have in
common? How do they differ?
Write several sentences to
summarize this information.
Space Exploration
This photo shows a major event in space
exploration. Make a time line of what you
think were important events in space
exploration.
12. Personal Narrative Look at the
night sky. Write a journal entry
about what you observe in the
night sky. How does what you
observe make you feel?
13. Observe Long ago, we could
only rely on our eyes to learn
about the Moon. What can you
observe about the Moon by just
looking at it? What other details
might you be able to observe
using a telescope?
14. Critical Thinking How might life
on Earth change if Earth were
farther away from the Sun? What
if Earth were much closer?
15. Observe the Moon’s shape below.
How much time must pass before
the New Moon phase occurs?
16. What objects move
through space, and how
do they move?
Draw a line that is 12 inches long.
Mark off each inch to represent five
years. Label each mark with the year.
Mark the very beginning of your time
line with the year 1950. End with the
year 2010.
Research some important events
in space exploration. Mark on your
time line each event and the year
that it occurred.
Which event on your time line do you
think was most important? Why?
Write about it.
1. Why is it warmer in summer than
in winter?
A There is more cloud cover in winter
to block the Sun’s rays.
B The Sun’s rays strike Earth’s surface
more directly in summer.
C The Sun’s rays strike Earth’s surface
more directly in winter.
D Earth is much closer to the Sun in
summer than in winter.
355
Meteorologist
Not all meteorologists work on TV.
Some work as aviation meteorologists.
They predict weather for airlines.
Airline pilots need to know what
weather will be like so people can
travel safely.
Other meteorologists gather data
at weather stations in rain forests or
at the North Pole and South Pole.
The information they gather helps
other scientists learn more about
Earth’s climate.
Meteorologists use technology
to collect data about weather.
To be a meteorologist, you need
to study weather in college. You need
good computer skills. You will also
need to learn to use special weather
tools and how to read radar scans
and satellite photos.
Here are some other Earth
Science careers:
• weather observer
• climatologist
• astronaut
• astronomer
356
This meteorologist checks
rainfall in the Amazon rain
forest of Brazil.
-Careers at www.macmillanmh.com