Download It`s cosmic! - NSW Department of Education

Science
Stage 5
It’s cosmic!
Set 1: Thinking BIG
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Photo credit: NASA
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Number: 43012
Title: It’s cosmic
This publication is copyright New South Wales Department of Education and Training (DET), however it may contain
material from other sources which is not owned by DET. We would like to acknowledge the following people and
organisations whose material has been used:
Photograph of a spiral galaxy courtesy NASA
Extract from Science Syllabus Years 7-10 © Board of Studies, NSW 2003
Photograph of the crab nebula © Malin/Pasachoff/Caltech
Photograph of a telescope, courtesy Ric Morante © Upgrade Business Systems Pty Ltd
Photographs of Saturn and Pluto, courtesy of NASA
Photograph of birds on telegraph wires © Thomas Brown
Photograph of a radio telescope © Jane West
Photograph of the Apollo 15 lunar vehicle, courtesy of NASA
Photograph of Voyager in deep space, courtesy of NASA
Covers of Sets 1-4,
Set 3 p 21
Set 1 pp i-iv
Set 1 p 11
Set 1 p 21, Set 3 p 1
Set 2 p 2
Set 2 p 11
Set 3 p 11,
Set 4 p 11
Set 3 p 15
Set 4 p 3
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pursuant to Part VB of the Copyright Act 1968 (the Act).
The material in this communication may be subject to copyright under
the Act. Any further reproduction or communication of this material by
you may be the subject of copyright protection under the Act.
CLI Project Team acknowledgement:
Writers:
Editors:
Illustrators:
Julie Rienstra and David Bray
Rhonda Caddy and Jane West
Tom Brown and Rhonda Caddy
All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith.
Published by
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© State of New South Wales, Department of Education and Training 2005.
i
Set 1: Thinking BIG
What to do
Complete all the activities in this Set 1 booklet.
Then return the booklet to your teacher.
Contents
Lesson 1
What is in the Universe? ......................................... 1
Lesson 2
Stars: the building blocks of galaxies ...................... 5
Lesson 3
The life cycle of a star................................................. 8
Lesson 4
Light from stars......................................................... 13
Lesson 5
Cosmic distances....................................................... 15
Lesson 6
Summary for Set 1.................................................... 20
It’s cosmic!
Set 1
ii
What will you learn in Set 1?
Here are some things that you will have opportunities to do in Set
1. As you complete each lesson, tick each thing you know or can
do to keep track of your own progress.
Lesson 1
❒
identify some parts of the cosmos
Lesson 2
❒
❒
❒
❒
identify objects that are luminous (give out light energy)
state what a star is made of
identify that light is a kind of electromagnetic radiation
spell most words in Lesson 1 and Lesson 2
Lesson 3
❒
❒
complete a summary table about how stars form, change and die
use these scientific words correctly: nebula, protostar, gravity,
supernova, fusion, red giant, black hole and dwarf
Lesson 4
❒
❒
❒
compare the colours and sizes of some stars
show that light can be absorbed
show that light can be reflected
Lesson 5
❒
❒
use the relationship between speed, distance and time
perform mathematical calculations
Lesson 6
❒
make a summary of some main ideas from Set 1.
1
Lesson 1
What is in the Universe?
Have you ever stood and gazed up at the night sky?
Amazing, isn't it!
Everything that exists, including you standing on Earth,
is part of the cosmos.
The cosmos, or Universe, has always fascinated people.
People have tried to explain its structure.
(Its structure is the parts it is made of.)
They have tried to explain how it works.
In this lesson, you will learn about some parts of the cosmos.
It’s cosmic!
Set 1
2
Some parts of the cosmos
Cut out the diagrams on page 3.
Match them with the information below.
Humans live on a planet called Earth.
Earth goes around a star called the Sun.
Other planets and rocks orbit the Sun too.
These make up the Solar System.
Our Sun is in the galaxy called the Milky Way.
A galaxy is a group of billions of stars.
There are billions of galaxies in the Universe.
Other galaxies look very small because
they are so far away. The huge empty spaces
between galaxies are called voids.
It’s cosmic!
Set 1
3
Cut apart the boxes below. Use them to complete page 2.
Pluto
Earth
Sun
Venus
Saturn
n
Su
Jupiter
Mars
Mercury
Neptune
Uranus
It’s cosmic!
Set 1
Sun
4
It’s cosmic!
Set 1
5
Lesson 2
Stars: the building blocks of galaxies
What do you see when you look out into the night sky?
If the night is dark and cloudless, you will see twinkling stars
everywhere. But some of the ‘stars’ you see are really huge groups
of stars called galaxies.
What are galaxies?
The stars in the Universe are grouped together into galaxies.
Galaxies are the largest objects in the Universe.
Each galaxy is a very large spinning structure. It contains billions
of stars. It also contains clouds of gas and dust called nebulas.
Some of the stars, like our Sun, have planets. All these things are
held together in each galaxy by gravitational forces.
(You feel a gravitational force on Earth. It is called gravity.)
What are stars?
Stars are objects in space that are able to give out their own energy.
The energy comes from nuclear reactions occurring inside each
star.
You can see stars because they are luminous. Luminous means
that an object gives out energy as light.
Circle the objects below that are luminous.
It’s cosmic!
Set 1
6
Here is a simple diagram of our Sun.
This diagram shows the structure of our star.
corona
a halo or crown
of gases
photosphere
the bright region
of the Sun that
you see
core of
intensely hot
hydrogen and
helium gas
There are also small amounts
of other elements such as
iron, calcium and sodium.
What is the core of a star made of? _________________________________
What is the name of the halo of gases? _____________________________
What is the name of the bright part of the Sun that we see? __________
Stars give out light. They also give out other forms of energy.
These forms of energy are called electromagnetic radiation.
Look at the next diagram of the different kinds of electromagnetic
radiation.
Shade over the part that shows light you can see (visible light).
ENERGY INCREASES
radio
TV
light
microwaves
infrared
visible
radio waves
X-rays
ultraviolet
Can you use your eyes to see all the energy that comes from stars?
No! There are lots of other kinds of energy that you cannot see.
(They are the parts of the diagram that you did not shade.)
It’s cosmic!
Set 1
gamma rays
7
Astronomers study all the kinds of electromagnetic radiation to learn
about stars. (Astronomers are scientists who study the cosmos.)
Check your spelling
Can you spell most of the words you have read? Try these words.
Copy the word.
Look at the word and
say it. Then cover it
and write it again.
cosmos
Universe
Earth
Milky Way
galaxy
nebula
gravity
nuclear
astronomer
millions
It’s cosmic!
Set 1
Check your spelling.
Tick it if it is right
or copy it correctly.
8
Lesson 3
The life cycle of a star
A star is very much like a person going through life stages. Stars, like
people, change as they age. But stars age over millions of years, so it is very
difficult for you to notice any changes when you look up at the night sky.
Stage
1.
birth
(protostar)
2.
childhood
(heats up)
3.
adolescence
to maturity
(nuclear
fusion)
4.
middle age
(red giant)
5.
old age
(white
dwarf)
6.
death (black
dwarf)
Description
It’s cosmic!
Set 1
9
Cut out the descriptions of the stages of a star’s life below and use
them to complete the table on the previous page. This is the life
cycle of an average-sized star such as our Sun.
A star spends most of its life shining
steadily without changing. Our Sun is at
this stage. Eventually, the fuel begins to
run out and the star expands to become a
red giant.
A star becomes unstable as it gets older.
Then it collapses to form a very hot small
star called a white dwarf.
The star heats up as it increases in size.
How long a star lives and how it dies
depends on its mass. An average-sized star
cools to be a dead star called a black dwarf.
Stars begin to form in nebulas (big clouds of
hydrogen and dust). A cool newborn
(newly formed) star is called a protostar.
When the star becomes hot enough,
nuclear fusion begins. This means
hydrogen atoms join, making helium
atoms and releasing enormous amounts of
heat and light.
It’s cosmic!
Set 1
10
˚
It’s cosmic!
Set 1
11
How do stars die?
You have just completed a life cycle that shows how an averagesized star dies. It slowly fades away and becomes a black dwarf.
Large stars, that have much more mass than our Sun, die in a
very spectacular way. They blow apart in a gigantic explosion.
The explosion forms a supernova. A supernova can shine as
brightly as a whole galaxy of stars.
Photograph by David Malin
© Malin/Pasachoff/Caltech
Here is a supernova that was discovered in a nearby galaxy.
It was photographed in 1987. It was so bright that people did not
need a telescope to see it.
Some supernovas change into neutron stars. (Some neutron stars
are called pulsars because they give out radio waves.)
Other supernovas change into black holes. (Black holes have
so much gravitational force that nothing—not even light—can
escape from them.) Black holes are the most mysterious objects
in the Universe.
It’s cosmic!
Set 1
12
All those new words!
Match each word with a clue. Then circle the words in the puzzle.
Words
Puzzle
gravity
S
R
A
T
S
O
T
O
R
P
red giant
B
U
N
O
R
T
U
E
N
E
protostar
L
T
P
H
G
D
L
D
E
T
supernova
A N
K
E
C
S
W
L
B
G
fusion
C
A
O
F
R
A
S
L
U
P
nebula
K
I
F
I
R
G
P
G
L
O
black hole
H
G
C
F
S
O
I
S
A
D
dwarf
O
D
E
N
L
U
A
A
L
U
L
E
M
U
O
D
F
I
N
S
E
R
Y
T
I
V
A
R
G
T
S
A
V
O
N
R
E
P
U
S
Clues
1.
A cloud of dust and gas in space
2. A star just ‘born’
3.
The name for gravitational force near Earth
4.
This word describes a special kind of star explosion
5.
A word that describes how stars produce energy
6.
Our Sun will become one of these
7.
Nothing escapes this
8.
The final size of our Sun when it 'dies'
There is another word you need to know too. It is supergiant.
A supergiant is a really huge star. (Can you find it in the puzzle?)
It’s cosmic!
Set 1
13
Lesson 4
Light from stars
You’ve learned that stars can be different sizes.
They can also give out different colours of light.
Here are some examples.
Betelgeuse (say beetlejuice) is a red supergiant.
Shade it orangy red.
Rigel is a blue giant.
Shade it light blue.
Our Sun is an average-sized star.
Shade it yellow.
Betelgeuse
Leave the white dwarf star white.
Rigel
our Sun
Betelgeuse is too large
to fit onto the drawing
on this page.
a white dwarf
Rigel
It’s cosmic!
Set 1
14
Our Sun is really rather small but it looks bright because it is close to
us. The light from stars travels out through the Universe.
It travels as waves since light is a kind of electromagnetic energy.
What happens to the light?
Some light is absorbed
Objects can absorb light, or soak it up. Have you ever sat in the
sunshine in a black jumper or black pants? Try it for a few
minutes—you can even call it school work! What happens?
Did you feel warmer after a few minutes in the sunshine?
The black material absorbed light and heat energy.
Black is a good absorber of light and heat energy.
Objects in space can soak up light energy. Black objects absorb
all colours of light. (Coloured objects absorb all colours of light
except their own colour.)
Some light is reflected
Reflect means to bounce back.
Light reflects off shiny surfaces, such as water, glass and mirrors.
Light bounces back from other objects too. For example, go into
the sunshine and look at a white object. See how bright it looks
compared with other darker objects. What do you notice?
Did the white object look very bright and glary? White reflects lots
of light.
All the objects you can see
reflect some light.
light energy from
a luminous source
If light bouncing off the object does
not reach your eyes, you cannot see
the object at all!
Objects in space such as planets and
moons reflect light from stars.
It’s cosmic!
reflected light
travels from the object
to your eyes
Set 1
15
Lesson 5
Cosmic distances
Are you beginning to get an idea of how big the Universe is?
Objects, their masses and the distances between them can be huge!
Units for measuring distances in space
On Earth, distances are measured in metres (m).
A metre is about from the tip of your nose to your fingertips.
Longer distances are measured in kilometres (km).
1 kilometre = 1 000 metres
Why do we need special units to measure distances in space?
The Moon is the object closest to Earth. It is 240 000 km away.
Some other objects are billions of billions of kilometres away.
So, it is useless to try to measure most distances in the cosmos
using kilometres.
What units do astronomers use to measure distances?
Astronomers use four different units. They are:
•
kilometres (km)
This unit is used for very small distances, such as the distance
between Earth and the Moon.
•
astronomical units (AU)
This unit is used for small distances, such as distances within
our Solar System.
•
light years (ly)
This unit is used for larger distances, such as the distances
between stars.
•
megaparsecs (Mpc)
This unit is used for very large distances, such as the distances
between galaxies.
In this lesson, you are going to learn more about light years and
astronomical units.
It’s cosmic!
Set 1
16
Light years
A light year (ly) is the distance that light travels in one year.
A light year is a very long distance because light travels at the
speed of 300 000 kilometres per second (300 000 km/s).
How far does light travel in one second? _______________________
How far does light travel in two seconds?
______________________
How far does light travel in one year?
Use a calculator to do the following calculation.
1.
Multiply 300 000 (which is the speed of light in seconds) by 60
to find out how far light has travelled in one minute.
2.
Then multiply your answer from Step 1 by 60
to find out how far light has travelled in one hour.
3.
Then multiply your answer from Step 2 by 24
to find the distance travelled in one day.
4.
Then multiply your answer from Step 3 by 365.25
to calculate how far light has travelled in one year.
5.
What is your answer? _____________________________________
Travelling to Alpha Centauri
After the Sun, Alpha Centauri is the closest star you can see from
Earth.
This might make you think that Alpha Centauri is fairly close to
Earth. How far away is it really?
Alpha Centauri is 4.3 ly away from Earth. That’s 40 000 000 000 000 km,
or 40 trillion kilometres. Too big a distance to begin to imagine!
And if you think that is a long way, think about the distance to some
other stars.
•
Betelgeuse is another star in our galaxy (the Milky Way).
It is 518 ly away.
•
The closest galaxy you can see is 160 000 ly away.
•
One of the furthest galaxies from Earth is called Sombrero
(because it looks like a hat). It is 41 million ly away.
It’s cosmic!
Set 1
17
How long would it take to go to Alpha Centauri if you could get
there by foot, car, jet and space shuttle?
Using lines, match up the way to travel with the correct speed
and with the correct time taken.
Way to travel
Speed of space travel
Time taken
by foot
900 km/hr
5 000 000 years
by car
6 km/hr
160 000 years
by jet
28 000 km/hr
45 000 000 years
100 km/hr
750 000 000 years
by space shuttle
Do you think it is likely that humans will travel to Alpha
Centauri in the next 100 years? Why or why not?
Astronomical units
An astronomical unit (AU) is the average distance from Earth
to the Sun. It is equal to 150 million (150 000 000) kilometres.
How long does it take for light to travel one astronomical unit?
Remember, speed is a measure of how quickly something moves.
To find a speed, you need to know the distance from one place to
another and the time taken for the trip.
Speed can be written using a mathematical formula:
speed =
This means speed equals distance divided by time.
The same formula can be rearranged like this:
distance
time =
speed
This means time equals distance divided by speed.
It’s cosmic!
Set 1
18
1.
Using this formula, calculate the time it takes for light
to travel 150 000 000 km from the Sun to Earth.
Remember that light has a speed of 300 000 km/s.
time = distance
speed
=
____________________________
=
2.
Your answer is a time measured in seconds.
What is this time in minutes?
3.
Why do you think the AU is used for distances within the
Solar System only, and not for distances in the Universe?
Comparing light years and astronomical units
Here is an activity to help you to picture the difference between
light years (ly) and astronomical units (AU).
For this activity, you will need:
•
a piece of chalk.
What to do:
1.
Mark a point on the ground about one millimetre in size.
This represents one AU, the distance Earth is from the Sun.
Not very big is it?
2.
Take 63 steps away, making each step about 1 metre in size.
This new distance represents the size of one light year.
It’s cosmic!
Set 1
19
Looking back in time
Now here is something to make you wonder!
When you look at a star, you are seeing light that has travelled
all the way from the star to your eyes. Light travels quickly but
stars are so far away that it takes a long time for the light to arrive.
For example, Rigel is 900 ly away. When you look at Rigel, you are
seeing light that left the star 900 years ago. You are seeing Rigel
as it looked 900 years ago. You are looking back in time.
© Ric Morante
So if Rigel explodes tonight, you won’t see it. You would have to
wait 900 years before light from its supernova reaches Earth.
(Sorry, if it explodes today, you won't be on Earth to see it!)
When astronomers look at galaxies that are millions of light years away,
they are looking back in time to when the Universe was forming.
These galaxies may not exist today but we can see them because their
light still reaches us from millions of years ago.
It’s cosmic!
Set 1
20
Lesson 6
Summary for Set 1
Complete the sentences below to make a summary.
Here are the words you need. Use each word once.
absorb
cosmos
holes
reflect
big
electromagnetic
kilometre
stars
black
energy
life
Universe
colours
galaxy
quickly
year
•
The cosmos is another name for the
•
The
•
Galaxies are the largest structures in the cosmos.
contains billions of stars.
Each
.
has existed for a very long time.
are made of hydrogen and helium.
•
•
during nuclear
Stars make their own light
fusion.
Light travels away from stars as energy waves. Light is a kind of
radiation.
•
You can see a star when light energy reaches your eyes.
Some objects absorb (soak up) light.
all light that reaches them.
Black objects
•
Most objects reflect (bounce back) some light that reaches them.
light
You can only see objects when they
into your eyes.
•
. It still takes a long time
Light travels very
for light from stars to reach Earth because the stars are so far
away.
speed =
It’s cosmic!
Set 1
21
•
Stars have a
cycle. They may go through stages
such as protostar, mature star, red giant and white dwarf. Some
stars fade away to be
dwarfs.
Others explode as supernovas and become neutron stars or
black
. The way stars die depends on their
mass.
•
Different stars give out different
Stars can be different sizes.
•
(ly) is much further than
A light
an astronomical unit (AU). An astronomical unit is much
further than a
(km).
•
The Universe is very
of light.
!
It’s cosmic!
Set 1