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Science Stage 5 It’s cosmic! Set 1: Thinking BIG ga voids laxie s st ar s t e m s nets s y Photo credit: NASA s s o l a r pla 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 COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you on behalf of the New South Wales Department of Education and Training (Centre for Learning Innovation) 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 Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 ________________________________________________________________________________________________ Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). © 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