chapter 13 the universe and its stars page 412

NEL602 Unit D: Space Exploration

CHAPTER

13 The Universe and Its Stars Page 412

Key Ideas Vocabulary

Technology has advanced our understandingof the universe.

Nuclear fusion powers stars and is the forcebehind solar flares, prominences, sunspots,and the solar wind.

A star’s mass determines the stages of its lifecycle.

Galaxies, star clusters, and nebulas can bedistinguished by their structures andcharacteristics.

expanding universered shiftBig Bang theorylight yearparallaxbaselinestandard candlesabsolute magnitudeapparent magnitudenuclear fusioncoreradiative zone

convective zonephotospherechromospherecoronasunspotssolar prominencessolar flaressolar windmain sequencesolar massred giant white dwarf

neutron starpulsar black holeelliptical galaxiesspiral galaxiesbarred spiral galaxiesirregular galaxiesquasarsglobular clustersopen clustersdark matterdark energy

Science Skills and Processes Intro 13.1 13A 13.2 13B 13.3 13C 13.4 13.5 13D 13.6

Inquiry Skills

Questioning

Hypothesizing

Predicting ✓ ✓ ✓ ✓ ✓

Planning

Conducting ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

Recording ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

Analyzing ✓ ✓ ✓ ✓ ✓ ✓ ✓

Evaluating ✓ ✓ ✓ ✓ ✓ ✓ ✓

Communicating ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

Synthesizing ✓ ✓

Additional Inquiry Skills (Try This Activity)

Creating Models ✓ ✓

Observing ✓

Estimating ✓

Measuring ✓

Interpreting Data ✓

TEACHING NOTES

• Possible Misconceptions– Identify: Students may think that all the objects in the night sky are

stars. – Clarify: Using our Milky Way as the example, explain that our

galaxy consists of over 200 billion stars. As distances increase, thestars appear smaller. At the enormous distances between bodies inspace, even the close galaxies appear as points of light to theunassisted eye (e.g., the Andromeda Galaxy at 2.9 light years isbarely a smudge).

– Ask What They Think Now: Ask students, What do you estimate to bethe number of stars in the universe, now that you understand that notevery object giving off light in the night sky is a star? (Students’estimated values should be significantly higher than 200 billion.)

• Have students look at the chapter opener photo on Student Bookpage 412. Ask, Is this a picture of our galaxy? A correct responsewould be no. This is actually the Pinwheel galaxy (M101), foundjust above the last two stars in the handle of the Big Dipper.

• Have students read the chapter preview and give possible answers forthe questions in the preview. Background information to provide tostudents about the preview and the photo includes: – The Milky Way is big to really big. The Milky Way holds

200 billion stars and is 100 000 light years across.– There are other galaxies like ours: M101, for instance.– Other galaxies are scattered throughout deep space, beyond the

unaided eye’s ability to see.– Some galaxies such as the small and large Magellanic Clouds are

close at 0.2 light years. The Pinwheel Galaxy is 2.2 light yearsaway, and Andromeda is 2.4 light years away. Other galaxies havebeen found as deep into space as we can see (about 13 billion lightyears) with the Hubble Space Telescope.

– Galaxies all arose from the gathering of matter just after the Big Bang.

– Stars produce heat and light from the thermonuclear reactions intheir core.

– All stars are related based on their mass. A star’s mass determineswhat type of a star it is and what it will become.

• Have students who need additional support with reading use thescaffolding masters provided for each section.

• As you progress through the chapter, prompt students to make studynotes in the Chapter 13 Study Guide Outline found in the StudentWorkbook.

• Hand out BLM 0.0-10 Chapter Key Ideas. Inform students that thiswill be a place to record key vocabulary and personal experiences.

Chapter 13 The Universe and Its Stars 603NEL

Related Resources

Dickinson, Terence. TheUniverse and Beyond.4th ed. Richmond Hill,ON: Firefly Books, 2004.

Garlick, Mark A. TheIllustrated Atlas of theUniverse. Sydney,Australia: Weldon OwenInc., 2006.

Kerrod, Robin. Hubble: TheMirror on the Universe.Richmond Hill, ON: FireflyBooks, 2005.

Moore, Patrick (Sir). FireflyAtlas of the Universe.3rd ed. Buffalo, NY:Firefly Books, 2005.

B.C. Science Probe 9ComputerizedAssessment Bank

B.C. Science Probe 9Create and Present:Modifiable Presentationsand Illustrations CD

Thomson Gale ScienceResource Center

Nelson Science Probe 9websitewww.science.nelson.com

• You can use any or all of the following BLMs to help students studythe vocabulary in this chapter:– BLM 0.0-11 Science Idea Box– BLM 0.0-12 Vocabulary Wheel– BLM 0.0-13 Term Box

• Additional information is available on the Nelson Science websitewherever a Go icon appears in the Student Book.

• To assess students, you may want to use or adapt Rubric 13: Chapter 13.

• Assign students the Try This: Structure in the Milky Way activity.


TRY THIS: STRUCTURE IN THE MILKY WAY

Purpose

• Learn that galaxies have complex shapes.

Notes

• Depending on the time of year, you may need to use images of the Milky Wayto do this Try This activity. Use BLM 13.0-1 Milky Way Galaxy.

Suggested Answers

A. When the 15 cm circle is labelled in this manner and held over the student’shead, it is correctly aligned with the points of the compass, and the imagedrawn will be in the correct perspective.

B. The Milky Way is not a simple band of stars. The shape changes as the armssplit.

Technology Connections

Have students access theHubble Space Telescopewebsite and look for moreinformation on the galaxydesignated M101 andshown on page 412.

ESL/Extra Support

• Direct students to read the chapter opener with the help of anEnglish-competent partner. Ask them to answer the question, Whatare galaxies made of? Then ask them to share what they already knowabout galaxies and stars.

• Have students begin or add to a visual dictionary in which a definitionis augmented by their own diagrams that help to explain the term.Include the words galaxy and star.

Extra Challenge

• Have students use the Internet and other sources to locate pictures andinformation on the name, size, shape, and location of selected galaxies.Encourage students to present their findings in poster format, usingtext boxes to provide information about their selected graphics.

Meeting Individual Needs

The Origin of the Universe 14


PRESCRIBED LEARNING OUTCOMES• explain how a variety of technologies have advanced understanding of

the universe and solar system• describe the major components and characteristics of the universe and

solar system• represent and interpret information in graphic form• demonstrate scientific literacy• describe the relationship between scientific principles and technology

KNOWLEDGE• technologies advance understanding of the solar system, stars, and

universe• components of the universe and solar system

SKILLS AND ATTITUDES• illustrate astronomical phenomena• communicate results• use bar graphs, line graphs, pie charts, tables, and diagrams to extract

and convey information• acquire and apply scientific and technological knowledge to the benefit

of self, society, and the environment

ICT OUTCOMES• demonstrate the ability to use the Internet to access, capture, and store

information • apply the principles of effective communication and good design when

using information technology tools

13.1

Time

30–45 min

Key Ideas

Technology has advancedour understanding of theuniverse.

Vocabulary

• expanding universe• red shift• Big Bang theory

Skills and Processes

ConductingRecordingAnalyzingEvaluatingCommunicating

Lesson Materials

per group• large balloon• water-soluble marker

Program Resources

BLM 13.1-1 Visible Spectrumand Red Shift

SM 13.1 The Origin of theUniverse


Red Shift• The earliest work on receding

galaxies was done by Vesto Slipher(1875–1969) at the LowellObservatory. Slipher used thespectral fingerprints of the galaxylight to determine that the lines werealways in the same locations relativeto each other. If the lines wereshifted to the red, or longer,wavelengths, then the light sourcewas moving away from us. A blueshift meant the light was comingtoward us. The comparison to a carhorn that comes closer and movesaway is a good analogy. As thevehicle approaches, the pitch of thehorn is quite high. As the vehiclepasses, the pitch drops to a lower

value. This occurs because thesound waves are stretched fartherapart, and sound with a longerwavelength has a lower pitch (orfrequency) than sound with a shorterwavelength. As in the car hornanalogy, the wavelengths arecompressed into the blue end of thespectrum as the light approachesand stretch into the red end as itrecedes.

The Big Bang• The expansion of the universe

suggests that objects in the universewere once much closer togetherthan they are today. This is the basisfor the idea known as the “BigBang,” that the universe began

SCIENCE BACKGROUND


TEACHING NOTES

Getting Started

• Teacher Demo: The Doppler ShiftAttach a small electronic buzzer to a string. With the buzzer on,swing the string in a circle as slowly as possible. Students will hearthe buzzer change in pitch. Ask if they can determine when the pitchchanges and in what way it changes. They should be able to noticethat the pitch increases as it swings toward them and decreases as itmoves away. This demonstrates the Doppler Shift, upon which thered shift–blue shift of light is also based.

• Possible Misconceptions– Identify: The light reaching us from any source near or far does so

at the same time.– Clarify: At a velocity of 300 000 km/s, light is fast, but even the

distance to the Sun is so great that it takes light 8 min to reachEarth. The light from the stars and galaxies takes even longerbecause they are so far away. Thus, the light we see left that star orgalaxy a very long time ago.

– Ask What They Think Now: Ask, The most distant galaxy found so faris 13.2 billion light years away. When did light leave that galaxy?(Student answers should indicate that light left 13.2 billion yearsago.)

• With this explanation or realization that the light we see today leftthat galaxy 13.2 billion years ago should come the understandingthat not all light we see began its journey at the same time. Further,this is a lead into the idea that looking out into space is like lookingback in time.

1

13.7 billion years ago as anexpansion from a condition of highdensity and temperature. The BigBang was not an explosion, blowingpieces into the surrounding space.Rather, it was the start of anexpansion of space itself. An initialtiny volume of extremely densematerial contained all of the matterand energy in the entire universe.Since the Big Bang, the size of theuniverse has increased.

Cosmic Microwave Background(CMB) Radiation• CMB was discovered in 1964 when

Arno Penzias and Robert Wilsondetected a background noise in theirradio telescope. They determinedthe noise was from outside our

galaxy, and it came from alldirections with equal intensity. The“noise” coming from every part ofthe universe was actually microwaveradiation at a temperature of 2.725 °C above absolute zero. Thesecharacteristics corresponded to thetheories that said this should be thetemperature and type of wavelengthenergy left after the big bang.

• Later use of the Cosmic BackgroundExplorer (COBE 1992) and WilkinsonMicrowave Anisotropy Probe(WMAP 2003) discovered non-homogeneous areas or“anisotropies” in the CMB. Theseareas of slightly higher temperaturesand densities are likely the seedsaround which galaxy formationbegan.

Related Resources

Dickinson, Terence. TheUniverse and Beyond. 4th ed. Richmond Hill,ON: Firefly Books, 2004.


Giancoli, Douglas C.Physics: Principles withApplications. 6th ed.Upper Saddle River, NJ:Pearson Education Inc.,2005.


Moore, Patrick (Sir). FireflyAtlas of the Universe. 3rd ed. Buffalo, NY:Firefly Books, 2005.

Understanding theUniverse: What’s New inAstronomy (VHS)

Understanding theUniverse: An Introductionto Astronomy (VHS)

Stephen Hawking’sUniverse (VHS)





CSA EducatorsResources: Astronomy

– Formation of theUniverse (in Module 6)

NOVA videos– Discovering the Big

Bang– Riddle of the Big Bang

Quirks and Quarks audioclip

– The Big Bang

Guide the Learning

• Use the Reading and Thinking Strategy of making comparisonsand paraphrasing when reading this section.

• Ask students to examine Figure 2 on Student Book page 414 anddetermine the connection between wavelength and frequency asnoted in the figure. They should note that as the wavelengthshortens, the frequency, or energy, increases. Thus, violet light hasthe shortest wavelength and the greatest energy. This could even beextended to explain why ultraviolet light with its higher energy levelcan be so damaging.

• Use BLM 13.1-1 Visible Spectrum and Red Shift to demonstrate howa moving light source can compress the light waves in front of it andstretch out the light waves behind it.

• To provide a physical example of Figures 3 and 4 in the StudentBook, use a ripple tank and ask the physics teacher in your school tohelp set it up. Alternately, make or obtain a series of concentrichoops (e.g., embroidery rings) of different sizes. Equally spaced, theyrepresent Figure 3. Using your finger as the “boat,” start from thecentre and move your finger in one direction until you are draggingall the hoops. This now simulates Figure 4.

• To help demonstrate why we would expect to find remnant radiationfrom the Big Bang in every direction in space, have students do thefollowing demonstration. Place one student in the centre of theroom to act as Earth, and surround that person with a shoulder-to-shoulder ring of students. These students should be about 1 m awayand facing outward from the centre. Ask the ring of students to take2 to 5 steps, or whatever your classroom will allow, in the directionthey are facing. Ask the student in the centre to rotate one turn andobserve that this “ring” is visible in every direction. To demonstrateclumping of matter in the early universe, give two adjoining studentsa short piece of string and have them stay that close together as theywalk away. The two “joined” students represent clumping of matter.

• Have students perform Try This: The Ballooning Universe.

2


TRY THIS: THE BALLOONING UNIVERSE

Purpose

• Use a simple model to illustrate the concept of an expanding universe.

Notes

• The expanding balloon model is rather simple and limited because it treatsgalaxies as dots on the surface of the balloon. In reality, galaxies are spreadthroughout the universe, but that cannot be shown inside a balloon.

• As the balloon expands, so does the distance between the dots.• The dots also expand, which is an error in the model.

Suggested Answers

A. The distances between the dots increase by the same amount.

B. Astronomers see galaxies moving away from us.

Math Connections

Relate the concept ofdifferent colours todifferent wavelengths oflight. Have students graphwavelength againstfrequency of visible lightto see the inverserelationship. Use the datain Figure 2 on page 414 ofthe Student Book.

Consolidate and Extend

• Ask students, Why did the red-shift phenomenon allow Hubble todevelop the expanding universe concept? Answers should relate the ideathat the greater the red shift, the farther away the light source.

• The Sun’s light reaches us 8 min after it leaves the Sun. That makesthe Sun eight light minutes away. The Andromeda Galaxy is 2.4 million light years away. Ask, How long ago did the light we seetoday leave Andromeda? (The answer will be 2.4 million years ago.)

• Inform students that cosmic microwave background (CMB)radiation is the remnant of the Big Bang and it displays regions ofdifferent densities and temperatures thought to be the “seeds” offuture galaxies.

• Assign students the Check Your Understanding questions.

3


C. The distance between the dots is reduced.

D. The deflated balloon represents a point when all the galaxies are much closertogether. This can either be just after the Big Bang or at a point late in thecollapse of the universe, which, according to recent discoveries, is not likely tooccur.

E. If the process of collapse could continue, the dots on the balloon would allcompress together.

F. The surface of the balloon represents space.

G. The model represents the galaxies moving away from each other as spaceexpands. The model shows galaxies only on the surface of the balloon, notthose inside the balloon. Galaxies are not on the boundary of the expandinguniverse, as they are on the balloon, and the model cannot collapse completely.

CHECK YOUR UNDERSTANDING—SUGGESTED ANSWERS

1. A wavelength is the distance between two neighbouring peaks or crests.

2. The colours of the visible spectrum are red, orange, yellow, green, blue, andviolet.

3. (a) Red has a wavelength range of 7.0 � 10–7 to 6.5 � 10–7 m.

Violet has a wavelength range of 4.5 � 10–7 to 4.0 � 10–7 m.

(b) Violet has the greater energy.

(c) Student diagrams need to show red with a lower frequency (longer wavelength) than violet.

crest crest

� � wavelength

1 �

Art Connections

Ask students to createtheir own colouredspectrum withwavelengths andfrequencies, and relate itto the variety of coloursavailable in art supplies.


4.

5. A spectroscope diffracts, or splits, and spreads light into a spectrum.

6. From a spectrograph, astronomers can learn the composition of a light sourceand the direction and speed at which the light source is moving.

7. Red-shift diagrams should look like Figure 6(a) and (b) on page 415 of theStudent Book, with a set of spectral lines now nearer to or in the red end ofthe spectrum.

8. As the object moves away, the wavelengths of light appear to be longer andare shifted to the red end of the spectrum.

9. The red shift has occurred because the galaxy is moving away from us.

10. (a) Time zero is the moment of the Big Bang.

(b) Time zero was 13.7 billion years ago.

11. Since the Big Bang, all the matter and energy in the universe have beenspreading outward. With space all around us, as we look outward in anydirection, we should detect the outer boundary of the Big Bang. The outerboundary of the universe is the remnants of the expansion front of the BigBang. We are on the inside of a sphere looking outward.

12. The red shift of the Big Bang’s background radiation helps determine itstemperature and its age.

13. Looking out in space is like looking back in time because the farther away anobject is, the longer light takes to reach us. Light takes about 8 min to reachus from the Sun; light left some distant stars a few years ago, or somegalaxies several billions of years ago.

14. COBE and WMAP data illustrated an uneven distribution of matter in the earlyuniverse, which showed the beginnings of all the galaxies and stars.

15. The current temperature of the background radiation is –273 °C.

16. Every scientific theory is open to refinement as new discoveries are made. It is a strength of science that changing knowledge leads to better theories.

shorterlonger

direction of motionTechnology Connections

Have students use theInternet and other sourcesto find the distance fromEarth to several suns andstars. Next, have studentsuse a computerspreadsheet/graphingprogram to calculate anddisplay how long it takeslight from their selectedstars and suns to reachEarth. To reinforce theconcept that when youlook at the lights in thesky you are looking at thepast, students couldresearch and discuss whatwas happening on Earthwhen the original light leftits source.

Make Comparisons/Paraphrase

• Read the section heading and the first two paragraphs on StudentBook page 414 with students.

• Suggest to students that one strategy they can use to help them learnsomething new is to compare the new information to somethingfamiliar. Tell them they will be learning about Hubble’s expandinguniverse theory by comparing it to a toy boat floating in a still pond.

• Arrange students in pairs to read the third paragraph and Figure 3 onpage 414 and the first paragraph and Figure 4 on page 415. Havethem take turns explaining to one another how Hubble used thephenomenon of light energy travelling as a wave as evidence for theexpanding universe. Encourage students who are listening to askquestions if the explanations are not clear. Then direct students toreverse roles.

Reading and

Thinking Strategies


What To Look For in Student Work

Evidence that students can• identify and describe a range of instruments that are used in astronomy

(e.g., spectroscopes, diffraction gratings, COBE, WMAP)• give examples of how astronomers use astronomical and space exploration technologies to

advance understanding of the universe and solar system (e.g., using red shift to support theidea of an expanding universe)

• describe the formation of the universe (the Big Bang)• extract information from diagrams• describe the qualities of the scientifically literate person, such as recognizing that scientific

knowledge is continually developing and often builds upon previous theories• identify the main points in a science-related illustration• identify a variety of technologies and explain how they have advanced our understanding of

science (e.g., spectroscope and red shift)

ASSESSMENT FOR LEARNING

ESL

• Have students add to their visual dictionary. Use the boldfacedvocabulary words and others such as spectrum, wavelength, galaxy,absolute zero, and scientific method.

Extra Support

• Have students build two models, one for each example in Figures 3and 4. Build the models from cardboard or paper circles of increasingradii: 2, 4, 6, and 8 cm. In Figure 3, the circles are concentric becausethe wave source is stationary. In Figure 4, the circles are elongated intoovals to represent the motion of the source. The resulting changes inwavelengths will be obvious when the centres of the circles are spreadout along a straight line.

• For students who need additional support with the reading in thissection, use SM 13.1 The Origin of the Universe.

Extra Challenge

• The scientific name for the cause of red shift is the Doppler Effect.Ask students to research this effect and relate it to what they havelearned about red shift. Although the Doppler Effect relates to alltypes of waves, including sound waves, focus on light waves only.


Investigation: Bright Line Spectra Page 446




solar system• demonstrate safe procedures• perform experiments using the scientific method• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour• describe the relationship between scientific principles and technology• demonstrate competence in the use of technologies specific to

investigative procedures and research


universe• elements of a valid experiment• appropriate scale• application of scientific principles in the development of technologies

SKILLS AND ATTITUDES• illustrate astronomical phenomena• recognize dangers• use personal protective equipment• make accurate measurements using a variety of instruments• communicate results• use bar graphs, line graphs, pie charts, tables, and diagrams to extract

and convey information



using information technology tools • analyze the impact of multimedia documents on intended audiences

13A

Time

45–60 min

Key Ideas



PredictingConductingRecordingAnalyzingEvaluatingSynthesizingCommunicating

Lesson Materials

per group• spectroscope• assorted light sources

(candles, light bulbs, heatlamp, bug light)

• coloured pencils• gas discharge tubes

Program Resources

Investigation BLM 13A BrightLine Spectra

Rubric 18: Conduct anInvestigation

Rubric 19: Conduct anInvestigation—Self-Assessment

WS 13A Bright Line SpectraRecording Chart

SSP Rubrics 5, 6, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 21, 22


Spectroscopes and DiffractionGratings• A spectroscope is a device to

measure wavelengths and may usea diffraction grating to separatedifferent wavelengths of light.

• A diffraction grating consists ofabout 10 000 lines per cm, and indevices used in schools it is usuallya photographic transparency of anoriginal grating.

SCIENCE BACKGROUND


INVESTIGATION NOTES

Student Safety

• Advise students not to look at the Sun with a spectroscope. Theywill damage their eyesight.

• Ensure that students set up the candle on a stable base and thatthey do not get too close to it.

• Do not allow students to change the gas discharge tubes.

• Most school labs have either the tube-style spectroscope or the flat,triangular plastic type. In either case, caution students not to disturbthe diffraction grating.

• Getting students competent with the spectroscope is often time-consuming. It might be practical to introduce the device a day earlierand practise using it.

• You may want to hand out Investigation BLM 13A for students torecord their answers on.

• To assess students, you may want to use or adapt Rubric 18: Conductan Investigation and/or Rubric 19: Conduct an Investigation—Self-Assessment.

Question

• Ask students if they can think of any lights, other than coloured lights,that they have looked at that seem to give different shades of “whitelight.” How might this observation have helped formulate the questionasked in the Student Book? Students should be able to make aconnection between different types of light and line spectra.

Hypothesis

• Following from the question posed above, students should expect tosee some differences when they look at different light sources with aspectroscope.

Gas Discharge Tubes• When an electric current passes

through the tube and heats the gas,the gas emits a specific linespectrum. Only certain discretewavelengths of light are emitted bythe gas, and these lines are differentfor different elements and

compounds. Line spectra occur onlyfor gases at high temperatures andlow pressure. The light from aheated solid or a dense gaseousobject, like the Sun, produces acontinuous spectrum with a widerange of wavelengths.

Related Resources




At Home

Students coulddemonstrate that light canbe split by a prism as wellas a diffraction grating. Ifthere is any cut glass orcrystal, a prism, or even arectangular fish tank, lightcan be shone at them andthe “rainbow” observedor projected onto a wall.


Prediction

• Students’ predictions should take into account different light sourcesand different spectra for each. A possible prediction could be: differentlight sources give different line spectra.

Experimental Design

• The variable being manipulated here is the wavelength of light.

• Consider daylight viewed through an open window as your controlspectrum.

• The primary purpose of this investigation is to discover thecharacteristics and capabilities of an instrument used in astronomicalresearch.

Materials

• Students should have all necessary materials before beginning theirinvestigation. The materials should also be checked to ensure that theyare safe.

Procedure

• Tube-style spectroscopes need adjusting so that the eyepiece slit isparallel to the lines in the diffraction grating (this instruction may beprinted on the side of the tube).

• Use the WS 13A Bright Line Spectra Recording Chart so students canproduce similar-looking spectra.

• Encourage the use of coloured pencils so students can erase any errorsin their attempts to record the spectra. Remind students to label eachspectrum.

Analysis—Suggested Answers

(a) The light from lamps, candles, or other light bulbs should producecontinuous spectra similar to that created by daylight and anincandescent bulb (white). The spectra may differ in having someregions or even single lines brighter than the spectrum of daylight.

(b) Spectra from gas discharge tubes have emissions in the same order asa visible spectrum. However, because they consist of only oneelement, gas discharge tubes will show only specific lines of colour astheir visible spectra.

(c) Depending upon the tubes you have, most spectra will be dissimilar.

(d) Various light sources give different line spectra. Other than thecontinuous spectra sources such as daylight, most light sources willnot give the same spectra. Light sources with the same spectra wouldcontain the same elements.

(e) One would expect to find a different spectrum for each element inthe Periodic Table.

(f) Observations should support the Hypothesis.


Have students use theInternet and other sourcesto research thedevelopment and types ofspectroscopes available.Encourage them to relatehow advancements inspectroscopes havehelped increase ourunderstanding of ouruniverse. Students coulduse posters andmultimedia presentationsto share the informationthey find with otherstudents.

Math Connections

Have students comparetheir sample spectra withthe spectrum of whitelight in terms of thewavelength or frequencyof the colour bands theyobserve.

Evaluation

(g) Students will probably have created a prediction that was accurate. If they predicted that different light sources give different line spectra,then their observations would support the prediction.

Synthesis

(h) Both samples would need to be burned so the light from each can beviewed with a spectroscope.



Evidence that students can• identify and describe a range of instruments that are used in astronomy (spectroscopes and

bright line spectra)• identify galaxies according to their distinguishing characteristics (elements in a galaxy, red

shift)• identify a variety of dangers in procedures (do not look directly at the Sun)• describe the elements of a valid experiment• use information and conclusions as a basis for further comparisons, investigations, or

analyses• communicate results using a variety of methods• explain how science and technology affect individuals, society, and the environment

(application of spectroscopy to forensics)• describe and demonstrate skills of collaboration and co-operation• identify a variety of technologies and explain how they have advanced our understanding of

science (spectroscopy and identifying elements and observing red shift)• select and use appropriate technologies, including spectroscopes


ESL

• Ensure that ESL students are paired with an English-competentpartner to do this investigation.

• Ask students to read through the investigation beforehand.

Extra Support

• Make sure each student is able to see a spectrum inside thespectroscope.

Extra Challenge

• Ask students to find out what combinations of gases are used indifferent types of fluorescent tubes (for example warm white, coolwhite).


Measuring Distances in Space Page 419




solar system• demonstrate scientific literacy• describe the relationship between scientific principles and technology


universe• components of the universe and solar system• metric system (SI units)• appropriate scale• application of scientific principles in the development of technologies

SKILLS AND ATTITUDES• illustrate astronomical phenomena• make accurate measurements using a variety of instruments• communicate results• use appropriate types of graphic models to represent a given type of

data


information

13.2

Time

30–45 min

Key Ideas


Vocabulary

• light year• parallax• baseline• standard candles• absolute magnitude• apparent magnitude


ConductingCommunicatingCreating ModelsObservingEstimatingMeasuringInterpreting Data

Lesson Materials

per student• notebook paper• calculator

Program Resources

WS 13.2-1 Sample Problem 2:Travel Time for InterstellarDistances: Worksheet

WS 13.2-2 How Far Apart AreStars?

WS 13.2-3 MeasuringDistances in SpaceCrossword Puzzle

SM 13.2 MeasuringDistances in Space


Measuring Distances in Space• Parallax can be used to determine the

distance to stars as far away as 200 light years, and to orbitingsatellites 5 to 10 times farther.Beyond that, parallax angles are toosmall to measure. Instead, acomparison of apparent brightnessand the use of the inverse square law(intensity drops off with the square ofthe distance) is used to estimate thedistance of stars. This technique isnot very precise because we cannotexpect all galaxies to have the samebrightness. However, if we assumethat the brightest stars in the galaxiesor the brightest galaxy in a cluster aresimilar and have about the sameapparent brightness, then this couldbe used as a measure of distance.

Cepheid Variables and Red Shift• Cepheids with a long pulse, are

considered to have the higherintrinsic brightness, as comparedwith those with a short pulse.

• Cepheids are about 1000 timesbrighter than our Sun and can beseen across great distances, makingthem useful distance indicators.

• Review Figure 4 in the Student Bookto see an HST image of galaxy IC 4182. There are 27 knownvariable stars in this galaxy. Thegalaxy was chosen as a site in whichto look for Cepheids because a typeIa supernova was there in 1937.Using the Cepheids in IC 4182,astronomers have been able todetermine the brightness of the1937 supernova.

SCIENCE BACKGROUND


TEACHING NOTES

Getting Started

• Teacher Demo: Estimating HeightA simple method for estimating height can be shown with a longstick. To determine the height of an object, such as the schoolflagpole, use a stick about 2 m long and measure off nine lengths ofthe stick from the pole. Mark that spot and measure one morelength with the stick. Have someone hold the stick upright at themarked spot at the end of the ninth length. With your eye as closeto the ground as possible at the tenth length, look back to the top ofthe flagpole. Where that line of sight crosses the stick, mark thatspot on the stick. Measure the number of centimetres from the markto the ground and multiply by 10. That will be the height of theflagpole in centimetres.

• Possible Misconceptions– Identify: Students may feel that because the distances are so great

and because we cannot physically measure a distance in space, wecannot determine the distance to a star or a distant galaxy.

– Clarify: By using the demonstration on estimating height or theTry This: The Rule of Thumb for Parallax activity, students shouldrecognize that we can determine distances we cannot physicallytraverse. As well, draw their attention to the use of radar and lasersto measure long distances.

– Ask What They Think Now: Ask students, Can you now describe amethod to determine the distance across a river? (Student answers shouldrelate a method identical to the Try This: The Rule of Thumb forParallax.)

Guide the Learning

• To begin the lesson, have students complete Try This: How ManyStars?

2

1

• The largest distances are estimatedby comparing the apparentbrightnesses of type Ia supernovas.All type Ia supernovas have a similarorigin; they collapse to a neutron starat 1.4 solar masses, and their brief,explosive burst of light is predictedto be of the same total luminosity.

• Red shift in the line spectra ofelements is related to the expansionof the universe. Red shift can beused to determine the direction andspeed of movement of stars, anddistance of stars from us. It worksbest for objects 107 to 108 lightyears away.

Related Resources










TRY THIS: HOW MANY STARS?

Purpose

• Provide a simple model through which students can gain insight into thenumber of stars in the Milky Way.

Notes

• Many students may not be familiar with a thimble. Either provide one to look at,or carefully describe one.

Suggested Answers

A. Depending upon the size of dot made, between 10 and 15 per side arepossible. Therefore, it will take 100 to 225 dots to fill the square.

B. At 10 dots or grains per side, there would be 1000 grains to fill a 1 cm3 cube.

C. To fill a 2.5 cm3 thimble would take 2500 grains of sand.

D. With 2.0 � 1011 stars/2.5 � 103 stars/thimble, it will take 8 � 107 or 80 000 000thimbles.

At 0.0025 L/thimble � 80 000 000 thimbles, that equals 200 000 L of sand.

It will therefore take a dump truck to hold all the sand. In fact, as the largest ofdump trucks holds 11 500 L, it will take at least 18 dump trucks to hold thesand.

• Use the Reading and Thinking Strategy of asking questions whenreading this section.

• To help understand parallax and long baselines, review Figures 1, 2,and 3.– Use Figure 1 to demonstrate how to sight a distant pair of objects

using an extended arm and upright thumb.– Use Figure 2 to demonstrate how to use trigonometry, a known

baseline, and the determined angle to calculate the distance to anobject. The object could be across a river or a distant mountain top.

– Use Figure 3 to point out that the longest baseline possible fromEarth is the major axis of Earth’s elliptical orbit.

• Use the two lower images in Figure 4 to show one Cepheid variablechanging in brightness.

• Use Figure 5 to demonstrate that the ideas of absolute and apparentmagnitude are likely within the experience of most students. Use itto point out that at 5 m, a headlight will be brighter than the tablelamp and the flashlight. However, at the distances shown in (b), thethree lights will appear to be of the same brightness or apparentmagnitude.

• In Figure 6, point out that diagrams sometimes reverse the violetand red ends of the spectrum. The colours still, however, correspondto the same range of wavelength.

• Sample Problem 1—practice problem solution: (a) Epsilon Eridani is 10.5 light years (l.y.) away.

In kilometres that is 10.5 l.y. � (9.5 � 1012 l.y./km)� 99.75 � 1012 km or 9.98 � 1013 km


Have students use theInternet and other sourcesto research the distanceto at least three stars orgalaxies that have beencalculated using a varietyof methods (i.e.,trigonometric parallax,Cepheid variables, and redshift). Encourage them toreview and compare theestimated distances andnote any discrepancies.Challenge students toexplain the variations anddetermine which methodthey consider the mostreliable.


At 50 000 km/hr it will take

�95..908�

�

11004

1

k

3

mk/mh

� �

� 1.995 � 109 h or 2.0 � 109 hIn years, that will be

2.0 � 109 h � �214dh

� � �36

15yd

� � 0.000228 � 109 y

� 2.28 � 105 y

It will take 2.3 � 105 years to reach Epsilon Eridani.

(b) 230 000 years � �1 g

5e0n

yereaatrison

�

� 4600 generationsIt will take 4600 generations of people to reach Epsilon Eridani.

• Have students practise this type of calculation using WS 13.2-1Sample Problem 2: Travel Time for Interstellar Distances: Worksheet.

• Complete Try This: The Rule of Thumb for Parallax.

9.98 � 1013 km � h��

5.0 � 104 km

TRY THIS: THE RULE OF THUMB FOR PARALLAX

Purpose

• Demonstrate a method of determining the distance to an object using parallax.

Notes

• This method is quite subjective and relies on two features: that the two chosenobjects are the same distance from the observer, and that the observer canestimate the distance between the two objects using a known standard (e.g., the average height of a person or the width of a typical building lot).

• If you carry out this activity in a school’s sports fields using trees or houses inthe distance, it may help to pre-measure these distances.

Suggested Answers

A. Point A could be a tree in the distance. Point B could be another tree or shrubsome distance away from A but in the same plane.

If backyards are 10.06 m wide in your city, and the two objects are threebackyards apart, then the estimated distance between A and B would beapproximately 30 m.

The distance to the objects A and B is 10 � 30 m or 300 m.

B. Using objects the same distance away should achieve similar results.

C. The accuracy depends on a variety of factors that include keeping all body partsstill as the objects are sighted, an ability to estimate at a distance, andconsiderable opportunity for error in the process and the ability to estimate.


• To help students develop an appreciation of the vastness andemptiness of space, have them complete WS 13.2-2 How Far ApartAre Stars?

• Have students complete WS 13.2-3 Measuring Distances in SpaceCrossword Puzzle as a review of the vocabulary in this section.

• Assign the Check Your Understanding questions.

3

At Home

Have students use one ofthe techniques in thissection to estimate adistance or a height ofsomething in theirneighbourhood.



1. Distance, brightness, size, obscuring dust, and light pollution are some of thefactors that limit our ability to see stars.

2. Planets are close enough to use kilometres—the most distant planet,Neptune, is 4497 � 106 km away from the Sun. Proxima Centauri, the closeststar to our Sun, is 4.22 light years away. In kilometres, this would be 4.0 � 1013 km. It is easier to state long distances in light years, as opposed tokilometres.

3. The diameter of the Milky Way expressed in kilometres is

1.0 � 105 light years � 9.46 � 1012 km/light year

� 9.5 � 1017 km.

In AU, the distance is

9.5 � 1017 km � 1 AU/1.5 � 108 km

� 6.3 � 109 AU.

4. The number of galaxies is estimated at 100 billion.

5. The volume of the universe is estimated at 1 � 1030 cubic light years.

6. A baseline is an imaginary line from which the distance to an object ismeasured. The major axis of Earth’s elliptical orbit is the baseline used inastronomy. The distance of the baseline is varied because the greater thedistance to be measured, the longer the baseline needs to be.

7. When your thumb jumps, you then choose a new item that now lines up withyour thumb and that appears to be the same distance away as the originalobject that jumped. You then estimate the distance between the two objects.The baseline is the distance between your eyes.

8. Beyond 200 light years, the angles from our baseline are so small thatobservational errors make the calculations invalid.

9. Increasing the baseline and measuring angles carefully are two methods toincrease the accuracy of triangulation.

10. A Cepheid variable is an unstable yellow supergiant star 1000 times brighterthan the Sun. Cepheids pulse, varying in size and brightness.

11. Cepheid variables are standard candles because they are of known brightnessand they behave in a predictable way.

12. Absolute magnitude is the actual amount of light given off by a star at astandard distance. Apparent magnitude is the brightness of the star as we seeit in the night sky. At the same distance, three different light sources give offdifferent amounts of light. This is their absolute magnitude. At differentdistances, the same three light sources seem to give off the same amount oflight. This is their apparent magnitude.

13. With increasing distance, the brightness decreases, or dims.

14. Large, bright Cepheids pulse more slowly.

15. Cepheid B has the greater absolute magnitude (it has a slower pulse).

16. A galaxy with a slight red shift is closer to us and moving away more slowly.This would be the top diagram in Figure 6 on page 422. A galaxy with a largered shift is farther away from us and is moving away faster. In Figure 6, thebottom figure has the largest red shift and is the farthest away.

17. (a) 1 light year � 9.5 � 1012 km

4.2 light years � 9.5 � 1012 km/light year

� 40 � 1012 km

Proxima Centauri is about 40 � 1012 km away.

(b) �40

40�

01000

1

k

2

mkm

� � h

� 1 � 109 h

At 40 000 km/h, it will take 1 � 109 h to reach the star.

Math Connections

Have students practiseusing similar triangles andtrigonometric ratios tocalculate unknowndistances. Review how to determine tangent,sine, and cosine onstudent calculators.Review right triangle sidesof adjacent, opposite, andhypotenuse. Review angleof inclination.

Have students use therules of exponents to solvethe sample problems onStudent Book page 423.Remind students of theimportance of using thecorrect units when solvingproblems. Reviewrearranging formulas usingalgebra.


(c) 1 � 109 h � 1 d/24 h � 1 year/365 d = 0.000114 � 109 years

� 1.14 � 105 years

The journey will take 1.14 � 105 years.

(d) 1.14 � 105 years � 1 generation/50 years

� 2280 generations

It will take 2280 generations to reach the star.

Ask Questions

• Discuss how asking questions while reading their Student Book willhelp students understand and remember new information. (Keeps thereader more alert, helps you respond to new information more fully.)

• Discuss how students might develop questions that will guide them intheir reading of Section 13.2. For example,– Scan the subheadings and turn them into questions.– Scan for vocabulary words and use them as the basis for questions. – Scan for diagrams and use them to develop questions.

• Arrange students in pairs to develop their own set of questions and toread the section.

• Conclude by bringing the class together to share their questions.

Reading and

Thinking Strategies

Taking Tests

• When answering short answer test questions, it is helpful for studentsif they know to read the question carefully to understand what it asks;underline key words in the question to help focus their attention; andanswer the question by using key words from the question and includea reason, an example, or an explanation.

Strategies for Success

ESL

• Add new vocabulary words to the visual dictionary along with termssuch as Cepheid variable stars.

Extra Challenge

• Ask students to research other methods of determining distance inspace such as type Ia supernovas, globular clusters, and so on, and havethem form opinions on the usefulness of these methods.



Evidence that students can• identify and describe a range of instruments that are used in astronomy (parallax)• give examples of how astronomers use astronomical and space exploration technologies to

advance understanding of the universe and solar system (red shift, parallax, etc.)• identify star types according to their distinguishing characteristics (Cepheid variables)• identify the main points in a science-related illustration• identify a variety of technologies and explain how they have advanced our understanding of

science (parallax, absolute and apparent magnitude)


Investigation: Triangulation: MeasuringDistances to the Stars Page 448



the universe and solar system• perform experiments using the scientific method• represent and interpret information in graphic form• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour


universe• metric system (SI units)• elements of a valid experiment• appropriate scale

SKILLS AND ATTITUDES• make accurate measurements using a variety of instruments• communicate results• use appropriate types of graphic models to represent a given type of

data• use models to demonstrate how systems operate• demonstrate ethical, responsible, co-operative behaviour




13B

Time

45–60 min

Key Ideas



PredictingConductingRecordingAnalyzingEvaluatingCommunicating

Lesson Materials

per pair• cardboard (old file folders)• angle measurer template

(BLM 13B-1)• glue stick• scissors• split pin• protractor• pencil• string and tape• metre stick• paper• centimetre ruler

Program Resources

Investigation BLM 13BTriangulation: Measuring

Distances to the StarsRubric 18: Conduct an

InvestigationRubric 19: Conduct an

Investigation—Self-Assessment

BLM 13B-1 Angle MeasurerTemplate

BLM 13B-2 MeasuringAngles

SSP Rubrics 5, 6, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 21, 22


Measuring Distances in Space• Check the Science Background of

Section 13.2 for more informationabout parallax.

• Friedrich Bessel (1784–1846) wasthe first to use trigonometric parallaxto measure the distance to a star. In1838, he determined the distance tothe star 61 Cygni, and did so towithin a few percent of our modernmeasurements.

• The space probe Hipparcos,launched in 1989, used trigonometricparallax to measure the distance to100 000 stars.

• GAIA, set for launch in 2010, will beeven more precise. It will be able toperform parallax measurements 100 times deeper into space thanHipparcos.

SCIENCE BACKGROUND

INVESTIGATION NOTES

Student Safety

If this investigation is carried out in a classroom, even with the desksmoved out of the way, crowding and space to move could be an issue.You may consider letting groups perform the measurements in turn.

• Measurement errors will increase as students hold and use the anglemeasurer higher above the baseline.

• The distant object at Point C should be as small as possible to reducean “aiming” error with the angle measurer.

• Angles A and B do not have to be the same, as long as the line on thescale diagram from point C to the baseline is 90° (Step 10).

• Encourage students to be as precise as possible with theirmeasurements. Students should double-check a measurement beforedeciding on an angle.

• Encourage the use of graph paper to draw scale diagrams.

• You may want to hand out Investigation BLM 13B for students torecord their answers on.


Question

• For the question posed in the text, you may want to point out that anindirect method of measuring is necessary because the distant objectcould be across a river and, as such, inaccessible.

Prediction

• The Prediction in the Student Book is not an attempt to get studentsusing angles close to 0° or 90°. In fact, angles from 10° to 80° willwork more effectively. An object far enough away to give angles ofnearly 90° demonstrates the limit of this technique.

• A student prediction could be the following: angles that are not closeto 0° or 90° will give more accurate results. (Students should be awareof this after reading Section 13.2.)

Experimental Design

• The method of triangulation, or parallax, involves two steps: first, themeasurements of two angles from a known baseline to a single objectare made; then a scale diagram of the measurement is drawn todetermine the unknown distance. Note the Math Connection for anextension to this problem.


Related Resources



Math Connections

Review trigonometryconcepts found in MathConnections in Section13.2. This technique tiesin with the topics ofsimilar or right triangles,as well as tangent, sine,and cosine ratios.Students could use thisdata and solve using anyof the ratios.

Materials

• To save time, you may want students to assemble the angle measurer aday before doing the Investigation.

• The angle measurer needs to be constructed carefully. Any errors willaffect measurement and calculations later.

Procedure

• Supply students with cardboard, such as old file folders, and BLM 13B-1 Angle Measurer Template. Students should glue the templateto the cardboard.

• Students should keep the hole for the split pin as small and as roundas possible.

• For Part 2, a large, open space like the school gym or cafeteria may bemore practical than the classroom.

• Students should orient the angle measurer carefully over baselinepoints A and B to avoid creating errors.

• Remind students that scale drawings should occupy a full page toimprove their accuracy.

• When angle measurements and scale drawings are complete, havestudents measure the actual distance from their baseline to the objectthey targeted for calculations.

Analysis—Suggested Answers

(a) It is indirect because the distance is calculated on a scale diagramrather than being measured directly.

(b) Stars farther and farther away have angles nearly 90° to the baseline.At 90°, triangulation no longer works.

(c) Longer baselines will provide more accurate measurements. Thelonger the baseline, the further from 90° angles A and B will be.

(d) Unless students have prior knowledge of the layout chosen, theircalculated distance will likely be more accurate than their estimateddistance. Estimates may be less accurate because of students’inexperience in judging distance and because of variances in theirdepth perception.

(e) Sample calculation

percentage of error � � 100 %

� �35.8 m

42�

.042.0

� � 100 %

� 14.8 %If students calculate the distance as 35.8 m and the actual distance is42 m, their error is approximately 15 %.

(f) A conclusion may indicate that with care, students can determine thedistance to a remote object.

calculated distance – actual distance��

actual distance



Have students use theInternet and other sourcesto research technologyused in measuringdistances both on Earthand in space. Studentscould present theirfindings by creating amini-poster of theirselected measurementtechnology. They couldplace a graphic of the itemin the centre of a pageand create text boxesnaming and explaining theparts and their function.Students could includeinformation about theitem’s historicaldevelopment and anycommon applications ofthat type of measurementdevice.

Evaluation

(g) Sources of error include construction of the angle measurer, use of theangle measurer, accuracy of the baseline length, size of the targetobject, careful construction of the scale diagram, and interpretation ofthe scale diagram.

(h) Without accurate angles, the calculation of distance will beinaccurate.

(i) Accuracy can be improved by addressing any of the sources of errornoted in (g) above.


ESL

• Partner ESL students with an English-competent partner.• Try to adjust the groups to include someone with strong math skills

and someone with good manual dexterity.

Extra Support

• Have students use BLM 13B-2 Measuring Angles to practise use of aprotractor.

• Partner students with a group with strong math skills and manualdexterity.

Extra Challenge

• Have students use triangulation to find the distance to a very remoteobject such as a distant building or mountain top. Then studentsshould confirm the distance with a topographical map or a mappingprogram from the Internet.



Evidence that students can• identify and describe a range of instruments that are used in astronomy (angle measurer)• give examples of how astronomers use astronomical technologies to advance

understanding of the universe and solar system (parallax and triangulation)• use information and conclusions as a basis for further comparisons or analyses• communicate results using a variety of methods • identify and use the most appropriate type of graphic to convey information (scale diagram)• describe the qualities of the scientifically literate person, such as respect for precision• describe and demonstrate skills of collaboration and co-operation


The Birth of Stars, and the Sun Page 425


PRESCRIBED LEARNING OUTCOMES• describe the major components and characteristics of the universe and

solar system• demonstrate scientific literacy• describe the relationship between scientific principles and technology


universe• components of the universe and solar system• metric system (SI units)

SKILLS AND ATTITUDES• use bar graphs, line graphs, pie charts, tables, and diagrams to extract

and convey information• acquire and apply scientific and technological knowledge to the benefit





13.3

Time

45–60 min

Key Ideas

Nuclear fusion powers starsand is the force behind solarflares, prominences,sunspots, and the solar wind.

Vocabulary

• nuclear fusion• core• radiative zone• convective zone • photosphere• chromosphere• corona• sunspots• solar prominences• solar flares• solar wind

Program Resources

BLM 13.3-1 Nuclear Fusion inStars

WS 13.3-1 The Structure ofthe Sun

SM 13.3 The Birth of Stars,and the Sun


Solar Anatomy• About 92.1% of the Sun’s atoms are

hydrogen, 7.8% are helium, and theheavier elements like carbon,nitrogen, oxygen, neon, magnesium,silicon, and iron constitute theremainder. The Sun is neither a solidnor a gas; rather, it is plasma that isgaseous near the surface and densertoward the core where fusionoccurs.

• Fusion in the Sun’s core provides theenergy that powers the Sun andproduces all the heat and light. Whatwe know about how energy escapesthe Sun is from theoretical models ofthe Sun’s interior, combined withobservations such as the Sun’smass, its surface temperature, andits total energy output.

• The core extends �14� of the way from

the centre of the Sun to the surface.

• Above the core is the Sun’s interior,which is like two nested shells. Theinnermost shell is the radiative zone,which reaches �

34� of the way to the

surface. Here, the plasma density isvery high and radiation does nottravel directly outward. Instead, itgets bounced around following azigzag path, taking at least 170 000 years to reach the surface.

• The outermost of the two shells isthe convective zone, and at a cool 2 � 106 °C, the plasma is too cooland opaque to allow radiation topass through. However, convectioncurrents driven by the inner heatcarry large masses of hot plasma uptoward the surface. In this manner,energy is carried through theconvective zone far faster than itpassed through the radiative zone.

SCIENCE BACKGROUND

TEACHING NOTES

Getting Started

• Possible Misconceptions– Identify: Students may believe that only light and heat reach us

from the Sun.– Clarify: Solar prominences in particular eject, on average,

100 billion tonnes of material. Most of this material misses us, butthe charged particles can cause damage or visible effects on Earth.

– Ask What They Think Now: Ask, If a particularly large amount ofmaterial from the Sun hit Earth and disrupted our communicationssatellites, what would we lose? (Students should be able to respondthat we would lose TV, radio—for example, airplane to controltower—and cell phones, and more.)

Guide the Learning

• Use the Reading and Thinking Strategies of analyzingdiagrams/checking understanding, followed by determining thedefinitions of scientific and technical terms, when reading thissection.

• The images in Section 13.3 contain a lot of detail. Go over themcarefully with students, pointing out the following:

• Figure 1– Use BLM 13.3-1 Nuclear Fusion in Stars to help explain the

process of nuclear fusion in a star. Point out that it takes a totalof three protons to form one helium-3 nucleus. One of thoseprotons is converted to a neutron as deuterium is formed.

– Note that positrons (positive electrons) and neutrinos are lostwhen deuterium forms.

2

1


• The Sun has a complex andchanging magnetic field that causesthe formation of phenomena likesunspots and prominences.Measurements have shown that themagnetic field changes on an 11-year cycle, which alsocorresponds to peaks in sunspot,solar flare, and prominence activity.

Solar Flares, Prominences, andSunspots• Sunspots are caused by powerful

magnetic fields that produce activeregions that spawn solar flares andcoronal mass ejections (CMEs) orprominences.

• Observations from the MichelsonDoppler Imager (MDI) aboard SOHOhave shown material flowing out ofthe sunspots. Below a sunspot’ssurface, quantities of material flowingat about 5000 km/h create a planet-sized whirlpool. The inflow pulls themagnetic field lines together andbottles up the normal outward flow ofenergy from the hot solar interior. Thisleaves the surface cool and darkerthan its surroundings—a sunspot. The MDI uses a systemsimilar to ultrasound in a techniquecalled acoustical tomography to makethese observations.

• The largest prominence observed bySOHO was 350 000 km long, whichis 14 times the diameter of Earth.

Related Resources

Dickinson, Terence. TheUniverse and Beyond. 4thed. Richmond Hill, ON:Firefly Books, 2004.







An Introduction toAstronomy, Vol. 2, 5, 7,12 (VHS)






– Module 2: The Sun andStars

– Interior of the Sunapplet

Quirks and Quarks audioclips

– Staring at the Sun– Watching the Sun from

Earth

• Figure 2– The varying size of the arrows shows the ultimate balancing

effect of the outward flow of energy and the inward collapsecaused by gravity.

• Figure 3– Use WS 13.3-1 The Structure of the Sun to review the layered

structure of the Sun. Have students make notes around thediagram as they learn about the Sun’s layers.

– Review each layer of the Sun for details of its anatomy.

• Figure 4– This is one of the most spectacular photos in Chapter 13. It

shows details of the dark umbra and the less dark penumbra, theless regular shape of the smaller trailing spot, several smaller spotsclustered about the pair, and details of the granules or surface ofthe convection cells.

– Direct students to look for photos of sunspots on the Internet.Have them begin their research on the Nelson Science website.

• Figure 5– To further clarify the Possible Misconception noted earlier, point

out the amount of material leaving the Sun in this image.Another massive prominence photographed in September 1999can be found in the web links on the Nelson Science website.This photo was an Astronomy Picture of the Day from NASA(from April 16, 2006).


• Details of solar anatomy learned now will prove useful in latersections as students learn about the life cycle of a star. Ensure thatstudents understand the concepts in this section before they proceedto Section 13.4.

• Assign students the task of making a labelled model of the Sun alongwith a report that explains the key features of each layer.


3



1. The Sun is about 5 billion years old.

2. Nebulas form stars and their surrounding planets. Stars are formed whennebulas collapse in on themselves as small amounts of matter collide andbecome a larger mass with stronger gravity.

3. Hydrogen is the simplest of all atoms, containing only one proton.

At Home

Students may want tosearch for other images ofthe Sun to share in class.

Art Connections

The impressive detail ofrecent sunspot and solarsurface images could bethe source of a piece ofabstract artwork.


4. A star will form from a nebula as its own gravity or a shock wave from asupernova causes it to collapse. Regions of greater density draw morehydrogen to themselves as they grow. These are the beginning of theprotostar. As the protostar grows, it gathers more material into its centre. The amount of heat in the centre becomes large enough to start nuclearfusion, and the star ignites. Student diagrams may resemble the following.

5. A nebula can collapse under its own gravity or from the impact of a shockwave from a supernova.

6. Gravity pulls more and more material toward the densest regions of aprotostar. The largest and usually most central dense region eventually gainsenough heat energy from the collisions of incoming material to ignite as a newstar.

7. Nuclear fusion requires great amounts of heat. (The heat provides enoughkinetic energy to drive the nuclei together.)

8. Helium concentrates at the core because it is denser than hydrogen.

9. It takes a total of six hydrogen nuclei, or protons, to form one helium nucleus.

10. Energy is released during the fusion of two helium-3 nuclei. The energy isreleased as great quantities of heat, light, X-rays, and gamma rays.

11. When thermal expansion balances gravity, the young star stabilizes at aparticular size.

12.

Sequence of events• Light is produced in the core.• The dense radiative zone keeps energy in for hundreds of thousands of

years.• In the convective zone, swirling streams and eddies carry energy outward to

the photosphere.• Photosphere is the visible surface of the Sun.• Chromosphere is the inner atmosphere.• Corona is the outer atmosphere.

13. During a total solar eclipse, the Moon blocks the bright body of the Sun andallows viewing of the less bright chromosphere and corona.

14. Sunspots are caused by disturbances in the Sun’s magnetic field.

Gravity collapses a nebula into a protostar.

Fusion begins in the core, and thermal expansion pushes outward.

Thermal expansion and gravity balance each other out, and the size of the star is set.

corona

chromospherephotosphereconvective zoneradiative zonecore

path of light and heat outfrom the core


Have students createposters or multimediapresentations on theanatomy and/or life cycleof a star. Encouragestudents to use theInternet to locateappropriate graphics. Theycan use text boxes toprovide information thathelps explain their postersor presentations.


15.

16.

17. �158

�

�

11008

9

kkmm

2

2� � 3.6 � 101

36 Earths would fit in the sunspot of April 8, 1947.

18. Solar prominences release tonnes of glowing hydrogen from the photosphere.The hydrogen is held in place for several weeks by the twisted magnetic fieldsabove the surface.

Solar flares form above active sunspots whose rapidly changing magneticfields cause the release of gas and charged particles. They last only a shorttime.

Both flares and prominences release great amounts of X-rays; gamma rays;charged particles, like protons and electrons; and even some of the Sun’smass. These discharges affect our weather, our communications satellites,and could even harm astronauts in space.

trailing sunspot

leading sunspot

direction of Sun‘s rotation

magnetic south

magnetic north

direction of Sun’s rotation

Top view of four solar granules showing sideways convective flow at the surface.

Side view of two granules showing convection and the release of light.

Light escaping the photosphere


19. Solar wind is ionized gas emitted all the time from the Sun, especially fromflares and prominences. The solar wind disrupts communications equipment,satellites, and so on and causes the auroras seen on Earth.

20. (a) Diagram (a) is the correct pattern of circulation.

(b) The kinetic molecular theory indicates that as a material is heated, its particles move faster and farther apart, making it less dense. Thus, the liquid rises above the heat source.

Analyze Diagrams/Check Understanding

• Read the introductory paragraph and the subsection Stellar (Star)Birth on Student Book page 425 with students.

• Arrange students in pairs to complete the Learning Tip activity onpage 425.

• Conclude by having students check their understanding of nuclearfusion in stars by explaining Figures 1 and 2 to each other. Then havestudents reverse roles.

Determine the Meaning of Scientific and Technical Terms

• Have students scan the subsection Solar Anatomy on Student Bookpage 426 for new terms. List the words on the board. Ask students toidentify words they know and words that are new.

• Arrange students in pairs to read the subsection and Figure 3, askingthem to stop at the end of sentences where the new words appear inthe text. Have them take turns explaining the meaning of the newwords to each other.

• Conclude by having students draw a diagram in their notebooks toshow the pathway of light from its point of origin through each zoneof the Sun. Have them include labels and a brief explanation of whathappens in each zone.

Reading and

Thinking Strategies

ESL

• Ask students to add the new vocabulary words to their visualdictionaries and to also include X-rays, gamma rays, convection cell,and magnetic field.

• Assign this section for pre-reading before covering it in class.• A videotape of the Sun’s activity and eclipses could be shown to

students. These videotapes may be available in the school or throughorganizations such as the Canadian Space Agency (CSA). You maywant to contact the Larkin Kerwin Library at the CSA to see whetherthey have any appropriate resources.

Extra Support

• For students who need additional support with the reading in thissection, use SM 13.3 The Birth of Stars, and the Sun.

Extra Challenge

• Ask students to learn more about sunspots, in particular, the effect ofthe magnetic forces and differential rotation of layers of the Sun.


ScienceWORKS: SOHO: The Solar andHeliospheric ObservatoryPAGE 430

• SOHO is designed to study the internal structure of the Sun, itscomplex outer atmosphere, and the origin of the solar wind—a streamof highly ionized gas that blows continuously outward through thesolar system. Scientists hope SOHO can solve some mysteries aboutthe Sun, including the heating of the corona, how the solar wind isgenerated, and what the complex interior of the Sun is actually like.

• SOHO’s uninterrupted view of the Sun 1.5 million km sunward fromEarth occurs because SOHO is set in a halo orbit around the L1Lagrangian point (the position between Earth and the Sun where thecombined gravitational pull of the two large bodies provides exactlythe centripetal force required to have the satellite rotate with them. Itis analogous to a geosynchronous orbit.) It has been functioning at thislocation since 1995.

• SOHO can detect solar waves that move through the Sun’s interior,similar to the way that sound waves move through the air.Temperature, internal composition, and movement within the Sunchange the movement of the solar waves and give clues to conditionsin the Sun’s interior. Three instruments aboard SOHO are dedicatedto this new science of helioseismology.

• To observe the corona, which is millions of times fainter than thephotosphere, we usually wait for a total eclipse of the Sun. Because ofits high temperature, the corona is highly ionized and gives off a varietyof energies or spectral emissions. The emissions in the ultraviolet or theX-ray wavelengths are absorbed by Earth’s atmosphere and must beobserved from space. SOHO detects these UV and X-ray emissions andproduces some spectacular images of the Sun.

• The solar wind is an ionized, or magnetized, plasma blown off by theSun. The plasma blow-off that creates the solar wind results fromheating in the Sun’s corona, which is crisscrossed by magnetic fieldsthat form either closed loops or open directly into space. The openloops are the source of the fast solar wind. SOHO observes the coronaand measures the composition of the solar wind to help understandhow it is formed and accelerated.



Evidence that students can• describe the formation of the universe• describe the processes that generate and events that distribute the energy of the Sun and

other stars (e.g., nuclear fusion, solar flares, prominences, sunspots, the solar wind)• identify the main points in a science-related illustration• identify a variety of technologies and explain how they have advanced our understanding of

science



Investigation: A Rotating Sun? Sunspots Provide the Answer Page 450


the universe and solar system• demonstrate safe procedures• perform experiments using the scientific method• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour• demonstrate competence in the use of technologies specific to



universe• motion of the constellations, planets, moons, sun, asteroids, and

comets• elements of a valid experiment

SKILLS AND ATTITUDES• recognize dangers• make accurate measurements using a variety of instruments• communicate results• use appropriate types of graphic models to represent a given type of

data• acquire and apply scientific and technological knowledge to the benefit





13C

Time

45–60 min

Key Ideas



PredictingConductingRecordingAnalyzingEvaluatingSynthesizingCommunicating

Lesson Materials

per group• binoculars focused for

distant viewing• tripod or other mounting

system• masking tape• cardboard or Bristol board

(at least 216 mm � 279 mm)• scissors• smooth white paper

attached to the cardboard• clock or watch• logbook or notebook

Program Resources

Investigation BLM 13C A Rotating Sun? SunspotsProvide the Answer

Rubric 18: Conduct anInvestigation

Rubric 19: Conduct anInvestigation—Self-Assessment

WS 13C Sun Grid SSP Rubrics 5, 6, 9, 10, 11, 12,

13, 14, 16, 15, 17, 18Nelson Science Probe 9

websitewww.science.nelson.com

The Solar Cycle• The Sun goes through an 11-year

cycle of solar activity. In the currentcycle, with minimum activity in 2007,solar activity increases to a peak in2012. The next minimum occurs in2018. An impressive image showingthe solar cycle can be found on theNelson Science website.

• One idea proposed to explain the 11-year cycle starts with the Sun’smagnetic field aligned from pole topole. Because of the Sun’s

differential rotation, the magneticfield at the equator rotates fasterthan at the poles. This twists themagnetic field lines until they burstthrough the surface of the Sun,creating sunspots, flares, loops, andprominences.

Solar Rotation• The Sun rotates once about every

25.4 days. This means that sunspotswill pass across one side of theSun’s surface in about 12 to 13 days.

SCIENCE BACKGROUND

INVESTIGATION NOTES

Student Safety

Remind students to perform this investigation with strict safetyprecautions.

• Never look directly at the Sun, and never look through binocularsor any other instrument at the Sun.

• Do not bring the Sun’s image to a fine point on the paper and donot put any body part under that focused point.

• The purpose of the cardboard is to create a shadow to increase thecontrast for the projected image of the Sun and its sunspots.

• Before mounting the binoculars, focus them to infinity.

• In periods of low sunspot activity, you should be prepared to not findany. Check the SOHO website and see what activity is present.

• If a tripod is unavailable, you could use a pair of ring stands withenough weight on them to stabilize their bases.

• Mounting the screen on a surface that is angled and stable wouldallow it to be moved in increments until a focused image forms.



• The Sun’s differential rotation alsodemonstrates that it is not a solidbody. At the equator it rotates oncein 25.4 days, at 40° latitude it rotatesonce in 29 to 30 days, and at thepoles it rotates once in 35 days. Thecore rotates in 27 days.

Sunspots• A sunspot is a region on the surface

of the Sun that is cool and darkcompared with the surroundingphotosphere. The average surfacetemperature of the Sun is 6000 °C;sunspots are 1500 °C cooler.Sunspots last from a few hours to afew months. Sunspots can changesize and shape during the time theyexist.

• Sunspots are regions of the Sunwhere the magnetic fields arethousands of times stronger thanEarth’s magnetic field. Sunspotsoften appear in pairs, with a leadingand trailing spot. One spot has a

positive, or north, magnetic fieldwhile the other has a negative, orsouth, magnetic field. The field isstrongest in the darker and coolerpart of the sunspot—called theumbra. The field is weaker in thelighter part—the penumbra. Overall,sunspots have a magnetic fieldabout 1000 times stronger than thesurrounding photosphere.

• The intense magnetic field below asunspot prevents the normal up-flowof energy from the hot solar interior.Thus, the sunspot is cooler anddarker. As such, convection in thisarea stalls. The cooler, densermaterial of the umbra plungesinward at nearly 5000 km/h. Thisdraws in the surrounding plasma andmagnetic field lines toward thesunspot’s centre, promoting furthercooling and perpetuating thesunspot. Thus, a strong magneticfield stabilizes the sunspot.

Related Resources




Question

• Although rotation of the Sun is not grasped intuitively, the extendingconcept that leads to this question is, What does the rest of the solarsystem do?

Prediction

• A sample prediction could be: if the Sun rotates, then we should beable to see sunspots moving either hourly or from day to day.

Experimental Design

• Binoculars will form a real image of the light source and, thus, theimage can be projected onto a screen.

Materials

• Students should have all materials before beginning their investigation.Materials should also be checked to ensure that they are safe.

• Try to acquire sets of binoculars that students’ parents are willing todonate. Only one side needs to function for this exercise to work.

• Distribute WS 13C Sun Grid to students. This worksheet is used tohelp plot the position of each sunspot and make it easier to track.

Procedure

• The real image projected by the binoculars will be upside down andreversed.

• If students view for any length of time, the tripod or binocular mountwill have to be moved to account for Earth’s rotation.

• For the purposes of orienting to the Sun, consider its top to be northand its left side to be west.

• Given the duration of the Sun’s rotation, any spot near the centre ofthe disc will be there for several days in a row and will be ideal forstudents to view and track.

Analysis

(a) The Sun’s image would be upside down and backward. The bottomof the students’ image would be north.

(b) After appearing as a near homogeneous disc in 2007, the Sun shouldshow an increasing number of sunspots from 2007 to 2012.

(c) The sunspots appear to move across the projected disc of the Sunfrom right to left. In proper orientation, as visible on the SOHOwebsite, the sunspots will move from left to right (west to east).

(d) A rotation of 25.4 days (other sources give up to 27 days for therotation at the solar equator) is equal to 609.6 h (25.4 d � 24 h/d).

Therefore, in 1 h students will see about �6110� of the Sun’s rotation.

The number of degrees that this represents is �6110� rotation � 360°

per rotation, or 0.6°/h. That converts to 14.4°/24 h.



Numerous websites existto give current andauthoritative informationabout the Sun. You couldchallenge students to findthe correlation betweensunspots and solaractivity, and make a shortreport.

(e) The amount of visible rotation in 1 h is too small to notice; therefore,rotation should be observed over several days. As part of a properlyexecuted science experiment, the Sun should be viewed at the sametime every day for several days. In practical terms, to demonstraterotation alone, the time of day would not be a significant source oferror because as long as the spot moves, rotation has been confirmed.

(f) The Sun does rotate. The movement of the sunspots across the face ofthe Sun is the supporting evidence.

Evaluation

(g) By noting a change in the position of a sunspot from day to day,students can demonstrate the rotation of the Sun.

(h) Modifications could include use of a professional tripod and motormount or the use of daily sunspot images captured by SOHO.

Synthesis

(i) Barring any anomalous behaviour, sunspot activity should increase from2007 to 2012 and student observations should match those predictions.

(j) We need to study the Sun because the disruptions caused by anincrease in particle emissions from the Sun and the solar wind candisrupt our communication satellites and our ground-basedcommunication systems.

(k) The increase in radiation with increased solar activity poses asignificant health hazard to a colony on the Moon where there is noatmosphere to absorb that radiation. High levels of radiation wouldhave to be addressed when considering housing, clothing, etc.


ESL/Extra Support

• If safety is an issue, assign this investigation as an Internet exerciseusing the activity on the SOHO website (found on the Nelson Sciencewebsite).

• Check that each group can form an image of a light bulb before theytry to create an image of the Sun.

Extra Challenge

• Ask students to use the Internet and other sources to researchdifferential rotation and ask them to explain to the class what it is, whyit happens, and how it contributes to sunspots.



Have students createmodels, posters, ormultimedia presentations(i.e., PowerPoint or HyperStudio presentations) toexplain the causes,frequency, and intensity ofsunspots. Encouragestudents to include boththe possible effects ofsunspots on life on Earthand what can be done tominimize the potentiallynegative effects ofsunspots.


Evidence that students can• identify and describe a range of instruments that are used in astronomy (e.g., binoculars)• identify a variety of dangers in procedures (do not look directly at the Sun)• use information and conclusions as a basis for further comparisons or analyses• communicate results using a variety of methods• explain how science and technology affect individuals, society, and the environment• describe and demonstrate skills of co-operation and collaboration• select and carefully use appropriate technologies, including binoculars



Stars: Old Age, Death, and New Life Page 431


solar system• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour• demonstrate competence in the use of technologies specific to



universe• components of the universe and solar system• metric system (SI units)• appropriate scale

SKILLS AND ATTITUDES• make accurate measurements using a variety of instruments• use the Internet as a research tool• communicate results• use appropriate types of graphic models to represent a given type of

data• use models to demonstrate how systems operate• acquire and apply scientific and technological knowledge to the benefit





13.4

Time

30–45 min

Key Ideas

A star’s mass determines thestages of its life cycle.

Vocabulary

• main sequence• solar mass• red giant• white dwarf• neutron star• pulsar• black hole


PredictingRecordingEvaluatingCommunicatingCreating Models

Lesson Materials

per group• basketball• tennis ball

Program Resources

BLM 13.4-1Hertzsprung–RussellDiagram

BLM 13.4-2 The Life Cycles ofDifferent Types of Stars

WS 13.4-1 Try This: BlackHoles: Gravity’s RelentlessPull

WS 13.4-2 Stars: Old Age,Death, and New LifeCrossword Puzzle

SM 13.4 Stars: Old Age,Death, and New Life


Stars• A star is a ball of gases held

together by gravity. The inward forceof gravity tries to collapse the starand the outward pressure of itsgases and escaping radiation causethe star to expand. For the bulk ofthe star’s lifetime, these forces arein balance and the star is found onthe main sequence of theHertzsprung–Russell (H-R) diagram.Prior to its time as a main sequencestar, the star is contracting and it isneither hot enough nor dense

enough for nuclear fusion reactionsto begin. After its main sequencetime, most of its nuclear fuel hasbeen exhausted. It switches to arange of less efficient nuclearreactions to create internal heatbefore it collapses. At that point, itcan no longer create enough heat tosupport itself against its own gravity.

• The balancing act betweenexpansion and collapse is verydelicate. If the forces did notbalance, the star would collapse orexpand. The duration of this effect is

SCIENCE BACKGROUND

TEACHING NOTES

Getting Started

• Possible Misconceptions– Identify: Students may think that all stars are like our Sun in size

and brightness.– Clarify: Use the H-R diagram on Student Book page 431, and

point out that Betelgeuse, as a red supergiant, is 500 to 800 times

1


called the “free-fall timescale,” saidto be about 2000 seconds for a starlike our Sun. We know that thedelicate balance is maintained to ahigh degree because the Sun hasbeen pretty much stable over the lifespan of Earth.

• The star’s nuclear reactions during itsmain sequence time are the fusionreactions that convert hydrogennuclei (protons) into helium nuclei.These reactions need very hightemperatures (above 10 � 106 °C)and densities (above 10 000 g/cc).The balance between temperatureand density determines how long astar stays on the main sequence.Higher-mass stars with higherinternal temperatures and densitiesuse up their fuel faster than lower-mass stars. So how long a star stayson the main sequence is a functionof its mass.

Hertzsprung–Russell Diagram• A handy way to compare stars is by

observing their luminosity and theircolour. When these two variables areplotted on the H-R diagram, mainsequence stars occupy a narrowband within the diagram. Ultimately,where a star falls on the H-Rdiagram depends on its mass.

• A star’s mass, therefore, determinesnot only its position in the mainsequence of the H-R diagram butalso how long it stays there.

After the Main Sequence• Most stars fuse hydrogen into

helium until there is not enoughhydrogen left in the core to providethe outflow of energy that balancesthe star against its own gravity. Thecore contracts until it is hot enoughfor helium fusion to occur and createcarbon. The hydrogen in the outer

layers continues to fuse to helium,but the star has to expand toconserve energy. This makes thestar look brighter and cooler. It isnow a red giant. It loses many of itsouter layers, which are blown awayby the radiation from the interior. Asits fuel is consumed, the red giantcollapses under its own gravity andbecome a white dwarf.

• Stars with greater than 10 solarmasses are relatively rare, but theirlives end in a cataclysmic fashion.Their main sequence time ends muchas the lower mass stars’, and theybecome cooler and brighter redsupergiants. Carbon fusion occurs atthe core and complex chemicalreactions, plus temperatures of 1 � 108 °C to 6 � 108 °C, result in acore of iron. All the way up to theformation of iron, the addition of extranuclei releases energy, and the starmaintains its “balance.” Once iron isformed, it takes energy to add nucleiand the nuclear fusion reactions stop.The core’s gravity causes the star tocontract very rapidly. Protons andelectrons fuse to become neutronsand the energy release blows awaythe outer part of the star in asupernova. This is when all theelements heavier than iron form. Leftbehind is a neutron star or pulsar.

• In the early universe, there were noelements heavier than helium. Thefirst stars were mostly just hydrogenand helium. There was no oxygen,nitrogen, iron, or any of the otherelements necessary for life. Asnoted above, the heavier elementswere formed later in more massivestars and were then spreadthroughout space by supernovas. If you think about it, we are made ofelements that were processed atleast once inside of a star.

Related Resources








Stephen Hawking’sUniverse (VHS)

An Introduction toAstronomy, Vol. 4, 5, 6, 7,8 (VHS)






– Module 2: The Sun andStars

– Module 6: The MilkyWay and Beyond

– Life of a Star applet

NOVA videos– Nature’s Most Bizarre

Creature– Tracking the Monster

the size of the Sun and varies in luminosity from 8000 to 14 000 times that of our Sun. However, it is 430 light years away,which explains why we do not see it as bigger or brighter. Sirius,the brightest star in the sky, is only 23 times as luminous as theSun but is closer at only 8.6 light years.

– Ask What They Think Now: This comparison should be clearenough, but ask students to explain how Polaris and ProximaCentauri would compare to our Sun.

• The quote from Carl Sagan that “We are made of star stuff ” or theNASA elaboration of “We are made up of material that has beenprocessed at least once inside stars” can be used to trigger discussion.Ask students to comment on the statement, “We are made of starstuff.” Lead them with questions about what stars are made of: ask,What happens as stars get older? Let this concept be a focus fromwhich you can determine what they already understand.

Guide the Learning

• Use the Reading and Thinking Strategies of sketching andchecking understanding when reading this section.

• Use BLM 13.4-1 Hertzsprung–Russell Diagram to help studentsunderstand the H-R diagram. – Begin with solar luminosity on the left side. Point out that

luminosity values increase toward the top of the image. Thus, thebrightest stars will be near the top of the diagram.

– On the right, absolute magnitude increases from the bottom to thetop of the image, even though the negative value is at the top ofthe diagram. A negative value for absolute magnitude indicatesextreme brightness. The Sun is the standard at a luminosity of 1and an absolute magnitude of +5. These scales were worked outindependently of each other and, therefore, seem to becumbersome and counterintuitive.

– Surface temperature is hottest on the left and decreases to theright. As a result, tiny red dwarfs are cool and dim. The mainsequence line is the home of most stars while they burn theirhydrogen fuel. Their mass determines their temperature, absolutemagnitude, and luminosity, and, therefore, their position on the H-R diagram and what they will become when most of theirhydrogen fuel is gone.

• Inform students that stars do not move along the main sequenceband as they age. While a star is on the main sequence, it is burninghydrogen and some helium. When most of its hydrogen is gone, itsenergy production changes and it becomes one of the giant stars,depending on its mass.

• Use BLM 13.4-2 The Life Cycles of Different Types of Stars to helpsummarize the stages a star passes through depending upon its mass.This visual will help students envision the life histories of stars.

2



Have students use theInternet and other sourcesto collect information onname, size, and distancefrom Earth of other starsin our universe. Challengethem to use a computer-based spreadsheet/graphing program tocalculate and graph howlong it takes light fromthese distant stars toreach Earth.

• Point out the white dwarf star in each of the nebulas in Figure 3 onStudent Book page 433. They illuminate much of the materialpreviously cast off when the star was a red giant.

• Point out that the existence of a neutron star or a black hole isprimarily based on the differences in the initial mass.

• Have students perform Try This: Modelling a Supernova Explosionand Try This: Black Holes: Gravity’s Relentless Pull.


TRY THIS: MODELLING A SUPERNOVA EXPLOSION

Purpose

• Demonstrate the mechanism that powers a supernova.

Notes

• Set up in a clear area so the rebounding balls do not break anything.• You may want to vary the height from which the balls are dropped to give the

impression of the energy in the collapse of small- and large-mass stars.

Suggested Answers

A. Using a metre stick, the height of rebound for each ball can be quantified.

B. When the balls hit the floor together, the tennis ball bounces much higher.

C. The energy comes from the combined reaction of the elasticity of the two balls.

D. This model is like a supernova in that the outer layers, represented by thetennis ball, get blown away.

E. Unlike a supernova, the balls are not to scale for the star’s anatomy, the energyderives from elastic rebound of the walls of the balls and not from the centreoutward, and this represents only two layers, whereas we know that starsconsist of several layers.

TRY THIS: BLACK HOLES: GRAVITY’S RELENTLESS PULL

Purpose

• Through the simulation, students will gain an understanding of the relativedistances to objects in deep space and learn the properties of two differentblack holes.

Notes

• Take your class to a computer lab for this activity.• Students can use WS 13.4-1 Try This: Black Holes: Gravity’s Relentless Pull to

record their answers.• You may want to collect student reports on the experiment they wrote up.

Suggested Answers

2. 1. M33 (extragalactic binaries), distance 2.1 million light years, has stellar-mass black hole.

2. Andromeda (spiral galaxy), 2.5 million light years, has a supermassive black hole.

3. Cygnus A (elliptical galaxy), 730 million light years, has a supermassive black hole.

4. Cygnus X-1, 8100 light years, has a stellar-mass black hole.

5. Milky Way Centre, 28 000 light years, has a supermassive black hole.

6. 3C273 (quasar), 2.5 billion light years, has a supermassive black hole.

Other items that students will find when they search the sky include the Sun, NGC 7027 (a planetary nebula), Albireo (binary star), Saturn, the Moon, and Betelgeuse.

At Home

Ask students to explainthe quote “we are madeof star stuff” to an adult.


• Ask students to create a flow chart that summarizes the possiblestages that stars of different masses could pass through. Ensure thatstudents address the fact that the fate of a star depends on its mass.

• Have students complete WS 13.4-2 Stars: Old Age, Death, and NewLife Crossword Puzzle as a review of the vocabulary in this section.


3


3. Cygnus X-1

Velocity to escape Earth’s gravity: 25 000 mph or 40 234 km/h

Energy boost to reach Pluto: 100 billion times more

Time to reach Pluto: 19 s

Current percentage of light speed: 99.9995 %

Time to reach Cygnus X-1: 8.2 years

Next energy boost: 10 million times

Time to reach Cygnus X-1: 26 s

Andromeda

Note: first four are same as Cygnus X-1

Time to reach edge of galaxy: 33 years

Energy boost to reach edge of galaxy: 100 million times more

Time to reach edge of galaxy: 10 s

Energy boost to reach Andromeda: 100 times more

Time to reach Andromeda: 8 s

4. Cygnus X-1 properties: binary system; the black hole pulls the gas from thestar around it.

Accretion disk properties: gases falling toward the black hole form a rotatingdisk. The gases heat up millions of degrees due to friction. The disk shines inX-rays.

Jet properties: some material is ejected at high speeds because of the energyin the accretion disk. The jet shines radio waves.

Black hole properties: no light can escape; the area around the event horizonlooks black; all of the mass is concentrated in the centre.

Andromeda properties: normal spiral galaxy with supermassive black hole 30 million times heavier than the Sun.

Accretion disk: very little gas goes into the black hole; therefore, little energyis generated. This black hole is not a good source of radio waves or X-rays.

Black hole has the same properties as Cygnus X-1. There is no jet from theblack hole in Andromeda.

5. The black hole’s gravity distorts the view of stars by bending light. You can seethe same stars a number of times on opposite sides of the black hole.

Einstein’s cross is four points of light that are actually coming from the samequasar. The light from the quasar gets bent by another galaxy in front of thequasar.

6. Student answers will vary depending on the experiment they choose.



1. Along the main sequence, stars are arranged by their masses while theirhydrogen is being consumed. This is the “main” part of their life. Massdetermines their surface temperature, absolute magnitude, and luminosity.Our Sun is one solar mass. Cooler, reddish stars are at the lower right, andvery bright, hot, bluish stars are at the upper left.

2. Red giants have an absolute magnitude of about +5 to –2; they are cool starswith a surface temperature of about 3000 °C and their luminosities rangebetween 1 and 103 (they are large, with cool surfaces, but relatively bright).

3. Today we understand stars are in a fixed position on the main sequence untiltheir hydrogen is burned up. Then, they move off the main sequence and,depending on their mass, become a red giant or supergiant, and later a whitedwarf.

4. A solar mass of 1 is the mass of our Sun. It is the standard with which allother stars are compared.

5. The gravity at the core increases as heavier, denser elements (helium throughto carbon and oxygen) form there.

6. (a) The pump gets hot because the compression of the gas increases the speed of its particles and increases the frequency of collisions with the pump wall. We feel the collisions as heat.

(b) As the helium at the core is compressed, the frequency of particle collisions increases and the heat of the core increases.

7. A red giant cools because the expanding outer layers move farther away fromthe heat source (the core), and their heat energy is not renewed fast enoughfrom the core.

8. The heaviest elements that a red giant can form are carbon and oxygen.

9. Fusion of hydrogen, helium, and atoms of other newly formed elements willlead to the formation of carbon and oxygen.

10.

He

H

He

inward pullof gravity

outwardenergy flow

H

main sequence star; gravity and energy flow balanced; helium core forming

Hydrogen fusion slows and outward flow of energy and pressure is reduced. Gravity increases and helium core contracts and heats up.

helium core

hydrogenburningshell

The hot helium core restarts hydrogen fusion in the hydrogen burning shell and the star’s outer layers expand and cool.

carbonandoxygen

Red Giant

hydrogenburningshell

heliumburningshell

Continued fusion of its remaining hydrogen increases the helium core and raises its temperature to the point (1 � 108 °C) when helium fusion begins. Helium fusion produces a core of carbon and oxygen.


11. Red giants send up streams of gas and dust into space and lose mass. A starwith 10 solar masses initially will lose enough mass to fall below 1.4 solarmasses and become a white dwarf.

12. A white dwarf becomes a black dwarf when the last of its energy has beengiven off into space. The white dwarf cools and dims until its light goes out.

13. Within the Spirograph nebula are concentrations of matter (the clumpiness)that could lead to the formation of new stars.

14. (a) At greater than 10 solar masses, stars will become either neutron stars or black holes.

(b) Neutron stars have initial solar masses of 10 to 50. Black holes have initial solar masses of over 50.

15. Elements heavier than iron include anything with a higher atomic number thaniron on the Periodic Table. The elements heavier than iron form when starsover 10 solar masses explode as supernovas.

16. (a) Neutron stars form from a supernova when the initial solar mass is between 10 and 50. They are extremely dense (a volume of 250 mL would have a mass of millions of kilograms).

(b) A pulsar is a neutron star that sends out light and a beam of high-energy radio waves. Pulsars also rotate while giving off energy.

17. At over 50 solar masses, the supernovas will form elements heavier thannickel and iron. If the supernova remnants are greater than 4 solar masses,then the core will collapse on itself and develop a gravitational pull that drawsin all neighbouring matter and prevents the escape of light.

18. The evidence is considered indirect because we cannot “see” a black hole;we rely on observing what happens around it to gain insight into its properties.

19. The sequence is hydrogen, nebula, formation of clumps of matter, mainsequence star, formation of helium, red giant, formation of carbon, whitedwarf.

20. Iron is not an efficient element with which to continue the fusion process. It will not “burn.” At the temperatures and pressures found in stars of up to10 solar masses, there is not enough heat or pressure to fuse iron further. Itcannot be used as a fuel.

Check Understanding

• Read the section heading and the first two paragraphs on StudentBook page 431 with students.

• Have students look at Figure 1 to note it is a Hertzsprung–Russelldiagram showing the main sequence distribution of stars. Ask whyinformation presented this way is helpful to astronomers (organizes astar’s history; simplifies and makes it easier to share information).

• Read the third paragraph with students, stopping at the end ofsentences where words in boldface appear. Ask students to explain themeaning of the words, using Figure 1 and information from the text.

• Conclude by having students check their understanding of Figure 1 byreading the Learning Tip on page 431 and answering the questionsthere.

Sketch

• Direct students to close their Student Books. Tell them you will bereading about how the Sun will eventually become a red giant.

• Read the first two paragraphs in the subsection Red Giant to a WhiteDwarf on page 432 out loud. Ask students to make quick sketches of

Reading and

Thinking Strategies

the images that come to mind as they listen. Read the paragraphsagain so that students can complete and label their sketches.

• Have students open their books and compare their drawings withFigure 2 on page 432. Ask if sketching helps them to “see” the changesto the Sun as it becomes a red giant.

• Conclude by reading the last two paragraphs on page 432 and the firstparagraph on the top of page 433 with students.


ESL

• Ask students to add new vocabulary words to their visual dictionaryand to also include the word luminosity.

• For the Learning Tip suggestion on Student Book page 432, pair ESLstudents with an English-competent partner.

Extra Challenge

• Ask students to learn more about Tom Bolton and the first confirmedblack hole, Cygnus X-1. Students could report on his discoveries in acreative format, such as a newspaper article or a news report.

• Challenge students to use imported computer graphics and text boxesto create an animation or PowerPoint presentation modelling andexplaining the life cycle of a star.



Evidence that students can• relate mass to different stages in the life cycle of stars• identify star clusters/types according to their distinguishing characteristics• interpret the information on the H-R diagram and give the properties of a star found

anywhere on the diagram• describe the formation of the solar system and its components (the life cycle of stars)• describe the qualities of the scientifically literate person (separate fundamental concepts

from the irrelevant)• demonstrate skills of collaboration and co-operation• proficiently use the Internet as a research tool



Galaxies and Our Home: The Milky Way 7


solar system• demonstrate scientific literacy

KNOWLEDGE• components of the universe and solar system• metric system (SI units)• appropriate scale

SKILLS AND ATTITUDES• communicate results• acquire and apply scientific and technological knowledge to the benefit





13.5

Time

30–45 min

Key Ideas

Galaxies, star clusters, andnebulas can be distinguishedby their structures andcharacteristics.

Vocabulary

• elliptical galaxies• spiral galaxies• barred-spiral galaxies• irregular galaxies• quasars• globular clusters• open clusters

Program Resources

BLM 13.5-1 Activity: Model aSpiral Galaxy

BLM 13.5-2 The Local GroupWS 13.5-1 Galaxies and the

Milky Way Word SearchBLM 13.5-3 Concept Map for

Check Your UnderstandingQuestion 9

BLM 13.5-4 The HubbleTuning Fork

SM 13.5 Galaxies and OurHome: The Milky Way


The Local Group• The Local Group is the name of the

small cluster of galaxies to which theMilky Way belongs. Depending onthe source, the Local Group is saidto be between 2.5 to over 6 millionlight years across and houses from24 to 40 galaxies and small systems.Its three largest galaxies, the MilkyWay, Andromeda, and the Pinwheel,will likely pull the whole grouptogether to form a large cluster ofgalaxies in the distant future. Mostmembers of the Local Group aresmall and faint and are typicallyirregular galaxies (Magellanic clouds)and dwarf ellipticals. The latter areso small and faint that they are hardto find beyond Andromeda, whichmakes the exact size of the LocalGroup hard to establish.

Classifying Galaxies• In 1926, Edwin Hubble proposed a

system with which to classify themany complex galaxies that werebeing identified. His system, theHubble Tuning Fork, is nowconsidered too simple, but its basictenets still hold.

• Hubble initially divided the galaxiesinto two basic types: spirals andellipticals. He numbered theellipticals from 0 to 7 to characterizehow elliptical they were. E0 isvirtually round, while E7 is veryelliptical. Eventually, this wasexpanded to include barred spiraland irregular galaxies.

• Hubble labelled the spirals from “a”to “c” to denote how compactlytheir arms were wound, with Sa’sspirals tightly wound and Sc’sloosely wound. He also noted thatthe hub, or central bulges, increasein size the more tightly the spiralarms are wound.

• An S0 designation was added yearsafter Hubble’s initial work to identifythe “lenticular” galaxies located in atransition zone between theellipticals and spirals.

• Initially, Hubble and others thoughtthe system represented anevolutionary sequence in thedevelopment of the galaxies, withgalaxies progressing from the left tothe right of the tuning fork. On theleft side of the fork are the elliptical

SCIENCE BACKGROUND

TEACHING NOTES

Getting Started

• Possible Misconceptions– Identify: Students may think of galaxies as far more solid structures

than they are.– Clarify: Modern computer simulations have shown that the edges

of galaxies could pass through each other without their starscolliding. If the closeness of galaxies could be likened to billiardballs on a table, their stars would be more like grains of sand tensof kilometres apart. Thus, the galaxies do interact, but collisionsbetween their stars are rare.

– Ask What They Think Now: The Milky Way and Andromedagalaxies are closing in on one another at 500 000 km/h. In 3 billion years (even before our Sun becomes a red giant), thosegalaxies will collide. Ask, What will likely happen when the galaxiescollide? Students should respond that the galaxies will pass througheach other. However, more likely will be the formation of onelarger galaxy.

• Have students do BLM 13.5-1 Activity: Model a Spiral Galaxy.

Guide the Learning

• Use the Reading and Thinking Strategies of interpreting visualsand graphics, and synthesizing and making comparisons whenreading this section.

• Discuss what the Milky Way looks like in the sky. The Milky Way gotits name because astronomers believed that it resembled milk splashedacross the sky. If the Milky Way is a spiral galaxy, why do we see it aswe do? (As we look into space, we can only see part of one arm of thespiral. Refer to page 439, Figure 8, in the Student Book.)

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galaxies (starting at E0). The forkthen opens up, with the spiralgalaxies on the top of the fork andthe barred spiral galaxies on thebottom. Today, we know that galaxyevolution is far more complex thanHubble imagined; the system isretained only for its nomenclature.

• The irregular galaxies are a thirdclass of galaxy and are not includedin the tuning fork.

The Galaxy’s Centre• The massive black hole at the centre

of the Milky Way is the radio sourceknown as Sagittarius A*(pronounced A star). Sagittarius A*

lies within a large region at thecentre of the galaxy calledSagittarius A.

• In 2002, a star designated S2 wasfound orbiting Sagittarius A* at adistance of three times theSun–Pluto distance, or 17 lighthours. It moves at 5000 km/s, or 200times the speed of Earth, and orbitsSagittarius A* in only 15.2 years.

• The star S2 has an estimated mass inexcess of 2 million solar masses.Rainer Schödel of the Max-PlanckInstitute claims that only a massiveblack hole would be capable of thegravitational pull required to accelerateS2 to the observed orbital speed.

Related Resources












CSA Educators’Resources: Astronomy

– Module 6: The MilkyWay and Beyond

• Use BLM 13.5-2 The Local Group to explain our place in space. TheLocal Group’s 24 closest galaxies extend only 2.4 million light yearsfrom the Milky Way—it is a small cluster. The closest neighbouringgiant cluster is the Virgo cluster in the direction of the constellationVirgo. It contains over 2000 galaxies and is 9 million light yearsacross. The Virgo cluster is 60 million light years away from us withlittle matter between it and the Local Group.

• Attempt to display as many photos/posters of galaxies as possible. Be sure to point out to students the different galaxy shapes.

• Using Figure 8, point out the number of younger, usually blue starsin the arms. Contrast that with the predominantly yellowish stars inthe core. The galactic arms are full of interstellar gas and dust.Slower rotating “density waves” compress the dust and gas and causethe formation of hot, young, blue stars. The galactic core consists ofolder and cooler reddish stars.

• The black hole Sagittarius A* is pinpointed by two yellow arrows inFigure 9. The yellow horizontal band at the bottom of the pictureshows a distance of 1 light year. Contrast the number of stars in thisimage with the fact that our nearest stars are Proxima and AlphaCentauri at just over 4 light years away. The galactic core of the MilkyWay is very crowded. What draws all those stars there? (gravity)


• By the end of this section, students should be able to answerquestions such as– What was the Big Bang?– What is a red shift?– How old and how big is the universe?– How do we measure distance in space?– How do black holes form?– What are galaxies?

You could ask these questions and others of your choosing orally, orin a game format.

• Assign WS 13.5-1 Galaxies and the Milky Way Word Search to reviewthe terms associated with the Milky Way and galaxies.

• Assign the Check Your Understanding questions. You may want tohand out BLM 13.5-3 Concept Map for Check Your UnderstandingQuestion 9 to help students complete the question.

3


At Home

Ask students to make alist of the astronomicalnames found in householditems, company names,automobile names, and soon. For instance, theJapanese name for thePleiades (also known asthe Seven Sisters) is“Subaru,” and the starcluster is depicted on theautomaker’s logo. Askstudents to bring their liststo class for comparison.


Students can examineimages of many differentgalaxies and star clustersusing the Internet orsoftware such as StarryNight Deluxe. Studentscan look for objects suchas• the globular cluster

Pegasus (M15)• Andromeda (M31)• the Beehive open cluster

(M44)• the Whirlpool galaxy

(M51)• the barred spiral in Leo

(M95)Students could use theimages found, along withkey unit vocabulary andconcepts, to createposters. Encouragestudents to locate themost current descriptionsand images available. Thiscould lead into adiscussion on thereliability of informationsources and howincreases in technologyincrease ourunderstanding of theworld and universe.


1. The Local Group includes more than 24 of the closest galaxies and smallersystems to a distance of 2.5 � 106 light years from the Milky Way.

2. Elliptical galaxies are thought to be older because they have little interstellarmatter and rarely form new stars.


3. A spiral galaxy’s arms spin about a single point. A barred spiral has a bar orband of stars extending out through its centre on either side and a spiral armoff each end. See Figures 4 and 5 on Student Book page 438 for what studentdiagrams should look like.

4. Astronomers believe that irregular galaxies are likely the result of collisions ofgalaxies.

5. Stars form within the arms when the pressure waves collide with the gas anddust and compress that nebula-like material into a protostar.

6. (a) 2.6 � 106 solar masses � �21.0so

�

la1r0m

30

asksg

�

� 5.2 � 1036 kg

The mass of Sagittarius A* is 5.2 � 1036 kg.

(b) 1.4 � 106 km � 15

� 2.1 � 107 km

The diameter of Sagittarius A* is 2.1 � 107 km.

7. (a) On the innermost arm of the Milky Way, we would see a hemispherical wall of stars.

(b) Inside the core or hub of the galaxy, the entire sky would be aglow with densely packed stars.

8. The black holes of two colliding galaxies could fuse into one to produce asupermassive black hole, which would likely emit a quasar. With twice asmuch material around it, the supermassive black hole would continue to growby consuming other galaxies.

9.

10. Hot stars are young stars and emit far more energy at a higher wavelength,which is the blue/violet end of the spectrum. Red stars are older stars, arerather cool, and do not emit such high frequency energy, placing them in thered end of the spectrum.

11. There would not likely be life on a planet in the galactic core. The heat andradiation in the core would be too excessive for life as we understand it.

12. Quasars emit powerful radio waves.

13. A galaxy cluster is a group of galaxies gathered around an enormous blackhole (tens of millions of solar masses). The cluster is held together by intensegravity.

partofthe

homeof

is a

number of arms

diameter

distancefrom hub

orbits

called

it is asource of

of

anothergalaxy

a smallersystem

consistsof

has adiameter of

has a

every 2.0 to2.3 � 108 years spiral galaxy

200 billion stars 4–6 spiral arms

1 � 105 l.y.

the local groupSun

27 000 l.y. 2.5 � 106 l.y.

X-rays andradio waves

supermassive blackhole of 2 � 106

solar masses

central black hole

Sagittarius A*large and small

Magellanic clouds

Andromeda

Milky Way 24 galaxies andsmaller systems


14. Table 1 Comparison of Star Clusters

Cluster Number ofstars

Age ofstars

Cluster shapeand size

Location ingalaxy

Globular thousands tomillions

all very old spherical, 10–30light years indiameter

near galacticcentre

Open a fewhundred

young stars spread out, 30 light years indiameter

only in thegalactic disc

Interpret Visuals and Graphics

• Read the first paragraph on Student Book page 438 with students. • Have pairs of students describe to each other the characteristics of the

different galaxy types, using Figures 3 to 6 in their explanations.• Encourage critical thinking by asking questions such as

– Why do you think spiral galaxies were the first to be discovered?– How do you think spiral galaxies were named?– What is the difference between spiral and barred spiral galaxies? – Why do you think elliptical galaxies are thought to be older than spiral

galaxies?

Synthesize/Make Comparisons

• Have students read the subsection Star Clusters on page 440 to answerthe question, How are globular and open star clusters different?

• Point out that one way to describe the different star clusters is to use acomparison matrix. If students are unfamiliar with this, have themlook at page 545 in the Skills Handbook.

• Have students create a four-column matrix (Term, Number and Age,Shape and Size, Location in Galaxy) in their notebooks. As they readthe subsection, have them complete the matrix.

• Ask students if creating a matrix helps them organize information.

Reading and

Thinking Strategies

ESL/Extra Support

• Ask students to add vocabulary words to their visual dictionary.• Hand out a copy of BLM 13.5-4 The Hubble Tuning Fork and have

students label each galaxy shape as part of their notes.

Extra Challenge

• Have students search for the work on the globular cluster NGC 6397and make a brief report on their findings.

• Ask students to research and report on the work of Helen Sawyer Hogg.



Evidence that students can• identify galaxies and star clusters/types according to their distinguishing characteristics • describe the qualities of the scientifically literate person (ability to separate fundamental

concepts from the irrelevant)


Investigation: Hunting for Galaxies Page 452




solar system• represent and interpret information in graphic form• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour


universe• components of the universe and solar system

SKILLS AND ATTITUDES• illustrate astronomical phenomena• communicate results• use bar graphs, line graphs, pie charts, tables, and diagrams to extract

and convey information• apply given criteria for evaluating evidence and sources of information




13D

Time

45–60 min

Key Ideas


Galaxies, star clusters, andnebulas can be distinguishedby their structures andcharacteristics.


PredictingConductingRecordingAnalyzingEvaluatingCommunicating

Lesson Materials

per student• galaxy shapes handout

(BLM 13D-2 Galaxy Shapes)• Hubble galaxy classification

handout (BLM 13D-3 HubbleGalaxy Classification)

Program Resources

Investigation BLM 13DHunting for Galaxies

BLM 13D-1 Hubble Deep FieldGalaxies

BLM 13D-2 Galaxy Shapes BLM 13D-3 Hubble Galaxy

Classification Rubric 18: Conduct an

InvestigationRubric 19: Conduct an

Investigation—Self-Assessment

SSP Rubrics 5, 6, 9, 10, 11, 12,13, 14, 15, 16, 17, 18


Classifying Galaxies• Galaxies, once known as spiral

nebulas, are cosmic bodies thatcontain hundreds of billions of stars,and there are billions (about 1012) ofthem in the universe.

• For further information on theshapes of galaxies, see the ScienceBackground information in Section13.5.

SCIENCE BACKGROUND

INVESTIGATION NOTES

• The Hubble Deep Field images can also be found in BLM 13D-1Hubble Deep Field Galaxies or viewed through the links on the NelsonScience website. The images on the BLM are negative images, whichmay make seeing the shapes of the galaxies easier. The larger theseimages can be viewed, the easier the students’ task becomes. However,enlarged images may require scrolling on a monitor or several pages ofprintout to see the whole image.

• As students use BLM 13D-2 Galaxy Shapes, explain that they must beable to precisely describe the characteristics that differentiate onegalaxy shape from another.

• As students create a diagram that reflects their classification system,suggest that their diagram could attempt to show a relationship orconnection between the galaxies.

Question

• Galaxies appear in all shapes and sizes. However, they are all galaxies—collections of stars. This commonality leads to the question asked.

• After reading Section 13.5, students will likely answer yes to thequestion in the Investigation. Students are aware of the various shapesof galaxies.

Prediction

• Most galaxies seem to be variations on a round shape.

• Students may predict that it could be possible to group or classifygalaxies based on their shape. Students may group galaxies from roundto oval (or spiral).

Experimental Design

• This is not an investigation in which variables are being manipulatedand controlled. It is an investigation for the purpose of demonstratingthe use of data collected from the Hubble Space Telescope, and thenapplying that data to our understanding of the universe.

Materials

• Do not distribute BLM 13D-3 Hubble Galaxy Classification until theend of the Investigation. It is required for the Evaluation questionsand will defeat the purpose of the activity if given out early.

Procedure

• The difference between a star and a galaxy is in number. Stars aresingle; galaxies are billions of stars. In the diagrams, however, stars arethe single points of light with, usually, four rays emanating from them.

• A student explanation of a classification system may focus on the twoprimary types: spirals and ellipticals. Students may recognize a possiblesimilarity between the tightest or densest spirals and the moreelongated ellipticals. The irregular galaxies do not clearly fit the systembut could be recognized as colliding spiral galaxies.

• Students may also recognize barred spirals as a variant on the spirals.

• Students should keep a count of the galaxy types they find. A simpletable listing their characteristics and a place to register a count mayhelp some students organize their thoughts. A sample table follows.


Ellipticalgalaxies

Spiral galaxies Barred spiralgalaxies

Irregulargalaxies


Students could searchvarious astronomy sitesand create their owntuning fork diagram usinggalaxy images they find.

At Home

Students could beencouraged to take theHubble tuning forkdiagram home and explainto an adult what itrepresents.

• Students’ labelled diagrams should contain at least three branches—one for each of the ellipticals, barred spirals, and spirals. The irregulargalaxies could be a separate entry to the main diagram. If students donot recreate a tuning fork-style diagram, they may create a Venndiagram.

Analysis

(a) Some galaxies are physically larger than others, but in these imagesthe smaller ones are usually farther away.

(b) Yes, galaxies can be classified by their physical characteristics. Shapeseems to be a major factor, as does the degree of winding for thespirals.

(c) Students may respond that not all galaxies fit neatly into Hubble’ssystem. Originally, the classification did not include the irregulargalaxies.

(d) A student conclusion could be the following: galaxies may beclassified by their shapes and degree and style of spiralling.

Evaluation

(e) A comparison with the Hubble tuning fork diagram may reveal astrong similarity with student work.


ESL

• Ask students to review Student Book page 438, Classifying Galaxies,before they begin this investigation. Have students pay particularattention to the captions with the figures.

Extra Challenge

• Ask students to note that Hubble’s original classification system wasmissing one of the shapes used today. Ask students to determine whichgalaxy shape has been added (S0) and why it was added (it is theintermediate between the elliptical, spiral, and barred spiral galaxies atthe crux of the fork).



Evidence that students can• identify and describe a range of instruments that are used in astronomy (Hubble Deep Field

and Hubble Ultra Deep Field)• identify galaxies according to their distinguishing characteristics• use the correct scientific terminology in their descriptions of galaxies and their shapes•extract information from diagrams

• identify the main points in a science-related illustration• describe and demonstrate skills of collaboration and co-operation



Dark Energy and the Expansion of the Universe Page 442


solar system• demonstrate scientific literacy• demonstrate ethical, responsible, co-operative behaviour

KNOWLEDGE• components of the universe and solar system• metric system (SI units)• appropriate scale

SKILLS AND ATTITUDES• communicate results• use appropriate types of graphic models to represent a given type of

data• acquire and apply scientific and technological knowledge to the benefit



information

13.6

Time

30–45 min

Key Ideas


Vocabulary

• dark matter• dark energy


ConductingRecordingAnalyzingEvaluatingCommunicating

Program Resources

WS 13.6-1 Dark Energy andExpansion of the UniverseCrossword Puzzle

SM 13.6 Dark Energy and theExpansion of the Universe


Dark Matter• For decades, astronomers were

aware of a problem that they called“missing mass.” Galaxy clusterswere not massive enough to keepthemselves from flying apart—theirgravitational pull for their visiblematter was too small. To confirmthis, astronomers began to improveon estimates of the number of starsin a galaxy. On average, galaxyclusters were found to have only �3

10�

of the material needed to keep thecluster together.

• This missing mass, or dark matter,had to exist both within galaxies andbetween them. Exactly what thismass happens to be is unknown atthis time. Several explanations havebeen offered: black holes, neutronstars, brown dwarfs, white dwarfs,stray planets, asteroids, comets, andthinly distributed gas betweengalaxies. All have failed to comeanywhere close.

Dark Energy• In 1998, red-shift measurements on

type Ia supernovas in remotegalaxies demonstrated that theseexploding stars should be dimmerthan they were. Overall, themeasurements seemed to indicatethat the expansion of the universe atthese distances was increasing, notslowing down as all previoustheories indicated. Somethingliterally seemed to be pushing thegalaxies apart. This force has beencalled dark energy.

• It has been determined that theeffects of dark energy increase withdistance and that billions of lightyears away is where dark energyfully exerts its effects.

Raisin Bread Model of Expansion• The Big Bang model developed

naturally from Einstein’s GeneralTheory of Relativity as applied to ahomogeneous universe.

SCIENCE BACKGROUND

TEACHING NOTES

Getting Started

• Possible Misconceptions– Identify: Students may think that dark matter and antimatter are

the same thing.– Clarify: Explain to students that antimatter is matter with its

electric charge reversed (normal matter is discussed in Section 7.1).For example, protons are positive while antiprotons are negative.Thus, antimatter and matter cannot exist together. Dark matter,however, is some undiscovered form of normal matter that behaveslike normal matter. It has mass, and it clusters in some places andnot others, like normal matter.

– Ask What They Think Now: Astronomers have concluded that darkmatter exists in the outer fringes of a galaxy. Now ask, In additionto holding a galaxy together, how does the existence of dark matter inthe outer fringes of a galaxy demonstrate that dark matter is notantimatter? (A possible answer could be the following: we do notsee lots of random explosions in the outer fringes of galaxies,which we would if dark matter were antimatter.)

Guide the Learning

• The existence of something we cannot see is often difficult forstudents to understand. Ask students, How do you know the wind isblowing? Most students should be able to explain that they see cloudsmoving, a flag flying, or the leaves on a tree fluttering. Scientists canalso detect the effects of an invisible phenomenon. This principle isfundamental to many branches of science wherein theories aredeveloped to explain what we see happen in the absence of a direct,visible cause.

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1


Einstein developed a cosmologicalconstant to allow for a constantuniverse. When Hubble found anexpanding universe wherein galaxieswere moving away from us with aspeed that was proportional to theirdistance from us, Einstein removedthe cosmological constant. Universalexpansion with distant galaxiesmoving away faster was whatGeneral Relativity predicted.

• One part of Hubble’s expansion lawindicates that the speed of recessionis proportional to distance. That ideacan be displayed using the raisinbread model.

• If every portion of the bread expandsby the same amount in a given

period of time, then the raisins wouldmove away from each other, asHubble predicted. That is, araisin/galaxy close to us would movevery little, but a raisin/galaxy somedistance away would move farther inrelative terms. This same effectwould be seen from any raisin/galaxy.The Hubble law is exactly whatwould be expected from ahomogeneous expanding universe aspredicted by the Big Bang theory.Therefore, no raisin/galaxy holds thatspecial, centre-of-the-universeposition. This analogy worksthroughout the portion of breadunless the raisin/galaxy is near theedge of the portion.

Related Resources

Dickinson, Terence. TheUniverse and Beyond. 4th ed. Richmond Hill,ON: Firefly Books, 2004.





Understanding theUniverse: What's New inAstronomy (VHS)


Stephen Hawking'sUniverse (VHS)




• This is a very new branch of cosmology and is still in development.It is highly recommended that you stay up-to-date using the manysites related to cosmology—Hubble, NASA, GSFC, and so on.

• Use the Reading and Thinking Strategy of paraphrasing whenreading this section.

• Have students perform Try This: Testing the Big Bang Model.


TRY THIS: TESTING THE BIG BANG MODEL

Purpose

• Simulate Hubble’s expansion observations and demonstrate that galaxies fartheraway are moving the fastest.

Notes

• As the dough expands, each raisin moves away from each neighbouring raisinby the same amount.

Suggested Answers

A. The warmth represents the energy of the Big Bang.

B. The dough represents space.

C. Raisins are the galaxies.

D. Each raisin would see the others moving away from it. This would seem toplace each raisin/galaxy at the centre of the universe.

E. No local galaxy is at the centre of the universe. The universe is so large that wecannot determine its centre.

F. The greatest expansion away from galaxy A is shown by galaxy D.

G. Galaxies are being carried along with space; otherwise, they too would beexpanding at the same rate.

H. Like the universe,

Shows why we seem to be at the centre of the universe.

Demonstrates that galaxies farthest away are receding fastest.

Space expands, carrying galaxies with it.

Unlike the universe,

The model has an edge to it; the universe does not.

The model does not account for dark energy’s effect of increasing the expansion rate in the outer portion of the loaf.

Raisin Original distance(cm)

Final distance (cm) Difference(final–original) (cm)

A to B 2 4 2

A to C 4 8 4

A to D 6 12 6

At Home

Ask students to havesomeone help them bakea loaf of bread to whichthey have added a fewraisins. When baked andcut open, they should seethe type of expansion inthe Try This.


• To summarize several important concepts, ask students thefollowing:– What problem did the discovery of dark matter apparently solve?

3

– Where is the missing mass theorized to exist? – What is dark matter? How does dark matter behave? – What 1998 discovery altered the idea that dark matter was going to

allow the universe to slow its expansion and even reverse it? – What force is theorized to be responsible for this increased expansion? – What portion of the universe’s mass and energy exist as dark matter?– Now ask the open-ended question, Is the universe going to continue

to expand forever, or will it eventually reverse its expansion andcollapse in on itself? (In all likelihood, it will continue to expand,unless future discoveries offer new theories.)

• Assign students WS 13.6-1 Dark Energy and the Expansion of theUniverse Crossword Puzzle to review some of the related concepts.




1. (a) The oscillating theory proposed that there would be enough gravitational pull to reverse the expansion of the universe and bring everything back in on itself.

(b) The oscillating theory claims the universe will expand, slow, and then reverse its expansion. The ultimate extension of that idea is that the universe would collapse in on itself and expand in another Big Bang. This theory requires that the universe contain enough mass to cause this slowing and eventual collapse. In the expanding universe theory, there is not enough mass to slow the expansion, and the universe will keep on expanding.

2. The universe is expanding at a rate of 1 � 1012 cubic light years a minute.

3. The force of the Big Bang is causing the expansion.

4. Gravity was supposed to slow down the expansion of the universe.

5. Without enough mass in the galaxies, there would not be enough gravity tohold them together.

6. Dark matter is some as-yet-undiscovered particle that behaves like normalmatter. Dark matter is supposed to add enough mass/gravity to the universe toslow its expansion.

7. Without enough mass to hold galaxies together, the stars would be distributedevenly throughout the sky. There would be no clusters or superclusters ofgalaxies.

8. (a) The number of stars in the outer fringes of galaxies decreases, but the mass does not. Without enough mass in the outer fringes of spiral galaxies, their arms should not rotate as fast as they do.

(b) The outer arms of a galaxy would lag behind in their rotation, and the inner and outer portions of a spiral galaxy may separate from each other.

9. Figure 6 shows the clustering of galaxies (blue), with voids in other locations(white). This indicates areas of stronger gravitational pull caused by darkmatter. The dark matter helps draw the galaxies together.

10. Astronomers discovered that the expansion of the universe is not slowing; infact it seems to be increasing. Dark energy is responsible for this increasingexpansion. It is now thought that the universe will not collapse back on itself;therefore, the oscillating theory had to be abandoned.

11. Dark energy is not an antigravity force, because dark energy increases itseffect with increasing distance, while gravity’s effect lessens with distance.


Many good sites exist thatcan bring students up-to-date or let them seecurrent developmentsabout dark energy. Askstudents for a quicksummary of informationfor the two most recentyears.


12.

We would be found in the visible matter area of the circle graph—0.4 %.

Distribution of matter and energy

dark energy

dark matter

non-visible matter

visible matter

73.0 %

23.0 %

3.6 % 0.4 %

Paraphrase

• Read the subsection Dark Energy on Student Book page 443 with students. • Ask, Why did the discovery of dark energy cause scientists to abandon the

oscillating theory? (They determined that the expansion of the universewas not slowing down but increasing. They use the idea of dark energyto explain the increasing expansion.)

• Conclude by arranging students in pairs to complete the activity in theLearning Tip on Student Book page 443.

Reading and

Thinking Strategies


Evidence that students can• describe the formation of the solar system and its components, and the formation of the

universe• describe dark matter, its location, and its role in the universe• describe dark energy and the role it plays in the expansion of the universe• describe the qualities of the scientifically literate person (recognizing that scientific

knowledge is continually developing and often builds upon previous theories)• describe and demonstrate skills of co-operation and collaboration


ESL

• Ask students to add to their visual dictionary.

Extra Challenge

• Ask students to research the concept of quintessence as it relates tocurrent theories about the expansion of the universe.

• Challenge students to use the Internet and other sources to summarizeand compare Einstein’s General Theory of Relativity and Hubble’sexpansion law. Encourage students to share their reasoning on whichexplanation they think best explains the expansion of the universe.


Unit D: Space Exploration 657NEL

Time

45–60 min


The Chapter Review providesan opportunity for students todemonstrate theirunderstanding of and theirability to apply the key ideas,vocabulary, and skills andprocesses.

Program Resources

BLM 0.0-10 Chapter KeyIdeas

Chapter 13 QuizNelson Science Probe 9

websitewww.science.nelson.com

Chapter 13 Review Chart

• Remind students of the format of the Chapter Review and theinformation it contains.

• Ask students to review the vocabulary by making their own crosswordpuzzles or word scrambles. As an alternative, some students may makevocabulary flash cards or two-column notes.

• Encourage students to describe the pictures to help them recall whatthey learned about the key ideas.

• Remind students to use the vocabulary words in the answers to thereview questions.

• Have students use BLM 0.0-10 Chapter Key Ideas to review the keyideas in the chapter.

• Have students review their Chapter 13 Study Guide Outline notes torecall what they have learned in this chapter.

• Have students complete the Chapter 13 Quiz in the StudentWorkbook to review the vocabulary and concepts in this chapter.

• Encourage students to visit the Quiz Centre and complete the chapterquiz as a self-test.

Review Key Ideas and Vocabulary—Suggested Answers

1. Hubble confirmed the existence of other galaxies and that thegalaxies were moving away from us.

2. (a) toward (b) away

3. (a) between students (0.001 km � 1 m) (c) interplanetary

(b) intergalactic (d) interstellar

4. A standard candle is an object of known brightness and predictablebehaviour that can be used to determine distance.

5. Apparent magnitude is how bright a star looks in the night sky,while absolute magnitude is its actual brightness (the actual amountof light the star gives off from a standard distance).

6. Gravity is directly proportional to mass; the greater the mass of anobject, the greater the gravitational pull that mass has.

7. Fusion, or the combining of atomic nuclei under great heat andpressure, is the reaction that produces light and heat in stars. In ourSun’s core, hydrogen nuclei fuse to form helium nuclei with a releaseof energy (including heat and light).

13CHAPTER

Review Page 454

8. Our Sun is considered a main sequence star because it is still in thelong, hydrogen-burning phase of its life cycle.

9. Thermal expansion opposes the gravity of a star to keep it fromcollapsing.

10. As a star uses up most of its hydrogen, it moves off the mainsequence to become a red giant or supergiant.

11. The Sun is a low-mass star (solar mass of 1); only stars of over 10 solar masses have enough mass to go supernova.

12. A globular cluster is a spherically shaped, tight group of thousands ofstars, and they are very old.

13. Globular clusters are numerous (150 for the Milky Way), and theyare scattered about the galactic centre like a halo. Open clusters arefound only in the galactic disc and usually in the spiral arms.

14. Dark energy is a big mystery because it seems to be an energy foundin empty space, and because it is in empty space it seems not to havea source. Further, dark energy opposes gravity and speeds up theexpansion of the universe. It gets stronger the farther away it is.

Use What You’ve Learned—Suggested Answers

15. Student responses will depend on the source they access. The samplebelow is based on an image from the NASA Goddard Space FlightCenter.

For simplicity, the stages from the Big Bang forward could be givenas

Time zero: the Big Bang

A. 10–43 s to 10–35 s: gravity separates from the unified forces.

B. 10–35 s to 10–33 s: cosmic inflation; the visible universe expands to the size of a softball.


10�43 s 10�35 s 10�33 s 380 000 y

A B C

Big Bang

Not to scale

D E F G

WMAP andCOBE peer intothe distant pastof our galaxy

stars and galaxies form 100 to 500 million yearsafter the Big Bang; the universe now has light

BigBang

10�43

sec10�33

sec380 000

years10�35

sec

Present

13.7 billion years

100 millionyears

500 millionyears

8.7 B.Y.

A B C D E F G

C. 10–33 s to 380 000 y: the strong and weak nuclear forces and electromagnetism separate from the unified forces; at 380 000 years, the universe is cool enough (60 000 °C) for atoms to remain stable.

D. 380 000 y to 100 million y: slight temperature and density variations appear in the background radiation; this is what COBE and WMAP have been observing.

E. 100 million y to 500 million y: star and galaxy formation begins and galaxy clusters form.

F. 500 million y to present: galaxy evolution continues and universal expansion continues.

G. 5 billion years ago: dark energy increases the expansion rate of the distant universe.

16. Two thousand kilometres from Vancouver would place a walker at ornear the Manitoba–Ontario border.

17. A scale drawing (at 1 cm � 1 � 108 km) done carefully can reveal adistance to Saturn of 1.4 � 109 km, which is very close to itsdistance of 1.434 � 109 km. See Figure 4 on Student Book page 449 for an example of a scale drawing.

18. (a) one light year � 9.5 � 1012 km

78 000 � 9.5 � 1012 km � 74.1 � 1016 km

� 7.4 � 1017 km

It is 7.4 � 1017 km to the Sagittarius dwarf galaxy.

(b) Assuming a 9:00 a.m. start and an end time of 3:00 p.m., the trip there would have to be made in 3 h at a speed of 2.47 � 1017 km/h. A return trip at the same speed would get you home for the final bell.

Given that the speed of light is 10.8 � 108 km/h, your travelling speed would be equal to 2.3 � 108 times the speed of light!

19. Type Ia supernovas can be used as standard candles because they areall believed to have the same luminosity or brightness. They are alsobrighter than anything else in a galaxy, so we can see them from veryfar away.

20. Hydrogen has an atomic mass of 1, while helium’s atomic mass is 4.The extra nuclei are only necessary to form helium-3 (atomic massof 3), the isotope that is fused together to create helium. As helium(atomic mass of 4) is formed, two hydrogen nuclei are released,along with enormous quantities of light and heat energy.

21. (a) convection

(b) fusion (thermonuclear) reactions in the Sun’s core

(c) a convection cell

(d) solar granules


22. A diagram of the solar wind striking Earth’s magnetic field wouldlook like this:

23. (a) Do not look through binoculars at the Sun; the concentrated energy will permanently damage eyesight.

(b) A focused image of the Sun would burn a hole in the paper and possibly set it on fire.

(c) Cooling the binoculars occasionally prevents the lenses from delaminating in the heat.

24. All of the elements above iron (Fe) in the Periodic Table are createdwhen a supernova occurs. It is only during a supernova thattemperatures and pressures develop that are necessary to form theheaviest elements. Many of these heavy elements exist in us in traceamounts. The explosion of the supernova scatters these elements. Intime, those elements will become part of a nebula and eventuallypart of a new solar system. These are the elements we are made of.

25. (a) barred spiral

(b) spiral

(c) elliptical

Think Critically—Suggested Answers

26. Students’ diagrams will consist of a full spectrum in the middle of aset of three. The two yellow lines of sodium (Figure 5 on StudentBook page 457) will be the uppermost diagram, with the linescentred above yellow in the full spectrum. In the lower diagram, theblue-shifted image will have the two yellow lines shifted to beneathgreen, blue, or violet of the middle spectrum. This star, with its blue-shifted spectrum, is moving toward us.

27. A flat universe is one that is infinite in extent and expanding. Withthe discovery of dark energy, we have an explanation of why theouter reaches of the universe have increased their rate of expansion.


Earth’s magnetic field—skewed due to collisionwith solar wind

solar wind

Sun

Earth

bow shock wave due tocollision of solar wind withEarth’s magnetic field

Students may also discuss open and closed universes and comparethem to a flat universe.

28. When the whistle is high pitched, the train is approaching theobserver. As the whistle deepens, the train is moving away. Soundwaves, like light waves, compress as the energy source approaches theobserver and stretch as the source moves away. Both light and soundare electromagnetic energies.

Reflect on Your Learning—Suggested Answers

29. By the end of the chapter, students should be able to respond to allthe questions from the beginning of the chapter and, hopefully, havedeveloped many more of their own. Students may ask about– the first few minutes of the Big Bang– the ultimate fate of the universe– whether we could travel through a black hole

You may want to put out a question box and have students ask anyquestion that they want about the universe.


ESL/Extra Support

• If students are having difficulty reading and answering questions, havethem work with students who are strong in reading and writing.

• Have students create flash cards or two-column notes for all the keyideas and the vocabulary.

Extra Challenge

• Challenge students to create an interactive multimedia quiz based onthe vocabulary words, concepts, and key ideas of this chapter.


chapter 13 the universe and its stars page 412

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