stardate teacher guide 2008

8/9/2019 StarDate Teacher Guide 2008

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TEACHER GUIDE


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Get Close to McDonald Observatory

For complete details

432-426-3640

mcdonaldobservatory.org/teachers

Live and in Person

McDonald Observatory offers a unique set-ting for teacher workshops: the Observatoryand Visitors Center in the Davis Mountainsof West Texas. The workshops offer inquiry-based activities aligned with national andTexas science and math standards. Teacherscan practice their new astronomy skills underthe dark West Texas skies, and partner withtrained and nationally recognized astronomyeducators.

mcdonaldobservatory.org/teachers/profdev

Live for Students

The Frank N. Bash Visitors Center featuresa full classroom, 90-seat theater, astronomypark with telescopes, and an exhibit hallfor groups of 12 to 100 students. Theseprograms offer hands-on, inquiry-basedac-tivities in an engaging environment, provid-ing an informal extension to classroom andscience instruction. Reservations are recom-mended at least six weeks in advance.

mcdonaldobservatory.org/teachers/visit

Live on Video

Visit McDonald Observatory from the class-room through an interactive videoconferenceprogram, Live! From McDonald Observato-ry. The live 50-minute program is designedfor Texas classrooms, with versions for grades3-5, 6-8, and 9-12. Each program is alignedwith Texas education standards.

mcdonaldobservatory.org/lfmo


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Table of Contents

To the Teacher 4

Resources 38

S TARD ATE/ UN I V ERSO T EACHER GU I D E 3

The StarDate/Universo Teacher Guide is published by the McDonaldObservatory Education and Outreach Office, 2609 University Ave.#3.118, Austin, TX 78712. 2008 The University of Texas at Austin.Direct all correspondence to StarDate, 2609 University Ave. #3.118,Austin, TX 78712, or call 512-471-5285. POSTMASTER: Send changeof address to StarDate, The University of Texas at Austin, 1 UniversityStation, A2100, Austin, TX 78712. Periodicals Postage Paid at Austin,TX. StarDate and Universo are trademarks of the University of TexasMcDonald Observatory.

Visit StarDate Online at stardate.organd Universo Online at radiouniverso.org

Staff

EXECUTIVE EDITOR Damond Benningfield

EDITOR Rebecca Johnson ART DIRECTOR Tim Jones CURRICULUM SPECIALISTS Dr. Mary Kay Hemenway

Kyle Fricke Brad Armosky

CIRCULATION MANAGER Paul PreviteDIRECTOR,

PUBLIC INFORMATION Sandra Preston

Special thanks to all the teachers who evaluated this guide.

Front CoverA Hubble Space Tele-scope view of a swathof the Coma Cluster, acollection of thousandsof galaxies. Astrono-mers are studyingComa to learn aboutthe evolution of galax-

ies in clusters.

Back CoverWith Earth looming in the background, astro-nauts service Hubble Space Telescope in thecargo bay of space shuttle Discovery.

NASA

/STSCI/COMAHSTACSTREASURYTEAM

5th Edition

TEACHER GUIDE

Support for Program num-ber HST-EO-10861.35-A was

provided by NASA through agrant from the Space Telescope

Science Institute, which is oper-ated by the Association of Univer-

sities for Research in Astronomy, Incorpo-rated, under NASA contract NAS5-26555.

Classroom Activities

Shadow Play 6

Modeling the Night Sky 8Observing the Moon 11

Planet Tours 14Solar System Science 15Rock Cycle 16Equatorial Sundial 18Scale Models 20

Sunspots 22

Spectroscope 24Stars and Galaxies 28Coma Cluster of Galaxies 30


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5/40S TARDATE/ UN I V ERSO TEACHER GU I D E 5

database of the information filed atthe resource station. Some teachersuse this station as a reference sourcefor assignments.

Bilingual InstructionUniverso can help you meet the

needs of Spanish-speaking studentsor students who are learning Span-ish.

Have Universo CDs available at alistening station. Use the programs tointroduce the lessons and vocabularyto bilingual students before the les-son in English.

Have students who need supportin Spanish listen to the programs toreview concepts taught in English.

Encourage Spanish students to listento Universo programs. The writtentext (in Spanish) may be printed forthem to follow. For some programs,students can check their comprehen-sion by listening to or reading theEnglish version of the program afterthey hear the Universo program.

Cross-Curriculum ConnectionsYou can incorporate

StarDate and Univer-

so into many subjectareas, including:

Language Arts andSocial Studies

Use the programs

on skylore to create interest inmythology and ancient civiliza-tions.

Have students keep a StarDateor Universo journal with their

summaries of the programs andanswers to the pre-listeningquestions. Journal entries mayconsist of phrases, sentences,paragraphs, or drawings toillustrate the core concept.

Encourage students tothink on a large scale.For example, in teach-ing a unit on Thoreau,ask them to consider thevastness of the universe,using the radio shows to

spark abstract thought andprepare them for existentialliterature.

Use the scripts from theStarDate or Universo websites and material from Star-Date magazine as supple-mental reading materials.

Encourage students to explore thehistorical context and relevance of

the events and livesof the astronomersdescribed in StarDate

and Universo pro-grams.

Use the programs toexplore the culturalperspectives relatingto astronomy and toteach about the impact

of celestialevents on cul-tural develop-ment.

Mathematics

Students canuse graphs andcharts duringthe skywatch-ing activitiesin this guide.They can applyconcepts ofproportion andpercentage as

they compare the sizes of planets orthe distances between planets within

our solar sys-tem. They canestimate timesand relative dis-tances.

Older studentscan apply princi-ples of geometryand trigonometryas they explorethe angles andorientations ofplanets and satel-lites or the position

of the Sun or Moon inthe sky throughout theday or year.

Fine Arts Encourage studentsto make drawings oftheir concepts relatedto the programs. Forexample, if the pro-gram is about sunsets,

they can draw their idealsunset, which might lead into a dis-cussion of the Suns color and why itappears redder at sunrise and sunset.Or, for a program about space flight,students might draw a spacecraft vis-

iting another planet or a comet. Astronomy-related music has beenpopular for centuries. Your studentsmay be more familiar with John Wil-liams score for Star Wars thanHolsts The Planets, but both piecescan be used as a trigger for combin-ing their ideas about astronomy withmusic.

Individualized LearningBecause StarDate and Universo top-

ics range from basic to more complex

concepts, you can use them with stu-dents of all ages and ability levels.

With a copy of the programs script,students can highlight key conceptsand challenging words as they listento the program.

Have students visit StarDate Onlineor Universo Online as an enrichmentactivity. They can search the web sitefor answers to their astronomy ques-tions or read the daily FrequentlyAsked Question.


6/406 STARD ATE/ UN I V ERSO T EACHER GU I D E

Everyone and everything has a shadow. Shadows illustrate how three-dimensional objects can be viewed in two dimensions. Youngerstudents can learn about the Suns relative motion in the sky as theyexperiment with shadows.

MATERIALSChalk

Outdoor drawing area

Lamp

Globe (a large globe is preferable)

Tape

Action figure (3 inches or smaller)

ACTIVITY ONEBegin by asking, Where is the Sun

at noon? Depending on theage of the child, responses

might be straight up, in

the sky, overhead, or in

the south. Ask, What is a

shadow? Accept responses.

PREPARATIONDivide the class into teams of two or three before going outside.

EXPERIMENTBegin in the morning. One member is to play statue holding still

while the other team members trace the outlines of both the statues feet

and shadow on the pavement. When all the tracings are completed, the

entire class can examine them. Wait about 3060 minutes, then ask the

statues to return to their places (which is why they traced their feet) and

hold the same position again.

ANALYSISWhat has changed?

ANSWERStudents should notice that the

length and position of the shad-

ow have changed. Younger chil-

dren may think that the statue

changed position. Ask them to

predict where the shadow will

be in three hours. Repeat the

tracings about once per hour

until the end of the school day.

The shadows will grow progres-

sively shorter in the morning

until mid-day, after which they will grow longer. It is best to do the tracings

throughout the school day. Note that the shadow never shortens enough to

disappear, which means that the Sun doesnt pass directly overhead at noon

(unless you live between the tropics). Depending on the grade, students may

Shadow PlaySunwatcherSUntil well into the last century, one of

the most important people in

the pueblos of the southwestwas the Sunwatcher. Each day,he watched the Sun rise, using

hills or other objects to track its motionalong the horizon. His observationstold the tribe when to plant or harvestcrops, and when to conduct importantceremonies.

The Sunwatchers may have beencarrying on a tradition established bysome of the ancestors of the pueblopeople the Anasazi, a Navajoname that means the ancient ones.They built a large, well-ordered civi-lization in the Four Corners region amillennium ago.

Archaeological sites at several Ana-sazi villages suggest that they watchedthe Sun carefully. One example is theSun room in Hovenweep Castle, a ruinin southeastern Utah. Doorways andwindows in the room align with the sun-set on the summer and winter solstices when the Sun appears farthest northand south in the sky and the equi-

noxes, when its half-way between.Nearby, a pair of buildings atop

Cajon Mesa apparently served as asolar calendar. Sunwatchers kept trackof the Suns motion from a series ofwindows. They also used the shadowsof the two buildings to determine thearrival of the solstices and equinoxes.

The most famous Anasazi sunwatch-ing sites are in Chaco Canyon, innorthwestern New Mexico. In fact,quite a few people are visiting the can-

yon this week to watch the sunrise on

the summer solstice.

This is the transcript of a StarDate radio episode that

aired June 19, 2001. Script by Damond Benningfield,

2001.



measure the lengths of the shadows or even graph the length versus time of

day. Discuss the results.

ACTIVITY TWO

This activity demonstrates the daily motion of Earth. We perceive the Sunas rising, crossing the daytime sky, and setting. It is actually Earth that

moves.

PREPARATIONInside the classroom, arrange all the children in a circle around a lamp,

which represents the Sun. The teacher should demonstrate and then ask

the children to spin. (Young children prefer the term spin to rotate

when thinking about Earths motion.)

DEMONSTRATIONTo find the proper direction, place your right hand over your heart (the

position for reciting the Pledge of Allegiance) and rotate in the direction

the fingers point. (As an extension, walk around the lamp to model Earthsannual motion around the Sun. Dont try to spin and walk at the same

time; it takes 365.25 spins to make a year!)

ANALYSISWhat has changed?

ANSWERWhen children are facing the lamp, it is day. When they are facing away

from the lamp, it is night.

ACTIVITY THREE

PREPARATIONInside the classroom, demonstrate the connection between the first two

activities. First, tape the action figure onto the globe at your geographic

location. Still using the lamp to represent the Sun, place the globe at least

6 feet away from the lamp (ideally with the globes spin axis tilted rela-

tive to the lamp to represent the current season, so it will be tilted away

from the lamp in the winter and toward it in the summer).

EXPERIMENTDarken the room and spin the globe so that everyone can see a change

in the length and position of the figures shadow.

ANALYSISHow does the figures shadow compare to the childrens shadows outside?

ANSWERThe behavior of the shadows should be similar. Spinning the globe counter-

clockwise when looking down on the north pole will show the proper move-

ment of the shadow from west to east.

EXTENSIONStudents draw pictures of why we have day and night.

Students study how ancient people created stories about what causes day

and night.

NATIONALSCIENCEEDUCATIONSTANDARDS

Content Standard in K-4 EarthScience (Objects in the sky,

Changes in Earth and sky) Content Standard in K-4 Science

as Inquiry (Abilities necessary todo scientific inquiry)

Light bulb


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PISCES AQUARIUS CAPRICORNUS

D C

S TARD ATE/ UN I V ERSO T EACHER GU I D E 9

C B

VIRGO LEO CANCER

B A

GEMINI TAURUS ARIES

A D

SAGITTARIUS OPHIUCHUS LIBRASCORPIUS



OphiuchuSandSerpenSTwo constellations that dontget a lot of respect are in the

southwest this evening, abovethe Moon and the bright planet

Jupiter. One of them is slighted by any-one who can name the 12 signs of thezodiac. The other was slighted by thepeople who established the constella-tion boundaries: they chopped out itsmiddle.

The constellations are Ophiuchus,the serpent bearer, and Serpens, theserpent.

Ophiuchus is one of the largest con-

stellations. More important, it lies alongthe ecliptic the Suns path across thesky. The constellations along this pathform the zodiac. But Ophiuchus isntincluded in the lineup, even though theSun spends more time inside its bordersthan in Scorpius, which is next door.

Ophiuchus represents the founderof medicine. In myth, he was such agood healer that he even brought thedead back to life. That was reminiscentof the powers of a snake: It can kill,but it also rejuvenates itself every year

when it sheds its skin. So in the sky, thephysician is also known as the serpentbearer.

Appropriately enough, hes holdingon to Serpens. The serpents head isto the west of Ophiuchus, with the tailto the east severed by the body ofOphiuchus.

Serpens and Ophiuchus are well upin the southwest at nightfall. Look for thecrescent Moon quite low in the sky, withbrilliant Jupiter and the bright orangestar Antares to its upper left. Ophiuchusand Serpens stretch out above thisbright trio.

We see different stars at different times of year because Earth orbits

(revolves around) the Sun. Some constellations are small, while others are

large. The Sun appears to move from one constellation to another in as few

as 6 days or as many as 43.

Add more celestial objects to your model by handing planet cards to more

students. These objects orbit the Sun like Earth, but at different rates. This

works best if they come in one at a time, each with their own rate of orbit

ing the Sun. The following table recommends some approximations to use

along with the exact values, for periods of revolution (the time it takes

for the object to revolve around the Sun one time). Distance scales are

not preserved in this activity. For example, tell the students that Mercury

orbits the Sun four times in one Earth year. So the person who represents

Mercury has to race around the Sun four times while Earth goes around

only once. Some students will count this out. For younger students, draw-

ing the circles on the floor helps them maintain the proper distances. Stop

occasionally to ask, If you are on Earth, where or when can you see that

object? Add more or fewer objects depending upon the age of the group.

For older students, model sunrise/sunset and ask what objects are vis-

ible in the sky at various times of day (just after sunset or at midnight,

for example) and in which constellations they appear. If you have already

studied phases of the Moon (see Observing the Moon, page 11), it can

be inserted into this model, orbiting Earth in about one month while Earth

orbits the Sun in one year.

Object Approximate period Actual period

Mercury 1/4 year 0.24 year = 88 daysEarth 1 year 1 year = 365.25 daysMoon 1 month 27.3 daysMars 2 years 1.88 yearsJupiter 12 years 11.86 years

EVALUATE

The asteroid Ceres has a period of 4.6 years. Where would it go in this

scheme? (Answer: between Mars and Jupiter.)

Why did we not include Venus (0.61 year), Saturn (29.42 years), Uranu

(83.75 years), or Neptune (163.73 years)? (Answer: 0.61 years wouldbe difficult to model and adding Venus would make it crowded. The othe

planets orbit so slowly that they would barely move!)

Place a plain piece of paper under the loop and sketch the number of

orbits (or partial orbits) for Earth and two other objects.

Teaching note: Although this activity does not indicate relative distanc-

es, it is correct that all of the planets orbit the Sun in approximately the

same plane. That is why we can limit ourselves to just the constellations

that form one great circle on the celestial sphere.

This is the transcript of a StarDate radio episode

that aired September 17, 2007. Script by Damond

Benningfield, 2007.



Does the Moon always look the same? Does its surface look differ-ent at different times? What will your students say when you ask themthese questions?

Many students are aware that the Moon goes through phases, butexcept for the man in the Moon which many admit they have ahard time seeing they probably havent thought about the surfaceof the Moon and how we view it from Earth. Some students may men-tion that the Moon changes colors. It actually doesnt the Moonscolor changes due to the effects of our own atmosphere, not anythingintrinsic to the Moon.

MATERIALS

Clear skies

Notebook

Soft drawing pencil

Binoculars

Chart on page 13

PREPARATIONFirst, figure out when you can see the Moon. Use the StarDate Sky Alma-

nac or a calendar to find the Moons phase on the day you will carry out

this activity. The outdoor part of this activity requires good weather.

In choosing a day, keep these tips in mind:

Although new Moon may seem to be the perfect phase for this activ-

ity, it really isnt. New Moon means no Moon. During this phase, the

Moon is in the sky all day, but it lies in the direction of the Sun and its

night side is facing Earth. That means no lunar surface features will be

visible.

During full Moon, patterns of dark and light on its surface are easy to

distinguish. Thats when the maria smooth, almost crater-free

regions on the Moon are easiest to see.

During crescent or quarter phases, the craters and mountains cast dis-

tinct shadows and become more noticeable.

Once you know the Moons phase, the chart provided here will help you

decide the best time of day (or night!) for lunar viewing.

ACTIVITYDraw two 10-cm circles in your observing notebook. List the time, date,

sky conditions, and location. Indicate the phase of the Moon within your

circle. Now, sketch in the lightand dark areas. A soft pencil

works best. Some students like to

smudge their lines to show light

and dark. If you have binoculars,

repeat the activity using them.

Binoculars will allow you to see a

lot more detail. At another phase

(at least five days later), repeat the

activity.


Content Standard in K-4 Earth andSpace Science (Changes in Earth

and sky, Objects in the sky) Content Standard in 5-8 Earth and

Space Sciences (Earth in the solarsystem)

Content Standard in 5-8 Scienceas Inquiry (Abilities necessary todo scientific inquiry)

Observing the Moon

Lunar eclipseJOHNGIANFORTE

Phase New First Quarter Full Last Quarter

Rise Sunrise Noon Sunset Midnight

Highest in Sky Noon Sunset Midnight Sunrise

Set Sunset Midnight Sunrise Noon


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ANALYSISCompare the naked-eye and binocular drawings done on the same date with

each other. What details are visible? Can you identify any features from the

lunar map? Now compare the drawings from one date to the other.

EXTENSIONFor an in-class activity, make craters by dropping marbles or pebbles into a

deep basin of flour sprinkled with dry chocolate milk mix. You should get

nice craters with elevated edges, and some with a series of splashed out

materials centered on the crater. In a darkened room, shine a flashlight

onto the cratered surface and show how the angle of the flashlight deter-

mines the length of the shadows. Students can research the surface of the

Moon in the library or on the Internet.

As a math extension, calculate the angle between the Sun and Moon for

different phases.

For English, write a poem about the Moon.

FullearthThe Moon is AWOL right now. It pass-

es between Earth and the Sunearly tomorrow, so its hiddenin the Suns glare. And even ifthe Sun wasnt in the way, there

wouldnt be much to see: Its night onthe lunar hemisphere facing our way,so the entire disk is dark.

Well, almost dark. The Sun is shiningon the far side of the Moon, so its notlighting up the side that faces Earth. Butthe side that does face Earth isgettingsome sunshine reflected off of Earth.

We can see this earthshine when

theres a crescent Moon in the sky,because it makes the dark portion of thelunar disk look like a gray phantom.

Right now, the earthshine is at its mostintense. Thats because theres a fullEarth in the lunar sky. Earth covers anarea more than 13 times greater thanthe Moon does. And on average, eachsquare mile of Earths surface reflectsmore than three times as much sunlightback into space. So a full Earth is about40 times brighter than a full Moon.

While a full Moon always looks thesame, a full Earth is constantly chang-ing. Anyone standing on the Moonwould see the entire surface of Earth asour planet turns on its axis. So theydsee different continents and oceans,plus the unceasing motions of cloudsin the atmosphere. And since the sameside of the Moon always faces Earth,our planet would always appear inexactly the same spot in the sky abright blue and white ball spinning inthe sunlight.

12 STARD ATE/ UN I V ERSO T EACHER GU I D E

Above: Impact craters and

volcanic valleys on the lunarsurface.Right: An Apollo 15 astro-naut salutes the flag.


aired May 7, 2005. Script by Damond Benningfield,

2005.



LEARNINGTHELUNARLANDSCAPE

Ocean

of

Storms

Seaof Rains

Sea ofTranquility

Sea ofFertilitySea of

Nectar

Sea ofClouds

Sea ofMoisture

Sea ofSerenity

Sea ofVapors

Sea ofCold

Bay of Dew

TychoTycho

Copernicus

Langrenus

Taruntius

Kepler

Aristarchus

Plato

Archimedes

Ocean

ofStorms

Seaof Rains

Sea ofTranquility

Sea ofFertilitySea of

Nectar

Sea ofClouds

Sea ofMoisture

Sea ofSerenity

Sea ofVapors

Sea ofCold

Bay of Dew

Copernicus

Langrenus

Taruntius

Kepler

Aristarchus

Plato

Archimedes

Sea ofCrisesSea ofCrises

JPL/TIMJONES



Planning to take a vacation soon? Visit Phobos! Small and cozy, Pho-bos orbits the fourth planet from the Sun in less than eight hours.From your observation deck on Phobos, you will have a superb viewof Mars. You will see its mountains, polar ice caps, and the largest volcano in the solar system. Call your cosmic travel agent today!

Try this creative activity to help your students explore the solar systemin an imaginative manner.

PREPARATIONUse StarDate or Universo CDs or printed materials such as StarDate: The

Solar Systemor the StarDate/Universo websites to find information about

solar system objects. As an aid, provide some examples of real travel bro-

chures or websites with travel ads available for students to preview. For

secondary classrooms, a good resource is Active Physics: Sportsby Arthur

Eisenkraft (ISBN 1-891629-04-02).

ACTIVITYBreak the class into teams that will research one planetary body (if youhave a large number of teams, you can include some of the moons of the

solar system, or comets and asteroids). The students use the information

they collect to create travel posters, brochures, or television or radio com-

mercials for their object.

Each project should include real facts about the solar system object, but

may use far-out features to form the basis of unusual recreation oppor-

tunities. When everyone is finished, each team presents its product to the

rest of the class.

ASSESSMENTDevelop a grading rubric for dif-

ferent grades, keeping in mind the

standards. In addition to facts

about solar system objects, the rubric

should ascertain whether students

use physical data to make compari-

sons. Making comparisons is the key

to learning science in this activity.

Some teachers may be comfortable

with allowing the students to design

the rubric for their class after they

have started the project; others may

want to pass the rubric out at the

beginning of the assignment. One

teacher had students make Power-

Point presentations and gave extra

credit for working some mythology

and images into the presentation.

Planet Tours

MOOnandJupiterOn the scale of our everyday lives,

Earth is a big place. Its so big,in fact, that an airliner, flyingnonstop, would take about twodays to circle its equator. But

our planet is tiny compared to Jupiter,the giant of the solar system. Its 11times bigger around than Earth is, sothat airliner would need about threeweeks to circle Jupiters equator.

And the sights out the window wouldbe spectacular.

Jupiter doesnt have a solid surface,so you wouldnt see any mountains,deserts, or oceans. But the Jovian atmo-sphere is filled with giant storms, andwith belts of clouds that race around theplanet at hundreds of miles an hour.

To avoid turbulence, youd have togo around the biggest storm systems.That could add days to the trip, though,because the storms can be as big asEarth. And they produce lightning boltsthat are hundreds of times as powerfulas those on Earth. At night, such blastsmight be visible for thousands of miles.

Different chemicals in the atmosphereadd color to the clouds, so youd seeshades of yellow, brown, and redmixed with the white clouds thatre

made of water vapor.And if youre afraid of heights, youwouldnt want to look down: the cloudlayers atop the Jovian atmosphere arescores of miles thick, so it would be along way down.

Future tourists may detour aroundJupiters Great Red Spot, a storm thatis larger than Earth.


Content Standard in 5-8 Earth andSpace Science (Earth in the solar

system) Content Standard in 5-8 Physical

Science (Properties of objects andmaterials)


that aired February 19, 2006. Script by Damond

Benningfield, 2006.



In this activity, students explore and compare planets in our solarsystem. Each student becomes the ambassador for a planet and pre-pares by researching their planet, then meets with other ambassadorsto form new mini-solar systems.

MATERIALSStarDate: The Solar Systemor other reference material on the solar system.

ACTIVITYSplit the class into small groups; each group researches one planet. Stu-

dents in the group make a list showing the planets atmosphere, size, mass,

distance from the Sun, geology and surface features, surface temperature,

and moons. They also write a sentence describing something unique or

striking about their planet an impression.

Have one ambassador from each group join with ambassadors from other

groups. Each group need not have exactly the same planet mix, but thereshould not be duplicates of a planet within a solar-system group. The

ambassadors interview each other to exchange information and impres-

sions.

Once they have shared their information, the ambassadors should consider

how they could organize themselves. Some might want to arrange them-

selves in order of distance from the Sun. Others might notice that some

planets are small and rocky and others large and gaseous. Solar systems

may invent several organization schemes. They will note interesting or

unexpected planetary features. For instance, Olympus Mons, a super vol-

cano on Mars, seems odd. Have each system report to the class.

Hints:The results may vary if the mix of planets is different in each sys-

tem. The teacher should help students sum up the results, noting

similarities and differences among the schemes. Most planetary

scientists organize planets into two divisions: terrestrial (like

Earth) and Jovian (like Jupiter). Terrestrial planets are small and

rocky with few or no moons, and they are close to the Sun. Jovian

planets are gaseous giants with many moons, and are farther

from the Sun.

EXTENSIONWhat planet or object should NASA choose for future human

exploration? Ask the solar system to choose a planet or moon.

With pictures and text describing its features, design a spacesuitfor the visit. For instance, Jupiter poses a serious challenge its

mostly high-pressure gas. What materials would the astronaut

need to stay alive? How would the suit help the astronaut explore

Jupiter? Would wings help?

Compare planets in our solar system to new extrasolar planets

that astronomers have discovered.

Solar System Science

The solar system is filled with amaz-ing sights, including (from top), anavalanche beneath a Martian icecap, the surface of Saturns big moonTitan, and Saturns bright rings.


Content Standard in 5-8 Earthand Space Science (Earth in thesolar system)

Content Standard in 5-8 Scienceas Inquiry (Abilities necessary todo scientific inquiry)

Content Standard in 5-8 Physi-cal Science (Properties of objectsand materials)

NASA(3)



This activity combines the concept of Earths rock cycle with the char-acteristics of other planets in the solar system. After learning aboutEarths rock cycle and the basic characteristics of objects in the solarsystem, students can consider how to extend this concept to otherobjects. The students goal is to create a rock cycle for each selectedsolar system object.

PREPARATIONFirst, as a class, students should agree on a course of action based on thei

own driving questions. For instance:

Which objects probably have some sort of rock cycle?

What information about the object would relate to the rock cycle?

What are the available resources of information?

How should we as a class conduct our research and present our results?

After their investigation, students must communicate their results to theirpeers. This involves not just presentation, but also discussion about the

supporting evidence for

their rock cycle claims.

As an extension, stu-

dents can investigate the

case for Pluto and come

up with their own con-

clusion what is Pluto?

MATERIALS

StarDate: The Solar Sys-

tem(or Universo Guadel Sistema Solar)

Slide projector and

slides (optional)

Internet access, com-

puter, and browser

(optional)

ACTIVITY

ENGAGEBegin by reviewing the basics of Earths rock cycle. Then pose a question

about other members of our solar system (not just planets): do they have

rock cycles, too? Record students driving questions and discuss ways to go

about answering those questions. You may wish to reserve Pluto as a spe-

cial solar system member for later investigation (see the Extend section).

EXPLOREDivide students into small groups of four to six. Each group should inves-

tigate a different planet, depending on the result of the class brainstorm.

StarDate: The Solar Systemwill help students gather information about

planetary features that provide clues to the planets rock cycle. If students

have trouble, help them consider Earths rock cycle and how it relates to

Rock Cycle

planetarytherMOStatEven on a winter day, our Earth is a

fairly warm, comfortable homefor life. Thats thanks in part tothe carbon dioxide in our air.Although it accounts for only

a tiny fraction of the atmosphere, itwarms our planet by about 50 degreesFahrenheit, and keeps Earth from turn-ing into a ball of ice.

Carbon dioxide is called a green-house gas. Like the glass in a green-house, it traps heat, in the form ofinfrared energy. So sunlight can comein, but much of the heat cant get out.

In the distant past, the atmospherecontained much more carbon dioxide.But rain washed most of it out of the air.It combined with other chemicals to formcarbonate rocks, such as limestone.Today, some carbon dioxide is pumpedback into the air by volcanoes.

Theres also carbon dioxide in theatmospheres of our two closest plan-etary neighbors, Venus and Mars.

Mars may have undergone the sameprocess as Earth, with almost all of itscarbon dioxide now locked up in rocks.The Martian atmosphere is thin, so Marsis cold and desolate, and temperaturesnormally stay well below zero.

On Venus, though, the carbon diox-ide remained in the atmosphere. Today,Venuss atmosphere is 90 times thickerthan Earths, and its made almostentirely of carbon dioxide, so the sur-face temperature is about 860 degreesFahrenheit.

Only on Earth is the balance just rightto provide a comfortable home for life.

Earths Rock Cycle

SEDIMENTARY

METAMORPHIC IGNEOUS

exposure& erosion

melting

melting

heat &pressure

cooling &chemicalchange

exposur

& erosio


that aired February 22, 2000. Script by Damond

Benningfield, 1999.



Earths features. Air and water erode rocks into sediments. Earths mantle

heats buried rocks to make metamorphic rocks. Continents collide and

raise mountains for water and air to erode.

EXPLAIN

The planets closest to the Sun (Mercury, Venus, Earth, and Mars) arerocky; they will most likely show evidence of a rock cycle. The gas giants

(Jupiter, Saturn, Uranus, and Neptune) wont. But these gas giants have

rocky moons that can be investigated. For each solar system object, infor-

mation about its surface features, agents of erosion, and geologic structure

under the crust will provide the major clues necessary to construct a possi-

ble rock cycle. Check your schools library for available resources. A wealth

of information about the planets resides on StarDate Online. One effective

way to organize the research is to break the class into research groups,

with each focusing on one planet or moon.

EXTEND

Break the students into another set of groups with each member being anexpert on a different planet. These groups discuss some of the following

questions:

What is Pluto? Is it a planet?

What about the gas giants Jupiter, Saturn, Uranus, and Neptune?

Instead of rock cycles, might they have gas cycles?

Consider what might happen if you could change the conditions on your

object, such as adding liquid water to Mars or changing Earths atmo-

sphere. Would these changes affect the rock cycles on these bodies?

EVALUATEAfter their investigation, each group presents its objects rock cycle to

the class. During their presentation, students should point to particu-

lar features of their planet as evidence that supports different phases

of their hypothetical rock cycle. This could be a presentation involving

posters or computer graphics. Or it could be something else a bit more

interactive, such as a poem or song.

Rain, wind, rivers, and ocean tideserode surface rocks, washing mate-rial into the oceans to begin therock cycle anew (below). Volcanoeson Io (lower left), Earth (bottom),and other bodies deposit new rockson the surface.


Content Standard in 5-8 Scienceas Inquiry (Abilities necessary to

do scientific inquiry, Understand-ing about scientific inquiry)

Content Standard in 5-8 Earth andSpace Science (Earth in the solarsystem, Structure of Earth system)

NASA(2)

NOAA


18/40

egyptianStOnehengeSummer arrives in the northern hemi-

sphere today, as the Sun appearsfarthest north for the entire year.

In centuries long past, skywatch-ers around the world watched for thesolstice at special observatories circlesof stones. The most famous is Stonehengein England, but circles of much smallerstones were found in the Americas, too.

The oldest of these stone observatoriesmay have been built in southern Egypt,at a site called Nabta. It was used6,000 years ago, and perhaps even ear-lier at least a thousand years beforeStonehenge.

Anthropologist Fred Wendorf of South-ern Methodist University discovered thesite in 1973. Last year, studies by Wen-

dorf and Colorado astronomer J. McKimMalville confirmed that Nabta had anastronomical function.

Among other artifacts, the site containsa 12-foot-wide calendar circle of smallstones. Two pairs of stones stand acrossthe circle from each other. If you lookthrough the spaces between each pair,youll see the point where the Sun roseon the summer solstice thousands of yearsago. This alignment was important to thepeople who lived at Nabta because mon-soons brought a few inches of rain to the

region soon after the solstice.Over the centuries, though, the rainsdried up and Nabta was abandoned.But the people of Nabta may have left alegacy. Their culture may have stimulatedthe formation of Egypts Old Kingdom the civilization that built the greatpyramids.

18 STARD ATE/ UN I V ERSO T EACHER GU I D E

One of astronomys first tools to measure the flow of time, a sundial issimply a stick that casts a shadow on a face marked with units of time.As Earth spins, the shadow sweeps across the face. There are manytypes of sundials; an equatorial sundial is easy to make and teaches fundamental astronomical concepts. The face of the sundial represents theplane of Earths equator, and the stick represents Earths spin axis.

PREPARATIONFirst, find your latitude and longitude and an outdoor observing site in a

clear (no shadows) area. Determine north (from a map, or by finding the

North Star at night and marking its location). Assemble the equipment as

described below. Use a flashlight to demonstrate how to position and read

the sundial indoors before going outside.

MATERIALSANDCONSTRUCTIONEach student team needs a copy of page 19 and a drinking straw.

Have the students cut out the Dial Face Template. Fold and glue the tem-plate, making sure the dial faces are lined up. Cut a cross in the center hol

where the straw will be snuggly inserted. Mark the straw using the latitud

strip as a guide. First mark the bottom of the straw at one end, then mark

a line corresponding to your latitude. Place the straw in the template hole

at the line marking your latitude. The south face of the template should

aim toward the bottom of the straw. Make sure the stick and template are

perpendicular. The straw should fit snugly; tape it in place if necessary.

EXPERIMENTOn a sunny day, take the sundial outside. Set it on a flat horizontal surface

with the bottom of the straw and the folded edge of the template both

resting on the ground. Aim the straw with the top pointing due north. (If

done correctly, the straw will point at the celestial north pole, where we

see the North Star at night.) Record the time on the sundial at least four

times in one day, with measurements at least an hour apart. Each time,

also record the clock time for your date and location. Try this experi-

ment during different months.

ANALYSIS1. If the sundial time did not match clock time, explain why.

2. Why does this sundial have front and back dial faces?

ANSWERS1. For each degree east or west of the center of your time zone (your longitude

difference from the center of the time zone), there is a correction of four min-utes. Also, the Suns location in the sky changes with the seasons, and a correc-

tion of up to about 15 minutes for the equation of time must be made. Read

the correction from the graph on page 19. Daylight Saving Time changes results

by one hour.

2. The shadow of the straw is cast on the north face from March 21 to Septem-

ber 21, and the south face from September 21 to March 21. The plane of the

template is aligned with the celestial equator. The Sun is north of the celestial

equator during the first period (spring and summer) and south of the celestial

equator during the second (fall and winter).

Equatorial SundialNATIONALSCIENCEEDUCATIONSTANDARDS

Content Standard in 5-8 Earth andSpace Science (Earth in the solar

system) Content Standard in 5-8 Science

as Inquiry (Abilities necessary todo scientific inquiry)



1998, 2003.


19/40

60

505

5

45

40

35

30

25

20

9

7

3

4

58

4

3

5

9

8

7

S TARDATE/ UN I V ERSO TEACHER GU I D E 19

1

1

10

9

7

6

1

2

3

4

5

6

8

North FaceSpring/Summer

E W

WE

12

1

2

3

5

6

1110

9

8

7

6

4

12

SouthFace

Fall/Winter

50

55

45

40

35

60

30

25

20

Bottom

DIALFACE

TEMPLATE

20.00

15.00

10.00

5.00

0.00

-5.00

-10.00

-15.00

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Decminutes

Correction for the Equation of Time

Finished Sundial

LATITUDESTRIP



Without being informed of the expected product, the students willmake a Play-doh model of the Earth-Moon system, scaled to size anddistance. The facilitator will reveal the true identity of the system atthe conclusion of the activity. During the construction phase, studentstry to guess what members of the solar system their model represents.Each group receives different amounts of Play-doh, with each groupassigned a color (red, blue, yellow, white). At the end, groups set uptheir models and inspect the models of other groups. They report pat-terns of scale that they notice; as the amount of Play-doh increases,for example, so do the size and distance of the model.

MATERIALS

On a central table for all to share

String

Rulers or meter sticks

Scissors (optional)

For each group

One or more cans of Play-doh. All the Play-doh for a group should be th

same color.

Large paper sheet as a work surface for rolling and shaping the Play-doh

PREPARATIONColor code each amount of Play-doh: red, 2 cans; blue, 1.5 cans; yellow, 1

can; white, 0.5 can. Divide students into groups of two to four members.

Lay out materials for all groups to share in a central location. Distribute

Play-doh and one large piece of paper to each group.

ACTIVITY

Introduce the problem

Tell the groups that they will make a scale model of two members of our

solar system. Do not reveal that it is the Earth and Moon thats the sur

prise that makes this activity memorable. Along the way, they can make

guesses about what the model represents.

Divide the Play-doh

Tell groups to divide their Play-doh into five equal pieces.

They may use whatever creative and clever means they can think of to

solve this problem. Example solution: Roll the Play-doh into a long cyl-

inder, then divide it into pieces. A 50-cm cylinder can be cut into 10-cm

lengths, then formed into spheres. Tell groups to divide up one of the larg-

er pieces into 10 equal size pieces; set one of these smaller pieces aside.

Create two carefully sized pieces

Tell each group to mash everything together (except the one small piece

previously set aside) into one big sphere. Roll the remaining small piece

into a little sphere.

Scale ModelsSOlareclipSeThe Moon will cover up the Sun early

tomorrow, briefly turning day to

night. Unfortunately, though, itllhappen while its already nighthere in the United States, so

well miss out on the show.

The event is a total solar eclipse. Ithappens thanks to a coincidence inthe way the solar system is laid out:Even though the Sun is about 400 timeswider than the Moon, its also about400 times farther away. So when thegeometry is just right, the Moon can justcover the solar disk.

As the Sun disappears, the air getscooler, and the sky turns dark. TheSuns hot but thin outer atmosphere,the corona, forms delicate streamersof light around the Moon. And the firstor last moment of sunlight can form adiamond ring a thin ring of lightaround the Moon, with a bright burstwhere sunlight streams through canyonsor between mountains.

The Moons orbit is tilted a little,so most months the Moon passes justabove or below the Sun, and theres no

eclipse. But two or more times a year,the Moons orbit lines up just right,creating an eclipse. Many eclipses arepartial, so the Moon appears to onlynick the Sun. But this month it goes rightacross the heart of the Sun, creating abeautiful eclipse.

The total eclipse is visible along athin path that runs through China andRussia, across the tip of northern Green-land, and just into Canada. The partialeclipse is visible across a much widerarea, but it doesnt include the U.S.


aired July 31, 2008. Script by Damond Benningfield,

Copyright 2008.



Make a guess

After they have made two Play-doh spheres, ask each group to write down

three guesses about what these solar system objects might represent. Dis-

cuss the guesses with the students. At least one student will guess they are

Earth and the Moon. Next, ask them to make a guess of how far apart to

put their Earth and Moon spheres to make a true model. A scientist follows

up and tests guesses with observations and measurements.

Measure the big sphere diameter; this is the diameter of Earth

Tell each group to measure the diameter of the Earth sphere. They may

cut the sphere in half. They may measure with a string and mark off the

diameter or use a meter stick.

Separate the big and little spheres

After students have measured the Earth and Moon sphere diameters, ask

each group to place the big and little spheres apart by 30 Earth-sphere

diameters. Groups with the least Play-doh will probably be able to lay out

their models on the table top. The two-can group might have to lay out its

model on the floor.

Inspect other models, compare, and analyze

After all the groups have laid out their models, ask everyone to inspect

other groups models. Discuss the results. Models will differ in three main

ways, besides the color of the Play-doh: the relative sizes of the Earth

spheres, the relative sizes of the Moon spheres, and the distance between

the spheres. But all of these differences are related to the same set of pro-

portions. The ratios of Earth diameter:Moon diameter and Earth diameter:

separation distance are the same for each model.

EXTEND

The Sun is about 150 million km from Earth. Estimate how many Earthdiameters and Earth-Moon distances in your system would be needed to

put the Sun in your model. Compare the sizes of the Sun and the Moons

orbit around Earth.

BACKGROUND

Earth to Moon Ratio

Earth Moon Ratio

Diameter (km) 12,756 3,475 3.7

Volume (m3)

V= 4/3

r31.08 x 1021 2.2 x 1019 49

Since spherical volume is 4/3 r3, the ratio of Earth-to-Moon volume is

49.5. The mean separation between Earth and the Moon is 384,500 km.

So the ratio of the Earth-Moon separation to Earths diameter is:

In round numbers, Earths volume is 50 times that of the Moon, and

the Moon is about 30 Earth diameters away. The Sun is 11,759 Earth

diameters, or 390 Earth-Moon distances away from Earth. The diameter

of the Moons orbit is twice the Earth-Moon distance (384,500 km x 2

= 769,000 km); the diameter of the Sun is 1,392,000 km. The Moons

orbital path around Earth is about half the diameter of the Sun.


Content Standard in 5-8 EarthScience (Earth in the solar sys-

tem) Content Standard in 5-8 Science

and Technology (Students shoulddevelop abilities of technologicaldesign)

Content Standard in 5-8 Scienceas Inquiry (Abilities necessary todo scientific inquiry, Understand-ing about scientific inquiry)

384,500 km12,756 km

= 30 Earth diameters.



The Sun is a huge sphere of gas. The visible layer of the Sun, whichwe view as the surface, is the photosphere. Its temperature is about6,200 degrees Celsius (10,340 degrees Fahrenheit). Above the surfaceare the chromosphere and corona. Sunspots are some of the mostnoticeable features of the Sun.

MATERIALS

Telescope (with finder covered)

Piece of white cardboard mounted on a

tripod

PREPARATIONThe easiest way to position the telescope

(since the finder is covered and you dont want to

sight along the side) is to move the telescope until

its shadow is smallest. If your telescope doesnt have

a special motor, the image will slowly track across

the cardboard as Earth rotates. You may use binoculars, although toomuch sunlight can cause heat to build up inside the binoculars and dam-

age them. For binoculars, the standard size (7x35) works satisfactorily.

EXPERIMENTDraw a circle around the edge of the Sun on some paper placed over

the cardboard. Now quickly sketch the positions and sizes of all the vis-

ible sunspots. Write the time and date on the edge of the paper. Repeat

your observations over several days or weeks. (If you trace the images on

very thin paper, you can later overlap them to see changes.) Be careful to

include the fine detail that surrounds some sunspots. An alternative is to

download images from web sites each day to use for this activity or to com

pare to your own data.

ANALYSIS1. Can you identify any sunspots or sunspot groups? Did they change

shape, size, or position over time?

2. If you move the cardboard screen farther away, what happens to the

image?

3. (Advanced) The diameter of the Sun is about 1.4 million km (864,000

miles). Measure the diameter of your image and estimate the physical size

of your largest sunspot. Earth is 12,700 km (7,900 miles). Compare your

largest sunspot with the size of Earth. Find the size of the sunspot with a

proportion equation:

4. Why are sunspots dark?

SunspotsreverSedpOlarityWhen a character in TV science fiction

faces a tough technical prob-

lem, one solution always seemsto work: reverse the polarity.

That may not fix problems inreal life, but for the scientists who studythe Sun, reversing the polarity is a bigevent. It signals that the Sun has starteda new 11-year cycle of magnetic activ-ity.

A new cycle began in January, whentelescopes on the ground and in orbitmeasured a small sunspot a rela-tively cool, dark magnetic storm on

the surface of the Sun. The observationsshowed that the polarity of the sunspotwas reversed from that of the sunspotbefore it.

As the Sun spins on its axis, differentlayers of hot gas spin at different rates.That generates a powerful magneticfield around the Sun.

Over a period of several years, thelines of magnetic force get twisted andtangled. That produces many moresunspots. The lines can also cross eachother, creating short circuits pow-

erful explosions of energy and particles.These outbursts can disrupt communica-tions and electrical systems on Earth.

At the end of a cycle, the Suns mag-netic field flips over: magnetic northbecomes magnetic south, and viceversa.

The Sun has been quiet for the lastfew years. But the start of a new cyclemeans that itll get busier in the yearsahead. The new cycle should peakaround 2012, and end around 2019 when scientists will once again bewaiting for the Sun to reverse polarity.

1,390,473 km

diameter of Suns image in mm

sunspot diameter in km

sunspot image in mm

=



2008.



ANSWERS1. Sunspots change size and

shape over a period of days.

The Sun rotates on its axis in

about 25 days (its equatorrotates faster than its poles).

Observations taken over a

period of several days should

show this.

2. As you move the cardboard

screen back, the image becomes

fainter and larger.

3. Large sunspots can equal Earth in diameter.

4. Do the following demonstration to illustrate that sunspots appear darksince they are cooler than the photosphere (they are about 4,500 degrees

C/7,100 degrees F). Attach a dimmer switch or rheostat to a clear incan-

descent light bulb. Place the bulb on its side on an overhead projector.

With the projector on, focus the bulb so that the filament appears as a

sharp silhouette on the screen. Turn up the power until the filament glows

against the screen, then turn the power down until the

filament is just barely dark against the background.

Turn off the projector and the bulb will seem to

glow dimly by itself. Sunspots are only dark

with respect to the hotter, brighter back-

ground of the photosphere.


Content Standard in 9-12 Scienceas Inquiry (Abilities necessary todo scientific inquiry, Understand-ing about scientific inquiry)

Spanning more than 13 times the totalarea of Earths surface, this large group ofsunspots photographed in 2001 coincidedwith the peak of the 11-year solar cycle(see sunspot number chart below). Inset:Close-up view of a typical sunspot.

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

D A T E

0

100

200

300

SUNSPOT

NUMBER

NOAO/NSF

!SAFETYWARNING

Do not look directly at the Sun,

especially with a telescope. You can

PERMANENTLY DAMAGE YOUR

EYES!When working with students,its best to cover the finder telescope

completely so that they cannot look

through it. Never trust filters that

go into the eyepiece or that

cover the objective.



Just as a geologist collects rocks or minerals and a botanist collectsplants, an astronomer collects light. Astronomers usually cannot touchthe objects they study, like stars or galaxies. But they can analyze thelight these celestial objects radiate using a spectroscope. When anastronomer looks at a star through a spectroscope, he or she sees acolorful spectrum that is full of information.

Students will construct their own spectroscope as they explore andobserve spectra of familiar light sources. Extension activities expandtheir understanding of different kinds of spectra and sharpen theirobserving skills. You may challenge more advanced students to maketechnological improvements to their instruments.

MATERIALS

PREPARATIONMaking the transmission grating cards

1. Cut a 3x5-inch index card in half, resulting in two 3x2.5-inch cards.

Then cut a narrow strip off the three inch side of one of the halves. This

will help fasten the card onto the spectroscope tube.

2. Fold each 3x2.5-inch card in half along the short side, then snip a slit

perpendicular to the fold about half a centimeter from either corner of

the fold. Punch a hole about two centimeters down in the fold. The open

ing should be about a centimeter wide.

Preparing the grating

1. Sandwich the transmission

grating material between two

sheets of transparency mate-

rial. Try not to touch the very

sensitive grating with your

fingers.

2. Cut the sandwich into 1x2-

cm pieces.

3. Tape it into place over the viewing hole on the index card along the

edges. Do not put tape OVER the hole or small slit.

electrOMagneticSpectruMScientists learn much about the world

by splitting things apart. A geol-

ogist can split rocks, a botanistcan split seeds, and a physicistcan split atoms. About the only

thing an astronomer can split is a beamof light, but even that reveals a greatdeal from the temperature of a starto the final moments of matter fallinginto a black hole.

Our eyes perceive the light from astar as a single color. But instrumentssplit the light into its individual wave-lengths or colors. The intensity of eachwavelength tells astronomers how hotthe star is, what its made of, how itsmoving, and whether it has compan-ions, like other stars or even planets.

Visible light is just one of the formsof energy that make up the electromag-netic spectrum. Other forms includeinfrared and radio waves, which havea longer wavelength than visible light,and ultraviolet, X-rays, and gammarays, which are shorterthan light.

Telescopes on the ground or in spacedetect these forms of energy and split

them into theircomponent wavelengths,too. Each type of energy tells us aboutthe environment in which it was cre-ated. Infrared, for example, comes fromrelatively cool objects like gas cloudsand planets. And X-rays come fromsome of the most violent objects in theuniverse, like disks of hot gas spiralinginto black holes.

By splitting each form of energy,astronomers build a more completeunderstanding of the universe onewavelength at a time.

Spectroscope

2.5 inpapercli

slit

punched

holes3 in

For class:

Incandescent light bulb (60-

100-watt frosted) and base

String of clear holiday lights

(optional)

Fluorescent light (single bulb)

Transmission grating sheet

(available from science supply store)

2 transparency sheets

Glo-Doodler

(available from Colorforms)

For each spectroscope:

Half of a manila folder

Sheet of black paper

3 index cards (3x5-inch size)

Tape or rubber bands

Scissors

A small paper clip

Hole puncher


aired in July 2004. Script by Damond Benningfield,

2001, 2004.


25/40S TARD ATE/ UN I V ERSO T EACHER GU I D E 25

ACTIVITYENGAGEDistribute individual grating cards to the students. Let them look around

the room. You may wish to have a light bulb (e.g. 60- 100-watt frosted

bulb) or string of holiday lights available.

EXPLOREWith gratings in hand, ask students to look at an incandescent light

source (light bulb with a filament) through the grating while holding it

close to their eye.

ASKSTUDENTS

Where does the spectrum appear?Spectra appear to the right and left of the light source.

What is the color order?

Violet is closest to the light source and red is most distant.

What could be done to improve the appearance or view of the spectrum?

Darken the room.

The grating is part of a spectroscope. As the students noticed, spectra are

best viewed against a dark background. Ask for alternatives to darkening

the room. If necessary, hint at something hand-held, since this instrument

should be portable. If no one mentions it, suggest that a tube, with the grat-

ing fixed at one end, will block stray light from the view of the spectrum andprovide the structural support for the spectroscope components.

What could you use to block out the stray light to make a dark back-

ground for viewing spectra?

Attach the grating to one end of a tube. Cut a manila folder in half along

the fold. Place a black sheet of construction paper on top of the manila

folder half. Roll them together along the long side so that the black paper

lines the inside of the tube. Secure with rubber bands or tape.

Attach the grating card to the tube (see figure, right). Fasten a paper clip

to one end of the tube, leaving a bit of the clip end over the tube edge. Fas-ten the grating card to the paper clip and secure with a folded card strip.

Have the students look at the incandescent bulb through the tube (with

the grating end next to the eye). The tube should aim directly at the bulb;

the students may need to move their heads to one side to see the spectrum.

Turn off the incandescent bulb and turn on a single fluorescent

bulb. Does the spectrum of the fluorescent bulb look like that of the

incandescent bulb? What is the same or different? (Students should see

a continuous spread of color in both bulbs spectra. They also may see

separate bands of color only in the fluorescent bulb spectrum.)

Finished spectroscope

Paper Clip

Grating card

FoldedStrip


Content Standard in 9-12 PhysicalScience (Interactions of energyand matter)

Content Standard in 9-12 Earthand Space Science (Origin andevolution of the universe)

Content Standard in 9-12 Scienceand Technology (Abilities oftechnical design)

sandwich spectrumspectrum



Cover up part of the fluorescent light bulb so that a narrow slit of light is

seen. Try making a slit in a double-thick manila folder and holding it in

front of the fluorescent source. Compare the incandescent light and the

fluorescent light. Do you see color bands now in one of the lights? Which

one?

Color bands appear dimmer and thinner with the slit in place for the fluorescent

bulb. The incandescent bulb has no bands.

Which observing method renders the best detail view of the spectrum fea-

ture with or without the slit?

With the slit. There is a limit if the slit is too narrow, the spectrum appears

too faint.

Where is a better place to put the slit, so that an observer can view other

light sources?

At the opposite end of the tube.

Make an adjustable slit from two index cards. Cut identical rectangular

slots, about 1x3 cm, into the center of two index cards. Stack the cards

then fold both cards together along both long sides. The cards

should now slide across each other. Adjust the size of the slit

by sliding one slot over the other.

Hold the adjustable slit at the opposite end of the tube from

the grating and open and close it until you find a position that

shows detail and still allows enough light through to see the

spectrum clearly. Rotate it if necessary so that the spectrum

has its largest height. This insures the parallel grooves in the grating run

in the same direction as the slit.

Congratulations! You have constructed a working spectroscope.

EXPLAINThis is a transmission grating. Its surface is scored or etched with thou-

sands of parallel grooves per centimeter. As light travels through the nar-

row grooves, diffraction effectively turns each groove into a new source

of light. As the light spreads out, it interacts or interferes with light of the

same wavelength from other grooves. Sometimes the light waves reinforce

each other (constructive interference), other times they cancel out and

become invisible (destructive interference). Collectively, the constructive

interference pattern directs a particular color along a unique angle from

the grating. The result is a color spectrum. Thats why blue light appearsclosest to the image of the source, while red is farthest away. Along those

angles, the constructive interference for that color lines up.

The tube blocks stray light that washes out details in the spectrum.

Against the dark background, subtle details of the spectrum are easily

seen. It also acts as a structure to attach the grating. The slit allows the

wavelengths (colors) of light to be resolved. The diffraction grating is

allowing you to see images of the slit side by side. The narrower the slit,

the more detail you can see. For instance, a narrow slit may resolve a pair

of lines in what appeared as a single emission feature viewed through a



TECHNICALNOTESFORCHEMISTRY/PHYSICSTEACHERS

This activity fits well with yourexploration of atomic structure,

spectra of various elements, howspectra vary for isotopes, andKirchhoffs laws.

wide slit. But as the slit narrows, less light passes through. So an observer

must strike a balance between the spectrums resolution and brightness.

The incandescent light has a hot filament which produces a continuous

spectrum (hot liquids also produce continuous spectra). The fluorescent

light is made of a tube of hot gas which produces an emission spectrum

more energy is released at certain wavelengths than at others so those

colors are more distinct. Which wavelengths are produced depends upon

the nature of the gas within a tube. Each gas has its own fingerprint or

pattern of wavelengths. In a fluorescent light, the gas is mercury.

[For some grade levels, the above explanation is too technical; the teacher may

wish to demonstrate constructive and destructive interference with water

waves.]

EXTENDTurn on the incandescent light and hold up the Glo-Doodler in front of it.

Ask students to describe how this spectrum is different from that of thebulb by itself or from the f luorescent bulb. (The Glo-Doodler absorbs cer-

tain wavelengths, which show as black bands in the spectrum.)

Think of a safe way to view the spectrum of the Sun DONT LOOK AT

THE SUN DIRECTLY!! For instance, point the spectroscope at brightly lit

clouds or the full Moon (which shines by reflected sunlight). What type of

spectrum does the Sun produce? (The Sun produces an absorption spec-

trum. The Suns photosphere, the solar layer where the Sun radiates most

of its light, is cooler than deeper solar layers. The hotter, deeper layers of

the Sun act like the light bulb filament while the photosphere acts like the

Glo-Doodler. Atomic elements in the photosphere selectively absorb certain

wavelengths of light. The resulting spectrum shows the absorbed wave-lengths as diminished bands, or lines, as astronomers call them.)

Scientists use spectroscopes to safely explore any heated object, from the

surface of the Sun to a chemical heated by a flame. How could a scientist

determine what elements may exist in the Suns photosphere? What pro-

cess would you suggest?

The spectroscope that the students construct in this activity does not allow

for direct measurement of wavelengths. Based on their knowledge of spec-

troscope construction and their observations of spectra, ask students how

they would improve their spectroscope. Could it allow an observer to mea-

sure the wavelength as they view a spectrum through the spectroscope?They should include a procedure for calibrating the wavelength scale.

EVALUATEGiven a diagram of a scientific spectrograph or spectroscope, identify the

main parts: slit, tube, and grating or prism. Early spectroscopes used a

prism instead of a grating.

A portion of our Suns spectrum revealsdark lines representing specific elementspresent in the Suns atmosphere.

N O A O / N S F



STUDENTPAGEA galaxy is a gravitationally bound system of stars, gas, and dust. Gal-axies range in diameter from a few thousand to a few hundred thou-sand light-years. Each galaxy contains billions (109) or trillions (1012)

of stars. In this activity, you will apply concepts of scale to grasp thedistances between stars and galaxies. You will use this understandingto elaborate on the question, Do galaxies collide?

EXPLOREOn a clear, dark night, you can see hundreds of bright stars. The next tabl

shows some of the brightest stars with their diameters and distances from

the Sun. Use a calculator to determine the scaled distance to each star

(how many times you could fit the star between itself and the Sun). Hint:

you first need to convert light-years and solar diameters into meters. One

light-year equals 9.46 x 1015meters, and the Suns diameter is 1.4 x 10 9

meters.

Star(Constellation)

Diameter(Sun=1)

Distance(light-years)

Scaled Distance(distancediameter)

Spica (Virgo) 8 261

Betelgeuse (Orion) 600 489

Deneb (Cygnus) 200 1,402

Altair (Aquila) 2 17

Vega (Lyra) 2.7 26

Sirius (Canis Major) 1.6 8.6

There are three galaxies beyond the Milky Way that you can see without

optical aid: the Andromeda galaxy, the Small Magellanic Cloud, and the

Large Magellanic Cloud. Figure the scaled distance to these galaxies (how

many times you could fit the galaxy between itself and the Milky Way).

Galaxy Diameter(light-years)

Distance(light-years)

Scaled Distance(distancediameter)(no conversion needed)

Milky Way 100,000 0

Andromeda Galaxy 125,000 2,500,000

Large Magellanic Cloud 31,000 165,000

Small Magellanic Cloud 16,000 200,000

EXPLAINHow does the scaled distance of galaxies compare to stars?

ELABORATEDo you think galaxies collide? Why or why not?

Stars and GalaxiesSeeingintOthepaStWe cant travel into the past, but we

can get a glimpse of it. Every

time we look at the Moon, forexample, we see it as it was alittle more than a second ago.

Thats because sunlight reflected fromthe Moons surface takes a little morethan a second to reach Earth. We seethe Sun as it looked about eight minutesago, and the other stars as they were afew years to a few centuries ago.

And then theres M31, the Androm-eda galaxy the most distant objectthats readily visible to human eyes.This great amalgamation of stars standsalmost directly overhead late this eve-ning. When viewed from a dark sky-watching location, far from city lights,it looks like a faint, fuzzy blob. But thatblob is the combined glow of hundredsof billions of stars seen as it lookedmore than two million years ago.

Andromeda is like a larger version ofour own Milky Way galaxy. Its a flatdisk that spans more than a quarter-mil-lion light-years. Its brightest stars formspiral arms that make the galaxy look

like a pinwheel. Yet the galaxy is sofar away that its structure is visible onlythrough telescopes.

The light from M31 has to travelabout two and a half million light-yearsto reach us about 15 quintillionmiles the number 15 followed by18 zeroes. Yet even across such anenormous gulf, the galaxy is so brightthat we can see it faintly with ourown eyes, crossing high overhead latetonight.


that aired October 14, 2006. Script by Damond

Benningfield, 2006.



TEACHERLESSONKEY

OBJECTIVES

Calculate scale distances of stars and galaxies.

Compare neighboring galaxies to neighboring stars.Understand the relative distances between objects in space.

ENGAGEFind a round object in the classroom that is about 2 to 5 inches in circum-

ference (such as a water bottle, tennis ball, or soda can). We will use a tennis

ball as an example. Using a table that everyone can see, ask the students,

How many tennis balls would it take to go from one end of this table to the

other? In other words, how many tennis balls across is the table? Accept all

answers. Then find the answer in front of the class by moving the ball across

the table one space at a time, counting each move out loud.

EXPLORE (ANSWERS)


Content Standard in 9-12 Scienceas Inquiry (Understanding aboutscientific inquiry)

Content Standard in 9-12 Earthand Space Science (Origin andevolution of the universe)

StarsTo convertDistance (ly) x 9.46 x 1015(m/ly)Diameter (Suns) x 1.4 x 109(m/Sun)

Scaled DistanceDistanceDiameter

(both must be in the same units,do conversions first)

Spica (Virgo) 2.22 x 108

Betelgeuse (Orion) 5.51 x 106

Deneb (Cygnus) 4.74 x 107

Altair (Aquila) 5.74 x 107

Vega (Lyra) 6.51 x 107

Sirius (Canis Major) 3.59 x 107

GalaxiesDistanceDiameter(no conversion needed)

Scaled Distancefrom Milky Way

DistanceDiameter(no conversion needed)

Milky Way ------

Andromeda Galaxy 20

Large Magellanic Cloud 5.32

Small Magellanic Cloud 12.5

EXPLAINHow does the scaled distance of galaxies compare to stars?

Galaxies, compared to their size, are much closer together than stars. Neigh-

boring stars are usually millions of star-diameters apart, while galaxies areusually less than 100 galaxy-diameters apart.

ELABORATEDo you think galaxies collide? Why or why not?

Galaxies do collide. They are relatively close to each other and they have thecombined mass of billions of stars. So even over large distances, the attraction

between galaxies can accelerate them toward each other. Thick of bowling balls(galaxies) versus sand grains (stars) on a trampoline (space). The galaxies stretch

and distort the trampoline much more, and over a wider area, than do single stars.Even though galaxies collide, the stars withingalaxies seldom collide becausethey are so far away from each other. Clouds of gas and dust in the galaxies docollide, though, giving birth to new stars.

EVALUATERubric: Explore = 60 pts (6 pts for each calculation), Explain = 25 pts,

Elaborate = 15 pts



In 2006, Hubble Space Telescope aimed at a nearby collection ofgalaxies called the Coma Cluster. Using the HST images, astronomersgained fascinating insights into the evolution of galaxies in densegalactic neighborhoods. In this activity, students will first learn thebasics of galaxy classification and grouping, then use HST images todiscover the morphology-density effect and make hypotheses aboutits causes.

MATERIALS& PREPARATION

Each student needs a copy of the next 7 pages (not this page). You may

copy the pages out of this guide, but it is recommended that you go to

mcdonaldobservatory.org/teachers/classroom and download the studen

worksheets. The galaxy images in the online worksheets are negatives

of the real images, which provides better detail when printing. Supple-

mental materials for this activity are also available on the website.

Each student or student team will need a calculator and a magnifying

glass (a linen tester works well).

Knowledge of percentages is needed before doing this activity.

SUGGESTEDGRADING

Page 31 (5 pts): Student provides clear explanations of the scheme.

Page 32 (2 pts total, 2 pts each): Answers: (E/S0/SB0 2,6,9), (S

1,8,12), (SB 3,4,10), (IR 5,7,11)

Pages 34 and 35: Not graded; based on students subjective interpreta-

tion.

Page 36 (30 pts): Graded for completion, not accuracy. Students will get

different numbers, but math should be correct. Answers for percentages

are typically in the following range: (Cluster: E 50 percent, L 30 percent,

S 20 percent) (Field: E 20 percent, L 10 percent, S 70 percent). Students

usually find a higher percentage of spirals in the field.

Page 37 (bottom, 30 pts): Student hypothesis should mention the

effects of interactions and ram-pressure stripping in changing past gas-

rich spirals into current gas-poor ellipticals and lenticulars in clusters.

Coma Cluster of GalaxiesNATIONALSCIENCEEDUCATIONSTANDARDS

Content Standard in 9-12 Science asInquiry (Abilities necessary to do sci-entific inquiry, Understanding about

scientific inquiry)

Content Standard in 9-12 Earth andSpace Science (Origin and evolutionof the universe)

inviSiblecluSterIf you aim a big telescope at the Coma

Cluster, youll see galaxies galore thousands of galaxies of all sizesand shapes, from little puffballs to

big, fuzzy footballs. Even so, you wont

see most of the cluster because its invis-ible to human eyes.

Some of the clusters dark side is inthe form of superhot gas that glows in X-rays. All together, the gas is several timesas massive as the galaxies themselves.

Theres a dynamic interplay betweenthe hot gas and the galaxies.

As galaxies fall toward the center ofthe cluster, they fly through the hot gas,which strips away the cold gas insidethe galaxies. Without their cold gas, the

galaxies cant give birth to new stars. Thathelps transform the appearance of someof the galaxies. Spiral galaxies lose theirspiral arms, so they look like featurelessdisks.

But the galaxies may have an effect onthe hot gas, too. Over the eons, it shouldhave cooled, but it hasnt. Hot jets ofparticles from the centers of some galax-ies may act like big blowtorches, keepingthe gas hot.

Yet even the gas and the galaxies com-

bined make up only a small fraction of theComa Cluster. As much as 80 percent ofits mass may consist of dark matter aform of matter that produces no detectableenergy, but that exerts a gravitational pullon the visible matter around it. The darkmatter ensures that most of this impressivecluster remains invisible.


aired May 6, 2008. Script by Damond Benningfield,

2008.



ENGAGEThe diagram above shows a mosaic of

40 galaxies. These images were taken

with Hubble Space Telescope and show

the variety of shapes that galaxies

can assume. When astronomer Edwin

Hubble first started studying these vari-

ous types of galaxies in the 1920s, he

realized he needed to develop a way to

organize and categorize them. He cre-

ated a classification scheme in which he

grouped similar galaxies together. Your

job is to do the same thing. In the chart,

invent your own four galaxy types and

provide a description and three examples

for each one.

Galaxy Type(name and draw)

Defining Characteristics(write a short description, provide enough detailso that anyone could use your scheme)

Three Examples(give 3 gridcoordinates)

G E M S C O L L A B O R A T I O N



EXPLOREThe image on the left is the classification scheme that Hubble himself

came up with. He thought that the tuning fork sequence represented th

evolutionary progression of galaxies. This concept turned

out to be wrong, although astronomers still use thesegeneral categories and labels to describe galaxies.

THEMAINGALAXYTYPES

Elliptical (E): Spherical or elliptical shape (like

a football), has no flat disc or spiral arms

Lenticular (S0): Smooth, flat disk shape with-

out spiral structure, often hard to distinguish

from ellipticals

Barred Lenticular (SB0): Same as above, but with an

elongated (barred) nucleus

Spiral (S): Flat disk shape with notable spiral patterns in

the outer disk, also contains a large bright

central bulge

Barred Spiral (SB): A special type of spiral

characterized by an elongated nucleus with

the spiral arms springing from the ends of

the bar

There are two other categories for classifying

galaxies:

Irregular (IR): An oddly shaped galaxy

that doesnt fit into any other category

Interacting (INT): Two or more galax-

ies that are so close together that they are

affecting each others shape

Using the definitions above, place the 12 gal

axies on the left into their proper morphol-

ogy categories:

Morphology Picture Numbers (3 each)

E/S0/SB0

S

SB

IR

The smallest galaxies are often called dwarf

galaxies (No. 5 and No. 7 are dwarf galax-

ies). These contain only a few billion stars

a small number compared to the Milky

Ways 200 billion. The largest ellipticals con

tain several trillion stars.

1 2 3

4 5 6

7 8 9

10 11 12

ORDIN

ARYSP

IRALS

BARREDSPIRALS

ELLIPTICAL GALAXIES

Boxy Disky SBO

SO

SBa SBbSBc

IBm

ImSa Sb

Sc

IRR

EGULARS

ESO(TOPRIGHT);ALLOTHERSNASA

JOHNKORMENDY/TIMJONES



THECOMAGALAXYCLUSTERThe Coma Cluster, which is centered about 320 million light-years away,

contains several thousand individual galaxies. The cluster has a roughly

spherical shape and is about 20 million light-years across. (For compari-

son, the Milky Way is 100,000 light-years across). That many galaxiesin a relatively small space makes the Coma Cluster one of the richest and

densest galaxy clusters in our region of the universe.

On the following pages you will be asked to count differenttypes of galaxies. Use the labels on this picture as an example

of how to count the various objects.

I) Ellipticals or Lenticulars

It can be hard to tell these apart. If you know its either an

E or S0/SB0, it is okay to

guess between these two.

II) Spirals and Barred Spi-

rals

It can be hard to tell these

apart. If you know its

either an S or SB, it is okayto guess between these two.

III) Irregular galaxy

IV) Uncertain

An edge-on view of a gal-

axy that could possibly be

an S0, SB0, S, SB, or IR.

There are too many pos-

sibilities, so do not count

these.

Star)

Any object that hascrosshairs sticking out of

it is a foreground star in the

Milky Way galaxy, so do not

count these.

?)

Dont count small, faint

objects like these that are

too hard to classify.

NWW

Arcturus

COMA BERENICES

BIG DIPPER

I ?

?

?

I

I

I

I

II

II

Star

II

I

I

IV III

??

II

II

Star

Star

IV IV

N A S A / S T S C I / C O M A H S T A C S T R E A S U R Y T E A M

( 3 )

T I M

J O N E S



E S0 /SB0 S SB IR / INT

Top Image (A)

Bottom Image (B)

Count the number of galaxies of each

morphological type and write down the

number in the correct spot in the table.

Use the guidelines on page 4 to help you

decide which objects to count.

A

B



E S0 /SB0 S SB IR / INT

Top Image (C)

Bottom Image (D)

Count the number of galaxies of each

morphological type and write down the

number in the correct spot in the table.

Use the guidelines on page 4 to help

you decide which objects to count.

C

D

NASA/STSCI/COMAHSTACSTREASURYTEAM(4)



EXPLAIN

Galaxies in Clusters, Groups, and the Field

Galaxies are found throughout the universe, from our next door neighbor

the Magellanic Clouds and Andromeda all the way out to the edge

of the visible universe 13 billion light years away. Nobody knows for sure,but it is estimated that there are 100 billion galaxies or more in the visible

universe, and many more beyond that. Galaxies live in a variety of envi-

ronments. Sometimes large numbers of them are packed close together in

clusters, such as the Coma Cluster; sometimes they gather in smaller num

bers called groups, like the Local Group that contains our Milky Way; a

stardate teacher guide 2008

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