TEACHER GUIDE Get Close to Mcdonald Observatory

TEACHER GUIDE Get Close to McDonald Observatory

Live and in Person Live for Students McDonald Observatory offers a unique set- The Frank N. Bash Visitors Center features ting for teacher workshops: the Observatory a full classroom, 90-seat theater, astronomy and Visitors Center in the Davis Mountains park with telescopes, and an exhibit hall of West Texas. The workshops offer inquiry- for groups of 12 to 100 students. These based activities aligned with national and programs offer hands-on, inquiry-based ac- Texas science and math standards. Teachers tivities in an engaging environment, provid- can practice their new astronomy skills under ing an informal extension to classroom and the dark West Texas skies, and partner with science instruction. Reservations are recom- trained and nationally recognized astronomy mended at least six weeks in advance. educators. mcdonaldobservatory.org/teachers/visit mcdonaldobservatory.org/teachers/profdev Live on Video Visit McDonald Observatory from the classroom through an interactive videoconference program, “Live! From McDonald Observato- ry.” The live 50-minute program is designed for Texas classrooms, with versions for grades 3-5, 6-8, and 9-12. Each program is aligned with Texas education standards. mcdonaldobservatory.org/lfmo F rank Cian c iolo (inset)

For complete details 432-426-3640

mcdonaldobservatory.org/teachers d Benningfiel d ; Damon Table of Contents

TEACHER GUIDE To the Teacher 4 Resources 38

5th Edition

Staff Classroom Activities

eXECUTIVE EDITOR Damond Benningfield EDitor rebecca Johnson Shadow Play 6

ART DIRECtor tim Jones K-4 CURRICULUM SPECIALISTS Dr. Mary Kay Hemenway kyle Fricke Brad Armosky CIRCULATION MANAGER Paul Previte r a d e s G DIRECTOR, PUBLIC INFORMATION Sandra Preston Modeling the Night Sky 8 Special thanks to all the teachers who evaluated this guide. Observing the Moon 11

Front Cover A Hubble Space Tele- T eam scope view of a swath

of the Coma Cluster, a T reas u ry

C S Planet Tours 14 collection of thousands A of galaxies. Astrono- mers are studying Solar System Science 15 5-8

Coma to learn about I /Coma H ST c the evolution of galax- Rock Cycle 16

ies in clusters. r a d e s NASA / STS Equatorial Sundial 18 G Back Cover With Earth looming in the background, astro- Scale Models 20 nauts service Hubble Space Telescope in the cargo bay of space shuttle Discovery.

Support for Program number HST-EO-10861.35-A was provided by NASA through a grant from the Space Telescope Science Institute, which is oper- Sunspots 22 ated by the Association of Univer- sities for Research in Astronomy, Incorpo- Spectroscope 24 rated, under NASA contract NAS5-26555. Stars and Galaxies 28 9-12 r a d e s The StarDate/Universo Teacher Guide is published by the McDonald G Observatory Education and Outreach Office, 2609 University Ave. Coma Cluster of Galaxies 30 #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 change of address to StarDate, The University of Texas at Austin, 1 University Station, A2100, Austin, TX 78712. Periodicals Postage Paid at Austin, TX. StarDate and Universo are trademarks of the University of Texas McDonald Observatory.

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

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 3 To the Teacher

tarDate and Universo are daily of the radio program content while may be distributed to other teach- radio programs that transport providing some idea of how these ers, placed in your school’s library, or Slisteners into the universe. and similar programs may be incor- used for other educational Many of the programs point out porated into lesson plans. purposes. However, interesting events or objects in StarDate and Universo provide the copies may not the night sky, with details on the additional resources through be sold or otherwise underlying science. Other programs World Wide Web sites in both distributed for non- cover the history of astronomy and English and Spanish. These sites educational uses. space exploration, upcoming mis- provide extensive information sions, recent discoveries, and relat- on the solar system, stars, Listening Skills ed topics. galaxies, and other sci- StarDate and Univer- Radio stations receive the programs ence topics, as well so provide an opportunity on monthly compact disks, and these as daily, weekly, and for students to improve their same monthly CDs are made avail- monthly skywatching listening skills. Teachers who able to teachers around the country. tips. Web addresses for preview the daily program Hundreds of teachers incorporate these and other sites may ask questions the programs into their classroom are provided at the back about the program to instruction. of this publication. help students focus The StarDate/Universo Teacher We occasionally produce on the topic. Written Guide can help you integrate Star- printed guides, posters, or other scripts are available Date and Universo programs into resources as well. These resourc- on-line each day your daily classes. We have provided es are distributed to the through the Star- simple activities for several grade lev- teachers who receive the Date Online and Uni- els, most of which require no elabo- audio CDs. verso Online web sites. rate equipment. These activities are Some teachers broadcast the examples upon which to build similar StarDate/Universo program over the school inter- lessons based on current StarDate and Your com each day. and Universo episodes. You can inte- Classroom grate and apply new skills from other Each CD contains a full Note-Taking and Discussion subject areas as you broaden stu- month of either StarDate To go beyond passive listening, dents’ awareness of astronomy. or Universo programming. have your students take notes. Some A transcript of a related StarDate You can integrate the information teachers have found that students are radio program accompanies most from the programs into daily learn- more prepared to discuss the topic if activities. The scripts are boxed and ing experiences in your classroom in they listen, take notes, then listen a denoted by a small radio transmitter a variety of ways. You are free to copy second time to check their notes. logo. The scripts show the breadth the CDs for educational uses. Copies Extending Class Lessons With their emphasis on objects in the sky, StarDate and Universo are Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s great sources for homework assignments. For this reason, some teachers Each activity in the StarDate/Universo Teacher Guide meets the National play StarDate or Universo at the end Science Education Standards (NSES), which were developed with these of class as they make an assignment. guiding principles: • Students can keep observing logs to record their observations throughout • Science is for ALL students. the year. Their StarDate or Universo • Learning science is an active process. notes prepare them to go outside and • School science reflects traditions of contemporary science. sketch what they see. • Improving science is part of systemic education reform. • Create a resource station where The NSES promote not just hands-on science, but also minds-on science. students file information they have gathered from the programs. Stu- The astronomy context of these activities aligns their content with the dents may file their own drawings, NSES “Physical Science” and “Earth and Space Science” standards. The data, and papers as well. Keeping “Science as Inquiry” standards manifest in the structure and format of your copies of the CDs and a CD the activities. Some activities overlap grade levels; many teachers will player with earphones will allow stu- find ways to modify the activities to fit the level of their students. dents to listen individually to selected programs. Students may create a

4 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e database of the information filed at on skylore to create interest in our solar sys- the resource station. Some teachers mythology and ancient civiliza- tem. They can use this station as a reference source tions. estimate times for assignments. • Have students keep a StarDate and relative dis- or Universo journal with their tances. Bilingual Instruction summaries of the programs and • Older students Universo can help you meet the answers to the pre-listening can apply princi- needs of Spanish-speaking students questions. Journal entries may ples of geometry or students who are learning Span- consist of phrases, sentences, and trigonometry ish. paragraphs, or drawings to as they explore • Have Universo CDs available at a illustrate the core concept. the angles and listening station. Use the programs to • Encourage students to orientations of introduce the lessons and vocabulary think on a large scale. planets and satel- to bilingual students before the les- For example, in teach- lites or the position son in English. ing a unit on Thoreau, of the Sun or Moon in the sky throughout the • Have students who need support ask them to consider the day or year. in Spanish listen to the programs to vastness of the universe, review concepts taught in English. using the radio shows to spark abstract thought and Fine Arts • Encourage Spanish students to listen prepare them for existential • Encourage students to Universo programs. The written literature. to make drawings of text (in Spanish) may be printed for their concepts related them to follow. For some programs, • Use the scripts from the StarDate or Universo web to the programs. For students can check their comprehen- example, if the pro- sion by listening to or reading the sites and material from Star- Date magazine as supple- gram is about sunsets, English version of the program after they can draw their ideal they hear the Universo program. mental reading materials. • Encourage students to explore the sunset, which might lead into a dis- historical context and relevance of cussion of the Sun’s color and why it Cross-Curriculum Connections the events and lives appears redder at sunrise and sunset. You can incorporate of the astronomers Or, for a program about space flight, StarDate and Univer- described in StarDate students might draw a spacecraft vis- so into many subject and Universo pro- iting another planet or a comet. areas, including: grams. • Astronomy-related music has been • Use the programs to popular for centuries. Your students Language Arts and may be more familiar with John Wil- Social Studies explore the cultural perspectives relating liams’ score for “Star Wars” than • Use the programs to astronomy and to Holst’s “The Planets,” but both pieces teach about the impact can be used as a trigger for combin- of celestial ing their ideas about astronomy with events on cul- music. tural develop- ment. Individualized Learning Because StarDate and Universo top- Mathematics ics range from basic to more complex concepts, you can use them with stu- • Students can dents of all ages and ability levels. use graphs and charts during • With a copy of the program’s script, the skywatch- students can highlight key concepts ing activities and challenging words as they listen in this guide. to the program. They can apply • Have students visit StarDate Online concepts of or Universo Online as an enrichment proportion and activity. They can search the web site percentage as for answers to their astronomy ques- they compare the sizes of planets or tions or read the daily Frequently the distances between planets within Asked Question.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 5 Shadow Play

Everyone and everything has a shadow. Shadows illustrate how three- dimensional objects can be viewed in two dimensions. Younger Su n w atc h e r s students can learn about the Sun’s relative motion in the sky as they Until well into the last century, one of experiment with shadows. the most important people in the pueblos of the southwest Mat e r i a l s was the Sunwatcher. Each day, • Chalk he watched the Sun rise, using • Outdoor drawing area hills or other objects to track its motion along the horizon. His observations • Lamp told the tribe when to plant or harvest • Globe (a large globe is preferable) crops, and when to conduct important ceremonies. • Tape The Sunwatchers may have been • Action figure (3 inches or smaller) carrying on a tradition established by some of the ancestors of the pueblo ACTIVITY ONE people — the Anasazi, a Navajo name that means “the ancient ones.” Begin by asking, “Where is the Sun They built a large, well-ordered civi- at noon?” Depending on the lization in the Four Corners region a age of the child, responses millennium ago. might be “straight up,” “in Archaeological sites at several Ana- the sky,” “overhead,” or “in sazi villages suggest that they watched the south.” Ask, “What is a the Sun carefully. One example is the shadow?” Accept responses. Sun room in Hovenweep Castle, a ruin in southeastern Utah. Doorways and Pr e pa r at i o n windows in the room align with the sun- Divide the class into teams of two or three before going outside. set on the summer and winter solstices Ex p e r i m e n t — when the Sun appears farthest north Begin in the morning. One member is to play “statue” — holding still and south in the sky — and the equinoxes, when it’s half-way between. while the other team members trace the outlines of both the statue’s feet and shadow on the pavement. When all the tracings are completed, the Nearby, a pair of buildings atop entire class can examine them. Wait about 30–60 minutes, then ask the Cajon Mesa apparently served as a solar calendar. Sunwatchers kept track “statues” to return to their places (which is why they traced their feet) and of the Sun’s motion from a series of hold the same position again. windows. They also used the shadows An a ly s i s of the two buildings to determine the What has changed? arrival of the solstices and equinoxes. The most famous Anasazi sunwatch- An s w e r ing sites are in Chaco Canyon, in Students should notice that the northwestern New Mexico. In fact, length and position of the shad- quite a few people are visiting the can- ow have changed. Younger chil- yon this week to watch the sunrise on dren may think that the “statue” the summer solstice. changed position. Ask them to predict where the shadow will be in three hours. Repeat the tracings about once per hour This is the transcript of a StarDate radio episode that until the end of the school day. aired June 19, 2001. Script by Damond Benningfield, ©2001. 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 doesn’t pass directly overhead at noon (unless you live between the tropics). Depending on the grade, students may

6 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e measure the lengths of the shadows or even graph the length versus time of day. Discuss the results. Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s • Content Standard in K-4 Earth ACTIVITY TWO Science (Objects in the sky, This activity demonstrates the daily motion of Earth. We perceive the Sun Changes in Earth and sky) as rising, crossing the daytime sky, and setting. It is actually Earth that • Content Standard in K-4 Science moves. as Inquiry (Abilities necessary to Pr e pa r at i o n do scientific inquiry) Inside 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 Earth’s motion.) De m o n s t r at i o n To 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 Earth’s annual motion around the Sun. Don’t try to spin and walk at the same time; it takes 365.25 spins to make a year!) An a ly s i s What has changed? An s w e r When children are facing the lamp, it is day. When they are facing away from the lamp, it is night. ACTIVITY THREE Pr e pa r at i o n Inside the classroom, demonstrate the connection between the first two Light bulb 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 globe’s spin axis tilted relative 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). Ex p e r i m e n t Darken the room and spin the globe so that everyone can see a change in the length and position of the figure’s shadow. An a ly s i s How does the figure’s shadow compare to the childrens’ shadows outside? An s w e r The behavior of the shadows should be similar. Spinning the globe counterclockwise when looking down on the north pole will show the proper move- ment of the shadow from west to east. Ex t e n s i o n Students draw pictures of why we have day and night. Students study how ancient people created stories about what causes day and night.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 7 Modeling the Night Sky

Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s Pr e pa r at i o n Each individual or group needs one copy of the constellation strip on page • Content Standard in K-4 Earth 9. The teacher needs individual constellation pictures and cards with the and Space Science (Changes in names or pictures of the following objects: Sun, Earth, Mercury, Mars, and Earth and sky, Objects in the sky) Jupiter. Allow each group of 2-3 students to glue or tape the strips togeth- • Content Standard in 5-8 Earth er, matching the letters on the edges of each strip, A:A, B:B, C:C, and D:D. and Space Sciences (Earth in the That will form a loop with the constellations in this order: Gemini, Taurus, solar system) Aries, Pisces, Aquarius, Capricornus, Sagittarius, Ophiuchus, Scorpius, • Content Standard in K-4 Physical Libra, Virgo, Leo, and Cancer. Ask students if they recognize any of the Science (Position and motion of pictures. Some students may wish to color the pictures. objects) Activity 1 Place the loop so that the pictures face inward. Distribute two small balls This activity extends “Shadow Play” (such as clay or marbles). Ask the students to place one ball to represent (page 6) to include more solar system the position of the Sun in relation to the constellations. Then ask them objects and to examine their motions. to place the other ball where they think Earth should be in relation to the Sun and the constellations and to explain to their partners why they chose that position. Ask the students to identify which side of Earth will be day Although Ophiuchus (oh-fee-YOO'-kus) is not and which side will be night. When the Sun is “in” a certain constella- a traditional constellation of the zodiac, the tion (that is, standing on Earth, if you had the ability to see stars in the daytime, which constellation would be behind the Sun), what constella- Sun passes through its borders in December. tion is seen at midnight? Your interactions will depend upon the student In one year, the Sun passes through 13 responses. If they place Earth rather than the Sun in the center, ask them constellations. In classical mythology, Ophi- to explain. For now, accept all answers. uchus was known as the serpent bearer. Ancient peoples tracked which constellations appeared in the direction of the Sun. They usually watched the sky near sunrise. For this model, the Sun is in the middle and Earth goes around it (counterclockwise as seen from the north pole). The stars are very distant compared to the Earth-Sun distance.

Activity 2 Cut each figure out of one strip and paste it on an individual card. Pass the cards out to 13 students, who stand in a circle facing inward. (For a small group, post the cards on backs of chairs to make a circle.) Make sure they follow the same order as the loop. Choose one student to be the Sun and stand in the middle of the circle. Allow another student to individually model Earth’s motion throughout the year, recalling that the direction of rotation and revolution are the same. For Earth, one turn around the Sun takes one year. (Although rotation can be considered simultaneously, remember that Earth rotates in 24 hours, and anyone who spins 365 times as they “orbit” the Sun will become dizzy!) As an extension, you may wish to include Earth’s tilt. Choose a spot above Gemini on a distant wall to be Polaris and tell “Earth” to always bend in that direction as it orbits the Sun. Activity continued, Page 10

8 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e A D

Gemini Taurus Aries C D

PISCES AQUARIUS CAPRICORNUS C B

SAGITTARIUS OPHIUCHUS SCORPIUS LIBRA A B

Virgo Leo Cancer

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 9 Op h i u c h u s a n d Se r p e n s We see different stars at different times of year because Earth orbits Two constellations that don’t (revolves around) the Sun. Some constellations are small, while others are get a lot of respect are in the large. The Sun appears to move from one constellation to another in as few southwest this evening, above as 6 days or as many as 43. the Moon and the bright planet Jupiter. One of them is slighted by any- Add more celestial objects to your model by handing planet cards to more one who can name the 12 signs of the students. These objects orbit the Sun like Earth, but at different rates. This zodiac. The other was slighted by the people who established the constella- works best if they come in one at a time, each with their own rate of orbit- tion boundaries: they chopped out its ing the Sun. The following table recommends some approximations to use, middle. along with the exact values, for periods of revolution (the time it takes The constellations are Ophiuchus, for the object to revolve around the Sun one time). Distance scales are the serpent bearer, and Serpens, the not preserved in this activity. For example, tell the students that Mercury serpent. orbits the Sun four times in one Earth year. So the person who represents Ophiuchus is one of the largest con- Mercury has to race around the Sun four times while Earth goes around stellations. More important, it lies along only once. Some students will count this out. For younger students, draw- the ecliptic — the Sun’s path across the ing the circles on the floor helps them maintain the proper distances. Stop sky. The constellations along this path occasionally to ask, “If you are on Earth, where or when can you see that form the zodiac. But Ophiuchus isn’t object?” Add more or fewer objects depending upon the age of the group. included in the lineup, even though the For older students, model sunrise/sunset and ask what objects are vis- Sun spends more time inside its borders ible in the sky at various times of day (just after sunset or at midnight, than in Scorpius, which is next door. for example) and in which constellations they appear. If you have already Ophiuchus represents the founder studied phases of the Moon (see “Observing the Moon,” page 11), it can of medicine. In myth, he was such a be inserted into this model, orbiting Earth in about one month while Earth good healer that he even brought the orbits the Sun in one year. dead back to life. That was reminiscent of the powers of a snake: It can kill, but it also rejuvenates itself every year Object Approximate period Actual period when it sheds its skin. So in the sky, the physician is also known as the serpent Mercury 1/4 year 0.24 year = 88 days bearer. Earth 1 year 1 year = 365.25 days Moon 1 month 27.3 days Appropriately enough, he’s holding Mars 2 years 1.88 years on to Serpens. The serpent’s head is to the west of Ophiuchus, with the tail Jupiter 12 years 11.86 years to the east — severed by the body of Ophiuchus. Ev a l u a t e Serpens and Ophiuchus are well up in the southwest at nightfall. Look for the • The asteroid Ceres has a period of 4.6 years. Where would it go in this crescent Moon quite low in the sky, with scheme? (Answer: between Mars and Jupiter.) brilliant Jupiter and the bright orange • Why did we not include Venus (0.61 year), Saturn (29.42 years), Uranus star Antares to its upper left. Ophiuchus (83.75 years), or Neptune (163.73 years)? (Answer: 0.61 years would and Serpens stretch out above this be difficult to model and adding Venus would make it crowded. The other bright trio. 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. This is the transcript of a StarDate radio episode that aired September 17, 2007. Script by Damond Benningfield, ©2007. Teaching note: Although this activity does not indicate relative distances, 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.

10 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Observing the Moon

Does the Moon always look the same? Does its surface look different at different times? What will your students say when you ask them Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s these questions? • Content Standard in K-4 Earth and Space Science (Changes in Earth Many students are aware that the Moon goes through phases, but and sky, Objects in the sky) except for the “man in the Moon” — which many admit they have a hard time seeing — they probably haven’t thought about the surface • Content Standard in 5-8 Earth and of the Moon and how we view it from Earth. Some students may men- Space Sciences (Earth in the solar tion that the Moon changes colors. It actually doesn’t — the Moon’s system) color changes due to the effects of our own atmosphere, not anything • Content Standard in 5-8 Science intrinsic to the Moon. as Inquiry (Abilities necessary to do scientific inquiry) Mat e r i a l s • Clear skies • Binoculars • Notebook • Chart on page 13 • Soft drawing pencil

Pr e pa r at i o n First, figure out when you can see the Moon. Use the StarDate Sky Alma- nac or a calendar to find the Moon’s 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 activity, it really isn’t. “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. That’s 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- G ianforte

tinct shadows and become more noticeable. Jo h n Lunar eclipse Once you know the Moon’s phase, the chart provided here will help you decide the best time of day (or night!) for lunar viewing. Ac t i v i t y Draw 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 light and 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. Phase New First Quarter Full Last Quarter Binoculars will allow you to see a lot more detail. At another phase Rise Sunrise Noon Sunset Midnight (at least five days later), repeat the Highest in Sky Noon Sunset Midnight Sunrise activity. Set Sunset Midnight Sunrise Noon

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 11 An a ly s i s Compare the naked-eye and binocular drawings done on the same date with Fu l l Ea r t h each other. What details are visible? Can you identify any features from the The Moon is AWOL right now. It pass- lunar map? Now compare the drawings from one date to the other. es between Earth and the Sun early tomorrow, so it’s hidden Ex t e n s i o n in the Sun’s glare. And even if For an in-class activity, make craters by dropping marbles or pebbles into a the Sun wasn’t in the way, there deep basin of flour sprinkled with dry chocolate milk mix. You should get wouldn’t be much to see: It’s night on nice craters with elevated edges, and some with a series of splashed out the lunar hemisphere facing our way, materials centered on the crater. In a darkened room, shine a flashlight so the entire disk is dark. onto the cratered surface and show how the angle of the flashlight deter- Well, almost dark. The Sun is shining mines the length of the shadows. Students can research the surface of the on the far side of the Moon, so it’s not Moon in the library or on the Internet. lighting up the side that faces Earth. But the side that does face Earth is getting As a math extension, calculate the angle between the Sun and Moon for some sunshine — reflected off of Earth. different phases. We can see this “earthshine” when there’s a crescent Moon in the sky, For English, write a poem about the Moon. because it makes the dark portion of the lunar disk look like a gray phantom. Right now, the earthshine is at its most intense. That’s because there’s a full Earth in the lunar sky. Earth covers an area more than 13 times greater than the Moon does. And on average, each square mile of Earth’s surface reflects more than three times as much sunlight back into space. So a full Earth is about 40 times brighter than a full Moon. While a full Moon always looks the same, a full Earth is constantly changing. Anyone standing on the Moon would see the entire surface of Earth as our planet turns on its axis. So they’d see different continents and oceans, plus the unceasing motions of clouds in the atmosphere. And since the same side of the Moon always faces Earth, our planet would always appear in exactly the same spot in the sky — a bright blue and white ball spinning in the sunlight. Above: Impact craters and volcanic valleys on the lunar surface. Right: An Apollo 15 astronaut salutes the flag. This is the transcript of a StarDate radio episode that aired May 7, 2005. Script by Damond Benningfield, ©2005. NASA ); p ); J A X / N H K (to

12 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Le a r n i ng t h e Lu n a r La n d s c a p e

Bay of Dew Sea of Cold Plato

Sea of Rains

Aristarchus Archimedes Sea of Serenity Sea of Crises Sea of Sea of

Kepler Vapors Tranquility JP L / TIM J ONES Copernicus Ocean Taruntius of Sea of Sea of Storms Sea of Fertility Nectar Langrenus

Sea of Sea of Moisture Clouds

Tycho

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 13 Planet Tours

Planning to take a vacation soon? Visit Phobos! Small and cozy, Pho- Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s bos orbits the fourth planet from the Sun in less than eight hours. • Content Standard in 5-8 Earth and From your observation deck on Phobos, you will have a superb view Space Science (Earth in the solar of Mars. You will see its mountains, polar ice caps, and the largest vol- system) cano in the solar system. Call your cosmic travel agent today! • Content Standard in 5-8 Physical Try this creative activity to help your students explore the solar system Science (Properties of objects and in an imaginative manner. materials) Pr e pa r at i o n oo n a n d u p i t e r Use StarDate or Universo CDs or printed materials such as StarDate: The M J Solar System or the StarDate/Universo websites to find information about On the scale of our everyday lives, solar system objects. As an aid, provide some examples of real travel bro- Earth is a big place. It’s so big, chures or websites with travel ads available for students to preview. For in fact, that an airliner, flying secondary classrooms, a good resource is Active Physics: Sports by Arthur nonstop, would take about two Eisenkraft (ISBN 1-891629-04-02). days to circle its equator. But our planet is tiny compared to Jupiter, Ac t i v i t y the giant of the solar system. It’s 11 Break the class into teams that will research one planetary body (if you times bigger around than Earth is, so have a large number of teams, you can include some of the moons of the that airliner would need about three solar system, or comets and asteroids). The students use the information weeks to circle Jupiter’s equator. they collect to create travel posters, brochures, or television or radio com- And the sights out the window would mercials for their object. be spectacular. Jupiter doesn’t have a solid surface, Each project should include real facts about the solar system object, but so you wouldn’t see any mountains, may use “far-out” features to form the basis of unusual recreation oppor- deserts, or oceans. But the Jovian atmo- tunities. When everyone is finished, each team presents its product to the sphere is filled with giant storms, and with belts of clouds that race around the rest of the class. planet at hundreds of miles an hour. As s e s s m e n t To avoid turbulence, you’d have to Develop a grading rubric for dif- go around the biggest storm systems. ferent grades, keeping in mind the That could add days to the trip, though, standards. In addition to “facts” because the storms can be as big as about solar system objects, the rubric Earth. And they produce lightning bolts should ascertain whether students that are hundreds of times as powerful as those on Earth. At night, such blasts use physical data to make compari- might be visible for thousands of miles. sons. Making comparisons is the key to learning science in this activity. Different chemicals in the atmosphere add color to the clouds, so you’d see Some teachers may be comfortable shades of yellow, brown, and red with allowing the students to design mixed with the white clouds that’re the rubric for their class after they made of water vapor. have started the project; others may And if you’re afraid of heights, you want to pass the rubric out at the wouldn’t want to look down: the cloud beginning of the assignment. One layers atop the Jovian atmosphere are teacher had students make Power- scores of miles thick, so it would be a Point presentations and gave extra long way down. credit for working some mythology

and images into the presentation. NASA Future tourists may detour around Jupiter’s Great Red Spot, a storm that This is the transcript of a StarDate radio episode is larger than Earth. that aired February 19, 2006. Script by Damond Benningfield, ©2006.

14 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Solar System Science

In this activity, students explore and compare planets in our solar system. Each student becomes the “ambassador” for a planet and pre- Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s pares by researching their planet, then meets with other ambassadors • Content Standard in 5-8 Earth to form new mini-solar systems. and Space Science (Earth in the solar system) Mat e r i a l s • Content Standard in 5-8 Science StarDate: The Solar System or other reference material on the solar system. as Inquiry (Abilities necessary to do scientific inquiry) Ac t i v i t y • Content Standard in 5-8 Physi- Split the class into small groups; each group researches one planet. Stu- cal Science (Properties of objects dents in the group make a list showing the planet’s atmosphere, size, mass, and materials) 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 there should 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 themselves 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 system. 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. Ex t e n s i o n What 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 spacesuit for the visit. For instance, Jupiter poses a serious challenge — it’s 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 NASA (3) that astronomers have discovered. The solar system is filled with amaz- ing sights, including (from top), an avalanche beneath a Martian ice cap, the surface of Saturn’s big moon Titan, and Saturn‘s bright rings.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 15 Rock Cycle

This activity combines the concept of Earth’s rock cycle with the characteristics of other planets in the solar system. After learning about Pl a n e ta r y Th e r mos tat Earth’s rock cycle and the basic characteristics of objects in the solar Even on a winter day, our Earth is a system, students can consider how to extend this concept to other fairly warm, comfortable home objects. The student’s goal is to create a rock cycle for each selected for life. That’s thanks in part to solar system object. the carbon dioxide in our air. Although it accounts for only Pr e pa r at i o n a tiny fraction of the atmosphere, it First, as a class, students should agree on a course of action based on their warms our planet by about 50 degrees own driving questions. For instance: Fahrenheit, and keeps Earth from turning into a ball of ice. • Which objects probably have some sort of rock cycle? Carbon dioxide is called a green- • What information about the object would relate to the rock cycle? house gas. Like the glass in a green- house, it traps heat, in the form of • What are the available resources of information? infrared energy. So sunlight can come • How should we as a class conduct our research and present our results? in, but much of the heat can’t get out. In the distant past, the atmosphere After their investigation, students must communicate their results to their contained much more carbon dioxide. peers. This involves not just presentation, but also discussion about the But rain washed most of it out of the air. supporting evidence for It combined with other chemicals to form their rock cycle claims. carbonate rocks, such as limestone. Earth’s Rock Cycle As an extension, stu- Today, some carbon dioxide is pumped dents can investigate the back into the air by volcanoes. SEDIMENTARY case for Pluto and come There’s also carbon dioxide in the up with their own con- heat & atmospheres of our two closest plan- pressure etary neighbors, Venus and Mars. clusion — what is Pluto? melting Mars may have undergone the same Mat e r i a l s process as Earth, with almost all of its • StarDate: The Solar Sys- exposure exposure carbon dioxide now locked up in rocks. & erosion & erosion The Martian atmosphere is thin, so Mars tem (or Universo Guía is cold and desolate, and temperatures del Sistema Solar) normally stay well below zero. • Slide projector and On Venus, though, the carbon diox- slides (optional) METAMORPHIC IGNEOUS ide remained in the atmosphere. Today, • Internet access, com- cooling & Venus’s atmosphere is 90 times thicker puter, and browser than Earth’s, and it’s made almost chemical (optional) change entirely of carbon dioxide, so the surface temperature is about 860 degrees melting T im Jones Fahrenheit. Activity Only on Earth is the balance just right Eng a g e to provide a comfortable home for life. Begin by reviewing the basics of Earth’s 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 special solar system member for later investigation (see the Extend section).

This is the transcript of a StarDate radio episode Ex p l o r e that aired February 22, 2000. Script by Damond Divide students into small groups of four to six. Each group should inves- Benningfield, ©1999. tigate a different planet, depending on the result of the class brainstorm. StarDate: The Solar System will help students gather information about planetary features that provide clues to the planet’s rock cycle. If students have trouble, help them consider Earth’s rock cycle and how it relates to

16 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Earth’s features. Air and water erode rocks into sediments. Earth’s mantle heats buried rocks to make metamorphic rocks. Continents collide and Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s raise mountains for water and air to erode. • Content Standard in 5-8 Science Ex p l a i n as Inquiry (Abilities necessary to The planets closest to the Sun (Mercury, Venus, Earth, and Mars) are do scientific inquiry, Understand- rocky; they will most likely show evidence of a rock cycle. The gas giants ing about scientific inquiry) (Jupiter, Saturn, Uranus, and Neptune) won’t. But these gas giants have • Content Standard in 5-8 Earth and rocky moons that can be investigated. For each solar system object, infor- Space Science (Earth in the solar mation about its surface features, agents of erosion, and geologic structure system, Structure of Earth system) under the crust will provide the major clues necessary to construct a possi- ble rock cycle. Check your school’s 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. Ex t e n d Break the students into another set of groups with each member being an expert on a different planet. These groups discuss some of the following questions:

• What is Pluto? Is it a planet? Rain, wind, rivers, and ocean tides • What about the gas giants — Jupiter, Saturn, Uranus, and Neptune? erode surface rocks, washing material into the oceans to begin the Instead of rock cycles, might they have gas cycles? rock cycle anew (below). Volcanoes • Consider what might happen if you could change the conditions on your on Io (lower left), Earth (bottom), object, such as adding liquid water to Mars or changing Earth’s atmo- and other bodies deposit new rocks sphere. Would these changes affect the rock cycles on these bodies? on the surface.

Ev a l u a t e After their investigation, each group presents its object’s rock cycle to the class. During their presentation, students should point to particular 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. NOAA NASA (2)

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 17 Equatorial Sundial

One of astronomy’s first tools to measure the flow of time, a sundial is Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s simply a stick that casts a shadow on a face marked with units of time. • Content Standard in 5-8 Earth and As Earth spins, the shadow sweeps across the face. There are many Space Science (Earth in the solar types of sundials; an equatorial sundial is easy to make and teaches fun- system) damental astronomical concepts. The face of the sundial represents the plane of Earth’s equator, and the stick represents Earth’s spin axis. • Content Standard in 5-8 Science as Inquiry (Abilities necessary to Pr e pa r at i o n do scientific inquiry) First, 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 Eg y p t i a n Sto n e h e n g e described below. Use a flashlight to demonstrate how to position and read Summer arrives in the northern hemi- the sundial indoors before going outside. sphere today, as the Sun appears farthest north for the entire year. Mat e r i a l s a n d Co n s t r u c t i o n In centuries long past, skywatch- Each student team needs a copy of page 19 and a drinking straw. ers around the world watched for the solstice at special observatories — circles Have the students cut out the Dial Face Template. Fold and glue the tem- of stones. The most famous is Stonehenge plate, making sure the dial faces are lined up. Cut a cross in the center hole in England, but circles of much smaller stones were found in the Americas, too. where the straw will be snuggly inserted. Mark the straw using the latitude strip as a guide. First mark the bottom of the straw at one end, then mark The oldest of these stone observatories may have been built in southern Egypt, a line corresponding to your latitude. Place the straw in the template hole at a site called Nabta. It was used at the line marking your latitude. The south face of the template should 6,000 years ago, and perhaps even ear- aim toward the bottom of the straw. Make sure the stick and template are lier — at least a thousand years before perpendicular. The straw should fit snugly; tape it in place if necessary. Stonehenge. Ex p e r i m e n t Anthropologist Fred Wendorf of South- ern Methodist University discovered the On a sunny day, take the sundial outside. Set it on a flat horizontal surface site in 1973. Last year, studies by Wen- with the bottom of the straw and the folded edge of the template both dorf and Colorado astronomer J. McKim resting on the ground. Aim the straw with the top pointing due north. (If Malville confirmed that Nabta had an done correctly, the straw will point at the celestial north pole, where we astronomical function. see the North Star at night.) Record the time on the sundial at least four Among other artifacts, the site contains times in one day, with measurements at least an hour apart. Each time, a 12-foot-wide “calendar circle” of small also record the “clock” time for your date and location. Try this experi- stones. Two pairs of stones stand across ment during different months. the circle from each other. If you look through the spaces between each pair, An a ly s i s you’ll see the point where the Sun rose 1. If the sundial time did not match clock time, explain why. on the summer solstice thousands of years 2. Why does this sundial have front and back dial faces? ago. This alignment was important to the people who lived at Nabta because mon- An s w e r s soons brought a few inches of rain to the 1. For each degree east or west of the center of your time zone (your longitude region soon after the solstice. difference from the center of the time zone), there is a correction of four min- Over the centuries, though, the rains utes. Also, the Sun’s location in the sky changes with the seasons, and a correc- dried up and Nabta was abandoned. tion of up to about 15 minutes for the “equation of time” must be made. Read But the people of Nabta may have left a the correction from the graph on page 19. Daylight Saving Time changes results legacy. Their culture may have stimulated by one hour. the formation of Egypt’s Old Kingdom — the civilization that built the great 2. The shadow of the straw is cast on the north face from March 21 to Septem- pyramids. 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 This is the transcript of a StarDate radio episode that equator during the first period (spring and summer) and south of the celestial aired June 22, 2003. Script by Damond Benningfield, equator during the second (fall and winter). ©1998, 2003.

18 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Di a l Fa c e Lat i t u d e St r i p Template North Face Spring/Summer 2 0

E 6 6 W 2 5

5 7

4 8 3 0

3 9

10 2 11 20 1 3 5 25 5 7 30 7 4

35 5 8 3 8 40 9

45 4 9 12 50 55 60 3 4 0

12 4 5

Finished Sundial

1 5 0 10

9 5 5 3

6 0

4 8

7 5

E W 6 6

Bottom

20.00

15.00

10.00 Fall/Winter

5.00 South Face South

minutes 0.00 JanFeb mar Apr mayJun JulAug Sep Oct Nov Dec -5.00

-10.00

-15.00 Correction for the “Equation of Time”

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 19 Scale Models

Without being informed of the expected product, the students will make a Play-doh model of the Earth-Moon system, scaled to size and So l a r Eclipse distance. The facilitator will reveal the true identity of the system at The Moon will cover up the Sun early the conclusion of the activity. During the construction phase, students tomorrow, briefly turning day to try to guess what members of the solar system their model represents. night. Unfortunately, though, it’ll Each group receives different amounts of Play-doh, with each group happen while it’s already night assigned a color (red, blue, yellow, white). At the end, groups set up here in the United States, so their models and inspect the models of other groups. They report pat- we’ll miss out on the show. terns of scale that they notice; as the amount of Play-doh increases, The event is a total solar eclipse. It for example, so do the size and distance of the model. happens thanks to a coincidence in the way the solar system is laid out: Mat e r i a l s Even though the Sun is about 400 times On a central table for all to share wider than the Moon, it’s also about 400 times farther away. So when the • String geometry is just right, the Moon can just • Rulers or meter sticks cover the solar disk. • Scissors (optional) As the Sun disappears, the air gets cooler, and the sky turns dark. The For each group Sun’s hot but thin outer atmosphere, • One or more cans of Play-doh. All the Play-doh for a group should be the the corona, forms delicate streamers same color. of light around the Moon. And the first or last moment of sunlight can form a • Large paper sheet as a work surface for rolling and shaping the Play-doh “diamond ring” — a thin ring of light r e pa r at i o n around the Moon, with a bright burst P where sunlight streams through canyons Color code each amount of Play-doh: red, 2 cans; blue, 1.5 cans; yellow, 1 or between mountains. 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 The Moon’s orbit is tilted a little, so most months the Moon passes just Play-doh and one large piece of paper to each group. above or below the Sun, and there’s no Ac t i v i t y eclipse. But two or more times a year, the Moon’s orbit lines up just right, Introduce the problem creating an eclipse. Many eclipses are Tell the groups that they will make a scale model of two members of our partial, so the Moon appears to only solar system. Do not reveal that it is the Earth and Moon — that’s the sur- nick the Sun. But this month it goes right prise that makes this activity memorable. Along the way, they can make across the heart of the Sun, creating a guesses about what the model represents. beautiful eclipse. Divide the Play-doh The total eclipse is visible along a Tell groups to divide their Play-doh into five equal pieces. thin path that runs through China and They may use whatever creative and clever means they can think of to Russia, across the tip of northern Green- land, and just into Canada. The partial solve this problem. Example solution: Roll the Play-doh into a long cyl- eclipse is visible across a much wider inder, then divide it into pieces. A 50-cm cylinder can be cut into 10-cm area, but it doesn’t include the U.S. lengths, then formed into spheres. Tell groups to divide up one of the larger 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 This is the transcript of a StarDate radio episode that into a little sphere. aired July 31, 2008. Script by Damond Benningfield, Copyright 2008.

20 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Make a guess After they have made two Play-doh spheres, ask each group to write down Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s three guesses about what these solar system objects might represent. Dis- • Content Standard in 5-8 Earth cuss the guesses with the students. At least one student will guess they are Science (Earth in the solar sys- Earth and the Moon. Next, ask them to make a guess of how far apart to tem) put their Earth and Moon spheres to make a true model. A scientist follows • Content Standard in 5-8 Science up and tests guesses with observations and measurements. and Technology (Students should Measure the big sphere diameter; this is the diameter of Earth develop abilities of technological Tell each group to measure the diameter of the Earth sphere. They may design) cut the sphere in half. They may measure with a string and mark off the • Content Standard in 5-8 Science diameter or use a meter stick. as Inquiry (Abilities necessary to Separate the big and little spheres do scientific inquiry, Understand- After students have measured the Earth and Moon sphere diameters, ask ing about scientific inquiry) 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. Ex t e n d The Sun is about 150 million km from Earth. Estimate how many Earth diameters 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 Moon’s orbit around Earth. Ba c kg r o u n d Earth to Moon Ratio Earth Moon Ratio Diameter (km) 12,756 3,475 3.7

Volume (m3) 1.08 x 1021 2.2 x 1019 49 4 r3 V= /3

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 Earth’s diameter is: 384,500 km = 30 Earth diameters. 12,756 km In round numbers, Earth’s 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 Moon’s 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 Moon’s orbital path around Earth is about half the diameter of the Sun.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 21 Sunspots

The Sun is a huge sphere of gas. The visible layer of the Sun, which we view as the surface, is the photosphere. Its temperature is about Re ve rse d Po l a r i t y 6,200 degrees Celsius (10,340 degrees Fahrenheit). Above the surface When a character in TV science fiction are the chromosphere and corona. Sunspots are some of the most faces a tough technical prob- noticeable features of the Sun. lem, one solution always seems to work: reverse the polarity. Mat e r i a l s That may not fix problems in • Telescope (with finder covered) real life, but for the scientists who study • Piece of white cardboard mounted on a the Sun, reversing the polarity is a big event. It signals that the Sun has started tripod a new 11-year cycle of magnetic activ- Pr e pa r at i o n ity. The easiest way to position the telescope A new cycle began in January, when (since the finder is covered and you don’t want to telescopes on the ground and in orbit “sight” along the side) is to move the telescope until measured a small sunspot — a rela- its shadow is smallest. If your telescope doesn’t have tively cool, dark magnetic “storm” on a special motor, the image will slowly track across the surface of the Sun. The observations showed that the polarity of the sunspot the cardboard as Earth rotates. You may use binoculars, although too was reversed from that of the sunspot much sunlight can cause heat to build up inside the binoculars and dam- before it. age them. For binoculars, the standard size (7x35) works satisfactorily. As the Sun spins on its axis, different Ex p e r i m e n t layers of hot gas spin at different rates. Draw a circle around the edge of the Sun on some paper placed over That generates a powerful magnetic the cardboard. Now quickly sketch the positions and sizes of all the vis- field around the Sun. ible sunspots. Write the time and date on the edge of the paper. Repeat Over a period of several years, the your observations over several days or weeks. (If you trace the images on lines of magnetic force get twisted and very thin paper, you can later overlap them to see changes.) Be careful to tangled. That produces many more include the fine detail that surrounds some sunspots. An alternative is to sunspots. The lines can also cross each other, creating “short circuits” — pow- download images from web sites each day to use for this activity or to com- erful explosions of energy and particles. pare to your own data. These outbursts can disrupt communica- An a ly s i s tions and electrical systems on Earth. 1. Can you identify any sunspots or sunspot groups? Did they change At the end of a cycle, the Sun’s mag- shape, size, or position over time? netic field flips over: magnetic north becomes magnetic south, and vice 2. If you move the cardboard screen farther away, what happens to the versa. image? The Sun has been quiet for the last few years. But the start of a new cycle 3. (Advanced) The diameter of the Sun is about 1.4 million km (864,000 means that it’ll get busier in the years ahead. The new cycle should peak miles). Measure the diameter of your image and estimate the physical size around 2012, and end around 2019 of your largest sunspot. Earth is 12,700 km (7,900 miles). Compare your — when scientists will once again be largest sunspot with the size of Earth. Find the size of the sunspot with a waiting for the Sun to reverse polarity. proportion equation: 1,390,473 km sunspot diameter in km = diameter of Sun’s image in mm sunspot image in mm This is the transcript of a StarDate radio episode that aired June 13, 2008. Script by Damond Benningfield, 4. Why are sunspots dark? ©2008.

22 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e ! Safety Wa r n i ng An s w e r s Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s Do not look directly at the Sun, 1. Sunspots change size and shape over a period of days. • Content Standard in 9-12 Science especially with a telescope. You can as Inquiry (Abilities necessary to PERMANENTLY DAMAGE YOUR The Sun rotates on its axis in about 25 days (its equator do scientific inquiry, Understand- EYES! When working with students, ing about scientific inquiry) it’s best to cover the finder telescope rotates faster than its poles). completely so that they cannot look Observations taken over a through it. Never trust filters that period of several days should go into the eyepiece or that show this. cover the objective. 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 dark since 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 incandescent 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 background of the photosphere.

Spanning more than 13 times the total area of Earth’s surface, this large group of sunspots photographed in 2001 coincided with the peak of the 11-year solar cycle (see sunspot number chart below). Inset: Close-up view of a typical sunspot. / NSF NOAO 300

200

100 SUNSPOT NUMBER

0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 DATE

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 23 Spectroscope

Just as a geologist collects rocks or minerals and a botanist collects plants, an astronomer collects light. Astronomers usually cannot touch Elec tromagne tic Sp e c t r u m the objects they study, like stars or galaxies. But they can analyze the Scientists learn much about the world light these celestial objects radiate using a spectroscope. When an by splitting things apart. A geol- astronomer looks at a star through a spectroscope, he or she sees a ogist can split rocks, a botanist colorful spectrum that is full of information. can split seeds, and a physicist can split atoms. About the only Students will construct their own spectroscope as they explore and thing an astronomer can split is a beam observe spectra of familiar light sources. Extension activities expand of light, but even that reveals a great deal — from the temperature of a star their understanding of different kinds of spectra and sharpen their to the final moments of matter falling observing skills. You may challenge more advanced students to make into a black hole. technological improvements to their instruments. Our eyes perceive the light from a star as a single color. But instruments Mat e r i a l s split the light into its individual wavelengths or colors. The intensity of each For class: For each spectroscope: wavelength tells astronomers how hot • Incandescent light bulb (60- • Half of a manila folder the star is, what it’s made of, how it’s 100-watt frosted) and base • Sheet of black paper moving, and whether it has compan- ions, like other stars or even planets. • String of clear holiday lights • 3 index cards (3x5-inch size) (optional) Visible light is just one of the forms • Tape or rubber bands • Fluorescent light (single bulb) of energy that make up the electromag- • Scissors netic spectrum. Other forms include • Transmission grating sheet • A small paper clip infrared and radio waves, which have (available from science supply store) a longer wavelength than visible light, • Hole puncher and ultraviolet, X-rays, and gamma • 2 transparency sheets rays, which are shorter than light. • Glo-Doodler Telescopes on the ground or in space (available from Colorforms) detect these forms of energy and split them into their component wavelengths, Pr e pa r at i o n too. Each type of energy tells us about Making the transmission grating cards the environment in which it was cre- 1. Cut a 3x5-inch index card in half, resulting in two 3x2.5-inch cards. ated. Infrared, for example, comes from Then cut a narrow strip off the three inch side of one of the halves. This relatively cool objects like gas clouds will help fasten the card onto the spectroscope tube. and planets. And X-rays come from some of the most violent objects in the 2. Fold each 3x2.5-inch card in half along the short side, then snip a slit universe, like disks of hot gas spiraling perpendicular to the fold about half a centimeter from either corner of into black holes. the fold. Punch a hole about two centimeters down in the fold. The open- By splitting each form of energy, ing should be about a centimeter wide. astronomers build a more complete understanding of the universe — one Preparing the grating 2.5 in wavelength at a time. paperclip 1. Sandwich the transmission slit grating material between two punched sheets of transparency mate- 3 in holes rial. Try not to touch the very

This is the transcript of a StarDate radio episode that sensitive grating with your aired in July 2004. Script by Damond Benningfield, fingers. ©2001, 2004. 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.

24 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s

spectrum sandwich spectrum • Content Standard in 9-12 Physical Science (Interactions of energy Activity and matter) • Content Standard in 9-12 Earth Eng a g e and Space Science (Origin and Distribute individual grating cards to the students. Let them look around evolution of the universe) the room. You may wish to have a light bulb (e.g. 60- 100-watt frosted • Content Standard in 9-12 Science bulb) or string of holiday lights available. and Technology (Abilities of Ex p l o r e technical design) With 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. As k s t u d e n t s • 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 grating fixed at one end, will block stray light from the view of the spectrum and provide the structural support for the spectroscope components.

What could you use to block out the stray light to make a dark background for viewing spectra? Paper Clip

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. Folded 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 Grating card bulb. Does the spectrum of the fluorescent bulb look like that of the incandescent bulb? What is the same or different? (Students should see Finished spectroscope a continuous spread of color in both bulbs’ spectra. They also may see separate bands of color only in the fluorescent bulb spectrum.)

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 25 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 feature — 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. Ex p l a i n This is a transmission grating. Its surface is scored or etched with thousands of parallel grooves per centimeter. As light travels through the narrow 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. That’s why blue light appears closest 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

26 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e wide slit. But as the slit narrows, less light passes through. So an observer Te c hn i c a l n o t e s f o r must strike a balance between the spectrum’s resolution and brightness. c h e m i s t r y /phy s i c s t e a c h e r s •This activity fits well with your The incandescent light has a hot filament which produces a continuous exploration of atomic structure, spectrum (hot liquids also produce continuous spectra). The fluorescent spectra of various elements, how light is made of a tube of hot gas which produces an emission spectrum spectra vary for isotopes, and — more energy is released at certain wavelengths than at others so those Kirchhoff’s laws. 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.] Ex t e n d Turn 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 the bulb by itself or from the fluorescent bulb. (The Glo-Doodler absorbs certain wavelengths, which show as black bands in the spectrum.)

Think of a safe way to view the spectrum of the Sun — DON’T 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 spectrum. The Sun’s 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 wavelengths 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 Sun’s photosphere? What process 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 spectroscope construction and their observations of spectra, ask students how they would improve their spectroscope. Could it allow an observer to measure the wavelength as they view a spectrum through the spectroscope? They should include a procedure for calibrating the wavelength scale. Ev a l u a t e Given 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. / NSF NOAO A portion of our Sun’s spectrum reveals dark lines representing specific elements present in the Sun’s atmosphere.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 27 Stars and Galaxies

St u d e n t Pa g e Se e i n g i n to t h e Pa s t A galaxy is a gravitationally bound system of stars, gas, and dust. Gal- We can’t travel into the past, but we axies range in diameter from a few thousand to a few hundred thou- can get a glimpse of it. Every sand light-years. Each galaxy contains billions (10 9) or trillions (1012) time we look at the Moon, for of stars. In this activity, you will apply concepts of scale to grasp the example, we see it as it was a distances between stars and galaxies. You will use this understanding little more than a second ago. to elaborate on the question, Do galaxies collide? That’s because sunlight reflected from the Moon’s surface takes a little more Ex p l o r e than a second to reach Earth. We see On a clear, dark night, you can see hundreds of bright stars. The next table the Sun as it looked about eight minutes shows some of the brightest stars with their diameters and distances from ago, and the other stars as they were a the Sun. Use a calculator to determine the scaled distance to each star few years to a few centuries ago. (how many times you could fit the star between itself and the Sun). Hint: And then there’s M31, the Androm- you first need to convert light-years and solar diameters into meters. One eda galaxy — the most distant object light-year equals 9.46 x 1015 meters, and the Sun’s diameter is 1.4 x 109 that’s readily visible to human eyes. meters. This great amalgamation of stars stands almost directly overhead late this eve- Star Diameter Distance Scaled Distance ning. When viewed from a dark sky- (Constellation) (Sun=1) (light-years) (distance÷diameter) watching location, far from city lights, Spica (Virgo) 8 261 it looks like a faint, fuzzy blob. But that blob is the combined glow of hundreds Betelgeuse (Orion) 600 489 of billions of stars — seen as it looked Deneb (Cygnus) 200 1,402 more than two million years ago. Altair (Aquila) 2 17 Andromeda is like a larger version of Vega (Lyra) 2.7 26 our own Milky Way galaxy. It’s a flat disk that spans more than a quarter-mil- Sirius (Canis Major) 1.6 8.6 lion light-years. Its brightest stars form spiral arms that make the galaxy look There are three galaxies beyond the Milky Way that you can see without like a pinwheel. Yet the galaxy is so optical aid: the Andromeda galaxy, the Small Magellanic Cloud, and the far away that its structure is visible only Large Magellanic Cloud. Figure the scaled distance to these galaxies (how through telescopes. many times you could fit the galaxy between itself and the Milky Way). The light from M31 has to travel about two and a half million light-years Diameter Distance Scaled Distance Galaxy (distance÷diameter) to reach us — about 15 quintillion (light-years) (light-years) miles — the number 15 followed by (no conversion needed) 18 zeroes. Yet even across such an Milky Way 100,000 0 enormous gulf, the galaxy is so bright Andromeda Galaxy 125,000 2,500,000 that we can see it — faintly — with our own eyes, crossing high overhead late Large Magellanic Cloud 31,000 165,000 tonight. Small Magellanic Cloud 16,000 200,000

El a b o r at e Do you think galaxies collide? Why or why not?

28 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Te a c h e r Le s s o n Key Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s

Ob j e c t i v e s • Content Standard in 9-12 Science • Calculate scale distances of stars and galaxies. as Inquiry (Understanding about scientific inquiry) • Compare neighboring galaxies to neighboring stars. • Content Standard in 9-12 Earth • Understand the relative distances between objects in space. and Space Science (Origin and Eng a g e evolution of the universe) Find 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. Ex p l o r e (An s w e r s )

Stars Scaled Distance Scaled Distance Galaxies To convert Distance÷Diameter from Milky Way 15 Distance÷Diameter Distance (ly) x 9.46 x 10 (m/ly) (both must be in the same units, Distance÷Diameter 9 (no conversion needed) Diameter (Suns) x 1.4 x 10 (m/Sun) do conversions first) (no conversion needed) Spica (Virgo) 2.22 x 108 Milky Way ------Betelgeuse (Orion) 5.51 x 106 Andromeda Galaxy 20 Deneb (Cygnus) 4.74 x 107 Large Magellanic Cloud 5.32 Altair (Aquila) 5.74 x 107 Small Magellanic Cloud 12.5 Vega (Lyra) 6.51 x 107 Sirius (Canis Major) 3.59 x 107

Ex p l a i n How 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 are usually less than 100 galaxy-diameters apart. El a b o r at e Do you think galaxies collide? Why or why not? Galaxies do collide. They are relatively close to each other and they have the combined 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 within galaxies seldom collide because they are so far away from each other. Clouds of gas and dust in the galaxies do collide, though, giving birth to new stars. Ev a l u a t e Rubric: Explore = 60 pts (6 pts for each calculation), Explain = 25 pts, Elaborate = 15 pts

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 29 Coma Cluster of Galaxies

In 2006, Hubble Space Telescope aimed at a nearby collection of Nat i o n a l Sc i e n c e Ed u c at i o n Sta n d a r d s galaxies called the Coma Cluster. Using the HST images, astronomers • Content Standard in 9-12 Science as gained fascinating insights into the evolution of galaxies in dense Inquiry (Abilities necessary to do sci- galactic neighborhoods. In this activity, students will first learn the entific inquiry, Understanding about basics of galaxy classification and grouping, then use HST images to scientific inquiry) discover the “morphology-density effect” and make hypotheses about • Content Standard in 9-12 Earth and its causes. Space Science (Origin and evolution of the universe) Mat e r i a l s & Pr e pa r at i o n • Each student needs a copy of the next 7 pages (not this page). You may Invisible Clu s t e r copy the pages out of this guide, but it is recommended that you go to If you aim a big telescope at the Coma mcdonaldobservatory.org/teachers/classroom and download the student Cluster, you’ll see galaxies galore worksheets. The galaxy images in the online worksheets are “negatives” — thousands of galaxies of all sizes of the real images, which provides better detail when printing. Supple- and shapes, from little puffballs to mental materials for this activity are also available on the website. big, fuzzy footballs. Even so, you won’t • Each student or student team will need a calculator and a magnifying see most of the cluster because it’s invis- glass (a linen tester works well). ible to human eyes. • Knowledge of percentages is needed before doing this activity. Some of the cluster’s “dark side” is in the form of superhot gas that glows in X- rays. All together, the gas is several times Su gg e s t e d Gr a d i ng as massive as the galaxies themselves. • Page 31 (5 pts): Student provides clear explanations of the scheme. There’s a dynamic interplay between the hot gas and the galaxies. • 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) As galaxies “fall” toward the center of the cluster, they fly through the hot gas, • Pages 34 and 35: Not graded; based on student’s subjective interpreta- which strips away the cold gas inside tion. the galaxies. Without their cold gas, the • Page 36 (30 pts): Graded for completion, not accuracy. Students will get galaxies can’t give birth to new stars. That different numbers, but math should be correct. Answers for percentages helps transform the appearance of some are typically in the following range: (Cluster: E 50 percent, L 30 percent, of the galaxies. Spiral galaxies lose their S 20 percent) (Field: E 20 percent, L 10 percent, S 70 percent). Students spiral arms, so they look like featureless usually find a higher percentage of spirals in the field. disks. • Page 37 (bottom, 30 pts): Student hypothesis should mention the But the galaxies may have an effect on effects of interactions and ram-pressure stripping in changing past gas- the hot gas, too. Over the eons, it should have cooled, but it hasn’t. Hot “jets” of rich spirals into current gas-poor ellipticals and lenticulars in clusters. particles from the centers of some galaxies may act like big blowtorches, keeping the gas hot. Yet even the gas and the galaxies combined make up only a small fraction of the Coma Cluster. As much as 80 percent of its mass may consist of dark matter — a form of matter that produces no detectable energy, but that exerts a gravitational pull on the visible matter around it. The dark matter ensures that most of this impressive cluster remains invisible.

30 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e GEMS C OLLA B ORATION

Eng a g e Defining Characteristics Three Examples Galaxy Type The diagram above shows a mosaic of (write a short description, provide enough detail (give 3 grid (name and draw) 40 galaxies. These images were taken so that anyone could use your scheme) coordinates) with Hubble Space Telescope and show the variety of shapes that galaxies can assume. When astronomer Edwin Hubble first started studying these various types of galaxies in the 1920s, he realized he needed to develop a way to organize and categorize them. He created 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.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 31 Ex p l o r e The image on the left is the classification scheme that Hubble himself came up with. He thought that the “tuning fork” sequence represented the evolutionary progression of galaxies. This concept turned out to be wrong, although astronomers still use these ALS SPIR RY general categories and labels to describe galaxies. INA RD

O Th e Ma i n Ga l a x y Typ e s S

ELLIPTICAL GALAXIES R

Sb A • Elliptical (E): Spherical or elliptical shape (like

y/ T im Jones SO L Sa Im Sc U a football), has no flat disc or spiral arms G SBa SBb IBm E R

ormen d SBc Boxy Disky SBO R • Lenticular (S0): Smooth, flat disk shape with- K I out spiral structure, often hard to distinguish

Jo h n B A R from ellipticals RE D SPI RALS • 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 1 2 3 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: 4 5 6 • Irregular (IR): An oddly shaped galaxy that doesn’t fit into any other category • Interacting (INT): Two or more galaxies that are so close together that they are affecting each other’s shape

Using the definitions above, place the 12 galaxies on the left into their proper morphology categories: 7 8 9

Morphology Picture Numbers (3 each)

E/S0/SB0

10 11 12 IR NASA

The smallest galaxies are often called dwarf galaxies (No. 5 and No. 7 are dwarf galaxies). These contain only a few billion stars — a small number compared to the Milky Way’s 200 billion. The largest ellipticals con-

h ers all ot p rig h t); ESO (to tain several trillion stars.

32 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e Th e Co m a Ga l a x y Cl u s t e r

The Coma Cluster, which is centered about 320 million light-years away, Arcturus contains several thousand individual galaxies. The cluster has a roughly BIG DIPPER spherical shape and is about 20 million light-years across. (For compari- COMA BERENICES son, the Milky Way is 100,000 light-years across). That many galaxies in a relatively small space makes the Coma Cluster one of the richest and densest galaxy clusters in our region of the universe.

W NW T im Jones

On the following pages you will be asked to count different types 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 it’s either an E or S0/SB0, it is okay to guess between these two. I ? II II) Spirals and Barred Spi- rals It can be hard to tell these ? I apart. If you know it’s II either an S or SB, it is okay to guess between these two. ? II III) Irregular galaxy I IV) Uncertain I An edge-on view of a gal- ? axy that could possibly be I ? an S0, SB0, S, SB, or IR. Star There are too many pos- sibilities, so do not count these. II Star) Any object that has “crosshairs” sticking out of I

it is a foreground star in the T eam (3) Milky Way galaxy, so do not IV IV I count these. Star T reas u ry C S

?) A Star Don’t count small, faint IV III objects like these that are II I /Coma H ST too hard to classify. c NASA / STS

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 33 A

Count the number of galaxies of each E S0 /SB0 S SB IR / INT morphological type and write down the number in the correct spot in the table. Top Image (A) Use the guidelines on page 4 to help you decide which objects to count. Bottom Image (B)

34 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e C

E S0 /SB0 S SB IR / INT Count the number of galaxies of each morphological type and write down the Top Image (C) number in the correct spot in the table. Use the guidelines on page 4 to help Bottom Image (D) you decide which objects to count.

D T eam (4) ry T reas u ry C S A I /Coma H ST c NASA / STS

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 35 Ex p l a i n Galaxies in Clusters, Groups, and the Field Galaxies are found throughout the universe, from our next door neighbors — 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 numbers called groups, like the Local Group that contains our Milky Way; and sometimes they are isolated far from one another in the field.

Minimum Number Diameter Number of of Non-dwarf (1 Mpc = 3.26 Total Mass Galaxies Galaxies million light years) Galaxy Cluster 1014 to 1015 50 to thousands 6 2 to 10 Mpc Large and dense solar masses Galaxy Group 1013 solar less than 50 3 1 to 2 Mpc Small and dense masses The Field Voids, can be larger very few 0 < 1010 Large and deserted than 100 Mpc Clusters, groups, and some isolated galaxies can all be part of even larger structures called superclusters. At the largest scales in the visible universe, superclusters are gathered into filaments and walls surrounding vast voids, often described as resembling large soap bubbles. This structure often is referred to as the “cosmic web.” On the previous two pages, the images on the top (A&C) show the dense central core of the Coma Cluster, and the images on the bottom (B&D) show galaxies out in the field. Fill in the table below using the numbers you wrote down on the previous two pages:

E S0 & SB0 S & SB (sum both together) Total Morphology→ Ellipticals Lenticulars Regular and Barred Spirals (E+S0+SB0+S+SB) Image A Image C Sum Total From A + C (e) (f) (g) (h)

Image B Image D Sum Total From B + D (i) (j) (k) (m)

Using a calculator, find the percentages i — of each galaxy type in the cluster versus m j the field (ignore IRs and INTs). Fill in —m each of the boxes on the right: k —m

Where did you find a higher percentage of spirals — in the Cluster or in the Field? Answer: ______

36 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e The percentages that you just found tell us which types of galaxies are common in the Coma Cluster versus which types are common in the field. Astronomers have done this same exercise on hundreds of thousands of galaxies in the nearby universe, and discovered that the following percentages are pretty typical: • In dense clusters, 40 percent of the galaxies are ellipticals, 50 percent are lenticulars, and 10 percent are spirals. • In the field, 10 percent of the galaxies are ellipticals, 10 percent are lenticulars, and 80 percent are spirals. When galaxies are found very close together there are more ellipticals and lenticulars. When galaxies are far apart there are more spirals. Astronomers call this the “morphology-density effect” (the word morphology means “type” or “class,” not “transformation,” as in biology). The term basically means that in crowded galaxy neighborhoods, like clusters, there are different types of galaxies than are found in open areas, like the field.

Ex t e n d The clues needed to answer the last question are in the following paragraphs. Please read the paragraphs carefully and then answer the question at the right. As a general rule, spiral galaxies (S and SB) have a lot of gas and are still forming lots of new stars. Elliptical and lenticular galaxies (E, S0, and SB0) are gas poor and are not making many new stars. Spirals are Gas-rich Both Ellipticals and Lenticulars are Gas-poor Using what you’ve learned, write a hypothesis that might explain why we see Galaxies that are very close to each other, such the morphology-density effect. In other words, why do we see more elliptical as those in clusters, often undergo many violent and lenticular galaxies in clusters and more spiral galaxies in the field? Remem- interactions with each other. When a gas-rich ber that galaxies change and evolve over time, and these galaxies have had a spiral galaxy interacts with another galaxy, it very long time to get to this point. tends to quickly use up most of its gas to make new stars, leaving little gas behind. Galaxy-galaxy interactions often change gas-rich galaxies into gas-poor galaxies. Many lenticular galaxies are the remains of old spirals that have lost their gas, and many elliptical galaxies are the remains of several spiral galaxies that have collided. Galaxy clusters are usually filled with a lot of extremely hot gas that is spread between galaxies throughout the cluster. However, there is no hot gas like this out in the field. When the radiation from this hot gas hits a spiral galaxy, it strips the spiral galaxy of its much cooler gas in a process called ram-pressure stripping. This process quickly converts a gas-rich spiral galaxy into a gas-poor lenticular galaxy. Spiral galaxies have a hard time surviving in the superheated gas environment.

S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e 37 Resources

Pr i n t e d m a t e r i a l s The Stars: A New Way to See Them In t e r n e t StarDate magazine by H. A. Rey, 1976 StarDate Online 1-800-STARDATE ISBN 0395245087 stardate.org stardate.org/magazine Nearest Star: The Surprising Science Universo Online StarDate: The Solar System of our Sun radiouniverso.org 1-800-STARDATE by Leon Golub and Jay M. Pasachoff, 2001 ISBN 0-674-00467-1 stardate.org/resources/ssguide McDonald Observatory Visitors Center mcdonaldobservatory.org StarDate: Beyond the Solar System Cambridge Encyclopedia of the Sun 1-800-STARDATE by Kenneth R. Lang, 2001 ISBN 0-521-78093-4 National Science Teachers Association stardate.org/resources/btss www.nsta.org

The Universe at Your Fingertips Galaxies in Turmoil by Chris Kitchin, 2007 NASA Astronomical Society of the Pacific, 1995 www.nasa.gov ISBN 1-886733-00-7 ISBN 1-84628-670-0 www.astrosociety.org Lawrence Hall of Science: Powers of Ten powersof10.com El Universo a Sus Pies Great Explorations in Math Astronomical Society of the Pacific, 2002 and Science ISBN 1-58381-199-0 www.lawrencehallofscience.org/gems NASA resources for sale www.astrosociety.org education.nasa.gov/edprograms/core/home/ Au d i o Observer’s Handbook StarDate radio NASA Education Resources (for advanced stargazers) 1-800-STARDATE education.nasa.gov Royal Astronomical Society of Canada stardate.org/radio www.rasc.ca AAS Education Resources Universo radio www.aas.org/education/EducatorResources.php Princeton Field Guides: Stars & 1-800-STARDATE Planets, 4th ed. radiouniverso.org/radio/ ASP Education Resources by Ian Ridpath and Wil Tirion, 2007 www.astrosociety.org/education.html ISBN 978-0-691-13556-4 Spanish Language Astronomy Materials Center The Young Oxford Book of Astronomy www.astronomyinspanish.org by Simon and Jacqueline Mitton, 1995 ISBN 0-19-521169-3 Galaxies and Cosmos Explorer www.as.utexas.edu/gcet Unfolding our Universe by Iain Nicolson, 1999 ISBN 0521-59270-4

National Science Education Standards National Research Council, 1996 ISBN 0309053269 www.nap.edu/html/nses/html

The Solar System: A Firefly Guide by Giovanni Caprara, 2003 ISBN 10: 1552976793

38 S t a r D a t e /Un i v e r s o Te a c h e r Gu i d e More Resources from McDonald Observatory

McDonald Observatory Guidebook Our 36-page guidebook covers all aspects of McDonald Observatory, from the telescopes to the community, from history to today’s research proj- ects. Makes a great keepsake. SKU 50401 $5.95

Subscribe to StarDate Each issue of our bimonthly magazine includes feature arti- McDonald Observatory DVD cles, astronomy news, skywatching information, and beautiful This DVD contains two programs. In astrophotography. Articles are written in non-technical lan- “Understanding the Universe,” tour guage so they make good classroom resources, and the star McDonald Observatory (14 minutes). charts and sky calendars will help students navigate around In “Telling Secrets,” learn about the the night sky. Hobby-Eberly Telescope (8 minutes). SKU 50209 $10.95 CALL 1-800-STARDATE (8-5, Monday-Friday Central Time)

Subscribe to StarDate Today! Order Online at stardate.org/giftshop Send order to: McDonald Observatory Merchandise orders (432) 426-3640 QUANTITY SKU DESCRIPTION UNIT PRICE TOTAL University of Texas at Austin Magazine subscriptions (800) 782-7328 1 University Station, A2100 Fax orders & subscriptions (512) 471-5060 Austin, TX 78712 Please make checks payable to the University of Texas at Austin Subscribe to StarDate (U.S. subscribers) Name •1 year $24 •2 years $42 •3 years $60 Address SUBTOTAL Shipping & handling from chart below City State Zip TX residents, add 8.25% sales tax

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