The Solar System?

5_CNLAESE589428_FMTOC.indd 18 xviii Index...... R23 . . Index. R� . Interactive Glossary Unit 15Review Lesson 4 Inquiry Lesson3 Inquiry Lesson2 Lesson 1 Unit 15—ForcesandMotion Inquiry Flipchart Inquiry Flipchart Inquiry Flipchart Inquiry Flipchart Inquiry Flipchart Careers inScience:SafetyEngineer 735 . . WhatAreNewton’sLaws? WhatAreForces? Engineering andTechnology:FootballSafetyEquipment . . . . 737 . p.79—ForcesofLooseChange/BlastOff p.78—WhatAreBalancedandUnbalancedForces? p.77—HowDoForcesAffectMotion? p.76—BalloonRacer p.75—OnaRoll/MakeItEasier WhatAreBalancedandUnbalancedForces? HowDoForcesAffectMotion? 699 ...... 723 . 697 . . .719 . .717 ..721 12/28/10 9:09:15 PM

I Wonder Why Why are most observatories built far from large cities? Turn the page to find out. investigations. out careful questions bycarrying Scientists answer Big Idea the Sun. objects orbiting up ofmanydifferent system whichismade Earth ispartofasolar 12/28/10 5:51:52 PM 537 5_CNLAESE589428_U12O.indd 538 UNIT 12 538 Unit 12 Here’s why Questions, andinvestigationsontheInquiryFlipchart. In thisunit,youwillexploreBigIdea,Essential see dimlightsfromstars. artificial outdoorlightingwhichcanmakeitimpossibleto cities toavoidthebrighteningofnightskycausedby

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s People inScience:KalpanaChawlaandClaudiaAlexander s WhatAreStarsandGalaxies? WhatObjectsArePartof Engineering &Technology:ToolsinSpace orbiting asun. which ismadeupofmanydifferentobjects Big Idea Mostobservatoriesarebuiltfarfrom HowDoWeObserve Essential Questions p. 59—How Do We Observe Objects in the Solar System? p. 61—ImproviseIt:HowHighIsThatStar? p. 60—ASmallSliceoftheUniverse/ColorfulStars . .573 p. 58—MakeaScaleModel/FirstSightings Earth ispartofasolarsystem . .539 ..559

Before you begin each lesson, be . .571 sure to write your thoughts about ..561 the Essential Questions. . .557 12/28/10 5:52:03 PM

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© Houghton Mifflin Harcourt Publishing Company (bkgd) ©NASA/JPL/Space Science Institute System? Part oftheSolar What Objects Are Question Essential make notes intheInteractive Glossary. eachone, about learn you As List theterms. Lesson Vocabulary the rings madeof? the rings andwhat are planetshaveWhich rings, question inthislessonandrecord ithere. Find to thefollowing theanswer Active Reading Active Reading How areHow different? they are How themselves, thesethingsalike? andcontrastscomparisons ask whenthey readers on stay focused Active different. contrasts—how thingsare alike and explain they and comparisons because ideasinthislessonareMany connected Compare andContrast 1 12/28/10 9:40:03 AM 539 5_CNLAESE589428_U12L01S.indd 540 540 revolves once around Earth about every 27days. every revolves around about once Earth has only It one. Earth planetshave Many moons. other objects. are smallnaturalthe sun.Moons that revolve around objects 24hours. isthelengthof onedayThis every once onEarth. rotates Earth through onitsaxis thecenter ofaplanet. goes anaxis. rotate, linethat orspin,about isanimaginary This thesun. around call astarwe revolve oursolarsystem,In theplanetsandotherobjects that revolves around Aplanetisalarge, astar. roundit. body that revolve around objects and theplanetsotherspace E two detailsthat tell allplanetsare how alike. two to learnaboutotherobjectsinspace. moon revolves around Earth.Read on the suninapath calledanorbit.The That meansEarthtravels around Earth revolves around thesun. moon form asystem inspace. The sun,Earth,andits two detailsthat tell allplanetsare how alike. two Active Reading Active Reading Unlike planets, some objects don’t someobjects Unlike planets, revolve directly around There are ofthem eight planetsinoursolarsystem. All called asolarsystem. Asolarsystemcalled ismadeupofastar are ofalarger part system anditsmoon inspace arth As you read you underline thispage, As from thesun! million kilometers 150 is about Earth Diagrams notto scale. 12/28/10 9:42:12 AM

© Houghton Mifflin Harcourt Publishing Company (bl) ©NASA/Corbis have none! one. Venus andMercury hasonly Earth moons. planets have manySome far from eachother. solar system are very planetsinour The moon anditsorbit. moon Draw for anorbit theplanet. drawThen a Around and Around or elliptical [eh or elliptical circles. They are oval-shaped, solar system are notperfect oftheplanets inour oftheplanets inour orbits orbits The The • LIP sun • tuh • planet kuhl]. 12/28/10 9:42:33 AM 541 5_CNLAESE589428_U12L01S.indd 540 540 revolves once around Earth about every 27days. every revolves around about once Earth has only It one. Earth planetshave Many moons. other objects. are smallnaturalthe sun.Moons that revolve around objects 24hours. isthelengthof onedayThis every once onEarth. rotates Earth through onitsaxis thecenter ofaplanet. goes anaxis. rotate, linethat orspin,about isanimaginary This thesun. around call astarwe revolve oursolarsystem,In theplanetsandotherobjects that revolves around Aplanetisalarge, astar. roundit. body that revolve around objects and theplanetsotherspace E two detailsthat tell allplanetsare how alike. two to learnaboutotherobjectsinspace. moon revolves around Earth.Read on the suninapath calledanorbit.The That meansEarthtravels around Earth revolves around thesun. moon form asystem inspace. The sun,Earth,andits two detailsthat tell allplanetsare how alike. two Active Reading Active Reading Unlike planets, some objects don’t someobjects Unlike planets, revolve directly around There are ofthem eight planetsinoursolarsystem. All called asolarsystem. Asolarsystemcalled ismadeupofastar are ofalarger part system anditsmoon inspace arth As you read you underline thispage, As from thesun! million kilometers 150 is about Earth Diagrams notto scale. 12/28/10 9:42:12 AM

© Houghton Mifflin Harcourt Publishing Company (bl) ©NASA/Corbis have none! one. Venus andMercury hasonly Earth moons. planets have manySome far from eachother. solar system are very planetsinour The moon anditsorbit. moon Draw for anorbit theplanet. drawThen a Around and Around or elliptical [eh or elliptical circles. They are oval-shaped, solar system are notperfect oftheplanets inour oftheplanets inour orbits orbits The The • LIP sun • tuh • planet kuhl]. 12/28/10 9:42:33 AM 541 5_CNLAESE589428_U12L01S.indd 542 542 as large as it does onEarth. as large asitdoes three times look sun would to Mercury, thesun.On the istheclosestplanet Mercury much like Earth’s moon. isfilledwithcraters,surface Its ofEarth. than halfthesize in oursolarsystem, isless Mercury, thesmallestplanet Mercury than 1,000 volcanoes on Venus’sthan 1,000volcanoes surface. dioxide. Lavacarbon flows from more its atmosphere ismadeup mostly of surface! cloudssurroundThick Venus, and Venus meltat its issohotthat leadwould Venus Earth’s closestneighbors inspace. is notthemoonorastar. ItisVenus, oneof At times,thebrightest objectinthenight sky the innerplanetsare alike. Active Reading Active Reading As you read you ways underline thispage, As inwhich P planets are Mercury, Venus, andMars. Earth, ordertheinner In from closestto farthest, four inner planetsare theclosestto thesun. center, to theotherside. innerplanets The throughfrom its onesideoftheplanet, Aplanet’sdiameters. diameter isthedistance rocky. haveThey thinatmospheres andsmall have large solidcores at theircenters. They The inner planets are very denseand innerplanetsareThe very based on their distance frombased ontheirdistance thesun. The classified be lanets inoursolarsystem can have few moons, andtheirrevolution have fewmoons, times are compared short to the other planetsinthesolarsystem. Planets nottoPlanets scale. 12/28/10 9:43:08 AM

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©© Houghton Houghton Mifflin Mifflin Harcourt Harcourt Publishing Publishing Company Company (t) (t) ©NASA/Corbis; ©NASA/Corbis; (b) (b) ©Science ©Science Source/Photo Source/Photo Researchers, Researchers, Inc.; Inc.; (bkgd) (bkgd) ©PhotoDisc/Getty ©PhotoDisc/Getty Images Images 2. 3. 1. 3. 2. 1. on not live Venus. List three reasons could why people for Home No Me Earth at temperaturesEarth life. that allow have abundant liquidwater, whichhelpsto keep istheonly dioxide.to planetknown Earth carbon atmosphere madeofmostlyoxygen,and nitrogen, isthethirdEarth planetfrom thesun.It hasan Earth planets, hasmanyplanets, volcanoes. like theotherinner Mars, dunes. forming hugesand planet, theentirestorms cover often Giantdust surface. red, rocky the Planet”“Red ofits because the night sky. as isknown Mars in seeMars can you Sometimes Mars 12/28/10 9:43:35 AM 543 sun 5_CNLAESE589428_U12L01S.indd 542 542 as large as it does onEarth. as large asitdoes three times look sun would to Mercury, thesun.On the istheclosestplanet Mercury much like Earth’s moon. isfilledwithcraters,surface Its ofEarth. than halfthesize in oursolarsystem, isless Mercury, thesmallestplanet Mercury than 1,000 volcanoes on Venus’sthan 1,000volcanoes surface. dioxide. Lavacarbon flows from more its atmosphere ismadeup mostly of surface! cloudssurroundThick Venus, and Venus meltat its issohotthat leadwould Venus Earth’s closestneighbors inspace. is notthemoonorastar. ItisVenus, oneof At times,thebrightest objectinthenight sky the innerplanetsare alike. Active Reading Active Reading As you read you ways underline thispage, As inwhich P center, to theotherside. innerplanets The throughfrom its onesideoftheplanet, Aplanet’sdiameters. diameter isthedistance rocky. haveThey thinatmospheres andsmall planets are Mercury, Venus, andMars. Earth, ordertheinner In from closestto farthest, four inner planetsare theclosestto thesun. have large solidcores at theircenters. They The inner planets are very denseand innerplanetsareThe very based on their distance frombased ontheirdistance thesun. The classified be lanets inoursolarsystem can have few moons, andtheirrevolution have fewmoons, times are compared short to the other planetsinthesolarsystem. Planets nottoPlanets scale. 12/28/10 9:43:08 AM

©© Houghton Houghton Mifflin Mifflin Harcourt Harcourt Publishing Publishing Company Company (t) (t) ©NASA/Corbis; ©NASA/Corbis; (b) (b) ©Science ©Science Source/Photo Source/Photo Researchers, Researchers, Inc.; Inc.; (bkgd) (bkgd) ©PhotoDisc/Getty ©PhotoDisc/Getty Images Images 2. 3. 1. 3. 2. 1. on not live Venus. List three reasons could why people for Home No Me Earth at temperaturesEarth life. that allow have abundant liquidwater, whichhelpsto keep istheonly dioxide.to planetknown Earth carbon atmosphere madeofmostlyoxygen,and nitrogen, isthethirdEarth planetfrom thesun.It hasan Earth planets, hasmanyplanets, volcanoes. like theotherinner Mars, dunes. forming hugesand planet, theentirestorms cover often Giantdust surface. red, rocky the Planet”“Red ofits because the night sky. as isknown Mars in seeMars can you Sometimes Mars 12/28/10 9:43:35 AM 543 sun 5_CNLAESE589428_U12L01S.indd 544 544 one of theouterplanetsinoursolarsystem. theouterplanetsinoursolarsystem. one of one of brightbright starinthenight starinthenight sky. sky. Butinfact, Butinfact, Jupiteris Jupiteris On aclearnight, Jupitermight appeartobealarge, planets are alike. ways underline page, inwhichtheouter Active Reading Active Reading Voyager in1979. probe 1space wererings the discovered by Jupiter’sspinning storms. faint are redThe massive, spots aswidethree Earths. is about inside Jupiter! Its Great Spot Red fit the otherplanetswould allof the solarsystem. fact, In Jupiter isthelargest planetin Jupiter As you read you this As Like Jupiter, haslarge storms. Saturn Saturn’s are found insidetheserings. moons of Some andchunksofrock. made upofice aroundthousands ofrings it. are rings The has largest thesecond planet, Saturn, Saturn and their cores are very small. small. and theircores are very of gases. don’tThey have asolidsurface, are they hugeandmadeupmostly because outer planetsare thegasgiants, alsocalled are planetsfrom thefarthest thesun. The than thoseoftheotherouter planets. systems. Saturn’s system ring ismore visible outer andring planetshave many moons ofthe All thantheinnerplanets. colder from are thesun,theirsurfaces much J the outer planets. In that In order,the outer planets. they upiter, Uranus, Saturn, are andNeptune Because thegasgiantsare sofarawayBecause Planets nottoPlanets scale. Spot Great Red 12/28/10 9:44:24 AM

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©© Houghton Houghton Mifflin Mifflin Harcourt Harcourt Publishing Publishing Company Company (tc) (tc) ©Getty ©Getty Images Images Royalty Royalty Free; Free; (Jupiter) (Jupiter) ©NASA/JPL/University ©NASA/JPL/University of of Arizona; Arizona; (Saturn) (Saturn) ©NASA/JPL; ©NASA/JPL; (Uranus) (Uranus) ©Getty ©Getty Images Images Royalty Royalty Free; Free; (Neptune) (Neptune) ©NASA; ©NASA; (bc) (bc) ©NASA; ©NASA; (bkgd) (bkgd) ©PhotoDisc/Getty ©PhotoDisc/Getty Images Images about eachoftheouter planets. about Write onethingthat isunique Unique? Them Makes What Neptune Neptune Uranus Saturn Jupiter reform! around hasnine rings Neptune it. to vanish known ofEarth, thesize and about around theplanet. Dark isa storm, Spot spot This (1,243 mi/hr). Neptune’s windsblow These Great 2,000km/hr ofabout at speeds Its windsmove isthewindiestplanet inoursolarsystem.Neptune Neptune of at least13faint rings. to form. Uranus hasasystem brightclouds causing surface, bubble andburstonto the inside Uranus, heated gases last more Deep than20years! makesThis seasonsonUranus itrotatesplanets, onitsside. compared to other far that, axisofUranusThe istilted so Uranus 12/28/10 9:44:55 AM 545 sun 5_CNLAESE589428_U12L01S.indd 544 544 one of theouterplanetsinoursolarsystem. theouterplanetsinoursolarsystem. one of one of brightbright starinthenight starinthenight sky. sky. Butinfact, Butinfact, Jupiteris Jupiteris On aclearnight, Jupitermight appeartobealarge, planets are alike. ways underline page, inwhichtheouter Active Reading Active Reading Voyager in1979. probe 1space wererings the discovered by Jupiter’sspinning storms. faint are redThe massive, spots aswidethree Earths. is about inside Jupiter! Its Great Spot Red fit the otherplanetswould allof the solarsystem. fact, In Jupiter isthelargest planetin Jupiter As you read you this As Like Jupiter, haslarge storms. Saturn Saturn’s are found insidetheserings. moons of Some andchunksofrock. made upofice aroundthousands ofrings it. are rings The has largest thesecond planet, Saturn, Saturn than thoseoftheotherouter planets. systems. Saturn’s system ring ismore visible outer andring planetshave many moons ofthe All thantheinnerplanets. colder from are thesun,theirsurfaces much small. and theircores are very of gases. don’tThey have asolidsurface, are they hugeandmadeupmostly because outer planetsare thegasgiants, alsocalled are planetsfrom thefarthest thesun. The J the outer planets. In that In order,the outer planets. they upiter, Uranus, Saturn, are andNeptune Because thegasgiantsare sofarawayBecause Planets nottoPlanets scale. Spot Great Red 12/28/10 9:44:24 AM

outer planets:top –88 to 58 –216 –178 –148 –214 462 of Moons Number 71.30 0.70 27 1.33 61 63 31.76 13 3.94 2 5.24 0 5.52 1 (g/cm Density 3 ) Diameter (3,031mi) 4,878 km (31,763 mi) 51,118 km (74,898 mi) 120,536 km (88,846 mi) 142,984 km (4,222 mi) 6,794 km (7,521 mi) 12,104 km (7,926 mi) 12,756 km (30,775 mi) 49,528 km 12/28/10 9:45:09 AM

outer planets:top –88 to 58 –214 –216 –178 –148 462 of Moons Number 31.76 1.30 13 0.70 27 1.33 61 63 3.94 5.52 2 5.24 1 0 (g/cm Density 3 ) Diameter (30,775 mi) 49,528 km (31,763 mi) 51,118 km (74,898 mi) 120,536 km (88,846 mi) 142,984 km (4,222 mi) 6,794 km (7,926 mi) 12,756 km (7,521 mi) 12,104 km (3,031mi) 4,878 km 12/28/10 9:45:09 AM

© Houghton Mifflin Harcourt Publishing Company (bkgd) ©Stocktrek Images/Corbis How How do the average densities compare? Outer planets: planets: Inner for thefour outer planets. Repeat ofthefour innerplanets. density below, thespace In find theaverage Find anAverage data between theinnerandouter planets. data between trends inthe two at thedata tableontheprevious Describe page. Look Patterns inData water. sink. would Earth of islessthan thedensity density its float because would Saturn 1 gramcentimeter cubic (g/cm per ofwater density The is 12/28/10 9:45:30 AM 547 3 ). 5_CNLAESE589428_U12L01S.indd 548 548 about some of them. about someof the sun.Let’s findoutmore many otherbodiesthat orbit Besides planets,there are about asteroids. about facts two findandunderline pages, two Active Reading Active Reading discovered in2002. study. Quaoar, was above, shown arebelt. faraway objects These andhard to Neptune’sbeyond theKuiper called orbit are found ina region ofthesolar system Most crossorbits ofotherbodies. theorbits whose planets are nearly round bodies it was reclassified asadwarf Dwarf planet. ButPluto was in2006, aplanet. called once Dwarf Planets As you read you these As own moons! own asteroids have their Some even up anocean. fill could Others block. are assmall asacity asteroids. Some belt astheasteroid known andJupiter Mars the wideregion between ofthemare thesun. Millions foundorbit in are that andiron Asteroids rock objects solar system. in the ofany body volcanoes the mostactive Another ofJupiter’sAnother [ Io moons, underalayer ofice. have aliquidocean Europa,moon. oneofJupiter’s may moons, different from are Earth’s very moons Other Io Asteroids Moons EYE • oh], has 12/28/10 9:45:55 AM

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©© HoughtonHoughton MifflinMifflin HarcourtHarcourt PublishingPublishing CompanyCompany (cl) (cl) ©Ambient©Ambient ImagesImages Inc./Alamy;Inc./Alamy; (bkgd)(bkgd) ©Dennis©Dennis didi Cicco/CorbisCicco/Corbis . are meteorites called Meteoroids that reach Earth’s surface . a streak ameteor oflight called upinEarth’sburn atmosphere, causing travel through meteoroids Most space. that breakrock offofasteroids and are of pieces atmosphere. Meteoroids day,Each tons ofmeteoroids hitEarth’s and Meteorites Meteoroids, Meteors, away from thesun. Acomet’slong tails. tailsalways point the sun’s visibleas light andbecome gases anddust. reflect particles These to break awaybegins into andturn oftheirfrozen the sun,part surface passcloseto comets around thesun.As Comets have longorbits anddust. ice, isachunkoffrozenA comet rock, gases, Comets sun. Put eachtail. aTover toward thedirection to indicate the thedrawingIn putanS ofacomet, Where’s theSun? 12/28/10 9:46:10 AM 549 5_CNLAESE589428_U12L01S.indd 548 548 about some of them. about someof the sun.Let’s findoutmore many otherbodiesthat orbit Besides planets,there are about asteroids. about facts two findandunderline pages, two Active Reading Active Reading discovered in2002. study. Quaoar, was above, shown arebelt. faraway objects These andhard to Neptune’sbeyond theKuiper called orbit are found ina region ofthesolar system Most crossorbits ofotherbodies. theorbits whose planets are nearly round bodies it was reclassified asadwarf Dwarf planet. ButPluto was in2006, aplanet. called once Dwarf Planets As you read you these As own moons! own asteroids have their Some even up anocean. fill could Others block. are assmall asacity asteroids. Some belt astheasteroid known andJupiter Mars the wideregion between ofthemare thesun. Millions foundorbit in are that andiron Asteroids rock objects solar system. in the ofany body volcanoes the mostactive Another ofJupiter’sAnother [ Io moons, underalayer ofice. have aliquidocean Europa,moon. oneofJupiter’s may moons, different from are Earth’s very moons Other Io Asteroids Moons EYE • oh], has 12/28/10 9:45:55 AM

©© HoughtonHoughton MifflinMifflin HarcourtHarcourt PublishingPublishing CompanyCompany (cl) (cl) ©Ambient©Ambient ImagesImages Inc./Alamy;Inc./Alamy; (bkgd)(bkgd) ©Dennis©Dennis didi Cicco/CorbisCicco/Corbis . are meteorites called Meteoroids that reach Earth’s surface . a streak ameteor oflight called upinEarth’sburn atmosphere, causing travel through meteoroids Most space. that breakrock offofasteroids and are of pieces atmosphere. Meteoroids day,Each tons ofmeteoroids hitEarth’s and Meteorites Meteoroids, Meteors, away from thesun. Acomet’slong tails. tailsalways point the sun’s visibleas light andbecome gases anddust. reflect particles These to break awaybegins into andturn oftheirfrozen the sun,part surface passcloseto comets around thesun.As Comets have longorbits anddust. ice, isachunkoffrozenA comet rock, gases, Comets sun. Put eachtail. aTover toward thedirection to indicate the thedrawingIn putanS ofacomet, Where’s theSun? 12/28/10 9:46:10 AM 549 5_CNLAESE589428_U12L01S.indd 550 550 objects that may cross Earth’s orbit. objects hiteachother. Scientistslookoutfor Often, nothinghapppens.Butsometimesthe Some objectsinspace cross eachothers’ orbits. P to determine if the objects could impact Earth. impact could to determine iftheobjects andmotion. position, size, analyzeThey thisdata cross Earth’s keep track Scientists orbit. of their near-Earth asteroids that are may. These objects often. not happen Luckily,all thedinosaurs. like that onedo impacts changesintheenvironmentit caused that killed ago. 65millionyears scientists Many think about Earth ahugeoneimpacted fact, In hit Earth. probe. space were taken theGalileo by Jupiterimpacted oftheimpact in1994.Pictures solar system. 9 namedShoemaker-Levy Acomet found onthemoon’s be can sizes surface. craters Impact the moon. ofall orhit, impacted, meteoroids,such ascomets, andasteroids have Scientists use telescopes to scan space for space to scan usetelescopes Scientists thathave large also know objects Scientists inthe have alsohitotherbodies objects Space story. objects space millionsofyears, Over tell a ofthemoon ofthesurface ictures Why ItMatters its surface. to form on spots asdark well into Jupiter’s atmosphere, as bubblesofhotgastocaused rise 9 ofShoemaker-Levy impact The 12/28/10 9:46:51 AM

© Houghton Mifflin Harcourt Publishing Company (tl) ©Charles O’Rear/Corbis; (c) ©SPL/Photo Researchers, Inc.; (br) ©Lester Lefkowitz/Getty Images shows evidence of an impact onEarth. ofanimpact shows evidence of impacts. circleThen that apicture

On these pages, underline effects effects underline thesepages, On greater than50km 25–50km 10–25km CraterImpact Diameter movement of objects inspace. of objects movement that enablescientists to track the telescopes Observatories have powerful years ago.years 50,000 about that struck Earth wasArizona, formed by ameteorite Meteor Crater, Barringer The in crater sites from around theworld. Earth! mapshowsThis someimpact anywhere on happen can Impacts 12/28/10 9:47:25 AM 551 5_CNLAESE589428_U12L01S.indd 550 550 objects that may cross Earth’s orbit. objects hiteachother. Scientistslookoutfor Often, nothinghapppens.Butsometimesthe Some objectsinspace cross eachothers’ orbits. P to determine if the objects could impact Earth. impact could to determine iftheobjects andmotion. position, size, analyzeThey thisdata cross Earth’s keep track Scientists orbit. of their near-Earth asteroids that are may. These objects often. not happen Luckily,all thedinosaurs. like that onedo impacts changesintheenvironmentit caused that killed ago. 65millionyears scientists Many think about Earth ahugeoneimpacted fact, In hit Earth. probe. space were taken theGalileo by Jupiterimpacted oftheimpact in1994.Pictures solar system. 9 namedShoemaker-Levy Acomet found onthemoon’s be can sizes surface. craters Impact the moon. ofall orhit, impacted, meteoroids,such ascomets, andasteroids have Scientists use telescopes to scan space for space to scan usetelescopes Scientists thathave large also know objects Scientists inthe have alsohitotherbodies objects Space story. objects space millionsofyears, Over tell a ofthemoon ofthesurface ictures Why ItMatters its surface. to form on spots asdark well into Jupiter’s atmosphere, as bubblesofhotgastocaused rise 9 ofShoemaker-Levy impact The 12/28/10 9:46:51 AM

Read the summary, and then place the information in the list Word Play into the correct box below. The sun is at the center of the solar system. Planets, dwarf planets, moons, and other Use each of the terms in the box to label the objects in the diagram below. smaller objects make up the solar system. The eight planets in the solar system can be planet comet asteroid solar system dwarf planet divided into inner planets and outer planets. Each group has different characteristics. moon orbit gas giant sun * Key Lesson Vocabulary small and dense longer revolutions many moons few moons (x 1) Pluto giant size closest to sun gaseous surface low density 9. rings rocky surface 1. Neptune (x 27) Uranus Inner Planets Outer Planets (x 13) 7. 8.

Jupiter Saturn (x 63) (x 61)

5. Fill in the missing information to describe the object shown below.

6. 4.

a. Object Type:

b. Space Neighbors: Mercury Earth c. Key Feature: Mars d. How It’s Different from Earth:

Io 2. 3.

Venus

so it orbits the sun. Io is farther from the sun than Earth. than sun the from farther is Io sun. the orbits it so

3a. moon 3b. Jupiter and its other moons 3c. active volcanoes 3d. Io orbits a planet. Earth is a planet, planet, a is Earth planet. a orbits Io 3d. volcanoes active 3c. moons other its and Jupiter 3b. moon 3a.

2. Outer Planets: gaseous surface, giant size, rings, many moons, low density, longer revolutions longer density, low moons, many rings, size, giant surface, gaseous Planets: Outer 2. Answer Key: 1. Inner Planets: small and dense, rocky surface, few moons, closest to sun to closest moons, few surface, rocky dense, and small Planets: Inner 1. Key: Answer © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company 552 © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company 553

5_CNLAESE589428_U12L01A.indd 552 12/28/10 9:41:26 AM 5_CNLAESE589428_U12L01A.indd 553 12/28/10 9:41:31 AM Sum It Up! 1 Name

Jupiter Saturn (x 63) (x 61)

5. Fill in the missing information to describe the object shown below.

6. 4.

a. Object Type:

b. Space Neighbors: Mercury Earth c. Key Feature: Mars d. How It’s Different from Earth:

Io 2. 3.

Venus

so it orbits the sun. Io is farther from the sun than Earth. than sun the from farther is Io sun. the orbits it so

5_CNLAESE589428_U12L01A.indd 552 12/28/10 9:41:26 AM 5_CNLAESE589428_U12L01A.indd 553 12/28/10 9:41:31 AM Apply Concepts Name 1

In the space below, draw pictures to show the key physical characteristics of an Identify each of the following large objects in the solar system. inner planet and an outer planet. Then describe your drawings. Write how you are able to identify each one.

Describe the features of a comet.

What is a meteoroid, and how does it become a meteorite? A scientist discovers an object in the solar system. She describes it as bigger than an asteroid, smaller than Mercury, and farther from the sun than Neptune. What kind of object could it be? Explain.

554 © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company 555

5_CNLAESE589428_U12L01A.indd 554 12/28/10 9:41:33 AM 5_CNLAESE589428_U12L01A.indd 555 12/28/10 9:41:35 AM Apply Concepts Name 1

Describe the features of a comet.

554 © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company 555

5_CNLAESE589428_U12L01A.indd 554 12/28/10 9:41:33 AM 5_CNLAESE589428_U12L01A.indd 555 12/28/10 9:41:35 AM 5_CNLAESE589428_U12L01A.indd 556 556 object. withplanetsandmoons? istherecollide evidence What object. that theseobjects the anddescribe Label Draw aplanet. that might impact ofanobject apicture an asteroid andacomet. Complete the Venn diagram inorder to compare andcontrast find them. are inthenight sky.They among thebrightest objects sky. Find outwhere theseplanetsmay inthesky appear. can ifyou See of thelocation Venus, give andJupiter newspapers Many inthe Mars, Asteroid Both Comet 12/28/10 9:41:36 AM

© Houghton Mifflin Harcourt Publishing Company (bkgd) ©PhotoDisc/Getty Images; (all else) ©NASA miles in15days! than sixmillion traveled more Chawla Kalpana mission, herfirst On Claudia Alexander Meet Two Space Explorers Space Kalpana Chawla of Jupiter anditsmoons. spacecraft to take detailed photos was Galileo thefirst her command, 385millionmiles!Under it over Jupiter. directed Alexander Claudia to reach sixlongyears It took spacecraft in1989. Earth left spacecraft to Jupiter. The mission sent anunmanned of NASA’s mission. Galileo The planet Jupiter. was She incharge ofthe studiesthemoons She Earth! leaves too. Butspace, shenever explores Alexander Claudia outer Indian-born woman inspace! woman Indian-born thefirst Chawla became Kalpana Soon, anastronaut. and became for NASA to work went She space. kept dreaming. wanted She to fly in dreams true! hadcome But she fly manyHer ofairplanes. kinds engineer. Chawla could Kalpana herdegreeearned asanaerospace States andstudiedhard. soon She to theUnited came She airplanes. Chawla flying dreamed about Kalpana inIndia, alittlegirl As space probe Galileo 12/28/10 9:11:55 PM 557 5_CNLAESE589428_U12L01A.indd 556 556 object. withplanetsandmoons? istherecollide evidence What object. that theseobjects the anddescribe Label Draw aplanet. that might impact ofanobject apicture an asteroid andacomet. Complete the Venn diagram inorder to compare andcontrast find them. are inthenight sky.They among thebrightest objects sky. Find outwhere theseplanetsmay inthesky appear. can ifyou See of thelocation Venus, give andJupiter newspapers Many inthe Mars, Asteroid Both Comet 12/28/10 9:41:36 AM

© Houghton Mifflin Harcourt Publishing Company (bkgd) ©PhotoDisc/Getty Images; (all else) ©NASA miles in15days! than sixmillion traveled more Chawla Kalpana mission, herfirst On Claudia Alexander Meet Two Space Explorers Space Kalpana Chawla of Jupiter anditsmoons. spacecraft to take detailed photos was Galileo thefirst her command, 385millionmiles!Under it over Jupiter. directed Alexander Claudia to reach sixlongyears It took spacecraft in1989. Earth left spacecraft to Jupiter. The mission sent anunmanned of NASA’s mission. Galileo The planet Jupiter. was She incharge ofthe studiesthemoons She Earth! leaves too. Butspace, shenever explores Alexander Claudia outer Indian-born woman inspace! woman Indian-born thefirst Chawla became Kalpana Soon, anastronaut. and became for NASA to work went She space. kept dreaming. wanted She to fly in dreams true! hadcome But she fly manyHer ofairplanes. kinds engineer. Chawla could Kalpana herdegreeearned asanaerospace States andstudiedhard. soon She to theUnited came She airplanes. Chawla flying dreamed about Kalpana inIndia, alittlegirl As space probe Galileo 12/28/10 9:11:55 PM 557 5_CNLAESE589428_U12PS.indd 558 558 Earth. highabove orbit fromof space its scientists pictures Telescope sends Space Hubble The the correct circle.the correct statements that apply to eachscientist in study indifferent space ways. Write the Chawla Alexander andClaudia Kalpana WaysTwo toStudySpace ______Claudia Alexander I study objects• in space. • I grew up in India and learned I study the• moons of Jupiter. I traveled• on the space shuttle. • I lead space missions without to fly many types of airplanes. leaving Earth. ______Kalpana Chawla this one, inanobservatory.this one, suchas usingatelescope, by Earth scientistsMany study from space 12/28/10 9:12:37 PM

© Houghton Mifflin Harcourt Publishing Company object indifferentobject ways? the willobserve Why thinkyou doyou theProcedure About Think investigation? from willlearn thinkyou this doyou What aPurpose Set Name as ateam inthisinvestigation? together work that you Why isitimportant How Do We Observe Observe We Do How the Solar System? Solar the in Objects Observe We Do How your Science Notebook. Science your in observations Record your aspossible. observations from faraway. asmany Make object assigned your Observe model di observations. erent kindsof objects inthesolarsystem. You will scientists observe andrecord data about In thisactivity, you willinvestigate ways Solar System? Solar Objects in the the in Objects binoculars ofsolarsystem objects poster Materials your observations. observations. your Record the sameobject. to observe Use binoculars Essential Question Essential return themto thegroup. and those observations have anotherstudent gather Afteramoment, observations. walk andrecord to theposter group ofyour Have onemember space andsenddataspace backto Earth. usedto explorevehicle in objects Wise the for Word A isacrewless space probe A space Review theanswers. Review theobject. standing by questions to thestudent the Send the object. questionsabout new andwriteobservations agroup,As review the Inquiry Flipchart page59 Flipchart Inquiry you madeusingallthreeyou methods. below, thespace In record theobservations Record Your Data 2 12/28/10 9:40:55 AM 559 5_CNLAESE589428_U12PS.indd 558 558 Earth. highabove orbit fromof space its scientists pictures Telescope sends Space Hubble The the correct circle.the correct statements that apply to eachscientist in study indifferent space ways. Write the Chawla Alexander andClaudia Kalpana WaysTwo toStudySpace ______Claudia Alexander I study objects• in space. • I grew up in India and learned I study the• moons of Jupiter. I traveled• on the space shuttle. • I lead space missions without to fly many types of airplanes. leaving Earth. ______Kalpana Chawla this one, inanobservatory.this one, suchas usingatelescope, by Earth scientistsMany study from space 12/28/10 9:12:37 PM

© Houghton Mifflin Harcourt Publishing Company as ateam inthisinvestigation? together work that you Why isitimportant indifferentobject ways? the willobserve Why thinkyou doyou theProcedure About Think investigation? from willlearn thinkyou this doyou What aPurpose Set Name How Do We Observe Observe We Do How the Solar System? Solar the in Objects Observe We Do How your Science Notebook. Science your in observations Record your aspossible. observations from faraway. asmany Make object assigned your Observe model di observations. erent kindsof objects inthesolarsystem. You will scientists observe andrecord data about In thisactivity, you willinvestigate ways Solar System? Solar Objects in the the in Objects binoculars ofsolarsystem objects poster Materials your observations. observations. your Record the sameobject. to observe Use binoculars Essential Question Essential return themto thegroup. and those observations have anotherstudent gather Afteramoment, observations. walk andrecord to theposter group ofyour Have onemember space andsenddataspace backto Earth. usedto explorevehicle in objects Wise the for Word A isacrewless space probe A space Review theanswers. Review theobject. standing by questions to thestudent the Send the object. questionsabout new andwriteobservations agroup,As review the Inquiry Flipchart page59 Flipchart Inquiry you madeusingallthreeyou methods. below, thespace In record theobservations Record Your Data 2 12/28/10 9:40:55 AM 559 5_CNLAESE589428_U12L02I.indd 560 560 How did your observations from observations didyour How far 1. andExtendAnalyze represent? upclose theobject didviewing What represent? didusingbinoculars What far away represent? from theobject space. didobserving What in objects scientists view how about Think Draw Conclusions binoculars? Give anexample. Give binoculars? away differ from thosemadeusing Think of other questions you would would ofotherquestionsyou Think 5. inthesolar objects about Think 4. helpscientists probes dospace How 3. made observations didyour How 2. objects in space. inspace. objects Write questions. your scientists study how like to askabout them? relationshipsspace to observe system. doscientists usetimeand How inspace? objects about learn walked anexample. Give to theposter? madewhenastudentobservations differ from the using binoculars 12/28/10 9:40:56 AM

© Houghton Mifflin Harcourt Publishing Company (bkgd) ©Stocktrek Images/Corbis and Galaxies? What Are Stars Question Essential make notes intheInteractive Glossary. eachone, about learn you As List theterms. Lesson Vocabulary when these particles come together? come when theseparticles inspace. small particles happens What isnotcompletelySpace empty. There are question inthislessonandrecord ithere. Find to thefollowing theanswer Active Reading Active Reading facts about atopic. about facts wordssignal that identify examples and are they to alert readwhat they because readers remember Active addedfacts. signal andinfact examplessignal ofanidea. Also as andsuch instance, for For example, ideas. between words connections Signal show Signal Words: Details of gasanddust. here, isagiant cloud Pelican shown Nebula A nebula,suchasthe 3 12/28/10 9:40:35 AM 561 5_CNLAESE589428_U12L02I.indd 560 560 How did your observations from observations didyour How far 1. andExtendAnalyze represent? upclose theobject didviewing What represent? didusingbinoculars What far away represent? from theobject space. didobserving What in objects scientists view how about Think Draw Conclusions binoculars? Give anexample. Give binoculars? away differ from thosemadeusing Think of other questions you would would ofotherquestionsyou Think 5. inthesolar objects about Think 4. helpscientists probes dospace How 3. made observations didyour How 2. objects in space. inspace. objects Write questions. your scientists study how like to askabout them? relationshipsspace to observe system. doscientists usetimeand How inspace? objects about learn walked anexample. Give to theposter? madewhenastudentobservations differ from the using binoculars 12/28/10 9:40:56 AM

You see stars as tiny points of eople have always looked at objects A STAR IS BORN For example, blue stars are the hottest. A in the sky. Astronomy is the study of blue star’s average temperature is about white light in the night sky. P Stars form when gravity causes gas objects in space and their characteristics. 15,000 ºC. and dust particles found in space to pull Stars are not tiny, and they Astronomers are scientists who study space Stars have a wide range of sizes. White together. These particles are squeezed and everything in it. They use many types of dwarf stars, for instance, can be as small as a are not all white. Find out together under great pressure. Eventually, telescopes to observe objects in space, such planet. Giant and supergiant stars are many energy stored in the particles is released as how scientists study stars. as stars and planets. times bigger than the average-size star. The heat and light. A star is born. Stars are huge balls of hot, glowing largest stars are also usually the brightest. A Active Reading Stars are classified by their color, As you read these two gases that produce their own heat and star’s brightness is related to the amount of pages, draw boxes around words or phrases temperature, brightness, and size. The color light. The sun is the star you know the most visible light it gives off. that signal a detail or an added fact. of a star can tell us about its temperature. about. It seems much larger than other stars only because it is much closer to Earth. Super Hot and Just Hot Draw a rectangle around the hottest stars in the diagram. Draw a circle around the brightest stars. Dividing by 3-digit Numbers Blue Giant Super Giant A small telescope magnifies objects 150 times. A large observatory Red Giant telescope magnifies an object 3,300 times. How many times as great is the magnification of the observatory telescope than the small telescope? Brightest sun

White Dwarf

Temperature

562 © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company (br) ©TONY GENTILE/Reuters/Corbis; (bkgd) ©Stephen Studd/Getty Images (br) ©TONY GENTILE/Reuters/Corbis; (bkgd) ©Stephen Studd/Getty Images © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company (t) ©Gregory MacNicol/Photo Researchers, Inc.; (bl) ©TONY GENTILE/Reuters/Corbis; (bkgd) ©Stephen Studd/Getty Images (t) ©Gregory MacNicol/Photo Researchers, Inc.; (bl) ©TONY GENTILE/Reuters/Corbis; (bkgd) ©Stephen Studd/Getty Images 563

5_CNLAESE589428_U12L03S.indd 562 12/28/10 9:48:44 AM 5_CNLAESE589428_U12L03S.indd 563 12/28/10 9:49:20 AM The sun is a medium-size yellow star. Many stars are larger or hotter than the sun. A supergiant, for example, can be more than 100 times the size of the sun.

White Dwarf

Temperature

5_CNLAESE589428_U12L03S.indd 562 12/28/10 9:48:44 AM 5_CNLAESE589428_U12L03S.indd 563 12/28/10 9:49:20 AM In the space below, describe the position GOING of the solar system within the Milky Way. GALACTIC Our solar system is huge. Yet it is only a tiny part of a FEATURES OF GALAXIES much larger system in space. Our sun is one star in a group A galaxy is a group of billions of stars, TYPES OF GALAXIES the objects that orbit the stars, gas, and of billions of stars found in the Milky Way galaxy. In the 1920s, astronomer Edwin Hubble dust. A galaxy is held together by gravity. was the first to study galaxies. He classified There are billions of galaxies in the Active Reading As you read the next four pages, circle details about the them by shape. Through his telescope, universe. Galaxies are separated by large ages of stars in each type of galaxy. Hubble observed pinwheel-like groups of distances. On a cloudless night, you might stars that he called spiral galaxies. see what looks like a faint band of clouds Some spiral galaxies, called barred spiral among the stars. This is a part of our home galaxies, have a center shaped like a long galaxy, the Milky Way. Most other galaxies bar. Recent evidence suggests that the Milky Way Galaxy can be seen only by using powerful Milky Way is a barred spiral galaxy. telescopes.

SPIRAL GALAXIES Spiral galaxies consist of a rotating disk of young stars, gas, and dust and a central bulge made of older stars.

YOU ARE HERE BARRED SPIRAL GALAXIES Once, people thought Earth was at the center of the universe. Barred spiral galaxies may have The universe is everything that two or more spiral arms. Unlike exists. Now we know that we are regular spirals, there are young not even at the center of stars at the center of barred our own galaxy! spiral galaxies. © Houghton Mifflin Harcourt Publishing Company (b) ©NASA/JPL-Caltech/R. Hurt (SSC); (bkgd) ©D. Nunuk/Photo Researchers, Inc. © Houghton Mifflin Harcourt Publishing Company (t) ©Getty Images; (b) ©Design Pics Inc./Alamy; (bkgd) ©D. Nunuk/Photo Researchers, Inc.; 564 © Houghton Mifflin Harcourt Publishing Company (b) ©NASA/JPL-Caltech/R. Hurt (SSC); (bkgd) ©D. Nunuk/Photo Researchers, Inc. © Houghton Mifflin Harcourt Publishing Company (t) ©Getty Images; (b) ©Design Pics Inc./Alamy; (bkgd) ©D. Nunuk/Photo Researchers, Inc.; 565

5_CNLAESE589428_U12L03S.indd 564 12/28/10 9:50:00 AM 5_CNLAESE589428_U12L03S.indd 565 12/28/10 9:50:31 AM In the space below, describe the position GOING of the solar system within the Milky Way. GALACTIC Our solar system is huge. Yet it is only a tiny part of a FEATURES OF GALAXIES much larger system in space. Our sun is one star in a group A galaxy is a group of billions of stars, TYPES OF GALAXIES the objects that orbit the stars, gas, and of billions of stars found in the Milky Way galaxy. In the 1920s, astronomer Edwin Hubble dust. A galaxy is held together by gravity. was the first to study galaxies. He classified There are billions of galaxies in the Active Reading As you read the next four pages, circle details about the them by shape. Through his telescope, universe. Galaxies are separated by large ages of stars in each type of galaxy. Hubble observed pinwheel-like groups of distances. On a cloudless night, you might stars that he called spiral galaxies. see what looks like a faint band of clouds Some spiral galaxies, called barred spiral among the stars. This is a part of our home galaxies, have a center shaped like a long galaxy, the Milky Way. Most other galaxies bar. Recent evidence suggests that the Milky Way Galaxy can be seen only by using powerful Milky Way is a barred spiral galaxy. telescopes.

SPIRAL GALAXIES Spiral galaxies consist of a rotating disk of young stars, gas, and dust and a central bulge made of older stars.

5_CNLAESE589428_U12L03S.indd 564 12/28/10 9:50:00 AM 5_CNLAESE589428_U12L03S.indd 565 12/28/10 9:50:31 AM MORE TYPES OF GALAXIES Most of the brightest galaxies in the universe have spiral shapes. But spiral galaxies are not the only type of galaxy. In fact, they make up only about 20 percent of all galaxies. The dimmer irregular COSMIC CRASHES galaxies and elliptical galaxies make up about Sometimes galaxies collide, or crash 80 percent of all galaxies in the universe. together, in space! Why? Gravity pulls galaxies toward IRREGULAR GALAXIES each other. Although galaxies may collide, single stars Irregular galaxies do not have any and planets almost never do. particular shape. The stars are Many things can happen when galaxies collide. randomly scattered. There is lots Often, large amounts of dust and gas are pressed of gas and dust to form new stars. About 20 percent of all galaxies together. This causes a starburst, or rapid formation of are irregular. Some astronomers many new stars. Sometimes, a smaller galaxy becomes think that gravity from nearby part of a larger galaxy. A collision of galaxies can also galaxies causes irregular form a large, irregular galaxy. Scientists believe that galaxies to form. many irregular galaxies were once spiral or elliptical ELLIPTICAL GALAXIES galaxies that were involved in a cosmic crash. Elliptical galaxies are brightest at their center. About 60 percent of all galaxies in the universe are Galaxies do not stand still. They are elliptical. They can be shaped like always moving. Galaxies can move away a perfect sphere or a flattened from each other or toward each other. globe. Large ellipticals are made up of old stars and have too little dust or gas to form Look at pictures 1–5. Draw a picture to new ones. show what you think will happen next to these two galaxies. Write a sentence to describe it. © Houghton Mifflin Harcourt Publishing Company (tl) ©NASA, ESA, and Science B. Institute); Whitmore (Space (br) Telescope ©Stocktrek Images/Getty Images; (bkgd) ©Scott Smith/Corbis © Houghton Mifflin Harcourt Publishing Company (all insets) ©Max Planck Institute for Astrophysics/Photo Researchers, Inc.; (bkgd) ©Scott Smith/Corbis © Houghton Mifflin Harcourt Publishing Company (tl) ©NASA, ESA, and Science B. Institute); Whitmore (Space (br) Telescope ©Stocktrek Images/Getty Images; (bkgd) ©Scott Smith/Corbis 566 © Houghton Mifflin Harcourt Publishing Company (all insets) ©Max Planck Institute for Astrophysics/Photo Researchers, Inc.; (bkgd) ©Scott Smith/Corbis 567

5_CNLAESE589428_U12L03S.indd 566 12/28/10 9:51:03 AM 5_CNLAESE589428_U12L03S.indd 567 12/28/10 9:51:23 AM MORE TYPES OF GALAXIES Most of the brightest galaxies in the universe have spiral shapes. But spiral galaxies are not the only type of galaxy. In fact, they make up only about 20 percent of all galaxies. The dimmer irregular COSMIC CRASHES galaxies and elliptical galaxies make up about Sometimes galaxies collide, or crash 80 percent of all galaxies in the universe. together, in space! Why? Gravity pulls galaxies toward IRREGULAR GALAXIES each other. Although galaxies may collide, single stars Irregular galaxies do not have any and planets almost never do. particular shape. The stars are Many things can happen when galaxies collide. randomly scattered. There is lots Often, large amounts of dust and gas are pressed of gas and dust to form new stars. About 20 percent of all galaxies together. This causes a starburst, or rapid formation of are irregular. Some astronomers many new stars. Sometimes, a smaller galaxy becomes think that gravity from nearby part of a larger galaxy. A collision of galaxies can also galaxies causes irregular form a large, irregular galaxy. Scientists believe that galaxies to form. many irregular galaxies were once spiral or elliptical ELLIPTICAL GALAXIES galaxies that were involved in a cosmic crash. Elliptical galaxies are brightest at their center. About 60 percent of all galaxies in the universe are Galaxies do not stand still. They are elliptical. They can be shaped like always moving. Galaxies can move away a perfect sphere or a flattened from each other or toward each other. globe. Large ellipticals are made up of old stars and have too little dust or gas to form Look at pictures 1–5. Draw a picture to new ones. show what you think will happen next to these two galaxies. Write a sentence to describe it. © Houghton Mifflin Harcourt Publishing Company (tl) ©NASA, ESA, and Science B. Institute); Whitmore (Space (br) Telescope ©Stocktrek Images/Getty Images; (bkgd) ©Scott Smith/Corbis © Houghton Mifflin Harcourt Publishing Company (all insets) ©Max Planck Institute for Astrophysics/Photo Researchers, Inc.; (bkgd) ©Scott Smith/Corbis © Houghton Mifflin Harcourt Publishing Company (tl) ©NASA, ESA, and Science B. Institute); Whitmore (Space (br) Telescope ©Stocktrek Images/Getty Images; (bkgd) ©Scott Smith/Corbis 566 © Houghton Mifflin Harcourt Publishing Company (all insets) ©Max Planck Institute for Astrophysics/Photo Researchers, Inc.; (bkgd) ©Scott Smith/Corbis 567

5_CNLAESE589428_U12L03S.indd 566 12/28/10 9:51:03 AM 5_CNLAESE589428_U12L03S.indd 567 12/28/10 9:51:23 AM Sum It Up! 3 Name When you’re done, use the answer key to check and revise your work. The universe is composed of billions of galaxies. Dust, gas, and billions of stars make Word Play up a galaxy. The idea web below summarizes information about stars and galaxies. Complete it using the words and phrases from the box. Complete the puzzle. If you need help, use the words in the box below the clues.

1 2

Types of Galaxies Elliptical Temperature 3 Spiral Characteristics of Stars Size 4 5 6 7 Color Irregular 8

Barred spiral 9

Across Down 1. A person who studies the universe 2. A pinwheel-like galaxy 4. A galaxy with no particular shape 3. A group of stars, dust, and gases 8. Characteristic that is related to a star’s 5. A galaxy shaped like a flattened globe temperature 6. Everything that exists—planets, stars, 9. A ball of hot, glowing gases dust, and gases 7. The study of the objects in space and their properties Brightness spiral elliptical astronomy* irregular galaxy* star*

astronomer color universe* * Key Lesson Vocabulary

6–8 (in any order): Color; Size; Temperature Temperature Size; Color; order): any (in 6–8 568 Stars of Characteristics 5. Galaxies of Types 4. Irregular Elliptical; Spiral; order): any (in 1–3 Key: Answer © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin Harcourt Publishing Company 569

5_CNLAESE589428_U12L03A.indd 568 12/28/10 9:41:08 AM 5_CNLAESE589428_U12L03A.indd 569 12/28/10 9:41:10 AM Sum It Up! 3 Name When you’re done, use the answer key to check and revise your work. The universe is composed of billions of galaxies. Dust, gas, and billions of stars make Word Play up a galaxy. The idea web below summarizes information about stars and galaxies. Complete it using the words and phrases from the box. Complete the puzzle. If you need help, use the words in the box below the clues.

1 2

Types of Galaxies Elliptical Temperature 3 Spiral Characteristics of Stars Size 4 5 6 7 Color Irregular 8

Barred spiral 9

astronomer color universe* * Key Lesson Vocabulary

5_CNLAESE589428_U12L03A.indd 568 12/28/10 9:41:08 AM 5_CNLAESE589428_U12L03A.indd 569 12/28/10 9:41:10 AM Apply Concepts

What are some ways in which galaxies differ? Tools in Space An astronaut often has to use screwdrivers or drills to fix things in space. The Look at this picture of a spiral galaxy. Draw a picture of a barred spiral galaxy. astronaut’s tools are specially designed for a person wearing bulky gloves and floating in orbit. Hand tools must work in the extreme cold vacuum of space and be tethered so they don’t float away. A robotic arm helps the astronaut move around outside. However, the astronaut’s most important tool is the spacesuit that maintains an environment in which the astronaut can live.

Tell how the two galaxies are alike and different.

Look at these two stars. Compare and contrast them using at least two properties.

red blue giant star

How do these stars compare to the sun? eshooting Troubl Circle the astronaut’s drill. How is it similar to a drill used on Earth? How is it different?

Find out which are the brightest stars that are visible this time of year in your area. With an adult, observe the stars. Make a diagram of the night sky showing where to find the brightest stars.

5_CNLAESE589428_U12EF.indd 571 12/28/10 5:32:56 PM 5_CNLAESE589428_U12L03A.indd 570 12/28/10 9:41:13 AM Apply Concepts

Tell how the two galaxies are alike and different.

Look at these two stars. Compare and contrast them using at least two properties.

red blue giant star

How do these stars compare to the sun? eshooting Troubl Circle the astronaut’s drill. How is it similar to a drill used on Earth? How is it different?

Find out which are the brightest stars that are visible this time of year in your area. With an adult, observe the stars. Make a diagram of the night sky showing where to find the brightest stars.

5_CNLAESE589428_U12EF.indd 571 12/28/10 5:32:56 PM 5_CNLAESE589428_U12L03A.indd 570 12/28/10 9:41:13 AM Unit 12 Review Name continued Vocabulary Review You are used to doing everything under the pull of Earth’s gravity. asteroid That’s what makes it possible for you feel motions as up, down, and Use the terms in the box to complete the sentences. comet galaxy side-to-side. There is no “right side up” in space! It is harder than Together, a star and all the planets and other objects orbiting it 1. solar system you might think to work in such an unfamiliar environment. form a(n) . star

2. A chunk of rock or iron that is less than 1,000 km (621 mi) in diameter and that orbits the sun is called a(n) . Turn your book so that the top of this page is closest to you. 3. A huge ball of very hot, glowing gases in space that can produce its own heat and light is called a(n) .

4. A group of solar systems that are held together by gravity and classified by shape is called a(n) .

5. The picture shows an example of a(n) . when you turn the page right side up again. up side right page the turn you when

Hold your pencil near the eraser. Write your name on the line above so that it reads properly properly reads it that so above line the on name your Write eraser. the near pencil your Hold Science Concepts Fill in the letter of the choice that best answers the question.

6. Scientists use models to represent or 7. On a clear night, Ram correctly identified What made this task difficult? explain things in the natural world. Why some clouds among the stars as the Milky are models useful for the study of the Way. What part of the Milky Way was solar system? most visible to Ram?

A because models cannot be proved F asteroids How do engineers account for microgravity when designing the inside of a space station? wrong G dust B because models are always accepted H planets by all scientists I stars C because models describe the way things actually are D because models can be used to describe how things work Rise to the engineering design challenge—Complete Improvise It: How High is That Star? in the Inquiry Flipchart. © Houghton Mifflin Harcourt Publishing Company HMH Credits 572 © Houghton Mifflin Harcourt Publishing Company HMH Credits Unit 12 573

5_CNLAESE589428_U12EF.indd 572 12/28/10 6:59:39 PM 5_CNLAESE589428_U12AS.indd 573 12/28/10 5:27:00 PM Unit 12 Review Name continued Vocabulary Review You are used to doing everything under the pull of Earth’s gravity. asteroid That’s what makes it possible for you feel motions as up, down, and Use the terms in the box to complete the sentences. comet galaxy side-to-side. There is no “right side up” in space! It is harder than Together, a star and all the planets and other objects orbiting it 1. solar system you might think to work in such an unfamiliar environment. form a(n) . star

4. A group of solar systems that are held together by gravity and classified by shape is called a(n) .

5. The picture shows an example of a(n) . when you turn the page right side up again. up side right page the turn you when

5_CNLAESE589428_U12EF.indd 572 12/28/10 6:59:39 PM 5_CNLAESE589428_U12AS.indd 573 12/28/10 5:27:00 PM 5_CNLAESE589428_U12AS.indd 574 UNIT 12 574 Fill intheletterofchoicethatbestanswersquestion. Science Concepts Whichofthesestarsproducesthe 8. 9.

High Low Brightness factor determinesastar’scolor? on thediagraminQuestion8,which observe starsofdifferentcolors.Based observatory, Smitausedatelescopeto During aschoolfieldtriptoan most light? some starsthatcanbeseenfromEarth. the color,temperature,andbrightnessof from Earth.Thediagrambelowcompares produces, nothowbrightastarappears to describetheamountoflightastar Astronomers usethetermbrightness C G H D B A F Hot I

Unit 12 Betelgeuse its distancefromEarth its temperature its brightness its size Vega our sun Proxima Centauri White dwarfs Blue White Vega Spica Temperature Color Proxima Centauri Yellow Aldebaran Supergiants sun Orange Betelgeuse Red Giants Cool Whattypeofgroupisthediagram 11. 10. 12. illustrating? orbiting astar. The diagrambelowshowsplanets Which planet is Planet Z most similar to? has a thick atmosphere and a low density. called Planet Z. Planet Z is very large and solar systems. She learns about a planet Ming is doing a project on planets in other distributed withinthiskindofgalaxy? perfect spheres.Howarethestars Some ellipticalgalaxiesappeartobe C G D B B A A F

Mars Earth arms ofspiral galaxies. sphere inbandsthatlook likethe The starsarespreadthroughout the the center. of thespherewithdust cloudsin Most ofthestarsarenearoutside stars, and density decreases farther out. The center is very dense with many throughout thegalaxy. The starsareevenlydistributed the MilkyWay a constellation C H D I

Saturn Mercury a universe a solarsystem 12/28/10 5:27:04 PM

The smallerstar must becloserto Earth. planets? between theorbitsofinnerandouter the sun.Whatismaindifference All theplanetsinsolarsystemorbit is true? same color.Whichpictureandstatement Each picturebelowshowstwostarsofthe There aremanydifferenttypesofstars. The smallerstar must becloserto Earth. The smallerstar must becloserto Earth. The smallerstar must becloserto Earth. C G H D B A F I The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor The smallerstar must behotter. The larger star must bebrighter. StarsStars thatare thatare thesamecolor thesamecolor are usuallly thesamesize. the sun,andinnerplanets donot. The outerplanetsrotate astheyorbit the sunthaninnerplanetsdo. The outerplanetstakelongertoorbit distance thantheouterplanetsdo. The innerplanetstravelagreater orbit indifferentdirections. The innerplanetsandouter The smallerstar must behotter. The larger star must bebrighter. The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor Stars thatare thesamecolor The smallerstar must becloserto Earth. are usuallly thesamesize. are usuallly thesamesize. are usuallly thesamesize. are usuallly thesamesize. are usuallly thesamesize. The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor are usuallly thesamesize. G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Name Whichofthesetypesspaceobjectsis 16. 15.

pass: 1st object wasGalileoobserving? or behindtheplanet.Whatkindofspace and sometimesdisappearedinfrontof four objectsmovedfromnightto four objectsinlinewiththeplanet.These When GalileoobservedJupiter,hesaw Borrelly mostlikelytobe? Earth andtheorbitofBorrelly. The diagrambelowshowstheorbitof 11/09/09 C G H D B A F I pass: 1st 11/09/09 pass: 1st pass: 1st pass: 1st 11/09/09 11/09/09 11/09/09 moons meteoroids solar systems dwarf planets a planet a moon a comet an asteroid pass: 1st 11/09/09 Borrelly Earth G5_EC_00007_5_CFLAEAG365800_8A Unit 12 Sun 12/28/10 5:27:07 PM 575 Dartmouth PublishingDartmouth

UNIT 12 pass: 1st 11/01/09 5_CNLAESE589428_U12AS.indd 574 UNIT 12 574 Fill intheletterofchoicethatbestanswersquestion. Science Concepts 9. Whichofthesestarsproducesthe 8.

Unit 12 its distancefromEarth its temperature its brightness its size Vega our sun Proxima Centauri Betelgeuse White dwarfs Blue White Vega Spica Temperature Color Proxima Centauri Yellow Aldebaran Supergiants sun Orange Betelgeuse Red Giants Cool Whattypeofgroupisthediagram 11. 10. 12. illustrating? orbiting astar. The diagrambelowshowsplanets Which planet is Planet Z most similar to? has a thick atmosphere and a low density. called Planet Z. Planet Z is very large and solar systems. She learns about a planet Ming is doing a project on planets in other distributed withinthiskindofgalaxy? perfect spheres.Howarethestars Some ellipticalgalaxiesappeartobe C G D B B A A F

Saturn Mercury a universe a solarsystem 12/28/10 5:27:04 PM

The smallerstar must becloserto Earth. planets? between theorbitsofinnerandouter the sun.Whatismaindifference All theplanetsinsolarsystemorbit is true? same color.Whichpictureandstatement Each picturebelowshowstwostarsofthe There aremanydifferenttypesofstars. The smallerstar must becloserto Earth. The smallerstar must becloserto Earth. The smallerstar must becloserto Earth. C G H D B A F I The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor The smallerstar must behotter. The larger star must bebrighter. StarsStars thatare thatare thesamecolor thesamecolor are usuallly thesamesize. the sun,andinnerplanets donot. The outerplanetsrotate astheyorbit the sunthaninnerplanetsdo. The outerplanetstakelongertoorbit distance thantheouterplanetsdo. The innerplanetstravelagreater orbit indifferentdirections. The innerplanetsandouter The smallerstar must behotter. The larger star must bebrighter. The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor Stars thatare thesamecolor The smallerstar must becloserto Earth. areare usuallly usuallly thesamesize. thesamesize. are usuallly thesamesize. are usuallly thesamesize. are usuallly thesamesize. The smallerstar must behotter. The larger star must bebrighter. Stars thatare thesamecolor are usuallly thesamesize. G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A G5_EC_00009_5_CFLAEAG365800_85A Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Dartmouth PublishingDartmouth Name Whichofthesetypesspaceobjectsis 16. 15.

pass: 1st object wasGalileoobserving? or behindtheplanet.Whatkindofspace and sometimesdisappearedinfrontof four objectsmovedfromnightto four objectsinlinewiththeplanet.These When GalileoobservedJupiter,hesaw Earth andtheorbitofBorrelly. The diagrambelowshowstheorbitof Borrelly mostlikelytobe? 11/09/09 C G H D B A F I pass: 1st 11/09/09 pass: 1st pass: 1st pass: 1st 11/09/09 11/09/09 11/09/09 moons meteoroids solar systems dwarf planets a planet a moon a comet an asteroid pass: 1st 11/09/09 Borrelly Earth G5_EC_00007_5_CFLAEAG365800_8A Unit 12 Sun 12/28/10 5:27:07 PM 575 Dartmouth PublishingDartmouth

UNIT 12 pass: 1st 11/01/09 5_CNLAESE589428_U12AS.indd 576 UNIT 12 576 b. a. 20. 19. 18. 17. Write theanswerstothesequestions. Apply InquiryandReviewtheBigIdea Observations Questions to thisobservation. how thestructureofourgalaxyandpositionsolarsystemwithinrelate On acloudlessnight,milkybandknownastheMilkyWayisvisiblefromEarth.Explain points oflight.WhatdidGalileo’sobservationsdemonstrateaboutstars? When GalileousedhistelescopetoobservetheMilkyWay,starsappearedassmall be useful. two observationsthatamodeloftheuniverse wouldneedtoexplaininorder People havedevelopedmodelsoftheuniverse forthousandsofyears.Identify use todeterminewhethertheobjectisaplanetorstar? Sofia observesanobjectinthenightsky.Whatquestionsandobservationscanshe Unit 12

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© Houghton Mifflin Harcourt Publishing Company HMH Credits DO NOT EDIT--LODO Number changes must made through be “File info” LOnumber=NC98102 6K_CNLAESE589343_U01AS 52 My Notes 52 Unit 1 The Natureof Science LOnumber=NC98102 NOT EDIT--LODO Number changes must made through be “File info” 6K_CNLAESE589343_U01AS 52 My Notes 52 Unit 1TheNatureofScience 12/18/10 3:07:08AM