ASTRONOMY - Troop 577 Wichita, Kansas€¦ · affect astronomy. 3. With the aid of diagrams (or real telescopes if available), do each of the following: ... With the aid of diagrams,

ASTRONOMY

How to Use This PamphletThe secret to successfully earning a merit badge is for you to use both the pamphlet and the suggestions of your counselor.

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Astronomy

Boy sCoUts oF AmErICAmErIt BADGE sErIEs

Requirements1. Dothefollowing:

a.Describetheproperclothingandotherprecautionsforsafelymakingobservationsatnightandincoldweather.

b.TellhowtosafelyobservetheSun,objectsneartheSun,andtheMoon.

c. Explainfirstaidforinjuriesorillnessessuchasheatandcoldreactions,dehydration,bitesandstings,anddamagetoyoureyesthatcouldoccurduringobservation.

2.Explainwhatlightpollutionisandhowitandairpollutionaffectastronomy.

3.Withtheaidofdiagrams(orrealtelescopesifavailable),doeachofthefollowing:

a.Explainwhybinocularsandtelescopesareimportantastronomicaltools.Demonstrateorexplainhowthesetoolsareused.

b.Describethesimilaritiesanddifferencesofseveraltypesofastronomicaltelescopes.

c.Explainthepurposesofatleastthreeinstrumentsusedwithastronomicaltelescopes.

d. Describethepropercareandstorageoftelescopesandbinocularsbothathomeandinthefield.

4. Dothefollowing:

a.Identifyintheskyatleast10constellations,atleastfourofwhichareinthezodiac.

b.Identifyatleasteightconspicuousstars,fiveofwhichareofmagnitude1orbrighter.

c. MaketwosketchesoftheBigDipper.Inonesketch,showtheBigDipper’sorientationintheearlyevening

35859ISBN 978-0-8395-3303-0©2010 Boy Scouts of America2010 Printing

BANG/Brainerd, MN6-2010/056828

Astronomy 3

sky.Inanothersketch,showitspositionseveralhourslater.Inbothsketches,showtheNorthStarandthehorizon.Recordthedateandtimeeachsketchwasmade.

d.ExplainwhatweseewhenwelookattheMilkyWay.

5.Dothefollowing:

a.Listthenamesofthefivemostvisibleplanets.Explainwhichonescanappearinphasessimilartolunarphasesandwhichonescannot,andexplainwhy.

b.UsingtheInternet(withyourparent’spermission),books,andotherresources,findoutwheneachofthefivemostvisibleplanetsthatyouidentifiedinrequirement5awillbeobservableintheeveningskyduringthenext12months,thencompilethisinformationintheformofachartortable.

c. Describethemotionoftheplanetsacrossthesky.

d. Observeaplanetanddescribewhatyousaw.

6.Dothefollowing:

a.SketchthefaceoftheMoonandindicateatleastfiveseasandfivecraters.Labeltheselandmarks.

b.SketchthephaseandthedailypositionoftheMoon,atthesamehourandplace,forfourdaysinarow.Includelandmarksonthehorizonsuchashills,trees,andbuildings.Explainthechangesyouobserve.

c. ListthefactorsthatkeeptheMooninorbitaroundEarth.

d.Withtheaidofdiagrams,explaintherelativepositionsoftheSun,Earth,andtheMoonatthetimesoflunarandsolareclipses,andatthetimesofnew,first-quarter,full,andlast-quarterphasesoftheMoon.

7.Dothefollowing:

a.DescribethecompositionoftheSun,itsrelationshiptootherstars,andsomeeffectsofitsradiationonEarth’sweatherandcommunications.

b.Definesunspotsanddescribesomeoftheeffectstheymayhaveonsolarradiation.

c. Identifyatleastoneredstar,onebluestar,andoneyellowstar(otherthantheSun).Explainthemeaningofthesecolors.

4 Astronomy

8. Withyourcounselor’sapprovalandguidance,doONEofthefollowing:

a.Visitaplanetariumorastronomicalobservatory.Submitawrittenreport,ascrapbook,oravideopresentationafterwardtoyourcounselorthatincludesthefollowinginformation:

(1)Activitiesoccurringthere

(2)Exhibitsanddisplaysyousaw

(3) Telescopesandotherinstrumentsbeingused

(4)Celestialobjectsyouobserved

b.Planandparticipateinathree-hourobservationsessionthatincludesusingbinocularsoratelescope.Listthecelestialobjectsyouwanttoobserve,andfindeachonastarchartorinaguidebook.Prepareanobserv-inglogornotebook.Showyourplan,charts,andlogornotebooktoyourcounselorbeforemakingyourobservations.Reviewyourlogornotebookwithyourcounselorafterward.

c.PlanandhostastarpartyforyourScouttrooporothergroupsuchasyourclassatschool.Usebinocularsoratelescopetoshowandexplaincelestialobjectstothegroup.

d.Helpanastronomyclubinyourcommunityholdastarpartythatisopentothepublic.

e.PersonallytakeaseriesofphotographsordigitalimagesofthemovementoftheMoon,aplanet,anasteroid,meteor,oracomet.Inyourvisualdisplay,labeleachimageandincludethedateandtimeitwastaken.Showallpositionsonastarchartormap.Showyourdisplayatschooloratatroopmeeting.Explainthechangesyouobserved.

9.Findoutaboutthreecareeropportunitiesinastronomy.Pickoneandfindouttheeducation,training,andexperiencerequiredforthisprofession.Discussthiswithyourcounselor,andexplainwhythisprofessionmightinterestyou.

Astronomy 5

Contents

Introduction:ReachfortheStars. . . . . . . . . . . . . . . . . . . . . . 7

GettingReadytoObserve . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

StarsandConstellations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

ThePlanetsandOurSolarSystem. . . . . . . . . . . . . . . . . . . . 27

TheMoon—OurNearestNeighbor. . . . . . . . . . . . . . . . . . . . 39

TheSunandStars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

ToolsoftheTrade. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

LightPollution...................................67

YouandAstronomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

CareersinAstronomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

AstronomyResources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Astronomy 7

.Introduction: reach for the stars

Just as you enjoy

looking up at the

stars and finding

the Big Dipper,

ancient stargazers

had fun naming

the patterns of

stars they saw

every night. The

word astronomy

literally translates

to “naming

the heavens.”

Introduction:ReachfortheStarsSpectacularshowscanbeseeninthenightsky.FromEarth,wecanseenebulae,orgiantcloudsofgasanddustwherenewstarsareborn.Wecanseeoldstarsdyingandexploding.Wecanseemeteorshowers,orshootingstars.Sometimesitisraretoseesomeofthesesights.Butonanyclearnightoftheyear,youusuallycanseetheMoonandadazzlingarrayofstars.

Inlearningaboutastronomy,youwillstudyhowactivitiesinspaceaffectyourownplanet.Yourdailyschedule—daytimeandnighttime—isdictatedbyEarth’spositionasitrotatesonitsaxis.Earth’sorbitaroundtheSuntakesayearandgivesusthechangingseasons.TheSun’senergyaffectstheweather,andthegravitationalpullbetweenEarthandtheMooncreatesandcontrolsoceantides.

Westillhavemuchtolearnaboutspace.Onlyafewyearsago,in2001,astronomersdiscovered11newmoonsorbit-ingJupiter.ThroughinstrumentssuchastheHubbleSpaceTelescope,weseevisionstodaythatearlierobserverscouldnothaveimagined.

Weknowmuchaboutspaceanditseffectsonus,butthereisagreatdealwedon’tyetknow.Somedayyoumightbeamongthescientistsortheseriousamateurobserverswhomakeimportantnewdiscoveries.

An axis is the imaginary line around which a rotating body, such as Earth, turns. Earth’s axis is a straight line between the geographic (not magnetic) north and south poles. Earth’s orbit is the curved path it follows on its yearly trip around the Sun.

Revolution

Rotation

8 Astronomy

Getting ready to observe.

GettingReadytoObserve

Knowhowtoprotectyourselfbeforeyougooutinsearchofthenextgreatastronomicaldiscovery.

Protect your BodyWhenyougostargazing,dressappropriatelyfortheweather—hotorcold.Tohelpprotectyourselfagainstbitesandstingswhenyougooutside,wearclothesthatcoverallexposedskin,andbesuretobuttonandtuckthemin.Wearshoesorboots—notsandals—andsocks.Insectrepellentsprayedonyourbody,clothing,andshoesprovidesaddedprotection.

moving in the DarkDuringthedaybeforeastargazingouting,surveytheareawhereyouwillbeobserving.Lookfordrop-offs,holes,crevices,orotherobjectslikelargerocksortreerootsthatyoumightnotseeatnight.Takecaretoavoidthehazardswhenyoureturnatnighttoobserve.Bringred-filteredflashlightstoilluminatethearea.

Many insect repellents contain chemicals that may corrode plastic. Whenever you are applying insect repellent, do so where it won’t affect your equipment. Afterward, clean your hands before handling a telescope.

It takes about 30 minutes for the human eye to adjust to darkness. to help preserve your night vision, use a red filter with your flashlight. simply secure a piece of red cellophane over an ordinary flashlight.

Astronomy 9

.Getting ready to observe

Protect your EyesneverstaredirectlyatorneartheSun,evenforafewmoments.neverlookattheSunthroughbinocularsoratelescopeunlessyourequipmenthasthepropersolarfilters.LookingdirectlyattheSun—evenwhilewearingsunglasses—cancausepermanentblindnessorotherdamagetoyoureyesthatmightnotbeimme-diatelynoticeable.The safest way to observe the Sun is indirectly by projection,whichisexplainedinthechaptercalled“TheMoon—OurNearestNeighbor.”Projectionistherecommendedmethodforsafelyviewingthesun.Inanycase,alwaysdosoonlyunderthesupervisionofaknowledgeableadult.

observing objects near the sunMercury,theplanetnearesttheSun,alwaysliesclosetotheSuninthesky.LookforMercuryonlywhentheSun’sdiskisentirelybelowthehorizon.Don’triskgettingtheSunintheview.Thiscouldcausepermanenteyedamageorblindness.

Heat Exhaustion and HeatstrokeHeat exhaustionoccurswhenthebodyoverheatsbecauseitscoolingmethodsfail.Watchforthesesigns:bodytemperaturebetween98.6and102degrees;skinpale,clammy,andsweaty;nausea,dizziness,andfainting;pronouncedweaknessandtired-ness;headache;musclecramps.Totreatheatexhaustion,havethevictimliedowninacoolspotwiththefeetraised.Loosentheclothing.Applycool,dampclothstotheskinoruseafan.Havethevictimsipwater.

If you are in the

Sun and you or

a companion

experience eye

discomfort, cover

the eyes and

seek medical

attention

immediately.

The Moon at new-moon phase also lies in the direc-tion of the Sun. The new Moon is in the sky all day, but it is not visible in the Sun’s glare. Do not look at or near the Sun while trying to view a new moon. Wait a couple of days after the new moon, then look for a thin crescent moon in the evening sky just after sunset.

10 Astronomy

Getting ready to observe.

Heatstroke (sunstroke)islife-threat-eningbecausethebody’sheatcontrolsystemhasbeenoverworkedandoverwhelmed,resultinginitsfailure.Signsincludebodytemperatureabove102degrees;red,hot,anddryskin;extremelyrapidpulse;confusionordisorientation;faintingorunconscious-ness;convulsions.

Coolthevictimimmediately.Placethevictiminacoolspotface-upwithheadandshouldersraised.Removeouterclothing,spongethebareskinwithcoldwater,andsoakunderclothingwithcoolwater.Applycoldpacks,useafan,orplacethevictiminatubof

coldwater.Drytheskinafterthebodytemperaturedropsto101degrees.Obtainmedicalhelpimmediately.

sunburnSunexposurecancatchyoubysurprisewhenyouareoutside,preoccupiedwithsettingupyourequipmentorviewingasolareclipse.Wearloose-fittingclothingthatcompletelycoversthearmsandlegs,andabrimmedhat.Applysunscreenwithasunprotectionfactor(SPF)ofatleast15toexposedskin.Don’tforgetyourearsandthebackofyourneck.Reapplysun-screenoftenandasneeded.

Cold-related Problems—HypothermiaHypothermiaoccurswhenthebody’scoretemperaturedropssolowthatitisnolongerabletokeepwarm.Thekeytopreventinghypothermiaistokeepwarmandstaydry,and—ifyouwillbeoutsideforextendedperiods—eatplentyofenergyfoods(nuts,driedfruits,peanutbutter).Don’tpushyourselftoadangerouspointoffatigue.

Astronomy 11

.Getting ready to observe

Apersonintheearlystagesofhypothermiamaybeshivering.Asthevictimgetscolder,theshiveringwillstop.Othersymptomsmayincludeirritability,sleepiness,incoher-ence,disorientation,andtheinabilitytoreasonorthinkclearly.Immediatelypreventfurtherheatloss.Movethevictimtoashelter,removedampclothing,andwarmthepersonwithblanketsuntilbodytemperaturereturnstonormal.Covertheheadwithawarmhatorothercovering,andofferhotdrinks.

Iftheconditionprogresses,activelywarmthevictim’sbody.Placethevictimintoasleepingbagwithoneortwootherpeo-ple.Allshouldbestrippedofmostclothingsothatskin-to-skincontactcanhastenthewarming—andperhapssavealife.Severehypothermiarequiresimmediatemedicalattention.

DehydrationDehydrationiscausedbylackofwaterinthebody.Apersonwhogivesoffmorewaterthanconsumedcanbecomedehy-drated—inhotorcoldweather.Astronomicalobserversshouldstaywell-hydratedwhileintheoutdoors.Donotwaittodrinkuntilyoufeelthirsty.

In cold weather, wear layers to keep in the heat. Bring along a woolen cap, scarf, gloves, extra socks, and a coat. Keep your arms and legs covered. Always carry rain gear.

Circumpolar star chart

Astronomy 13

.stars and Constellations

A star is a hot,

glowing ball of

gas that produces

energy by nuclear

reactions in its

core. In fact, our

sun is a star.

A constellation

is a pattern of

stars in the sky.

StarsandConstellationsPeoplehavealwaysenjoyedstudyingthestars.Tohelpthemkeeptrackofthestars,ancientGreekscreativelydrewimaginarylinesbetweenstarstoformimagesofmythologicalcharactersorotherfamiliarcreatures.Thesestargroupsareknownasconstellations.Today,astronomersrecognize88constellations.

year-round ConstellationsSomeconstellationsarevisibleanytimeoftheyear.Theseconstellationsareknownascircumpolarbecausetheyneversetbelowthehorizon.AsEarthrotatesonitsaxis,thestarsseemtocircleapointcalledthecelestialnorthpole.ThenorthpoleitselfpointstoPolaris,ortheNorthStar.FindingPolariswillbeabighelpinlocatingthefourmaincircumpolarconstellations.

Ursa major.TheBigDipperispartofUrsaMajor(theGreatBear),aconstellationthatincludesafewless-visiblestars.TheouterstarsonthebowloftheBigDipperalwayspointtoPolaris.Everysixhours,theBigDipperappearstohavemovedaquarterofthewayaroundPolaris.

Ursa minor.TheLittleDipper,withstarsfainterthantheBigDipper,ispartoftheconstellationUrsaMinor,ortheLittleBear.PolarisistheendoftheLittleDipper’shandle.

Cassiopeia.IfyoufollowthelinefromthemiddlestaroftheBigDipper’shandlethroughPolaris,youwillfindCassiopeia.ItsfivemainstarsformanMwhenthey’reabovetheNorthStarandaWwhentheyarebelowit.

Draco.Draco,thedragon,windsaroundPolarisbetweentheBigandLittleDippers.Noneofitsmorethan80visiblestarsisverybright;thefourstarsthatformthedragon’sheadareeasiesttosee.

14 Astronomy

stars and Constellations.

seasonal ConstellationsSomeconstellationsarevisibleinthenightskyonlyatcertaintimesoftheyear.Twelveseasonalconstellationsknownaszodiacalconstellationsarecenteredontheecliptic,thepaththattheSun,theMoon,andtheplanetsallappeartofollowthroughthesky.Thezodiacalconstellationsyoucanseeatnight—Aries,Taurus,Gemini,Cancer,Leo,Virgo,Libra,Scorpius,Sagittarius,Capricornus,Aquarius,andPisces—changeasEarthfollowsitsyearlypatharoundtheSun.

spring ConstellationsLeo.YoucanseeLeo,theLion,fromJanuarythroughJune.FromthetwostarsoftheBigDipper’sbowlthatarenotusedtopointtowardPolaris,followwithyoureyealinestraightdowntoLeo’sbrighteststar,Regulus.

Virgo.Virgo,theVirgin,isthelargestconstellationandisvisiblefromAprilthroughJuly.IfyoulookfromthehandleoftheBigDipperthroughArcturus(abrightstarintheconstellationBoötes),youwillseeanotherbrightstar.ThisisSpica,thebottomofVirgo’sYshape.

Libra.Libra,theBalanceScale,isalate-springconstellationwithfourfairlydimstars.Itisoneofthemostdifficultzodiacalstarpatternstospot.LookbetweenSpicaandthesoutheasternhorizon.

Cancer.Cancer,theCrab,isvisiblefromJanuarytoMay,butitisthefaintestconstellationinthezodiac.Tofindit,followalinefromLeo’sRegulustotheGeminiconstellation(awinterconstellationdescribedbelow).CancerisbetweenLeoandGemini.

Some people believe the zodiacal constellations affect human behavior. This belief is known as astrology.

spring star chart

16 Astronomy


summer ConstellationsLyra.YoucanseeLyra,theLyre,fromMaythroughNovember.Inlatesummeratabout10p.m.,ifyoulookstraightup,youmayseeaverybrightblue-whitestar.Thisstar,Vega,isLyra’sbrighteststar.

Cygnus.OftencalledtheNorthernCross,CygnustheSwanisvisiblefromJunethroughNovember.FollowalinefromVegaslightlyeasttoanotherstar,Deneb,thatisalmostasbright.DenebisCygnus’sbrighteststar.

Aquila.ThesomewhattriangulargroupinginthesummerskysouthofLyraandCygnusisAquila,theEagle.ItsbrighteststarisAltair,whichformstheSummerTrianglewithDenebandVega.

scorpius.InJulyandAugust,youcanseeScorpius,theScorpion,veryclosetothesouthernhorizon.ItsbrighteststarisAntares,aredsupergiantstarnearthescorpion’shead.

sagittarius.InJulyandAugustyoucanseeSagittarius,theArcher,justeastofScorpius.Itsmainstarsformapatternthatresemblesateapot.WhenyoulookatSagittarius,you’relook-ingtowardthecenteroftheMilkyWaygalaxy.ScorpiusandSagittariusmaybedifficulttoviewifyouliveintheNorth.

A galaxy is an

enormous group

of millions or

billions of stars,

bound together

by gravity. Earth

is in the Milky

Way galaxy.

Part of Aquila lies along the path of the Milky Way where there are dense star fields.

Of the conspicuous (easy-to-see) stars, only Sirius and Arcturus are brighter than Vega.

summer star chart

18 Astronomy


Autumn ConstellationsPegasus.Pegasus,theFlyingHorse,isbestseenfromAugustthroughOctober,southeastofCygnus.PartoftheconstellationisknownastheGreatSquare,aneasyshapetorecognize.

Andromeda.PegasussharesoneofitsstarswithAndromeda,whichisvisiblefromSeptembertoJanuary.LookeastwardfromtheGreatSquareofPegasus.TheAndromedagalaxy—themostdistantobjectvisibletothenakedeye—isvisibleonclearnightsasafaint,mistyspotintheAndromedaconstellation.

Perseus.YoucanseePerseusintheautumnandwinter,eastofAndromeda.ItliesbetweentheconstellationsofAuriga(describedbelow)andCassiopeia.PerseuscontainsthedoublestarAlgol.AsthestarsofAlgolpassinfrontofeachother,Algolappearsalternatelyfainterandbrighter.

Aries.ThreefairlybrightstarsmakeupthemainpartofAries,theRam.ItappearssouthofAndromedafromOctoberthroughMarch.

Pisces.ThemainpartofPisces,theFishes,isastringofstarsbelowAndromedaandPegasus.PiscesappearsintheskyfromOctobertoDecember,butitisfaintandcanbehardtofind.

Capricornus.LookstraightdownfromthestarAltairinAquila.Capricornus,theSeaGoat,isafaintconstellation,butwhenvisibilityisgoodyoucanseeitfromAugustthroughOctober.

Aquarius.Ondark,clearnightsfromAugustthroughOctober,youmaybeabletoseeAquarius,theWaterBearer,southofPegasus.OneendofAquariusstretchesaboveCapricornusandtheotherisbelowtheCircletofPisces.

To locate the

Circlet, an

interesting star

group in Pisces,

look just south of

the Great Square

of Pegasus.

A double star is a pair of stars that are close together and hold each other captive by the force of gravity. Each one orbits around the other. In most cases they are so close together, they look like single stars.

Autumn star chart

20 Astronomy


Winter Constellationsorion.Orion,theHunter,usuallyiseasytofindfromOctoberthroughApril.Itislargeanddistinctivewithtwoverybrightstars—thereddish-orangegiantBetelgeuseandbluish-whiteRigel—aswellasfiveotherbrightstarsandseverallessvisibleones.TheOrionNebula,acloudofdustandgasseverallight-yearsacross,isvisibletothenakedeyeasafuzzypatchjustbelowOrion’sbelt.

Canis major.SoutheastofOrionisCanisMajor,theGreatDog,whichyoucanseefromDecemberthroughApril.Sirius,thenightsky’sbrighteststar,isapartofCanisMajor.Orion’sthreebeltstarspointdownwardtowardSirius.

Gemini.FromDecemberthroughMayyoucanseeGemini,theTwins,northeastofOrion.Twobrightstars,CastorandPollux,aretheheadsoftheGeminitwins.

Auriga.VisiblefromNovemberthroughApril,Auriga,theCharioteer,isnorthofOrion.Capella,adoublestarinAuriga,isoneofthebrightestlightsinthesky.

taurus.Orion’sbeltstarspointuptowardAldebaran,abrightorange-redstar.AldebaranistheeyeofTaurustheBull,aconstellationyoucanseefromNovemberthroughMarch.

Betelgeuse,

Orion’s shoulder

star, is so huge

that if it were at

the center of our

solar system,

its edges would

extend beyond

the orbit of Mars.

Taurus has two star groups: one a cluster of stars known as the Pleiades, and the other a larger, more scattered, V-shaped group known as the Hyades.

Winter star chart

22 Astronomy


Star Light, Star BrightAnother word astronomers use to describe a star’s brightness is magnitude.

• Absolute magnitude refers to a star’s true brightness—that is, the brightness if all stars were viewed from the same distance.

• Apparent magnitude means the brightness of a star as we see it from Earth. Astronomers give a star a number to refer to this magnitude. The lower the magnitude number, the brighter the star. Stars that are brighter than a magnitude 1 have a zero or negative number. The unaided human eye can see stars with a magnitude number as high as 6.

Listed here are some of the brightest stars in the sky, the constellations where they are found, and their apparent magnitude.

star Constellation magnitude

Sirius Canis Major -1.46

Arcturus Boötes -0.04

Vega Lyra 0.03

Capella Auriga 0.08

Rigel Orion 0.12

Procyon Canis Minor 0.38

Betelgeuse Orion 0.5

Altair Aquila 0.77

Aldebaran Taurus 0.85

Antares Scorpius 0.96

Spica Virgo 0.98

Pollux Gemini 1.14

Deneb Cygnus 1.25

Astronomy 23


the milky WayWhenwelookattheMilkyWayinthenightsky,weseeourowngalaxy.Apartfromothergalaxies,everythingweseeinthenightsky—thestars,starclusters,nebulae,theSun,theMoon,andtheplanets—ispartoftheMilkyWay.Justasitsnameimplies,itappearsasawhitishbandoflight.Forobserv-ersinthenorthernhemisphere,itisbrightestinthesummermonthsintheconstellationsAquilaandCygnus.

TheMilkyWayisourhomegalaxy,agiganticdiskofhundredsofbillionsofstarsandvastquantitiesofdustandgas.Itisabout100,000light-yearsacrossandsome10,000light-yearsthickatitscenter.Stars,dust,andgasesfanoutfromthehubofthishugewhirlingdiskinlong,curvingarmsthatmakeaspiralorpinwheelshape.Oursolarsystemisabouthalfwayoutfromthecenterononeofthearms.

If you live outside a major city, you probably have seen the milky Way, which can be viewed without the aid of a telescope or binoculars.

Every one of the

billions of galaxies

in the universe

has millions or

billions of stars.

The Milky Way

appears to

be an average

spiral galaxy.

24 Astronomy


Youcanseeanothergalaxywiththeunaidedeyeonaclearnightinthefall—theAndromedaGalaxy.Italsoisthemostdistantobjectyoucanseewiththenakedeye.ItappearsasamistypatchoflightintheconstellationofAndromeda.AstronomerscalltheAndromedaGalaxy“M31”andplaceitatabout2.4millionlight-yearsfromEarth.M31appearstobehalfagainasbigasourgalaxy—150,000light-yearsacross.

The Andromeda

Galaxy is more

than 2 million

light-years away.

A light-year is

the distance light

travels in one

year, equal to

approximately

5.9 trillion miles.

Some galaxies can be seen through backyard telescopes at distances of 100 million light-years or more—distances almost unimaginable.

Astronomy 25


Using a PlanisphereA planisphere is a flat, circular map of the stars with an overlay that you can set to show what stars and constellations are visible at any time of the night and any night of the year. It can be adjusted to match the exact month, day, and hour when you are looking at the sky.

Astronomy 27

.the Planets and our solar system

ThePlanetsandOurSolarSystemTheplanetsofoursolarsystemtravelaroundtheSun,eachinitsownorbit.ThefourplanetsclosesttotheSun—Mercury,Venus,Earth,andMars—arecalledtheterrestrial(earthlike)planetsbecausetheyhavesolid,rockysurfaces.ThefourlargeplanetsbeyondtheorbitofMars—Jupiter,Saturn,Uranus,andNeptune—arethegasgiants,mademostlyofhydrogenandheli-um,probablywithnosolidsurfaces.

mercuryisthesmall,rockyplanetnearesttheSun.ItcompletesatriparoundtheSunevery88Earth-days,speedinginitsorbitfasterthananyotherplanetinthesolarsystem.IfyoucouldstandonMercury,youwouldseeabloatedsuncreepatasnail’spacethroughablacksky.Mercuryrotatesextremelyslowlyonitsaxis—onceinabout59Earth-days.BecauseMercuryissoclosetotheSun,temperaturesontheplanet’ssurfacecanreachasearing800degrees.Mercury’scrateredsurfacelooksmuchlikethesurfaceofEarth’smoon.

Venus,secondplanetfromtheSun,isonlyslightlysmallerthanEarth.ThethickcloudsofcarbondioxideandsulfuricacidthatcoverVenusreflectsunlight,makingitbrightbutalsotrappingheatattheplanet’ssurface.At842degrees,it’shotteronVenusthanonMercury,eventhoughMercuryisnearertheSun.Thethick,heavyatmospherecreatesenormouspressureonVenus.Spaceprobesthathavelandedtherehavelastedonlyafewhoursbeforethepressurecrushedthem.VenusspinsintheoppositedirectionofitsorbitaroundtheSun.

Venus is a scorched world with temperatures hot enough to melt lead.

mercury

28 Astronomy

the Planets and our solar system.

LifeonEarthsurvivesbeneathathinlayerofatmospherethatsheltersusfromthedangersofspace.“Ocean”mightbeamoreappropriatenameforthisplanet,becauseoceanscovernearly70percentofEarth’ssurface.

mars,theredplanet,isthefourthterrestrialplanet.AdayonMarslasts24hours,37minutes—onlyslightlylon-gerthananEarth-day.ButMarstakesalmosttwiceaslongasEarthtoorbittheSun,goingaroundoncein687Earth-days.

ThoughMarsisaworldwithnorivers,ithaswindingvalleysthatlooklikedryriverbeds.ScientistsbelievethatpowerfulfloodsoncedelugedMars.Todaytheplanetistoocoldanditsatmospheretoothinforliquidwatertoexistatthesurface.In2002,theMarsOdysseyspacecraftdetectedlargeamountsoficenearthesurface—enoughtofillLakeMichigantwiceover.Morewaterisfrozeninthepolaricecaps.

Jupiter,morethan300millionmilesfromMars,isthelargestplanetinthesolarsystem.IfJupiterwereahollowball,morethanathousandEarthswouldfitinside.Despiteitssize,Jupiterspinsfasterthananyotherplanet,rotatingevery10hours.However,ittakesJupiternearly12Earth-yearstoorbittheSun.Liketheothergasgiants,Jupiterismostlyhydrogenandhelium.Thetemperatureatthetopofitscolorfulcloudsisminus220degrees.Downintheclouds,thetemperaturereaches70degreesatadepthwheretheatmosphericpressureisabout10timesasgreatasitisonEarth.

Earth

mars

Jupiter

Astronomy 29


saturn,thesecondlargestplanet,isthefarthestfromEarthofthefiveplanetsknowntoearlystargazers.Galileo,in1610,wasthefirstastronomertoseeSaturnanditsringsthroughatelescope.Upto1977,astronomersthoughtSaturnwastheonlyplanetwithrings.Wenowknowtheothergasgiants—Jupiter,Uranus,andNeptune—alsohaveringsystems,butSaturn’sisbyfarthelargest,mostvisible,andmostcom-plex.Itsringsaremademostlyofice.Saturnalsohasatleast30moons.Thelargest,Titan,isalittlebiggerthanMercuryandisblanketedwithathick,nitrogen-richatmosphere.

Uranus(pronouncedYOOR-un-nus),alargegasplanet,blue-greenincolor,wasdiscoveredin1781byastronomer

WilliamHerschel;itsringswerenotdiscovereduntil1977.UranusistwiceasfarfromtheSunasSaturn—sofarawaythatittakessunlightabout2hours,40minutestoreachit.UranusorbitstheSuntippedonitsside,theresultofwhatmanyastronomersthinkwasacollisionwithaplanet-sizedbodylongago.

Saturn with its

rings would just

fit in the distance

between Earth

and the Moon.

Three Earths could fit across Jupiter’s Great Red Spot, a storm like a hurricane that has raged for centuries in Jupiter’s southern hemisphere.

Uranus

saturn

30 Astronomy


neptune,theeighthplanetfromtheSun,issofarawaythatittakes165yearstoorbittheSun.LikeEarth,Neptunehassea-sons,buteachseasonlastsfor41Earth-years.Neptuneistoodistanttobeseenwiththeunaidedeye.In1989,theVoyager2spacecrafttrackedalargedarkstormlikeahurricane

inNeptune’ssouthernhemisphereanddiscoveredgreatgey-sersofnitrogenonTriton,Neptune’slargestmoon.Tritonisthecoldestbodyyetvisitedinoursolarsystem,withsurfacetemperaturesreachingminus390degrees.

How the Planets moveFromourhomeplanet,theSunappearstocircleEarth,risingintheeastandsettinginthewest.ButEarthreallyisthebodythatismoving.Tounderstandthemovementsofthenightsky,keepinmindEarth’stwomainmotions:ItcirclestheSun,goingaroundoncein365days(ayear),anditspinsonitsaxis,makingonecompleterotationin24hours(aday).

Fromnighttonight,eachplanetshiftsitspositionslightlyeastwardinrelationtothestars,traveling“through”variousconstellationsoverthecourseofseveralweeksasitcirclestheSun.Mercury,Venus,andMarsshowthismotionmostclearly.DistantJupiterandSaturntravelsoslowly,it’shardertoseetheireastwardshiftagainstthestars.

Since its discovery

in 1846, Neptune

has yet to make

one full circle

around the Sun.

Earth’s counterclockwise spin—from west to east—makes the sky overhead seem to rotate in the opposite direction, from east to west. The Sun, the stars, the Moon, and the planets also appear to travel a simple westward path across the sky, but their patterns actually are more complicated.

neptune

Astronomy 31


Sometimes,aplanetexhibitsretrograde motion—itappearstostopitseastwarddriftandloopbacktowardthewestbeforeresumingitsnormalwest-to-eastmovement.Forexample,becauseEarthtakeslesstimetoorbittheSunthanouterplanetslikeMars,Jupiter,andSaturn,itoccasionallyovertakesanouterplanet,likeafastcarpassingasloweroneonthehighway.AsEarthapproaches,theotherplanetappearstostopitseastwarddriftandloopbacktowardthewest.AsEarthswingspasttheplanet,weseetheplanetresumeitsnormalwest-to-eastdriftinthenightsky.

As Earth overtakes a planet that is farther from the sun, the planet’s movement appears to change direction. this retrograde motion is most apparent in the movement of mars from 1994 to 1995.

JanuaRy 2, 1995

July 4, 1995

SeptembeR 24, 1994

maRch 24, 1995

leo

canceR

The retrograde motion of the planets puzzled early astronomers, who named these bodies “planets,” which in Greek means “wanderers,” because of the complicated ways the planets move.

32 Astronomy


Never look at

the Sun to locate

Mercury, as

blindness could

result. Make sure

the Sun’s disk

is completely

below the horizon

before looking in

its direction.

observing the PlanetsFiveplanetsarevisiblefromEarthwiththeunaidedeye:Mercury,Venus,Mars,Jupiter,andSaturn.Uranusmaybedimlyviewedonveryclearnights,butonlywithpowerfultelescopescanweviewNeptuneevenfaintly.

the Inferior PlanetsMercuryandVenusorbittheSuninsideEarth’sorbit,sotheyareknownasinferiorplanets.WhentheseplanetsarebetweenEarthandtheSun,theSun’sbrightnessmaketheminvisible.BehindtheSun,theyareoutofsight.Thebesttimetoseetheseplanets,therefore,iswhentheyareoneithersideoftheSun.

BecauseMercuryissoclosetotheSun,itisneverseeninafullydark,nighttimesky.Itisvisibleonlyinbrighttwilight,eitherverylowinthewesternskyjustaftersunsetorverylowintheeastjustbeforesunrise.

LatewinterandearlyspringareusuallythebesttimesforobserversinthenorthernhemispheretospottinyMercuryintheeveningsky,abouthalfanhouraftersunset.Tofinditintheearlymorningsky,abouthalfanhourbeforesunrise,lookinthedirectionofsunriseduringthelatesummerandfall.

mercury’s phases

evening viSibility

to eaRth

moRning viSibility

Astronomy 33


Venusalsoappearsonlyintheearlyeveningorearlymorningsky,butitismucheasiertoseethanMercury.Sometimescalledthemorningortheeveningstar,diamond-whiteandbrilliantVenusisoursolarsystem’sbrightestplanet.IfVenusisintheeveningsky,youcan’tmissit.

BecausedifferentpartsoftheirsunlitareasarevisiblefromEarthatdifferenttimes,MercuryandVenushavephasessimilartotheMoon’s.Atdifferenttimes,theyappearfull,gib-bous(three-quartersfull),half-full(likeafirst-quarterorlast-quartermoon),asacrescent,oranywhereinbetween.

WhenMercuryorVenusisonthesamesideoftheSunasEarth,theplanet’sunlitsidefacesEarth.AstheplanetmovesaroundtheSunawayfromEarth,itssunlitsidebecomesvis-ibleasathincrescentandgrowsgraduallyastheplanetmovesalong.WhenMercuryorVenusisneartheothersideoftheSun,wecanseealmostallofitssunlitface—thefullphase.

the superior PlanetsTheplanetsbeyondEarth’sorbitareknownasthesuperiorplanets.Unliketheinferiorplanets,whicharealwaysclosetotheSuninoursky,thesuperiorplanetscanappearanywhereintheskyontheecliptic,andtheyalwaysappearfull.Mars,Jupiter,andSaturncanbeseenhighinthenightsky,longafterthesunhasset.

Thebesttimetoviewasuperiorplanetiswhenitisinopposition—whenEarthisdirectlybetweenitandtheSun.Whenaplanetisinopposition,itrisesatsunsetandsetswhentheSunrises.

A conjunction occurs when two or more planets appear near each other in the sky. Major conjunc-tions—when several planets align—are rare celestial events that may occur decades apart. In May 2000, five planets lined up across the solar system. The next grand conjunction will not occur until September 8, 2040.

34 Astronomy


the zodiac is centered on the ecliptic, the path the sun appears to follow among the stars.

gemini

tauRuS

piSceS

aRieS

tauRuS

ecliptic

capRicoRnuS

aquaRiuSScoRpiouS

libRa

ecliptic

viRgo

leo

canceR

SagittaRiuS

South celeStial pole

gemini

eaRth

noRth celeStial pole

ScoRpiuS

SagittaRiuS

Astronomy 35


tracking Visible PlanetsAlltheplanetstravelwithinthenarrowbandofthezodiac,althoughtheywanderaroundabit,sotheycanbeeasytomiss.Evenifyouhaveaprettygoodideaaboutthelocationofthezodiac,youmaystillhavetroublefindingtheplanets.Forhelp,lookataskymap,whichyoucandownloadfromtheInternet(withyourparent’spermission)orfindatthelocallibrary.Hereareafewtipsonrecognizingtheplanets.

mercury.Thissmallplanetishardtospot,butitisvisiblewithoutatelescope,eitherjustaftersunsetorjustbeforedawn,alwaysinthegeneraldirectionoftheSunandneverfarfromit.

Venus.AftertheSunandMoon,Venusisthebrightestobjectinthesky.Itcansometimesbeseenindaylight,butitisnevermorethanthreehoursaheadoforbehindtheSun.

mars.MarsiscalledtheRedPlanetwithgoodreason,butitsbrightnessvaries.Checkitspositioninanastronomicalalmanacorguidebook.

Jupiter.Amongtheplanets,JupiterissecondonlytoVenusforbrightness.Itsprogressacrosstheskycanseemsoslowthatyoumightmistakeitforastarunlessyoutrackitsmovementforseveralnights.

saturn.YouwillnotseeSaturn’sfamousringswiththeunaidedeye,buttheplanetisbrightenoughtofind.LikeJupiter,Saturntakesalongtimetoshowmovement,soconsultanalmanacorguidebookbeforescanningtheheavensforit.

Uranus.Thisdistantplanetisbarelyvisibletothenakedeyeunderevengoodviewingconditions.Itmovesveryslowly,sototheunaidedeyeitlookslikeanaveragestar.Throughatelescopeitappearspalegreen.

Planets do not twinkle like stars because they have a measurable disk, and more light reaches Earth. So, the steadiness of the light is a good indication that you are looking at a planet.

36 Astronomy


Asteroids, Comets, and meteoroidsOthermembersoftheSun’sfamilyincludeasteroids,comets,andmeteoroids—sometimesconsidered“cosmicdebris.”

AsteroidsAsteroidsareminorplanetsoftheSun.Estimatesoftheirnumberrangeintothemillions.Someareonlyafewfeetindiameter.Thelargest,Ceres,isabout580milesacross.

MostasteroidsorbitthesuninthehugeexpanseofspacebetweenMarsandJupiterknownastheasteroidbeltormainbelt.Sometimesasteroidsgetknockedoutofthemainbeltintotheinnersolarsystem.AsteroidfragmentsstrikeEartheveryday,andscientistsbelieveseverallargeasteroidshaveslammedintoEarthovertheyears.

CometsCometsareoftendescribedasdirtysnowballsbecausetheyaremadeoffrozengasesembeddedwithrockanddustparticles.Mostcometstravelinlong,ovalorbitsaroundtheSun.

WhenacometnearstheSun,theintenseheatcausesthegasesandparticlesthatwerefrozentogetherto“melt”andvaporize.Thevaporformsa“tail”thatmaybemillionsofmileslong.

Ida the asteroid

Comets that are bright enough to be seen without a telescope are so rare that only two or three comets may be visible from Earth every 10 or 15 years.

Some scientists

believe that a

huge asteroid

many years ago

struck near

Mexico’s Yucatan

Peninsula, setting

off a chain of

events that

doomed Earth’s

dinosaurs to

extinction.

Astronomy 37


meteoroids, meteors, and meteoritesThesethreearedifferentaspectsofthesamemembersofthesolarsystem.Theystartasmeteoroids—stonyormetallicmaterialsinspace.Somearemicroscopic,othersarehuge.

Everyday,Earth’satmospherecollideswithmillionsofmeteoroidsthatburninthetremendousheatcreatedbythecollision.Ifameteoroidislargeenough,thecollisionisvisibleasastreakoflightacrossthesky—ameteor,orshootingstar.

SomemeteoroidssurvivetheflamingfalltoEarthwithoutburningupcompletely.Thosethatmakeittothegroundaremeteorites.Mostmeteoritesaresmall,butthelargestmeteoriteeverdiscoveredweighsabout66tons.ItfellonafarminSouthAfrica.

Meteor ShowersSome meteoroids are believed to be clusters of comet frag-ments that continue to orbit along the comet’s old path, creating show-ers of meteors that blaze through the night sky as they pass through Earth’s atmosphere. Some noteworthy meteor showers are listed here. They are named for the constel-lations from which they appear to come.

the Willamette meteorite was found in 1902 in oregon’s Willamette Valley. It weighs 15.5 tons and measures 9.8 feet long and is the largest meteorite ever found in the United states.

shower Date of maximum

Quadrantid January 3

Lyrid April 21

Eta Aquarid May 4

Delta Aquarid July 29

Perseid August 12

Orionid October 22

South Taurid November 4–6

Leonid November 11–13

Geminid December 12

Astronomy 39

.the moon—our nearest neighbor

TheMoon—OurNearestNeighborTheMoonwashumankind’sfirsttargetinexplorationbeyondEarth.PeoplefirststudiedtheMoonwithjusttheireyes,thenwithEarth-basedtelescopes,thenwithrobotsinspace.In1968,explorersflewtotheMoonandstudieditfromorbit.Thefollowingyear,U.S.astronautslandedontheMoonandbroughtbackrockandsoilsamples.

Severaltimesbetween1969and1972,U.S.astronautsexploredthelunarsurfaceandleftbehindscientificinstrumentstohelpscientistslearnmoreaboutEarth’snaturalsatellite.AfewroboticprobeshavestudiedtheMooninthedecadessince,buttheMoonremainsafascinatingplacewithmanyunansweredquestions.

the Face of the moonTheMoon’ssurfaceishighlyuneven,coveredwithmountains,plains,andvalleys,andpittedwithcraters.TheMoonisbarren,withoutvegetation.Ithasnoatmosphereandthereareonlytracesofwater.Therearenoclouds,nofog,andnosnowtoblockourviewofitssurface.

Theseconditionsalsocauseextremesurfacetemperatures.Duringatypicallunarday,whichlaststwoweeks,theMoon’ssurfacebecomesmuchhotterthanwater’sboilingpointonEarth.Duringlunarnights,whichalsolasttwoweeks,thesurfacetemperatureplummetstomorethan300degreesbelowfreezing.

The soil samples

astronauts

brought back from

the Moon lack

many essential

minerals, but

they are not

poisonous

to plants.

Researchers

mixed a tray of

lunar soil with

dirt and grew

plants in it.

Even though one side of the Moon always faces away from Earth, both the near side and the far side of the Moon receive the same amounts of sunlight. There really is no “dark side of the Moon.”

40 Astronomy

the moon—our nearest neighbor.

mountains, seas, and CratersGooutatnightandtakeagoodlookattheMoon.Youwillseelighterareasanddarkerareas.Thedarkerareaswerecalledmaria(MAHR-ee-ah),orseas,becausetheastronomerswhopointedthefirstcrudetelescopesattheMooninthe17thcenturythoughtthesewerelargebodiesofwater.Thelighterareaswerecalledterrae(TEH-ray),orlands.LookattheMoonthroughbinocularsandyoucaneasilyseehowearlyastronomersmighthavereachedthatconclusion.

Wenowknowthatthebrightlunarlandsarerough,mountainoushighlands.Thedarkseasactuallyarebroad,levelplainsandlowlands.

Millionsofbowl-shapedcavitiesorpits,calledcraters,pockmarktheMoon’ssurface.Somecratersspanmorethan100mileswide.Somearethousandsoffeetdeep.TheMoon’sbroadestcratersoftenarecalledwalled plainsbecausetheirsidesaremuchlikesteepcliffsrisinguptomountainheight.

cold Sea

Sea of RainS

ocean of StoRmS*Sea of vapoRS

Sea of cloudS

Sea of moiStuRe

Sea of SeRenitySea of cRiSeS

Sea of tRanquility

Sea of feRtility

Sea of nectaR

*This big plain is called an “ocean” because of its size—1,550 miles across.

seas on the moon

Most lunar craters carry the names of astronomers, explorers, or ancient scientists and mathematicians, but several craters were named for mythological figures.

Astronomy 41


YoursketchoftheMoonforrequirement7adoesnothavetoshowafullmoon,butyoushouldselectaphasethatshowsatleastfiveseasandfivecraters.Drawthecontoursofvisiblefeaturesandlabelseasandprominentcraters.Ifyouhavetroubleidentifyingcraters,mostpubliclibrarieshaveastronomybookswithlunarmaps.

the moon’s PhasesAstheMoonorbitsEarth,itappearstotravelwestward,sinceweseetheMoonriseintheeastandsetinthewest.WatchtheMoon’spositionagainststarpatterns.Asthehourspass,theMoonmoveseastwardrelativetothestars,eventhoughitseemstobemovingwestwardthroughthenightsky.

TheMoontakesanaverageof27¼daystomakeonetriparoundEarth.Butthisisnottheactualtimefromnewmoontonewmoon.Earthalsoismoving,travelinginitsorbitaroundtheSun.IttakestheMoonabout2¼moredaystoreturntoapositiondirectlybetweenEarthandtheSun,sotheaveragetimefortheMoontomakeonecompletecircuitfromnewmoontonewmoonisabout29½days.

TheMoon’sappearancevariesgreatlyduringitscycleofphases.Justafternewmoonweseeaslendercrescent.Atthefirst-quarterphaseweseetheMoonhalf-illuminated.Duringthefollowingweek,agibbous(morethanhalf-illuminated)moongrowslargerstill.Atfullmoon,theMoonisoppositetheSunintheskysoweseeacompletelyilluminateddisk.

aRiStaRchuS

plato

aRchimedeS

hippaRchuSptolemaeuSalbategniuSalphonSuS

copeRnicuSKepleR

gRimaldi

tychoclaviuS

Craters and mountains on the moon

42 Astronomy


Afterthefullmoon,itbecomesagibbousmoon,thenshrinkstohalf-illuminatedasathird-quarterorlast-quartermoon,thenbecomesacrescentmoonagain.Finallyitreturnstothenew-moonphase,whereitisinvisibleintheSun’sglare.

TheMoon’spositionintheskyisslightlydifferenteachnight,anditriseslatereachnight,too.Witheachday,theMoonrisesanaverageofabout50minuteslater,anditdropsabout13degreesfartherbehindinrelationtotheSun.

A moon growing

to full is said to

be waxing. As it

shrinks from full to

new, it is waning.

Even as it moves through its phases, the moon is always a big rocky ball, roughly 2,200 miles across. Its appearance changes because half of the lunar surface always faces the sun, but that lighted portion does not always face Earth.

new moon

waxing cReScent

fiRSt quaRteR

waxing gibbouS

full moon

waning gibbouS

laSt quaRteR

waning cReScent

Astronomy 43


OneoftheeasiestwaystosketchthephasesanddailypositionsoftheMoonistostartyourobservationswhentheMoonissomewhereinthesouthwesternsky.Onyourfirstnightofobserving,drawacoupleoftheconstellationsthatarevisible.Next,drawintheMoonandwritethedatebesideitonyoursketch.Atthesamehouronothernights,addtheMoon’snewposition.

the moon’s orbitTheMoonorbitsEarthinanellipse,orslightlyflattenedcircle,atanaveragespeedof2,300milesperhour.ItsaveragedistancefromEarthis238,857miles.TwoforcesworktokeeptheMoonorbitingEarth.Thefirstforceiscalledinertia,thetendencyofanobjectinmotiontocontinueinmotioninastraightline.

IftheMoontraveledinastraightline,itwouldleaveorbitandshootoffintospace.TheforcethatholdstheMooninitsorbitisgravity,thesameforcethatpullsaballtothegroundwhenyoudropit.GravitykeepstheMoon“falling”aroundEarth.

JustasEarth’sgravitytugsontheMoon,theMoon’slessergravitypullsonEarth.ThatpullcausesEarthtowaverslightlyasitrevolvesaroundtheSun.LunargravityalsostronglyaffectsEarth’soceantides.

The Moon

travels faster

at its perigee,

when it is closest

to Earth—221,000

miles away.

It travels slower

at its apogee,

when it is farthest

from Earth—

about 253,000

miles away.

Remember that Earth’s surface is curved. If you could throw a ball fast enough so that it would land thousands of miles away, Earth would curve away from the speeding ball just as fast as the ball was dropping. When that happened, the ball would keep on falling and never strike the ground—it would be orbiting our planet.

moon

eaRth

the moon’s orbit

44 Astronomy


the moon’s role in EclipsesAneclipsehappenswhentheMoonmovesdirectlyintolinewithEarthandtheSun.Eclipsescanoccuronlyatnewmoonorfullmoon,andthenonlywhentheMooniscrossingEarth’sorbitalplane.Eclipsesusuallyoccurseveraltimesayear.

Therearetwotypesofeclipses:solarandlunar.Asolareclipsecanbeadramaticevent.Ithappenswhen

theMoonpassesdirectlybetweenEarthandtheSun,sothattheMoon’sshadowstrikesEarth.Duringatotalsolareclipse,

theSuniscompletelyblottedfromviewforeveryoneinthepathoftheMoon’sshadow.Apartialsolareclipseisvisibleofftoonesideofthepathoftotaleclipse.TheMoonappearstotakeabiteoutoftheSuninsteadoffullyblockingit.

WhentheMoonisatafarpointinitsorbit,anannulareclipsemayoccur.Inthiscase,theMoonappearssmallerbecauseitisfartheraway,anditblocksonlythecenteroftheSun’sdisk,allowingsunlighttoblazeallarounditsedges.

AlunareclipsehappenswhentheMoonmovesdirectlybehindEarth,passingintoEarth’sshadow.Thereareseveraltypesoflunareclipses:

• Partial lunar eclipse—TheMoondoesnottravelcompletelyintoEarth’sshadow.

• Penumbral eclipse—TheMooniscompletelywithinthebrighter,outerportion(penumbra)ofEarth’sshadow.

The orbital plane

is the imaginary

flat surface (the

plane) that Earth

marks out in

space as it orbits

the Sun. With few

exceptions, all the

other planets orbit

in or near this

same plane.

total eclipSe

moonSun umbRa penumbRa

paRtial eclipSe annulaR eclipSe

solar eclipse

Astronomy 45


Viewing a Solar EclipseSeeing a solar eclipse can be an unforgettable experience—but don’t let that be the last thing you ever see. never stare directly at the Sun, even for a few moments. Doing so can cause permanent blindness. Projection is the safest way to observe solar activity. However, when using the projection method, you should never look through the eyepiece.

one way to safely view the sun’s image is by projecting it through the objective lens (the large end) of a telescope or binoculars and holding a piece of paper under the eyepiece like a screen. An image of the sun will display on the paper. Never look into the eyepiece.

If you don’t have a telescope or binoculars, use the pinhole projection method. you will need two pieces of flimsy cardboard. Using a straight pin, make a small hole in the center of one piece. Hold this first piece of cardboard above the second one, lining the cards up with the sun as shown. the light will project an image of the sun’s eclipse through the hole in the first card onto the second card.

ScReen

StaR diagonal and eyepiece

caRdboaRd Shade

• Umbral eclipse—TheMoonpassesintothedarkestinnerportion(umbra)oftheshadow.

• total lunar eclipse—TheMoonmovescompletelywithintheumbra.Itistherarestoflunareclipses.

Youdon’tneedanyspecialequip-menttoviewalunareclipse.Lunareclipsesoftengounnoticed,eventhoughtheyarevisibleoveragreatarea.Mostpeoplefailtonoticeaslightshadow,dimming,ordiscolorationofthefullmoon.

Sun eaRth moon

penumbRaumbRa

Lunar eclipse

Astronomy 47

.the sun and stars

The Sun produces

enough energy

every second to

meet the needs of

the whole world

for more than

1,000 years.

TheSunandStarsTheSunisahugeballofhotgasabout93millionmilesfromEarth.Itcontains99.86percentofthemassoftheentiresolarsystem.IfyouimaginetheEarthasthesizeofagrape,thentheSunisabout5feethigh—thesizeofasmallrefrigerator.

TheSunismademainlyofhydrogenandhelium.EnergyisreleasedattheSun’scoreashydrogenchangesintoheliumduringnuclearfusionreactions.Everysecond,theSunconverts564milliontonsofhydrogeninto560milliontonsofhelium.FourmilliontonsofmatterarereleasedasenergytheSunradiatesintothesolarsystem.

48 Astronomy

the sun and stars.

The Sun From the Inside Out

the core is the center of the sun, where nuclear reactions take place. the temperature at the core is close to 29 million degrees. the core occupies 2 percent of the sun’s volume but has 60 percent of its mass.

the radiative zone is the section where energy leaves the core.

Above the photosphere lies the hot gas of the chromosphere (“sphere of color”), which is in violent motion. the chromosphere may be seen briefly during total solar eclipses as a reddish rim around the sun.

Above the chromosphere is the corona (“crown”), which extends outward from the sun in the form of the “solar wind.”

In the convective zone, energy is carried by rising and falling currents of hot gas called convective cells.

the photosphere is the sun’s outer surface—the visible layer from which most of the sun’s radiation and light escape.

Astronomy 49

.the sun and stars

sunspotsSunspotsarecoolerareasontheSun(butstillabout7,000degreesF).Theyappearinthephotosphereaspairsorgroupsofdarkspotsthatcanmeasuremorethan20,000milesacross.Whensunspotsarenumerous,thetotalenergycomingfromtheSunincreasesslightly.HotmaterialnearasunspotcanburstoutfromtheSuninwhatisknownasasolar flare.

Sunspots can cause static and drown out radio signals on Earth. If the energetic flow from the Sun is strong enough, it can cause power surges, damage sensitive electronics, and overload power systems on Earth.

Particles, radiation, and magnetic fields from solar flares bombard Earth.

sunspots are not permanent features of the sun’s surface. they come and go in cycles, usually over a period of about 11 years.

50 Astronomy

the sun and stars.

the sun and Earth’s WeatherTheSun’senergydrivesweatherandclimateonEarth.ItburnsoffEarth’smoisturebyevaporation,heatstheatmosphere,andcreateswindwhenoneairmassbecomeshotterthananother.Cloudscondensefromwatervaporthathasevaporatedfromtheoceans,andrainfromthesecloudsreturnswatertotheoceans.

the reason for our seasonsEarthhasseasonsbecauseofitstiltedaxis,whichkeepsthenorthernhemispheretippedtowardtheSunforhalftheyearandawayfortheotherhalf.Thenorthernhemispheregetsmoredirectsunlightinsummer,andlesssunlightsixmonthslaterinwinter.Thus,ourregionreceivesandretainslessheatfromtheSunduringthewinter.

FromourviewpointonEarth,theSunseemstoriseintheeastandsetinthewest.Butthatisactuallytrueonlyonthefirstdayofspringandthefirstdayoffall.Inthewinter,theSunrisessoutheastandsetssouthwest.Duringsummer,itrisesnortheastandsetsnorthwest.

SpRing

fall

SummeR winteR

Astronomy 51

.the sun and stars

The average

distance from

Earth to the Sun

is 93 million miles.

In July, we are

94.5 million miles

from the Sun;

around January 1

we are “only”

91.4 million

miles away.

Viewing the SunIt bears repeating: never view the Sun directly; your eyesight is too precious to risk. Telescope filters are not recommended because you are still looking in the Sun’s direction, so part of your line of vision falls outside the telescope lens. Also, filters can shatter, leaving the eyes unprotected, which can blind the observer instantly. View the Sun only by projection.

93 million

mileS

52 Astronomy

the sun and stars.

star QualityStarsaredividedintocolorcategories,fromhottesttorelativelycoolest:blueandblue-white,white,yellow,orange,andred.Starsarereferredtothiswaybecausetheyappeartobethesecolorswhenobservedthroughatelescope.

Blue and Blue-White stars.Thehottestofallstarsappearblueorblue-white.Theirtemperaturesrangefrom18,000degreesFtomorethan45,000degreesF.Anexampleofahot,blue-whitestarisRigelinOrion.

White stars.Whitestarshavetemperaturesfrom13,500degreesFtoabout18,000degreesF.SiriusinCanisMajor—thebrighteststarinoursky(notcountingoursun)—isawhitestar.

yellow stars.Yellowstarsarecooler,attemperaturesofabout9,000to13,500degreesF.TheSunisayellowstar,andsoisCapellainAuriga.

orange stars.Orangestarsarebetween6,000and9,000degreesF.ArcturusinBoötesisanorangestar.

red stars.Redstars,the“coolest,”arecoolerthan6,000degreesF.Oneofthebrighteststars,Betelgeuse,isaredstar.

BrightnessBrightnessisnotmeasuredthesamewayascolor.Justbecauseastarisnotashotasothersdoesnotmeanitisnotasbright.

Abrightstarisnotnecessarilylarge,either.Someofthebrighteststarsaresmallerthanother,fainterstars.Astar’sbrightnessinourskydependsonitsactualbrightnessorluminosityanditsdistancefromus.AstarmayappearbrightinourskyeitherbecauseitisgenuinelyverybrightorbecauseitisrelativelyclosetoEarth.

Astronomy 53

.the sun and stars

A star’s actual brightness is not the same as its apparent magnitude. A star can be really bright and yet, if it is an enormous distance from Earth, it may appear faint in our sky. The opposite also is true: A nearby star that is not terribly bright can shine brilliantly in our sky. Sirius, for example, is just 9 light-years from Earth. It shines more brightly in our sky than does Rigel, which actually is a much brighter star but so far away (about 800 light-years) that it appears fainter to observers on Earth.

Astronomy 55

.tools of the trade

ToolsoftheTradeYoucanobserveobjectsinthenightskywithyourunaidedeye.However,withbinocularsoratelescope,theimagesyouseewillappearbrighterandlarger.

BinocularsBinocularsareperfectforstargazing.Theycollectmorelightthanthehumaneye,soyoucansee50timesmorestarswith1050binoculars.Theyalsoimprovetheclarityandintensifythecolorsofthestarsyousee.

Unlikeatelescope,binocularsallowyoutousebotheyestoview.Binocularsshowanimagetherightwayup,whereastelescopesshowobjectsupsidedown.Binocularsareeasytotransportandlessexpensivethanmanytelescopes.

Because of their wide field of view, binoculars are perfect for studying the surface of the Moon, scan-ning the Milky Way, spot-ting Jupiter’s large moons, and viewing star clusters. An ideal size is 10350, which means the image is magnified 10 times and the main lenses are 50 millimeters in diameter. The 8340 and 7335 are also good choices.

obJective lenS

path of light

standard binoculars

pRiSm

pRiSm

eyepiece lenSeS

56 Astronomy

tools of the trade.

telescopesLikebinoculars,telescopesgathermorelightthanthehumaneye.Thetwomaintypesofopticaltelescopes—thosethatcollectvisiblelight—arerefractingandreflect-ing,withathirdtype,thecatadioptric,thatcombinesfeaturesoftherefractorandthereflector.

Principle of a refracting telescope

light enteRS

obJective lenS tube

focuS

focal plane eyepiece

Refracting telescopes use a system of lenses. At the large end of the telescope, the objective or front lens collects and focuses light. The eyepiece, the smaller lens you look through, is at the other end. Refracting telescopes produce sharp images.

refracting telescope

Some giant binoculars have lenses of 70 millimeters or more and magnifications of 15x to 20x. Wider lenses allow you to see more stars, but these giant binoculars are so heavy that they must be mounted on a tripod, like a telescope, for viewing.

Astronomy 57

.tools of the trade

Catadioptric telescope

the catadioptric telescope, also called a refracting-reflecting telescope, combines a large front lens with two mirrors. It has a short, enclosed tube and is often portable.

light enteRS

coRRectoR plate

SecondaRy miRRoR

tube pRimaRy miRRoR

eyepiece

light enteRS

diagonal miRRoR

pRimaRy miRRoReyepiece

focuS

focal planetube

Principle of a reflecting telescope

In the reflecting telescope, a concave (bowl-shaped) mirror at the base of an open tube collects and reflects light to a second, smaller mirror near the top of the tube. The eyepiece magnifies the image that the mirrors have formed. The reflec-tor is the most common type of telescope and a popular choice for backyard astronomers.

reflecting telescope

58 Astronomy

tools of the trade.

radio and X-ray telescopesRadiotelescopespickupimagesthatastronomerswouldnotbeabletoseeotherwise.Radiowavesfromspaceenterthetelescope’slargebowl-shaped(dish)antenna,andtheradioreceiverpicksupthesignals.Acomputerconvertsthesignalsintoimages.Radiosignalsrevealdetails,includingtemperatureandcomposition,ofobjectsinspacethatgiveoffradiowaves.

One of the most famous telescopes is the Hubble Space Telescope. The size of a school bus, this solar-powered reflecting telescope is an observatory that circles outside Earth’s atmosphere. Its sophisticated equipment is operated by remote control and can get spectacular images of space.

Astronomy 59

.tools of the trade

X-raytelescopeshelpscientistsdeterminethegalaxy’shotspots.CosmicX-rays—theinvisibleradiationemittedfromveryhotobjects—capturedbytelescopesaboveEarth’satmospherehelpscientistsstudydyingstars,collidinggalax-ies,andquasars,extremelybrightstarlikeobjectsthatgiveoffenormousamountsofenergy.

NASA’smostsensitiveX-raytelescope,theChandraX-rayObservatory,capturesX-raysfromtheedgeoftheobservableuniverse.

X-rays from distant galaxies are absorbed by Earth’s atmosphere, making them impossible to study from the ground.

the dish antennas of radio telescopes are much larger than the lenses or mirrors of optical telescopes. the Arecibo observatory in Puerto rico has the world’s largest radio telescope. Its dish measures 1,000 feet across.

60 Astronomy

tools of the trade.

Care of Binoculars and TelescopesFollowing the manufacturer’s recommendations and a few simple tips will help you keep your viewing equipment in good shape for many years.

• Handle binoculars and telescopes carefully and with respect. Repeated bumping, shaking, and dropping can cause the lenses to break or become misaligned.

• Keep your equipment clean. Keep lenses free from dirt, debris, fingerprints, and moisture. Use a cloth (such as a microfiber cloth) and cleaner made especially for lenses. Apply cleaner very sparingly to the cloth and never directly to the lenses.

• Keep dust from building up on lenses. Aside from normal cleaning, you may use a very soft brush (such as camel’s hair), or com-pressed air if you take some precautions. You want to avoid any contact with the lenses and any liquid from the can. Before use, avoid shaking the can. Always hold the can upright and never tilted or directly overhead while spraying. Use a few short (a second or two) bursts of air; stop immediately if the can starts to feel cold.

Astronomy 61

.tools of the trade

Whenever your

binoculars or

telescope are

not in use, be sure

to leave on the

lens caps.

• Keep water away. Protect equipment from the elements such as rain, snow, and—in particular—saltwater, which is corrosive. Repeated use in high humidity will also have a negative effect on equipment.

• In the field, use and wear the strap that comes with your binoculars to keep them safely around your neck.

• Store binoculars and telescopes in a cool (not cold), dry place, away from humidity and extreme temperatures, which will have a negative effect on the lens coatings and housing. Use the storage or carrying case and rubber eyecups (in the “up” position) that came with your equipment.

62 Astronomy

tools of the trade.

other Instruments Used in AstronomyAspectroscopeseparatesthelightcomingfromanobjectinspaceintoadetailedpatternofcoloredlines,muchlikearainbow,calledaspectrum.

Mountedinsideatelescope,aspecialeyepiececalledafilar micrometermeasuresthedistancebetweendoublestars.Anotherinstrumentformeasuringisthephotometer,whichmeasuresbrightness,ormagnitude,oflight.

AstrophotographyAstronomicalphotographyallowsyoutokeeparecordofyourobservationsoftheskies.Camerafilmishighlysensitivetolight,andobjectsappearbrighterandclearerinphotographsthanthroughatelescopeorbinoculars.Infact,thenightsky’ssubtlecolorsrecordedbycolorfilmaretruecolors.

Any35-millimeter,single-lens-reflex(SLR)camerathathasatimed-exposuresettingcantakegoodphotographsofstarsandplanets.The“B”settingontheshutter-speeddialwillholdtheshutteropenforaslongasthereleaseispressed.

FilmCamerashopswillhavethehigh-speedfilmthatisneededforastrophotography.Chooseblack-and-white,color-slide,orcolor-printfilmratedat400speedorfaster,although1000-speedfilmmightyieldthebestresults.Slidefilmsworkwellforastrophotographybecausetheytendtoshowmoreaccuratelythanprintfilmswhatthecamerasaw.

When having color-print film developed, be sure to tell the photo dealer your film has night-sky or star pictures on it. Give the technician samples of good astrophotos so you won’t get back prints that show the night sky in a weird shade of green or purple.

Astronomy 63

.tools of the trade

taking AstrophotosBegintosetupyourcelestialstudiobyoutfittingyourcamerawithaninexpensivecableshutterrelease.Setthefilm-speeddialtocorrespondwiththefilmyouareusing.Setthelensatthesmallestnumberonthef-stopring,settheshutter-speeddialon“B,”andsetthefocusringatinfinity.Placethecameraonatripodorothersolidsupportandaimitattheareayouwanttoshoot.

cable ShutteR ReleaSe

film Speed dial

focuSing Ring f-Stop

Ring

When you are ready to shoot, use the cable shutter release to open the shutter for 15 seconds, then try exposures of 30 and 60 seconds. (remember to advance the film after each shot.)

On a very dark

night you can

leave the shutter

open for minutes

—or even hours—

to capture the

stars’ movement

or even a meteor.

ShutteR Speed dial

film advance

As the stars move across the sky, longer exposures will give you star trails, a record of the path in the sky taken by the stars.

Astronomy 65

.tools of the trade

Digital PhotographyIfyouhaveusedadigitalcamera,youknowthatoneadvantageithasoverconventionalfilm-loadedcamerasisthatyougetinstantresults.Adigitalcameramightnot,however,bethebestcurrentchoiceforastrophotography.Picturestakenonfilmtendtoproducesharperimagesandmoreaccuratecolors.Manydigitalcamerashaveautomaticshutterspeedandaperture,soyoucan’tadjusttheexposuretime.

Ifyouwanttouseadigitalcameraforastrophotography,shootbrightsubjectslikethemoon.Exposuretimespossiblewithmanydigitalcamerasarelimitedtoafewsecondsatmost—tooshortforallbutthebrighteststarsandobjectsliketheMoonandbrightplanets.Galaxiesandnebulaearetoofaint.Youmaywanttoexperimentwiththeblack-and-whitemodeifyourcamerahasthatfeature.Picturesshotinblackandwhitecanappearsharperthancolorimages.

Astronomical CCD CamerasTherearedigitalcamerasusedespeciallyforastrophotography.Justlikeconsumer-typedigitalcameras,theyuseacharge-coupleddevice(CCD)insteadoffilmtorecordimages.ButtheCCDinanastronomicalcameraismoresensitivetolightthanphotographicfilm,soadigitalexposuredoesn’tneedtobeaslongtocapturethesameamountofdetail.Aone-minuteCCDexposurerecordsaboutthesamedetailasa30-minuteexposureonfilm.Thecameracancapturevividimagesofevenfaintobjects.

Onceusedonlybyprofessionalastronomers,theastro-nomicalCCDcameraisnowavailabletoamateurobservers.Itisfittedtotheeyepieceofatelescopeandlinkedtoahomecomputer.Withcomputerimagingsoftware,imagescanbeenhancedforbrightness,color,andcontrast.

Photos taken with a digital camera can be downloaded very quickly and easily to your computer.

To take pictures

through a

telescope, mount

the camera on a

separate tripod.

Aim the lens into

the telescope’s

eyepiece,

centered and

set as close to

the eyepiece as

possible. For

short exposure

times, hold the

camera up to

the eyepiece.

Light pollution is a serious energy waste that concerns professional astronomers and amateur observers alike. In north America electricity that wastefully illuminates the night sky costs an estimated $1 billion a year. If steps are not taken to control light pollution, someday people may not be able to see the stars or planets.

Astronomy 67

.Light Pollution

During the last

few thousand feet

of its journey to

Earth, starlight

that has traveled

trillions of miles

through deep

space gets

washed out by

bright city lights.

LightPollutionLightpollutionis,verysimply,toomuchartificiallightconcentratedinurbanareas(areasaroundcities).Theglareofstreetlights,outdoorsigns,parking-lotlights,dusk-to-dawnsecuritylights,andoutdoorfixturesaroundprivatehomescreatesglowingdomesovercitiesandtowns.Italsocanspoilyourviewofthenightsky.

the Air Up thereAircurrentsalsocanaffectobserving.TurbulentaircanruinviewsoftheMoon,planets,andfaintnebulae.WindlessnightsarebetterforstudyingtheMoonandplanets.Otherconditionsthatcanaffectobservingareclouds,highorlowhumidity,andairpollutionsuchasdustandchemicals.Faintstarsmaybevisibleonlyonclear,darknights.

Seeing in a Bright NightIf light pollution interferes with your stargazing, try these tricks.

• Cover your head down to your shoulders with a dark, opaque (nontransparent) cloth. This will help prevent light from streetlights, passing cars, and the glowing sky itself from ruining your night vision.

• Observe the skies as late at night as you can. As businesses close and people go to bed, less light pollution will intrude on your stargazing.

• Look for the bright objects. Urban sky glow will not keep you from seeing Sirius, Vega, Spica, Aldebaran, or similarly strong shiners. You should also be able to spot the brightest star clusters—the Pleiades, Hyades, and Beehive clusters, for example—and the spectacular Orion Nebula.

Astronomy 69

.you and Astronomy

YouandAstronomyPlanactivitiestohavesomefunwithyournewfoundknowledgeofastronomy.Invitefriends,andshareyourknowledgewiththem.

Visit a Planetarium or observatoryChecktheactivityscheduleofaplanetarium,sciencemuseum,orobservatoryinyourareaandroundupsomefriendstovisit.Whilethere,paycloseattentiontothepre-sentationsanddisplays.Atanobservatory,findoutaboutthetelescopesinuse.Mostofall,asklotsofquestions!Thepeopleonstaffnotonlyknowaboutastronomy,theyknowaboutpracticalobservinginyourarea.

Plan an observing sessionDevelopanobservingplanforasessionwhenyouwillsetupatelescopeorobservewithbinoculars.Assemblethechartsandguidebooksyouwillneed.Prepareared-filteredflashlightsoyoucanviewyourchartswithoutimpairingyournightvision.Getanotebookorcreateanobservinglog.

Besuretochecktheweatherforecastanddressappropriately.Eveninmildseasonslikethespring,nightscangetcold.Itpaystohaveextralayersaswellasgloves,ascarf,andahat.

Scout out the area beforehand to make sure you are aware of any conditions or potential hazards on the ground that you might miss when you come back at night.

70 Astronomy

you and Astronomy.

throw a star PartyPlantodoeverythingyoudidforyourownobservingsession,plusmore.Findagooddateandaplacewithplentyofroomforthenumberofpeopleyouwanttoinvite.Consideringthetimeofyearandhowfarnorthyoulive,developalistofspaceobjectsyouwishtofindduringthestarparty.

ConsiderinvitingScoutsinyourtroop,yourneighbors,familyandfriends,classmates,andteachers.Whenyouinvitethem,besuretocoversuchsubjectsasweatherandproperdress,observingetiquette,andsafety.Encouragethosewhohavebinocularstobringthem.

Contact a local astronomy organization or club to volunteer to help with a public star party. If you are unsure whom to contact, ask at a college in your community.

moon observation

Date: _________________________________ Time: __________________________

Telescope: _____________________________ Power: __________________________

Crater(s): _______________________________________________________________

Notes: _________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Write a summary of your observing session and share it with your counselor.

Astronomy 73

.Careers in Astronomy

CareersinAstronomyIfyouhaveenjoyedearningtheAstronomymeritbadge,youmightwanttoconsideracareerinthescience.Tobeanastronomer,youmustbeobservant,logical,imaginative,intuitive,andcurious—yourgoalisnothinglessthantounder-standthenatureoftheuniverse.Ithelpstobepatientandtohavethedeterminationtostickwithadifficultproblemorlongprojectuntilyouhaveseenitthrough,whichcantakeyears.

Astronomerstypicallyaremathandsciencewhizzes,skilledwithcomputers.Youwillneedtotakehighschoolcalculusorprecalculus,physics,chemistry,andcomputersciencetoprepareforcollegeastronomy.

Reading,writing,andspeakingskillsalsoareimportant.Astronomersgivetalksatprofessionalmeetingsandwritepapersforscientificjournals.So,whenchoosingyourcourses,donotneglectlanguage,communication,andsocialstudies.

Where Astronomers Are FoundMostastronomersteachatcollegesanduniversitiesandalsodosomeresearchinaparticularareaofastronomy,suchasplanetaryscience,solarastronomy,orthestudyofstarsorgalaxies.Manywhoteachastronomymayworkinthephysicsdepartmentoftheiruniversity.Often,thosewhoteachastronomyalsoteachphysics.

Aboutathirdofprofessionalastronomershavecareersinfederalgovernmentoratgovernment-supportednationalobservatoriesandlaboratories.About10percentofastronomersareemployedinbusinessorprivateindustryliketheaerospacefield.

What Astronomers DoObservationalastronomersdesignandcarryoutobservingprogramswithatelescopeorspacecraft,buttheydonotspendalltheirtimelookingthroughtheeyepieceofatelescope.They

74 Astronomy

Careers in Astronomy.

typicallyspendonly10to30nightsperyearworkingatanobservatoryorgettingobservationsfromspacecraft.Andeventhen,theyarenotlookingupattheheavens.Theyareworkingatcomputers,analyzingandinterpretingtheinformationcollectedbythetelescopeandotherinstruments.

Peopleinterestedinastronomyalsomayfindcareersassciencelibrariansorteachers,sciencewriters,planetariumorsciencemuseumdirectors,observingtechniciansorassistants,telescopeoperators,andopticalengineers.Relatedcareeropportunitiesmightbefoundincomputing,imageprocessing,andinstrumentdesignandbuilding.

Professional astronomers such as theoretical astrophysicists may never work directly with observing equipment. they often do their research using supercomputers and complex computer models.

Space for AmateursSerious amateur observers make important contributions to astronomy. Amateurs are the chief comet-finders. They map storms on Mars and Jupiter, track the movements of asteroids, and discover supernovas. Their thousands of telescopes, computers, and electronic cameras far outnumber the comparatively few large university and government observatories. You might prefer to remain a hobbyist, where you can do real science and you get to decide how to spend your stargazing nights.

Astronomy 77

.Astronomy resources

AstronomyResources

scouting LiteratureDeck of Stars; Night Sky pocketguide; Chemistry, Computers, Geology, Nuclear Science, Photography, Radio, Space Exploration,andWeathermeritbadgepamphlets

Books

Brunier,Serge,andAkiraFujii.The Great Atlas of the Stars.FireflyBooks,2001.

Covington,MichaelA.Astrophotography for the Amateur,2nded.CambridgeUniversityPress,1999.

Davis,KennethC.Don’t Know Much About Space.HarperTrophy,2001.

———.Don’t Know Much About the Solar System.HarperCollins,2001.

Dickinson,Terence.NightWatch: A Practical Guide to Viewing the Universe. FireflyBooks,2006.

Harrington,Philip,andEdwardPascuzzi.Astronomy for All Ages.GlobePequotPress,2000.

Lambert,David.The Kingfisher Young People’s Book of the Universe.KingfisherBooks,2001.

Moore,Patrick,ed.Astronomy Encyclopedia.OxfordChildren’sBooks,2002.

Price,FredW.The Planet Observer’s Handbook.CambridgeUniversityPress,2000.

Schaaf,Fred.40 Nights to Knowing the Sky: A Night-by-Night Skywatching Primer.OwlBooks,1998.

Trefil,James.Other Worlds: Images of the Cosmos from Earth and Space.NationalGeographic,1999.

CDs, DVDs, and VideosAmazing Universe III.Hopkins

Technology,1995,CD-ROM.

IMAX Cosmic Voyage.WarnerHomeVideo,1996,DVD.

Savage Sun.DiscoveryChannel,1999,videocassette.

The Solar Empire: A Star is Born.DiscoveryChannelandTheLearningChannel,1997,videocassette.

Visit the Boy Scouts of America’s official retail Web site at http://www.scoutstuff.org for a complete listing of all merit badge pamphlets and other helpful Scouting materi-als and supplies.

78 Astronomy

Astronomy resources.

magazinesAstronomyKalmbachPublishingCo.21027CrossroadsCircleP.O.Box1612Waukesha,WI53187-1612Toll-freetelephone:800-533-6644Website:http://www.astronomy.com

Sky and TelescopeSkyPublishing90ShermanSt.Cambridge,MA02140Toll-freetelephone:866-644-1377Website:http://www.skyandtelescope.com

organizations and Web sites

the Astronomical League9201WardParkway,Suite100KansasCity,MO64114Telephone:816-333-7759Website:http://www.astroleague.org

national Aeronautics and space AdministrationNASAHeadquartersSuite5K39Washington,DC20546-0001Telephone:202-358-0001Website:http://www.nasa.gov

national optical Astronomy observatory 950NorthCherryAve.Tucson,AZ85719Telephone:520-318-8000Website:http://www.noao.edu

national radio Astronomy observatory

520EdgemontRoadCharlottesville,VA22903Telephone:434-296-0222Website:http://www.nrao.edu

the Planetary society65NorthCatalinaAve.Pasadena,CA91106-2301Telephone:626-793-5100Website:http://planetary.org

sky mapsWebsite:http://www.skymaps.com

solar system Exploration: PlanetsWebsite:http://sse.jpl.nasa.gov/planets/index.cfm

space telescope science Institute 3700SanMartinDriveBaltimore,MD21218Telephone:410-338-4444Website:http://www.stsci.edu

spaceWander.com™Website:http://www.spacewander.com

spaceweather.comWebsite:http://www.spaceweather.com

Astronomy 79

.Astronomy resources

AcknowledgmentsTheBoyScoutsofAmericathanksWilliamCress,BeaverFalls,Pennsylvania,anadvancednucleartechnologistbytradewhoisalongtimeAstronomymeritbadgecounselorandanexperiencedamateurastronomer.Weappreciatehisknowledge,advice,andsupportimmenselyinhelpingtoupdatetheAstronomymeritbadgepamphlet.Hegatheredanimpressivegroupoffel-lowastronomerstoassistinthiseffort,andwethankthemhere,aswell:

• JaneKonrad,PittsburghRegionalCenterforScienceTeachersandthePennsylvaniaNASAEducatorResourceCenter

• DanMalerbo,BuhlDigitalDome,CarnegieScienceCenter,Pittsburgh,Pennsylvania

• TimManka,retiredscienceinstruc-tor,anAstronomymeritbadgecounselorsince1966

• JeanPhilpott,BuhlDigitalDome,CarnegieScienceCenter,Pittsburgh,Pennsylvania

• PatPlunkett,Wheeling(WestVirginia)JesuitUniversity

• TomReiland,founder,WagmanObservatory,westernPennsylvania

TheBoyScoutsofAmericaisgratefultoAlDornandtheOmahaAstronomicalSocietyfortheirexpertise,assistance,andguidanceinupdatingrequirementsfortheAstronomymeritbadgeandsup-portindevelopingthenewtextforthe2004edition.TheSociety’sWebsite,foundathttp://www.omahaastro.com,providesawealthofinformationforthebeginneramateurastronomeraswellasthosewhohavedevelopedamoreseriousinterest.

Photo and Illustration Credits

Ablestock.com—page60

BrandXPictures—page61

Comstock—page29(top)

DigitalVision™Astronomy&SpaceCD—page51

GeminiObservatory/NOAO*/AURA†/NationalScienceFoundation,courtesy—page64

Goodshoot—page5

NAIC—AreciboObservatory,afacilityoftheNationalScienceFoundation,courtesy—page59

NASA,courtesy—cover(galaxy);pages27(top),47,74(top),and76

NASA,JetPropulsionLaboratory,courtesy—pages27(bottom),29(bottom),30,and36(top)

NASA,MarshallSpaceFlightCenter,courtesy—page72

*NationalOpticalAstronomyObservatory†AssociationofUniversitiesforResearchinAstronomy

80 Astronomy

Astronomy resources.

NationalOpticalAstronomyObservatory/AssociationofUniversitiesforResearchinAstronomy/NationalScienceFoundation,courtesy—page74(bottom)

NOAO/AURA/NSF,courtesy;photobyDavidTalent—page23

©Photos.com—cover(solar system model, satellite dish, moon, Mars); pages6,9,24,26,28(all),36(bottom), 38,44(top),46,58,66–67(both),69,75,and76 (background)

RoyalSwedishAcademyofSciences,courtesy—page49(top)

SOHOProject,NASAGoddardSpaceFlightCenter,courtesy—page49(bottom)

Wikipedia.org/DanteAlighieri,courtesy—page37

Wikipedia.org/GeoffreyNotkin,courtesy—cover(meteorite)

AllotherphotosarethepropertyoforareprotectedbytheBoyScoutsofAmerica.

JohnMcDearmon—allillustrationsonpages7,12,15,17,19,21,31–32,34,40–45(all illustrations),48,50,and55–57

BrianPayne—page10

Merit badge libraryThough intended as an aid to Boy Scouts, Varsity Scouts, and qualified Venturers in meeting merit badge requirements, these pamphlets are of general interest and are made available by many schools and public libraries. The latest revision date of each pamphlet might not correspond with the copyright date shown below, because this list is corrected only once a year, in January. Any number of merit badge pamphlets may be revised throughout the year; others are simply reprinted until a revision becomes necessary.

If a Scout has already started working on a merit badge when a new edition for that pamphlet is introduced, he may continue to use the same merit badge pamphlet to earn the badge and fulfill the requirements therein. In other words, the Scout need not start all over again with the new pamphlet and possibly revised requirements.

American Business 2002American Cultures 2005American Heritage 2005American Labor 2006Animal Science 2006Archaeology 2006Archery 2004Architecture 2008Art 2006Astronomy 2004Athletics 2006Automotive Maintenance 2008Aviation 2006Backpacking 2007Basketry 2003Bird Study 2005Bugling (see Music)Camping 2005Canoeing 2004Chemistry 2004Cinematography 2008Citizenship in the

Community 2005Citizenship in the Nation 2005Citizenship in the World 2005Climbing 2006Coin Collecting 2008Collections 2008Communication 2009Composite Materials 2006Computers 2009Cooking 2007Crime Prevention 2005Cycling 2003Dentistry 2006Disabilities Awareness 2005Dog Care 2003Drafting 2008Electricity 2004Electronics 2004Emergency Preparedness 2008Energy 2005

Photography 2005Pioneering 2006Plant Science 2005Plumbing 2004Pottery 2008Public Health 2005Public Speaking 2002Pulp and Paper 2006Radio 2008Railroading 2003Reading 2003Reptile and

Amphibian Study 2005Rifle Shooting 2001Rowing 2006Safety 2006Salesmanship 2003Scholarship 2004Scuba Diving 2009Sculpture 2007Shotgun Shooting 2005Skating 2005Small-Boat Sailing 2004Snow Sports 2007Soil and Water

Conservation 2004Space Exploration 2004Sports 2006Stamp Collecting 2007Surveying 2004Swimming 2008Textile 2003Theater 2005Traffic Safety 2006Truck Transportation 2005Veterinary Medicine 2005Water Sports 2007Weather 2006Whitewater 2005Wilderness Survival 2007Wood Carving 2006Woodwork 2003

Engineering 2008Entrepreneurship 2006Environmental Science 2006Family Life 2005Farm Mechanics 2008Fingerprinting 2003Fire Safety 2004First Aid 2007Fish and Wildlife

Management 2004Fishing 2009Fly-Fishing 2009Forestry 2005Gardening 2002Genealogy 2005Geology 2005Golf 2002Graphic Arts 2006Hiking 2007Home Repairs 2009Horsemanship 2003Indian Lore 2008Insect Study 2008Journalism 2006Landscape Architecture 2008Law 2003Leatherwork 2002Lifesaving 2008Mammal Study 2003Medicine 2009Metalwork 2007Model Design and Building 2003Motorboating 2008Music and Bugling 2003Nature 2003Nuclear Science 2004Oceanography 2009Orienteering 2003Painting 2008Personal Fitness 2006Personal Management 2003Pets 2003

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ASTRONOMY - Troop 577 Wichita, Kansas€¦ · affect astronomy. 3. With the aid of diagrams (or real telescopes if available), do each of the following: ... With the aid of diagrams,