astronomy - welcome to troop 10, yardley, pa
TRANSCRIPT
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.
Your counselor can be as important to you as a coach is to an athlete. Use all of the resources your counselor can make available to you. This may be the best chance you will have to learn about this particular subject. Make it count.
If you or your counselor feels that any information in this pamphlet is incorrect, please let us know. Please state your source of information.
Merit badge pamphlets are reprinted annually and requirements updated regularly. Your suggestions for improvement are welcome.
Send comments along with a brief statement about yourself to Youth Development, S209 • Boy Scouts of America • 1325 West Walnut Hill Lane • P.O. Box 152079 • Irving, TX 75015-2079.
Who Pays for This Pamphlet?This merit badge pamphlet is one in a series of more than 100 covering all kinds of hobby and career subjects. It is made available for you to buy as a service of the national and local councils, Boy Scouts of America. The costs of the development, writing, and editing of the merit badge pamphlets are paid for by the Boy Scouts of America in order to bring you the best book at a reasonable price.
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.
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.
16 Astronomy
stars and Constellations.
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.
18 Astronomy
stars and Constellations.
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.
20 Astronomy
stars and Constellations.
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.
22 Astronomy
stars and Constellations.
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
.stars and Constellations
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
stars and Constellations.
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
.stars and Constellations
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
.the Planets and our solar system
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
the Planets and our solar system.
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
.the Planets and our solar system
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
the Planets and our solar system.
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
.the Planets and our solar system
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 Planets and our solar system.
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
.the Planets and our solar system
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
the Planets and our solar system.
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
.the Planets and our solar system
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
.the moon—our nearest neighbor
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
the moon—our nearest neighbor.
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
.the moon—our nearest neighbor
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—our nearest neighbor.
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
.the moon—our nearest neighbor
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
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