National Aeronautics and Space Administration

SciScienceBackground

constellation Q&as

Teacher’s

NASA / AmazingSpaceScienceBackground:ConstellationQ&As

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1. What are constellations?

Constellationsare“pictures”intheskythatancientastronomersperceived

byimagininglinesorrelationsbetweenstarsthatappeargrouped.Asimple,

geometricstarpatternliesattheheartofeachconstellation.Constellations

depictpeople,inanimateobjects,realanimals(birds,insects,andlandand

watercreatures),andmythologicalanimals(serpents,dragons,andflying

horses).

Generally,thereislittlesimilaritybetweenthegeometricstarpatternon

whichtheconstellationisbasedandthefullydetaileddrawingoftheconstel-

lation.Forexample,thewinterconstellation,Orion,theHunter,withfour

brightstarsatthecornersofatrapezoidandthreestarsinarownearthe

center,doesn’tlookmuchlikeaperson.

Creatingtheconstellationshelpedpeoplerememberthepositionsofthe

stars.Knowingthepositionsofthestarshelpedfarmerskeeptrackofthe

seasonsandtravelerskeeptrackofwheretheywere.

2. Are all the stars from a constellation in the same area of the sky?

Chancealignmentsofstarshavecreatedthepatternsweseeinthesky.

Starsthatappeartobenexttoeachothermayactuallybeveryfarfromeach

other,andatverydifferentdistancesfromEarth.Starsthatappeartobeof

thesamebrightnessmayalsolieatvastlydifferentdistancesfromEarth.In

thatcase,thestarfartherawayistrulymuchbrighterthantheonenearerto

Earth.

3. What are constellation myths?

Constellationmythsareancientstoriesaboutthegods,heroes,andmytho-

logicalcreatures(serpents,dragons,andflyinghorses)featuredinthecon-

stellations.TheGreeksandRomanscreatedthestoriesfortheconstellations

NASA / AmazingSpaceScienceBackground:ConstellationQ&As

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intheNorthernHemisphere,andforafewintheSouthernHemispherethat

theycouldsometimessee,closetothehorizon.

Othersocietieshadtheirownmythologiesforthestars.Thestorieswerepart

oftheirreligions,helpingthemtoexplaineverydayevents,suchasthesea-

sons.Thesestoriesusuallyhaveahero,whowasgivenanhonoraryplacein

thesky,aseitherarewardoratribute.

MostoftheconstellationsintheSouthernHemispherearemoremodern

andwereidentifiedandnamedintheseventeenthcentury,whenEuropean

explorersfirstsailedthesouthernseas.Theyarenotusuallyassociatedwith

myths.

4. How many constellations are there?

Theentiresky(NorthernandSouthernhemispheres)hasbeendividedinto

88regions,eachcontainingaconstellation.

5. Who created the constellations?

ManyofourmodernconstellationscomefromtheancientGreeks.The

Greeks,however,didnotinventthem.Manypeoplespeculatethatthe

ancientBabyloniansandSumeriansaretheactualinventorsofmanyof

theconstellations.Theseculturespassedthetraditionontotheancient

EgyptiansandGreeks.

MuchofwhatweknowaboutGreekastronomycomesfromLatintransla-

tionsoftheArabictranslationsoftheoriginalGreekwork.Forexample,

thetitleofPtolemy’stext,The Almagest,isnottheoriginalGreektitle,but

anArabictranslation.Ptolemynamedstarsbasedontheirpositionsinthe

constellations,suchas“mouthofthesouthernfish,”astarintheconstel-

NASA / AmazingSpaceScienceBackground:ConstellationQ&As

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lationofPisces.ButtheArabsnamedstarsforpeople,andaddedthose

Arabicstarnamestotheconstellations.So,forexample,theygavethename

“Fomalhaut”tothatsamestar,inPisces.ThisiswhywehaveArabicnames

forstarsinGreekconstellationsthatbearLatinnames.

6. Why did the ancients need the constellations?

AncientfarmerslivingneartheEquator,wheretheseasonsdon’tvarymuch,

mayhaveusedthestarstotellthemwhentoplantandharvesttheircrops.

Sincesomeconstellationsareonlyvisibleatcertaintimesoftheyear,notic-

ingtheirappearancecanrevealwhatmonthitis.Somehistoriansthinkthe

constellationmythswereinventedtohelpthefarmersremembertheconstel-

lations.

Throughouthistory,thestarshavealsobeenusedfornavigation,either

acrossadesert,orabodyofwater.Travelershavehistoricallyreliedonthe

NorthStar,Polaris,tomarktheirway.Polarisisthelaststarattheendof

thehandleoftheasterism*oftheLittleDipper,intheconstellationofthe

LittleBear.DuetoEarth’srotation,thestarsappeartomoveacrossthe

nightsky.ButPolarisislocatedabovetheaxisonwhichtheEarthrotates,

soitdoesn’tchangepositionappreciablywithtime.

7. How do we use the constellations?

Constellationsgivemodern-dayskywatchersameansofkeepingtrackofthe

manybrightstarsinthesky.Bylookingforgroupsofstarsinaparticular

pattern,professionalandamateurastronomerscanlocatespecificstars

withinthegroup.Forexample,manypeoplecanpickoutthetrapezoidalwin-

terstarpatternknownasOrion.OncetheyhavefoundOrion,theycanfind

Betelgeuse(thestarintheupperleft“corner”ofthetrapezoidformedbythe

brightstars)andRigel(thestarinthelowerright“corner”ofthesametrap-

NASA / AmazingSpaceScienceBackground:ConstellationQ&As

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ezoid),twoofthebrighteststarsinthisregionofthesky.Constellationsarealso

usedtolocateotherobjects,suchasgalaxiesandnebulae(areaswheregasand

dustareclustered).

8. Do other cultures also have constellations?

Manydifferentcultures,includingtheGreeks,Mayans,Indians,NativeAmericans,

andCeltscreatedtheirownnamesforvariousgroupsofstars,alongwithdiffer-

entmythologicalstoriesaboutthem.Thesestargroups,aswellastheirnamesand

stories,rarelycorrespondtothoseofothercultures.

Thereisonepatterninthenorthernskythatmanycultureshaverecognized.

Itistheasterism*called,intheU.S.,theBigDipper.InsouthernFrance,it

iscalleda“saucepan”andinBritain,a“plough.”TheMayanscalleditSeven

Macaw,aparrot,buttheHindussawsevenwisemen.TheMicmacIndiansof

MaritimeCanada,andotherNorthAmericanIndianssawabear(thepartwesee

asthebowlofthedipper),withhunterstrackingit(thehandle).Therunaway

slavescalleditthe“drinkinggourd”andfolloweditnorthtofreedom.Therefore,

theBigDipperbecameasymboloffreedom.Itisunusualforsomanyculturesto

pickoutthesamesetofstars.Perhapsitisbecauseallsevenstarsareverybright.

*Theterm“asterism”isusedheretoindicateasubsetofthestarsinaconstellationthatmakeaseparate,recognizedpatternoftheirown.TheLittleDipperissuchagroupofstars,foundwithintheLittleBear,oneofthe88constellations.ThestarsmakinguptheBigDipperareanother“asterism,”fallingwithintheconstellationoftheGreatBear.