Used of Constellatio1n
description
Transcript of Used of Constellatio1n
National Aeronautics and Space Administration
SciScienceBackground
constellation Q&as
Teacher’s
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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
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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-
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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-
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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.