Milky Way Globular Clusters - WSAAG · There are 157 Milky Way globular clusters in the Catalog of...
Transcript of Milky Way Globular Clusters - WSAAG · There are 157 Milky Way globular clusters in the Catalog of...
MilkyWayGlobularClusters(RobHorvat)
47Tucanae(47Tuc).Credit:GerryAarts(WSAAG).Thisglobularclusterhasmorethanonemillionstars.
MulCpleStarSystemsAsmallCghtgroupofstars(usually2or3)thatareboundtogetherbygravityformamul3plestarsystem.Atwo-starsystemissimplyreferredtoasabinarystar.Visually,onestarmightbeseentoorbitanotheroveraperiodofdecadesorcenturies.
Mostbinarystarsareseparatedbyalotlessthan200”and0.3lightyears.
BetaMonoceroCs
AlphaCentauri
Star Distance(LtYrs) Separa3on Sep(AU) Sep(LtYrs)
AlphaCentauriAB 4.3 5” 7 0.0001
Acrux 322 4” 390 0.006
BetaMonoceroCs(A-BC) 680 7.4” 1,540 0.024
BetaCygni(Albireo) 430 35” 4,067 0.064
Beta1,2Capricorni 340 205” 21,300 0.338
Anopen cluster is a loosely bound group of a hundred, a few hundred or a fewthousandstars(M11has2,900stars).
Mostofthewell-knownopenclustersaresomewherebetween10’and100’insizeand10to30lightyearsacross.About2-3lightyearsbetweeneachstar.
BuXerflyCluster(M6).Credit: Narayan Mukkavilli (WSAAG).Approximately100stars.Clusteris50-100millionyearsold.
OpenClusters
The escape velocity of the system isless than the average velocity of itsstars so open clusters tend todisperse a\er a few 100 millionyears.
OpenCluster Distance(LtYrs) AngularSize Size(LtYrs)
M45(Pleiades) 430 120’ 15
IC2602(SouthernPleiades) 530 100’ 15
IC2391(OmicronVelorumCluster) 570 60’ 10
M44(Beehive) 610 90’ 16
M7(PtolemyCluster) 980 80’ 23
NGC2516(SouthernBeehive) 1,300 30’ 11
M6(BuXerflyCluster) 1,600 30’ 14
M47 1,600 25’ 12
M41 2,300 40’ 27
M50 3,100 15’ 14
NGC6231(NorthernJewelBox) 4,100 14’ 17
M46 4,900 20’ 29
M11(WildDuckCluster) 6,100 14’ 25
NGC4755(JewelBox) 6,400 10’ 19
NGC3766(PearlCluster) 7,200 9’ 19
NGC3293(GemCluster) 7,600 6’ 13
Mostoftheknownopenclustersarelessthan200millionyearsold.TheJewelBox(NGC4755)isoneoftheyoungestatonly7millionyearsold.
PtolemyCluster(M7).Credit:NarayanMukkavilli(WSAAG).Approximately100stars.Clusteris220millionyearsold.
Thereareover1000knownopenclusters inourgalaxybuttherecouldbe10Cmesthisnumber.OpenclustersarefoundinthegalacCcdiskandmoveinrotaConwiththedisk.Youngeropenclustersaremoredenselyconcentratedinthespiralarmsofthegalaxywherethelevelsofhydrogengasarehigher.
NGC1566.Credit:ESA/Hubble&NASA
The typical distancebetween stars in aglobular cluster isaboutonelightyear.
In the core ofOmegaCentauri,theaverage distancebetween any twostars is about1/3ofalightyear.
OmegaCentauri.Credit:CharlesYendle(WSAAG).Theclustercontainsperhaps5millionstars.
GlobularClustersAglobular cluster isaCghtlyboundgroupof tensof thousands,o\en100,000sandoccasionallymillionsofstars.Theyaresphericalinappearance.
Thedifference in shapebetweenanopenclusterandglobular cluster is somewhatlikethedifferencebetweenanasteroidandasphericalmooninthesolarsystem.
Asteroid243Ida.60kmx25kmx19km.TakenbyGalileo1993.Credit:NASA/JPL
Saturn’smoonMimas.diameter396km.LargeHerschelCrater.TakenbyCassini2010.Smallest known roundastronomicalbody.“The potato radius”,approximately200km.Credit:NASA/JPL/SSI.
Enoughmass/starsanditpullsintoasphere.
OpenclusterNGC6231.Credit:NarayanMukkavilli(WSAAG)
47Tuc.Credit:TedDobosz(WSAAG)
M22.Credit:NarayanMukkavilli(WSAAG)
WilliamHerschelwasthefirsttousethenameglobularclusterforhisdescripConoftheminhis1789catalogofdeepskyobjects.
Very liXle is known about how globular clusters are formed or why they haveorbitsoutsidethegalacCcdisk.
AgeofGlobularClusters
Theuniverseisabout13.8billionyears(or13.8Gyr)old.Globularclustersaresomeoftheoldestobjects in theUniverseandwereprobably formedbefore thematerialoftheGalaxyflaXenedintothepresentthindisk.
GlobularCluster Age(billionsofyears)
OmegaCentauri 11.5
47Tuc 13
M2 13
M3 11.4
M4 12.2
M5 10.6
M10 11.4
M12 12.7
M13 11.7
M15 12
M22 12
MostglobularclustersinourgalaxyshowalackofOandBtypebluestars.
Globularclusterscontainmanylow-massredstarsandintermediate-massyellowstars<0.8solarmasses.(Source–Hyperphysics,DeptofPhysicsandAstronomy,GeorgiaStateUniversity).
StarformaConshouldhavestoppedintheseclustersalmost13billionyearsago,soonlyoldstarsareexpectedtobefoundthere.
StarsarecomposedmostlyofHydrogenandHelium.TheSunis73%Hydrogenand25% Helium. Heavier elements (oxygen, carbon, iron etc), called metals inastronomy,onlyaccountfor2%ofitsmass.
Metallicity
Metallicity [Fe/H] = log(Fe/H)STAR - log(Fe/H)SUN compares the raCo of iron tohydrogeninastarwiththeSun.BydefiniCon,theSun(4.6billionyearsold)hasmetallicity[Fe/H]=0.
Spectral analysis for thousands of stars gives the range for metallicity to bebetween-4and+1.
Hydrogen
Helium
Metals
Popula3onIStars–inthegalac3cdisk(e.g.openclusters),[Fe/H]>-1.Thesestarswereformedfromaninterstellarmediumprogressivelyenrichedwiththeejectedmaterialsof redgiantsandsupernovae. It is thereforeassumedthatthehighertheraCo,themorerecentlythestarwasformed.Astarwithmetallicity+1wouldhave10CmestheironcontentoftheSun.
Popula3onIIStars-inglobularclusters&galac3cbulge,[Fe/H]<-1.Halostarshavenothadaccesstotheheavierelementsofthedisk.Astarwithmetallicity-2wouldhave100CmeslessironthantheSun.
ThebeliefwasthatglobularclustersconsistedofasinglepopulaConofmetalpoorstarsthatformedtogether.Globularclustersshouldconsistpredominantlyofolder“populaConII”yellowtoredstars.
GlobularCluster
Metallicity GlobularCluster
Metallicity GlobularCluster
Metallicity
M15 -2.37 M19 -1.74 M12 -1.37
M92 -2.31 M22 -1.70 M28 -1.32
NGC5053 -2.27 M2 -1.65 M5 -1.29
M30 -2.27 OmegaCen -1.53 M75 -1.29
M68 -2.23 M70 -1.62 M14 -1.28
NGC2419 -2.15 M79 -1.60 M62 -1.18
M53 -2.10 M10 -1.56 M4 -1.16
NGC6397 -2.02 NGC6752 -1.54 NGC2808 -1.14
M56 -1.98 M13 -1.53 M107 -1.02
M55 -1.94 M3 -1.50 M71 -0.78
M9 -1.77 M54 -1.49 47Tuc -0.72
M80 -1.75 M72 -1.42 M69 -0.64
However,manyMilkyWayglobularclusterssuchasOmegaCentaurihavecomplexformaConhistoriesandconsistofatleasttwodisCnctpopulaConsofstars.
OmegaCentauri.Credit:TedDobosz(WSAAG)
Bluestarshavebeenfoundinthecentralregionsofmanyglobularclusters.OneexplanaConfortheseistheformaConofbluestragglers.
Thestarsinthecoreofaglobularclustercanbesoclosethatoccasionallytwowillcollide,formingalargerandhoXerstar(bluestraggler).
Duetotheoldageofglobs,manythousandsofcollisionsmayhaveoccurredsincetheclusterformed.
Anearmisscouldalsoresultinaclosebinarywhereamoremassivestarsiphonshotgasesoffitscompanion.TheincreasedmassmakesthisstarhoXerorbluer.
BlueStragglers
CoreareaofOmegaCentauri(1.3’x1’).Credit:NASA,ESA,andtheHubbleSM4EROTeam.
100,000StarsPicturedintheCentreofOmegaCentauri
BlueStragglersinNGC6362(Ara).Credit:ESA/Hubble&NASA
GalacCcCannibalismAsignificantnumber(?)ofglobularclustersmayhavecomefromdwarfsatellitegalaxiesthatwereabsorbedbytheMilkyWayGalaxy.
The high density of the globular clusters would allow them to survive in ourgalaxy’shalo.
There is also some debate as to whether globular clusters are disCnct andseparateobjectstodwarfspheroidalgalaxies.
OmegaCentauri isthoughttobetheremnantnucleusofadwarfsatellitegalaxycapturedandstrippedofitsouterstars.
Of similar luminosity to 47 Tuc,M54 may once have been the nucleus of theSagiXariusDwarfEllipCcalGalaxy(SgrDEG).At86,400lydistance,itbecomesthefirstextra-galacCcglobularclusterdiscovered(CharlesMessier1778).
M54.Credit:JimMisC(MisCMountainObservatory)
NGC2808.Credit:NASA,ESA,A.Sarajedini(UniversityofFlorida)andG.PioXo(UniversityofPadua(Padova))
It is thought that radiaCon pressure fromcomponent stars should drive interstellargasesoutof globular clustersearly in theirformaCon.
Perhaps massive clusters like NGC 2808exert enough gravity to hold onto gasesearlyintheirformaCon.Asaresult,asecondandathirdgeneraConofstarsmightform.
Or like Omega Centauri, it could bemasqueradingasaglobularcluster…adwarf satellitegalaxy strippedofmostofitsmaterialbytheMilkyWay.
Like47Tuc,NGC2808isthoughttocontainoveronemillionstars.Analysis of HST data for this massive glob provides evidence that star birthoccurredover3generaConsearlyinthecluster'slife.EachsuccessivegeneraConappearingslightlybluer.
AsearchforJupiter-sizedplanetsin47Tuc,carriedoutbyateamofastronomersusing theHubbleSpaceTelescope,cameupempty-handed.Thework involvedchecking34,000starsintheclusterforsignsoflargetransiCngplanets.
TheabsenceofanyposiCve results strengthens theargument thatplanetsarerareornonexistentinglobularclustersbecauseoftheirverylowconcentraConofheavyelements.
AnyPlanets?
DiametersofGlobularClustersOmega Centauri is considered to be the most massive of the Milky Way globs.However, ifyoudosomecalculaConsbasedonangularsize (visual)anddistance:NGC2419is321lightyearsindiameter.M54is229lightyearsindiameter.OmegaCentauriis6that178lightyearsindiameter!
Attheoppositeend,Terzan9isonly1lightyearindiameter.
TheaveragediameterofMilkyWayGalaxyglobularclustersisabout70lightyears.Themediandiameterisabout60lightyears.
Diameters are calculated from angular size and distance. Given angular sizes areusuallyvisualandrathersubjecCvee.g.wheredoestheclusterend?Thiswillalsodependonthesizeoftheaperture.
ThefollowingcroppedimagesofOmegaCentaurisimulatehowitsextentcanvaryunderdifferentcircumstances.
Credit:TedDobosz Credit:CharlesYendle Credit:GerryAarts
Visual:10x60binoculars18’ Visual:30inchTelescope36’ Photographed65’
Onthewhole,calculateddiametersareconsiderablyunder-esCmated.OmegaCentauri’sdiametercalculatedfromavisual36’is178ly.Fromaphotographicdiameterof65’itis320ly.
Globular clusters do notmove in lockwith the rotaCon of the galacCc disk butorbit through thehaloof thegalaxyaround thegalacCc core.Manyorbit in theoppositedirecCon(retrogrademoCon)tothegalacCcdisk.
TheOrbitsofGlobularClusters
Theorbitsofglobularclustersarelikelytobeintheformofaprecessingellipse.
RoseXeorbit
There are 17 globs lessthan 5000 ly from thegalacCc centre. If thecentralbulgeis5000lyinradius then these innerglobsareactuallypassingthroughthebulge.
DistribuConofGlobularClusters
There are 157MilkyWay globular clusters in the Catalog of ProfessorWilliamHarris, McMaster University, Canada. There are more candidates as yetunconfirmed.
ThediameteroftheMilkyWaygalaxyisabout100,000lightyears.TheSunisabout26,000lightyearsfromthegalacCccentreorabouthalfwayoutfromthecentreofthegalaxy.
There are roughly anequal number of globsabove and below thegalacCcdisk.
The average distance ofglobularclustersfromtheGalacCc Centre is about40,000lightyears.However, the median isonlyabout16,000ly.
98 globular clusters arewithin 25,000 ly of thegalacCccentre.
There are 13 globsfurtherthan100,000lightyears.
TheIntergalacCcWanderer
NGC2419wasdiscoveredbyWilliamHerschelin1788.
It is also known as the Intergalac/c Wanderer, a name given when it waserroneouslybelievednottobeinorbitabouttheMilkyWay.
NGC 2419 lies about 270,000 ly fromtheSun.NearlytwiceasfarastheLMC.At thisdistance, it takessome3billionyears to make one trip around thegalaxy.
This dense glob is very luminous andrankswithOmegaCentauriand47Tucinabsolutebrightness.
NGC2419.Credit:AdamBlock/MountLemmonSkyCenter/UniversityofArizona
SkySafariscreenclipfor9pmon15thMarch2016.NGC2419alCtude18degrees.
ObservingGlobularClusters
Ofthe157MilkyWayglobularclustersinWilliamHarris’cataloguehalf(79)arefoundtowardsthegalacCccentreinjust3constellaCons:
SagiXarius:35globularclusters.7Messier:M22,M28,M54,M55,M69,M70,M75.
Ophiuchus:25globularclusters.7Messier:M9,M10,M12,M14,M19,M62,M107.
Scorpius:19globularclusters.2Messier:M4,M80.
Thereare29Messierglobularclusters:M2,M3,M4,M5,M9,M10,M12,M13,M14,M15,M19,M22,M28,M30,M53,M54,M55,M56,M62,M68,M69,M70,M71,M72,M75,M79,M80,M92,M107.
SagiXariushas22globularclustersbrighterthanmagnitude10
NGC 6522 and NGC 6528 in SagiXarius areprobably the two globular clusters closest tothe GalacCc Centre as the closer posiCon ofDufay1(mag11.6)isnowinquesCon.
Thepairareseparatedbyonly16’andareonly710lightyearsapart.
GlobularCluster Galac3cLongitude
Galac3cLa3tude
DistancefromSun(ly)
DistancefromGalac3cCentre(ly)
Dufay1 357.44° 2.12° 26,700 1,600
NGC6522 1.02° -3.93° 25,100 2,000
NGC6528 1.14° -4.17° 25,800 2,000
UKS1 5.13° 0.76° 25,400 2,300
Terzan2 356.32° 2.3° 24,400 2,600
Liller1 354.84° -0.16° 26,700 2,600
GlobsNearesttotheGalacCcCentre
M69 and M70 are separated by2.5°andareonly1400lyapart.
M22 andNGC 6544 are separatedby6.7°andareonly1320lyapart!
Ophiuchushas18globularclustersbrighterthanmagnitude10.
M4andM80areinScorpius.
M10andM12areseparatedby3.3°andareonly1,560lyapart.
FromaplanetaroundastarnearM12,theglobularclusterM10wouldlooksixCmesbigger*intheskythantheEarth’sFullMoon.(*diameter).
Scorpiushas7globularclustersbrighterthanmagnitude10.
NGC6453hasmag10.08andisalsoshown.
Coincidently, NGC 6441 and NGC 6453 lie at the samedistancefromtheSun,separatedby2.5°and1,620lyapart.
TheEarth’sorbitabout theSun (EclipCcshown inblue) isCltedto theplaneofthegalaxyatabout60degrees.Thenormal(axisoforbit)isthereforeCltedtotheplaneofthegalaxyat30degrees.
The Earth’s axis is Clted away from the normal at 23.5 degrees and somewhattowardsthegalacCcplane.TheEarth’saxismakesanangleofabout27degreestotheplaneofthegalaxy.
TheEarth’saxiskeepsthesameorientaConinspaceastheEarthorbitstheSun.AstheEarthrotates,theNorthCelesCalPole(NCP)andSouthCelesCalPole(SCP)arefixedpointsinthesky(ignoringprecession).TheNCPhasgalacCccoordinates:longitude123°,laCtude+27°.TheSCPhasgalacCccoordinates:longitude303°,laCtude-27°.
NotethattheNCPfacesawayfromtheGalacCcCentrebuttheSCPfacesmoretowardstheGalacCcCentre.
Because theNCP faces away from theGalacCc Centre, there are only 27 globularclustersinthenorthernhemispherebut130inthesouthernhemisphere.
Only13northernglobularsarebrighterthanmagnitude10,comparedto81inthesouthernhemisphere.
Thereareactuallyonly8Messierglobsinthenorthernhemisphere: M3(CVn) M5(Ser)
M13(Her) M15(Peg)
M53(Com) M56(Lyr)
M71(Sge) M92(Her)}
21MessierglobsareinthesouthernhemispherebutnonearebelowDEC-33°.
M2(Aqr)istheclosestMessierglobtotheCelesCalEquatoratDEC-0.8°.
ThereareonlytwoMilkyWayglobsareaboveDEC+45°:
NGC6229(mag9.4)inHerculesatDEC+47.5°
Palomar1(mag13)inCepheusatDEC+79.6°.
Thereare25MilkyWayglobsbelowDEC-45degrees:
thelowestbeingIC4499(mag9.8)inApusatDEC-82°.
BrightestbyVisualMagnitudeThereare94globularclustersbrighterthanvisualmagnitude10.Allwithinrangeofan8inchtelescope.Thereare24brighterthanmagnitude7andviewablewithbinoculars.Onlytwoarereallynakedeye:OmegaCentauriand47Tuc.
YoumaybesurprisedtoknowthatNGC6752inPavoandNGC6397inAraareinthetop10.
Globular Cons VMag Globular Cons VMag
OmegaCen Cen 3.7 M55 Sgr 6.3 47Tuc Tuc 4.0 NGC362 Tuc 6.4 M22 Sgr 5.1 M92 Her 6.4 NGC6752 Pav 5.4 M62 Oph 6.5 M4 Sco 5.6 M2 Aqr 6.5 M5 Ser 5.7 M10 Oph 6.6 NGC6397 Ara 5.7 M12 Oph 6.7 M13 Her 5.8 NGC6388 Sco 6.7 M3 CVn 6.2 NGC3201 Vel 6.8 M15 Peg 6.2 M19 Oph 6.8 NGC2808 Car 6.2 M28 Sgr 6.8 NGC6541 CrA 6.3 NGC4833 Mus 6.9
Givenvisualmagnitudesforlargerobjects,includingglobularclusters,arerathererraCcandvaryfromsourcetosource.
ForOmegaCentauri:
Source Vmag
SIMBAD(AstronomicalDatabase) 5.33
NGC/ICProject 3.9
SkySafariPro 3.68
AtlasoftheUniversebyPatrickMoore 3.6
AtlasoftheNightSky(Massey&Quirk) 3.5
StephenO’Meara(TheCaldwellObjects)states:“Althoughmanysourcesshowitasbrightasmagnitude3.7or3.5,mynaked-eyeesCmateofmagnitude3.9isnotsoopCmisCc”.
Ifinditlaughablethatthevisualmagnitudecanbequotedtotwodecimalplaceswheninfactdifferentsourcescan’tevenagreeonthefirstdecimalplace!
AbsoluteMagnitudeandLuminosityTheabsolutemagnitudeofastariswhatitsapparentmagnitudewouldbeatastandarddistanceof10parsecs(32.6lightyears).Absolutemagnitudeallowstheintrinsicbrightnessofstarstobecompareddirectly.
Star Distance(ly) Vmag AbsMag
Sun 0.000016 -26.7 +4.83
Sirius 8.7 -1.44 +1.43
Vega 25 +0.02 +0.60
Aldebaran 67 +0.99 -0.57
Achernar 139 +0.54 -2.61
Canopus 309 -0.62 -5.50
Antares 550 +1.07 -5.07
Luminosityisthetotalamountofenergyradiatedbyastar(orsomeothercelesCalobject)perunitCme.Basically,thepoweroutputofthestar.Luminosity can be stated as so many Cmes brighter than the Sun and can becalculatedfromtheAbsMagbytheformula:
L=2.5124.83-AbsMagwhere2.512=Pogson’sraCo.
AbsoluteMagnitude LuminosityxSun
-10.17 1,000,000
-7.67 100,000
-5.17 10,000
-2.67 1,000
-0.17 100
+2.33 10
+4.83 1
+7.30 0.1
+9.80 0.01
MostLuminousGlobsLuminosity has been calculated off absolute magnitude, which in turn has beencalculatedoffdistanceandvisualmagnitude.
GlobCluster Con Distance VMag AbsMag Luminosity
OmegaCentauri Cen 17,000 3.7 -9.91 785,000
M54 Sgr 86,400 7.6 -9.52 548,000
47Tuc Tuc 14,700 4.0 -9.32 458,000
NGC2419 Lyn 269,300 10.4 -9.18 400,000
M15 Peg 33,900 6.2 -8.88 306,000
M3 CVn 33,300 6.2 -8.86 298,000
M2 Aqr 37,500 6.5 -8.83 292,000
M5 Ser 24,400 5.7 -8.72 263,000
NGC2808 Car 31,300 6.2 -8.71 261,000
M53 Com 58,400 7.6 -8.66 248,000
M13 Her 23,100 5.8 -8.47 209,000
NGC5824 Lup 104,600 9.1 -8.44 204,000
ClassificaConofGlobularClustersAClassificaConofGlobularClustersbyHarlowShapleyandHelenB.Sawyer1927.Globularclusterswereplacedin12classesonthebasisofapparentconcentraConofstars tocentre.Class1globsarehighlyconcentrated towardscentre,whilst class12globsappearfairlyhomogeneouswithliXlecentralconcentraCon.
Class1GlobularCluster Class12GlobularCluster
SimulaConshowinghowtheproporConofstarsshi\sgraduallyfromthecentreintothehalofromclasstoclass.Note:imagesmaynotexactlyreflectactualobservaCons.
Glob Class Table byHarlow Shapley andHelenB.Sawyer1927.
Totalof95globs.Asterisked (*) globs(usually bright) werechosen as beingrepresentaCve of theirclass.
The classes for someglobs were uncertain -indicatedbyacolon.
Daggered NGCs hadquesCons about theirstatusasglobs.
Shapely and Sawyer used photos of the clusters taken with the Bruce 24inchphotographic refractor at Arequipa in Peru (southern staConof theHarvard CollegeObservatory)toderivethefollowingdata.
Class 1 2 3 4 5 6 7 8 9 10 11 12
MeanVmag 8.7 7.5 6.8 8.6 7.4 8.4 8 8.2 8.8 8.9 9.4 9.6
Frequency 3 6 7 10 10 9 8 11 10 9 8 4
Theircomments…
“Thevariousclassesarewidelyspreadinapparentbrightnessanddiameteranddonot depend on integrated magnitude, except for a slight tendency of the leastcondensed clusters in themean to be faint. In apparent galacCc distribuCon theclassesarethoroughlymixed.
TheclassesofglobularclustersareprobablyanindicaConofdevelopmentalage.”
Class GlobularClusters
1 M75,NGC2808,NGC7006
2 M2,M80,NGC1851(Col),NGC2419(Lyn)
3 47Tuc,M54,NGC362(Tuc),NGC6388(Sco),NGC6541(CrA)
4 M15,M28,M62,M92
5 M5,M13,M30,M53,M69,M70,M79,NGC5286(Cen)
6 M3,NGC6752(Pav)
7 M10,M22
8 OmegaCentauri,M9,M14,M19,NGC4833(Lup)
9 M4,M12,M72,NGC6397
10 M56,M68,M107,NGC288(Scl),NGC3201(Vel)
11 M55,M71,NGC6352(Ara)
12 NGC4372(Mus)
Class2:M80(Scorpius).Credit:TheHubbleHeritageTeam(AURA/STScl/NASA)
Class4:M15(Pegasus).Credit:ESA/Hubble&NASA
Class6:M3.Credit:JimMisC(MisCMountainObservatory)
Class8:ωCentauri.Credit:GerryAarts(WSAAG)
Class10:M107(Ophiuchus).Credit:ESA/NASA
Class12:Palomar1(Cepheus).Credit:ESA/Hubble&NASA
MostofthedatausedforglobularclusterswastakenfromtheSIMBADdatabase,operatedatCDS,Strasbourg,Franceandfromthe…
CATALOGOFPARAMETERSFORMILKYWAYGLOBULARCLUSTERS:THEDATABASE
CompiledbyWilliamE.Harris,McMasterUniversityThisrevision:December2010
Exceptwhereotherwiseindicated(pages33and53),alltables,chartsanddiagramsinthispresentaConwerecreatedbyme.
Themapsof globular clusters in SagiXarius,OphiuchusandScorpiuswereploXed fromcomputerprogramscreatedbymeusingJ2000.0coordinatesofstarsandclustersfromSIMBAD.LabelsandotherinformaCononchartswereaddedusingEazyDrawonaMac.
ThecelesCal(RA,DEC)andgalacCcchartsforglobularclusterswereploXedfromcomputerprogramscreatedbymeusingequatorialandgalacCccoordinatesfromHarris’database.
SimulaConsforclassesandorbitsofglobularclusterswerealsoploXedfromcomputerprograms.
AllotherdiagramswerecreatedinEazyDraw.
RobHorvat(WSAAG)November2015