天空望远镜新闻说明15h 10m 67ursa小矮人20u sky amp telescope.pdfVIP

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ADwarfGalaxy’sSimplePast

DwarfgalaxiesmayhemoststudybyPamelaL.Gay(Universityof

commongalaxiesintheuniverse,butTexas)indicatesthatthisfaintMilky

theydon’tusuallycapturethlic’sWayneighborexperiencedonlyasingle

imagination.Unliketheirmoremassivestar-formingeventearlyinitistence.

cousins,whichcansustainspiraldensityWhileitprobablyhadenoughgasto

wavesandinteractgravitationallywithsustainthisinitialburstofstellarbirth-

companions,resultinginburstsofstaring,subsequentstellarwindsandsuper-

formation,mostdwarfsaredestinedtonovaexplosionsdissipatedallthelight-

leadquieter,more“normal”lives.weightgalaxy’sremainingrawmaterials.

SuchisthecasefortheUrsaMinorGay’sfindings,presentedatJanuary’sURSAMINOR

dwarfspheroidalgalaxy(UGC9749).AmeetingoftheAmericanAstronomical

Above:Thiscomposite-color,visible-lightCCDimageofthehard-to-seeUrsaMinordwarfspheroidalgalaxywasobtainedbyPamelaGaywith

McDonaldObservatory’s30-inch(0.75-meter)reflector.Thisgalaxylies230,000light-yearsawayandissituatedatrightascension15h9.2m,decli-

nation+67°13(epoch2000.0).Northisupandeasttotheleftinthis46-widefield.ThechartisadaptedfromtheMillenniumStarAtlas.

20June1999SkyTelescope

Society,suggestthatthegalaxyhad“one

epochofstarformation,thennothing.”

Gaycametoherconclusioninanin-

directbutcompellingway.Shesurveyed

81variablestarsintheUrsaMinor

dwarf,identifying64RRLyraeand7

anomalousCepheidpulsators.Byaccu-

ratelytrackingthesestars’brightnessva-

riations,Gayconfirmedearlierhintsthat

thegalaxy’soverall