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1、Aninternationalteamofastronomersl,ledresearchersfromtheUniversityofCambridgeandtheAustralianNationalUniversity,haveidentifiedsomeoftheoldeststarsinourgalaxy2,whichcouldcontainvitalcluesabouttheearlyUniverse,includinganindicationofhowthefirststarsdied.Thesestars,whichhavebeenatth
2、everycentreoftheMilky3Wayforbillionsofyears,containextremelylowamountsofmetal:oneofthestarsisthemostmetal-poorstaryetdiscoveredinthecentreofourgalaxy.Thestarsalsocontainchemicalfingerprints4whichindicatethattheearlieststarsmayhavediedinspectaculardeathsknownashypernovae,whichwer
3、etentimesmoreenergeticthanaregularsupernova.Thefindings,reportedtoday(11November)inthejournalNature,couldaidinunderstandingjusthowmuchtheUniversehaschangedoverthepast13.7billionyears.Fordecades,astronomershavebeentryingtodeterminewhattheUniversewaslikesoonaftertheBigBang-underst
4、andinghowthefirststarsandgalaxies5formediscrucialtothisgoal.Whilesomeastronomersarelookingoutwardtogalaxiesbillionsoflightyearsawaytountanglethismystery,othersarelookinginwardtothecentreofourgalaxy.Ifyou'veeverlookedupatthenightskyfromadarkplaceyoumightseethecentreoftheMilkyWay.
5、Therearebillionsofstarsinourgalaxy,andastronomersareinterestedinpickingouttheoldeststarsandfindingoutabouttheirchemicalcompositionandmovements.SoonaftertheBigBang,theUniversewasentirely6madeupofonlyhydrogen,heliumandsmallamountsoflithium.Alloftheotherelements,liketheoxygenwebrea
6、theorthesodium7inourtoothpaste,havebeenmadeinsidestarsorwhentheydieassupernovae.Thishasledastronomerstosearchforextremelymetal-poorstars:starswithlotsofhydrogen,butverylittleofanyotherelement.Ithadbeenthoughtthattheveryfirststarsformedinthecentreofthegalaxy,wheretheeffectsofgrav
7、ityarestrongest.Butafterdecadesofsearches,astronomersfoundthatmoststarsinthecentreofourgalaxyhaveasimilarmetalcontentofthosemuchclosertous.WhilethestarsatthecentreofthegalaxyareaboutsevenbillionyearsolderthantheSun,they'restillnotoldenoughtounderstandwhattheconditionswerelikeint
8、heearlyUniverse.UsingtelescopesinAustraliaandCh