天体物理学报：LIGO引力波探测器释疑

LIGO:InitiatingtheAdvancedDetectorEraforGravitationalWaveAstrophysicsAlbertLazzariniDeputyDirector,LIGOLaboratoryCaliforniaInstituteofTechnologyOnbehalfoftheLIGOScientificCollaboration13October2014EasternForumofScienceandTechnology(EFST)Shanghai,ChinaCollidingBlackHolescourtesyofNCSA2OutlineTheLIGOmissionGravitationalwavesandtheirdetectionAstronomicalsourcesforLIGOTheAdvancedLIGOProjectProspectsforaglobalnetworkEFST,Shanghai,China13October2014LIGO-G1401149-v13LIGOAddressesFundamentalQuestionsinPhysicsandAstronomyLIGOLaboratoryistheworld’sleadingfacilityforconductinggravitational-wavescienceTheLIGOScientificCollaborationisthescientificorganizationthat,inconcertwiththeLIGOLaboratory,carriesoutLIGOscienceFundamentalPhysicsIsGeneralRelativitythecorrecttheoryofgravity?Wavepropagationspeed(delaysinarrivaltimeofbursts)Spincharacteroftheradiationfield(polarizationofradiationfromCWsources)Areblackholesreallycharacterizedbyonlymassandspin?Howdoesmatterbehaveunderextremeconditions?Astrophysics,Astronomy,CosmologyDocompactbinarymergerscauseGRBs?Whatisthesupernovamechanismincore-collapseofmassivestars?Howmanylowmassblackholesarethereintheuniverse?Dointermediatemassblackholesexist?Howbumpyareneutronstars?Canweobservepopulationsofweakgravitationalwavesources?Canbinaryinspiralsbeusedas“standardsirens”tomeasurethelocalHubbleparameter?LIGO-G1401149-v1EFST,Shanghai,China13Octonber2014Credit:LIGOScientificCollaborationImagecredit:W.BengerBlackHoleMergerandRingdownNeutronStarFormationImagecredit:NASAGWUpperlimitmapLIGO-G1401149-v14TheLIGOScientificCollaboration•~80groups,900+peopleworkingontechnologyforLIGOdetectorsandlookingattheLIGO/GEOdata.•JointlyoperatingwithVirgoCollaboration’sVirgodetectorEFST,Shanghai,China13October2014LIGO-G1401149-v1Learnmore:VisitTheSpecialTheoryofRelativity(1905)overthrewcommonsenseassumptionsaboutspaceandtimeFinitepropagationofinformation⟹ElectromagneticradiationTheGeneralTheoryofRelativityandtheoryofGravity(1916)Gravitydescribedasawarpageofspacetime,notaforceactingatadistanceFinitepropagationofinfluenceofgravity⟹GravitationalradiationEFST,Shanghai,China13October2014LIGO-G1401149-v16Existenceproof:PSR1913+16JosephTaylorRussellHulseAwarded1974NobelPrizeinPhysicsEFST,Shanghai,China13October2014LIGO-G1401149-v1forbitaltoday~0.000035Hz(35microHertz)forbital300,000,000yrs~100Hz(inLIGOband)17/secVerypreciseclock~8hr7GravitationalWavesGravitationalwavesarepropagatingdynamicfluctuationsinthecurvatureofspace-time(‘ripples’inspace-time)Physicalproperties:predictedtotravelatthespeedoflightalmosttransparenttomatterquadrupoleradiationLIGOtargets:astrophysicalobjectsmovingatspeedapproachingthespeedoflightGravitationalwaveamplitudesarestrains:Senseofscale:computedstrainfromabinaryneutronstarpairM=1.4M,r=5x1023m(15Mpc),Rsep=40km,forb≈380Hz,v/c~0.3LIGO-G1401149-v1EFST,Shanghai,China13October2014LIGO-G1401149-v18LIGOInterferometryLIGOusesenhancedMichelsoninterferometrysuspended(‘freelyfalling’)mirrorsPassingGWsstretchandcompressthedistancebetweentheendtestmassandthebeamsplitterTheinterferometeractsasatransducer,turningGWsintophotocurrentproportionaldifferentialarmlengthAcoherentstrain-amplitudedetectorAdvancedLIGO4kmh(f)=DLL(f)LIGO-G1401149-v1EFST,Shanghai,China13October20149TheLIGOLaboratorySitesCaltechMITLivingston,LAHanford,WAInterferometersarealignedalongthegreatcircleconnectingthesitesEFST,Shanghai,China13October2014LIGO-G1401149-v1JointlybuiltandoperatedfortheU.S.NationalScienceFoundationbyCaltechandMITunderaCooperativeAgreementHanford,WA-AdvancedLIGO:4kmAdvancedLIGO:4kminterferometer10S6–LastScienceRunofInitialLIGOEraS6endedwiththebestsensitivityinitialLIGOachieved:BeststraindataeverrecordedbyanyinstrumentintheworldBothH1andL1ranconsistentlyinthe18-20MpcrangeforNS+NSbinariesduringquiettimes(SNR=8for1.4M+1.4MNS/NSsystems)Maximumrangeobserved~21MpcRangedefinedasasky&source-orientationaveragedeffectivedistanceMaximumdistancetowhichasourcemaybedetected:Horizondistance--foronoptimallylocated&orientedsourceis~2.3Xgreater(45Mpc)EFST,Shanghai,China13October2014LIGO-G1401149-v111LIGOAstrophysicsFirstgenerationobservations:SciencerunsS1–S6Spanningtheepoch2002–2010Currentlyupgradinginterferometersto2ndgenerationadvanceddetectorsTodate,nodetectionshavebeenmade80+publicationsonupperlimitstodateSee:Afewhighlightsfollow…EFST,Shanghai,China13October2014LIGO-G1401149-v112BinaryCoalescencesS5/S6all-skyblindsearchTightestratelimitsfromLIGOObservationsInferredtheoreticalratesbasedonbinarypulsars,populationsynthesisRef:arXiv:1111.7314v4EFST,Shanghai,China13October2014LIGO-G1401149-v1Uncertainity:+/-2INEXPONENT!OptimisticratesLikelyratesPessimisticratesLIGOobservationalresultsStill~10Xfromoptimisticrates,~100XfromrealisticratesNeedtoawaitnextgenerationdetector–AdvancedLIGO13D~6500light-yearsYoungandrapidlyspinningdownSpinfrequencynEM=29.8HznGW=2nEM=59.6HzSpindowndueto:elec