supermassive black holes - alexander von … · 1) all galaxy bulges contain supermassive black...

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  • SUPERMASSIVE BLACK HOLES

  • TheFrenchmathematicianLaplacefirstspeculatedabouttheexistenceofanobjectsocompactthattheescapespeedwouldbegreaterthanthespeedoflight.

    ThefirstrelativisticcalculationwasperformedbyKarlSchwarzschild(1916),shortlyafterEinsteinpublishedhistheory.

    Rhorizon=2GM/c2

    BLACKHOLES

  • In1939,J.RobertOppenheimerandH.Snyder(agraduatestudent)describedamechanismbywhichblackholesmaybecreatedintherealUniverse.Astarthathasexhaustedallitsnuclearfuelcannolongersupportitselfagainstgravity.Astarwhoseremnantcoreexceedsacriticallimitfollowingasupernovaexplosionwillformablackhole.

  • MorethantwodozenstellarblackholecandidateshavebeenindentifiedintheMilkyWay,allofthempartofbinarysystemsinwhichtheothercomponentisavisiblestar.Theyhavehighlyvariablexrayemission,thoughttobecomingfromanaccretiondisksurroundingtheblackhole.

  • TheSupermassiveBlackHoleattheCentreoftheMilkyWay

  • EvidenceforSupermassiveBlackHolesinOtherGalaxies

  • Revolutionininourunderstandingofgalaxyformation:1)Allgalaxybulgescontainsupermassiveblackholes2)Themassoftheblackholeistightlycorrelatedwiththemassofthebulge.

  • Standard paradigm for structure formation in the Universe

  • STRUCTUREFORMSHIERARCHICALLY

  • Galaxiesarebelievedtoformthroughtwoprocesses:gasaccretionandmerging

  • Whathappenswhenablackholeaccretesnewmaterial?

  • Quasars(quasistellarobjects)haveapparentbrightnessescomparabletostarsinourgalaxy,yettheyareatcosmologicaldistances.

    Onlypossiblesourceofenergy:accretiondiskssurroundingsupermassiveblackholes.Frictionalheatinginthediskcanconvert10%oftherestmassenergyontheinfallingmaterialintoradiation.

  • SpectrumofaQuasar

  • OnlyaftertheadventoftheHubbleSpaceTelescope,diditbecomeclearthatquasarsresidewithingalaxies.Manyshowdisturbedmorphologies.

  • Thenumberdensityofquasarshasevolvedverystronglyasfunctionofcosmologicaltime...therewasanepochwhenaccretionontoblackholeswasatamaximum.

  • Mergersbetweengalaxiesarealsowelldocumented

    Anewfrontierinastrophysics:whathappenswhentheblackholesinthesegalaxiesmerge?