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Measuring the Expansion and Acceleration of the Universe MeasuringMeasuring thethe ExpansionExpansion andand AccelerationAcceleration ofof thethe UniverseUniverse withwith SupernovaeSupernovae andand Gamma-RayGamma-Ray BurstsBursts AndrewAndrew FriedmanFriedman Department of Astronomy, Harvard University TA ’02 Ojai California, July 3, 2006 OO uu tt ll II nn ee • Measuring Distances in Astronomy • Einstein, Hubble, and the Expansion of the Universe • Type Ia Supernovae and the Acceleration of the Expansion of the Universe. • My Research: Developing New Distance Measurement Methods Type Ia Supernovae at Infrared Wavelengths Gamma-Ray Bursts (GRBs) DistancesDistances inin astronomyastronomy InverseInverse squaresquare lawlaw FF == fluxflux (or(or brightness)brightness) LL == luminosityluminosity (or(or power)power) dd == distancedistance StandardStandard candlescandles AA StandardStandard CandleCandle isis aa theoreticaltheoretical astronomicalastronomical objectobject ofof knownknown intrinsicintrinsic luminosityluminosity LL,, likelike aa 100100 WattWatt lightlight bulbbulb inin spacespace OO uu tt ll II nn ee • Measuring Distances in Astronomy • Einstein, Hubble, and the Expansion of the Universe • Type Ia Supernovae and the Acceleration of the Expansion of the Universe • My Research: Developing New Distance Measurement Methods Type Ia Supernovae at Infrared Wavelengths Gamma-Ray Bursts TheThe sizesize ofof thethe KnownKnown universeuniverse inin 19151915 TheThe cosmologicalcosmological constantconstant The Cosmological Constant Cosmic Anti-Gravity Term ••In 1917, Einstein introduced the cosmological constant to allow for a static universe, the favored theory of the time. “That term [the cosmological constant] is necessary only for the purpose of making possible a quasi-static distribution of matter, as required by the fact of the small velocities of the stars.” (Einstein, 1917) EdwinEdwin HubbleHubble Edwin Hubble 1889-1953 Measuring the velocities and Hubble Space distances of The 100 inch Telescope “spiral- Hooker telescope at the 1990 – ???? nebulae” Mt. Wilson Observatory RedshiftRedshift CepheidCepheid variablevariable starsstars HubbleHubble’’ss DiagramDiagram (1929)(1929) v=v= HoHo xx dd velocity (v) velocity (v) distancedistance (d)(d) Most galaxies are redshifted (moving away) The more distant ones move faster. Ho = Hubble Constant. To=1/Ho ~age of universe EinsteinEinstein’’ss biggestbiggest blunder?blunder? ••IfIf EinsteinEinstein hadnhadn’’tt beenbeen soso insistentinsistent onon aa staticstatic universe,universe, hehe couldcould havehave predictedpredicted thethe expansionexpansion ofof thethe universeuniverse yearsyears beforebefore HubbleHubble’’ss 19291929 discovery.discovery. “Much later, when I was discussing cosmological problems with Einstein, he remarked that the introduction of the cosmological term was the biggest blunder of his life.” -George Gamow, My World Line, 1970 OO uu tt ll II nn ee • Measuring Distances in Astronomy • Einstein, Hubble, and the Expansion of the Universe • Type Ia Supernovae and the Acceleration of the Expansion of the Universe • My Research: Developing New Distance Measurement Methods Type Ia Supernovae at Infrared Wavelengths Gamma-Ray Bursts SupernovaSupernova A single exploding star can outshines an entire galaxy! SN 1999bh – Katzmann Automated Imaging SN 1994d – Hubble Space Telescope Telescope & Andy TypeType IaIa SupernovaESupernovaE Thermonuclear Bombs in Space! Explosions of White Dwarfs in Binary Systems WD Accretion From Main Merger of 2 White Dwarfs Sequence Companion If the total mass of the WD system exceeds ~1.4 Msun (the Chandrasekhar mass), it goes supernova TypeType IaIa lightlight curvescurves ••TheThe peakpeak absoluteabsolute brightnessbrightness (or(or luminosityluminosity LL)) ofof aa TypeType IaIa supernovasupernova isis roughlyroughly constantconstant fromfrom eventevent toto eventevent ••IfIf wewe measuremeasure thethe apparentapparent brightnessbrightness (or(or fluxflux FF),), wewe cancan inferinfer thethe distancedistance dd ifif wewe somehowsomehow knowknow LL TheThe RiseRise andand FallFall ofof AphroditeAphrodite NovAugOctSeptOctNovOct 5 17 3031201 1012522 Courtesy:Courtesy: RobertRobert P.P. KirshnerKirshner TypeType IaIa StandardizableStandardizable candlescandles ••TypeType IaIa SNeSNe areare notnot perfectperfect standardstandard candlescandles atat opticaloptical (magnitudes) (magnitudes) Absolute Brightness Absolute Brightness wavelengthswavelengths ••FortunatelyFortunately thethe brightestbrightest onesones declinedecline slowestslowest (magnitudes) (magnitudes) Absolute Brightness Absolute Brightness Time (Days) TheThe universeuniverse asas aa timetime machinemachine ••TheThe speedspeed ofof lightlight isis finite.finite. ••ObjectsObjects atat differentdifferent distancesdistances givegive usus snapshotssnapshots ofof thethe universeuniverse atat thethe timetime thatthat thethe lightlight left.left. ••TheThe redshiftredshift tellstells usus howhow muchmuch thethe universeuniverse hashas expandedexpanded inin thatthat time.time. ••IfIf wewe measuremeasure thethe redshiftredshift andand distancedistance forfor thatthat snapshot,snapshot, wewe cancan reconstructreconstruct aa moviemovie ofof thethe expansionexpansion forfor eacheach epochepoch inin cosmiccosmic history.history. possiblepossible expansionexpansion historieshistories TheThe acceleratingaccelerating universeuniverse Modern The unexpected Hubble 1998 discovery by Diagram 2 independent teams, the High-z SN Search Team (HZT) and the Hubble’s Supernova Cosmology Project (SCP). only the HZT results are shown here TheThe acceleratingaccelerating universeuniverse ReturnReturn ofof thethe cosmologicalcosmological DarkDark EnergyEnergy constant?constant? OO uu tt ll II nn ee • Measuring Distances in Astronomy • Einstein, Hubble, and the Expansion of the Universe • Type Ia Supernovae and the Acceleration of the Expansion of the Universe • My Research: Developing New Distance Measurement Methods Type Ia Supernovae at Infrared Wavelengths Gamma-Ray Bursts TypeType IaIa lightlight curvescurves ••WeWe observeobserve thethe SNSN throughthrough differentdifferent filtersfilters thatthat onlyonly letlet throughthrough colorscolors inin somesome range.range. ••UBVRIUBVRI areare namesnames forfor colorcolor rangesranges atat opticaloptical wavelengthswavelengths Apparent Brightness (magnitudes) Apparent Brightness (magnitudes) ••JHKJHK areare infraredinfrared Time (Modified Julian Days) colorcolor rangesranges InfraredInfrared TypeType IaIa SupernovaeSupernovae TypeType IaIa SupernovaeSupernovae maymay bebe betterbetter standardstandard candlescandles atat infraredinfrared wavelengthswavelengths vs.vs. opticaloptical wavelengths.wavelengths. Krisciunas et. al 2005 P A I R I T E L TheThe PPeterseters AAutomatedutomated IInfranfraRReded IImagingmaging TELTELescopeescope www.pairitel.org MountMount Hopkins,Hopkins, ArizonaArizona Infrared Type Ia Light Curves Gamma-rayGamma-ray burstsbursts ((GRBsGRBs)) The Brightest Explosions in the Universe! Long GRBs - Related to core Short GRBs – Probably collapse Supernovae of Merging Neutron Stars Some Massive Stars A short-lived accretion disk forms around newly formed black hole. High velocity jets produced which emit paired beams of gamma-rays. GRBGRB EnergeticsEnergetics The isotropic equivalent The beaming corrected gamma-ray energy Eiso is gamma-ray energy E is a a bad standard candle better standard candle Data from: Friedman & Bloom 2005 GrbGrb standardizedstandardized candlescandles Y-axis: Ep The peak energy at Friedman & Bloom 2005 which most of the gamma-ray light is emitted (this is like the dominant gamma-ray color of the GRB) X-axis: E The total energy emitted in gamma rays, corrected for beaming (this is related to the intrinsic luminosity of the GRB) GrbGrb HubbleHubble diagramdiagram Ep and E E Friedman & Bloom 2005 NasaNasa swiftswift satellitesatellite Sky & Telescope, Aug 2006 100100 billionbillion yearsyears ofof solitudesolitude TheThe FriedmannFriedmann equationsequations SolutionsSolutions toto EinsteinEinstein’’ss FieldField EquationsEquations ofof GeneralGeneral Relativity,Relativity, whichwhich describedescribe anan expandingexpanding (or(or contracting)contracting) universe.universe. EinsteinEinstein introducedintroduced GeneralGeneral RelativityRelativity inin 19151915 butbut thesethese Alexander solutionssolutions werewere notnot foundfound Friedmann untiluntil 1922,1922, byby FriedmannFriedmann 1888-1925 ModernModern HubbleHubble DiagramDiagram velocity velocity Hubble’s original Jha et al. 2006 in prep. diagram distancedistance AA universeuniverse ofof galaxiesgalaxies HISTORICALHISTORICAL SUPERNOVAESUPERNOVAE Year Report Status Identification in doubt 185AD China (Chin and Huang 1994) 386 China unknown 393 China unknown 1006 China, Japan, Korea, Arab lands, Europe Identified with radio SNR 1054 China, Japan Crab Nebula Possible identification 1181 China, Japan with radio SNR 3C58 1572 Europe (Tycho Brahe), China, Japan Tycho's remnant 1604 Europe (Kepler), China, Japan, Korea Kepler's remnant 1987 SN 1987A – southern hemisphere Large Magellanic Cloud EinsteinEinstein’’ss theorytheory ofof gravitygravity EinsteinEinstein’’ss FieldField EquationEquation The curvature of The matter energy space-time content of space- time ••Matter and Energy tell space and time how to curve. ••The curvature of space and time tells matter and energy how to move. ••In general relativity, gravity is curved space-time! HighHigh redshiftredshift HubbleHubble diagramdiagram Distance modulus Distance
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