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 velocity (v) velocity
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 Absolute Brightness Absolute wavelengthswavelengths
••FortunatelyFortunately thethe brightestbrightest onesones declinedecline slowestslowest (magnitudes) (magnitudes) Absolute Brightness Absolute Absolute Brightness Absolute
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) Brightness Apparent Apparent Brightness (magnitudes) Brightness Apparent ••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 Distance modulus Distance
RedshiftRedshift (i.e.(i.e. velocity)velocity) RedshiftRedshift CosmologicalCosmological InverseInverse sq.sq. lawlaw 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) Brightness Apparent Apparent Brightness (magnitudes) Brightness Apparent ••JHKJHK areare infraredinfrared
Time (Modified Julian Days) colorcolor rangesranges possiblepossible expansionexpansion historieshistories GeometryGeometry ofof thethe universeuniverse
ClosedClosed
OpenOpen
FlatFlat StarStar warswars •Gravity vs. pressure. WhiteWhite dwarfsdwarfs
•A White Dwarf star is a dead star (i.e. no nuclear fusion), about as massive as the sun, but shrunk to the size of the Earth. •WDs are held up by the pressure from the mutual repulsion of their electrons WhiteWhite dwarfsdwarfs
A White Dwarf (WD) star exists in a so- called degenerate state of matter. WDs shrink when you add mass to them. NeutronNeutron starsstars
•A Neutron Star (NS) is a dead star (no fusion) as massive as the sun, but the size of a city. •NSs are held up by the pressure from the mutual repulsion of their neutrons PULsarsPULsars
•Pulsars are rapidly rotating neutron stars with radio or X-ray beams like lighthouses •Pulsars rotate with precise regularity that beats our best atomic clocks. QuarkQuark starsstars ??
•A Quark Star may be held up by the pressure from the mutual repulsion of its quarks StarStar warswars
Astrophysical Object Force Fighting Gravity People Electromagnetism Planets Electromagnetism Protostars Thermal Pressure (gravitational contraction) Main Sequence Stars Thermal Pressure (nuclear fusion) White Dwarfs electron degeneracy pressure Neutron Stars neutron degeneracy pressure Quark Stars quark pressure? Black Holes NOTHING! questionquestion #1#1 A Neutron Star has an average density of about 1014 g/cm3. A teaspoon has a volume of about 5 cm3. Assuming an average person weighs 50kg, which of the following has the most total mass? • The guest lecturer • A teaspoon of material from the sun’s core • A teaspoon of white dwarf material • A teaspoon of neutron star material • The mass of all six billion human beings on Earth TypeType II ii SupernovaeSupernovae Gravity Bombs! Gravitational Core Collapse of Massive Stars
•For stars with M > 8 Msun main sequence nuclear fusion results in an onion-like structure w/ an Iron core
•Star can’t get any more energy from fusing Iron Once the pressure support from fusion DEMODEMO disappears, the star’s core collapses, leading to a supernova as the outer layers fall in and rebound StellarStellar ExplosionExplosion MOVIEsMOVIEs
Core Collapse Supernova Movie
Gamma Ray Burst Movie LeftoverLeftover COMpactCOMpact objectsobjects
Type of Stellar Compact Explosion Remnant Type Ia NOTHING!
Failed Type Ia NEUTRON STAR? NEUTRON STAR Type II BLACK HOLE
Gamma-Ray Burst BLACK HOLE TheThe FriedmannFriedmann equationsequations SolutionsSolutions toto EinsteinEinstein’’ss FieldField EquationsEquations ofof GeneralGeneral Relativity,Relativity, whichwhich describedescribe anan expandingexpanding (or(or contracting)contracting) universe.universe.
Einstein introduced General Alexander George Relativity in 1915 but these Friedmann Lemaitre solutions were not found until 1888-1925 1894-1966 1922, by Friedmann