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11/25/03 Prof. Lynn Cominsky 1
Class web site: Class web site: http://glast.sonoma.edu/~lynnc/courses/ahttp://glast.sonoma.edu/~lynnc/courses/a305305
Office: Darwin 329AOffice: Darwin 329A
(707) 664-2655(707) 664-2655
Best way to reach me: Best way to reach me: [email protected]@charmian.sonoma.edu
Astronomy 305/Frontiers in Astronomy 305/Frontiers in AstronomyAstronomy
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Golden Age of Cosmology IIGolden Age of Cosmology II What is the fate of the Universe?What is the fate of the Universe?
Observations of CMBR Observations of CMBR Hubble ExpansionHubble Expansion Supernovae and CosmologySupernovae and Cosmology Accelerating UniverseAccelerating Universe
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CMBR and cosmologyCMBR and cosmology
Take a trip in time/out in space to Take a trip in time/out in space to put "earliest light" in perspectiveput "earliest light" in perspective
movie
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Cosmic Background Cosmic Background ExplorerExplorer
3 instruments: FIRAS, DMR and DIRBE Cryogens ran out on 9/ 21/ 90 ending observations by FIRAS and longer wavelengths of DIRBE DMR and the shorter wavelengths of DIRBE operated until 11/23/93
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COBE data/DIRBECOBE data/DIRBE
Diffuse InfraRed Background Experiment IR background is produced by dust warmed by all the stars that have existed since the beginning of time Limit to energy produced by all stars in the Universe
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COBE data/FIRASCOBE data/FIRAS
Far InfraRed Absolute Spectrophotometer
11/25/03 Prof. Lynn Cominsky 9
COBE data/FIRASCOBE data/FIRAS
FIRAS results show that 99.994% of the radiant energy of the Universe was released within the first year after the Big Bang Data match the Big Bang predictions so exactly that the error bars are within the curve itself
Residuals from a 2.728 (+/- 0.004)
degree Kelvin blackbody
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COBE data/FIRASCOBE data/FIRAS
The CMBR is described by the most perfect The CMBR is described by the most perfect blackbody spectrum ever measuredblackbody spectrum ever measured
Blackbody spectra are produced when Blackbody spectra are produced when material is thick and dense, so that photons material is thick and dense, so that photons must scatter many times before they escapemust scatter many times before they escape
The photons must therefore have been The photons must therefore have been emitted from dark, thick matter at a much emitted from dark, thick matter at a much earlier timeearlier time
The CMBR energy was emitted when the The CMBR energy was emitted when the Universe was 10Universe was 1066 times smaller and hotter times smaller and hotter than it is now. Photons continued to scatter than it is now. Photons continued to scatter until the Universe was 10until the Universe was 10-3-3 its present size its present size
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Geometry Geometry
See how parallel laser light beams fired by the space slug are affected by the geometry of space
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(total)M
where
M = matter density (including regular and dark
matter)
tot = density/critical density
If tot = 1,Universe is flat, expansion coasts to a halt as Universe is critically balanced.
Old view: Density of the Old view: Density of the UniverseUniverse
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COBE DMRCOBE DMR
Differential Microwave Radiometer 3 different wavelengths 2 antennae for each wavelength, 7 degree beam Pointed 60 degrees apart
DMR work featured in George Smoot’s “Wrinkles in Time”
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COBE data/DMRCOBE data/DMR
Dipole due to movement of Solar System
warm
cool
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COBE data/DMRCOBE data/DMR
Fluctuations in CMB seen by DMR are at the level of one part in 100,000
Blue spots mean greater density
Red spots mean lesser density
(in the early Universe)
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CMBR FluctuationsCMBR Fluctuations
COBE measures the angular fluctuations COBE measures the angular fluctuations on large scales, down to about L=16on large scales, down to about L=16
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CMBR FluctuationsCMBR Fluctuations
Determining the spectrum of fluctuations Determining the spectrum of fluctuations in the CMBR can directly differentiate in the CMBR can directly differentiate between models of the Universebetween models of the Universe
Angular size of
fluctuation
How much power there is
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CMBR FluctuationsCMBR Fluctuations Current data favor a Current data favor a
peak near Lpeak near LEffEff = 210 = 210 This is consistent This is consistent
with the sCDM with the sCDM (standard Cold Dark (standard Cold Dark Matter) and Matter) and CDM CDM models (CDM + models (CDM + cosmological cosmological constant)constant)
Both describe a flat Both describe a flat ((=1) Universe=1) Universe
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CMBR FluctuationsCMBR Fluctuations
For a given For a given model (e.g., model (e.g., sCDM) the sCDM) the fluctuation fluctuation spectrum can spectrum can also be used also be used to directly to directly determine the determine the Hubble Hubble constantconstant
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BOOMERanGBOOMERanG
Balloon Observations Of Balloon Observations Of Millimeter Extragalactic Millimeter Extragalactic Radiation and GeophysicsRadiation and Geophysics
12 - 20 arc min resolution – 12 - 20 arc min resolution – about 35 times better than about 35 times better than COBECOBE
Two flights: 1998/99 (10 Two flights: 1998/99 (10 days) and 1999/00days) and 1999/00
Sensitive to temperature Sensitive to temperature differences as small as differences as small as 0.0001 degrees C0.0001 degrees C
Imaged 2.5% of entire skyImaged 2.5% of entire sky
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BOOMERanG vs. COBEBOOMERanG vs. COBE
1800 square degrees of sky
-300K +300 K
moon
Fluctuations Fluctuations were about 1 were about 1 degreedegree
0.85< 0.85< tottot <1.25 <1.25
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BOOMERanG ConclusionsBOOMERanG Conclusions Presence of large Presence of large
peak near peak near ll = 200 (1 = 200 (1 degree) confirms degree) confirms inflationary expansioninflationary expansion
Height of second peak Height of second peak at at ll = 600 determines = 600 determines relative amounts of relative amounts of baryonic (normal) and baryonic (normal) and non-baryonic (dark) non-baryonic (dark) mattermatter
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Cosmological Parameters - Cosmological Parameters - TOTTOT
The strong first peak at The strong first peak at ll =200 =200 confirms inflationary expansionconfirms inflationary expansion
Recall that inflation was proposed Recall that inflation was proposed in order to explain the apparent in order to explain the apparent flatness of the Universeflatness of the Universe
Another way to say this: Another way to say this: TOTTOT= 1.0 = 1.0 so we live in a critically balanced so we live in a critically balanced UniverseUniverse
However, to quote Rocky Kolb:However, to quote Rocky Kolb:
11/25/03 Prof. Lynn Cominsky 27
Wilkinson Microwave Anisotropy Wilkinson Microwave Anisotropy ProbeProbe
Selected by Selected by NASA in 1996NASA in 1996
Launched June Launched June 30, 2001 to L230, 2001 to L2
Has measured Has measured fluctuations in fluctuations in CMBR on a CMBR on a scale of 0.2 - 1 scale of 0.2 - 1 degrees (vs. 7degrees (vs. 7oo for COBE) and for COBE) and filled in the filled in the fluctuation plotfluctuation plot
Key results:
•Hubble constant is 71 km/sec/Mpc (to within 5%)
•Age of the Universe is 13.7 billion years old (to within 1%!)
• First stars appeared at t = 200 million years after the BB
• Universe is geometrically flat
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WMAP OrbitWMAP Orbit
L2 is one of the 3 L2 is one of the 3 semistable points semistable points in the Earth-Sun in the Earth-Sun binary systembinary system
Another body can Another body can orbit at this point orbit at this point at a fixed at a fixed distance from the distance from the Earth and the Sun Earth and the Sun with corrections with corrections every 23 daysevery 23 days
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Making the WMAPMaking the WMAP
All five WMAP frequency band All five WMAP frequency band maps combine to create the full-maps combine to create the full-sky CMB map.sky CMB map.
movie
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WMAP correctionsWMAP corrections
Removing the dipole caused by Removing the dipole caused by Earth’s motionEarth’s motion
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WMAP correctionsWMAP corrections
Removing the foreground signal Removing the foreground signal from our Galaxy to show the from our Galaxy to show the backgroundbackground
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Universe’s Baby PicturesUniverse’s Baby Pictures
Red is warmer
Blue is Blue is coolercooler
Credit: NASA/WMAP
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Compare to COBECompare to COBE
The WMAP image brings the COBE The WMAP image brings the COBE picture into sharp focus.picture into sharp focus.
movie
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Compare maps at other Compare maps at other wavelengthswavelengths
Visible to microwave galaxy imagesVisible to microwave galaxy images Compare the dynamic rangeCompare the dynamic range
movie
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WMAP cosmologyWMAP cosmology
Content of the Universe: Content of the Universe: 4% Atoms 4% Atoms 23% Cold Dark Matter 23% Cold Dark Matter 73% Dark energy73% Dark energy
Fast moving neutrinos do not play any Fast moving neutrinos do not play any major role in the evolution of structure in major role in the evolution of structure in the universe. They would have prevented the universe. They would have prevented the early clumping of gas in the universe, the early clumping of gas in the universe, delaying the emergence of the first stars, delaying the emergence of the first stars, in conflict with the new WMAP data.in conflict with the new WMAP data.
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WMAP supports inflationWMAP supports inflation
Inflation - a VERY rapid expansion in the Inflation - a VERY rapid expansion in the first 10first 10-35-35 s of the Universe – predicts: s of the Universe – predicts: That the density of the universe is close to the That the density of the universe is close to the
critical density, and thus the geometry of the critical density, and thus the geometry of the universe is flat. universe is flat.
That the fluctuations in the primordial density That the fluctuations in the primordial density in the early universe had the same amplitude in the early universe had the same amplitude on all physical scales. on all physical scales.
That there should be, on average, equal That there should be, on average, equal numbers of hot and cold spots in the numbers of hot and cold spots in the fluctuations of the cosmic microwave fluctuations of the cosmic microwave background temperature. background temperature.
WMAP sees a geometrically flat UniverseWMAP sees a geometrically flat Universe
11/25/03 Prof. Lynn Cominsky 39
PlanckPlanck ESA mission to be ESA mission to be
launched in 2007launched in 2007 Will measure entire Will measure entire
sky to 10’ to 2 parts sky to 10’ to 2 parts per millionper million
Will give better Will give better information than information than WMAP for LWMAP for Leffeff from from 600 to 2000600 to 2000
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Hubble ExpansionHubble Expansion
We have already seen how the galaxies We have already seen how the galaxies move away faster at further distancesmove away faster at further distances
We measured the slope of the velocity of We measured the slope of the velocity of the galaxies vs. their distances the galaxies vs. their distances Hubble Hubble constantconstant
But is the Hubble constant really constant? But is the Hubble constant really constant? In other words, has the expansion In other words, has the expansion
occurred at the same rate in the past as it occurred at the same rate in the past as it is right now, and will the future expansion is right now, and will the future expansion also be at this same rate?also be at this same rate?
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Measuring the Hubble ExpansionMeasuring the Hubble Expansion
If the expansion rate is constant, If the expansion rate is constant, distance between 2 galaxies follows distance between 2 galaxies follows yellow dotted line back in timeyellow dotted line back in time
If rate is speeding up, then the Universe is older than we thinkReal Big Bang Derived from constant
rate
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Distances to SupernovaeDistances to Supernovae Type Ia supernovae are Type Ia supernovae are “standard candles”“standard candles” Occur in a binary system in which a white Occur in a binary system in which a white
dwarf star accretes beyond the 1.4 Mdwarf star accretes beyond the 1.4 Moo Chandrasekhar limit and collapses and Chandrasekhar limit and collapses and explodesexplodes
Decay time of light curve is correlated to Decay time of light curve is correlated to absolute luminosityabsolute luminosity
Luminosity comes from the radioactive decay Luminosity comes from the radioactive decay of Cobalt and Nickel into Ironof Cobalt and Nickel into Iron
Some Type Ia supernovae are in galaxies with Some Type Ia supernovae are in galaxies with Cepheid variablesCepheid variables
Good to 20% as a distance measureGood to 20% as a distance measure
11/25/03 Prof. Lynn Cominsky 44
Supernovae as Standard Supernovae as Standard CandlesCandles
If you know the absolute If you know the absolute brightness of an object, you can brightness of an object, you can measure its apparent brightness measure its apparent brightness and then calculate its distanceand then calculate its distance
Fobs = Labs/4d2
11/25/03 Prof. Lynn Cominsky 45
Supernovae as Standard Supernovae as Standard CandlesCandles Here is a typical supernova lightcurve and Here is a typical supernova lightcurve and
its spectrumits spectrum
Compare two distances to see if Compare two distances to see if expansion rate has changedexpansion rate has changed
Measure shape of curve and peak distance
Measure redshift distance
11/25/03 Prof. Lynn Cominsky 46
Supernova Cosmology projectsSupernova Cosmology projects Two competing groupsTwo competing groups
Saul Perlmutter, Lawrence Berkeley LabSaul Perlmutter, Lawrence Berkeley Lab Brian Schmidt, AustraliaBrian Schmidt, Australia
Analyze lightcurves vs. redshifts for many Analyze lightcurves vs. redshifts for many Type 1a supernovae at redshifts <2Type 1a supernovae at redshifts <2
Expected to find the deceleration rate of Expected to find the deceleration rate of the Universe – that the expansion was the Universe – that the expansion was coasting to a slow haltcoasting to a slow halt
Instead found that the expansion seems to Instead found that the expansion seems to be accelerating!be accelerating!
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Cosmological parameters - Cosmological parameters -
Observations of over 80 SN (over several Observations of over 80 SN (over several years) have showed that they are dimmer years) have showed that they are dimmer than would be expected if the Universe was than would be expected if the Universe was expanding at a constant rate or slowing expanding at a constant rate or slowing down (as was previously thought)down (as was previously thought)
This means that some unknown “dark This means that some unknown “dark energy” is causing the Universe to fly apart energy” is causing the Universe to fly apart at ever-increasing speeds. at ever-increasing speeds.
The dark energy density/critical density =The dark energy density/critical density =
Current measurements: Current measurements: – – = = ~ ~ 0.650.65
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Accelerating UniverseAccelerating Universe
M = matter
= cosmological constant
0 0.2 10.80.60.4Redshift
11/25/03 Prof. Lynn Cominsky 49
Einstein and Dark EnergyEinstein and Dark Energy When Einstein first formulated his equations When Einstein first formulated his equations
of General Relativity, he believed in a static of General Relativity, he believed in a static Universe (or steady state Universe)Universe (or steady state Universe)
Since the equations seemed to predict an Since the equations seemed to predict an unstable universe that would either expand unstable universe that would either expand or contract, he “fixed” his equations by or contract, he “fixed” his equations by inserting a “Cosmological Constant” called inserting a “Cosmological Constant” called
When Hubble later found that the Universe When Hubble later found that the Universe was expanding, Einstein called the creation was expanding, Einstein called the creation of the Cosmological Constant his “greatest of the Cosmological Constant his “greatest blunder”blunder”
11/25/03 Prof. Lynn Cominsky 50
Einstein and Dark EnergyEinstein and Dark Energy
However, now we see that there is indeed a However, now we see that there is indeed a cosmological constant term – but it acts in cosmological constant term – but it acts in the opposite sense to Einstein’s original the opposite sense to Einstein’s original ideaidea
The Dark Energy implied by the non-zero The Dark Energy implied by the non-zero value of value of pushes the Universe apart even pushes the Universe apart even faster, rather than adding stability to an faster, rather than adding stability to an unstable Universe, as Einstein originally unstable Universe, as Einstein originally intended.intended.
There are many theories for Dark Energy: There are many theories for Dark Energy: vacuum fluctuations, extra dimensions, etc.vacuum fluctuations, extra dimensions, etc.
11/25/03 Prof. Lynn Cominsky 51
Best results from SN + CMBBest results from SN + CMB
Contours show best Contours show best fits from 2 SN fits from 2 SN groupsgroups
Blue region shows Blue region shows best fits from 2 best fits from 2 CMB groupsCMB groups
Intersection of Intersection of these two also these two also includes the most includes the most likely value for likely value for M M = = 0.30.3
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HST views Distant Supernovae HST views Distant Supernovae 1a1a HST found most HST found most
distant Type 1adistant Type 1a It was so far away It was so far away
that it occurred that it occurred during the period during the period when the when the expansion was still expansion was still slowing down due slowing down due to gravity from the to gravity from the galaxies in a galaxies in a smaller Universesmaller Universe
11/25/03 Prof. Lynn Cominsky 53
(total)M +
where
M = matter density (including
regular and dark matter)
= cosmological constant or
dark energy density
tot = density/critical density
New view: Density of the New view: Density of the UniverseUniverse
Perlmutter et al.
40 supernovae
SN data
11/25/03 Prof. Lynn Cominsky 54
SNAPSNAP – SuperNova Acceleration – SuperNova Acceleration ProbeProbe
SNAP would be a space-SNAP would be a space-based mission with a 2-based mission with a 2-m optical telescope, 1m optical telescope, 1oo square field-of-view and square field-of-view and a 10a 1066 pixel CCD detector pixel CCD detector
It would be able to find It would be able to find 2000 SN per year – thus 2000 SN per year – thus getting enough data to getting enough data to measure properties of measure properties of dark matter, dark dark matter, dark energy and cosmological energy and cosmological parametersparameters
11/25/03 Prof. Lynn Cominsky 55
SNAPSNAP – SuperNova Acceleration – SuperNova Acceleration ProbeProbe
Expected Expected statistical statistical uncertainty region uncertainty region from SNAP from SNAP observationsobservations
Arrow points to Arrow points to best value for best value for MM
Solid blue line is Solid blue line is flat Universe from flat Universe from CMB CMB measurementsmeasurements
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Today’s CosmologyToday’s Cosmology = 1.0 from CMBR measurements. We = 1.0 from CMBR measurements. We
live in a flat Universe.live in a flat Universe. <0.3 from extensive observations at <0.3 from extensive observations at
various wavelengths. Includes dark matter various wavelengths. Includes dark matter as well as normal matter and light. as well as normal matter and light.
> 0.6 from Type 1a SN observations. > 0.6 from Type 1a SN observations. Many different theories for “dark energy.” Many different theories for “dark energy.” Universe accelerates even though it is flat.Universe accelerates even though it is flat.
Hubble constant = 70 km/sec/Mpc from Hubble constant = 70 km/sec/Mpc from HST observations. Age of Universe is HST observations. Age of Universe is around 13.7 billion years.around 13.7 billion years.
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Web ResourcesWeb Resources
Ned Wright’s CMBR pages http://www.astro.ucla.edu/~wright/CMB-DT.html
Ned Wright’s Cosmology Tutorial http://www.astro.ucla.edu/~wright/cosmolog.htm
BOOMERanG http://www.physics.ucsb.edu/~boomerang/
MAP mission http://map.gsfc.nasa.gov
Planck mission http://sci.esa.int/home/planck/index.cfm
http://astro.estec.esa.nl/SA-general/Projects/Planck/
SNAP mission http://snap.lbl.gov/
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Web ResourcesWeb Resources
Brian Schmidt’s Supernova PagesBrian Schmidt’s Supernova Pages http://msowww.anu.edu.au/~brian/PUBLIC/public.htmlhttp://msowww.anu.edu.au/~brian/PUBLIC/public.html
Hubble Space Telescope sees Distant SupernovaHubble Space Telescope sees Distant Supernova http://oposite.stsci.edu/pubinfo/pr/2001/09/pr.htmlhttp://oposite.stsci.edu/pubinfo/pr/2001/09/pr.html
Saul Perlmutter’s Group Supernova Pages Saul Perlmutter’s Group Supernova Pages http://panisse.lbl.gov/http://panisse.lbl.gov/
MAP Teacher’s Guide by Lindsay Clark MAP Teacher’s Guide by Lindsay Clark http://www.astro.princeton.edu/~clark/teachersguide.htmlhttp://www.astro.princeton.edu/~clark/teachersguide.html
George Smoot’s group pages http://aether.lbl.gov/