11/25/03Prof. Lynn Cominsky1 Class web site: Office: Darwin 329A (707) Best way to reach me: Astronomy 305/Frontiers in Astronomy

11/25/03Prof. Lynn Cominsky2 Group 13

11/25/03Prof. Lynn Cominsky3 Golden 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 Expansion Hubble Expansion Supernovae and Cosmology Supernovae and Cosmology Accelerating Universe Accelerating Universe

11/25/03Prof. Lynn Cominsky4 Big Bang Timeline We are here Today’s lecture

11/25/03Prof. Lynn Cominsky5 CMBR and cosmology Take a trip in time/out in space to put "earliest light" in perspective Take a trip in time/out in space to put "earliest light" in perspective movie

11/25/03Prof. Lynn Cominsky6 Cosmic Background Explorer  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

11/25/03Prof. Lynn Cominsky7 COBE 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

11/25/03Prof. Lynn Cominsky8 COBE data/FIRAS  Far InfraRed Absolute Spectrophotometer

11/25/03Prof. Lynn Cominsky9 COBE data/FIRAS  FIRAS results show that % 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 (+/ ) degree Kelvin blackbody

11/25/03Prof. Lynn Cominsky10 COBE data/FIRAS The CMBR is described by the most perfect blackbody spectrum ever measured The CMBR is described by the most perfect blackbody spectrum ever measured Blackbody spectra are produced when material is thick and dense, so that photons must scatter many times before they escape Blackbody spectra are produced when material is thick and dense, so that photons must scatter many times before they escape The photons must therefore have been emitted from dark, thick matter at a much earlier time The photons must therefore have been emitted from dark, thick matter at a much earlier time The CMBR energy was emitted when the Universe was 10 6 times smaller and hotter than it is now. Photons continued to scatter until the Universe was its present size The CMBR energy was emitted when the Universe was 10 6 times smaller and hotter than it is now. Photons continued to scatter until the Universe was its present size

11/25/03Prof. Lynn Cominsky11 Geometry See how parallel laser light beams fired by the space slug are affected by the geometry of space

11/25/03Prof. Lynn Cominsky12  (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 Universe

11/25/03Prof. Lynn Cominsky13 COBE 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”

11/25/03Prof. Lynn Cominsky14 COBE data/DMR  Dipole due to movement of Solar System warm cool

11/25/03Prof. Lynn Cominsky15 COBE data/DMR  Dipole removed to show “wrinkles”

11/25/03Prof. Lynn Cominsky16 COBE 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)

11/25/03Prof. Lynn Cominsky17 CMBR Fluctuations COBE measures the angular fluctuations on large scales, down to about L=16 COBE measures the angular fluctuations on large scales, down to about L=16

11/25/03Prof. Lynn Cominsky18 CMBR Fluctuations Determining the spectrum of fluctuations in the CMBR can directly differentiate between models of the Universe Determining the spectrum of fluctuations in the CMBR can directly differentiate between models of the Universe Angular size of fluctuation How much power there is

11/25/03Prof. Lynn Cominsky19 Fluctuations and geometry

11/25/03Prof. Lynn Cominsky20 CMBR Fluctuations Current data favor a peak near L Eff = 210 Current data favor a peak near L Eff = 210 This is consistent with the sCDM (standard Cold Dark Matter) and  CDM models (CDM + cosmological constant) This is consistent with the sCDM (standard Cold Dark Matter) and  CDM models (CDM + cosmological constant) Both describe a flat (  =1) Universe Both describe a flat (  =1) Universe

11/25/03Prof. Lynn Cominsky21 CMBR Fluctuations For a given model (e.g., sCDM) the fluctuation spectrum can also be used to directly determine the Hubble constant For a given model (e.g., sCDM) the fluctuation spectrum can also be used to directly determine the Hubble constant

11/25/03Prof. Lynn Cominsky22 BOOMERanG Photos from previous flight in Antarctica

11/25/03Prof. Lynn Cominsky23 BOOMERanG Balloon Observations Of Millimeter Extragalactic Radiation and Geophysics Balloon Observations Of Millimeter Extragalactic Radiation and Geophysics arc min resolution – about 35 times better than COBE arc min resolution – about 35 times better than COBE Two flights: 1998/99 (10 days) and 1999/00 Two flights: 1998/99 (10 days) and 1999/00 Sensitive to temperature differences as small as degrees C Sensitive to temperature differences as small as degrees C Imaged 2.5% of entire sky Imaged 2.5% of entire sky

11/25/03Prof. Lynn Cominsky24 BOOMERanG vs. COBE 1800 square degrees of sky -300  K +300  K moon  Fluctuations were about 1 degree  0.85<  tot <1.25

11/25/03Prof. Lynn Cominsky25 BOOMERanG Conclusions Presence of large peak near l = 200 (1 degree) confirms inflationary expansion Presence of large peak near l = 200 (1 degree) confirms inflationary expansion Height of second peak at l = 600 determines relative amounts of baryonic (normal) and non-baryonic (dark) matter Height of second peak at l = 600 determines relative amounts of baryonic (normal) and non-baryonic (dark) matter

11/25/03Prof. Lynn Cominsky26 Cosmological Parameters -  TOT The strong first peak at l =200 confirms inflationary expansion The strong first peak at l =200 confirms inflationary expansion Recall that inflation was proposed in order to explain the apparent flatness of the Universe Recall that inflation was proposed in order to explain the apparent flatness of the Universe Another way to say this:  TOT  = 1.0 so we live in a critically balanced Universe Another way to say this:  TOT  = 1.0 so we live in a critically balanced Universe However, to quote Rocky Kolb: However, to quote Rocky Kolb:

11/25/03Prof. Lynn Cominsky27 Wilkinson Microwave Anisotropy Probe Selected by NASA in 1996 Selected by NASA in 1996 Launched June 30, 2001 to L2 Launched June 30, 2001 to L2 Has measured fluctuations in CMBR on a scale of degrees (vs. 7 o for COBE) and filled in the fluctuation plot Has measured fluctuations in CMBR on a scale of degrees (vs. 7 o for COBE) and filled in the fluctuation 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

11/25/03Prof. Lynn Cominsky28 WMAP Orbit L2 is one of the 3 semistable points in the Earth-Sun binary system L2 is one of the 3 semistable points in the Earth-Sun binary system Another body can orbit at this point at a fixed distance from the Earth and the Sun with corrections every 23 days Another body can orbit at this point at a fixed distance from the Earth and the Sun with corrections every 23 days

11/25/03Prof. Lynn Cominsky29 WMAP

11/25/03Prof. Lynn Cominsky30 Making the WMAP All five WMAP frequency band maps combine to create the full-sky CMB map. All five WMAP frequency band maps combine to create the full-sky CMB map. movie

11/25/03Prof. Lynn Cominsky31 WMAP corrections Removing the dipole caused by Earth’s motion Removing the dipole caused by Earth’s motion

11/25/03Prof. Lynn Cominsky32 WMAP corrections Removing the foreground signal from our Galaxy to show the background Removing the foreground signal from our Galaxy to show the background

11/25/03Prof. Lynn Cominsky33 Universe’s Baby Pictures Red is warmer Blue is cooler Credit: NASA/WMAP

11/25/03Prof. Lynn Cominsky34 Compare to COBE The WMAP image brings the COBE picture into sharp focus. The WMAP image brings the COBE picture into sharp focus. movie

11/25/03Prof. Lynn Cominsky35 Compare maps at other wavelengths Visible to microwave galaxy images Visible to microwave galaxy images Compare the dynamic range Compare the dynamic range movie

11/25/03Prof. Lynn Cominsky36 WMAP cosmology Content of the Universe: Content of the Universe: 4% Atoms 4% Atoms 23% Cold Dark Matter 23% Cold Dark Matter 73% Dark energy 73% Dark energy Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data. Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data.

11/25/03Prof. Lynn Cominsky37 WMAP supports inflation Inflation - a VERY rapid expansion in the first s of the Universe – predicts: Inflation - a VERY rapid expansion in the first s of the Universe – predicts: That the density of the universe is close to the critical density, and thus the geometry of the universe is flat. That the density of the universe is close to the critical density, and thus the geometry of the universe is flat.geometry That the fluctuations in the primordial density in the early universe had the same amplitude on all physical scales. That the fluctuations in the primordial density in the early universe had the same amplitude on all physical scales.fluctuations That there should be, on average, equal numbers of hot and cold spots in the fluctuations of the cosmic microwave background temperature. That there should be, on average, equal numbers of hot and cold spots in the fluctuations of the cosmic microwave background temperature. WMAP sees a geometrically flat Universe WMAP sees a geometrically flat Universe

11/25/03Prof. Lynn Cominsky38 WMAP angular power spectrum

11/25/03Prof. Lynn Cominsky39 Planck ESA mission to be launched in 2007 ESA mission to be launched in 2007 Will measure entire sky to 10’ to 2 parts per million Will measure entire sky to 10’ to 2 parts per million Will give better information than WMAP for L eff from 600 to 2000 Will give better information than WMAP for L eff from 600 to 2000

11/25/03Prof. Lynn Cominsky40 Planck COBE vs. Planck What Planck will see

11/25/03Prof. Lynn Cominsky41 Hubble Expansion We have already seen how the galaxies move away faster at further distances We have already seen how the galaxies move away faster at further distances We measured the slope of the velocity of the galaxies vs. their distances  Hubble constant We measured the slope of the velocity of the galaxies vs. their distances  Hubble constant But is the Hubble constant really constant? But is the Hubble constant really constant? In other words, has the expansion occurred at the same rate in the past as it is right now, and will the future expansion also be at this same rate? In other words, has the expansion occurred at the same rate in the past as it is right now, and will the future expansion also be at this same rate?

11/25/03Prof. Lynn Cominsky42 Measuring the Hubble Expansion If the expansion rate is constant, distance between 2 galaxies follows yellow dotted line back in time If the expansion rate is constant, distance between 2 galaxies follows yellow dotted line back in time If rate is speeding up, then the Universe is older than we think Real Big Bang Derived from constant rate

11/25/03Prof. Lynn Cominsky43 Distances to Supernovae Type Ia supernovae are “standard candles” Type Ia supernovae are “standard candles” Occur in a binary system in which a white dwarf star accretes beyond the 1.4 M o Chandrasekhar limit and collapses and explodes Occur in a binary system in which a white dwarf star accretes beyond the 1.4 M o Chandrasekhar limit and collapses and explodes Decay time of light curve is correlated to absolute luminosity Decay time of light curve is correlated to absolute luminosity Luminosity comes from the radioactive decay of Cobalt and Nickel into Iron Luminosity comes from the radioactive decay of Cobalt and Nickel into Iron Some Type Ia supernovae are in galaxies with Cepheid variables Some Type Ia supernovae are in galaxies with Cepheid variables Good to 20% as a distance measure Good to 20% as a distance measure

11/25/03Prof. Lynn Cominsky44 Supernovae as Standard Candles If you know the absolute brightness of an object, you can measure its apparent brightness and then calculate its distance If you know the absolute brightness of an object, you can measure its apparent brightness and then calculate its distance F obs = L abs /4  d 2

11/25/03Prof. Lynn Cominsky45 Supernovae as Standard Candles Here is a typical supernova lightcurve and its spectrum Here is a typical supernova lightcurve and its spectrum Compare two distances to see if expansion rate has changed Compare two distances to see if expansion rate has changed Measure shape of curve and peak  distance Measure redshift  distance

11/25/03Prof. Lynn Cominsky46 Supernova Cosmology projects Two competing groups Two competing groups Saul Perlmutter, Lawrence Berkeley Lab Saul Perlmutter, Lawrence Berkeley Lab Brian Schmidt, Australia Brian Schmidt, Australia Analyze lightcurves vs. redshifts for many Type 1a supernovae at redshifts <2 Analyze lightcurves vs. redshifts for many Type 1a supernovae at redshifts <2 Expected to find the deceleration rate of the Universe – that the expansion was coasting to a slow halt Expected to find the deceleration rate of the Universe – that the expansion was coasting to a slow halt Instead found that the expansion seems to be accelerating! Instead found that the expansion seems to be accelerating!

11/25/03Prof. Lynn Cominsky47 Cosmological parameters -   Observations of over 80 SN (over several years) have showed that they are dimmer than would be expected if the Universe was expanding at a constant rate or slowing down (as was previously thought) Observations of over 80 SN (over several years) have showed that they are dimmer than would be expected if the Universe was expanding at a constant rate or slowing down (as was previously thought) This means that some unknown “dark energy” is causing the Universe to fly apart at ever- increasing speeds. This means that some unknown “dark energy” is causing the Universe to fly apart at ever- increasing speeds. The dark energy density/critical density =   The dark energy density/critical density =   Current measurements:   –   =   ~ 0.65 Current measurements:   –   =   ~ 0.65

11/25/03Prof. Lynn Cominsky48 Accelerating Universe  M = matter   = cosmological constant Redshift

11/25/03Prof. Lynn Cominsky49 Einstein and Dark Energy When Einstein first formulated his equations of General Relativity, he believed in a static Universe (or steady state Universe) When Einstein first formulated his equations of General Relativity, he believed in a static Universe (or steady state Universe) Since the equations seemed to predict an unstable universe that would either expand or contract, he “fixed” his equations by inserting a “Cosmological Constant” called  Since the equations seemed to predict an unstable universe that would either expand or contract, he “fixed” his equations by inserting a “Cosmological Constant” called  When Hubble later found that the Universe was expanding, Einstein called the creation of the Cosmological Constant his “greatest blunder” When Hubble later found that the Universe was expanding, Einstein called the creation of the Cosmological Constant his “greatest blunder”

11/25/03Prof. Lynn Cominsky50 Einstein and Dark Energy However, now we see that there is indeed a cosmological constant term – but it acts in the opposite sense to Einstein’s original idea However, now we see that there is indeed a cosmological constant term – but it acts in the opposite sense to Einstein’s original idea The Dark Energy implied by the non-zero value of  pushes the Universe apart even faster, rather than adding stability to an unstable Universe, as Einstein originally intended. The Dark Energy implied by the non-zero value of  pushes the Universe apart even faster, rather than adding stability to an unstable Universe, as Einstein originally intended. There are many theories for Dark Energy: vacuum fluctuations, extra dimensions, etc. There are many theories for Dark Energy: vacuum fluctuations, extra dimensions, etc.

11/25/03Prof. Lynn Cominsky51 Best results from SN + CMB Contours show best fits from 2 SN groups Contours show best fits from 2 SN groups Blue region shows best fits from 2 CMB groups Blue region shows best fits from 2 CMB groups Intersection of these two also includes the most likely value for  M = 0.3 Intersection of these two also includes the most likely value for  M = 0.3

11/25/03Prof. Lynn Cominsky52 HST views Distant Supernovae 1a HST found most distant Type 1a HST found most distant Type 1a It was so far away that it occurred during the period when the expansion was still slowing down due to gravity from the galaxies in a smaller Universe It was so far away that it occurred during the period when the expansion was still slowing down due to gravity from the galaxies in a smaller Universe

11/25/03Prof. Lynn Cominsky53  (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 Universe Perlmutter et al. 40 supernovae SN data

11/25/03Prof. Lynn Cominsky54 SNAP – SuperNova Acceleration Probe SNAP would be a space- based mission with a 2-m optical telescope, 1 o square field-of-view and a 10 6 pixel CCD detector SNAP would be a space- based mission with a 2-m optical telescope, 1 o square field-of-view and a 10 6 pixel CCD detector It would be able to find 2000 SN per year – thus getting enough data to measure properties of dark matter, dark energy and cosmological parameters It would be able to find 2000 SN per year – thus getting enough data to measure properties of dark matter, dark energy and cosmological parameters

11/25/03Prof. Lynn Cominsky55 SNAP – SuperNova Acceleration Probe Expected statistical uncertainty region from SNAP observations Expected statistical uncertainty region from SNAP observations Arrow points to best value for  M Arrow points to best value for  M Solid blue line is flat Universe from CMB measurements Solid blue line is flat Universe from CMB measurements

11/25/03Prof. Lynn Cominsky56 Today’s Cosmology   = 1.0 from CMBR measurements. We live in a flat Universe.   = 1.0 from CMBR measurements. We live in a flat Universe.   <0.3 from extensive observations at various wavelengths. Includes dark matter as well as normal matter and light.   <0.3 from extensive observations at various wavelengths. Includes dark matter as well as normal matter and light.   > 0.6 from Type 1a SN observations. Many different theories for “ dark energy. ” Universe accelerates even though it is flat.   > 0.6 from Type 1a SN observations. Many different theories for “ dark energy. ” Universe accelerates even though it is flat. Hubble constant = 70 km/sec/Mpc from HST observations. Age of Universe is around 13.7 billion years. Hubble constant = 70 km/sec/Mpc from HST observations. Age of Universe is around 13.7 billion years.

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11/25/03Prof. Lynn Cominsky58 Web Resources  Ned Wright’s CMBR pages  Ned Wright’s Cosmology Tutorial  BOOMERanG  MAP mission  Planck mission   SNAP mission

11/25/03Prof. Lynn Cominsky59 Web Resources Brian Schmidt’s Supernova Pages Brian Schmidt’s Supernova Pages Hubble Space Telescope sees Distant Supernova Hubble Space Telescope sees Distant Supernova Saul Perlmutter’s Group Supernova Pages Saul Perlmutter’s Group Supernova Pages MAP Teacher’s Guide by Lindsay Clark MAP Teacher’s Guide by Lindsay Clark   George Smoot’s group pages