11/25/03prof. lynn cominsky1 class web site: lynnc/courses/a305 office: darwin 329a (707) 664-2655...

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


Group 13Group 13


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


Big Bang TimelineBig Bang Timeline

We are hereToday’s lecture


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


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


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


COBE data/FIRASCOBE data/FIRAS

Far InfraRed Absolute Spectrophotometer



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



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


Geometry Geometry

See how parallel laser light beams fired by the space slug are affected by the geometry of space


(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


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”


COBE data/DMRCOBE data/DMR

Dipole due to movement of Solar System

warm

cool



Dipole removed to show “wrinkles”



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)


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



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


Fluctuations and geometryFluctuations and geometry


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



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


BOOMERanGBOOMERanG

Photos from previous flight in

Antarctica


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


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


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


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:


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


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


WMAPWMAP


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


WMAP correctionsWMAP corrections

Removing the dipole caused by Removing the dipole caused by Earth’s motionEarth’s motion


WMAP correctionsWMAP corrections

Removing the foreground signal Removing the foreground signal from our Galaxy to show the from our Galaxy to show the backgroundbackground


Universe’s Baby PicturesUniverse’s Baby Pictures

Red is warmer

Blue is Blue is coolercooler

Credit: NASA/WMAP


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


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


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.


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


WMAP angular power spectrumWMAP angular power spectrum


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


PlanckPlanck

COBE vs. Planck

What Planck will see


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?


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


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


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


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


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!


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


Accelerating UniverseAccelerating Universe

M = matter

= cosmological constant

0 0.2 10.80.60.4Redshift


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”


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.


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


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


(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


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


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


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.


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/


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/

11/25/03prof. lynn cominsky1 class web site: lynnc/courses/a305 office: darwin 329a (707) 664-2655...

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