Embed Size (px)
Citation preview
1
The Accelerating Universe: The Accelerating Universe: Why you should worry…Why you should worry…
The Accelerating Universe: The Accelerating Universe: Why you should worry…Why you should worry…
2006 Hoxton Lecture2006 Hoxton Lecture
Christopher StubbsChristopher Stubbs
Department of Physics Department of Physics
DepartmeDepartment nt of Astronomyof Astronomy
Harvard UniversityHarvard University
2006 Hoxton Lecture2006 Hoxton Lecture
Christopher StubbsChristopher Stubbs
Department of Physics Department of Physics
DepartmeDepartment nt of Astronomyof Astronomy
Harvard UniversityHarvard University
This is a remarkable time This is a remarkable time This is a remarkable time This is a remarkable time
Our view of the Universe is shifting, yet againOur view of the Universe is shifting, yet again
Sun-centered solar systemSun-centered solar system
Galactic structureGalactic structure
Recognition of external galaxiesRecognition of external galaxies
Discovery of Expansion of the UniverseDiscovery of Expansion of the Universe
Big Bang paradigm, inflationBig Bang paradigm, inflation
Dark Matter >> Luminous matterDark Matter >> Luminous matter
Discovery that the rate of cosmic expansion is increasing:Discovery that the rate of cosmic expansion is increasing:
The “Accelerating” Universe The “Accelerating” Universe
Our view of the Universe is shifting, yet againOur view of the Universe is shifting, yet again
Sun-centered solar systemSun-centered solar system
Galactic structureGalactic structure
Recognition of external galaxiesRecognition of external galaxies
Discovery of Expansion of the UniverseDiscovery of Expansion of the Universe
Big Bang paradigm, inflationBig Bang paradigm, inflation
Dark Matter >> Luminous matterDark Matter >> Luminous matter
Discovery that the rate of cosmic expansion is increasing:Discovery that the rate of cosmic expansion is increasing:
The “Accelerating” Universe The “Accelerating” Universe
3
Emergence of a Standard CosmologyEmergence of a Standard CosmologyEmergence of a Standard CosmologyEmergence of a Standard Cosmology
Our geometrically flat Universe started in a hot big bang Our geometrically flat Universe started in a hot big bang 13.7 billion yrs ago.13.7 billion yrs ago.
The evolution of the Universe is increasingly dominated by The evolution of the Universe is increasingly dominated by the phenomenology of the vacuum, the “Dark Energy”. the phenomenology of the vacuum, the “Dark Energy”.
Our geometrically flat Universe started in a hot big bang Our geometrically flat Universe started in a hot big bang 13.7 billion yrs ago.13.7 billion yrs ago.
The evolution of the Universe is increasingly dominated by The evolution of the Universe is increasingly dominated by the phenomenology of the vacuum, the “Dark Energy”. the phenomenology of the vacuum, the “Dark Energy”.
Matter, mostly non-baryonic, Matter, mostly non-baryonic, is a minor component. “Dark is a minor component. “Dark matter” matters most. matter” matters most.
Luminous matter comprises Luminous matter comprises a very small fraction of the a very small fraction of the mass of the Universe. mass of the Universe.
Matter, mostly non-baryonic, Matter, mostly non-baryonic, is a minor component. “Dark is a minor component. “Dark matter” matters most. matter” matters most.
Luminous matter comprises Luminous matter comprises a very small fraction of the a very small fraction of the mass of the Universe. mass of the Universe.
preposterouspreposterous
It’s like living through a bad episode It’s like living through a bad episode of Star Trek!of Star Trek!
It’s like living through a bad episode It’s like living through a bad episode of Star Trek!of Star Trek!
Empty regions of space (vacuum) interact via a Empty regions of space (vacuum) interact via a repulsive gravitational force.repulsive gravitational force.
This effect will increasingly dominate, leading to all This effect will increasingly dominate, leading to all unbound galaxies eventually being unobservableunbound galaxies eventually being unobservable
Scientists at the interface between particle physics Scientists at the interface between particle physics and gravity are in a more sophisticated state of and gravity are in a more sophisticated state of confusion than ever before…confusion than ever before…
Empty regions of space (vacuum) interact via a Empty regions of space (vacuum) interact via a repulsive gravitational force.repulsive gravitational force.
This effect will increasingly dominate, leading to all This effect will increasingly dominate, leading to all unbound galaxies eventually being unobservableunbound galaxies eventually being unobservable
Scientists at the interface between particle physics Scientists at the interface between particle physics and gravity are in a more sophisticated state of and gravity are in a more sophisticated state of confusion than ever before…confusion than ever before…
An accelerating Universe: An accelerating Universe: some things to worry about...some things to worry about...
An accelerating Universe: An accelerating Universe: some things to worry about...some things to worry about...
Worry #1: Worry #1: What if the observations are wrong or misinterpreted?What if the observations are wrong or misinterpreted?
Worry #2:Worry #2: What if the observations are right!? What if the observations are right!?
Worry #3:Worry #3: What are the implications?What are the implications?
Worry #4:Worry #4: Prospects for understanding the underlying physics?Prospects for understanding the underlying physics?
Worry #1: Worry #1: What if the observations are wrong or misinterpreted?What if the observations are wrong or misinterpreted?
Worry #2:Worry #2: What if the observations are right!? What if the observations are right!?
Worry #3:Worry #3: What are the implications?What are the implications?
Worry #4:Worry #4: Prospects for understanding the underlying physics?Prospects for understanding the underlying physics?
6
Reason to Worry #1: Reason to Worry #1: What if the observations are wrong?!What if the observations are wrong?!
Reason to Worry #1: Reason to Worry #1: What if the observations are wrong?!What if the observations are wrong?!
““Cosmologists are often in error, but seldom in Cosmologists are often in error, but seldom in doubt”doubt”
Need a way to gauge Need a way to gauge our level of concern…our level of concern…
““Cosmologists are often in error, but seldom in Cosmologists are often in error, but seldom in doubt”doubt”
Need a way to gauge Need a way to gauge our level of concern…our level of concern…
7
Close, Far,Close, Far,Recent AncientRecent Ancient
Expansion Expansion historyhistory can be mapped by measuring can be mapped by measuring both distances and redshiftsboth distances and redshifts
Our View of the Expanding UniverseOur View of the Expanding UniverseOur View of the Expanding UniverseOur View of the Expanding Universe
Expansion causes stretching of light, “redshift”Expansion causes stretching of light, “redshift”
8
A Cosmic Sum RuleA Cosmic Sum RuleA Cosmic Sum RuleA Cosmic Sum Rule
General Relativity + isotropy and homogeneity General Relativity + isotropy and homogeneity require that (in the relevant units)require that (in the relevant units)
geometrygeometry + + mattermatter + +
nergynergy = 1 = 1
If the underlying geometry is flat, and if If the underlying geometry is flat, and if mm <1 <1
then the cosmological constant term then the cosmological constant term must must be be non-zero. non-zero.
So it would seem……..So it would seem……..
General Relativity + isotropy and homogeneity General Relativity + isotropy and homogeneity require that (in the relevant units)require that (in the relevant units)
geometrygeometry + + mattermatter + +
nergynergy = 1 = 1
If the underlying geometry is flat, and if If the underlying geometry is flat, and if mm <1 <1
then the cosmological constant term then the cosmological constant term must must be be non-zero. non-zero.
So it would seem……..So it would seem……..
9
(Hubble Space Telescope, NASA)(Hubble Space Telescope, NASA)
Supernovae are powerful cosmological probes
Distances to ~6% from brightness
Redshifts from features in spectra
10
Redshift = Δλ/λ
DistancetoSupernova
Faraway
Nearby0.01 0.1 1.0
Δλλ
Schmidt et al, High-z SN TeamSchmidt et al, High-z SN Team
11
Extinction by “gray” dust?Extinction by “gray” dust?Careful multicolor measurements, esp. in IRExploit different z-dependenceLook at SNe behind clusters of galaxies
““Evolutionary” Effects?Evolutionary” Effects?Use stellar populations of different ages as a proxy
Selection differences in nearby vs. distant Selection differences in nearby vs. distant samples?samples?
Increase the sample of well-monitored SneCalibrate detection efficiencies
K-corrections, Galactic extinction, K-corrections, Galactic extinction, photometric zeropoints....photometric zeropoints....
See See Leibundgut, astro-ph/0003326Leibundgut, astro-ph/0003326
Extinction by “gray” dust?Extinction by “gray” dust?Careful multicolor measurements, esp. in IRExploit different z-dependenceLook at SNe behind clusters of galaxies
““Evolutionary” Effects?Evolutionary” Effects?Use stellar populations of different ages as a proxy
Selection differences in nearby vs. distant Selection differences in nearby vs. distant samples?samples?
Increase the sample of well-monitored SneCalibrate detection efficiencies
K-corrections, Galactic extinction, K-corrections, Galactic extinction, photometric zeropoints....photometric zeropoints....
See See Leibundgut, astro-ph/0003326Leibundgut, astro-ph/0003326
12
The accelerating Universe scenario is The accelerating Universe scenario is supported by multiple independent lines supported by multiple independent lines
of evidenceof evidence
The accelerating Universe scenario is The accelerating Universe scenario is supported by multiple independent lines supported by multiple independent lines
of evidenceof evidence• Lower bound on age, from starsLower bound on age, from stars
• Inventories of cosmic matter contentInventories of cosmic matter content
• Measurements of expansion history using supernovaeMeasurements of expansion history using supernovae
• Primordial element abundances Primordial element abundances
• Cosmic Microwave Background provides strong Cosmic Microwave Background provides strong
confirmationconfirmation
• Lower bound on age, from starsLower bound on age, from stars
• Inventories of cosmic matter contentInventories of cosmic matter content
• Measurements of expansion history using supernovaeMeasurements of expansion history using supernovae
• Primordial element abundances Primordial element abundances
• Cosmic Microwave Background provides strong Cosmic Microwave Background provides strong
confirmationconfirmation
13
WMAP- The Relic Hiss of WMAP- The Relic Hiss of the Big Bangthe Big Bang
WMAP- The Relic Hiss of WMAP- The Relic Hiss of the Big Bangthe Big Bang
(NASA)(NASA)
14
High-z Supernova Search Team
Microwave Background
Cluster Masses
m
““Best Fit” at Best Fit” at massmass ~ 0.3 ~ 0.3
~ 0.7~ 0.7
Is the expansion Is the expansion reallyreally accelerating? accelerating?
What does this mean?What does this mean?
Insufficient mass to halt the Insufficient mass to halt the expansionexpansion
Rate of expansion is Rate of expansion is increasing…increasing…
15
So, are the observations are wrong?So, are the observations are wrong?So, are the observations are wrong?So, are the observations are wrong?
My assessment:My assessment:
Probably not, the effect Probably not, the effect seems to be real. seems to be real.
My assessment:My assessment:
Probably not, the effect Probably not, the effect seems to be real. seems to be real.
16
Reason to Worry #2: Reason to Worry #2: What if the observations are right?!What if the observations are right?!
Reason to Worry #2: Reason to Worry #2: What if the observations are right?!What if the observations are right?!
What’s responsible for what we see? What’s responsible for what we see? What’s responsible for what we see? What’s responsible for what we see?
17
Three philosophically distinct possibilitiesThree philosophically distinct possibilities......Three philosophically distinct possibilitiesThree philosophically distinct possibilities......
• A “classical” cosmological constant, as envisioned A “classical” cosmological constant, as envisioned by Einstein, residing in the gravitational sector. by Einstein, residing in the gravitational sector.
• A “Vacuum energy” effect, arising from quantum A “Vacuum energy” effect, arising from quantum fluctuations in the vacuum, acting as a “source” fluctuations in the vacuum, acting as a “source” termterm
• Departure from GR on cosmological length scalesDeparture from GR on cosmological length scales
• A “classical” cosmological constant, as envisioned A “classical” cosmological constant, as envisioned by Einstein, residing in the gravitational sector. by Einstein, residing in the gravitational sector.
• A “Vacuum energy” effect, arising from quantum A “Vacuum energy” effect, arising from quantum fluctuations in the vacuum, acting as a “source” fluctuations in the vacuum, acting as a “source” termterm
• Departure from GR on cosmological length scalesDeparture from GR on cosmological length scales
Regardless, it’s evidence of new fundamental physics!Regardless, it’s evidence of new fundamental physics!Regardless, it’s evidence of new fundamental physics!Regardless, it’s evidence of new fundamental physics!
18
Worry #2: Worry #2: What if the observations are right?What if the observations are right?
Worry #2: Worry #2: What if the observations are right?What if the observations are right?
It’s good news: It’s good news:
Clear evidence for new Clear evidence for new physics at the interface physics at the interface between gravity and between gravity and quantum mechanics. quantum mechanics.
It’s good news: It’s good news:
Clear evidence for new Clear evidence for new physics at the interface physics at the interface between gravity and between gravity and quantum mechanics. quantum mechanics.
19
Worry #3: Worry #3: What are the implications?What are the implications?
Worry #3: Worry #3: What are the implications?What are the implications?
If there is some Dark Energy permeating If there is some Dark Energy permeating the Universe, what are the implications? the Universe, what are the implications?
If there is some Dark Energy permeating If there is some Dark Energy permeating the Universe, what are the implications? the Universe, what are the implications?
20
Has Dark Energy toppled reductionism!?Has Dark Energy toppled reductionism!?Has Dark Energy toppled reductionism!?Has Dark Energy toppled reductionism!?• The reductionist approach to physics The reductionist approach to physics
has been very successfulhas been very successful• Newton’s Universal law of gravitation• Atoms, Electricity & Magnetism• Quarks and Leptons• Unification of fundamental interactions...
• The reductionist approach to physics The reductionist approach to physics has been very successfulhas been very successful
• Newton’s Universal law of gravitation• Atoms, Electricity & Magnetism• Quarks and Leptons• Unification of fundamental interactions...
mmee
mmtoptop
= 0= 0
Elegant TOE equationElegant TOE equation
The goal:The goal:
Constrained parametersConstrained parameters
21
Through some profound but not yet understood mechanism, the
vacuum energy must be cancelled to arrive at value of identically zero ummm... Supersymmetry uhhh ...Planck Mass
...
22
Two possible “natural” values Two possible “natural” values Two possible “natural” values Two possible “natural” values
• Vacuum energy integrated up to Planck Vacuum energy integrated up to Planck scale scale
• Cancellation via tooth fairy:Cancellation via tooth fairy:
• But it’s measured to be around 0.7!But it’s measured to be around 0.7!
• Vacuum energy integrated up to Planck Vacuum energy integrated up to Planck scale scale
• Cancellation via tooth fairy:Cancellation via tooth fairy:
• But it’s measured to be around 0.7!But it’s measured to be around 0.7!
12010 :
0.0000000000000000000000000000.... =
23
From string theory perspective...From string theory perspective...From string theory perspective...From string theory perspective...
• Constraining Constraining =0 reduces number of =0 reduces number of candidate vacuum configurations candidate vacuum configurations (“landscapes”).(“landscapes”).
• With non-zero With non-zero , get of order 10, get of order 10500500 landscapes, each with potentially different landscapes, each with potentially different kinds of physicskinds of physics
• What picks the one we inhabit? What picks the one we inhabit?
• Constraining Constraining =0 reduces number of =0 reduces number of candidate vacuum configurations candidate vacuum configurations (“landscapes”).(“landscapes”).
• With non-zero With non-zero , get of order 10, get of order 10500500 landscapes, each with potentially different landscapes, each with potentially different kinds of physicskinds of physics
• What picks the one we inhabit? What picks the one we inhabit?
24
25
The “selection effect” viewpointThe “selection effect” viewpointThe “selection effect” viewpointThe “selection effect” viewpoint• From all possible (presumably equally likely) From all possible (presumably equally likely)
sets of parameters and interaction strengths, sets of parameters and interaction strengths, only a small subset could produce heavy only a small subset could produce heavy elements and evolve life.elements and evolve life.
• This selection effect is what determines This selection effect is what determines
observables, such as mobservables, such as mee/m/mpp, coupling strengths, , coupling strengths, etc, and etc, and notnot something deep and fundamental! something deep and fundamental!
Ouch.Ouch.
• From all possible (presumably equally likely) From all possible (presumably equally likely) sets of parameters and interaction strengths, sets of parameters and interaction strengths, only a small subset could produce heavy only a small subset could produce heavy elements and evolve life.elements and evolve life.
• This selection effect is what determines This selection effect is what determines
observables, such as mobservables, such as mee/m/mpp, coupling strengths, , coupling strengths, etc, and etc, and notnot something deep and fundamental! something deep and fundamental!
Ouch.Ouch.
26
Worry #3: Worry #3: What are the implications?What are the implications?
Worry #3: Worry #3: What are the implications?What are the implications?
It is entirely possible that It is entirely possible that astrophysical observations astrophysical observations of non-zero vacuum of non-zero vacuum energy have killed the energy have killed the reductionist approach to reductionist approach to physics. physics.
It is entirely possible that It is entirely possible that astrophysical observations astrophysical observations of non-zero vacuum of non-zero vacuum energy have killed the energy have killed the reductionist approach to reductionist approach to physics. physics.
27
Worry #4: What are the prospects Worry #4: What are the prospects for figuring this out?for figuring this out?
Worry #4: What are the prospects Worry #4: What are the prospects for figuring this out?for figuring this out?
Given the confusion over what’s going on Given the confusion over what’s going on here, how likely are we to figure it out? here, how likely are we to figure it out?
Given the confusion over what’s going on Given the confusion over what’s going on here, how likely are we to figure it out? here, how likely are we to figure it out?
28
Dark Energy’s Equation of StateDark Energy’s Equation of StateDark Energy’s Equation of StateDark Energy’s Equation of State w = 0, matter
P = w w = 1/3 ,radiation
w = 1, w = N/3, topological defects
Our current challenge is measuring the value of w.
w = 0, matter
P = w w = 1/3 ,radiation
w = 1, w = N/3, topological defects
Our current challenge is measuring the value of w.
Probing the nature of Dark EnergyProbing the nature of Dark EnergyProbing the nature of Dark EnergyProbing the nature of Dark Energy
• SN cosmology testsSN cosmology tests
• Gravitational lensingGravitational lensing
• Galaxy cluster abundances Galaxy cluster abundances
• Baryon oscillationsBaryon oscillations
• Particle physics experimentsParticle physics experiments
• Tests of gravity on all scalesTests of gravity on all scales
• SN cosmology testsSN cosmology tests
• Gravitational lensingGravitational lensing
• Galaxy cluster abundances Galaxy cluster abundances
• Baryon oscillationsBaryon oscillations
• Particle physics experimentsParticle physics experiments
• Tests of gravity on all scalesTests of gravity on all scales
signal!signal!signal!signal!
30
The ESSENCE SurveyThe ESSENCE SurveyThe ESSENCE SurveyThe ESSENCE Survey
• Our goal is to determine the equation of state Our goal is to determine the equation of state parameter to 10%parameter to 10%
• This should help determine whether This should help determine whether belongs on the belongs on the left or right side of the Einstein equations…left or right side of the Einstein equations…
• w = w = 1 or any variation over cosmic time favors QM1 or any variation over cosmic time favors QM
• Supernovae are well suited to this task – they probe Supernovae are well suited to this task – they probe directly the epoch of accelerating expansion. directly the epoch of accelerating expansion.
• Our goal is to determine the equation of state Our goal is to determine the equation of state parameter to 10%parameter to 10%
• This should help determine whether This should help determine whether belongs on the belongs on the left or right side of the Einstein equations…left or right side of the Einstein equations…
• w = w = 1 or any variation over cosmic time favors QM1 or any variation over cosmic time favors QM
• Supernovae are well suited to this task – they probe Supernovae are well suited to this task – they probe directly the epoch of accelerating expansion. directly the epoch of accelerating expansion.
31
Claudio Aguilera --- CTIO/NOAO Claudio Aguilera --- CTIO/NOAO
Brian Barris --- Univ of Hawaii Brian Barris --- Univ of Hawaii
Andy Becker --- Bell Labs/Univ. of Washington Andy Becker --- Bell Labs/Univ. of Washington
Peter Challis --- Harvard-Smithsonian CfA Peter Challis --- Harvard-Smithsonian CfA
Ryan Chornock --- UC Berkeley Ryan Chornock --- UC Berkeley
Alejandro Clocchiatti --- Univ Catolica de Chile Alejandro Clocchiatti --- Univ Catolica de Chile
Ricardo Covarrubias --- Univ of WashingtonRicardo Covarrubias --- Univ of Washington
Alex V. Filippenko --- Univ of Ca, Berkeley Alex V. Filippenko --- Univ of Ca, Berkeley
Arti Garg --- Harvard UniversityArti Garg --- Harvard University
Peter M. Garnavich --- Notre Dame University Peter M. Garnavich --- Notre Dame University
Malcolm Hicken --- Harvard University Malcolm Hicken --- Harvard University
Saurabh Jha --- UC BerkeleySaurabh Jha --- UC Berkeley
Robert Kirshner --- Harvard-Smithsonian CfA Robert Kirshner --- Harvard-Smithsonian CfA
Kevin Krisciunas --- Notre Dame Univ. Kevin Krisciunas --- Notre Dame Univ.
Bruno Leibundgut --- European Southern Observatory Bruno Leibundgut --- European Southern Observatory
Weidong D. Li --- Univ of California, Berkeley Weidong D. Li --- Univ of California, Berkeley
Thomas Matheson --- Harvard-Smithsonian CfAThomas Matheson --- Harvard-Smithsonian CfA
Gajus Miknaitis --- FermilabGajus Miknaitis --- Fermilab
Jose Prieto --- The Ohio State UniversityJose Prieto --- The Ohio State University
Armin Rest --- NOAO/CTIO Armin Rest --- NOAO/CTIO
Adam G. Reiss --- Space Telescope Science Institute Adam G. Reiss --- Space Telescope Science Institute
Brian P. Schmidt --- Mt. Stromlo Siding Springs Observatories Brian P. Schmidt --- Mt. Stromlo Siding Springs Observatories
Chris Smith --- CTIO/NOAO Chris Smith --- CTIO/NOAO
Jesper Sollerman --- Stockholm Observatory Jesper Sollerman --- Stockholm Observatory
Jason Spyromilio --- European Southern Observatory Jason Spyromilio --- European Southern Observatory
Christopher Stubbs --- Harvard UniversityChristopher Stubbs --- Harvard University
Nicholas B. Suntzeff --- CTIO/NOAO Nicholas B. Suntzeff --- CTIO/NOAO
John L. Tonry --- Univ of HawaiiJohn L. Tonry --- Univ of Hawaii
Michael Wood-Vasey --- Harvard UniversityMichael Wood-Vasey --- Harvard University
ESSENCE Survey TeamESSENCE Survey Team
32
ImplementationImplementationImplementationImplementation
• 5 year project on 4m telescope 5 year project on 4m telescope
at CTIO in Chileat CTIO in Chile
• Wide field images in 2 bands Wide field images in 2 bands
• Same-night detection of SNeSame-night detection of SNe
• Spectroscopy Spectroscopy Magellan, Keck, Gemini telescopes
• Near-IR from Hubble Near-IR from Hubble
• Goal is ~200 SNe, 0.2<z<0.8Goal is ~200 SNe, 0.2<z<0.8
• 5 year project on 4m telescope 5 year project on 4m telescope
at CTIO in Chileat CTIO in Chile
• Wide field images in 2 bands Wide field images in 2 bands
• Same-night detection of SNeSame-night detection of SNe
• Spectroscopy Spectroscopy Magellan, Keck, Gemini telescopes
• Near-IR from Hubble Near-IR from Hubble
• Goal is ~200 SNe, 0.2<z<0.8Goal is ~200 SNe, 0.2<z<0.8
33
34
38
ESSENCE Survey Progress to ESSENCE Survey Progress to date – 3 of 5 seasons completeddate – 3 of 5 seasons completedESSENCE Survey Progress to ESSENCE Survey Progress to
date – 3 of 5 seasons completeddate – 3 of 5 seasons completed
39
(High-z Supernova Team)
Image SubtractionImage SubtractionImage SubtractionImage Subtraction
40
Preliminary ESSENCE Preliminary ESSENCE constraints on constraints on ww
Preliminary ESSENCE Preliminary ESSENCE constraints on constraints on ww
• Essence Essence supernovae plus supernovae plus nearby sample nearby sample jointly constrain w jointly constrain w and and mm..
• Adding other data Adding other data sets collapses sets collapses contours. contours.
• Essence Essence supernovae plus supernovae plus nearby sample nearby sample jointly constrain w jointly constrain w and and mm..
• Adding other data Adding other data sets collapses sets collapses contours. contours.
41
Next-Generation FacilitiesNext-Generation FacilitiesNext-Generation FacilitiesNext-Generation Facilities
Microwave background - Microwave background - Better angular resolution CMB mapsBetter angular resolution CMB mapsDetection of clusters of galaxies vs. zDetection of clusters of galaxies vs. z
Supernovae – Supernovae – Dedicated Dark Energy satellite missionDedicated Dark Energy satellite missionLarge Synoptic Survey Telescope (LSST)Large Synoptic Survey Telescope (LSST)
Weak Gravitational LensingWeak Gravitational LensingBoth ground-based and space basedBoth ground-based and space based
Probing the foundations of gravityProbing the foundations of gravityEquivalence principleEquivalence principleInverse square lawInverse square law
SNAP, Lawrence Berkeley LaboratorySNAP, Lawrence Berkeley Laboratory
LSST CorporationLSST Corporation
42
What would an optimized What would an optimized ground-based facility look like?ground-based facility look like?
What would an optimized What would an optimized ground-based facility look like?ground-based facility look like?
• Large collecting area Large collecting area
• Wide field of viewWide field of view
• Real-time analysis of dataReal-time analysis of data
• Significant leap in figure-of-meritSignificant leap in figure-of-meritArea x Field of View
• Large collecting area Large collecting area
• Wide field of viewWide field of view
• Real-time analysis of dataReal-time analysis of data
• Significant leap in figure-of-meritSignificant leap in figure-of-meritArea x Field of View
43
Large Synoptic Survey TelescopeLarge Synoptic Survey TelescopeLarge Synoptic Survey TelescopeLarge Synoptic Survey TelescopeHighly ranked in Decadal SurveyHighly ranked in Decadal Survey
Optimized for time domainOptimized for time domain
scan modescan mode
deep modedeep mode
10 square degree field10 square degree field
6.5m effective aperture6.5m effective aperture
24th mag in 20 sec24th mag in 20 sec
>20 Tbyte/night>20 Tbyte/night
Real-time analysisReal-time analysis
Simultaneous multiple science goalsSimultaneous multiple science goals
44
LSST Merges 3 Enabling LSST Merges 3 Enabling Technologies Technologies
LSST Merges 3 Enabling LSST Merges 3 Enabling Technologies Technologies
• Large Aperture OpticsLarge Aperture Optics
• Computing and Data Storage Computing and Data Storage
• High Efficiency DetectorsHigh Efficiency Detectors
• Large Aperture OpticsLarge Aperture Optics
• Computing and Data Storage Computing and Data Storage
• High Efficiency DetectorsHigh Efficiency Detectors
45
Large Mirror FabricationLarge Mirror FabricationLarge Mirror FabricationLarge Mirror Fabrication
University of ArizonaUniversity of Arizona
46
Cost per GigabyteCost per GigabyteCost per GigabyteCost per Gigabyte
47
Large Format CCD MosaicsLarge Format CCD MosaicsLarge Format CCD MosaicsLarge Format CCD MosaicsMegacam, CfA/HarvardMegacam, CfA/Harvard
Unobscured Aperture, sq meters
Fie
ld o
f V
iew
, sq
deg
rees
100 m2 deg2
500 m2 deg2
300 m2 deg2
LSSTPS1 PS4
KeckSubaruSDSS
DES
Magellan
CTIO
CFHT
49
50
Near Earth AsteroidsNear Earth AsteroidsNear Earth AsteroidsNear Earth Asteroids
• Inventory of solar system is incompleteInventory of solar system is incomplete• R=1 km asteroids are dinosaur killersR=1 km asteroids are dinosaur killers• R=300m asteroids in ocean wipe out a R=300m asteroids in ocean wipe out a
coastlinecoastline• Demanding project: requires mapping the Demanding project: requires mapping the
sky down to 24sky down to 24thth every few days, individual every few days, individual exposures not to exceed ~20 sec. exposures not to exceed ~20 sec.
• LSST will detect NEAs to 300m LSST will detect NEAs to 300m
• Inventory of solar system is incompleteInventory of solar system is incomplete• R=1 km asteroids are dinosaur killersR=1 km asteroids are dinosaur killers• R=300m asteroids in ocean wipe out a R=300m asteroids in ocean wipe out a
coastlinecoastline• Demanding project: requires mapping the Demanding project: requires mapping the
sky down to 24sky down to 24thth every few days, individual every few days, individual exposures not to exceed ~20 sec. exposures not to exceed ~20 sec.
• LSST will detect NEAs to 300m LSST will detect NEAs to 300m
51
LSST ChallengesLSST ChallengesLSST ChallengesLSST Challenges
• Large effective aperture wide field telescopeLarge effective aperture wide field telescope
• 3 Gpix focal plane3 Gpix focal plane
• Analysis pipelineAnalysis pipeline
• Automated Variability ClassificationAutomated Variability Classification
• Database schema/structure and indexingDatabase schema/structure and indexing
• $$$$
• Large effective aperture wide field telescopeLarge effective aperture wide field telescope
• 3 Gpix focal plane3 Gpix focal plane
• Analysis pipelineAnalysis pipeline
• Automated Variability ClassificationAutomated Variability Classification
• Database schema/structure and indexingDatabase schema/structure and indexing
• $$$$
52
Worry #4: Worry #4: What are the prospects for deeper What are the prospects for deeper
understanding?understanding?
Worry #4: Worry #4: What are the prospects for deeper What are the prospects for deeper
understanding?understanding?
Next steps are fairly clear: precision Next steps are fairly clear: precision cosmology.cosmology.
What if w= What if w= 1.000?1.000?
We’ll need more clues:We’ll need more clues: particle physicsparticle physics expt’l gravityexpt’l gravity … ….?… .?…
Next steps are fairly clear: precision Next steps are fairly clear: precision cosmology.cosmology.
What if w= What if w= 1.000?1.000?
We’ll need more clues:We’ll need more clues: particle physicsparticle physics expt’l gravityexpt’l gravity … ….?… .?…
A summary of where we stand..A summary of where we stand..A summary of where we stand..A summary of where we stand..
1.1. Maybe it’s not right?Maybe it’s not right?
2.2. Maybe it Maybe it isis right? right?
3.3. Implications?Implications?
4.4. Prospects?Prospects?
1.1. Maybe it’s not right?Maybe it’s not right?
2.2. Maybe it Maybe it isis right? right?
3.3. Implications?Implications?
4.4. Prospects?Prospects?
54
Closing thoughtsClosing thoughtsClosing thoughtsClosing thoughts
The Accelerating Universe poses a challenge to The Accelerating Universe poses a challenge to both theory and experiment/observationboth theory and experiment/observation
This problem sits squarely at an interface we don’t This problem sits squarely at an interface we don’t understand: the intersection between gravity and understand: the intersection between gravity and quantum mechanicsquantum mechanics
Look for upcoming new results from Look for upcoming new results from • Supernova and galaxy cluster cosmology• Gravitational lensing• Large Hadron Collider (LHC) • Tests of gravitation, on all scales
The Accelerating Universe poses a challenge to The Accelerating Universe poses a challenge to both theory and experiment/observationboth theory and experiment/observation
This problem sits squarely at an interface we don’t This problem sits squarely at an interface we don’t understand: the intersection between gravity and understand: the intersection between gravity and quantum mechanicsquantum mechanics
Look for upcoming new results from Look for upcoming new results from • Supernova and galaxy cluster cosmology• Gravitational lensing• Large Hadron Collider (LHC) • Tests of gravitation, on all scales
