astronomy 305/frontiers in astronomy

12/2/03 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 329A and NASA EPOOffice: Darwin 329A and NASA EPO

(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 14Group 14


What is the Universe What is the Universe made of?made of? Regular matterRegular matter

Heavy elements 0.03%Heavy elements 0.03% Stars 0.5%Stars 0.5% Free Hydrogen and Helium 4% (Lecture Free Hydrogen and Helium 4% (Lecture

11)11) Neutrinos 0.3% (Lecture 10)Neutrinos 0.3% (Lecture 10) Dark Energy 60% (Lecture 13)Dark Energy 60% (Lecture 13) Dark Matter 30% (this lecture)Dark Matter 30% (this lecture)


Kepler’s Third Law movieKepler’s Third Law movie PP22 is proportional to a is proportional to a33


Dark Matter EvidenceDark Matter Evidence In 1930, Fritz Zwicky discovered In 1930, Fritz Zwicky discovered

that the galaxies in the Coma that the galaxies in the Coma cluster were moving too fast to cluster were moving too fast to remain bound in the cluster remain bound in the cluster according to the according to the Virial TheoremVirial Theorem

KPNO image of the Coma cluster of galaxies - almost every object in this picture is a galaxy! Coma is 300 million light years away.


Virial TheoremVirial Theorem Stable galaxies should obey this law: Stable galaxies should obey this law: 2K = -U2K = -U where where K=½mvK=½mv22 is the Kinetic Energy is the Kinetic Energy U = -U = -GMm/rGMm/r is the Potential Energy is the Potential Energy (( is usually is usually

0.5 - 2, and depends on the mass distribution)0.5 - 2, and depends on the mass distribution) Putting these together, we have Putting these together, we have M=vM=v22r/r/GG. . MeasureMeasure M, r M, r and and vv22 from observations of the from observations of the

galaxies; then use galaxies; then use MM and and rr to calculate to calculate vvvirial virial

Compare Compare vvmeasured measured to to vvvirialvirial

vvmeasuredmeasured > > vvvirial virial which implies which implies MM was too small was too small


Dark Matter EvidenceDark Matter Evidence Galaxy Rotation CurvesGalaxy Rotation Curves • Measure the velocity of

stars and gas clouds from their Doppler shifts at various distances

• Velocity curve flattens out!

• Halo seems to cut off after r= 50 kpc

NGC 3198

v2=GM/r where M is mass within a radius r

Since v flattens out, M must increase with increasing r!


Dark Matter EvidenceDark Matter Evidence Cluster Mass Java simulationCluster Mass Java simulation

Rotation Curve Java simulationRotation Curve Java simulation


Dark Matter EvidenceDark Matter Evidence

Hot gas in Galaxy Hot gas in Galaxy ClustersClusters

• Measure the mass of light emitting matter in galaxies in the cluster (stars)

• Measure mass of hot gas - it is 3-5 times greater than the mass in stars

• Calculate the mass the cluster needs to hold in the hot gas - it is 5 - 10 times more than the mass of the gas plus the mass of the stars!


Dark Matter HaloDark Matter Halo The rotating disks of The rotating disks of

the spiral galaxies that the spiral galaxies that we see are not stablewe see are not stable

Dark matter halos Dark matter halos provide enough provide enough gravitational force to gravitational force to hold the galaxies hold the galaxies togethertogether

The halos also The halos also maintain the rapid maintain the rapid velocities of the velocities of the outermost stars in the outermost stars in the galaxiesgalaxies


Types of Dark MatterTypes of Dark Matter Baryonic Baryonic - ordinary matter: MACHOs, - ordinary matter: MACHOs,

white, red or brown dwarfs, planets, black white, red or brown dwarfs, planets, black holes, neutron stars, gas, and dustholes, neutron stars, gas, and dust

Non-baryonicNon-baryonic - neutrinos, WIMPs or other - neutrinos, WIMPs or other Supersymmetric particles and axionsSupersymmetric particles and axions

ColdCold (CDM)(CDM) - a form of non-baryonic dark - a form of non-baryonic dark matter with typical mass around 1 GeV/cmatter with typical mass around 1 GeV/c22 (e.g., WIMPs)(e.g., WIMPs)

Hot (HDM)Hot (HDM) - a form of non-baryonic dark - a form of non-baryonic dark matter with individual particle masses not matter with individual particle masses not more than 10-100 eV/cmore than 10-100 eV/c22 (e.g., neutrinos) (e.g., neutrinos)


Primordial MatterPrimordial Matter Normal matter is 3/4 Hydrogen (and about Normal matter is 3/4 Hydrogen (and about

1/4 Helium) because as the Universe cooled 1/4 Helium) because as the Universe cooled from the Big Bang, there were 7 times as from the Big Bang, there were 7 times as many protons as neutronsmany protons as neutrons

Almost all of the Deuterium made HeliumAlmost all of the Deuterium made Helium

Hydrogen = 1p + 1e

Deuterium = 1p + 1e + 1n

Helium = 2p + 2e + 2n


Primordial MatterPrimordial Matter The relative amounts of H, D and He The relative amounts of H, D and He

depend on depend on = (protons + neutrons) / = (protons + neutrons) / photonsphotons

is very small - We measure about 1 or 2 is very small - We measure about 1 or 2 atoms per 10 cubic meters of space vs. 411 atoms per 10 cubic meters of space vs. 411 photons in each cubic centimeterphotons in each cubic centimeter

The measured value for The measured value for is the same or a is the same or a little bit smaller than that derived from little bit smaller than that derived from comparing relative amounts of H, D and Hecomparing relative amounts of H, D and He

Conclusion:Conclusion: we may be missing some of we may be missing some of baryonic matter, but not enough to account baryonic matter, but not enough to account for the observed effects from dark matter!for the observed effects from dark matter!


Baryonic Dark MatterBaryonic Dark Matter Baryons are ordinary matter particlesBaryons are ordinary matter particles Protons, neutrons and electrons and Protons, neutrons and electrons and

atoms that we cannot detect through atoms that we cannot detect through visible radiationvisible radiation

Primordial Helium (and Hydrogen) – Primordial Helium (and Hydrogen) – recently measured – increased total recently measured – increased total baryonic content significantlybaryonic content significantly

Brown dwarfs, red dwarfs, planetsBrown dwarfs, red dwarfs, planets Possible primordial black holes?Possible primordial black holes? Baryonic content limited by primordial Baryonic content limited by primordial

Deuterium abundance measurementsDeuterium abundance measurements


Baryonic - Brown DwarfsBaryonic - Brown Dwarfs Mass around 0.08 MMass around 0.08 Moo

Do not undergo nuclear burning in Do not undergo nuclear burning in cores cores

First brown dwarf star Gliese 229BFirst brown dwarf star Gliese 229B


Baryonic - Red Dwarf Baryonic - Red Dwarf StarsStars

HST searched HST searched for red dwarf for red dwarf stars in the stars in the halo of the halo of the GalaxyGalaxy

Surprisingly Surprisingly few red dwarf few red dwarf stars were stars were found, < 6% found, < 6% of mass of of mass of galaxy halogalaxy halo

Expected 38 red dwarfs: Seen 0!


Ghost GalaxiesGhost Galaxies

Also known as low surface brightness Also known as low surface brightness galaxiesgalaxies

Studies have shown that fainter, Studies have shown that fainter, elliptical galaxies have a larger elliptical galaxies have a larger percentage of dark matter (up to 99%)percentage of dark matter (up to 99%)

This leads to the surprising conclusion This leads to the surprising conclusion that there may be many more ghostly that there may be many more ghostly galaxies than those we can see!galaxies than those we can see!

Each ghost galaxy has a mass around Each ghost galaxy has a mass around 10 million M10 million Moo


Baryonic –MACHOsBaryonic –MACHOs Massive Compact Massive Compact

Halo ObjectsHalo Objects Many have been Many have been

discovered discovered through through gravitational gravitational micro-lensingmicro-lensing

Not enough to Not enough to account for Dark account for Dark MatterMatter

And few in the And few in the halo!halo!

Mt. Stromlo Observatory in Australia (in better days)


Baryonic – MACHOsBaryonic – MACHOs 4 events 4 events

towards the LMCtowards the LMC 45 events 45 events

towards the towards the Galactic BulgeGalactic Bulge

8 million stars 8 million stars observed in LMCobserved in LMC

10 million stars 10 million stars observed in observed in Galactic BulgeGalactic Bulge

27,000 images 27,000 images since 6/92since 6/92


Gravitational Gravitational MicrolensingMicrolensing

Scale not Scale not large enough large enough to form two to form two separate separate imagesimages

movie


Baryonic – black holesBaryonic – black holes Primordial black holes would form at 10Primordial black holes would form at 10-5-5 s s

after the Big Bang from regions of high after the Big Bang from regions of high energy densityenergy density

Sizes and numbers of primordial black holes Sizes and numbers of primordial black holes are unknownare unknown

If too large, you would be able to see their If too large, you would be able to see their effects on stars circulating in the outer effects on stars circulating in the outer GalaxyGalaxy

Black holes also exist at the centers of most Black holes also exist at the centers of most galaxies – but are accounted for by the galaxies – but are accounted for by the luminosity of the galaxy’s central regionluminosity of the galaxy’s central region


Black Hole MACHOBlack Hole MACHO Isolated black hole seen in Galactic BulgeIsolated black hole seen in Galactic Bulge Distorts gravitational lensing light curveDistorts gravitational lensing light curve Mass of distorting object can be measuredMass of distorting object can be measured No star is seen that is bright enough…..No star is seen that is bright enough…..


Strong Gravitational Strong Gravitational LensingLensing



HST image of HST image of background background blue galaxies blue galaxies lensed by lensed by orange galaxies orange galaxies in a clusterin a cluster

““Einstein’s Einstein’s rings” can be rings” can be formed for the formed for the correct correct alignmentalignment


Large Survey Synoptic Large Survey Synoptic TelescopeTelescope At least 8 meter At least 8 meter

telescopetelescope About 3 degree field About 3 degree field

of view with high of view with high angular resolutionangular resolution

Resolve all Resolve all background galaxies background galaxies and find redshiftsand find redshifts

Goal is 3D maps of Goal is 3D maps of universe back to half universe back to half its current ageits current age


Gravitational Lens Movie #1Gravitational Lens Movie #1

Dark matter is Dark matter is clumped clumped around orange around orange cluster galaxiescluster galaxies

Background Background galaxies are galaxies are white and bluewhite and blue

Movie shows evolution of distortion as cluster moves past background during 500 million years


Gravitational Lens Movie #2Gravitational Lens Movie #2

Dark matter is Dark matter is distributed distributed more smoothly more smoothly around the around the cluster cluster galaxiesgalaxies

Background Background galaxies are galaxies are white and bluewhite and blue

Movie shows evolution of distortion as cluster moves past background during 500 million years



Spherical lensSpherical lens Perfect alignmentPerfect alignment Note formation of Note formation of

Einstein’s ringsEinstein’s rings

movie



Elliptical lensElliptical lens Einstein’s rings Einstein’s rings

break up into break up into arcs if you can arcs if you can only see the only see the brightest partsbrightest parts

movie


Baryonic – cold gasBaryonic – cold gas We can see almost all We can see almost all

the cold gas due to the cold gas due to absorption of light from absorption of light from background objectsbackground objects

Gas clouds range in Gas clouds range in size from 100 pc (Giant size from 100 pc (Giant Molecular Clouds) to Molecular Clouds) to Bok globules (0.1 pc)Bok globules (0.1 pc)

Mass of gas is about Mass of gas is about the same as mass of the same as mass of stars, and is part of stars, and is part of total baryon inventorytotal baryon inventory Gas clouds in Lagoon nebula


Baryonic –dustBaryonic –dust Dust is made of elements heavier than Dust is made of elements heavier than

Helium, which were previously produced Helium, which were previously produced by stars (<2% of total)by stars (<2% of total)

Dust absorbs and reradiates Dust absorbs and reradiates background lightbackground light

Dust clouds of the dark Pipe nebula


Non-baryonic: NeutrinosNon-baryonic: Neutrinos

There are about 100 million neutrinos per mThere are about 100 million neutrinos per m33

More (or less) types of neutrinos would lead to More (or less) types of neutrinos would lead to more (or less) primordial Helium than we seemore (or less) primordial Helium than we see

Neutrinos with mass affect the formation of Neutrinos with mass affect the formation of structure in the Universestructure in the Universe Much less small scale structure would be present Much less small scale structure would be present Observed structure sets limits on how much mass Observed structure sets limits on how much mass

neutrinos may have, and on their contribution to neutrinos may have, and on their contribution to dark matter.dark matter.

The sum of all the The sum of all the mm ~ 5 ~ 5 hh505022 eV (due to eV (due to

models of Hot and Cold DM)models of Hot and Cold DM)


Non-baryonic - axionsNon-baryonic - axions

Extremely light particles, with typical Extremely light particles, with typical mass of 10mass of 10-6-6 eV/c eV/c22

Interactions are 10Interactions are 101212 weaker than weaker than ordinary weak interactionordinary weak interaction

Density would be 10Density would be 1088 per cubic per cubic centimetercentimeter

Velocities are lowVelocities are low Axions may be detected when they Axions may be detected when they

convert to low energy photons after convert to low energy photons after passing through a strong magnetic fieldpassing through a strong magnetic field


Searching for axionsSearching for axions Superconducting Superconducting

magnet to convert magnet to convert axions into axions into microwave photonsmicrowave photons

Cryogenically cooled Cryogenically cooled microwave microwave resonance chamberresonance chamber

Cavity can be tuned Cavity can be tuned to different to different frequenciesfrequencies

Microwave signal Microwave signal amplified if seenamplified if seen


Non-baryonic - WIMPsNon-baryonic - WIMPs Weakly Interacting Massive ParticlesWeakly Interacting Massive Particles Predicted by Supersymmetry (SUSY) Predicted by Supersymmetry (SUSY)

theories of particle physicstheories of particle physics Supersymmetry tries to unify the four Supersymmetry tries to unify the four

forces of physics by adding extra forces of physics by adding extra dimensionsdimensions

WIMPs would have been easily detected in WIMPs would have been easily detected in acclerators if M < 15 GeV/cacclerators if M < 15 GeV/c22

The lightest WIMPs would be stable, and The lightest WIMPs would be stable, and could still exist in the Universe, contributing could still exist in the Universe, contributing most if not all of the Dark Mattermost if not all of the Dark Matter


CDMS for WIMPsCDMS for WIMPs Cryogenic Dark Matter SearchCryogenic Dark Matter Search 6.4 million events studied - 13 possible 6.4 million events studied - 13 possible

candidates for WIMPscandidates for WIMPs All are consistent with expected neutronAll are consistent with expected neutron

fluxflux

Cryostat holds T= 0.01 K

CDMS Lab 35 feet under Stanford


Detecting WIMPs?Detecting WIMPs? Laboratory experiments - DAMA experiment Laboratory experiments - DAMA experiment

1400 m underground at Gran Sasso Laboratory 1400 m underground at Gran Sasso Laboratory in Italy announced the discovery of seasonal in Italy announced the discovery of seasonal modulation evidence for 52 GeV WIMPsmodulation evidence for 52 GeV WIMPs

100 kg of Sodium Iodide, operated for 4 years100 kg of Sodium Iodide, operated for 4 years CDMS has 0.5 kg of Germanium, operated for CDMS has 0.5 kg of Germanium, operated for

1 year, but claims better 1 year, but claims better

background rejection techniquesbackground rejection techniques http://www.lngs.infn.it/http://www.lngs.infn.it/


HDM vs. CDM modelsHDM vs. CDM models

Supercomputer models of the evolution of Supercomputer models of the evolution of the Universe show distinct differences the Universe show distinct differences

Rapid motion of HDM particles washes out Rapid motion of HDM particles washes out small scale structure – the Universe would small scale structure – the Universe would form from the “top down”form from the “top down”

CDM particles don’t move very fast and CDM particles don’t move very fast and clump to form small structures first – clump to form small structures first – “bottom up”“bottom up”CDM HDM


CDM models vs. densityCDM models vs. density CDM models as a function of z (look-back time)CDM models as a function of z (look-back time)

NowZ=0.5Z=1.0

Critical density

Low density

Largest structures are now just forming


Dark Matter ActivityDark Matter Activity You will search a paper plate You will search a paper plate

“galaxy” for some hidden mass by “galaxy” for some hidden mass by observing its effect on how the observing its effect on how the “galaxy” “rotates”“galaxy” “rotates” In order to balance,

the torques on both sides must be equal:

T1 = F1X1 = F2X2 =

T2

where

F1 = m1g and

F2 = m2g


SuperstringsSuperstrings

Strings are little closed loops that are 10Strings are little closed loops that are 102020 times smaller than a protontimes smaller than a proton

Strings vibrate at different frequenciesStrings vibrate at different frequencies Each resonant vibration frequency creates a Each resonant vibration frequency creates a

different particledifferent particle Matter is composed of harmonies from Matter is composed of harmonies from

vibrating strings – the Universe is a string vibrating strings – the Universe is a string symphonysymphony

“String theory is twenty-first century physics that fell accidentally into the twentieth

century” - Edward Witten


SuperstringsSuperstrings

Strings can execute many different Strings can execute many different motions through spacetimemotions through spacetime

But, there are only certain sets of motions But, there are only certain sets of motions that are self-consistentthat are self-consistent

Gravity is a natural consequence of a self-Gravity is a natural consequence of a self-consistent string theory – it is not consistent string theory – it is not something that is added on latersomething that is added on later

Self-consistent string theories only exist in 10 or 26 dimensions – enough mathematical space to create all the particles and interactions that we

have observed


Superstring DimensionsSuperstring Dimensions

Since we can observe Since we can observe only 3 spatial and 1 only 3 spatial and 1 time dimensions, the time dimensions, the extra 6 dimensions (in extra 6 dimensions (in a 10D string theory) a 10D string theory) are curled up to a very are curled up to a very small sizesmall size

The shape of the The shape of the curled up dimensions curled up dimensions is known is known mathematically as a mathematically as a Calabi-Yau spaceCalabi-Yau space


Superstring UniverseSuperstring Universe

At each point in 3D space, the extra At each point in 3D space, the extra dimensions exist in unobservably small dimensions exist in unobservably small Calabi-Yau shapesCalabi-Yau shapes


Superstring TheoriesSuperstring Theories There are at least five different versions of string There are at least five different versions of string

theory, which seem to have different propertiestheory, which seem to have different properties As physicists began to understand the As physicists began to understand the

mathematics, the different versions of the mathematics, the different versions of the theories began to resemble each other theories began to resemble each other (“duality”)(“duality”)

In 1995, Edward Witten showed how all five In 1995, Edward Witten showed how all five versions were really different mathematical versions were really different mathematical representations of the same underlying theoryrepresentations of the same underlying theory

This new theory is known as M-theory (for This new theory is known as M-theory (for Mother or Membrane)Mother or Membrane)


M-TheoryM-Theory

Unification of Unification of five different five different types of types of superstring superstring theory into one theory into one theory called M-theory called M-theorytheory

M-theory has M-theory has 11 dimensions11 dimensions


Some questionsSome questions

Can we find the underlying physical principles Can we find the underlying physical principles which have led to us to string theory?which have led to us to string theory?

Does the correct string (or membrane) theory Does the correct string (or membrane) theory have 10 or 11 dimensions?have 10 or 11 dimensions?

Will we ever be able to find evidence for the curled Will we ever be able to find evidence for the curled up dimensions?up dimensions?

Is string theory really the long-sought “Theory of Is string theory really the long-sought “Theory of Everything”?Everything”?

Will any non-physicists ever be able to understand Will any non-physicists ever be able to understand string theory?string theory?

Hear and see Brian Greene in NOVA’s “Elegant Hear and see Brian Greene in NOVA’s “Elegant Universe”Universe”


Web ResourcesWeb Resources

VROOM visualization of 4 dimensions http://www.evl.uic.edu/EVL/VROOM/HTML/PROJECTS/02Sandin.html

Ned Wright’s Cosmology Tutorial http://www.astro.ucla.edu/~wright/cosmolog.htm

Fourth dimension web site

http://www.math.union.edu/~dpvc/math/4D/welcome.html


Web ResourcesWeb Resources

Michio Kaku’s web site http://www.mkaku.org

E. Lowry’s EM Field in Spacetime http://www.ultranet.com/~eslowry/elmag Visualizing tensor fields http://www.nas.nasa.gov/Pubs/TechReports/RelatedPapers/StanfordTensorFieldVis/CGA93/abstract.html

Exploring the Shape of Space http://www.geometrygames.org/ESoS/index.html


Web ResourcesWeb Resources Astronomy picture of the DayAstronomy picture of the Day

http://antwrp.gsfc.nasa.gov/apod/astropix.htmlhttp://antwrp.gsfc.nasa.gov/apod/astropix.html Imagine the UniverseImagine the Universe

http://imagine.gsfc.nasa.govhttp://imagine.gsfc.nasa.gov Center for Particle Astrophysics Center for Particle Astrophysics

http://cfpa.berkeley.edu/http://cfpa.berkeley.edu/ Dark Matter telescope Dark Matter telescope

http://www.dmtelescope.org/darkmatter.hthttp://www.dmtelescope.org/darkmatter.htmlml

Dark Matter Activity #2Dark Matter Activity #2 http://universe.sonoma.edu/materials/lesson_planshttp://universe.sonoma.edu/materials/lesson_plans/dark_matter.html/dark_matter.html


Web ResourcesWeb Resources Jonathan Dursi’s Dark Matter Tutorials & Jonathan Dursi’s Dark Matter Tutorials &

Java applets Java applets http://www.astro.queensu.ca/~dursi/dm-tutorial/dhttp://www.astro.queensu.ca/~dursi/dm-tutorial/dm0.htmlm0.html

MACHO projectMACHO project http://wwwmacho.mcmaster.ca/ http://wwwmacho.mcmaster.ca/ National Center for Supercomputing National Center for Supercomputing

Applications Applications http://www.ncsa.uiuc.edu/Cyberia/Cosmos/http://www.ncsa.uiuc.edu/Cyberia/Cosmos/MystDarkMatter.htmlMystDarkMatter.html

Pete Newbury’s Gravitational Lens movies Pete Newbury’s Gravitational Lens movies http://www.iam.ubc.ca/~newbury/lenses/rehttp://www.iam.ubc.ca/~newbury/lenses/research.htmlsearch.html


Web ResourcesWeb Resources Alex Gary Markowitz’ Dark Matter Alex Gary Markowitz’ Dark Matter

Tutorial Tutorial http://www.astro.ucla.edu/~agm/darkmtr.htmlhttp://www.astro.ucla.edu/~agm/darkmtr.html

Martin White’s Dark Matter ModelsMartin White’s Dark Matter Models http://cfa-www.harvard.edu/~mwhite/http://cfa-www.harvard.edu/~mwhite/modelcmp.htmlmodelcmp.html

Livermore Laboratory axion searchLivermore Laboratory axion search http://www-phys.llnl.gov/N_Div/Axion/axion.htmlhttp://www-phys.llnl.gov/N_Div/Axion/axion.html

Dark Matter Activity #1 Dark Matter Activity #1 http://www.astro.washington.edu/labs/clearinghhttp://www.astro.washington.edu/labs/clearinghouse/labs/Darkmatter/ouse/labs/Darkmatter/

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