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THE DARK SIDE OF THE FORCE -THE DARK SIDE OF THE FORCE -Black Holes and Dark Matter
THE DARK SIDE OF THE FORCE -THE DARK SIDE OF THE FORCE -Black Holes and Dark Matter
Weldon J. Wilson
Department of Physics & Engineering
University of Central Oklahoma
Weldon J. Wilson
Department of Physics & Engineering
University of Central Oklahoma
PlanetsComets StarsGalaxiesIs there material that does not emit or absorb light?
Yes!
Historically, astronomers have harvested lightHistorically, astronomers have harvested light
Dark MatterDark Matter
What is it made of? We don’t know
How much is there? Most of the Universe!
What is it made of? We don’t know
How much is there? Most of the Universe!
Particle Physics
CosmologyAstronomy
How do we know?How do we know?
“We see it as Columbus saw America from the shores of Spain. Its movements have been felt, trembling along the far-reaching line of our analysis, with a certainty hardly inferior to that of ocular demonstration”
Sir John Herschel (referring to evidence for
Neptune, 150 years ago)
“We see it as Columbus saw America from the shores of Spain. Its movements have been felt, trembling along the far-reaching line of our analysis, with a certainty hardly inferior to that of ocular demonstration”
Sir John Herschel (referring to evidence for
Neptune, 150 years ago)
Rotation Curves of Spiral GalaxiesRotation Curves of Spiral Galaxies
NGC 253 Spiral galaxies like our own Milky Way are rotating.
The rate of rotation can be measured, and used to determine the mass of the galaxy.
Spiral galaxies like our own Milky Way are rotating.
The rate of rotation can be measured, and used to determine the mass of the galaxy.
(David Malin, AAO)
The stars in a typical galaxy comprise at most 10% of its mass!
The stars in a typical galaxy comprise at most 10% of its mass!
Revised notion of a galaxy Revised notion of a galaxy
With our Dark Matter glasses on:With our Dark Matter glasses on:
A cosmological Rosetta stone? A cosmological Rosetta stone? Dark Matter
• governs the majestic rotation of galaxies• seeds the evolution of cosmic structures• determines the fate of the Universe
Dark Matter• governs the majestic rotation of galaxies• seeds the evolution of cosmic structures• determines the fate of the Universe
Understanding the nature and distribution of Dark Matter is one of the most pressing open
questions in the physical sciences today
Understanding the nature and distribution of Dark Matter is one of the most pressing open
questions in the physical sciences today
The Mass Budget of the UniverseThe Mass Budget of the Universe
“Critical” density“Critical” density
Stars, less than 1% of critical densityStars, less than 1% of critical density
Ordinary (“Baryonic”)
Matter, at most 10%of critical density
Ordinary (“Baryonic”)
Matter, at most 10%of critical density
closed
open
“Best Guess” Density of the Universe“Best Guess” Density of the Universe
What is the Galactic Dark Matter?What is the Galactic Dark Matter?
Exotic Particles New Physics!
Exotic Particles New Physics!
Ordinary Matter
Ordinary Matter
StarsStars
Gas,DustGas,Dust
MAssiveCompactHaloObjects Jupiters? Black Holes? Brown Dwarfs?
MAssiveCompactHaloObjects Jupiters? Black Holes? Brown Dwarfs?
Massive NeutrinosMassive Neutrinos
AxionsAxions
WeaklyInteractingMassiveParticles
WeaklyInteractingMassiveParticles
????
Searching for Particle Physics Dark MatterSearching for Particle Physics Dark Matter• Direct Detection of WIMPs• Direct Detection of Axions • Fossil Record - tracks in mica• Neutrino experiments:
1) Do neutrinos have a non-zero mass?
2) Searches for annihilation decay products
• Direct Detection of WIMPs• Direct Detection of Axions • Fossil Record - tracks in mica• Neutrino experiments:
1) Do neutrinos have a non-zero mass?
2) Searches for annihilation decay products
DM + DM neutrinosDM + DM neutrinos
Experimental Challenges: low ratebackground discrimination
Thermal and ionization signature in laboratory apparatus
Deep underground cryogenic experiment
Experimental Challenges: low ratebackground discrimination
Thermal and ionization signature in laboratory apparatus
Deep underground cryogenic experiment
Searching for WIMPs Searching for WIMPs
Is the mass of the neutrino exactly zero?Is the mass of the neutrino exactly zero?A new generation of experiments will determine
properties of neutrinosA new generation of experiments will determine
properties of neutrinos
SuperKamiokande, JapanSuperKamiokande, JapanSudbury NeutrinoObservatory, CanadaSudbury NeutrinoObservatory, Canada
Scanning for AxionsScanning for Axions• Specific prediction relates the axion’s mass to its interaction rate• In a strong magnetic field, axions convert to light
• Specific prediction relates the axion’s mass to its interaction rate• In a strong magnetic field, axions convert to light
superconducting magnet
sensitive detector
frequency
signal
(LLNL/MIT/Florida)
Searching for MACHOsHow do you look for something that can’t be seen?
Searching for MACHOsHow do you look for something that can’t be seen?
Use the one thing that is known about Dark Matter:
- It Gravitates!
Use the one thing that is known about Dark Matter:
- It Gravitates!
StarTelescope
MACHO
Gravitational Lensing Gravitational Lensing Within the solar system, deflection of light grazing past the
sun provides a stringent test of General Relativity Within the solar system, deflection of light grazing past the
sun provides a stringent test of General Relativity
Over cosmologicaldistances, lensing byintervening galaxiesproduces dramatic
effects
Over cosmologicaldistances, lensing byintervening galaxiesproduces dramatic
effects
From a Black Hole Not even Light Escapes
From a Black Hole Not even Light Escapes
Gravitational Lensing By a Moving Mass
The Signature of Gravitational MicrolensingThe Signature of Gravitational Microlensing
Brightness
star
The Signature of Gravitational MicrolensingThe Signature of Gravitational Microlensing
Brightness
star
speed mass
duration depends on speed and mass of MACHO
peak depends on how close it passes to line of sight
MACHO
Gravitational Microlensing by MACHOsGravitational Microlensing by MACHOs
Unlikely! One star in a million is lensed at any given time
Distinctive signature is a brightening of a background star
Unlikely! One star in a million is lensed at any given time
Distinctive signature is a brightening of a background star
Requires a population of stars just outside the Galactic dark halo, but close enough to monitor individual starsRequires a population of stars just outside the Galactic dark halo, but close enough to monitor individual stars
you arehere
MACHO Project - lines of sightMACHO Project - lines of sight
towards GalacticCenter
(M65, David Malin, AAO)
towards Large Magellanic Cloud
you arehere
The Needle in the HaystackThe Needle in the Haystack
Single Image 77 Mbytes = 3 Seattle phone books
Typical night 5,000 Mbytes = 200 phone books!
Total to date 5,000 Gbytes = 200,000 phone books
More repeated measurements of stars than the entire cumulative previous history
of astronomy
More repeated measurements of stars than the entire cumulative previous history
of astronomy
The MACHO Project - Data AnalysisThe MACHO Project - Data Analysis
77 Mbytesper frame
Image Archive
Image Analysis
Database Alert System
Time Series Analysis
Many stars are variable!Many stars are variable!Eclipsing Binary systems
Periodic variable stars
Exotic stars...
boom!
Eclipsing Binary Star System Eclipsing Binary Star System
Periodic Variable StarsPeriodic Variable Stars
Microlensing has been detectedMicrolensing has been detected
• The trick is distinguishing microlensing from intrinsic stellar variability
• More than 200 events seen towards Galactic center
• Valuable new tool for astrophysics
• The trick is distinguishing microlensing from intrinsic stellar variability
• More than 200 events seen towards Galactic center
• Valuable new tool for astrophysics
days
Am
plif
icat
ion
Gravitational Microlensing is Very UsefulGravitational Microlensing is Very Useful
• Lensed stars are brighter!
Can get detailed data
• Better detail than Hubble Space Telescope
• Mass tomography of the Galaxy
• Search for distant planets around disk stars
• Search for Dark Matter
• Lensed stars are brighter!
Can get detailed data
• Better detail than Hubble Space Telescope
• Mass tomography of the Galaxy
• Search for distant planets around disk stars
• Search for Dark Matter
Looking for Planets with MicrolensingLooking for Planets with Microlensing
• Take advantage of hundreds of events towards Galactic Center
• Planetary companions to lensing stars in Galactic disk produce excursions in light curves
• Sensitive to Earth-mass planets
• Preliminary data look encouraging
• Take advantage of hundreds of events towards Galactic Center
• Planetary companions to lensing stars in Galactic disk produce excursions in light curves
• Sensitive to Earth-mass planets
• Preliminary data look encouraging
As for the search for MACHOs...As for the search for MACHOs...
After looking at more than twenty million stars for two years - a pair of observations:
• No short events seen.
• A handful of surprisingly long events detected...
After looking at more than twenty million stars for two years - a pair of observations:
• No short events seen.
• A handful of surprisingly long events detected...
Lack of short events rules out a wide range of MACHOs being the Dark Matter
Lack of short events rules out a wide range of MACHOs being the Dark Matter
excluded
1 million timesless massive than
the sun
one tenthas massiveas the sun
Eliminating DM candidates is major progress!Eliminating DM candidates is major progress!
A detection of Dark Matter?A detection of Dark Matter? Eight microlensing events were seen in a two-year
period, after monitoring twenty million stars
This significantly exceeds the single event expected from “known” stars in the Galaxy
Eight microlensing events were seen in a two-year period, after monitoring twenty million stars
This significantly exceeds the single event expected from “known” stars in the Galaxy
But wait!But wait!
The PuzzleThe Puzzle
The detected events last roughly 80 days, corresponding to lenses with about 1/10th the mass of the sun
What could these things be?
If the preliminary results endure, this could be a turning point
The detected events last roughly 80 days, corresponding to lenses with about 1/10th the mass of the sun
What could these things be?
If the preliminary results endure, this could be a turning point
So, what is the matter?So, what is the matter?
The least radical option:
– MACHOs and/or massive neutrinos.
More speculative:
– exotic elementary particles never before seen
The least radical option:
– MACHOs and/or massive neutrinos.
More speculative:
– exotic elementary particles never before seen
We live in a special time in human history
We live in a special time in human history
Some of the most fundamental questions in cosmology are being successfully addressed by experiments.
The measurements are difficult, with results that sometimes appear contradictory.
A much more complete understanding will take shape in the decade to come.
Some of the most fundamental questions in cosmology are being successfully addressed by experiments.
The measurements are difficult, with results that sometimes appear contradictory.
A much more complete understanding will take shape in the decade to come.
The FutureThe Future
Next-generation microlensing projects,
along new lines of sight
Next-generation microlensing projects,
along new lines of sight
Other observationalcosmology projectsOther observationalcosmology projects
Results fromWIMP and Axion
Searches
Results fromWIMP and Axion
Searches
Neutrino ResultsNeutrino Results
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