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

Planets Comets Stars Galaxies Is there material that does not emit or absorb light? Yes! Historically, astronomers have harvested light

Dark 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? “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 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

With our Dark Matter glasses on:

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

The Mass Budget of the Universe “Critical” density Stars, less than 1% of critical density Stars, 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? Exotic Particles New Physics! Exotic Particles New Physics! Ordinary Matter Ordinary Matter Stars Gas, Dust Gas, Dust MAssive Compact Halo Objects Jupiters? Black Holes? Brown Dwarfs? MAssive Compact Halo Objects Jupiters? Black Holes? Brown Dwarfs? Massive Neutrinos Massive Neutrinos Axions Weakly Interacting Massive Particles Weakly Interacting Massive Particles ??

Searching 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 neutrinos

Experimental Challenges: low rate background discrimination Thermal and ionization signature in laboratory apparatus Deep underground cryogenic experiment Experimental Challenges: low rate background discrimination Thermal and ionization signature in laboratory apparatus Deep underground cryogenic experiment Searching for WIMPs

Is the mass of the neutrino exactly zero? A new generation of experiments will determine properties of neutrinos SuperKamiokande, Japan Sudbury Neutrino Observatory, Canada Sudbury Neutrino Observatory, Canada

Scanning 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 MACHOs How 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! Star Telescope MACHO

Gravitational Lensing Within the solar system, deflection of light grazing past the sun provides a stringent test of General Relativity Over cosmological distances, lensing by intervening galaxies produces dramatic effects Over cosmological distances, lensing by intervening galaxies produces dramatic effects

From a Black Hole Not even Light Escapes

Gravitational Lensing By a Moving Mass

The Signature of Gravitational Microlensing Brightness star

The 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 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 stars you are here

MACHO Project - lines of sight towards Galactic Center (M65, David Malin, AAO) towards Large Magellanic Cloud you are here

The 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 Analysis 77 Mbytes per frame Image Archive Image Analysis Database Alert System Time Series Analysis

Many stars are variable! Eclipsing Binary systems Periodic variable stars Exotic stars... boom!

Eclipsing Binary Star System

Periodic Variable Stars

Microlensing 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 Amplification

Gravitational 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 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... 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 excluded 1 million times less massive than the sun one tenth as massive as the sun Eliminating DM candidates is major progress!

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!

The 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? 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 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 Future Next-generation microlensing projects, along new lines of sight Next-generation microlensing projects, along new lines of sight Other observational cosmology projects Other observational cosmology projects Results from WIMP and Axion Searches Results from WIMP and Axion Searches Neutrino Results