THE DARK SIDE OF THE FORCE -Black Holes and Dark MatterWeldon J. Wilson

Department of Physics & EngineeringUniversity of Central Oklahoma

Historically, astronomers have harvested lightIs there material that does not emit or absorb light?Yes!

Dark Matter

What is it made of? We dont knowHow much is there? Most of the Universe!

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)

Rotation Curves of Spiral GalaxiesNGC 253Spiral 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)

Revised notion of a galaxy

With our Dark Matter glasses on:

A cosmological Rosetta stone? Dark Mattergoverns the majestic rotation of galaxiesseeds the evolution of cosmic structuresdetermines the fate of the Universe

The Mass Budget of the UniverseCritical densityStars, less than 1% of critical densityOrdinary (Baryonic) Matter, at most 10%of critical densityBest Guess Density of the Universe

What is the Galactic Dark Matter?

Searching for Particle Physics Dark MatterDirect Detection of WIMPsDirect Detection of Axions Fossil Record - tracks in micaNeutrino experiments: 1) Do neutrinos have a non-zero mass? 2) Searches for annihilation decay products

Searching for WIMPs Experimental Challenges: low ratebackground discrimination

Thermal and ionization signature in laboratory apparatus

Deep underground cryogenic experiment

Is the mass of the neutrino exactly zero?A new generation of experiments will determine properties of neutrinosSuperKamiokande, JapanSudbury NeutrinoObservatory, Canada

Scanning for AxionsSpecific prediction relates the axions mass to its interaction rateIn a strong magnetic field, axions convert to lightsuperconducting magnetsensitive detectorfrequencysignal(LLNL/MIT/Florida)

Searching for MACHOsHow do you look for something that cant be seen? Use the one thing that is known about Dark Matter: - It Gravitates!

Gravitational Lensing Within the solar system, deflection of light grazing past the sun provides a stringent test of General RelativityOver cosmologicaldistances, lensing byintervening galaxiesproduces dramaticeffects

From a Black Hole Not even Light Escapes

Gravitational Lensing By a Moving Mass

The Signature of Gravitational MicrolensingBrightnessstar

The Signature of Gravitational MicrolensingBrightnessstar

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 Requires a population of stars just outside the Galactic dark halo, but close enough to monitor individual stars

MACHO Project - lines of sight(M65, David Malin, AAO)you arehere

The Needle in the HaystackMore repeated measurements of stars than the entire cumulative previous historyof astronomy

The MACHO Project - Data Analysis

Many stars are variable!Eclipsing Binary systems

Periodic variable stars

Exotic stars...

Eclipsing Binary Star System

Periodic Variable Stars

Microlensing has been detectedThe trick is distinguishing microlensing from intrinsic stellar variabilityMore than 200 events seen towards Galactic centerValuable new tool for astrophysics

daysAmplification

Gravitational Microlensing is Very UsefulLensed stars are brighter! Can get detailed data Better detail than Hubble Space TelescopeMass tomography of the Galaxy Search for distant planets around disk starsSearch for Dark Matter

Looking for Planets with MicrolensingTake advantage of hundreds of events towards Galactic CenterPlanetary companions to lensing stars in Galactic disk produce excursions in light curvesSensitive to Earth-mass planetsPreliminary 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...

Lack of short events rules out a wide range of MACHOs being the Dark MatterEliminating 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 But wait!

The PuzzleThe 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

We live in a special time in human historySome 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

Good Evening

My name is Christopher Stubbs. I am a professor in the Department of Astronomy and the Department of Physics here at the University of Washington. Tonight I am going to speak about one of the most important unanswered questions in the physical sciences-What is the Universe made of?

Right now, we dont know

Much effort

harvested lightBountiful harvest!start within the solar system#1: Planets- reflected sunlight#2- comets#3- stars#4- galaxiesmade up of starsdust lane- absorption#5- is there matter that does not emit or absorb much light

Previous example of detecting something through its gravitational effect- the Planet Neptune

Similarly, evidence for dark matter comes from seeing its gravitational influence on its surroundings.

#1Spiral galaxies are rotating

#2 Rate of rotation to measure mass

#3 Stars are 10% of massData Firehose

Single image = 3 phone books, etc.

Roughly one star equiv to one listing in phone book

variables = 1 page

microlensing = 1 entry, out of a phone book.