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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 23 & 24 Papers Paper 1 is done Paper 2 grades are on eLearning All grades fixed, revision paper grades posted Paper 3: We have fixed papers for calibration problems Still mis-graded? Let us know!

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papers
Papers
  • Paper 1 is done
  • Paper 2 grades are on eLearning
    • All grades fixed, revision paper grades posted
  • Paper 3:
    • We have fixed papers for calibration problems
    • Still mis-graded? Let us know!
    • Do CPR if you submitted a revision
  • Paper 4:
    • Was due today before class
  • Paper 5 (last paper, no final)
    • Assigned after we start Chap 20
other stuff
Other Stuff
  • Elearning:
    • Unit 5 has Unit 6 questions (sigh…)
    • 5 and 6 will both be due last day of class
  • Schedule from here on out
    • Today: Ch 19 & 20 (paper 4 due)
    • Wed Apr 21: No class, Muster
    • Mon Apr 26: Ch 20 &21 (paper 4 CPR due)
    • Wed Apr 28: Ch 21 & 22
    • Mon May 3: Ch 22 (last day of class, paper 5 due)

3

the reading for unit 6
The Reading for Unit 6

Full reading for Unit 6:

  • BBBHNM: Chaps. 18-22
  • SHU: 8 (159-164)
  • BHOT: 11 (122-137), 12
  • Seeds (Cosmology in the 21st Century, Web Handout)

Full reading through Unit 6:

  • BBBHNM: Chaps. 1-22
  • TFTM: Chaps. 1-5
  • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12
  • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164)
  • TOE: Chaps. 1-3
  • Seeds (Cosmology in the 21st Century)
unit 6
Unit 6

Going back in time and going forward in time

Before the first millionth of a second

and the

Fate of the Universe

outline of unit 6
Outline of Unit 6
  • Possible Fates of the Universe
  • The Case for Dark Matter
  • Particle Physics and Dark Matter
  • Inflation
  • Dark Energy

Today

summarizing the data so far
Summarizing the Data so Far
  • Redshifts of Galaxies gives us the speed of expansion fairly accurately
  • The measured mass of the “stars and stuff” gives about 4% of the critical density
  • The Cosmic Background Radiation is consistent with a density of 100% of the critical density

Something is inconsistent…

the story
The Story

There is a strong case to be made that there is Matter and Energy in the Universe we can’t “see” directly

  • The Evidence for Dark Matter
    • Today
  • Particle Physics and Dark Matter
    • The Standard Model and Supersymmetry
    • Next time
today s lecture
Today’s Lecture

The Case for Dark Matter

  • The Rotation of Galaxies
  • Gravitational Lensing
  • Colliding Galaxies

Note: SHU is a little out of date…

what is dark matter and why do we call it dark matter
What is Dark Matter and why do we call it Dark Matter?

What do we see when we look at the Heavens?

  • Our eyes see photons, but with other detectors we can see electrons, protons, atoms and neutrinos
  • All these things interact with photons  we can “see” them because they produce the light we observe
dark matter
Dark Matter
  • If there is something else out there it must not interact with light very much
  • Call this “Dark Matter”
evidence 1
Evidence 1

Watch the way stars rotate around the center of Galaxies

the planets and the sun
The Planets and the Sun

General Relativity does a good job of predicting the planets path around the sun assuming virtually all the mass of the Solar system is located at the Sun

  • Only small influence due to the small masses of the other planets
what about stars and galaxies
What about Stars and Galaxies?
  • Can again use General Relativity to predict the orbits of stars as they move around the galaxy
  • Should look like a complex collection of individual stars all in separate free orbits around the heart of the galaxy
  • Problem: This isn’t what the data shows
does this work for stars
Does this work for Stars?

Watch how fast a star rotates around the center of the galaxy…

Simulation without

Dark Matter

Simulation with lots of

Dark Matter particles in the galaxy

Data looks like this

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gif

stuff outside the stars
Stuff Outside the Stars?
  • Can also look at the clouds of hydrogen on the outskirts of the galaxy
  • Also rotating faster than they should be
  • Looks like they are feeling the gravity of a large amount of mass we can’t “see”
dark matter18
Dark Matter?

Data well explained by lots of “Dark Matter” we can’t see

Mostly clumped at the center due to gravity

Lots of it in a “halo” around the entire galaxy

evidence 2
Evidence 2

Look at the gravitational impact on light that travels through the Universe towards us

general relativity and light
General Relativity and Light
  • The large mass of the Sun can bend the path of light
  • Result: The apparent position of a star “moved” as the light passed from outer space, past the Sun, and to us

Is here

“Looks” like its here

Light’s path in curved

space time

looking at light from the universe
Looking at Light from the Universe

Galaxy

Light from a Galaxy

Another Galaxy

Hydrogen

Cloud

Looks like a Galaxy behind a cloud of heavy “stuff” that isn’t just stars and hydrogen

Looks like a Galaxy behind a cloud of hydrogen

Looks like a Galaxy

lensing of galaxies
Lensing of Galaxies

Prism

  • Dark Matter “Lenses” the galaxies behind them like a prism
  • Evidence that the light coming to us is passing through lots of matter we can’t see directly
more on lensing
More on Lensing

Sometimes we can even see more than one image of the same galaxy!

evidence 3
Evidence 3

Colliding Clusters of Galaxies

look at colliding clusters of galaxies
Look at Colliding Clusters of Galaxies

Atoms in the Galaxies interact and slow down as they pass through each other

Atoms

Atoms

Dark Matter doesn’t interact much so it isn’t slowed down much

Dark Matter

Dark Matter

colliding galaxy clusters
Colliding Galaxy Clusters

The atom part and the Dark Matter part of Galaxies interact differently as they pass through each other

Atoms and

Dark Matter

Atoms and

Dark Matter

Atoms

Atoms

Dark Matter

Dark Matter

colliding galaxy clusters27
Colliding Galaxy Clusters

Galaxy

Galaxy

Galaxy

Light from a Galaxy

Atoms and

Dark Matter

Atoms and

Dark Matter

Atoms

Atoms

Dark Matter

Dark Matter

evidence for this in nature
Evidence for This in Nature?

Colliding Clusters of Galaxies

Blue is the part from lensing only

“Fast  Dark Matter”

Red part from observing the light

“Slow Atoms”

slide29

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/dark_matter_lg.mpghttp://bigbang.physics.tamu.edu/Figures/StolenAnimations/dark_matter_lg.mpg

slide30

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/bullett_anim_lg.mpghttp://bigbang.physics.tamu.edu/Figures/StolenAnimations/bullett_anim_lg.mpg

slide31
What IS Dark Matter?

We don’t know…

Still working on it…

for next time
For Next Time

Could the Dark Matter just be a bunch of a single type of new fundamental particle?

  • Chap 20: Particle Physics
    • The Standard Model of Particle Physics
    • Supersymmetry

Full reading for Unit 6:

  • BBBHNM: Chaps. 18-22
  • SHU: 8 (159-164)
  • BHOT: 11 (122-137), 12
  • Seeds (Cosmology in the 21st Century, Web Handout)

Full reading through Unit 6:

  • BBBHNM: Chaps. 1-22
  • TFTM: Chaps. 1-5
  • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12
  • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164)
  • TOE: Chaps. 1-3
  • Seeds (Cosmology in the 21st Century)

Lecture prep: Turn in on eLearning

Two questions from Chapter 20 you want to know the answer to

evolution of the universe
Evolution of The Universe

Put it all together and there is significant evidence that there is LOTS of dark matter in the Universe

writing assignments
Writing Assignments

Short Assignments 1, 2 & 3

Re-do’s are still possible. Want to revise again? Talk to me

eLearning:

Unit 5 past due

Need to be working on Unit 6

35

last paper
Last Paper

Due last day of class

If you did the Black Hole paper your paper is posted now, on Dark Matter

If you did not do the Black Hole paper you must turn in a Research Paper

Turn in at eLearning like usual

36

ok what does it look like
Ok… What Does it Look Like?
  • Stars look more like they are turning as if they are part of a single solid, giant wheel
  • Looks like this wheel would be MUCH more massive than the sum of all the stars in the galaxy
  • Also, much more spread out than most of the mass at the center
does this work for stars38
Does this work for Stars?

Watch how fast a star rotates around the center of the galaxy…

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gif

evidence 4
Evidence 4
  • Is the universe made up of just the known particles?
    • Electrons?
    • Protons?
    • Neutrons?
    • Neutrinos?
  • Perhaps its just known particles we can’t see?
    • The Earth doesn’t shine…
composed of normal matter
Composed of Normal Matter?

0

  • Lots of “protons and neutrons” we can’t see?
  • Look at the amount of Deuterium and Lithium in the Universe
  • The data predict that normal matter is only ~4% of the critical density
  • Consistent with other observations
does this work for stars41
Does this work for Stars?

Watch how fast a star rotates around the center of the galaxy…

does this work for stars42
Does this work for Stars?

Watch how fast a star rotates around the center of the galaxy…

how the earth looks to light
How the Earth looks to Light…

Path

doesn’t curve

Path

does curve

slide45
Need a picture here…
  • TCP Figure 21.1, page 614 ?
  • Shockwave video comparing galaxy rotation with and without dark matter
dark matter46
Dark Matter

0

  • Combined mass of all “visible” matter (i.e. emitting any kind of radiation) in the universe adds up to much less than the critical density.
  • Gravitational lensing shows that some clusters contain 10 times as much mass as is directly visible.
slide47
From this we can conclude (but not prove) that much of our galaxy’s mass must lie beyond the distance of the Sun’s orbit around the galactic center, and distributed throughout the galaxy’s spherical halo
  • Most of the light comes from the center
  • Thus, there is a large amount of matter that we can’t see
rotation stuff
Rotation Stuff
  • However, there is lots of “dark matter” that we cannot see directly but which we know must be there
shu 8 cont
SHU 8 cont…
  • This “dark, unseen matter must have so much mass that it held the stars in position, making them the shining hub of a giant invisible wheel”
tcp 21
TCP 21
  • One of our favorite reasons is to look at the atomic hydrogen clouds in the Milky Way.
  • The clouds lay very far out from the galactic center (further out than our sun) and are rotating faster than they should be if they were just feeling the gravity of the mass we can “see”
slide51
There had to be part of the galaxy which were just not seeing, and that this must make up far more of the total mass of the galaxy than the stars we could observe shining
why do we believe
Why do we believe?
  • Why do we believe there is other stuff out there that we can’t see?
  • Three reasons
    • The way stars rotate around the center of Galaxies
    • Look at the gravitational impact on light that travels through the Universe towards us
    • Colliding Galaxies
two topics
Two Topics

We can use the evidence that we live in a Flat, Homogenous and Isotropic Universe as evidence for two main things

  • Other Mass/Energy in the Universe (This Time)
  • Inflation (Coming Soon)
slide54
Evidence that we live in a Flat, Homogenous and Isotropic Universe and its implications
  • If we live in a flat Universe where is the rest of the Mass/Energy that makes up the rest of the “critical Density”
  • Missing Mass and Energy in the Universe and the case for Dark Matter
outline
Outline
  • SHU 8 first part
  • TCP 21, but not really…
slide56
“If you assumed that all the stars we can see in the galaxy are free to affect each other gravitationally in exactly the same way gravity governs the dynamics of the solar system, then our galaxy should rotate differently than we observe them to…
baryonic dark matter
Baryonic Dark Matter

0

Nature of baryonic dark matter still very uncertain and speculative.

One component: MAssive Compact Halo Objects = “MACHOs”:

Brightness of background star

Small compact objects (e.g., brown dwarfs, small black holes) acting as gravitational lenses.

Time

Distant background star

Earth

MACHO

tcp 21 cont
TCP 21 cont…
  • The universe has two possible fates: It might continue to expand forever, or it might someday stop expanding and begin to collapse
  • We don’t yet know the fate of the universe because the answer depends on the overall density of matter in the universe – and we cannot determine the overall density until we first determine how much dark matter is out there
  • Finished?