The Dark Side of the Universe Lecture 26. Homework R ead Ch. 24: Life in the Universe H W:...
33
The Dark Side of the Universe Lecture 26
-
Upload
trevor-morgan -
Category
Documents
-
view
213 -
download
0
Transcript of The Dark Side of the Universe Lecture 26. Homework R ead Ch. 24: Life in the Universe H W:...
The Dark Side of
the Universe
Lecture 26
Homework
• Read Ch. 24: Life in the Universe• HW: MasteringAstronomy Chapter 24
Final Exam
• Time: Thursday, Dec 13 at 11:30am in VLSB2050.
Topics: - 25% material covered before midterm 1. - 25% material covered between midterms 1 and 2. - 50% material covered after midterm 2.
Review Session: Tuesday, Dec 4 at 5pm in VLSB2050 (same room)
Discussion Sectionsand Office Hours
4
Student Evaluations
• Thank you for evaluating the course
and me (Prof. Geoff Marcy)!
Instructor: Geoff Marcy
Course: C12
Semester: Fall 2012
5
The Dark Side of
the Universe
Lecture 26
Most of the Universe is Dark
You, me, stars, grey matter,white matter,antimatter…
Example 1: Stars would be moving too fast
if there were only luminous matter
How do we know the Universe is Dark?
Solar System:
“Keplerian orbits”
Earth
Jupiter
Mercury
How do we know the Universe is Dark?
Galaxies:
“Flat rotation curve”
Example 1: Stars would be moving too fast
if there were only luminous matter
Example 2: Bending of light - gravitational lensing
How do we know the Universe is Dark?
How do we know the Universe is Dark?
Four images of the same galaxy
How do we know the Universe is Dark?
How do we know the Universe is Dark?
How do we know the Universe is Dark?
CMB: very cold (-270.275 C, -454.495 F) and nearly uniform relic radiation left over from the hot big bang
Example 3: Cosmic Microwave Background
How do we know the Universe is Dark?
(1965)
If you had microwave eyes:
Example 3: Cosmic Microwave Background
How do we know the Universe is Dark?
17
(1992)
(2010)
White points:
WMAP (2010)
7-year data
Red curve: Theoretical prediction for a universe made of73% dark energy, 23% dark matter, 4% atoms
How do we know the Universe is Dark?
19
Example 4: Distant supernovae
After
Before
How do we know the Universe is Dark?
Example 4: Distant supernovae are standard candles
How do we know the Universe is Dark?
Example 4: Distant supernovae are standard candles
How do we know the Universe is Dark?
Concordance region:
73% dark energy23% dark matter
4% atoms
How do we know
the Universe is Dark?
Kowalski et al (2008)
Dark Energy
Dark Matter
Supernovae probe
CMB probes
What can dark matter be?
Not enough mass: even Jupiter weighs only
0.1% of the Sun
Rocks, gas, oceans are all made of quarks.
The “normal” stuff cannot be > 4%.
Planets?
What can dark matter be?
Graveyards of massive stars, but massive stars are rare and made of normal atoms.
Once formed, black holes suck in normal matter.
So you can’t hide much dark matter in it.
Black Holes?
What can dark matter be?
Antimatter and matter annihilate each other into flashes of easily detectable gamma rays
Anti-matter?
Hardly “dark” !
Antimatter and matter have identical mass but opposite quantum numbers (electric charge, spin…)
Recall PET = Positron Emission Tomography
What can dark matter be?
Top candidate:
WIMPs
Direct Detection: CDMS-II, Edelweiss etc
Accelerator: Large Hadron Collider
But it takes more than wimps to find WIMPs!
Cryogenic Dark Matter Search
28
Supernova Explosionsas
Standard Candles
The distance to the galaxy that contains the supernova: Compare how bright they know the explosion should be with how bright the explosion appears. Using the inverse square law of light, they can compute the distance to the supernova and thus to the supernova's home galaxy.
Type Ia supernovae, which give off a standard amount of light.
30
Accelerating Expansion of the Universe:Dark Energy
31
LargeHadronCollider
(17 mile tunnel)
Most of the Universe is Dark???
You, me, stars, grey matter,white matter,antimatter…
WIMPS ?
