galaxies, dark matter and the universe
Post on 18-Dec-2014
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GALAXIES:! Island !
"Universes"!
Stephen Perrenod, Ph.D.
What is a Galaxy?
Gravitationally bound !system of:!
!Stars!
Planets!Gas!Dust!
!"Dark Matter" (mostly!)
3 Major Types of Galaxies
Elliptical - M87!!
Spiral - M101!!
Irregular - NGC1427A
Image credit: X-ray: NASA/CXC/SAO; Optical: Detlef Hartmann; Infrared: NASA/
JPL-Caltech
Our Galaxy: The Milky Way200 to 400 Billion Stars!
!A Spiral Shape!
!Size 100,000+ light-year
Diameter !(Only 1000 thickness)!
!Sun distance to center, 27,000
light-years!!
Rotates once per 240 million years
Portion of #Milky Way
NGC 6744
Milky Way!SchematicBar, Spiral Arms &!
You are Here!
Our Neighbor: Andromeda Galaxy
Distance - 2.5 Million light-years!
!Size - 220,000 light-years!
!Will collide with us in ~4
Billion years!
M31
Andromeda Attacks!
Lots of time to prepare..
The Magellanic Clouds
Southern Hemisphere objects, visible to the naked eye!
!About 200,000 light-years away!
!Large Magellanic Cloud is 14,000 light-years in size!
!Small Magellanic Cloud size is
7,000 light-years
The Local Group
Our neighborhood!!!
10 million light-years across!
!Will coalesce eventually
into one Supergalaxy!!
Rich Cluster of Galaxies~ 1000 galaxies bound together!
!Along with dark matter and gas!
!High gravitational potential heats gas to 100
million degrees!!
X-ray emission
Abell 2218
Stellar Factories
Galaxies are Huge!!
They are old ~ 13 billion years!!
They are factories for star formation and planet
formationOrion #
Nebula
Why Galaxies?
Galaxies exist so that multiple generations of stars
can be created!!
Stars exist to create elements for, and provide heat and
light to, planets!!
Planets exist as friendly abodes for life:!Including You!
Dark Matter
Our galaxy is mostly made of mysterious "Dark Matter"!
!Not stars or light-emitting
gas, but gravitational effects seen!!
All galaxies and clusters of galaxies are like this!
!Harvard computer simulation
What does "Dark Matter" mean?
Simply, matter that is hard to detect because
it doesn't emit light!!
But it has mass, so has gravitational effects!
!Thought to be some
kind of new, unknown matter
Abell 1689
Ways to Detect Dark Matter's Gravitational Effects
Galaxy rotation curves!!
Clusters of galaxies, X-ray emission!
!Gravitational lensing
How Much DM is there?
5 times as much as all ordinary matter!
What is it composed of?
We don't know!!!
NOT candidates: faint stars, black holes, dust, planets, lumps of coal!
!Candidates are all hypothetical new particles!!
!WIMPs (LSP - neutralinos)!
Axions!Sterile neutrinos
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