Download Chapter 15 and 16: Discovering Galaxies

Chapter 15 and 16: Discovering Galaxies
The Milky Way Galaxy
Whenever life gets you down, Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious or daft,
And you feel that you've had quite eno-o-o-o-o-ough...
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the "Milky Way".
Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.
Galaxies seem to take one of four
different appearances
SPIRALS
Galaxies seem to take one of four
different appearances
BARRED SPIRALS
Edge on Spiral
Galaxies seem to take one of four
different appearances
Type E0
Type E3
ELLIPTICALS
Type E6
Galaxies seem to take one of four
different appearances
IRREGULAR
Galaxies that look like merger
remnants
Galaxy Mergers
Mergers cause the shapes of galaxies to change over time.
Galaxy Classification
A
B
C
D
E
F
Our View of the Milky Way
Galaxy
Our Milky Way Galaxy?
This object
that looks
like a star
must be
enormously
luminous –
because it is
4 billion
light years
away!!
What are Quasars?
Quasars get their energy from swallowing up matter in the accretion disk
Quasars and other Active Galaxies
90% of a Galaxy is Dark Matter!
Measuring the amount of Dark Matter in the
Universe: Gravitational Lensing
Perfectly Aligned
Slightly Misaligned
Einstein’s General Theory of Relativity says that
light from a distant object gets bent when it
passes through a gravitational field of an
intervening object.
Gravitational lensing
Gravitational Lensing:
Evidence for dark matter
The Birth and Life of Galaxies
View of the Early Universe with WMAP (2003)
Early Universe showed slight variations in density!
Are the density variations the seeds of galaxy formation??
Now the popular choice for galaxy formation!
Young Galaxies
• smaller
• bluer
• more
irregular
• higher star
forming
rates
Galaxies as they appeared more than 10 billion years ago.
Galaxies are Grouped in Clusters
Now the popular choice for galaxy formation!
The Local Group
The Local Group
The Local Super Cluster
Large-Scale Structure in the
Universe
Superclusters,
walls,
and voids
dominate the
large scale
structure
of the Universe