Transcript Galaxies: 33.1

GALAXIES
By
Christopher Wrobleski
&
Patrick Bradford Poole
What are Galaxies?
• A component of our
universe made up of
gas and a large
number of stars held
together by gravity.
Types of Galaxies
Spiral
Lenticular
Elliptical
Irregular
Spiral
Two major components:
1.) A flat large disk
2.) Young Star Clusters
Forms distinct spiral patterns.
The Milky Way
• The Milky Way is our galaxy.
• ~ 200,000,000,000 make up the M.W.
– Our sun is one of them.
– The sun is 2/3 away from the center.
Like other spiral galaxies, it
has several parts; disk,
bulge, and halo.
Milky Way (cont.)
• It would take 100,000 light
years to cross the MW.
• Using visible light, we
cannot see the center of the
galaxy. Therefore,
astronomers have to use
other wavelengths to make
observations. This picture
was taken with light from
the infrared region of the
electromagnetic spectrum.
Lenticular
• The lenticular
galaxies are disk
galaxies without any
conspicuous
structure in their
disks.
Elliptical
Football shaped
Little or no global angular momentum
Irregular
Do not fit any
of the other categories.
Chaotic in appearance.
Make up about 25% of the galaxies.
Active Galaxies
• Active galaxies are
intensely studied at all
wavelengths.
• They can change their
behavior on short
timescales.
A diagram of an active
galaxy, showing the primary
components.
Seyfert Galaxies
• Unusually bright,
compact nuclei.
Radio Galaxies
• Extensive double radio
sources, shining by
synchrotron radiation
as electrons spiral
through magnetic
fields at relativistic
speeds.
Quasars
The only interesting
thing about quasars is
their spectrum.
z = (Observed wavelength - Rest wavelength)/(Rest wavelength)
Mass of Our Galaxy
The Milky Way
Estimate the total mass of our Galaxy using
the orbital data of the Sun (including our
solar system) about the center of the
Galaxy. Assume that most of the mass of
the Galaxy can be approximated as a
uniform sphere of mass (the center bulge).
EXAMPLE 33-1, pg. 1001
The Dark Matter
• It’s a lot of different stuff, from tiny
subatomic particles to black holes.
Massive Astrophysical Compact Halo Objects
Weakly Interacting Massive Particles
MACHOs
• Strong dark matter
objects ranging in size
from small stars to
super massive black
holes.
• Made of baryonic
matter.
• Make up the halos
around galaxies.
Brown Dwarfs Vs. Black Holes
•
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Made out of hydrogen--the same
as our sun but they are typically
much smaller.
Stars like our sun form when a
mass of hydrogen collapses under
its own gravity and the intense
pressure initiates a nuclear
reaction, emitting light and
energy.
Brown dwarfs are different from
normal stars, because of their
relatively low mass,
Brown dwarfs do not have
enough gravity to ignite when
they form.
Brown dwarfs give off some heat
and a small amount of light.
• Have an over-abundance of
matter.
• All that matter "collapses"
under its own enormous
gravity into a relatively small
area.
• Extremely strong
gravitational field.
• Stars at safe distance will
circle around the black hole.
• Black holes emit no light; they
are truly black.
References
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http://seds.lpl.arizona.edu/messier/galaxy.html
http://zebu.uoregon.edu/galaxy.html
http://www.damtp.cam.ac.uk/user/gr/public/gal_home.html
http://www.smv.org/hastings/student2.htm
http://csep10.phys.utk.edu/astr162/lect/
http://www.astr.ua.edu/keel/galaxies/
http://imagine.gsfc.nasa.gov/docs/science/know_l1/active_galaxies.html
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