Download Astronomy 1

Astronomy
The scientific study of matter in
outer space, especially the
positions, dimensions,
distribution, motion, composition,
energy, and evolution of celestial
bodies and phenomena.
Big Bang–origin of the
Universe

created between 10 & 20 billion years
ago from a cosmic explosion that hurled
matter and in all directions.

initially suggested because it explains
why distant galaxies are traveling away
from us at great speeds; also predicts the
existence of cosmic background
radiation

Although widely accepted, it probably
will never be proved
http://liftoff.msfc.nasa.gov/academy/universe/b_bang.html
Galaxies

Galaxy - a massive
system of hundreds
of millions of stars,
all gravitationally
interacting, and
orbiting about a
common center.
Galaxies
Astronomers
estimate that
there are
about 125
billion
galaxies in
the universe.
Galaxies
There are two types of galaxies –
distinguished by the amount of
energy they emit:
Normal – can be thought as the total
energy they emitted (sum emitted)
from each of the stars found in the
galaxy.
Galaxies
 Active
- there is a great deal
more emitted energy than
there should be...
(this excess energy is found in
the infrared, radio, UV, and Xray regions of the
electromagnetic spectrum.)
Spiral Galaxy
has central
lens-shaped,
bright nucleus
made of
millions of
stars
¾ of galaxies
are spiral
Rotating with
2 to 4 arms
Spiral Galaxy
A Barred Spiral Galaxy:
has massive straight bar runs
through; gravitational pull from
the bar causes
interstellar gas
and dust clouds to
form a pair of
spiral arms that
extend from the
ends of the bar
Elliptical
Galaxy
shape ranges
from almost
spherical to
lens-shaped
(lenticular
galaxy)
Galaxies

Irregular
Galaxy –
uneven, cloud
of stars and
dust. i.e.
Magellanic
Clouds
Our Galaxy
Milky Way Galaxy –
 our sun is one of 100-400 billion stars.
 At least140,000 light years across
 1,000 light years thick at center
 The halo, which is a spherical cloud
surrounding the disk, contains only
about 2% as many stars as the disk. It
contains old and cool stars, since it
has little gas & dust.
 all the stars visible to the unaided eye
from Earth belong to the Milky Way
Milky Way Galaxy
What kind of galaxy
is ours?
(mass (latest value) = about 2,000,000 times that of the Sun )
Active Galaxy
Active galaxy nuclei 
There are several
types of active
galaxies: Seyferts,
quasars, and
blazars.
Quasars - An
enormously bright
object at the edge
of our universe
which emits
massive amounts of
energy. . .
Active Galaxy
Quasars – (quasi-stellar radio source)
- brightest objects in the universe
- larger and more massive than
any known star
- is considered to possibly be a
“proto-galaxy”
(we will not cover Seyferts and blazars, for more info:
http://imagine.gsfc.nasa.gov/docs/science/know_l1/active_galaxie
s.html)
.

This is what a
quasar would
look like from
here….
Go to the
www.nasa.gov
site for more
information

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The Milky Way Galaxy, commonly referred to as just the Milky
Way, or sometimes simply as the Galaxy,[a] is the home galaxy of the
Solar System, and of Earth. It is agreed that the Milky Way is a spiral
galaxy, with observations suggesting that it is a barred spiral galaxy. It
contains 100-400 billion stars and an estimated 50 billion planets, 500
million of which could be located in the habitable zone of their parent
star. The Milky Way is part of the Local Group of galaxies and is one
of around 200 billion galaxies in the observable universe.
The Solar System is located in the Milky Way galaxy halfway out from
the center, on the inner edge of the Orion–Cygnus Arm. The Sun
orbits around the center of the galaxy in a galactic year—once every
225-250 million Earth years.
It is generally believed that a black hole does exist at the center of the
Milky Way galaxy. The latest value we have seen is that it has a mass of
about 2,000,000 that of the Sun. In fact, it is believed that this may be
common for most galaxies. Observational evidence supports these
ideas more and more. However, you must keep in mind that due to the
large absorption and source confusion when trying to look into the
center of a galaxy, it is very, very hard to see what's there!
The "Milky Way" is a translation of the Latin Via Lactea, in turn
translated from the Greek Γαλαξίας (Galaxias), referring to the pale
band of light formed by stars in the galactic plane as seen from Earth.