Milky Way Galaxy
Cosmology:
W. Herschel
H. Shapley
Shapley vs. Curtis
Structure of our galaxy
Mapping our galaxy (21cm)
size, population, motion
Chapter 23
By
reading
this
chapter,
you
will
learn
23-1 How astronomers
discovered the solar system’s
location within the Milky Way
Galaxy
23-2 The shape and size of our
Galaxy
23-3 How the Milky Way’s spiral
structure was discovered
23-4 The evidence for the
existence of dark matter in our
Galaxy
23-5 What causes the Milky
Way’s spiral arms to form and
persist
23-6 How astronomers
discovered a supermassive
black hole at the galactic center
Our Galaxy
Wide-angle photograph spanning half the
Milky Way, as seen from the equatorial
latitudes. More than a million stars in the disk of
our Galaxy fill this view, which covers a relatively
clear window just 4º south of the galactic nucleus
in Sagittarius.
Understanding the structure of our galaxy
1. W. Herschel place ____at the center of
the universe. a) Earth, b) Moon, c) The
Sun, d) center of MWG
2. H. Shapley observed _____ to displace
the Sun from the center. a) Supernova,
b) Cepheid VS, c) OSC, d)GSC
3.
T / F Some of the Apollo astronauts have seen
MWG like this picture below.
1.c, 2.b, 3.F
Mapping
the
Galaxy
right: Synchrotron
radiation or 21cm
line
below: Measure
the Doppler shift of
21cm line to
determine the
structure / motion
Zoom out past Earth, Venus, Mercury & the Sun. Go beyond the solar system, and out
What kind of stars / matters are found in our galaxy?
Structure of Milky
Way Galaxy
Density wave & star
formation.
Watch the animation to learn how density wave
works.
As the starts in our galaxy move through the high
density area, start formations takes place out
of the available interstellar matter.
Our Galaxy
• Diameter is about 100,000 ly
• Sun about 26,000 ly from the
galactic center
• Disk contains gas, dust and
Population I stars
• Halo is composed mostly of
Population II stars.
IR view by COBE
1. Radio emission from _____ helped us learn
the structure of our galaxy. a) hydrogen, b)
Helium, c) Carbon, d) water
2. The sun is located at __in our galaxy. a) The
center, b) in Halo, outskirts of our galaxy, c)
about half way between the center and edge
of visible part of disk of our galaxy d) this is
not known yet.
3. Most young stars are found in: ) The center, b)
in Halo, outskirts of our galaxy, c) disk of our
galaxy d) this is not known yet because MWG
is too dusty for us to determine this info.
1. a, 2. c, 3. c
This sequence shows how astronomers are using Chandra to help probe the mysterious region at the
center of the Milky Way. The first image is a 900- by 400-light-year mosaic in X-rays taken by
Chandra. The view then zooms into a smaller region that encompasses the latest Chandra discovery
of puzzling, extremely hot and diffuse emission. From there, the sequence shows two even smaller
fields of view of the region surrounding the Milky Way's supermassive black hole, known as Sgr A*.
The final element is an artist's conception of Sgr A* itself and its accretion disk as it undergoes a flare
Galactic motion
Center of our galaxy and galactic motion
1. Chandra space telescope observe the
universe in: a) visible light, b) infrared, c) radio
waves, d) x ray
2. Pictures form Chandra space telescope
shows there is ____ at the center of our
galaxy. A) giant star, b) giant neutron star, c)
blackhole, d) another universe
3. The motion of the Milky Way galaxy appear to
follow Kepler’s 3rd law. True / False why or
why not?
1. d, 2. c, 3. false, there must be other source of
gravity that we are not seeing.
Discovery channel: Milky way galaxy
•
http://science.discovery.com/videos/space-schoolmilky-way.html
1. Who first speculated the band of what appear to be cloud
of gas is made up of collation of stars.
2. What type of galaxy is our galaxy?
3. Where is the sun in our galaxy?
4. Describe the motion of the sun.
5. How old is our galaxy?
6. What make up more than 90% of our galaxy? What is it?
7. Which direction is the center of out galaxy?
8. What will you find out the center of our galaxy?
9. Will our galaxy ever collide with other galaxy?
10. How many stars are forming in our galaxy?
11. Have we found any earth like planets yet?
• The Universe: Backyard Astronomer Behold The Milky Way
• http://www.history.com/video.do?name=Th
e_Universe&bcpid=1406608117&bclid=14
00530708&bctid=1400494629
Milky Way galaxy: see 2nd&3rd page of your
homework for this week!
G
F
E
D
C
B
A
H
This
worksheet is
to have you
better
understand
the size of the
Milky Way
galaxy. In this
picture of the
Milky way
galaxy, 1cm is
represent
5,000 ly.