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Galaxies and the Milky Way

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Title: Galaxies and the Milky Way


1
Galaxies and the Milky Way
2
1. One light year 1 ly distance light travels
in 1 year
3
2. Galaxy large group of stars, gas and dust
held together by gravity
4
3. Estimate 40 billion galaxies can be seen.
5
4. Three types of galaxies spiral elliptical
and irregular
6
Spiral galaxy spiral arms and large central
round mass of stars
7
Barred spiral central mass of stars oblong,
not round
8
Elliptical galaxy
9
Elliptical galaxies are 3 dimensional ,
egg-shaped
10
Irregular
11
Irregular galaxy uncommon, no distinct shape
12
5) MOST common type galaxy dwarf elliptical
13
6. Milky Way spiral galaxy of 400 billion stars
including the Sun
14
Visible Examples of elliptical large and small
clouds of Magellan
15
7. Local group cluster of 45 galaxies near the
Milky Way.
16
8. Andromeda Galaxy largest galaxy in Local
Group
17
9. Galaxies are moving. Separate stars in
galaxies are also moving.
18
10. If galaxies collide stars so far
apart, most stars will just glide past each
other . http//www.youtube.com/watch?vWuucxy7snB
sfeaturerelmfu
19
11. Dwarf galaxy colliding with large galaxy may
be absorbed
20
12. Milky Way has already absorbed some dwarf
galaxies. No problem http//astroaviator.com/2009
/09/08/milky-way-and-the-dwarf/
21
13. But Milky Way and Andromeda Galaxy will
collide within 5 billion years
22
v
23
OOPS
24
14. How galaxies form gravity
25
Remember Milky Way contains 400 billion stars
26
15. Sun orbits around center of Milky Way
every 225 million years
27
How many times has Sun orbited since it formed?
28
22 times
29
16. All of the stars we can see belong to the
Milky Way.
30
17. structure of Milky Way spiral
31
18. Sun is 26,000 light years from center of
Milky Way
32
19. Spiral arms contain young stars and
protostars and nebulae
33
20 Stars form on the spiral arms
34
21. We believe the center of the galaxy is a
supermassive black hole.
35
Big Bang Theory
36
Cosmology
37
22. Cosmology is study of the universe.
38
Models of the universe
39
23. 1920s Oscillating model of universe
big bang and big crunch
40
a) Universe expanded rapidly, slowed, and then
contracted.
41
b) The universe continues cycle of expand and
contract .
42
24. 1948 Steady state theory a) universe has
always existed and always will.
43
b) As universe expands, new matter is created.
44
c)The density of the universe is constant.
45
25. Current theory Big Bang Theory
46
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47
a) Universe began as very hot, and very densely
packed matter
48
b) The matter exploded, expanded rapidly, and
cooled.
49
c) Matter did NOT expand into space, space
itself expanded.
50
d) Space continues to expand.
51
26. Universe is 13.7 billion years old
52
27. Relative motion of stars in the Milky Way
detected by Doppler Effect
53
Remember wavelength Red light l 700 nm
longer than blue light l 400 nm
54
Doppler effect each star emits a constant
wavelength of light star color
55
If star NOT moving relative to an observer,
observed wavelength is constant
56
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57
28.If star is moving away from observer,
wavelength appears longer Red Shift
58
29. If star is moving towards observer,
wavelength appears shorter. BLUE SHIFT
59
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60
31. HUBBLE RED SHIFT For distant galaxies, red
shift caused because Universe is expanding.
61
31. The Universe contains Visible mostly
hydrogen matter and Invisible dark matter
62
32.Very small percent of matter is ordinary
visible matter.
63
33.Majority of matter and energy in universe is
dark matter and dark energy.
64
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65
34. Einstein equation E mc2 relates energy
and mass
66
35 Universe is expanding AND accelerating
because of dark energy
67
36. gravity has less effect as Universe expands,
so matter accelerates apart
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