Black Holes

1
Black Holes
2
Discussion
How can we go about looking for black holes if no
light can get out of them?
3
(No Transcript)
4
(No Transcript)
5
X-ray image
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
Simulated black hole picture
11
Discussion
Black holes are the ultimate blackbodies , or
perfect absorbers. All light that shines on them
is absorbed and none of it can get back out. But
what happens to a perfect absorber?
12
(No Transcript)
13
Black holes radiate
Too little to ever be observed
14
The galactic center
Contains a strong radio source called Sagittarius
A which is likely to be a 3 million M? black
hole.
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
The results
At the position of Sagittarius A there must be
roughly 3 million solar masses within the size of
the solar system. The Schwarzschild radius of
a 3 million solar mass black hole is only 9
million km, or about 13 times the radius of the
Sun.
20
(No Transcript)
21
Black hole sounds
22
(No Transcript)
23
Wormholes
Tunnels through spacetime.
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
Milky Way
28
Discussion
How would you go about plotting the size and
shape of our galaxy?
29
Herschels view of Milky Way
30
M13 Hercules
31
Discussion
How can we determine the distances to globular
clusters? All the globular clusters are too far
away to get parallax distances.
32
(No Transcript)
33
(No Transcript)
34
Main-Sequence fitting
Match the band of main-sequence stars with
another H-R diagram plotted with temp. and
luminosity.
35
RR Lyrae stars
The most accurate way to measure the distance to
globular clusters is by measuring the period of
the RR Lyrae stars.
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
Discussion
Why cant we just use the higher luminosity
Cepheids to find the distance to globular
clusters?
40
(No Transcript)
41
The results
The globular clusters are centered around a point
8 kpc from the Sun in the direction of
Sagittarius.
42
(No Transcript)
43
(No Transcript)
44
Interstellar absorption
The galaxy contains large amounts of dust and gas
in the galactic plane that obscures stars.
45
(No Transcript)
46
(No Transcript)
47
Discussion
What observations could you make to either prove
or disprove this conclusion?
48
MW in infrared light
MW in microwave
49
(No Transcript)
50
Discussion
If you wanted to map out the hydrogen gas in the
galaxy, how might you go about doing it? What
are the disadvantages of your method?
51
(No Transcript)
52
(No Transcript)
53
(No Transcript)
54
HI neutral Hydrogen map
55
(No Transcript)
56
Stellar populations

• Bulge
• Thin disk
• Thick disk
• Halo

57
(No Transcript)
58
(No Transcript)
59
Discussion
The Sun, traveling at 220 km/sec takes about 220
million years to complete one orbit around the
galaxy. How could we measure the motion of the
Sun about the galactic center? Hint It
involves the globular clusters