Expansion and Age

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Lecture 7

• Expansion and Age

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Pure Thermal Real Star Spectra
pure thermal spectrum
smooth curve
Brightness
absorption lines
real star spectrum
600
400
800
1000
200
Colors within spectrum need to match colors in
band
Wavelength (nm)
3
Optical Spectra Doppler Shifts
Hydrogen absorption line spectra
Zero shift stationary
1.5 redshift 4500 km/s
2.0 blueshift 6000 km/s
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Early Spectrographs
Hugginss two-prism spectrograph
Prism disperses the light
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Modern Spectrographs
Grating disperses light
VIMOS Spectrograph on VLT
Please include this image as well as the other
one.
GMOS spectrograph on Gemini North
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Real Galaxy Spectra
blue
red
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Galaxy Doppler Shifts
zero Doppler shift
z ??/?e 0.14 v 42,000 km/s !!
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Hubbles Original data
Hubbles 1929 data
1000
Velocity (km/s)
500
0
0
6
4
2
Distance (Mly)
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Hubbles Original Data
Hubbles 1931 Data
30,000
10,000
Velocity (km/s)
3,000
1,000
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10
12
14
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Faint Far
Bright Near
Galaxy Faintness (distance)
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The Hubble Law v Ho ? d
HST Key Project final results Freedman et al
(2000)
30,000
20,000
Velocity (km/s)
10,000
v Ho ? d
0
400
200
300
100
0
Distance (Mpc)
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Ho and the age of the Universe.
2v
v
2d
us
d
Distance Speed
d v
1 million light years 22 km/s
Time


1019 km 22 km/s


4.30 ? 1017 seconds
13.5 Billion years
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Ho and the age of the Universe.
v
us
v Ho ? d
d
Distance Speed
d Ho ? d
d v
1 Ho
Time



1 Ho
tH
Hubble time 13.5 Billion years
c Ho
rH tH ? c
Hubble radius 13.5 Billion light years
radius of visible Universe
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H-R Diagram for Young Cluster
Cluster M11 0.25 Gyr
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H-R Diagram of Older Cluster
Cluster M67 4.0 Gyr
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H-R Diagram of Old Cluster
Cluster 47 Tuc 12 Gyr
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Other Age Estimates
M55 very old
M42 very young
What are the oldest things in our galaxy? Are
these close to the age of the Universe?
N3293 young
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Redshift Stretch Factor Cosmic Stretch Factor
?emit
demit
dnow
?now
dnow demit
?now ?emit

rsf
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An Example
?em
?now
486
510
700 Mly
500
400
Wavelength (nm)
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End of Lecture
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