hubble deep field - ann arbor earth science
TRANSCRIPT
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Hubble Deep Field
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Hubble Ultra Deep Field
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Spiral Galaxy
Elliptical Galaxy
Hubble Ultra Deep Field
Spiral Galaxy
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Spiral Galaxy
Hubble Ultra Deep Field
Spiral Galaxy
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Spiral Galaxy
Elliptical Galaxy
Hubble Ultra Deep Field
Elliptical Galaxy
Spiral Galaxy
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Spiral Galaxy
Elliptical Galaxy
Hubble Ultra Deep Field
Elliptical Galaxy
Spiral Galaxy
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Spiral Galaxy
Elliptical Galaxy
Irregular Galaxies
Hubble Ultra Deep Field
Elliptical Galaxy
Spiral Galaxy
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How are galaxies grouped together?
Cosmology questions
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Spiral galaxies are often found in groups of galaxies
(up to a few dozen galaxies)
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Elliptical galaxies are much more common in huge clusters of galaxies
(hundreds to thousands of galaxies)
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Are galaxies doing anything peculiar?
Cosmology questions
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The spectral features of virtually all galaxies are redshifted � They’re all moving away from us
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Edwin Hubble, using Cepheids as standard candles, was one of the first to measure distances to other galaxies
By measuring distances to galaxies, Hubble found that redshift and distance are related in a special way
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y= mx+b
b
y
x
∆x
∆y
where m=∆y/∆x
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y = mx +bvelocity = (H0)i(distance) + 0 The Hubble
LawH0 is the ‘Hubble constant’
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velocity = (H0)i(distance)
The Hubble Law:
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Redshift of a galaxy tells us its distance through Hubble’s Law:
distance = velocity
H0
redshift (z) is defined:0
0
m velocityz
c
λ λλ−� ≅
0 mλ λ
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Homework #11
1. Hubble originally got 250 km/s Mpc for the Hubble constant. How old is the universe with that value of H0?
3. If a galaxy has a redshift of 0.02, how fast is it traveling away from us?
4. How far away is the galaxy?
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Homework #11
1. Hubble originally got … for the Hubble constant. How is the universe with that value of H0?
3. If a galaxy has a redshift of 0.02, how fast is it going?
4. How far away is it?
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Distances of farthest galaxies are measured from redshifts
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How do distance measurements tell us the age of the universe?
Cosmology questions
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Thought Question
Your friend leaves your house. She later calls you on her cell phone, saying that she’s been driving at 60 miles an hour directly away from you the whole time and is now 60 miles away. How long has she been gone?
A. 1 minute
B. 30 minutes
C. 60 minutes
D. 120 minutes
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Thought Question
Your friend leaves your house. She later calls you on her cell phone, saying that she’s been driving at 60 miles an hour directly away from you the whole time and is now 60 miles away. How long has she been gone?
A. 1 minute
B. 30 minutes
C. 60 minutes
D. 120 minutesdistance 60 miles
time = = =1 hourspeed 60 miles/hour
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Thought Question
Your observe a galaxy moving away from you at 0.1 light-years per year, and it is now 1.4 billion light-years away from you. How long has it taken to get there?
A. 1 million years
B. 14 million years
C. 10 billion years
D. 14 billion years
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Thought Question
Your observe a galaxy moving away from you at 0.1 light-years per year, and it is now 1.4 billion light-years away from you. How long has it taken to get there?
A. 1 million years
B. 14 million years
C. 10 billion years
D. 14 billion years1.4 billion lytime = = 14 billion years
0.1 ly/year
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Hubble’s constant tells us age of universe because it relates velocities and distances of all galaxies
Age =
~ 1 / H0
Distance
Velocity
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distance?
Distances between faraway galaxies change while light travels
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Distances between faraway galaxies change while light travels
Astronomers think in terms of lookback time rather than distance
distance?
lookback time
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Expansion stretches photon wavelengths causing a cosmological redshift directly related to lookback time
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Cosmological Horizon
Maximum lookback time of 14 billion years limits how far we can see
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Cosmological Principle
The universe looks about the same no matter where you are within it
• Matter is evenly distributed on very large scales in the universe
• No center & no edges
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Surface of a balloon expands but has no center or edge
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Cosmological Principle
The universe looks about the same no matter where you are within it
• Matter is evenly distributed on very large scales in the universe
• No center & no edges• Not proven but consistent with all observations to
date
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Has the Universe changed?
Cosmology questions