1. Learning Goals: I will:
4. Complex Knowledge: demonstrations of learning that go aboveand above and beyond what was explicitly taught. 3. Knowledge: meeting the learning goals and expectations. 2. Foundational knowledge: simpler procedures, isolated details, vocabulary. 1. Limited knowledge: know very little details but working toward a higher level.
I will:
understand the properties of different types of galaxies.
understand how the universe came to be what we observe today.
understand how astronomers use astronomical objects (standard candles)
Understand how we use a distance ladder to estimate the size of the universe and to measure large distances in the universe.
understand how astronomers determine the age and size of the universe?.

2. Question of the day
How does Hubble's law help determine distances to the most remote galaxies?

3. Redshift of Spectral Lines
Which color of visible light has the longest wavelength?
Which color of visible light has the shortest wavelength?

4. The Doppler Effect
change in frequency of a wave for an observer moving relative to the source of the wave.
compared to the actual emitted frequency, received frequency is:
higher during the approach,
identical at the instant of passing by,
lower during the recession.

5. Not Just Sound

6. Sun Distant Supercluster
If you know how redshifted an object’s spectrum is, you know how fast it is moving away from you

8. Hubble Diagram
Hubble used Cepheids and type 1a supernovae to calculate the distance to thousands of galaxies
He used their spectrum to calculate the velocity at which those galaxies are moving away from us
Now, his diagram is used to calculate the distance to faraway galaxies that do NOT have Cepheids or Type 1a Supernovae in them
H0 - the Hubble constant was calculated from this graph
H0 = v/d
H0 = Hubble's constant
v= velocity
d= distance

9. Hubble’s Constant
The Hubble Constant (slope) describes how fast objects appear to be moving away from our galaxy as a function of distance
Distant galaxies are ALL redshifted…meaning they are receding from us
From all of the previous methods, we figured out how far away tens of thousands of individual galaxies are
Things farther from us are going away faster (more redshifted) than things closer to us (less redshifted)

10. Hubble’s constant
We’ve plotted this relationship between amount of redshift and distance out onto a graph
When we find a new galaxy, we measure the redshift from its spectrum, and use the graph to determine its distance from us
Not super accurate, still some debate over the constant’s actual value
Hubble was way wrong, thought it had a value around 500! He had the right idea though

11. The community is divided into two schools of thought;
There is currently a strong debate on the value of the Hubble's constant fueled by new data from HST Cepheid studies of nearby galaxies.
The community is divided into two schools of thought;
1) the old school which proposes a value for Hubble's constant around ~50 [(km/s)/Mps] to agree with the ages of the oldest stars in our Galaxy, and
2) a newer, and larger school which finds a higher Hubble's constant of ~ This higher value poses a problem for modern cosmology in that the age of the Universe from Hubble's constant is less than the age of the oldest stars as determined by nuclear physics. (rate of fusion)

12. So the dilemma is this, either something is wrong with nuclear physics or something is wrong with our understanding of the geometry of the Universe.

13. It is important to figure out though because it helps us determine things like:
The age of the universe
The size of the universe
What will happen to the universe in the future

14. One possible solution
the universe isn’t expanding and hasn’t been expanding at the same speed throughout its history. It’s expansion has changed speed. But How?!?

15. Cosmological Constant
This is a mysterious force that can be interpreted as a repulsive force that exactly balances the pull of gravity if the universe was static
It was the only way Einstein could get his equations to work
when Hubble discovered the universe was expanding, Einstein took it back out of his equations because he didn’t need it. – he called it his BIGGEST BLUNDER

18. Everything is expanding away from everything else!
Which means there is no center
Everywhere seems to be the center at the same time

19. Question of the day
How does Hubble's law help determine distances to the most remote galaxies?

20. Checking In Questions…
If a galaxy’s spectral lines are redshifted by 3%, how fast is the galaxy moving away from us?

21. Checking In Questions…
If a galaxy’s spectral lines are redshifted by 3%, how fast is the galaxy moving away from us?
3% the speed of light = 0.03(3x108m/s) = 9x106m/s
9,000,000 m/s

24. Checking In Questions…
If a galaxy’s spectral lines are redshifted by 3%, how fast is the galaxy moving away from us?
3% the speed of light = 0.03(3x108m/s) = 9x106m/s
2. Spectral lines shifted and
observed-rest/rest = /300 = 0.06
observed-rest/rest = /320=0.06
0.06(3x108m/s) = 1.8x107m/s
1,800,000 m/s

26. Checking In d=2,400,000 light years Redshift = .002
0.002(3x108m/s) = 6X105m/s = 6x102km/s
Velocity = 6x102km/s
Hubble Constant = 25km/s per million light years
d= v/H0
d= (6x102km/s) / (25km/s per million light years)
d= (6x102km/s) / (25km/s)/(106ly)
d=(6x102km/s) x (106ly)/(25km/s)
d=(6x102)x (106ly)/(25)
d=2.4x107 light years
d=2,400,000 light years

28. This is due at Midnight tomorrow
It is on Canvas