Transcript Measuring the Age of the Universe

Two Activities:
1. A Paper Tape Scale “Solar System”
2. The Size and Age of the Universe
from Supernovae
(both in early pilot)
Carl Pennypacker
HOU Conference, June , 2009
Learning Goals:
Students learn:
• Real size and scale of solar system planets and
distances
•
Use of ratios in making scale models
•
Distance = speed x time
•
1/R2 Law for brightness vs. Distance (Quick Cams!!)
•
Expansion and Age of Universe
Note on Pedagogy:
• Elicit Preconceptions
• Make a first attempt model
• Discuss the Why of their model in groups,
class, etc.
• Measure/evidence
• Make a new model
Make a Paper Tape “Solar System”!
Rich Lohman has co-developed this unit
(Just Earth, Sun, and Jupiter)
Materials:
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5 meter paper tape 1 AU = 1 meter
Big sheet of paper for Sun, Earth, Jupiter
Protractors (string) for making “Big” circles for scale sun- planets
Scissors for cutting out planets
Meter Stick
Tape
Work sheet (for refining estimates)
Make a Paper Tape Solar System(cont)!
• Assume 5 meters is distance from Jupiter to Sun (= 5 “AU’s”
Earth is at 1 AU -- the Sun is at one end, Jupiter at other.
1 AU = 1 meter is the distance from the sun to the earth.
• Without thinking, search your heart and emotions for the
best size circle (draw and cut out) that matches the scale size of
the Earth, the Sun, and Jupiter. Students usually make sun as
big as paper. They seem to get ratios right, though.
“There Is no wrong answer!! Go for it!”
• Share your model with the class -- why do they choose
these models. Let them luxuriate in these neurons and synapses
of their great first models!
Make a Paper Tape Solar System!
• Go to computers and open SalsaJ, and measure the size of
the Sun, Earth, and Jupiter. Desktop:
Fireball.fts = Jupiter 1 pixel = 340 km
Sun = Sun1 1 pixel = 4100 km
Earth_from_mars = Earth 1 pixel = 220 km
Make a Paper Tape Solar System!
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Go to computers and open SalsaJ, and measure the size of the Sun, Earth,
and Jupiter. Desktop:
Fireball.fts = Jupiter
Sun1 = Sun 1 pixel
Earth_from_mars = Earth
Make a Paper Tape Solar System!
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Find the size in kilometers of the Sun, Jupiter, and the Earth.
• Convert kilometers into millimeters by dividing by
150,000. (cookbook for now -- need to drill down!)
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Remake your model.
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Class Discussion -- have to figure out how not to make teacher
seem like too much a smarty pants and students too naïve.
Now: Shift Gears to Hubble Activity:A word about the
Expansion of the Universe With M&M Cookie:
Velocities are reasonably easy to measure
With Doppler shift in spectra:
A Challenge: How to measure Distance!
Calibrated Standard Candles
Use a known light source, measure how
bright it is -- what variable is left?
Quick Cam Activity:
Discover dependence of Brightness on
distance for a Standard Candle:
1) Students make a model first -- draw a graph of
measured counts of standard candle versus distance -discuss
2) Take a standard light source, standard exposure with
quick cam (or use reference “star”)
3) Measure images with Salsa J
4) Make a graph
5) Make a new model/law
Why are all the Type Ia SNe of nearly the same brightness?
 When a star of near Solar Mass uses up all of its Hydrogen
and Helium it collapses to a White Dwarf. (W.D.)
 If the White Dwarf has a companion star then, for the right
conditions, Mass can be Transferred to the W.D.
 Type Ia SNe are due to the explosion of a W.D.
This occurs when it reaches a mass of 1.4 M0
(the Chandrasekhar limit) from Mass Transfer
The star of about the size of the Sun
becomes a White Dwarf about the size
of the Earth.
`
The WD consists of carbon and
oxygen nuclei and a free electron gas.

The Supernova explosion occurs
when the gravitational pressure
exceeds the electron gas pressure.
Supernova Discovery and Measurement Sequence.
The Sky in Chile
By Chris Smith at Cerro Tololo
QuickTime™ and a
Motion JPEG A decompressor
are needed to see this picture.
The Hubble SpaceTelescope
\
Supernova Light Curve and Spectrum
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
SNe Light Curves from the HST and Images
Hubble Curves
Concordance between SNe, CMB and Clusters
M
Punchline: Energy budget of Universe
Dark
Energy:
~70%
Dark
Matter:
~25%
~25%
~70%
Expansion Activity #1
Materials: (demo)
1)
One sheet (black)“Grid” of Universe at T=1
2)
Transparency of expanded Universe at T=2 (red)
3)
Transparency marking pen
4)
Paper for making a table
5)
Graph paper
Expansion Activity #1 cont.)
1) Tape down T = 1 Universe (paper)
2) Tape down with T = 2 Universe
(transparency)
3) Tape down blank transparency and carefully
draw arrows from the same “galaxies” at T=1
connecting them to the same galaxy at T=2
Expansion Activity (cont)
4) What do you notice?
5) Untape and re-center on some random galaxy
6) Put arrows on that galaxy
Math note: Speed = Distance/time
7) Record the distance to the galaxy and also the
speed, which is the length of the arrow (need to
understand this)
Expansion Activity (cont)
8) Make a table of distance from the origin
and the velocity of each galaxy
9)
Make a graph
10) Figure out an age (Hubble constant-1)
of the Universe, etc.
Expansion Activity (cont)
Sloan Supernova Strip Data
The Sloan Digital Sky Survey telescope undertook
a focused study of a strip of the sky and discovered
over a hundred Type Ia supernovae.
We have five good ones from them to use.
The Supernovae!
Data from Josh Frieman of the SDSS, University of Chicago
`
Coordinates, redshifts ( z = v/c, where c = speed of light).
SNID
Redshift
1241 0.087
2308
0.148
5550
0.156
2422 0.265
5391
0.301
5844
0.311
AKA
2005ff
2005ey
2005hy
2005fi
2005hs
2005ic
RA
22:30:41.41
2:17:5.49
0:14:23.59
0:7:58.69
3:29:22.08
21:51:8.69
DEC
-0:46:35.7
+0:16:49.1
+0:19:59.0
+0:38:17.5
-1:5:40.9
-0:50:34.6
Decoding the SDSS:
(in this activity, the SDSS is used to find the supernovae)
Decoding the SDSS (continued)
Decoding the SDSS (continued)
New Feature:
Photometry Tool!
 Photometry Tool: Measure How Bright an Object is!!
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Photometry Tool: Measure How Bright an Object is!! (find Sne first)
 1) Click on photometry tool
 2) Click on star you want to read
3) Read off intensity (in counts) (photometry measures all of the counts within
a circular ring, and subtracts off background)
Expansion Activity #2
1) Measure Sne
2) Fill in the table
3) Calculate Distance (jiffy formula to
convert counts to million light years)
4) Make a Hubble Diagram
5) Get age of Universe
Future of this Unit:
1) “HPL-ize” these activities
2) More pilots (with you
all??)
3) Put on web, etc.