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Two Activities: 1. A Paper Tape Scale “Solar System” 2. The Size and Age of the Universe from Supernov ae (both in early pilot). Carl Pennypacker HOU Conference, June , 2009. Learning Goals:. Students learn: • Real size and scale of solar system planets and distances
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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: • 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! • 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! • 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!) • Remake your model. • 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 CandlesUse a known light source, measure how bright it is -- what variable is left?
Quick Cam Activity:Discover dependence of Brightness ondistance for a Standard Candle:1) Students make a model first -- draw a graph of measured counts of standard candle versus distance -- discuss2) Take a standard light source, standard exposure with quick cam (or use reference “star”)3) Measure images with Salsa J4) Make a graph5) 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.
The Sky in Chile By Chris Smith at Cerro Tololo
Punchline: Energy budget of Universe Dark Energy: ~70% Dark Matter: ~25% ~25% ~70%
Materials: (demo)1) One sheet (black)“Grid” of Universe at T=12) Transparency of expanded Universe at T=2 (red)3) Transparency marking pen4) Paper for making a table5) Graph paper Expansion Activity #1
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 #1 cont.)
4) What do you notice? 5) Untape and re-center on some random galaxy6) Put arrows on that galaxyMath note: Speed = Distance/time7) 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 galaxy9) Make a graph10) Figure out an age (Hubble constant-1) of the Universe, etc. Expansion Activity (cont)
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. Expansion Activity (cont) Sloan Supernova Strip Data
` The Supernovae! Data from Josh Frieman of the SDSS, University of Chicago Coordinates, redshifts ( z = v/c, where c = speed of light). SNID Redshift AKA RA DEC 1241 0.087 2005ff 22:30:41.41 -0:46:35.7 2308 0.148 2005ey 2:17:5.49 +0:16:49.1 5550 0.156 2005hy 0:14:23.59 +0:19:59.0 2422 0.265 2005fi 0:7:58.69 +0:38:17.5 5391 0.301 2005hs 3:29:22.08 -1:5:40.9 5844 0.311 2005ic 21:51:8.69 -0:50:34.6
Decoding the SDSS: (in this activity, the SDSS is used to find the supernovae)
New Feature:Photometry Tool! • Photometry Tool: Measure How Bright an Object is!!
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)
1) Measure Sne2) Fill in the table 3) Calculate Distance (jiffy formula to convert counts to million light years)4) Make a Hubble Diagram5) Get age of Universe Expansion Activity #2
1) “HPL-ize” these activities2) More pilots (with you all??) 3) Put on web, etc. Future of this Unit: