10/27/2010AST210, Fall 2010 1Hubble’s Law; Test 227 Oct• Test 2– Answer s– Lessons• Intro: What are galaxies?• Friday is start of Hubble’s Law and Big Bang. Essential class• No pre‐class questions for Fri.• Astronomical Horizons– Thurs, October 28, 7:30, Abrams Planetarium– Mars Meteorites: Rock Messengers from the Red Planet– Prof. Michael Velbel10/27/2010 AST 210, Fall 2010Test 2: Average: 11.5 (50%)Test 1: Average: 75%• Answers: Link T2 on syllabus on angel• Grade is on angel– Report>Report Setting– Choose “Grades”– Overall % (Course grade)• Eg., 90% (4.0)• Course grade– Test 1 is weighted 17% and Test 2 46% to make tests count same as all tests at end of course.– Average is 3.0• 50% of grade is in the future.Ast 207 F20100 20 40 60 8005101520RankTest214123491010/27/2010AST210, Fall 2010 2Test 2, Q1• Lost without knowing– What is an H‐R diagram?– Where are dwarfs & giants on H‐R diagram?• Main ideas– How are dwarfs in an old and new cluster different?– Hot‐plate model. ܮൌܴଶܶସWhat are the two physical parameters that determine location on H‐R diagram?– Conversion between luminosity & magnitude.10/27/2010 AST 210, Fall 2010Test 2, Q2• Background– Hot plate model ܮൌܴଶܶସ– Flux depends on distance.– Walter Adams’ discovery of a white dwarf.• Clues – Temperature same.– Star B is 15 mag fainter than star A.• Questions– Do Walter & Balter have the same information? If so, then I can reason as Walter did. If not, I cannot reproduce the same arguments.10/27/2010 AST 210, Fall 201010/27/2010AST210, Fall 2010 3Test 2, Q3• Main ideas– Kepler’s Laws– Newton’s realization.– K’s 3rdLaw as amended by Newton.10/27/2010 AST 210, Fall 2010Test 2, Q4• Main ideas– Parallax. Angle of a star changes over the year. Conversely, what motions are not due to parallax?– Angle=Baseline/Distance• Learn from doing homework– Do the problem.– Afterwards• Recapitulate how you did it.• What did you learn?• Bad practices– If it looks sort of like a duck, it must be a duck.– Find a formula with some of the same symbols.– Find an example and use the same numbers.– Balter is the same as Walter.• Good practices– What is the main idea? Write it in your own words.10/27/2010 AST 210, Fall 201010/27/2010AST210, Fall 2010 4Realm of the nebulae (galaxies)• Galaxies are made of billions of stars, gas, dust, and dark matter.• Our galaxy is the Milky Way .• Nearest big galaxy is our big sister Andromeda, which is 0.7Mpc from us. Sun is 8kpc from center of the Milky Way .10/27/2010 AST 210, Fall 2010Andromeda10/27/2010 AST 210, Fall 201010/27/2010AST210, Fall 2010 5Sombrero10/27/2010 AST 210, Fall 2010M5110/27/2010 AST 210, Fall 201010/27/2010AST210, Fall 2010 6M8710/27/2010 AST 210, Fall 2010Galaxy cluster A221810/27/2010 AST 210, Fall 201010/27/2010AST210, Fall 2010 71. Which is bigger, galaxy or star cluster? Galaxy or solar system?A. Galaxy. Solar system.B. Star cluster. Solar systemC. Star cluster. Galaxy.D. Galaxy. Galaxy.10/27/2010 AST 210, Fall
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