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THE LIFE AND DEATH OF BOB (a.k.a. NGC 6397) IN AN INTRODUCTORY COLLEGE-LEVEL ASTRONOMY COURSE

0. THE LIFE AND DEATH OF BOB (a.k.a. NGC 6397) IN AN INTRODUCTORY COLLEGE-LEVEL ASTRONOMY COURSE. 0. Hmmm…what would be a good way to start an introductory stars and galaxies class for non-science majors at a state university?. Lots of equations?!? perhaps not Pretty pictures?

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THE LIFE AND DEATH OF BOB (a.k.a. NGC 6397) IN AN INTRODUCTORY COLLEGE-LEVEL ASTRONOMY COURSE

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  1. 0 THE LIFE AND DEATH OF BOB (a.k.a. NGC 6397) IN AN INTRODUCTORY COLLEGE-LEVEL ASTRONOMY COURSE Dr. C. Renee James NASA Top Stars 2010

  2. 0 Hmmm…what would be a good way to start an introductory stars and galaxies class for non-science majors at a state university? Lots of equations?!? perhaps not Pretty pictures? that’d probably work, but there are so many… Dr. C. Renee James NASA Top Stars 2010

  3. I know! I’ll just scour the Hubble Heritage Site for something cool-looking that relates to stars and galaxies. Dr. C. Renee James NASA Top Stars 2010

  4. 0 Okay…I just spent four hours looking at a jillion cool photos. Perhaps I should start smaller. Maybe with the “stars” part of “stars and galaxies.” Aha! Here’s one... Dr. C. Renee James NASA Top Stars 2010

  5. My new friend: NGC 6397http://heritage.stsci.edu/2003/21/index.html • Good colors. Not too complicated looking. Stars have a variety of obvious differences. Plus globular clusters might come in handy later this semester. Sure…I’ll start with this one, but how? Dr. C. Renee James NASA Top Stars 2010

  6. What does the education research say? • Let the students ask the questions. (inquiry-based learning) • Let the students work together to find the answers. (collaborative learning) • Just a few of the references on the subject (in 3 point font – see end of show for a more legible version) • Abell, S., George, M., & Martini, M. 2002, The Moon Investigation: Instructional Strategies for Strategies for Elementary Science Methods, Journal of Science Teacher Education, 13(2), 85. • Abell, S., Martini, M., & George, M. 2001, 'That's What Scientists Have To Do': Preservice Elementary Teachers' Conceptions of the Nature of Science During a Moon Investigation, International Journal of Science Education, 23(11), 1095. • Adams, J. P., & Slater, T. F. 1998, Mysteries of the Sky: Activities for Collaborative Groups, Dubuque, IA: Kendall Hunt Publishing, 1998a. • Adams, J. P., & Slater, T. F. 1998, Using Action Research To Bring the Large Lecture Course Down to Size, Journal of College Science Teaching, 28, 87, 1998b. • Adams, J. P., & Slater, T. F. 2002, Learning Through Sharing: Supplementing the Astronomy Lecture with Collaborative-Learning Group Activities, Journal of College Science Teaching, 31, 384. • Adams, J. P., & Slater, T. F. 2000, Astronomy in the National Science Education Standards, Journal of Geoscience Education, 48, 39. • Adams, J. P., Brissenden, G., Lindell, R. S., Slater, T. F., & Wallace, J. 2002, Observations of Student Behavior in Collaborative Learning Groups, Astronomy Education Review, 1(1), 25. http://aer.noao.edu/AERArticle.php?issue=1&section=1&article=2. • Adams, J. P., Prather, E. E., & Slater, T. F. 2002, Lecture-Tutorials for Introductory Astronomy, Preliminary Ed., Upper Saddle River, NJ: Prentice Hall. • Albanese, A., Danhoni Neves, M. C., & Vicentini, M. 1997, Models in Science and in Education: A Critical Review of Research on Students' Ideas About the Earth and Its Place in the Universe, Science and Education, 6, 573. • American Association for the Advancement of Science Project 2061. 1993, Benchmarks for Science Literacy, New York: Oxford University Press. • Ashcraft, P., & Courson, S. 2003, Effects of an Inquiry-Based Intervention to Modify Pre-Service Teachers' Understanding of Seasons, Paper presented at the Annual Meeting of theNational Association for Research in Science Teaching, March, Philadelphia, PA. • Atwood, R. K., & Atwood, V. A. 1996, Preservice Elementary Teachers' Conceptions of the Causes of Seasons, Journal of Research in Science Teaching, 33, 553. • Atwood, V. A., & Atwood, R. K. 1995, Preservice Elementary Teachers' Conceptions of What Causes Night and Day, School Science and Mathematics, 95, 290. • Bailey, J. M. 2000, On the Nature of Moonquakes, The Physics Teacher, 38, 522. • Baker, B., & Heruth, D. 2000, An Interdisciplinary Approach to Stargazing, The Physics Teacher, 38, 555. • Ball, N., Coyle, H. P., & Shapiro, I. I. (Eds.). 1994, Project SPICA: A Teacher Resource to Enhance Astronomy Education, Dubuque, IA: Kendall-Hunt Publishing. • Barba, R., & Rubba, P. A. 1992, A Comparison of Preservice and In-Service Earth and Space Science Teachers' General Mental Abilities, Content Knowledge, and Problem-Solving Skills, Journal of Research in Science Teaching, 29, 1021. • Barnett, M., & Morran, J. 2002, Addressing Children's Alternative Frameworks of the Moon's Phases and Eclipses, International Journal of Science Education, 24(8), 859. • Baxter, J. 1989, Children's Understanding of Familiar Astronomical Events, International Journal of Science Education, 11, 502. • Bieniek, R. J., & Zeilik, M. 1976, Follow-up Study of a PSI Astronomy Course, American Journal of Physics, 44(7), 695. • Bisard, W. J., Aron, R. H., Francek, M. A., & Nelson, B. D. 1994, Assessing Selected Physical Science and Earth Science Misconceptions of Middle School Through University Preservice Teachers: Breaking the Science 'Misconception Cycle', Journal of College Science Teaching, 24, 38. • Bishop, J. E. 1977, United States Astronomy Education: Past, Present, and Future, Science Education, 61, 295. • Bobrowsky, M. 2000, Teaching Evolutionary Processes to Skeptical Students, The Physics Teacher, 38, 565. • Brickhouse, N. W., Dagher, Z. R., Letts IV, W. J., & Shipman, H. L. 2000, Diversity of Students' Views About Evidence, Theory, and the Interface Between Science and Religion in an Astronomy Course, Journal of Research in Science Teaching, 37(4), 340. • Brickhouse, N. W., Dagher, Z. R., Shipman, H. L., & Letts IV, W. J. 2002, Evidence and Warrants for Belief in a College Astronomy Course, Science and Education, 11(6), 573. • Brissenden, G. 2001, SABER Astronomy Online Database: Searchable Annotated Bibliography of Education Research, Retrieved February 15, 2002, from http://www.cdes-astro.com/saber/index.htm. • Callison, P. L., & Wright, E. L. 1993, The Effect of Teaching Strategies Using Models on Preservice Elementary Teachers' Conceptions About Earth-Sun-Moon Relationships, Paper presented at the Annual Meeting of the National Association for Research in Science Teaching, April, Atlanta, GA. • Casey, T. L., & Slater, T. F. 2002, A Comparison of Group and Individually Completed Course Evaluations in Introductory Astronomy, Astronomy Education Review, 1(2), 1. http://aer.noao.edu/AERArticle.php?issue=2&section=2&article=3. • Comins, N. F. 2000, A Method To Help Students Overcome Astronomy Misconceptions, The Physics Teacher, 38, 542, 2000a. • Comins, N. F. 2000, An In-Your-Face Approach to Student Misconceptions About Astronomy, Unpublished manuscript, 2000b. • Comins, N. F. 2001, Heavenly Errors: Misconceptions About the Real Nature of the Universe, New York: Columbia University Press. • DeLaughter, J. E., Stein, S., Stein, C. A., & Bain, K. R. 1998, Preconceptions Abound Among Students in an Introductory Earth Science Course, EOS Transactions, 79, 429. • Deming, G., & Hufnagel, B. 2001, Who's taking ASTRO 101?, The Physics Teacher, 39, 368. • diSessa, A. 1993, Toward an Epistemology of Physics, Cognition and Instruction, 10, 105. • Dunlop, J. 2000, How Children Observe the Universe, Publications of the Astronomical Society of Australia, 17, 194. • Fanetti, T. M. 2001, The Relationships of Scale Concepts on College Age Students' Misconceptions About the Cause of Lunar Phases, Unpublished master's thesis, Iowa State University, Ames. • Finegold, M., & Pundak, D. 1990, Students' Conceptual Frameworks in Astronomy, Australian Science Teachers Journal, 36, 76. • Fletcher, J. K. 1980, Traditional Planetarium Programming Versus Participatory Planetarium Programming, School Science and Mathematics, 80, 227. • Fraknoi, A. 1998, Astronomy Education: A Selective Bibliography, Retrieved April 6, 2003, from http://www.astrosociety.org/education/resources/educ_bib.html. • Fraknoi, A. 2002, Enrollments in Astronomy 101 Courses: An Update, Astronomy Education Review, 1(1), 121. http://aer.noao.edu/AERArticle.php?issue=1&section=4&article=2. • Gregory, B., Luzader, W. M., & Coyle, H. P. 1995, Project STAR: The Universe in Your Hands, Dubuque, IA: Kendall-Hunt Publishing. • Haupt, G. W. 1948, First Grade Concepts of the Moon, Science Education, 32(4), 258. • Haupt, G. W. 1950, First Grade Concepts of the Moon: Part II: By Interview, Science Education, 34(4), 224. • Hemenway, M. K., Straits, W. J., Wilke, R. R., & Hufnagel, B. 2002, Educational Research in an Introductory Astronomy Course, Innovative Higher Education, 26(4), 271. • Hufnagel, B. 2002, Development of the Astronomy Diagnostic Test, Astronomy Education Review, 1(1), 47. http://aer.noao.edu/AERArticle.php?issue=1&section=1&article=4. • Hufnagel, B., Slater, T. F., Deming, G., Adams, J. P., Adrien, R. L., Brick, C., & Zeilik, M. 2000, Pre-Course Results from the Astronomy Diagnostic Test, Publications of the Astronomical Society of Australia, 17, 152. • Janke, D. L., & Pella, M. O. 1972, Earth Science Concept List for Grades K–12 Curriculum Construction and Evaluation, Journal of Research in Science Teaching, 9, 223. • Jones, B. L., Lynch, P. P., & Reesink, C. 1987, Children's Conceptions of the Earth, Sun and Moon, International Journal of Science Education, 9, 43. • Kikas, E. 1998, The Impact of Teaching on Students' Definitions and Explanations of Astronomical Phenomena, Learning and Instruction, 8, 439. Klein, C. 1982, Children's Concepts of the Earth and the Sun: A Cross-Cultural Study, Science Education, 65, 95. Lightman, A., & Sadler, P. M. 1988, The Earth Is Round? Who Are You Kidding?, Science and Children, 25(5), 24. Lightman, A., & Sadler, P. M. 1993, Teacher Predictions Versus Actual Student Gains, The Physics Teacher, 31, 162. Lindell, R. S. 2001, Enhancing College Students' Understanding of Lunar Phases, Unpublished doctoral dissertation, University of Nebraska, Lincoln. Lindell, R. S., & Olsen, J. P. 2002, Developing the Lunar Phases Concept Inventory, Paper presented at the American Association of Physics Teachers Summer Meeting (Physics Education Research Conference), August, Boise, ID. Mali, G., & Howe, A. 1979, A Development of Earth and Gravity Concepts Among Nepali Children, Science Education, 63, 685. Mallon, G. L., & Bruce, M. H. 1982, Student Achievement and Attitudes in Astronomy: An Experimental Comparison of Two Planetarium Programs, Journal of Research in Science Teaching, 19, 53. Maran, S. P. 2000, 'Hot Topics' in Astrophysics, The Physics Teacher, 38, 550. Morrow, C. A. 2003, Misconceptions scientists often have about the K–12 National Science Education Standards, Astronomy Education Review, 1(2), 84. http://aer.noao.edu/AERArticle.php?issue=2&section=2&article=8. National Research Council. 1996, National Science Education Standards, Washington, D.C.: National Academy Press. National Research Council. 1999, How People Learn: Brain, Mind, Experience, and School, Washington, D.C.: National Academy of Sciences. Nussbaum, J. 1979, Children’s Conception of the Earth as a Cosmic Body: A Cross Age Study, Science Education, 63, 83. Nussbaum, J., & Novak, J. 1976, An Assessment of Children’s Concepts of the Earth Utilizing Structured Interviews, Science Education, 60, 535. Nussbaum, J., & Sharoni-Dagan, N. 1983, Changes in Second Grade Children’s Preconceptions About the Earth as a Cosmic Body Resulting from a Short Series of Audio-Tutorial Lessons, Science Education, 67, 99. Offerdahl, E. G., Prather, E. E., & Slater, T. F. 2002, Students’ Pre-Instructional Beliefs and Reasoning Strategies About Astrobiology Concepts, Astronomy Education Review, 1(2), 5. http://aer.noao.edu/AERArticle.php?issue=2&section=2&article=1. Parker, J., & Heywood, D. 1998, The Earth and Beyond: Developing Primary Teachers' Understanding of Basic Astronomical Events, International Journal of Science Education, 20, 503. Pasachoff, J. M. 2001, What Should Students Learn?, The Physics Teacher, 39, 381. Pasachoff, J. M. 2002, Pasachoff's Points, The Physics Teacher, 40, 197, 2002a. Pasachoff, J. M. 2002, What Should College Students Learn? Phases and Seasons? Is Less More or Is Less Less?, Astronomy Education Review, 1(1), 124. http://aer.noao.edu/AERArticle.php?issue=1&section=4&article=3, 2002b. Prather, E. E., Slater, T. F., & Offerdahl, E. G. 2002, Hints of a Fundamental Misconception in Cosmology, Astronomy Education Review, 1(2), 28. http://aer.noao.edu/AERArticle.php?issue=2&section=2&article=2. Reed, G., & Campbell, J. R. 1972, A Comparison of the Effectiveness of the Planetarium and the Classroom Chalkboard and Celestial Globe in the Teaching of Specific Astronomical Concepts, School Science and Mathematics, 72, 368. Roettger, E. E. 1998, Changing View of the Universe, Paper presented at the American Association of Physics Teachers Winter Meeting, January, New Orleans, LA. Sadler, P. M. 1992, The Initial Knowledge State of High School Astronomy Students, Unpublished doctoral dissertation, Harvard University, Cambridge, MA. Sadler, P. M. 1998, Psychometric Models of Student Conceptions in Science: Reconciling Qualitative Studies and Distractor-Driven Assessment Instruments, Journal of Research in Science Teaching, 35(3), 265. Sadler, P. M. 2001, Choosing Between Teaching Helioseismology and Phases of the Moon, The Physics Teacher, 39, 554. Sadler, P. M. 2002, Further Discussion, The Physics Teacher, 40, 198. Safko, J. L. 1998, Self-Paced Astronomy at the University of South Carolina—A Twenty-Five Year Retrospect, Poster session presented at the American Association of Physics Teachers Winter Meeting, New Orleans, LA. Samarapungavan, A., Vosniadou, S., & Brewer, W. F. 1996, Mental Models of the Earth, Sun, and Moon: Indian Children's Cosmologies, Cognitive Development, 11(4), 491. Schneps, M. P. 1989, A Private Universe, Video. San Francisco: Astronomical Society of the Pacific. Schoon, K. J. 1992, Students’ Alternative Conceptions of Earth and Space, Journal of Geological Education, 40(3), 209. Shawl, S. J. 2000, 'It’s ONLY a Theory': What Do Students Know About the Scientific Enterprise?, Poster session presented at the 195th Meeting of the American Astronomical Society, January, Atlanta, GA. Skala, C., Slater, T. F., & Adams, J. P. 2000, Qualitative Analysis of Collaborative Learning Groups in Large Enrollment Introductory Astronomy, Publications of the Astronomical Society of Australia, 17, 185. Skam, K. 1994, Determining Misconceptions About Astronomy, Australian Science Teachers Journal, 40(3), 63. Slater, T. F. 2000, K-12 Astronomy Benchmarks from Project 2061, The Physics Teacher, 38, 538. Slater, T. F., & Adams, J. P. 2002, Mathematical Reasoning over Arithmetic in Introductory Astronomy, The Physics Teacher, 40, 268. Slater, T. F., & Adams, J. P. 2003, Learner-Centered Astronomy: Strategies for Teaching ASTRO 101, Upper Saddle River, NJ: Prentice Hall. Slater, T. F., Adams, J. P., Brissenden, G., & Duncan, D. 2001, What Topics are Taught in Introductory Astronomy Courses?, The Physics Teacher, 39, 52. Slater, T. F., Carpenter, J. R., & Safko, J. L. 1996, Dynamics of a Constructivist Astronomy Course for In-Service Teachers, Journal of Geoscience Education, 44, 523. Slater, T. F., Jones, L. V., Bailey, J. M., Jaeggli, S. A., & Lee, A. C. 2003, An Online Interactive Astronomy Course for Non-Science Majors, Poster session presented at the 201st Meeting of the American Astronomical Society, January, Seattle, WA. Slater, T. F., Prather, E. E., Bailey, J. M., & Adams, J. P. 2003, Effectiveness of a Lecture-Tutorial Approach to Large Enrollment Introductory Astronomy, Paper presented at the Annual Meeting of the National Association for Research in Science Teaching, March, Philadelphia, PA. Slater, T. F., Safko, J. L., & Carpenter, J. R. 1999, Long-Term Attitude Sustainability from a Constructivist-Based Astronomy-for-Teachers Course, Journal of Geoscience Education, 47, 366. Sneider, C. I., & Ohadi, M. M. 1998, Unraveling Students' Misconceptions About the Earth's Shape and Gravity, Science Education, 82(2), 265. Sneider, C. I., & Pulos, S. 1983, Children's Cosmographies: Understanding the Earth's Shape and Gravity, Science Education, 67(2), 205. Stahly, L. L., Krockover, G. H., & Shepardson, D. P. 1999, Third Grade Students' Ideas About the Lunar Phases, Journal of Research in Science Teaching, 36(2), 159. Treagust, D. F., & Smith, C. L. 1989, Secondary Students' Understanding of Gravity and the Motion of Planets, School Science and Mathematics, 89(5), 380. Trumper, R. 2000, University Students' Conceptions of Basic Astronomy Concepts, Physics Education, 35(1), 9. Trumper, R. 2001, A Cross-Age Study of Junior High School Students' Conceptions of Basic Astronomy Concepts, International Journal of Science Education, 23(11), 1111, 2001a. Trumper, R. 2001, A Cross-Age Study of Senior High School Students' Conceptions of Basic Astronomy Concepts, Research in Science and Technological Education, 19(1), 97, 2001b. Trumper, R. 2001, A Cross-College Age Study of Science and Nonscience Students' Conceptions of Basic Astronomy Concepts in Preservice Training for High-School Teachers, Journal of Science Education and Technology, 10(2), 189, 2001c. Trundle, K. C., Atwood, R. K., & Christopher, J. E. 2002, Preservice Elementary Teachers' Conceptions of Moon Phases Before and After Instruction, Journal of Research in Science Teaching, 39(7), 633. Trundle, K. C., Atwood, R. K., & Christopher, J. E. 2003, Preservice Elementary Teachers' Conceptions of Moon Phases: A Longitudinal Study, Paper presented at the Annual Meeting of the National Association for Research in Science Teaching, March, Philadelphia, PA. Vosniadou, S., & Brewer, W. F. 1987, Theories of Knowledge Restructuring in Development, Review of Educational Research, 57(1), 51. Vosniadou, S., & Brewer, W. F. 1992, Mental Models of the Earth: A Study of Conceptual Change in Childhood, Cognitive Psychology, 24(4), 535. Vosniadou, S., & Brewer, W. F. 1994, Mental Models of the Day/Night Cycle, Cognitive Science, 18(1), 123. Wall, C. A. 1973, A Review of Research Related to Astronomy Education, School Science and Mathematics, 73(8), 653. Wandersee, J. H., Mintzes, J. J., & Novak, J. D. 1994, Research on Alternative Conceptions in Science, In Handbook of Research on Science Teaching and Learning, D. L. Gabel (Editor), New York: MacMillan Publishing, 177. Yost, M. 1973, Similarity of Science Textbooks: A Content Analysis, Journal of Research in Science Teaching, 10(4), 317. Zeilik, M. 1974, A PSI Astronomy Course, American Journal of Physics, 42(12), 1095. Zeilik, M. 1981, Flexible, Mastery-Oriented Astrophysics Sequence, American Journal of Physics, 49(9), 827. Zeilik, M. 1998, Interactive Lesson Guide for Astronomy, Revised Ed., Santa Fe, NM: The Learning Zone. Zeilik, M. 2002, Birth of the Astronomy Diagnostic Test: Prototest Evolution, Astronomy Education Review, 1(2), 46. http://aer.noao.edu/AERArticle.php?issue=2&section=2&article=5. Zeilik, M., & Bisard, W. J. 2000, Conceptual Change in Introductory-Level Astronomy Courses, Journal of College Science Teaching, 29(4), 229. Zeilik, M., Schau, C., & Mattern, N. 1998, Misconceptions and Their Change in University Astronomy Courses, The Physics Teacher, 36, 104. Zeilik, M., Schau, C., & Mattern, N. 1999, Conceptual Astronomy. II. Replicating Conceptual Gains, Probing Attitude Changes Across Three Semesters, American Journal of Physics, 67(10), 923. Zeilik, M., Schau, C., Mattern, N., Hall, S., Teague, K. W., & Bisard, W. J. 1997, Conceptual Astronomy: A Novel Model for Teaching Post-Secondary Science Courses, American Journal of Physics, 65, 987. Dr. C. Renee James NASA Top Stars 2010

  7. Sounds reasonable enough… • My very first “Stars & Galaxies” class ran in fall 2006. • After having attended a workshop on learner-center astronomy during Summer 2006, I was determined to give it a shot. • I began the semester with the following slide: Dr. C. Renee James NASA Top Stars 2010

  8. 0 A jillion points of light (stars)What can you tell from just this picture? Are all stars the same? What’s different? WHAT SPECIFIC INFORMATION DO YOU THINK WOULD HELP YOU UNDERSTAND MORE ABOUT THESE STARS? Dr. C. Renee James NASA Top Stars 2010

  9. First group assignment: • Name five things that you can tell about NGC 6397 JUST BY LOOKING AT THIS PHOTO. Think small (very small) like a child. Dr. C. Renee James NASA Top Stars 2010

  10. At this point, the class chats. • I encourage them to exchange contact information so that they have study partners. • I tell them that no observation is too obvious. • I warn them that some conclusions cannot be made on the basis of the photo. Dr. C. Renee James NASA Top Stars 2010

  11. What the students said: • You can tell stars are different colors. • Stars look different sizes or brightnesses. (at which point I ask if they can really determine size or absolute brightness) • Stars are really clumped together in the middle of the picture. • Some stars look closer than others. (at which point I ask if they can really determine distance) • Orange stars tend to be brighter and bigger-looking than white stars. Dr. C. Renee James NASA Top Stars 2010

  12. Phew – one collaboration down. Now what? Oh yes…inquiry based learning. • I want my students to ‘own’ the class from the first day, so I let them decide the direction of class from there with the following question: Dr. C. Renee James NASA Top Stars 2010

  13. 0 NOW DECIDE WHAT YOU WANT TO KNOW • WITH YOUR GROUP decide what aspect of this photo you think will best help you understand it. Dr. C. Renee James NASA Top Stars 2010

  14. And the nominees are… • The piece of information that will help us understand more about this picture is… • Why so many? • Why different colors? • How far from us? Distance norms? • Why brighter/dimmer? • Why clustered in the middle/dispersed outside? • Why appear different sizes? • Can you tell temps? • How far from each other? • How old? Dr. C. Renee James NASA Top Stars 2010

  15. MY SECRET WEAPON • I don’t tell the students this, but there are typically only two basic things they will ever want to explore: Distances (or anything spatial about the picture) or light (anything relating to the colors or brightness). I prepare the two “lectures” ahead of time, but it’s up to them which one they begin with. • Then I hold a vote. This semester they chose… Dr. C. Renee James NASA Top Stars 2010

  16. WHICH ONE?? 1.Light 2. Distances Dr. C. Renee James NASA Top Stars 2010

  17. At this point, they think they’ve probably seen the last of NGC 6397. • Boy are THEY wrong! BWAHAHAHAA! • To be honest, though, I had no idea that this image would get so enmeshed in my entire semester. • For the classes that begin exploring light, we play with light bulbs on dimmer switches and get some info about color/temperature/brightness relationships. • Once that’s done, I ask the following: Dr. C. Renee James NASA Top Stars 2010

  18. 0 Two stars are exactly the same size and distance from us. One appears orange. The other appears white. ASSUMING THAT STARS BEHAVE LIKE LIGHT BULBS, which one do you THINK will appear brighter? • The orange one • The white one • They’ll both be the same brightness • Need more information Dr. C. Renee James NASA Top Stars 2010

  19. Voting Questions • The previous slide is an example of a ‘voting question’ that I present often in class. • Students simply hold the number of fingers to their chest to indicate their answer. • If the vote is mostly correct, we can move on. If not, well…looks like I need to explain things better. • Then I hit them with this: Dr. C. Renee James NASA Top Stars 2010

  20. 0 Do THESE behave the way you expect if stars act like light bulbs? If not, what is different from what you expect? Dr. C. Renee James NASA Top Stars 2010

  21. Thank you, NGC 6397 • One of the more obvious features in this Hubble photo is that the orange stars tend to appear brighter. And yet my students have found that for light bulbs, white is brighter than orange. • This leads to possible solutions: • Orange stars in that photo are closer • Orange stars in that photo are bigger • Stars don’t behave like light bulbs Dr. C. Renee James NASA Top Stars 2010

  22. SEVERAL CLASSES LATER… • Students are convinced that stars do in fact get their colors from their temperatures and not from their composition (e.g. discharge tubes like neon or helium lights), leaving only the size and distance issues. • We explore size first with an group exercise from Prather, et al’s Lecture Tutorials for Intruductory Astronomy. • Then we see the cluster again… Dr. C. Renee James NASA Top Stars 2010

  23. 0 Orange stars – like orange light bulbs – are cool.>So each square inch of an orange star is DIMMER than each square inch of a white star. >But there are zillions more square inches in these orange stars (not a general rule about orange stars) Dr. C. Renee James NASA Top Stars 2010

  24. If you’re keeping score at home… • We’ve now looked at the image of NGC 6397 three times in class, and we’re only a few days into the semester. • Students are suggesting that we give it a new name like “Bob.” • Might not be a bad idea because, after all… Dr. C. Renee James NASA Top Stars 2010

  25. Her name is Polly Puffball. I can keep her…Right, Mom? …naming things gives them a special place in your heart. But…is it possible that NGC 6397 would ever hold a special place in their hearts? Hmmm… Dr. C. Renee James NASA Top Stars 2010

  26. Back to Bob…er, NGC 6397 • It IS still possible that the orange stars are simply closer (although that’s a really creepy proposition since they’d be ganging up on us). • So we spend some time going over stellar distance determinations via parallax. • Everyone’s happy with parallax because you can personally observe “finger parallax.” Dr. C. Renee James NASA Top Stars 2010

  27. Then the hammer falls… • At 8200 light years, Bob is too far away for our current technology to detect stellar parallax. • But somehow we KNOW how far away it is. • Is Bob lying to us?? Dr. C. Renee James NASA Top Stars 2010

  28. This opens another door • Parallaxes and colors are just the first step. • Now we can explore stellar spectra, including spectral types and luminosity classes, always hearkening back to Bob. • Spectroscopic parallax can be applied to this cluster, yielding a distance. • In addition, we can explore Bob’s HR Diagram. Dr. C. Renee James NASA Top Stars 2010

  29. So many awesome features to figure out! From “The CM diagram of the nearby globular cluster NGC 6397” 1987. AJ, vol 94. Authors:Alcaino, G.; Buonanno, R.; Caloi, V.; Castellani, V.; Corsi, C. E.; Iannicola, G.; Liller, W. Dr. C. Renee James NASA Top Stars 2010

  30. Questions from the students include… • What the heck is B-V? • Why isn’t this a pretty HR Diagram like the ones in the book? • Why does the main sequence just quit halfway up? • Why is there a “wishbone” shape in the upper right? • What are the stars that look like they’re in the main sequence, but hotter? Dr. C. Renee James NASA Top Stars 2010

  31. Clearly Bob is thwarting their attempts to understand stars • Fortunately, we can then go into stellar masses, stellar evolution, main sequence turnoffs, and how to determine cluster ages (pretty standard for intro astronomy course) • But we ALSO can go into blue stragglers, age determination from white dwarfs (which are plentiful in Bob), and a host of other more “cutting edge” topics that arise from studying this cluster. Dr. C. Renee James NASA Top Stars 2010

  32. Assessing the Value of Bob • It’s all well and good to say Bob has dominated the semester, but how does this get assessed? • Informally via voting questions and group work, such as listing what can be determined about Bob. • Formally via homework and exam questions. • Here are some examples (in slide form): Dr. C. Renee James NASA Top Stars 2010

  33. The next slide is a group discussion question Dr. C. Renee James NASA Top Stars 2010

  34. 0 BACK TO THAT FIRST PICTURE… • ALL of the stars in this photo have essentially the same PARALLAX. • WHAT DOES THIS TELL YOU ABOUT THE ACTUAL BRIGHTNESS OF THESE OBJECTS? • What do you think this means about their relative SIZES? Dr. C. Renee James NASA Top Stars 2010

  35. The next two slides are sample voting questions from class Dr. C. Renee James NASA Top Stars 2010

  36. 0 Bob has a distance of 8200 light years. Approximately what is the parallax to one of its stars? • 1/8200 arcseconds • 8200 arcseconds • 1/2700 arcseconds • 2700 arcseconds • Need more info Dr. C. Renee James NASA Top Stars 2010

  37. 0 • If Bob’s orange stars • have an apparent • magnitude of 12.3, • what would be an • appropriate apparent • magnitude for the • white ones? • 16 • 12.3 • 9 Dr. C. Renee James NASA Top Stars 2010

  38. Another discussion question, followed quickly by a voting question, and some more discussion (Bob really takes over this class day): Dr. C. Renee James NASA Top Stars 2010

  39. 0 The HR Diagram for Bob • In your groups, list some features that you can see in this diagram. Which ones are unexpected? • What do you want to learn next? Dr. C. Renee James NASA Top Stars 2010

  40. From Bob’s HR-Diagram: • No stars hotter than B-V of about 0.5 on MS • This is equivalent to spectral type F7, give or take. • Sun is G2V, and has a mass of 1.0 solar masses (by definition). Dr. C. Renee James NASA Top Stars 2010

  41. 0 What does this say about the masses of Bob’s Main sequence stars? • There are no MS stars more massive than about 1.4x the mass of the Sun • There are no MS stars less massive than about 1.4x the mass of the Sun the Sun • The MS stars in NGC 6397 have a wide range of masses from much more to much less massive than the Sun Dr. C. Renee James NASA Top Stars 2010

  42. 0 • CAN YOU THINK OF ANY POSSIBLE REASONS WHY THIS CLUSTER DOESN’T HAVE ANY MAIN SEQUENCE STARS GREATER THAN 1.4 SOLAR MASSES? • DISCUSS… • (Proposed solutions typically include possibility that cluster is too YOUNG and high-mass stars haven’t formed yet; too OLD and high-mass stars have died; region of the galaxy was abnormal and high-mass stars couldn’t form to begin with. Or a giant space echidna ate them.) Dr. C. Renee James NASA Top Stars 2010

  43. And, after a couple of weeks of stellar formation and evolution, a couple more voting questions. Dr. C. Renee James NASA Top Stars 2010

  44. Why doesn’t Bob have any stars greater than 1.4 solar masses on the main sequence? • The cluster is too young to have pulled enough material to form high-mass stars. • The higher mass stars are too dim to see. • The higher mass stars have already used up their core hydrogen fuel and left the MS. • The higher mass stars broke apart into low-mass stars. Dr. C. Renee James NASA Top Stars 2010

  45. 0 BOB • MS ends around B-V = +0.5 • This is about spectral type F7. • Sun is G2. IS NGC6397 1) older than 2) younger than 10 billion years old?? Dr. C. Renee James NASA Top Stars 2010

  46. Then the inevitable… Dr. C. Renee James NASA Top Stars 2010

  47. Here lies Bob. But before we bid adieu to our friend Bob (nee NGC 6397), let’s say some kind words about it… Dr. C. Renee James NASA Top Stars 2010

  48. Goodbye, Bob. We’ll miss you. We really enjoyed finding out about your… • (and the students get together and list EVERYTHING that they have learned about this cluster from day one through this point in class, which is about 9 or 10 weeks later. They are truly astonished at how much of a stars and galaxies class can be pulled together from just one cluster and a simple question at the beginning of the semester). Dr. C. Renee James NASA Top Stars 2010

  49. AND HERE’S WHAT THEY LIST: LuminosityTemperatureSizeMagnitudes (absolute and apparent)Parallax and Spectroscopic ParallaxStellar MassesStellar EvolutionAge of the clusterWhite dwarfsBlue Stragglers…and much, much more! Dr. C. Renee James NASA Top Stars 2010

  50. Good ol’ Bob… • Virtually half of a college-level introductory astronomy class for non-majors derives from a single photo from the Hubble Heritage. • Bob turns out to be quite the conceptual anchor (and not so much of a ‘bob.’) Dr. C. Renee James NASA Top Stars 2010

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