the life and death of bob (a.k.a. ngc 6397) in an introductory college-level astronomy course dr. c....

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

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…


I know! I’ll just scour the Hubble Heritage Site for something cool-looking that relates to

stars and galaxies.


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...


• 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?

My new friend: NGC 6397http://heritage.stsci.edu/2003/21/index.html


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.

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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:


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?


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.


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.


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.


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:


NOW DECIDE WHAT YOU WANT TO KNOW

• WITH YOUR GROUP decide what aspect of this photo you think will best help you understand it.


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?


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…


WHICH ONE??

1.Light

2. Distances


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:


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?

1. The orange one

2. The white one

3. They’ll both be the same brightness

4. Need more information


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:


Do THESE behave the way you expect if stars act like light bulbs?

If not, what is different from what you expect?


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


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…


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)


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…


…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…

Her name is Polly Puffball. I can keep her…Right, Mom?


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.”


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

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.


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.


http://adsabs.harvard.edu/cgi-bin/author_form?author=Alcaino,+G&fullauthor=Alcaino,%20G.&charset=UTF-8&db_key=AST


http://adsabs.harvard.edu/cgi-bin/author_form?author=Buonanno,+R&fullauthor=Buonanno,%20R.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Buonanno,+R&fullauthor=Buonanno,%20R.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Caloi,+V&fullauthor=Caloi,%20V.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Caloi,+V&fullauthor=Caloi,%20V.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Castellani,+V&fullauthor=Castellani,%20V.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Castellani,+V&fullauthor=Castellani,%20V.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Corsi,+C&fullauthor=Corsi,%20C.%20E.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Corsi,+C&fullauthor=Corsi,%20C.%20E.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Iannicola,+G&fullauthor=Iannicola,%20G.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Iannicola,+G&fullauthor=Iannicola,%20G.&charset=UTF-8&db_key=AST

http://adsabs.harvard.edu/cgi-bin/author_form?author=Liller,+W&fullauthor=Liller,%20W.&charset=UTF-8&db_key=AST



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?


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.


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):


The next slide is a group discussion question


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?


The next two slides are sample voting questions from class


Bob has a distance of 8200 light years. Approximately what is the

parallax to one of its stars?

1. 1/8200 arcseconds

2. 8200 arcseconds

3. 1/2700 arcseconds

4. 2700 arcseconds

5. Need more info


If Bob’s orange starshave an apparentmagnitude of 12.3, what would be anappropriate apparentmagnitude for the white ones?

1)162)12.33) 9


Another discussion question, followed quickly by a voting

question, and some more discussion (Bob really takes over

this class day):


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?


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).


What does this say about the masses of Bob’s Main sequence stars?

1. There are no MS stars more massive than about 1.4x the mass of the Sun

2. There are no MS stars less massive than about 1.4x the mass of the Sun the Sun

3. The MS stars in NGC 6397 have a wide range of masses from much more to much less massive than the Sun


• 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.)


And, after a couple of weeks of stellar formation and evolution, a

couple more voting questions.


Why doesn’t Bob have any stars greater than 1.4 solar masses on the

main sequence?1. The cluster is too young to have pulled

enough material to form high-mass stars.

2. The higher mass stars are too dim to see.

3. The higher mass stars have already used up their core hydrogen fuel and left the MS.

4. The higher mass stars broke apart into low-mass stars.


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??


Then the inevitable…


Here lies Bob.

But before we bid adieu to ourfriend Bob (nee NGC 6397), let’s say some kind words about it…


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).


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!


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.’)


REFERENCES

• How to locate Bob: http://heritage.stsci.edu/2003/21/index.html

• And his HR Diagram:

“The CM diagram of the nearby globular cluster NGC 6397” 1987. AJ, vol 94. ByAlcaino, G.; Buonanno, R.; Caloi, V.; Castellani, V.; Corsi, C. E.; Iannicola, G.; Liller, W.


http://heritage.stsci.edu/2003/21/index.html



Educational Resources (in slightly larger font than before)

• 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., 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.


• Ball, N., Coyle, H. P., & Shapiro, I. I. (Eds.). 1994, Project SPICA: A Teacher Resource to Enhance Astronomy Education, Dubuque, IA: Kendall-Hunt Publishing.

• 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.

• 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.

• 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.


• Finegold, M., & Pundak, D. 1990, Students' Conceptual Frameworks in Astronomy, Australian Science Teachers Journal, 36, 76.

• Fraknoi, A. 1998, Astronomy Education: A Selective Bibliography, Retrieved April 6, 2003, from http://www.astrosociety.org/education/resources/educ_bib.html.

• 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.

• Kikas, E. 1998, The Impact of Teaching on Students' Definitions and Explanations of Astronomical Phenomena, Learning and Instruction, 8, 439.

• Lightman, A., & Sadler, P. M. 1993, Teacher Predictions Versus Actual Student Gains, The Physics Teacher, 31, 162.

• Maran, S. P. 2000, 'Hot Topics' in Astrophysics, The Physics Teacher, 38, 550. • 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. • 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.

• 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.

• Schneps, M. P. 1989, A Private Universe, Video. San Francisco: Astronomical Society of the Pacific.

• 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., & 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., 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.


• 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.

• Vosniadou, S., & Brewer, W. F. 1987, Theories of Knowledge Restructuring in Development, Review of Educational Research, 57(1), 51.

• 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., 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.

I think that about does it….


APPENDIX

• The following slides are taken directly from the first couple of days of the semester (assuming they choose “light” as the direction at the beginning of class)

• If you would like to see how NGC 6397 keeps cropping up in my classes, or if you wish to see how I tackle a vote of “distance,” feel free to contact me.


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?


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.


Now for a more involved group assignment:

• Several things might help you better understand that picture. For instance, finding out what makes the stars different colors could help, or perhaps if you knew how far away these things are from Earth, or if you knew about the actual sizes of these dots... There are tons of things that could help you find out what’s really being shown in this picture.

• WITH YOUR GROUP – come up with WHAT YOU WANT TO KNOW ABOUT THIS PICTURE and what that knowledge will help you understand. For example, “I want to know how fast sound travels. That way I can tell how far away a lightning strike is simply by counting the seconds until the sound (thunder) gets to me.”


And the class vote is…• The piece of information that will help us

understand more about this picture is…– (students offer their answers)


WHICH ONE??

1.Light

2. Distances


IN YOUR EXPERIENCE what causes things to appear

orange?• (again, students offer their own observations, but

here’s what I got last semester)• Paint, orange – reflecting stuff.

– YOU’LL HAVE TO TAKE MY WORD FOR NOW THAT THE STARS ARE NOT REFLECTING LIGHT LIKE MARS DOES. They make their own.

• Fire, neon sign, stove burner, glow in the dark thingies – stuff that makes its OWN light.

vDr. C. Renee James NASA Top Stars 2010

So what kind of info can we get from things giving off their own

light? Let’s start simple…• An incandescent (filament) light bulb on dimmer

switch. • Turn it low. Look at it. Put your hand near it.

What does it look like (color, brightness)? How hot does it feel (warmish, hot, very hot)?

• Turn it medium. • Turn it high.• What conclusions can you draw about objects that

behave like LIGHT BULBS?Dr. C. Renee James NASA Top Stars 2010

RESULTS

COLOR BRIGHTNESS TEMP

LOW Orange Dim Lukewarm

MED Whitish orangeish yellowish beige salmony color.

Kinda brighter Warm to hot

HIGH White Blinding Really hot


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?

1. The orange one

2. The white one

3. They’ll both be the same brightness

4. Need more information


Do THESE behave the way you expect if stars act like light bulbs?

If not, what is different from what you expect?


COLOR = TEMPERATURE?• From light bulbs, we see a nice correlation

between color and temperature (white = OW!; yellow = hot; orange = coolish)

• Temperature also affects BRIGHTNESS.

• But the orange stars in the photo tend to be BRIGHT, rather than dim; the white stars tend to be DIM, rather than bright.– So maybe stars DON’T behave like light bulbs.


Let’s look at a different type of light source:

• “Discharge” tubes (hydrogen, mercury, helium).• Different composition tubes appear different colors.• What does spectrum (as seen through the diffraction

grating) look like?• What does a normal LIGHT BULB look like through

diffraction grating? [all students have a diffraction grating passed out to them at the beginning of class]


2 Mechanisms to Produce Light• One relates to TEMPERATURE (e.g. light bulb)

and gives continuous spectrum:

• Other relates to COMPOSITION (e.g. discharge tubes) and gives emission spectrum:

• So which one is responsible for the different colors of stars?


Do stars display a spectrum more like the emission spectrum or more

like a light bulb’s spectrum?

• You’ve probably all seen at least one star’s spectrum in your lives.

• Which star? What does its spectrum look like? [they’ll usually get it after a tiny bit of prompting]


STELLAR SPECTRUM = RAINBOW!

• Sun gives one off.• Stars do, too.

(to a first approximation, at least, but all those dark lines have to wait for another class)


Now it’s time for a fleet of voting questions. Personal response

devices ready???? [in my classes, the students use their hands to

indicate their answers]


A light bulb's color is a result of its... 1. composition 2. temperature

A discharge tube (e.g. those long glass tubes I plugged into that big power supply) gets its color from its... (Same choices as above)


A light bulb's spectrum looks like ____, while a discharge tube's spectrum looks like ___.1. a rainbow; a rainbow2. a series of different colored lines; a series of different colored lines3. a rainbow; a series of different colored lines

4. a series of different colored lines; a rainbow


A STAR'S spectrum (think of the Sun) looks like...1. a rainbow 2. a series of different colored lines

THEREFORE a star's light must be produced the same way a _____'s light is produced.1. light bulb 2. discharge tube


AND THIS MEANS a star's color is related to its...1. temperature 2. composition


WHAT HAVE WE FOUND OUT SO FAR?

• We’ve demonstrated that the Sun and stars produce light the same way that a LIGHT BULB does.

• (but we haven’t shown that the sun is a star. We also haven’t shown that the Sun is a light bulb)

• Thus their COLORS must be related to their TEMPERATURES, not their compositions.

• But then we still have a problem…Dr. C. Renee James NASA Top Stars 2010

SO HOW CAN THE ORANGE STARS BE THE BRIGHT ONES???

• Lower temp light bulb = orange, but dim.

• Higher temp light bulb = white, but bright.

• In NGC 6397, orange stars are the bright ones, not the dim ones.

• ??????? ANY IDEAS????? [again, class discussion ensues]


• Now it’s time to get into the Lecture Tutorials. Please get with a couple of people and work your way through questions 1-9 pp 53-55. Take this and all LT exercises pretty seriously – it’ll all come back to haunt you. (BWAHAHAHAHA!!)

• Dr. Miller has made a series of videos to help illustrate astronomical concepts: http://video.google.com/videoplay?docid=6690730625344739278&ei=YKy-SKuMH4zq-AGyl_31CQ&q=%22astronomy+001%22


LUMINOSITY• Fancy term for how much energy a star is

pumping out each second.

• Does NOT depend on distance (it’s the WATTAGE. A 100-W light bulb is still 100-W light bulb even if it’s in Chicago)

• TWO THINGS INFLUENCE LUMINOSITY. You can make a star MORE LUMINOUS by doing what?


Still assuming that stars behave like light bulbs, how can an orange star

APPEAR brighter than a white star?

1. The orange star is more distant

2. The orange star is larger

3. The orange star is hotter

4. There is no mystery here – from what we know of light bulbs, orange stars SHOULD be brighter than white stars.


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)


How big are they?

The harsh reality:

The Sun compared to

a red giant


CONCLUSIONS• Light bulbs, the Sun, and stars give off continuous

spectra (i.e. rainbows)– Colors of these objects arise from differences in

temperature, not composition.

– This is not yet conclusive evidence that the Sun is a star, though!

• Can make light bulbs – or STARS – brighter by increasing temp OR size. – Orange stars in the photo in question are cool, but

HUGE! (they’re red giants, in fact)


the life and death of bob (a.k.a. ngc 6397) in an introductory college-level astronomy course dr. c....

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