(PDF) Decoding Starlight: From Pixels to Images

The Earth Scientist Volume XXVIII • Issue 1 • Spring 2012 $10.00* FREE IN Stellar Li SIDE fe Cy color car cles d set This composite image and illustration shows supernova remnant E0102, the remains of the core collapse of a massive star in the neighboring Small Magellanic Cloud galaxy about 190,000 light years away. Similar supernova events within the Milky Way Galaxy are part of the stellar evolution cycle that provide the conditions for planets to form, create the elements necessary for life, and emit radiation that can impact Earth. Supernova E0102 is a composite image of observations from the Chandra X-Ray Observatory and Hubble. Image courtesy of Chandra. For more about the Chandra mission, visit http://chandra.si.edu    INSIDE THIS ISSUE From the President . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Pulsating Variable Stars and the Hertzsprung-Russell Diagram . . 20 From the Executive Director . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Investigating Supernova Remnants. . . . . . . . . . . . . . . . . . . . . . . 27 Editor’s Corner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Advertising in The Earth Scientist. . . . . . . . . . . . . . . . . . . . . . . . 32 Decoding Starlight: From Pixels to Images. . . . . . . . . . . . . . . . . . 7 Manuscript Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Ice Core Records – From Volcanoes To Supernovas. . . . . . . . . . 12 Membership Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Transit of Venus – June 5, 2012. . . . . . . . . . . . . . . . . . . . . . . . . . 18 *ISSN 1045-4772 This special themed issue is sponsored by the Chandra X-Ray Observatory’s Education and Public Outreach Office Page 2 The Earth Scientist From the President by Ardis Herrold, NESTA President 2010 – 2012 In Memoriam: NESTA’S MISSION Dr. Harold B. Stonehouse I To facilitate and advance excellence in Earth and Space t has always seemed to me one of the great injustices of life that special people can’t live on Science education. forever. So with some sense of sadness I mark the passing of Dr. Harold B. Stonehouse, one of the founders of the National Earth Science Teachers Association and its first Executive Advisor. NESTA Contacts Although he held a PhD in Geology and many leadership positions, I chuckle to think of calling EXECUTIVE BOARD him “Dr. Stonehouse.” “Stoney” was his familiar name, and well-suited for him because he was one of the most down to earth (no pun intended) academic types I have known. He was not an eloquent President speaker. He did not thrive on power. He always seemed to have a harmonious balance of work and Ardis Herrold

fun, and a respect for everyone, regardless of their state in life. President-Elect Missy Holzer Yet at the same time he was the

consummate professional. His career encompassed an amazing variety of Secretary experiences. His entrance exams for the Jenelle Hopkins Royal School of Mines were interrupted

by an air raid over England in 1939. He Treasurer mined tin in Nigeria, gold in South Howard Dimmick America and nickel in Canada. He did his

thesis research on the origin of the ore emplacement in the Sudbury Basin, grad- Past-President Stoney at the Charter meeting of NESTA in Dallas, Texas uating with a Ph.D. from the University on April 9, 1983 in Room E408 of the Dallas Convention Michael J Passow of Toronto in 1952.  He majored in Center. The second NESTA president, Sharon Stroud is in the

background just to Stoney’s left.   Geochemistry with minors in Economic Photo courtesy of Jan Woerner. Board of Directors Geology and Mineralogy.  In 1955 Stoney Representative became a professor at Michigan State Parker Pennington IV University, where he taught until 1989.

At Michigan State he became especially Executive Director, involved with the aspects of Earth Association Contact Science education. He was a Fulbright Dr. Roberta Johnson Fellow in Earth Science Education in

the Philippines in 1973 and was advisor to the Crustal Evolution Education The NESTA office is located at: Project. Stoney also served as director of 4041 Hanover St., Suite 100 numerous NSF institutes for teachers, Boulder, CO 80305 participated in state (of Michigan) PO Box 20854 education committees and served on the Boulder, CO 80308-3854 boards of the Michigan and National Phone: 720-328-5351 Earth Science Teachers for many years. Jan and Stoney after their helicopter flight from Hilo, Hawaii over Fax: 720-328-5356 He studied neuro-linguistic program- Kileaua volcano in Hawaii in 2006. Visit the NESTA website at http://www.nestanet.org ming (NLP) for 15 years, becoming an Photo courtesy of Jan Woerner. © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 3 NLP Master Practitioner. (I still NESTA Contacts use some of the eye-brain strategies Stoney taught me.) REGIONAL DIRECTORS Central Region - IL, IA, MN, Stoney spent many years in leader- MO, WI ship positions in NESTA, with the Chad Heinzel

Michigan Earth Science Teachers Association (MESTA), the Michigan East Central Region - IN, KY, MI, OH and National Science Olympiads, Jay Sinclair and the National Association of

Geoscience Teachers. In addition Eastern Region - DE, NJ, PA Michael Smith to helping to begin NESTA, he

later founded the California Earth Far Western and Hawaii Science Teachers Association. Region - CA, GU, HI, NV Wendy Van Norden Yet Stoney probably accomplished

twice as much tangentially as he did Mid-Atlantic Region - DC, MD, Jan and Stoney visiting the pyramids in Egypt in September 2010. directly. He was great at spinning Camels are difficult to “ride.”  Stoney didn’t get up on one, he just VA, WV watched as the camel driver led the beast around, toward the pyramids Michelle Harris off ideas and getting other people

to implement them. As a young and back again.  It was about 110°F or more at the time this photo was taken. New England Region - CT, ME, teacher I was prodded by Stoney Photo courtesy of Jan Woerner. MA, NH, RI, VT into giving teacher workshops Lisa Sarah Alter

and then into leadership roles in MESTA and later NESTA. Think about how one teacher impacts New York Region - NY many students. Then think how one teacher–presenter impacts many teachers. Add in the “Stoney Gilles Reimer factor”, and you have one man who inspired many teachers to help teachers. You can see the expo-

nential benefits. North Central Region - MT, NE, ND, SD, WY Stoney had little tolerance for stupidity, and no qualms about breaking rules or traditions if they VACANT didn’t make sense…Especially if they didn’t make sense. He had a keen understanding of leader- Northwest Region - AK, ID, OR, ship –both how to inspire, and how to optimize the potentials of those on the team. He continued WA & British Columbia Steve Carlson to serve even after retirement, working with both the Adult Literacy program and the coordinating

one of the best AARP Tax Aide programs in California. He cared deeply about people and this was South Central Region - AR, KS, most obvious when he talked about his wife, Dr. Jan Woerner. A few years ago Stoney described an LA, OK, TX upcoming trip to Egypt saying that he and Jan were going “to play Anthony and Cleopatra.” Kurtis Koll

NESTA’s highest award, the “Jan and Stoney Award” is given biennually to recognize outstanding Southeastern Region - AL, FL, individuals who, like Jan and Stoney, have dedicated so much of their lives to advance Earth Science GA, MS, NC, PR, SC, TN Dave Rodriguez education. MESTA also annually awards teacher mini-grants, named the “Stoney Awards”.

What will I remember most? When I think about Stoney, I naturally think about rocks. One of the Southwest Region - AZ, CO, NM, UT awesome aspects of rocks is their longevity compared to our short time on the crust. In a similar Pamela Whiffen way, Stoney’s works will long persevere, just as his name implies.

Appointed Directors Ardis Herrold Tom Ervin –

NESTA President, 2010-2012 Ron Fabich –

Parker Pennington IV –

Rick Jones –

Joe Monaco –

© 2012 National Earth Science Teachers Association. All Rights Reserved. Page 4 The Earth Scientist NESTA Coordinators From the Executive Director Dear NESTA Members, Affiliates Coordinator Ron Fabich NESTA has a very full schedule of events planned for the Spring NSTA National Conference in Conference Logistics Indianapolis, Indiana, 28 - 31 March 2012. Please see our full page announcement elsewhere in this Coordinators issue for details on our events at the conference. We’ve made some significant changes in our menu Kim Warschaw of offerings this year: Michelle Harris n We are offering two field trips – one full day field trip on Wednesday, and an afternoon ½ day Membership Coordinator field trip on Thursday. Bruce Hall n Instead of offering a NESTA breakfast on Saturday morning, this year we are offering the Merchandise Coordinator NESTA Earth and Space Science Educator Saturday Luncheon. Howard Dimmick Procedures Manual n In addition to our regular and very popular Share-a-Thons and Rock and Mineral Raffle, Coordinator to accommodate our membership’s responses on our recent survey, NESTA is also offering Parker Pennington IV multiple topical workshops. Rock Raffle Coordinators n Thanks to NSTA’s assistance, this year we are able to conveniently offer almost all of our Parker Pennington IV sessions in the same room! Thanks NSTA! Kimberly Warschaw This year, we have numerous organizations and individuals to thank for their support for our activi- Share-a-thon Coordinator ties at the spring conference: Michelle Harris Volunteer Coordinator Diamond Sponsor Joe Manaco The American Geophysical Union for their continuing support of our advertisement in the Webpage Coordinator NSTA program, through which we also promote the AGU Lecture, on Friday, 30 March at 2 Jack Hentz pm, by Prof. Gabriel Filippelli, who will be speaking on FrankenClimate: The Perils of Engineering

Our Way Out of Global Warming E-News Editors Missy Holzer Platinum Sponsors Richard Jones Google Earth and the American Meteorological Society, both of which are generously providing financial support for all of NESTA’s programs at the NSTA conference. Gold Sponsor Purdue University Department of Earth and Atmospheric Science, for their generous financial support for a bus for our full-day field trip on March 28th, as well as their in-kind support provided by printing and binding the field guides for our field trips. This support has made it possible to offer our field trips this year at a bargain rate! A special shout-out to Dr. Steven Smith, K-12 Outreach Coordinator in the department, for his tremendous assistance with all things field trip! Silver Sponsors n The American Geosciences Institute for their financial support of the Friends of Earth Science Reception on Friday evening. I’d also like to remind you all that the AGI Edward C. Roy, Jr. Award For Excellence in K-8 Earth Science Teaching will be awarded at this event on Friday evening – don’t miss it! n Carolina Biological, for their continuing financial support of NESTA’s NSTA National conference program, as well as for consistently contributing wonderful specimens to the Rock and Mineral Raffle. © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 5 Share-a-Thon Sponsors n Earth Science Information Partners (ESIP), for their sponsorship of our Earth System Science and Atmospheres, Oceans, and Climate Change The Earth Scientist Share-a-Thons. EDITOR Tom Ervin n Incorporated Research Institutions for Seismology (IRIS), for their spon- PUBLICATIONS COMMITTEE sorship of our Geology Share-a-Thon. Linda Knight, Chair Tom Ervin, TES Editor n Northrup Grumman, for their support of our Earth System Science Parker Pennington IV Share-a-Thon. Howard Dimmick Ardis Herrold Speakers Missy Holzer Richard Jones Thanks to the Consortium for Ocean Leadership, and specifically Jennifer Collins there, who was a great help with lining up our speakers for the conference CONTRIBUTING AUTHORS Troy Cline, Elaine Lewis, Doug Lombardi, in Indianapolis! They are also generously providing dessert for us at the NESTA Sten Odenwald, Donna Young Earth and Space Science Educator Luncheon on Saturday! The Earth Scientist is the journal of the National Earth Science Teachers Association Without the support of these organizations and of many other volunteers, NESTA (NESTA). would not be able to put together such a packed program, with so many exciting events The Earth Scientist is published quarterly (January, for focused on teachers. Thanks to all of you for your efforts! March, June, September) and distributed to NESTA members. Back issues of The Earth Best Regards, Scientist are available for sale through the NESTA Office for $10 per copy. Dr. Roberta Johnson Advertising is available in each issue of The Earth Scientist. If you wish to advertise, visit http://www. Executive Director, NESTA nestanet.org/cms/content/publications/tes/ advertising. Editor’s Corner To become a member of NESTA visit www. nestanet.org. To get more information about NESTA or Welcome to this special issue of The Earth Scientist sponsored by the Chandra X-Ray advertising in our publications, or to get copies Observatory’s Education and Public Outreach Office! The Chandra mission was of back issues, contact the NESTA Office at 720-328-5351 or

launched July 23, 1999 and has been providing astronomers and the public with Copyright © 2012 by the National Earth Science valuable insights to the X-ray portion of the universe ever since. Accompanying the Teachers Association. All rights thereunder spectacular scientific discoveries are a host of efforts to help students, teachers, and the reserved; anything appearing in The Earth Scientist may not be reprinted either wholly or in part public learn about both Chandra itself and the objects it observes. In this issue, educa- without written permission. tors from the Chandra E/PO Office describe four of the classroom-ready activities that DISCLAIMER have been developed. The information contained herein is provided as a service to our members with the understanding In Decoding Starlight: From Pixels to Images, Doug Lombardi describes how students can that National Earth Science Teachers Association (NESTA) makes no warranties, either expressed learn about the creation and interpretation of “false-color” images, a task that is at or implied, concerning the accuracy, complete- the heart of X-ray science. Doug also describes Investigating Supernova Remnants and ness, reliability, or suitability of the information. Nor does NESTA warrant that the use of this why these objects are so critical for the composition of our planet and the universe as information is free of any claims of copyright a whole. The free Chandra ds9 image analysis software can be used with Investigating infringement. In addition, the views expressed in The Earth Scientist are those of the authors and Supernova remnants; download information and instructions are available at http:// advertisers and may not reflect NESTA policy. chandra-ed.harvard.edu/ DESIGN/LAYOUT Patty Schuster, Page Designs Donna Young introduces Chandra’s new classroom activity: Ice Core Records – From Volcanoes to Supernovas. Read about how ice core records can tell us not only about Printed and bound by Scotsman Press, Syracuse, NY on climate records, volcanic eruptions, and solar proton events, but may also help us date recycled paper using soy ink. historical supernova events through the cosmic particles that reach Earth. Donna’s article Pulsating Variable Stars and the Hertzsprung-Russell Diagram focuses on using stellar properties to create a model in order to further understand stellar evolu- tion. Finally, the Chandra E/PO team has included the Stellar Life Cycles color card set to © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 6 The Earth Scientist use as an assessment and/or learning tool for this activity. The cards should be cut into the 24 indi- vidual images to make a classroom set. Additional classroom card sets are available upon request at http://chandra.harvard.edu/edu/request_special.html, and the activity and teacher guide is posted at http://chandra.harvard.edu/edu/formal/stellar_cycle/. But Chandra E/PO isn’t the only thing you’ll find in this special issue. On June 5, 2012, Venus will transit across the face of the Sun – a rare phenomenon that will not occur again until 2117. Elaine Lewis, Sten Odenwald, and Troy Cline provide TES readers with background on this fascinating event’s historical importance and information about how you can witness this event from a live webcast by the University of Hawaii’s Institute for Astronomy. In these pages of TES, you will find background information, activity descriptions, and suggestions for extending these astronomy topics in your classroom. We hope that you will find them engaging and useful, and that you will visit the Chandra E/PO website (http://chandra.harvard.edu/edu/ index.html) for even more ideas! Chandra X-Ray Observatory Education and Public Outreach Office Donna L. Young, Lead Educator Doug Lombardi Guest Writer of this Editor’s Corner Janelle M. Bailey, University of Nevada, Las Vegas TES Editor Tom Ervin Climate and Energy Education Must-Have Resources for Teachers CLEAN Collection Cleanet.org provides: • Reviewed climate and energy learning resources • Teaching tools CIRES Community Forum Iceeonline.org offers: • CIRES climate education support Learn More About Climate LearnMoreAboutClimate.colorado.edu offers: • Climate resources on topics pertinent to the West, including water use, pine beetles and energy • Videos pairing citizens and scientists • Lesson plans, scientist partnerships and resources University of Colorado Boulder © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 7 Decoding Starlight: From Pixels to Images Doug Lombardi Ph.D. Candidate, Educational Psychology, University of Nevada, Las Vegas D ecoding Starlight is a classroom activity that helps students better understand the scientific practices associated with imaging. The activity combines data analysis with image creation and interpretation. Students work through the activity tasks without the aid of automation, thereby facilitating understanding of both how computers normally conduct the analysis and why scientists use computers for imaging. This article first discusses some fundamentals of how scientists and technicians create astronomical images and how imaging is a scientific process. The article then introduces the basics of the activity and how Decoding Starlight can be used in the classroom. Finally, the article concludes by presenting suggested next steps to further deepen student understanding of image analysis and evaluation. Some Imaging Fundamentals Astronomers, geophysicists, and many other scientists use imaging widely in their daily routines. Scientists employ images to achieve greater understanding of our universe, and also to engage students as well as the public in the scientific enterprise. In this way, imaging creates both scientific knowledge and increases scientific literacy. The Decoding Starlight activity uses data collected from NASA’s Chandra X-ray Observatory, a spacecraft and telescope system that has been orbiting Earth since 1999, and helps students learn the fundamental processes of imaging that are common to many scientific disciplines. Representative color The Chandra X-ray Observatory gathers information about high-energy astronomical phenomena. From the data collected by the observatory, scientists and technicians have created literally thou- sands of images that are all available on the Chandra website (http://chandra.harvard.edu). The observatory collects information from X-rays, a type of light invisible to the humans. The question then arises: how are images of X-ray light made, and specifically, how are these images made so that they are scientifically meaningful? © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 8 The Earth Scientist Chandra images are made by using what is commonly called false color, but what the mission education and public outreach office prefers to call representative color. Representative color is commonly used to depict light that our eyes cannot detect, such as radio, infrared, ultraviolet, gamma, and of course, X-rays. Furthermore, representative color is often used to enhance images made from visible light, such as the images made from data collected by the Hubble Space Telescope. Representative colors are selected by scientists and technicians to highlight important details. Additionally, representative colors are chosen as an analog to light that we observe with our eyes. It is often the case in Chandra images that lower-energy (soft) X-rays are colored red, moderate energy X-rays are colored yellow, and higher-energy (hard) X-rays are colored blue. Such a color scheme is representative of the visible light spectrum, where red light has lower photon energy, yellow light has moderate photon energy, and blue light has higher photon energy. Scaling Scientists and technicians also need to define the scaling scheme when they develop representative color images. A fundamental scheme is linear scaling, where different photon energies are equally divided among the different colors. The Chandra X-ray observatory can detect photon energies from about .1 to 10 keV (kiloelectron-volts, where 1 keV equals about 1.6 × 10-16 Joules). Therefore, a linear scheme using three colors (e.g., red, yellow, and blue) would subsequently divide photon energy ranges into three essentially equal parts (~.1 to 3.3 keV is red, 3.3 to 6.7 keV is yellow, and 6.7 to 10 keV is blue). Sometimes scientists and technicians call these equal divisions: bins (think of three laundry hampers, where you would sort white clothes into one hamper, light colors into another, and dark colors into the third). Scientists and technicians often call this scaling/color combination the binning scheme. Imaging as a Scientific Process Data collection and processing are essential facets of astronomical research using both space- and ground-based telescopes. Often the final results of these analyses are images that scientists use to communicate among themselves, as well as with the general public. Many of these images involve observations lasting a few hours up to a few days or more. These observations therefore generate millions of data points from which the images are created. In practice, scientists and technicians use computers to do calculations, and to change measured and calculated numbers into images. A tremendous amount of scientific understanding and effort goes into creating these computer- generated images. As Comins (2001) states, “these images create an impression of the glamour of science in the public mind that is not entirely realistic…the process of transforming most telescope data into accurate and meaningful images is long, involved, unglamorous, and exacting…make a mistake in one of dozens of parameters or steps in the analysis and you will get inaccurate images” (p. 76). However, imaging is not just an essential skill for astronomers, but something which is prac- ticed by many scientists (e.g., meteorologists’ use of infrared images of clouds; neurologists’ use of magnetic resonance images). The process of scientific imaging is an excellent example of the science and engineering practices recommended for inclusion into the Next Generation Science Standards (National Research Council, 2011), including the use of mathematics, information and computer technology, and computational thinking. Therefore, it is important that when our students view these images, they understand the fundamental processes scientists are using to create them (e.g., representative color and scaling), as well as the meanings scientists are trying to convey through these images. © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 9 Removing the Veil Decoding Starlight: From Pixels to Images is an activity created to take students through the steps of data and image processing with actual data from the Chandra X-ray Observatory. The data are from observations made of Cassiopeia A (or Cas A for short), a supernova remnant of what once was a massive star (also known as a Type II supernova). Supernova remnants can emit an abundance of X-rays and Cas A was Chandra’s extended source calibration image (e.g., one of the first images observed by the observatory to verify that both spacecraft and instrumentation were functioning properly; see Figure 1). Over time, Chandra has made several detailed observations of Cas A that have greatly expanded our understanding of supernovas and stellar nucleosynthesis, which is the generation and distribution of elements from carbon to pluto- nium. Cas A is the youngest supernova remnant in the Milky way and you can learn more about this remnant and nucleosynthesis at the Chandra website (http://chandra.harvard.edu/photo/2011/casa). Decoding Starlight is easily scaled to various grade levels and the author has personally used the activity with 5th grade students, under- graduates, and every grade in between. The underlying purpose of this activity is to engage students in the fundamentals of imaging, including basic data analysis, assignment of representative color and scaling schemes, generation of an image by hand, and creating an analog artist’s representation Figure 1.Cassiopeia A (Cas A) to help communicate their understanding. For classroom manageability purposes, the data for is a 325-year-old remnant produced by the explosive death Decoding Starlight have undergone some pre-analysis by Chandra scientists, but the activity retains of a massive star located about the basic principles of data analysis. You can download a description of the Decoding Starlight activity 11,000 light years from Earth. and the necessary materials for classroom use at http://chandra.harvard.edu/edu/formal/imaging/ This image was created using index.html. The main features of the activity are highlighted below. representative color. Credit: NASA/CXC/MIT/UMass Amherst/M.D.Stage et al. The Scenario The Decoding Starlight activity has students assume the role of scientists who have just discovered a new supernova remnant. The students are told that they are expected to present this discovery to a NASA official very soon, but unfortunately, their computer has crashed. In order to create an image for the presentation, the students need to reanalyze some of the data and create an image using paper and pencil. The Tasks Students need to complete three major tasks in Decoding Starlight: a. recalculate some values that have been lost in the computer crash, b. determine the binning scheme to be used to color the image, and c. prepare the image and the associated presentation. The activity is flexible in many ways by supporting a variety of instructional modes and grade levels. For example, the teacher may specify a certain method for recalculating missing values, such as using a simple arithmetic average among numbers. However, advanced students can use more robust calculations (e.g., areal or running average techniques). Furthermore, the activity has both a middle and high school version. The middle school version of Decoding Starlight has much fewer values that require recalculation. © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 10 The Earth Scientist Examples of student work on the Decoding Starlight is similarly flexible in allowing a variety of binning schemes. For example, students Decoding Starlight: From Pixels can pick a linear, logarithmic, or squared scaling method. If students use linear scaling (equal to Images activity. range of photon counts for each bin; which may be the preferred scaling technique for lower grade (left to right) levels), the image looks quite different than when they use logarithmic scaling (more bins associ- Figure 2.This example represents a linear scaling and ated with lower photon count ranges) or squared scaling (more bins associated with higher photon complementary color scheme. count ranges). Students can also specify different color schemes, such as using complementary Figure 3. This example color transitions to sharply delineate different bin ranges, or a gradual color transitions to provide represents a quasi-logarithmic smoothness to the different bin ranges. With lower grade levels, teachers may wish to have pre- scaling and complementary color assigned representative color and binning schemes; however if you pre-assign schemes to students, scheme. I recommend having students select from more than one because this will allow for a richer class Figure 4. This example represents a quasi-exponential discussion when sharing results. Figures 2, 3 and 4 are examples of students’ work with various scaling and gradual color representative color and binning schemes. scheme. Planning to Use Decoding Starlight Be sure to read the teacher’s guide section of Decoding Starlight (http://chandra.harvard.edu/edu/ formal/imaging/index.html) to gain insights about how to prepare and use the activity in your classroom. For example, you may wish to introduce your students to the basic components that are commonly found in supernova remnants prior to conducting the activity. In a Type II supernova remnant that results from a massive stellar explosion, common components that can often be imaged are the n stellar remnant (a neutron star or black hole), n slow inner shock wave, and n fast outer shock wave. Students can resolve each of these components in the image of Cas A that they create; however, because they are doing this by hand, the resolution will be far less detailed than in the Chandra images. If you introduce your students to supernovas before conducting the activity, the Chandra website contains many images and explanations of supernova remnants other than Cas A (http:// chandra.harvard.edu/photo/category/snr.html). Be sure to use Type II supernova remnants, which are from explosions of massive stars. Type Ia supernova remnants have some different features because they result from explosions of stars that are about the same mass as our Sun and © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 11 are accreting material from a companion star. Alternatively, you may wish to have the students complete Decoding Starlight prior to any discussion of supernovas. In this way, the About the Author activity and the drawings created by your students would be a platform for engagement Doug Lombardi is a doctoral and introduction. candidate in Educational Psychology at the University of Nevada, Las Vegas. Analyzing Data and Generating Images with Computers His research is on climate change Decoding Starlight provides an introduction for students’ use of the SAOImage ds9 software. education and the role of critical This software was developed by the Harvard-Smithsonian Center for Astrophysics (CfA) evaluation in reappraising plausibility to first, acquire Chandra data, and then, to form and analyze computer-generated images. judgments and conceptual change. He The software and data are free and available for student use at the Chandra Education has appreciable experience working Data Analysis Software and Activities web site (http://chandra-ed.harvard.edu). The ds9 in NASA education enterprises and software can be run on either on the Windows or Mac operating systems. Although not has been a teaching resource agent required for successful use of the software, conducting Decoding Starlight in your classroom for the agency’s Chandra X-ray prior to doing computer-assisted analysis can deepen your students understanding about Observatory since 2001. Doug is also imaging processes and increase their chances for conducting meaningful investigations. a project facilitator at the Regional Furthermore, the activity provides an opportunity for students to learn about the funda- Professional Development Program, mentals of a scientific practice that spans several disciplines. serving as a science education specialist and the program’s internal References evaluator. He is a licensed physics and Comins, N. F. (2001). Heavenly errors: Misconceptions about the real nature of the universe. New York: mathematics teacher, with 12 years Columbia University Press. experience in a variety of educational National Research Council. (2011). A framework for K-12 science education: Practices, crosscutting concepts, settings. Doug can be reached at and core ideas. Committee on a Conceptual Framework for New K-12 Science Education

. Standards Board on Science Education, Division of Behavioral and Social Sciences and Education. Washington, D. C.: The National Academies Press. Welcomes K-12 Teachers with programs tailored to your needs! • Geophysical Information for Teachers Workshops • Bright Stars • AGU Speaker at National NSTA Conference • AGU Membership includes weekly EOS magazine, with science updates and opportunities www.agu.org/education © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 12 The Earth Scientist Ice Core Records – From Volcanoes To Supernovas Figure 1. Illustration of the Cas A supernova remnant in the Ice Core Record. Donna L Young Jean-Pierre Normand, artist, Montreal, Canada Abstract An ice core – known as the GISP2 H-Core – was collected in June, 1992 adjacent to the GISP2 (Greenland Ice Sheet Project Two) summit drill site. The project scientists, Gisela A.M. Dreschhoff and Edward J. Zeller, were interested in dating solar proton events with volcanic eruptions. The GISP2-H 122-meter firn and ice core is a record of 415 years of liquid electrical conductivity (LEC) and nitrate concentrations – spanning the years from 1992 at the surface through 1577 at the bottom. The liquid electrical conductivity (LEC) sequence contains signals from a number of known volcanic eruptions that provide a dating system at specific locations along the core. The terrestrial and solar background nitrate records show seasonal and annual variations – as well as unique events. Several major nitrate anomalies within the record do not correspond to any known terrestrial or solar events, and there is evidence that some of the nitrate anomalies within the GISP2 Figure 2. 191-year Longleaf Pine tree ring record from the Hope H-Core could be a record of supernova events. Mills, North Carolina © 2012 Photo courtesy of Dr. Henri D. Grissino- The Chandra Education and Public Outreach Office, in cooperation with the GISP2 Mayer, University of Tennessee H-Core project scientist Dr. Gisela A. M. Dreschhoff, has developed a classroom activity for middle school and high school students, utilizing absolute and relative dating techniques to examine several lines of evidence in the high resolution GISP2 H-Core data – discriminating among nearby and mid-latitude volcanic activity, solar proton events, and possible supernova events. Ice Core Records – From Volcanoes to Supernovas Constructing a reliable record of the Earth’s history only began in the 1880’s. To reconstruct conditions and events further back in time, scientists use proxies – preserved physical characteristics of the past such as tree rings, lake and ocean sediments and © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 13 ice cores. The deposition or growth rates of proxy materials are influenced by the Figures 3a and 3b. climatic conditions during the time they were deposited or grew. Ice cores can (a) Top 53 meters of the GISP2 ice core firn provide an annual record of temperature, precipitation, atmospheric composi- (b) Annual layers of the GISP2 tion, volcanic eruptions and solar activity. Snow contains the compounds that ice core at a depth of 1837 are in the air at the time – compounds ranging from sulfates, nitrates and other meters ions, to dust, radioactive fallout, and trace metals. In the Polar Regions, where Photos courtesy of the U.S. National Ice Core Laboratory, Denver, CO temperatures above freezing are extremely rare, gravitational deposition (dry or snowfall) of the materials in the atmosphere fall on top of the previous year without melting. The upper unconsolidated layers of snow are called firn. The upper layers of ice below the firn correspond to a single year or sometimes just a single season. Deeper into the ice the layers become more compressed and annual layers become indistinguishable. Any materials that were in the snow, such as dust, ash, bubbles of atmospheric gas and radioactive substances, remain in the ice. This information is used to determine temperature, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, and solar variability. The Greenland GISP2 H-Core Figure 4. Gisela Dreschhoff at Grinnell Lake in Glacier National Research Project Park 2009 Donna L Young, photographer The original GISP2 H-Core data set consists of a total of 7,776 individual analyses. The upper 12 meters of firn were analyzed on-site in Greenland and the remaining core was sent to the National Ice Core Laboratory in Denver, Colorado. At the lab, the core was sliced into 1.5 cm thick samples, and each sample was inserted into a glass vial which was sealed and stored at -24oC. Approximately twenty vials were removed at a time from storage and allowed to melt at room temperature for one hour. The liquid samples were removed from the vials with a syringe and injected into a UV absorption cell (UV spectrophotometer) to determine the nitrate values in absorption units. After the nitrate values were obtained from the UV spectrophotometer, the samples were inserted directly into a micro-conductivity cell to measure the conductivity in micro Figure 5. The first 800 samples of the GISP2 H-core showing Siemens per centimeter (mS/cm). This ultrahigh resolution sampling technique resulted in a time the conductivity (red) and nitrate resolution of one week near the surface and one month at depth. At a later time 3.6 meters of core (green) records were added, taking the time series back to the year 1561 – with a total of 8,002 samples analyzed. Courtesy of Dr. Gisela Dreschhoff The Liquid Electrical Conductivity (LEC) Record and Volcanoes The liquid electrical conductivity measurements (LEC) measure the change in acidity along the length of the core. Numerous anomalies occur in the liquid electrical conductivity (LEC) records. The LEC sequence contains signals from a number of © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 14 The Earth Scientist Figure 6 (left). Aerial photo of the known volcanic eruptions and provides a dating system at specific locations along the core. An onset of the Grimsvotn volcano especially distinctive signal in both records marks volcanic eruptions in Iceland. Nearby Icelandic eruption, Iceland, 2011 volcanic eruptions release most of their products into the upper troposphere, and deposition onto Olafur Sigurjonsson, photographer the Greenland ice sheet happens within a week. Because the Icelandic eruptions occur geographi- Figure 7 (right). Solar prominence cally close to the GISP2 H-core drill site, they produce large and distinctive conductivity signals eruption on March 19, 2011, SOHO spacecraft accompanied by very sharp reductions in nitrate concentrations. The reason is that the hydroxyl Courtesy of NASA ions (OH-) are preferentially used in the oxidation of volcanic SO2 and therefore are unavailable for the production of nitrates. The Icelandic volcano signature – opposed dual anomalies of high conductivity and low nitrates – provide time markers to use absolute dating techniques for events recorded within the Greenland ice core. The Nitrate Record and Solar Proton Events Charged particles from solar activity follow the Earth’s magnetic field lines and enter the atmo- sphere above the Polar Regions. The particles ionize nitrogen and oxygen, generating oxides of nitrogen with nitrates (NO3-) as the end product. Changes in solar activity lead to changes in the amount of nitrates in the atmosphere; and therefore in the amount of nitrates that get deposited in Figure 8 (left). The 400 year the Polar Regions. Solar activity and the resulting solar proton events leave a continuous record of sunspot record from 1600 – nitrate deposits within the polar ice; therefore, a measurement of the nitrate record is a reflection of 2000 with the more unreliable observations plotted in red solar activity. Prolonged and sustained solar observations are fairly recent – since the early 1600’s – Courtesy of Hoyt & Schatten, Solar Physics, 1998 and ice core data provides evidence of solar behavior that pre-dates telescopes and satellites. Figure 9 (right). A 37.5 year section of the GISP2 H-core with nitrate anomalies that correlate to the Tycho and Kepler supernova events Courtesy of Dr. Gisela Dreschhoff © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 15 The main feature in the 415-year nitrate concentration record is the prominent yearly cycle – with the spring/summer values higher than the fall/winter values. Volcanic episodes and other terres- trial processes add nitrates to the atmosphere that are deposited and recorded in the ice sheets. The annual solar nitrate record also includes concentration variations produced by unique solar activity. One example is the solar proton nitrate concentration fluctuations that remain consistent through the Dalton (1833 – 1798) and Maunder (1715-1645) Minima – periods of unusually low solar activity. A major nitrate anomaly in 1859 is related to a solar flare that was optically observed by Richard Carrington in England. A few large nitrate anomalies accompanied by comparable and sharply defined anomalies in the conductivity occur simultaneously and are not connected to any known volcanic eruptions or unique solar proton events. These peaks are several standard deviations above the mean. It is likely that these anomalies result from the primary production of nitrate (NO3-) in the atmosphere – therefore there has to be an enhanced supply of nitrate in the stratosphere. In the GSIP2-H core segment shown, there are major dual nitrate and conductivity anomalies at the times of the Tycho and Kepler supernovas. There are no known terrestrial or solar events that could have produced nitrate spikes of this magnitude, and they occur with the correct time separation of 32 years and one year after Tycho and Kepler observed and recorded these two events. Supernova events produce high energy photons (X-rays and gamma rays) that enter the stratosphere and ionize atmospheric nitrogen – producing excess nitrates that are then gravitationally deposited in the Polar Regions with up to a one-year time delay. Supporting evidence from two ice cores drilled in Antarctica contains nitrate anomalies at the same time equivalent locations. The GISP2 H-Core Classroom Materials At the 2005 American Association of Physics Teachers (AAPT) winter meeting in Albuquerque, New Mexico, the author attended an invited talk by Dr. Gisela Dreschhoff. The title of her talk was irresistible – Evidence for a Stratigraphic record of Supernovae in Polar Ice. The description mentioned the possibility that the Cassiopeia A (Cas A) supernova event was part of the ice core record. After corresponding with Gisela, reading the research and studying the high resolution ice core data, it was decided the materials would provide the basis for an interesting interdisciplinary classroom investigation. The Ice Core Record – From Volcanoes to Supernovas is the end result and is available at http://chandra.si.edu/edu/formal/ icecore/ In this investigation, students examine the seasonal/annual nitrate record and use information from known volcanic eruptions to date the unique signature of the Icelandic volcanoes. Data is also provided for known volcanic eruptions from other Figure 10. Kepler’s Supernova latitudes which can be used throughout the activity to date major conductivity spikes to further Remnant NASA/CXC/NCSU/S.Reynolds et al. refine the time locations. Solar proton data, including the Carrington superflare and the Dalton and Maunder Minima are used to date both solar activity and unique solar events. Using seasonal nitrate cycles and the volcanic eruptions that have been labeled on the ice core strip, students search for unlabeled nitrate anomalies that correlate to the Tycho and Kepler supernova events of 1572 and 1604 respectively. The final task for students is to search for evidence of an anomaly that could be correlated to the Cassiopeia A supernova and determine the date of the event. After reading the possible evidence for different dates of the Cas A supernova, students can decide for themselves which date they support. Cassiopeia A has been observed by the Chandra X-ray telescope multiple times, and each observation increases our knowledge of the remnant © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 16 The Earth Scientist and neutron core. Knowing the exact date of the event would increase our understanding of the processes that produced the present structure of Cas A. However, even after decades of multi- wavelength observations of Cassiopeia A, the exact date of the collapse of the progenitor star that produced the remnant remains a mystery! Using Ice Core Records – From Volcanoes to Supernovas in the Classroom This student investigation is an application of absolute and relative dating techniques – a skill taught within multiple disciplines – and includes concepts relating to cryology, chemistry, meteo- rology and astronomy. Educators can use the investigation as a springboard to the associated sciences – but that is not the intended focus of the materials. The GISP2 H-core contains suspected supernova events, and there are other research projects that support the correlation of nitrates with supernovas; however, within the scientific community there are those who disagree. Controversial science is great science; often, serendipitous discoveries that cross disciplinary boundaries produce years of additional research, analysis, investigation and debate before a final consensus is reached. Sometimes there is no one definitive answer unless other supporting evidence is found. This inves- tigation provides a more realistic view of how science Figure 11. Artist’s conception of works. The GISP2 H-core also contains nitrate anoma- a supernova event as seen from lies that are as yet unidentified and are not correlated the Earth’s northern Polar Region. Jean-Pierre Normand, artist, Montreal, Canada with any known terrestrial or extra-terrestrial event – providing students with the opportunity for research projects. The power of Ice Core Records – From Volcanoes to Supernovas is that it does not provide all the answers; it is an open-ended inquiry into possibilities. There are interesting and rich historical connec- tions during the timeframe represented in the core – including the first ice core data from Greenland, Icelandic volcanism, the historical sunspot record, the lives of Tycho Brahe and Johannes Kepler, John Flamsteed the First Royal Astronomer, and King Charles II of Great Britain. The detonation of the RDS-220 hydrogen bomb and the Tunguska Event also occurred within the timeframe of the GISP2 H-Core. The core is embedded within a historical context of changing world views and paradigm shifts. The introductory sections provide a historical context and perspective of the individuals and/or locations related to the investigation. The associated histories help illu- minate science as an extension of the prevailing culture of the times. A major focus of the Chandra X-Ray mission is to study the cycles of matter and energy that drive the evolution of the universe – and supernovas are funda- mental to that process. Supernova events create elements through nucleosynthesis which travel into the interstellar medium and become incorporated into the next generation of stars and planetary systems. The high energy X-rays and gamma rays generated by supernovas several light years away impact the Earth – and leave their signatures within the ice sheets of the Polar Regions. © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 17 Materials and Supporting Resources Ice Core Records – From Volcanoes to Supernovas: An activity that applies absolute and relative About the Author dating techniques to high resolution ice core data to identify Icelandic and mid-latitude Donna L. Young, Lead Educator, volcanic eruptions and solar proton events, and correlate unidentified anomalies within the Chandra Education & Public core with supernova events. The investigation includes extensive background information, Outreach Office student ice core worksheets and labeled ice cores in HTML and PDF. http://chandra. si.edu/edu/formal/icecore/ Donna Young develops Cassiopeia A (Cas A)—The Death of a Star: A timeline that describes the Cas A supernova event. educational materials for the http://chandra.harvard.edu/edu/formal/casa_timeline/ Chandra X-ray mission, and is Stellar Evolution: A Journey with Chandra: A poster which displays the cycles of the evolutionary a staff member at the American stages of stars of different masses. http://chandra.harvard.edu/edu/prod_descriptions. Association of Variable Star html Observers in Cambridge, MA. Poster Request Form: http://chandra.harvard.edu/edu/request.html She is the National Science Podcasts: Supernovas and Supernova Remnants: A list of podcasts that highlight Chandra Olympiad astronomy event observations of supernovas. http://chandra.harvard.edu/resources/podcasts/by_ supervisor. She presents category.html?catid=4 Chandra and AAVSO The Story of Stellar Evolution: A complete intro­duction that describes the stages of stellar evolution educational materials to formal of all stars. http://chandra.harvard.edu/edu/formal/stellar_ev/story/ and informal educators and Investigating Supernova Remnants: An activity that uses Chandra data and ds9 image analysis Science Olympiad coaches and software to investigate supernova remnants to determine if they are Type II core collapse or teams at national workshops Type Ia thermonuclear events. http://chandra.harvard.edu/edu/formal/snr/ and conferences. She can be reached at

. Twenty Five Years Ago in TES HELP WANTED! T wenty Five years ago, TES was in its fourth year of publi- cation. In 1987, the cover of Volume 4, issue 1 featured a map of the planet Jupiter detailing the belts and zones as deter- NESTA needs you to help us run our events at the NSTA Conference in Indianapolis. We need volunteers to help with our Share-a-thons, Rock mined by NASA. To accompany the cover, inside the TES there Raffle, and at our Exhibit Hall booth. If you feel was a seven page article summaraizing the newest informa- that you can help, contact Joe Monaco, NESTA Volunteer Coordinator:

tion about Jupiter and the other outer planets. The issue also featured an eight page article detailing the history of the Why should I open and read the Scientific Approach. There was NESTA ENews emails? an article explaining how the NESTA’s monthly ENews provides brief summa- Accu-Weather© database could ries of stories and projects that have a direct be used in the classroom. The link to the Earth Sciences and or the teaching article marvelled at the fact of Earth Sciences. Many of these short articles provide links to more information or complete that the database featured websites that those interested can follow. The hourly weather readings. ENews also contains information regarding An article discussed how teacher opportunities for research, professional popping popcorn could development, and even grants. The reader will be used to teach conduction, also find a calendar with items that have time convection and radiation, after which the class could eat the critical information or may be occurring later that month or the next month. The ENews will also be popcorn. And finally, an update on Mount St. Helens was adding state related links each month. The goal presented, reporting the seismic activity in the 7 years since is to provide links to two states’ Earth Science its 1980 eruption as well as using “dome growth” to predict sites each month. For example, in the June 2011 eruptions. issue we focused on Earth Science resources in Alabama and Colorado. © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 18 The Earth Scientist Transit of Venus June 5, 2012 Elaine Lewis, Sun Earth Day; Dr. Sten Odenwald, SpaceMath@NASA and Troy Cline, E/PO Magnetospheric Multiscale Mission (MMS) This is the transit of Venus observed by the 1-meter Swedish Vacuum Telescope in La Palma on June 8, 2004 at the wavelength of H-alpha. Credit: Institute of Solar Physics, Royal Swedish Academy of Sciences. O n June 5, 2012, you should see the planet Venus as it moves across the face of the early morning sun. This astronomical oddity has played a very important role over the last few centuries in giving scientists a way to understand the size of the solar system. It is fair to say though that Galileo Galilee with his telescope, in 1610, was the first human to actu- ally see Venus as more than just a bright point of light in the sky. Johannes Kepler, meanwhile, was shaking up the world with his meticulous use of astronomical data assembled by Tycho Brahe. He predicted that Venus would pass in front of the Sun on December 6, 1631, but unfortunately the transit was not visible from Europe at all. The first recorded sighting of this transit was by British cleric, Jeremiah Horrocks, and his friend William Crabtree, on December 4, 1639—only because Horrocks had mathematically predicted it, using better data than Kepler had. Scientists calculated they could use the transit to figure out the size of the solar system! How do we know that the actual distance from Sun to Earth is 93 million miles and not, say, 153 million or 23 million? In 1663, mathematician Rev. James Gregory suggested that a more accurate calculation of the Earth-Sun distance could be made during the transit of Venus. It turned out to be harder than anticipated, but during subsequent transits, the focus on Venus led to an even more exciting discovery. During the transit of June 5, 1761, observed by 176 scientists from all over the world, Russian astronomer Mikhail Lomonosov (1711-1765) discovered a very strange thing. Instead of the very black disk of Venus sliding into the Sun’s bright edge, it actually grew a brief, beautiful halo of light all around its dark edge. This is exactly what you would expect to see if Venus had an atmosphere! In 1769, many international expeditions planned observations. The most famous expedition was led by Capt. James Cook, who set up an observation post in Tahiti using his ship, the Endeavour. The expedition astronomers, with help from a detachment of Royal Marines, set up an observatory on a high point of ground above the bay (still known as “Point Venus”) and made many transit measurements. They later discovered New Zealand, got stuck on the Great Barrier Reef for several weeks, and explored many of the then unknown coasts of Australia. Cook and his crew completed © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 19 their trip around the Earth and reached England safely and in triumph. The expedition established Cook’s fame as a mariner and explorer. The next transit, on December 6, 1882, made the front pages of every newspaper, worldwide. Thousands of photographs were taken with improved calibrations. Only a few astronomers were trusted to carry out the complex calculations from the resulting data. In 1896, Simon Newcomb’s value, a distance from Earth to Sun of 92,702,000 plus or minus 53,700 miles, was adopted by the international scientific community. Today most textbooks report the Astronomical Unit (or AU) as “93 million miles.” On June 5, 2012 Venus will transit across the face of the sun, an event which will not be seen again until 2117. The Sun Earth Day Team and NASA EDGE have joined forces to celebrate the Transit of Venus! On June 5, 2012, we will air a live ‘remote’ webcast from Mauna Kea, Hawaii, through our partnership with the University of Hawaii Institute for Astronomy. The event will not be visible from the continental U.S. in its entirety. With little chance of cloud cover, the mountainside Visitors Station site near the observatories in Hilo, Hawaii should, for the entire transit, give a wonderful view to a worldwide audience, enabling us to bring to you, real-time images, in various wavelengths of light, for the duration of the event. This webcast will also emphasize the history and importance of Hawaiian astronomy and its connections to NASA space science. It will use the backdrop of Mauna Kea, combined with the world class University of Hawaii (UH), NASA scientists and Hawaiian cultural leaders to weave multigenerational stories combining ancient ways of knowing with modern scientific discoveries. The University of Hawaii Institute for Astronomy is an astronomical research facility and host to the Mauna Kea Observatory, one of the most important observational astronomy sites in the world. Mauna Kea is a unique astronomical research facility, emphasizing respect for Hawaiian cultural beliefs, as well as the protection of environmentally sensitive habitats. The exceptional stability of the atmosphere above Mauna Kea permits more detailed studies than are possible elsewhere, while its distance from city lights and a strong island-wide lighting ordinance ensure an extremely dark sky, allowing observation of the faintest galaxies that lie at the very edge of the observable Universe. Follow us on http://sunearthday.nasa.gov for information about viewing the webcast and the continual streaming (6 hours and 40 minutes) of the Transit of Venus. About the Authors Elaine Lewis is a Technical Specialist (Educator) and has extensive experience in teaching and curriculum development. She has lead the SED team for 6 years and formal education lead for 11 years. Together with spacecraft mission personnel, she made near real-time NASA space weather data accessible for inquiry- based learning. Elaine Lewis can be contacted at

Dr. Sten Odenwald is an astronomer at the NASA Goddard Spaceflight Center. He is an active science popularizer and book author, and participates in many NASA programs in space science and math education. He was recently awarded a 3-year NASA education grant to continue his Space Math @ NASA project which develops K-12 math problems based on NASA mission data and press releases. Dr. Odenwald can be contacted at

Troy Cline is the E/PO Lead for the Magnetospheric Multiscale Mission (MMS). He is responsible for mission level public outreach activities and coordination of overall EPO efforts. He also serves as the Educational Technology Integration Specialist, providing ongoing educational technology support and leadership in the development and distribution of educational programs and materials. Troy Cline can be contacted at

© 2012 National Earth Science Teachers Association. All Rights Reserved. Page 20 The Earth Scientist Pulsating Variable Stars and The Hertzsprung- Russell Diagram Donna Young Cygnus X-1 is a 15 solar mass black hole in orbit with a massive main sequence blue companion star approximately 6070 light years from Earth. Cygnus X-1 is a stellar-mass black hole - the result of the core collapse of a massive star. Credit: Artist Illustration: NASA/CXC/M. Weiss Abstract Ejnar Hertzsprung, working with Henry Norris Russell between 1911 and 1913, devel- oped the Hertzsprung - Russell diagram (H-R diagram) – an important astronomical tool that represents a major step towards understanding how stars evolve over time. Stellar evolution can not be studied by observing individual stars as most changes occur over millions and billions of years. Astrophysicists observe numerous stars at various stages in their evolutionary history to determine their changing properties and probable evolu- tionary tracks across the H-R diagram. The H-R diagram is a scatter graph of stars – a plot of stellar absolute magnitude or luminosity versus temperature or stellar classification. Stages of stellar evolution occupy specific regions on the H-R diagram and exhibit similar Figure 1. Supernova in star properties. One class of stars – the pulsating variables which include Cepheids, RR Lyraes, forming region in the Small Semiregulars and Miras – occupy regions of instability on the H-R diagram and represent Magellanic Cloud Galaxy Image courtesy of Chandra transitional periods between stages of evolution. The American Association of Variable Star Observers (AAVSO) and the Chandra X-Ray mission have collaborated with variable star observations and educational materials in their mutual quest to understand stellar processes and evolution. The H-R Diagram student activity is an example of how evidence is used to construct a model to explain complex concepts – in this case the evolution of stars which is fundamental to understanding the origin and evolution of the universe. © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 21 The Hertzsprung-Russell (H-R) Diagram The Hertzsprung-Russell (H-R) diagram is an analog to the periodic table of the elements. It was discovered that when the absolute magnitude (MV) – intrinsic brightness – of stars is plotted against their temperature (stellar classification) the stars are not randomly distributed on the graph but are mostly restricted to a few well-defined regions. The stars within the same regions share a common set of characteris- tics, just like the groups, periods, and blocks of elements in the periodic table. Unlike the periodic table, as the physical characteristics of a star change over its evolutionary history, its position on the H-R diagram changes also – so the H-R diagram can also be thought of as a graphical plot of stellar evolution. From the location of a star on the diagram, its luminosity, spectral type, color, temperature, mass, chemical composition, age, and evolutionary history are known. Figure 2. Basic Hertzsprung- Russell diagram Most stars are classified by temperature (spectral type) from hottest to coolest as follows: O B A F G Diagram courtesy of NASA K M. These categories are further subdivided into subclasses from hottest (0) to coolest (9). The hottest B stars are B0 and the coolest are B9, followed by spectral type A0. Each major spectral classification is characterized by its own unique spectra. Though O B A F G K and M are the stellar classifications commonly shown on H-R diagrams, a number of new and extended spectral classes have been desig- nated. These include Wolf-Rayet stars (W), cool dwarfs (L), brown dwarfs (T), carbon stars (C), and stars with zirconium oxide lines that are between M and C stars (S). The carbon stars (C) include stars that were Figure 3 (above). Some examples originally classified as R and N stars. Class of Harvard classification stellar D (degenerate) is the modern classification spectra Image courtesy of NASA for white dwarfs. The major classifications have subclasses – Class D is divided into 7 Figure 4 (left). The luminosity classifications on the H-R different subtypes of white dwarfs based diagram upon variations in the composition of their Diagram courtesy of Wikimedia Commons atmospheres, e.g. DQ white dwarfs have a carbon-rich atmosphere. Spectral lines can show different charac- teristics within the same spectral type or temperature (T), and so a second type of classification system for stars was devised using luminosity. The differences in spec- tral lines among stars having the same spectral type are a function of the radius of the star, which results in different © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 22 The Earth Scientist luminosities. Luminosity (L) is related to the absolute magnitude (MV) of a star, and is the total amount of energy radiated per second (luminosity is proportional to T4). Two stars with similar effective temperatures but greatly different luminosities must differ in size. They belong to different luminosity classes within that spectral type, as determined from their spectra. Stellar luminosities range from one million times more luminous than the Sun, to one ten-thousandth of the luminosity of the Sun. The basic luminosity categories from most to least luminous are I and II, supergiants and bright giants respectively, III giants, IV subgiants, V main sequence stars, VI subdwarfs and VII white dwarfs. Starting at the upper left-hand corner and curving down to the lower right-hand corner is a band called the main sequence. ~90% of all stars lie within the main sequence. These stars run from the hot and bright O and B stars at the top left-hand corner to the cool, dim K and M stars at the lower right-hand corner. Main sequence stars have a fairly steady rate of hydrogen fusion ongoing in their cores. In main sequence stars, the radiation pressure pushing outward from the fusion process balanced by the inward pull of gravitational forces maintains a state of dynamic equilibrium. When hydrogen in the core is depleted and radiation pressure decreases, the two forces become unbalanced and the star “moves off the main sequence” and begins a series of evolutionary stages – the final end product(s) depending upon the initial mass of the star. The giant and supergiant branches of the H-R diagram are occu- Figure 5. H-R diagram of pied by stars that have transitioned from the main sequence and are fusing heavier atomic nuclei. luminosity vs temperature As most stars transition from the main sequence to the giant and supergiant branches, they exhibit Image Courtesy of the European Southern Observatory types of variability that are also confined to specific locations on the diagram. Pulsating Variable Stars and Light Curves As many stars transition from one stage to another on the H-R diagram they vary in brightness. The brightness that a star appears to have (apparent magnitude) from our perspective here on Earth Figure 6. A variable star depends upon its distance from Earth and its actual intrinsic brightness, or absolute magnitude classification system (MV). The behavior of stars that vary in magnitude (brightness) can be studied by measuring their Diagram (revised) courtesy of the Australian changes in brightness over time and plotting the changes on a graph called a light curve. Light Telescope E/PO curves are usually plots of apparent magnitude over time. Historically the time scale has been the Julian Day (JD), a counting system starting with January 1, 4713 BC – Julian Day number 1. Measuring and recording the changes in magnitude and plotting the resulting light curves allow astron- omers to determine the period of variation. The period is the amount of time it takes for the star to go through one complete cycle from maximum magnitude through minimum magnitude and back to maximum magnitude. The 2011 General Catalog of Variable Stars (GCVS) classifies 43,675 Milky Way Galaxy stars into several different categories and subcategories of variability. The intrinsic, pulsating variable stars located in the instability regions of the H-R diagram vary in © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 23 brightness due to physical changes within the interior of the star. The pulsations are due to the periodic expansion and contraction of the surface layers of the stars. The change in size is observed as a change in apparent magnitude. Stars pulsate because they are not in hydrostatic equilibrium: the force of gravity acting on the outer mass of the star is not balanced by the interior radiation pressure directed outwards from the interior. If a star expands as a result of increased radiation pressure, the material density and pressure decrease until hydrostatic equilibrium is reached and then overshot, owing to the momentum of the expansion. At this point the star is transparent and photons can escape. Then gravity dominates, and the star begins to contract. The momentum of the infalling material carries the contraction beyond the equilibrium point. The star becomes opaque and photons are trapped and the star becomes dimmer. The pressure again becomes too high, and the cycle starts over again. The system acts as an oscillator. With loose atmospheric layers of gases, the oscillations get out of phase with one another and set the stage for chaotic motions. Energy is dissipated during such pulsations (analogous Figure 7. Pulsating mira variable to losses caused by frictional forces), and eventually this loss of energy should result in a damping star (Chi Cyg) Image courtesy of SAO/NASA or lessening of the pulsations. The prevalence and regularity of pulsating stars imply that the dissi- pated energy is replenished in some way. The dynamics of pulsating variable stars is complicated and not well understood. Figure 8. Cepheid variable star The different types of pulsating variables are distinguished by their periods of pulsation and the light curve (Delta Cep) shapes of their light curves. These in turn are a function of their mass and evolutionary stage. Image courtesy of AAVSO, Cambridge, MA Cepheids, RR Lyraes, and Long Period Variables (LPVs) – Miras and Semiregulars – are pulsating vari- able stars and occupy regions on the H-R diagram called instability strips. Cepheid variable stars expand and contract in a repeating cycle of size changes. The change in size can be observed as a change in apparent brightness (apparent magnitude.) Cepheids have a repeating cycle of change that is periodic - as regular as the beating of a heart, with a period of 1 to 70 days with an amplitude variation of 0.1 to Figure 9. RR Lyrae variable star light curve 2.0 magnitudes. These massive stars (~8 Image courtesy of AAVSO, Cambridge, MA solar masses) have a high luminosity and are spectral class F at maximum, and G to K at minimum. Cepheids occupy an elon- gated horizontal instability strip on the H-R diagram as massive stars transition from the main sequence to the giant and supergiant branches. RR Lyrae variables are older pulsating white giants with low metallicity. They are common in globular clusters – dense groups of old stars in the halos of galaxies. © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 24 The Earth Scientist Like Cepheids, their pulsations are periodic. RR Lyraes have ~0.5 solar mass and have a short pulsa- tion period of 0.05 to 1.2 days and amplitude variations of 0.3 to 2 magnitudes. RR Lyrae stars are usually spectral class A. RR Lyrae stars occupy a small instability strip near the intersection of the main sequence and the horizontal giant branch (HB). The HB stars have left the red giant branch and are characterized by helium fusion in their cores surrounded by a shell of hydrogen fusion. Cepheids and RR Lyrae variables are periodic and there is a relationship between their period and luminosity – the period-luminosity relationship. The period is calculated from the light curve and the associated luminosity is determined. The luminosity is then either used directly or converted to Figure 10 (left). Mira variable star light curve (Omicron Ceti) absolute magnitude and used with the apparent magnitude in the distance modulus equation to Image courtesy of AAVSO, Cambridge, MA calculate cosmological distances within the Milky Way Galaxy and to other galaxies. Figure 11 (right). Semiregular Long Period Variables (LPVs) are pulsating red giants or supergiants with periods ranging from variable star light curve (Z Uusae 30-1000 days. They are usually of spectral type M, R, C or N. There are two subclasses; Mira and Majoris) Image courtesy of AAVSO, Cambridge, MA Semiregular. Mira variables are periodic pulsating red giants with a periods of 80 to 1000 days. It is a stage that most mid-sized main sequence stars transition through as they evolve to the red giant branch. Miras have amplitude variations of more than 2.5 magnitudes. Mira (Omicron Ceti) is the prototype Figure 12. H-R diagram with of Mira variable stars. The Sun will eventually become a pulsating Mira star. The Mira instability instability strips labeled strip on the H-R diagram is the region between mid-sized stars on the main sequence and the Diagram courtesy of Wikimedia Commons giant branch. Semiregular variables are giants and supergiants showing periodicity accom- panied by intervals of semiregular or irregular light variation. Their periods range from 30 to 1000 days, generally with amplitude variations of less than 2.5 magnitudes. Antares (α Scorpius) and Betelgeuse (α Orionis) are two promi- nent examples of LPV semiregular variable stars. These stars occupy a region of instability on the H-R diagram similar to the Mira variables. Plotting Cepheids, RR Lyrae, Mira and Semiregular pulsating variable stars on the H-R diagram is not a single plot like non-pulsating stars. During their evolution through the instability strips they are pulsationally unstable – expanding and brightening, then contracting and become dimmer. The instability strips for Miras and Cepheids are especially elongated because of these expansions and contractions. Some pulsating variable stars change in temperature by two spectral classes during one cycle from maximum to minimum. To show the entire cycle of change for individual variable stars, it is necessary to plot them twice on the H-R diagram – both at maximum absolute © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 25 magnitude (MVmax) and minimum absolute magnitude (Mvmin) – along with the corresponding spectral classes. Variable Stars & the H-R Diagram Classroom Activities, Materials and Resources In 1996 a set of curricular materials was written for the American Association of Variable Star Observers (AAVSO) in Cambridge, Massachusetts titled Hands-On Astrophysics – Variable Stars in Math, Science and Computer Class. The materials have been converted, with the support of both AAVSO and the Chandra E/PO office, to an electronic PDF version and renamed Variable Star Astronomy (VSA). The mate- rials are located at http:// www.aavso.org/education/ vsa/. The AAVSO Variable Star Astronomy (VSA) educational project was funded by the National Science Foundation. The content, activities, inves- tigations and software, based on the AAVSO’s unique electronic database of more than 21,000,000 variable star observations, provides students with the necessary information and skills to study and research variable star behavior. Figure 13. The Stellar Evolution: A The VSA materials are posted on the AAVSO website, and three of the activities and investigations, Journey with Chandra Poster Illustration courtesy of Chandra enhanced with extensions and flash versions, have also been posted on the Chandra website at http://chandra.harvard.edu/edu/formal/index.html. Chandra is designed to observe X-rays from high-energy regions of the universe – including cataclysmic variables (supernovas, novas), and X-ray binary systems such as the pulsating red giant Mira A and its white dwarf companion Mira B. Figure 14. The pulsating variable star Mira the Beautiful (Omicron Plotting Variable Stars on the H-R Diagram Ceti) Image courtesy of Chandra Students plot pulsating variable stars on an H-R diagram. The diagram has several bright and nearby stars plotted to show the locations of the main sequence, giant, supergiant and dwarf branches. Students plot both maxima and minima with corresponding stellar classifications for several variables, then identify the type of variability – Cepheid, RR Lyrae, Mira or Semiregular. The investigation includes extensive background infor- mation, student worksheets and answer keys in HTML and PDF. Student Activity http://chandra.harvard.edu/edu/formal/variable_stars/plot.html Stellar Heartbeats is an introductory activity designed to familiarize students with the magnitude scale and the Julian Day by estimating the changing magnitude of a variable star using comparison stars, plotting © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 26 The Earth Scientist a light curve and determining the period. There are HTML, Flash, PDF, and PowerPoint versions. About the http://chandra.harvard.edu/edu/formal/variable_stars/activity1a.html Author A Variable Star in Cygnus uses a set of photos of the variable star W Cyg. By using actual images of W Donna Young develops Cyg students learn how to estimate the changing magnitudes of a variable star with actual compar- educational materials for ison stars against a background of the real sky. Students then plot a light curve and determine the the Chandra X-ray mission, period. There are HTML, Flash, PDF, and PowerPoint versions.http://chandra.harvard.edu/edu/ and is a staff member at formal/variable_stars/activity2a.html the American Association of Variable Star Observers Stellar Cycles: A pre or post assessment ac­tivity complete with a scoring rubric to determine student in Cambridge, MA. She understanding of stellar evolution. The image set for the ac­tivity includes images of the different is the National Science stages of stellar evolution, light curves and H-R diagrams. (HTML, PDF and PowerPoint (PPT) Olympiad astronomy versions) http://chandra.harvard.edu/edu/formal/stellar_cycle/ event supervisor. She NOTE: One, color set of Stellar Life Cycles cards is included with the print version of this journal. presents Chandra and Educators can request additional classroom sets with the Card Sets Request Form at http:// AAVSO educational chandra.harvard.edu/edu/request_special.html materials to formal and informal educators The Chandra Chronicles have two articles describing how the AAVSO amateur observers assisted and Science Olympiad the Chandra X-Ray Observatory during two observing campaigns of the variable star SS Cygni: coaches and teams at Backyard Astronomers Trigger Multi-satellite Observing Campaign on SS Cygni http:// national workshops and chandra.harvard.edu/chronicle/0101/aavso.html conferences. She can be reached at donna@aavso. Astronomers Team Up for Chandra Observations of SS Cygni http://chandra.harvard.edu/ org. chronicle/0300/aavso.html Are you looking for some quality mineral or fossil specimens for your classes? Or maybe for you? Check out the assortment of minerals and fossil specimens available on our Online Store from Nature’s Own! Classroom specimens and collections, jewelry, and household items available! Visit our online store at www.windows2universe.org/store, and click on “Nature’s Own” Windows to the Universe members get a 10% discount! © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 27 Investigating Supernova Remnants Doug Lombardi Ph.D. Candidate Educational Psychology University of Nevada Las Vegas C arl Sagan (1980) said that “if you wish to make an apple pie from scratch, you must first invent the universe” (p. 218). With that idea, he linked pie ingredients (e.g., apples, flour, butter, water, etc.) to basic atomic structure (carbon, oxygen, hydrogen, etc.) and ultimately to the Big Bang. Investigating Supernova Remnants is a classroom activity concerned with an intermediate point in this cosmic process. Specifically, how stars and their remnants are the source for almost all of the chemical elements, as well as their distribution throughout the universe. The activity itself is concerned with how we can identify different types of supernova remnants based on their chemical signature. To better understand the two main types of supernovas, the article first provides an overview of the features of these astronomical phenomena and how these supernovas contribute to scien- tific understanding and the scientific process. The article then introduces the Investigating Supernova Remnants activity and the option of conducting the activity using the freely avail- able ds9 imaging software. In the article wrap-up, it is discussed how this imaging software can be used to engage students in conducting scientific investigations using data collected by NASA’s Chandra X-ray Observatory. Types of Supernovas Much scientific research has been conducted on two types of supernovas. Type Ia supernovas are the complete annihilation of a remnant from a medium mass star (i.e., a star with a mass on the order of our own Sun), which is accreting material from a nearby companion star. Type II super- novas are another type that involve the core collapse of massive stars (i.e., much more massive that the Sun). Type Ia Supernovas. For much of its existence, nuclear fusion in a star’s core exerts an outward pressure that essentially counterbalances the inward force induced by gravitational attraction of the star’s mass. Fusion of hydrogen to helium occurs in a star’s core during the early stages of its exis- tence and fusion of helium to carbon and/or oxygen characterizes the latter part. At this later stage, © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 28 The Earth Scientist the star is commonly referred to as a red giant due to cooling and expansion of the star’s outer layers. Stellar cores that are up to 1.4 times as massive as our Sun, transition into a white dwarf remnant after most of the core helium has fused. White dwarves are created because a lesser thermal pressure in the star cannot overcome gravitational forces and the core collapses. As the core material becomes tightly packed, a degeneracy pressure builds due to filling of electron energy levels. This electron degeneracy pressure then counterbalances the pressure induced by gravitational attraction and the white dwarf remnant is stable. Our Sun is destined to end its existence as a white dwarf. The white dwarf stage is not the end for all medium mass stars. Some explode as a Type Ia super- nova. To result in an explosion, a white dwarf must be in a contact binary system, which means that the dwarf is pulling material from its nearby companion star. This happens when the companion has reached the red giant stage after the white dwarf has formed. As the white dwarf pulls material from the companion star onto itself (a process that scientists call accretion), the mass of the white dwarf grows. Accretion may cause the mass of the dwarf to increase to a value greater than 1.4 times the Sun’s mass, which in turn, causes the remnants’ internal pressure to increase, core temperatures to rise, and unsustainable nuclear fusion to occur. The white dwarf undergoes a thermonuclear explosion and is completely destroyed. Type II Supernovas. In massive stars (i.e., from about eight times as massive as our Sun or greater) that reach the red giant stage, internal core temperatures are hot enough that elements heavier than carbon and oxygen are created in the core. This forms elements such as neon, magnesium, silicon, sulfur, nickel, and iron. As iron builds in the core, it fuses into even heavier elements; however, rather than releasing energy, fusion of iron into heavier elements absorbs energy. A critical value is reached when the iron in the star’s core reaches about 1.4 times our Sun’s mass. At this value, more energy is required for fusion than the star has available and thermal radiation pressure from the star is catastrophically reduced. The result is a nearly instantaneous core collapse and a rebounding explosion called a Type II supernova. The energy produced by the explosion’s shockwave creates elements heavier than iron (e.g., gold, yttrium, uranium) as the shockwave interacts with the star’s outer layers. A stellar remnant of very dense matter (called a neutron star), or a singularity (called a black hole) are also produced from the core collapse. How Do Scientists Know? The Chandra X-ray Observatory measures X-ray light from many high-energy astronomical phenomena, including supernova remnants. Chandra has greatly increased our understanding of the universe, including characterizing important differences between Type Ia and II supernovas. If scientists are just observing light, the following questions arise. n How do they know the type of supernova remnant they are observing? n How do scientists determine the cause of the remnant when the event occurred hundreds or thousands of years ago? n What effect do the different types of supernovas have on the distribution of elements throughout the cosmos? Answering such questions about “cause and effect relationships by seeking the mechanisms that underlie” a phenomena are an important crosscutting concept that spans all of science and some- thing that is essential for our students to know in order to achieve scientific literacy (National Research Council, 2011, p. 4-2). © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 29 Supernova Remnants Activity Investigating Supernova Remnants is an activity that helps students to deepen their understanding about cause and effect by understanding the underlying mechanisms that characterize super- novas. The activity is available for download at http://chandra.harvard.edu/edu/formal/snr/. Investigating Supernova Remnants engages students in an investigation of whether a supernova is a Type Ia or Type II by looking at the element distribution within the remnant. This activity is appro- priate for high school and undergraduate students. Teachers have two options for using Investigating Supernova Remnants in their classrooms. In the first option, students conduct the analysis with the SAOImageds9 software, which is freely available at the Chandra Education Data Analysis Software and Activities web site (http://chandra-ed.harvard. edu). The ds9 software can be used on either on the Windows or Mac operating systems. Students can download data collected from the Chandra X-ray Observatory and use ds9’s sophisticated suite of analysis tools to understand the chemical nature of supernova remnants, as well as other astro- physical properties. Baselining Known Remnants The first thing that students do in Investigating Supernova Remnants is to determine the chemical composition of two events that serve as the baseline for further comparisons. The first remnant is from a supernova that was documented by Renaissance astronomer Tycho Brahe (commonly known as a Tycho’s Supernova Remnant; see Figure 1). This remnant resulted from a Type Ia Supernova resulting from an explosion and complete destruction of a white dwarf. Tycho’s Supernova Remnant has undergone many observations via the Chandra X-ray Observatory, with more information found at http://chandra.harvard.edu/photo/2011/tycho/. The second baseline remnant is SNR G292.0+1.8 (see Figure 2), has an unglamorous name based on its catalog coding, but nevertheless has been an important object for gaining “textbook” understanding of super- novas, specifically those that are rich in oxygen content. SNR G292.0+1.8 resulted from a Type II supernova and more information about this event can be found at http://chandra.harvard.edu/ photo/2007/g292/. Figure 1 (left). An image of Tycho’s Supernova Remnant, which was formed by a Type Ia supernova of a white dwarf located about 13,000 light years from Earth. Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al. Figure 2 (right). An image of SNR G292.0+1.8, a remnant of a Type II supernova formed by the explosion of a massive star located about 20,000 light years from Earth. Credit: X-ray: NASA/CXC/Penn State/S.Park et al.; Optical: Pal.Obs. DSS To determine the chemical compositions of Tycho’s Supernova Remnant and SNR G292.0+1.8, students look for peak emission lines in energy plots that either (a) they generate using the ds9 imaging and analysis software or (b) are provided in the pencil and paper version of the activity (see © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 30 The Earth Scientist Figures 3 and 4). Energy plots represent the spectrum of different X-ray photon energies collected by Chandra during an observing run and provide a chemical “fingerprint” of remnants. Investigating Supernova Remnants includes a database of different photon energies and their elements that students can use as they look up peak emission lines that they can identify on the graph. Figure 3. Bremsstrahlung The peaks produced by the elements are Spectrum of Tycho’s SNR referred to as emission lines, the greater the peak, the stronger the emission line (See Figures 3 and 4). To determine relative strength of the peaks, the X-ray spectra the emission lines are superimposed on top of a large curve that is also drawn as white lines on Figures 3 and 4. This curve is produced by the acceleration of electrons as they are deflected by positively charged atomic nuclei and is called Bremsstrahlung (breaking) radi- Figure 4. Bremsstrahlung Spectrum of G292.0+1.8 ation. The distribution of photon energies due to Bremsstrahlung radiation is called a continuous spectrum. Peak emission lines that spike above the Bremsstrahlung curve correspond to the ejection of K and L shell electrons knocked out of atoms in collisions with the high-energy electrons. The ener- gies of these emission lines can be used to identify the elements in plasma rich environ- ments, such as supernova remnants. Beyond the Baseline Once students have identified the chemical structure of Tycho’s Supernova Remnant and SNR G292.0+1.8—the known Type Ia and Type II remnants, respectively—the activity pushes students to examine five mystery remnants. The purpose of this extension is to have students use the infor- mation they have gained in the two baseline remnants to make inferences about what types of supernovas the mystery remnants represent. In other words, which of the supernova remnants look chemically similar to Tycho’s and may be Type Ia, and which look similar to SNR G292.0+1.8 and may be Type II? Again, the spectral plots of these mystery remnants and associated extension ques- tions are included in the Investigating Supernova Remnants activity. Developing Student Scientists Investigating Supernova Remnants is an excellent platform for launching students into conducting scientific investigations using freely available data, which in large part, may have not been analyzed by astronomers. Students can conduct this activity in pencil and paper mode with hard copies of X-ray spectra; however, this is activity is most powerful for students if they use the ds9 imaging analysis software. This software allows the user to download a toolbox onto their desktop and remotely access dedicated Linux servers which process the analysis commands. The ds9 image analysis software allows educators, students, amateur astronomers and the general public to perform X-ray astronomy data analysis using data sets from the Chandra X-ray Observatory, the ds9 image display program, and astrophysical software analysis tools. The program uses the same analysis process that an X-ray astronomer would follow in analyzing the © 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 31 data from a Chandra observation. The download instructions to install the ds9 toolbox on your desktop are located athttp://chandra-ed.harvard.edu/install.html. The intro- About the Author duction at http://chandra-ed.harvard.edu/learning_ds9overview.htmldescribes the Doug Lombardi is a doctoral candidate overview and purpose of the software. in Educational Psychology at the Almost all of the Chandra observations are freely available online at http://cxc.harvard. University of Nevada, Las Vegas. edu/cda/public.html. These data are generally released to the public after about one year His research is on climate change from the observation period to allow the proposing scientific team a “first crack” at the education and the role of critical information. However, even though scientists have had a first look opportunity, much of evaluation in reappraising plausibility the data may not have been involved in the scientific analysis. Therefore, there are many judgments and conceptual change. He data that are unexplored. This presents a wonderful opportunity for students to provide has appreciable experience working in a unique analysis of astronomical information and the potential for students to do some NASA education enterprises and has meaningful science. By using ds9, which is the same imaging analysis software used by been a teaching resource agent for the astronomers, and the wealth of data that has been collected by the Chandra X-ray obser- agency’s Chandra X-ray Observatory vatory, students can actively engage in the scientific process. This in turn will increase since 2001. Doug is also a project their learning of phenomena, such as supernova remnants, which are essential for under- facilitator at the Regional Professional standing the material composition of our universe. Development Program, serving as a science education specialist and the References program’s internal evaluator. He is a National Research Council. (2011). A framework for K-12 science education: Practices, crosscutting concepts, licensed physics and mathematics and core Ideas. Committee on a Conceptual Framework for New K-12 Science Education teacher, with 12 years experience in a Standards. Board on Science Education, Division of Behavioral and Social Sciences and variety of educational settings. Doug Education. Washington, D. C.: The National Academies Press. can be reached at lombardi.doug@ Sagan, C. (1980). Cosmos. New York: Random House. gmail.com. Open Windows to the Universe at www.windows2universe.org From Earth science to astronomy, your Earth and space science ecosystem for learning! • Science content – 9000+ pages • Over 100 classroom-tested activities, interactives and games • 3 levels, English and Spanish • Free Educator newsletter • Educator Members receive special services and benefits: Join Today  Free access to formatted classroom $20/yr - $10/yr for activities, student worksheets, Teacher keys, associated graphics and data, downloadable ppts and more! $230 value! NESTA members! www.windows2universe.org/  My W2U, Journal, store discounts, calendars, opportunities membership.html for teachers, web seminars, and no ads! Windows to the Universe is a project of the National Earth Science Teachers Association © 2012 National Earth Science Teachers Association. All Rights Reserved. Page 32 The Earth Scientist Visit American Geosciences Institute Resources Excellence in Earth Your one-stop shop for marine Science Education science curriculum supplies . • Earth Science Week • Earth Magazine www.LeaveOnlyBubbles.com • Curriculum resources 715-659-5427 • Teacher PD

• Geoscience Career Info Leave Only Bubbles is a subsidiary of “What If…?” Scientific, a teacher- owned and operated earth science supply company founded in 1997. http://www.agiweb.org/geoeducation.html Advertising in the NESTA Quarterly Journal, The Earth Scientist NESTA will accept advertisements that are relevant to Earth and space science education. A limited number of spaces for advertisements are available in each issue. Artwork We accept CD or electronic ad files in the following formats: high-res PDF, TIFF or high-res JPEG. Files must have a minimum resolution of 300 dpi. Ads can be in color. Advertising Rates Full-page 7.5” w × 10” h $500 Quarter-page 3.625”w × 4.75”h $125 Half-page 7.25” w × 4.75” h $250 Eighth-page 3.625”w × 2.375”h $75 Submission Deadlines for Advertisements Submission dates given below are the latest possible dates by which ads can be accepted for a given issue. Advertisers are advised to submit their ads well in advance of these dates, to ensure any problems with the ads can be addressed prior to issue preparation. The TES Editor is responsible for decisions regarding the appropriateness of advertisements in TES. Issue Submission Deadline Mailing Date Spring January 15 March 1 For further information contact Summer April 15 June 1 Howard Dimmick Fall July 15 September 1 Treasurer Winter October 31 January 1

© 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 33 The Earth Scientist (TES) NESTA Membership MANUSCRIPT GUIDELINES Dues Structure NESTA encourages articles that provide exemplary state-of-the-art tested classroom activities and background science content relevant to K-12 classroom Earth and Space Basic Membership (US and Science teachers. International) – includes access to • Original material only; references must be properly cited according to APA style manual online versions (only) of The Earth • Clean and concise writing style, spell checked and grammar checked Scientist (not including posters), monthly • Demonstrates clear classroom relevance NESTA, E-News, access to TES archives online, NESTA Special Alert e-mailings, Format Specifications access to member-only sections of the • Manuscripts should be submitted electronically – Microsoft Word (PC or Mac) website, and full voting privileges. • Length of manuscript should not exceed 2000 words. • One year – $20 • All submissions must include a summary/abstract. • Two years – $40 • Photos and graphs: may not be embedded, but must be submitted as separate files, of • Three years – $60 excellent quality and in PDF, EPS, TIFF or JPEG format. 300 dpi minimum resolution. Color or black and white are both accepted. Membership with Print Supplement* – – Photos/charts should not be embedded in the Word file. References to photo/ includes a printed copy of TES mailed to chart placement may be made in the body of the article identified with some you quarterly, frequently including poster marker: <Figure 1 here> or [Figure 1 in this area]. inserts, in addition to Basic Membership • Figures should be numbered and include captions (Figure 1. XYZ.). benefits (US rates): – Captions may be included with photo/chart reference in a separate Microsoft Word file or at the end of the article. • One year – $35 • If using pictures with people, a signed model release will be required for EACH indi- • Two years – $68 vidual whose face is recognizable. • Three years – $100 • Each article must include: author(s) names, the school/organizations, mailing address, home and work phone numbers (which will not be published), and e-mail addresses. * in Mexico and Canada, our rates for Membership with Print Supplement Review are slightly higher, because of mailing Manuscripts are to be submitted to the Editor, via the email address at the bottom of costs: the page. Manuscripts are reviewed by the Editor for content and language. The Editor is responsible for final decisions on the publication of each manuscript. Manuscripts may • One year – $45 be accepted as is, returned for minor or major revisions, or declined, based on the decision • Two years – $88 of the Editor. The Editor reserves the right to edit the manuscript for typographical or • Three years – $130 language usage errors. Domestic Library Rate – includes print Page Charges copies of The Earth Scientist only, and A fee of $100 per page is charged to authors who have institutional, industrial, or grant does not include NESTA membership funds available to pay publication costs. Authors without access to such funds are strongly urged to assist in defraying costs of publication to the extent their resources permit, but • One year – $70 payment of page charges is not required from such authors. Payment of page charges has no bearing on the decision to accept or reject a manuscript. Add Windows to the Universe Educator Membership Subscription Copyright Transfer Waiver to your NESTA membership (50% The lead author of the article shall submit a signed NESTA Copyright Transfer Waiver. discount from non-NESTA member The waiver form may be obtained from the NESTA web page. When completed AND rates) – provides access to special signed it should be sent to the Editor. It may be sent as a printed original by US mail capabilities and services on NESTA’s (address below), or as a pdf attachment via e-mail. premier Earth and Space Science We cannot begin the production process until this signed waiver has been received. Please Education website available at http:// help us to expedite the publication of your paper with your immediate compliance. If you www.windows2universe.org have any questions, please e-mail the NESTA Editor or Executive Director as listed below. • One year – $10 • Two years – $18 Submission Deadlines Issue Submission Mailing For further information contact: • Three years – $24 Deadline Date Tom Ervin, EDITOR Spring January 15 March 1

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© 2012 National Earth Science Teachers Association. All Rights Reserved. Page 34 The Earth Scientist 2012 National This year the 4th week in April is NATIONAL ASTRONOMY WEEK – a week-long celebration of stargazing that culminates on Saturday the 28th with National Astronomy Day. Astronomy week is a “movable” holiday, and takes place each year in late April or Astronomy early May, during the week of the first quarter moon. The celebration began in 1973 when an astronomer from northern California, Doug Berger, set up telescopes on street corners, Day parks and mall parking lots as a way to bring astronomy to the general public. The event has grown to national and international proportions with amateur astronomy clubs, planetariums, observatories and other science organizations throughout the world hosting special events APRIL 28 in honor of Astronomy Day, including England, Canada, New Zealand, Finland, Sweden, the Philippines, Argentina, Malaysia and New Guinea. The purpose of National Astronomy Day is to provide a means of interaction between the general public and various amateur and professional astronomy enthusiasts – a way of bringing the beauty of the night sky to everyone who is intrigued with astronomy and would like to know more about stars and the universe. As a science teacher, have you ever considered joining your local astronomy club? If you have always wanted to look through a telescope, then there is no better time than during National Astronomy Week and Astronomy Day. Contact your local amateur astronomy club, museum, science center, library, planetarium, national park or observatory for a list of programs or events in your area – or check the listings in your local newspaper. At http://media.skysurvey.org/interactive360/index.html there is a 360 degree interactive Photopic Sky Survey 5,000 megapixel photograph of the entire night sky stitched together from 37,440 individual exposures. The Photopic Sky Survey was the project of Nick Risinger, and he states that ….”In it we see tens of millions of stars, the glowing factories of newborn ones, and a rich tapestry of dust all floating on a state of unimaginable proportions. I hope you enjoy this new view of our place in the universe as much as I have enjoyed making it……” Maybe this stunning view of the night sky and the Milky Way Galaxy will start you on your own journey to visit the starry sky. Membership Information RENEW OR UPDATE YOUR MEMBERSHIP INFORMATION the completed form to the address indicated. Your Electronic renewal notices are now automatically e-mailed expiration date is listed on the address label of The to each member. They will be sent at 4, 2, and 1-week Earth Scientist. intervals before your membership expires. If you have not • If you would like additional information about received a renewal notice please contact membership@ NESTA membership, please email membership@ nestanet.org. NESTA members can renew their member- nestanet.org or call the NESTA Office at ship and edit their Personal Information by going online. 720-328-5351 • Go to NESTA Home Page ADDRESS OR EMAIL CHANGES • Click on Member Login It is very important that we have your current address and • Welcome to your User Account email. To update your membership information Complete Username and Password. If you do not 1. Go to www.nestanet.org know your password, click on the “Request new 2. Click on LOG IN password” tab 3. Welcome to NESTA Member Menu • MY NESTA – Here you will find your: Account Edit your profile – please use this to update your settings and personal information (under Edit you information. It is very important that this infor- can change your password) mation be current. • Membeship Expiration Date MEMBERSHIP EXPIRATION • Renew Now You will be notified via email regarding your If you do not wish to use a credit card, you membership renewal. can renew by check or money order. Click on If you wish further information regarding Download Renew Membership application. Mail membership, please contact

© 2012 National Earth Science Teachers Association. All Rights Reserved. Volume XXVIII, Issue 1 Page 35 National Earth Science Teachers Association Events at 2012 Indianapolis NSTA Conference All NESTA sessions are in the Westin Indianapolis, Grand Ballroom 5, unless otherwise indicated Tickets for both field trips and Saturday NESTA Luncheon are available through NESTA at www.nestanet.org beginning January 16, 2012. Wednesday, March 28 NESTA Field Trip – From Glacial Till to Minerals that Thrill! – full day ($35 in advance, $40 on-site) Thursday, March 29 NESTA Field Trip – Sampling Midwest Geology – afternoon ($30 in advance, $35 on-site) Friday, March 30 9:30 – 10:30 am NESTA Geology Share-a-Thon 11:00 am – noon NESTA Atmospheres, Oceans, and Climate Change Share-a-Thon 12:30 – 1:30 pm NESTA Earth System Science Share-a-Thon 2:00 – 3:00 pm American Geophysical Union Lecture! “FrankenClimate: The Perils of Engineering Our Way Out of Global Warming”, by Prof. Gabriel Filippelli, Indiana Convention Center, Sagamore Ballroom 3 2:00 – 3:00 pm Drama in Near Earth Space – The Sun, Space Weather, and Earth’s Magnetic Field As We Approach Solar Maximum!, Westin Grand Ballroom 3 3:30 – 4:30 pm Earth and Space Science Education Today in K-12: Status and Trends at the State and National Levels 5:00 – 6:30 pm IESTA & OESTA Rock and Mineral Raffle 6:30 – 8:00 pm Friends of Earth Science Reception, Westin Grand Ballroom 1 Saturday, March 31 8:00 – 9:00 am Activities Across the Earth System 9:30 – 10:30 am Strategies for Teaching Charged Topics in the Earth Science Classroom 11:30 – 1:00 pm NESTA Earth and Space Science Educator Luncheon, “Dust in the Wind – The Geological Record of Ancient Atmospheric Circulation” by Prof. Steven Hovan, Westin State Room, tickets available through NESTA at www.nestanet.org for $40 per person in advance or $45 on-site (tickets limited). 2:00 – 3:00 pm NESTA Astronomy, Space, and Planetary Science Share-a-Thon 2:00 – 3:00 pm Our Changing Planet, Westin Grand Ballroom 3 3:30 – 5:00 pm NESTA Rock and Mineral Raffle 5:30 – 7:00 pm NESTA Annual Membership Meeting NESTA gratefully acknowledges co-sponsorship of our events by the following organizations:  © 2012 National Earth Science Teachers Association. All Rights Reserved. NESTA NON PROFIT ORG. U.S. POSTAGE 4041 HANOVER AVE STE 100 PAID BOULDER CO 80305-5975 PERMIT #718 SYRACUSE NY PLEASE INFORM US IF YOU ARE MOVING CHANGE SERVICE REQUESTED This illustration shows the GISP2 ice core drill dome site on the Greenland summit ice sheet in the early 1990’s. The Greenland summit lies within the auroral footprint of the northern Polar Region, where ionization from charged particles entering the Earth’s atmosphere produce the often spectacular Aurora Borealis. Oxidation products from solar activity and supernova events, such as nitrates, settle to the surface of the Greenland ice sheet and become part of the ice core record. Illustration courtesy of Jean-Pierre Normand, artist, Montreal, Canada