Summary
Students sort 14 star spectra and creating a star classification system to develop science classification skills. Though analysis of figures that describe the OBAFGKM classification system and temperature effects on element absorption in stars, students will learn that star spectra can be used to find a star's surface temperature. A summative reading describes OBAFGKM star types that are more likely to harbor planets that could support complex life, reinforcing the connection between star spectra, temperature, and science's search for habitable planets.
Essential Question(s)
How do star spectra help us look for planets capable of supporting complex life?
Snapshot
Engage
Students consider physical characteristics of stars that make stars more likely to support planets with complex life. Students recall or are introduced to star spectra as a tool for remote measurements of star properties.
Explore
Students work in a team to sort 14 star spectra and create a classification system for the stars. Teams are paired to create a consensus classification and discuss the communication issues involved in classification processes.
Explain
Students study Figures A1–A3 to learn about and apply the canonical OBAFGKM classification system. Using Figures B1–B4 as guides, students learn why light absorption by elements in stars is dependent on temperature.
Extend
Students have opportunities to learn more about the history and applications of the OBAFGKM classification system and practice quantitative problem-solving using a blackbody radiation equation.
Evaluate
After reading a NASA article on OBAFGKM star types that are more likely to support planets with life, students use the 4-2-1 strategy with a timed writing or cognitive comics step to identify the most important information in the article and summarize the lesson.
Materials
Activity Handout- Classifying Stars as Spectra (attached; one per student)
Data Handout- Classifying Stars as Spectra (attached; one per student)
PDF handout of a NASA reading for the Evaluate phase (attached; one per student)
Sample Response Handout- Classifying Stars as Spectra (attached; for teacher use)
Lesson Slides- Classifying Stars as Spectra (attached)
Computer (one per group)
Wifi
Scissors (optional)
Glue (optional)
Student notebook
Pencil or pen
Engage
Use the attached Lesson Slides to help you guide students through the lesson. Edit, add, or omit slides to suit your needs.
Using slides 2 through slide 4, introduce the lesson title, essential question, and lesson objectives.
Distribute the "Activity Handout" to the students. Ask students to work on the Engage questions first (either on their own or with elbow partners, perhaps as a Bellringer) before engaging in a whole class discussion.
One option to save time is to address engage questions at the whole class level, only.
Use slides 5 and 6 to discuss the Engage questions and prepare students for the Explore phase. The level of explanation needed with slide 6 depends on your students' background experience. You are either engaging a review of previous knowledge about light, spectra, and absorption lines or introducing the fundamental information needed for the Explore phase.
Explore
At the whole class level, show students slide 7. Tell students that the goal is to look for similarities and differences in 14 star spectra and sort them into groups. Connect to the Engage by noting that sorting processes like these led to the identification of star groups that are more likely to harbor life. Three spectra are shown on the left side of slide 7 and should be used in a guided practice. Ask students to discuss the similarities and differences they see in these spectra and identify the most distinctive spectrum. Most students will conclude that stars "2" and "157" are more similar and that "346" is the most distinctive. Use Slide 7 to also introduce the table for reporting classification results. This table is in the activity handout.
Go to the SDSS database and find the table shown on slide 8
Click on a blue "fiber" link
Scroll down to find the spectrum on the data page as seen on slide 9
Once teams have complete Part A, in the Activity handout, pair teams to work through PART B. Use Slide 10 to trigger that transition. Remind students to record written notes of their discussion. Consensus schemes can be reported in a table (like those used in part A), but also encourage groups to create alternative/better ways to present their classification scheme. For example, a decision tree is a really nice way to present a classification scheme.
Before moving onto the Explain phase, bring the class together for a short discussion of the questions posed in Part B of the Explore. This discussion would be a touchpoint to emphasize general points about scientific classification and collaboration. Refer to the Sample Responses handout for guidance on this discussion. A key point is that classification is somewhat arbitrary and depends on the data available and used.
Explain
Show students slide 11 to introduce the spectral lines (Table A1) and classification labels (Table A2) used in the OBAFGKM system.
Use slide 12 to clarify the goals of the Explain questions and orient the students to Figure A3: a star spectra the students will classify using the OBAFGKM system.
Ask students to work with the figures to answer the questions individually or in small groups. Circulate to help students and encourage them to make their own hypotheses. Questions can assigned as a homework assignment, though students may get stuck and struggle to complete the set without the support of peers or a teacher.
After students have worked through the questions, facilitate a whole class discussion to review understanding. To identify areas of confusion before or after the discussion, consider using the Muddiest Point strategy. Use slide 13 if you use the Muddiest Point check-in here.
Use slide 14 to support a discussion of questions A1–A5, which work together to introduce students to the OBAFGKM system with questions about the Sun that refer to Tables A1 and A2. Use slides 15–17 to support a discussion of questions A6–A11, which work together to allow students to characterize the star in Figure A3. Slide 15 allows you to work out assignment of the spectra in Figure A3 step by step. You have slide 16 to use as a reference. You have slide 17 to facilitate a class vote on the assignment.
Slides 18–21 support PART B questions, which explains that spectral lines change with star temperature. Prepare by referring to the SAMPLE ANSWER HANDOUT for this more difficult material. Slide 18 uses Bohr models to show excitation and absorption. Slide 19 gives you access to Figures B1–B4 to work through the questions. Slides 20 and 21 show specific models to help you compare the atomic structure of helium and hydrogen and the effect that has on optimal absorption temperatures in question B5.
