LESSON PLAN: CATEGORIZING CELESTIAL OBJECTS
Background, Activities and Critical Analysis
By Adnaan Wasey, Online NewsHour

Subject(s): Space science, earth science, general science

Estimated Time: One 45-minute period with options to extend

Grade Level: 9-12 (lesson can be modified for lower grades)

Overview: Students will:

1. Apply astronomy concepts to develop and test a classification system for planets.
2. Participate in a class vote on planet classification.
3. Read an article about astronomers' response to the planetary categorization.
4. Discuss and write an essay about the scientist's role as decision-makers for the public.

TO MAKE THESE LESSONS BETTER

Correlation to National Standards

Materials

• Copies of an Online NewsHour article about the debate over Pluto's planetary status, "Pluto Debate Eclipsing More Important Research, Some Say", available at
  http://www.pbs.org/newshour/indepth_coverage/science/pluto/news.html (If students do not have Internet access, PDF)
• Copies of the "What is a planet?" instructions, data sheet, worksheet, rubric and homework instructions (printer-friendly PDF) (one per student)
• Copies and transparency (optional) of "How does your definition compare?" (printer-friendly PDF) instructions and worksheet (one per student or one transparency)
• Printout of rubric (printer-friendly PDF) (for teacher)
• Printout of "Are these planets?" (printer-friendly PDF) (for teacher)
• Pen and paper for each student, calculators (optional)
• Projector (optional, for transparencies)
• Solar system posters or astronomy text books (if available)
• Download all materials as one file (printer-friendly PDF)
• Full coverage of the "Pluto Debate" by the Online NewsHour, including NewsHour with Jim Lehrer TV segments, is available at
  http://www.pbs.org/newshour/indepth_coverage/science/pluto/index.html

Background

• In August 2006, the International Astronomical Union voted to demote Pluto to "dwarf planet" status, leaving eight full "planets" in the solar system.
• The new "planet" definition is based on the ability for a celestial object to keep a spherical shape and to dominate its orbit around the Sun.
• Before this decision, there was no official definition of a "planet."
• Three celestial bodies are now given the "dwarf planet" distinction:
  • Pluto
  • Eris (an object discovered in 2004 in the Kuiper Belt, a region at the edge of the solar system)
  • Ceres (a body in the solar system's main asteroid belt, discovered 200 years ago)
• Discoveries in recent years (Eris and the other planet-like objects in other star systems) have brought the question of what a planet is to the forefront in the space science community.

Procedure

1. Ask students for examples of scientific classification schemes (taxonomy in biology, geologic timescales, planet categorization, etc.). Ask the students how they think scientists create these classifications systems.

2. Tell the students about the IAU's August 2006 decision to demote Pluto from "planet" to "dwarf planet" then introduce the planet categorization exercise. Students will examine scientific data, develop a scientifically based definition of a planet in small groups, then present their definition to the class so the class can vote for their favorite.

3. Distribute the "What is a planet?" handouts containing the assignment instructions, celestial body data sheet, a worksheet, rubric and homework instructions. You may also choose to display data on the projector or blackboard.

4. Review the assignment and rubric with the students and answer any clarification questions. Tell the students that astronomers were considering many definitions, that science is always evolving, and that the IAU realizes that their current "planet" definition may need to change.

5. Assign appropriate groups, or have the students work on their own, to examine the data sheets and develop their planetary definition.

6. As the students work, refer to the "Are these planets?" page to help the students refine their definitions.

7. Once the students have created their definitions, collect their worksheets. Ask for a representative from each group, or volunteers from the class, to present their definition and reasoning to the class. You may also want to read the definitions yourself to maintain anonymity.

8. Conduct a poll to see which definition the students like best.

9. Show the class the International Astronomical Union's actual August 2006 planetary definition "How does your definition compare?" by distributing handouts, showing a transparency, or reading the definition aloud. Discuss similarities and differences between the definition the class chose and the one chosen by astronomers.

10. (Optional) Ask the students to read the article "Pluto Debate Eclipsing More Important Research, Some Say" (http://www.pbs.org/newshour/indepth_coverage/science/pluto/news.html; if students do not have Internet access, PDF) in class or as a homework assignment. Students may also visit the "Pluto Debate" Web site at the Online NewsHour:
http://www.pbs.org/newshour/indepth_coverage/science/pluto/index.html

11. (Optional Extension Activity) Download the homework assignment (printer-friendly PDF)

Lead a discussion about the role of the scientist in their community as a precursor to a homework essay, or ask students to investigate the subject on their own as part of their homework assignment. Students may examine one or more of these questions:

• Is voting on a scientific concept in keeping with the ethical tradition of science and the scientist's search for the truth?
• Is voting a valid way to get the opinion of the scientific community?
• Should scientists accept a "best available explanation" though they know it may not be correct?
• Do you think the IAU's planetary definition decision was made by examining enough data, using logical arguments, and using an appropriate amount of skepticism?
• What new scientific evidence would help resolve the planetary definition debate?

Additional Resources for Teachers

The Online NewsHour's in-depth coverage of planetary categorization, "The Pluto Debate," including segments from the NewsHour with Jim Lehrer TV segments, is available at:
http://www.pbs.org/newshour/indepth_coverage/science/pluto/index.html

National Standards

Correlation to National Science Standards
(from the National Science Education Standards site at http://books.nap.edu/html/nses/html/6e.html):

Content Standard G: History and Nature of Science

McRel Compendium of K-12 Standards Addressed:

Nature of Science
Standard 11. Understands the nature of scientific knowledge
Standard 12. Understands the nature of scientific inquiry
Standard 13. Understands the scientific enterprise

Mathematics
Standard 1. Uses a variety of strategies in the problem-solving process
Standard 2. Understands and applies basic and advanced properties of the concepts of numbers
Standard 4. Understands and applies basic and advanced properties of the concepts of measurement
Standard 9. Understands the general nature and uses of mathematics

Language Arts
Standard 1. Uses the general skills and strategies of the writing process
Standard 3. Uses grammatical and mechanical conventions in written compositions
Standard 5. Uses the general skills and strategies of the reading process
Standard 7. Uses reading skills and strategies to understand and interpret a variety of informational texts
Standard 8. Uses listening and speaking strategies for different purposes

Working with Others
Standard 1. Contributes to the overall effort of a group
Standard 3. Works well with diverse individuals and in diverse situations
Standard 4. Displays effective interpersonal communication skills

Life Work
Standard 2. Uses various information sources, including those of a technical nature, to accomplish specific tasks

Thinking and Reasoning
Standard 1. Understands and applies the basic principles of presenting an argument
Standard 2. Understands and applies basic principles of logic and reasoning
Standard 3. Effectively uses mental processes that are based on identifying similarities and differences
Standard 6. Applies decision-making techniques

About the Author Adnaan Wasey is an associate editor at the Online NewsHour. He has degrees in Engineering and Chemistry and taught high school science before joining the NewsHour.

To find out more about opportunities to contribute to this site, contact Leah Clapman at extra@newshour.org.