CATEGORIZING CELESTIAL OBJECTS
Background, Activities and Critical Analysis
Adnaan Wasey, Online NewsHour
Space science, earth science, general science
Time: One 45-minute period with options to extend
Level: 9-12 (lesson can be modified for lower grades)
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.
THESE LESSONS BETTER
to National Standards
of an Online NewsHour article about the debate over Pluto's planetary
status, "Pluto Debate Eclipsing More Important Research, Some Say",
(If students do not have Internet access, PDF)
of the "What is a planet?" instructions, data sheet, worksheet,
rubric and homework instructions (printer-friendly PDF)
(one per student)
and transparency (optional) of "How does your definition compare?"
instructions and worksheet (one per student or one transparency)
of rubric (printer-friendly PDF)
of "Are these planets?" (printer-friendly PDF)
- Pen and
paper for each student, calculators (optional)
(optional, for transparencies)
system posters or astronomy text books (if available)
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
- In August
2006, the International Astronomical Union voted to demote Pluto to
"dwarf planet" status, leaving eight full "planets" in the
- 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
this decision, there was no official definition of a "planet."
celestial bodies are now given the "dwarf planet" distinction:
(an object discovered in 2004 in the Kuiper Belt, a region at the
edge of the solar system)
(a body in the solar system's main asteroid belt, discovered 200
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.
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.
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.
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.
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.
a poll to see which definition the students like best.
9. Show the
class the International Astronomical Union's actual August 2006 planetary
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
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:
Extension Activity) Download the homework assignment (printer-friendly
Lead a discussion
about the role of the scientist in their community as a precursor to a
essay, or ask students to investigate the subject on their own as
part of their homework assignment. Students may examine one or more of
- 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?
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
- What new
scientific evidence would help resolve the planetary definition debate?
Resources for Teachers
NewsHour's in-depth coverage of planetary categorization, "The Pluto
Debate," including segments from the NewsHour with Jim Lehrer TV
segments, is available at:
to National Science Standards
(from the National Science Education Standards site at http://books.nap.edu/html/nses/html/6e.html):
G: History and Nature of Science
Compendium of K-12 Standards Addressed:
Standard 11. Understands the nature of scientific knowledge
Standard 12. Understands the nature of scientific inquiry
Standard 13. Understands the scientific enterprise
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
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
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
Standard 2. Uses various information sources, including those of a technical
nature, to accomplish specific tasks
Standard 1. Understands and applies the basic principles of presenting
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
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.
find out more about opportunities to contribute to this site, contact
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