See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/281410178
The Controversy Over Pluto: Planet or Astronomic Oddball?
Article in Science Scope · October 2015
DOI: 10.2505/4/ss15_039_01_18
CITATIONS
READS
0
2,742
3 authors, including:
Sissy S. Wong
Irasema Ortega
University of Houston
University of Alaska Anchorage
32 PUBLICATIONS 381 CITATIONS
8 PUBLICATIONS 191 CITATIONS
SEE PROFILE
Some of the authors of this publication are also working on these related projects:
Beginning Secondary Science Teachers View project
All content following this page was uploaded by Sissy S. Wong on 01 September 2015.
The user has requested enhancement of the downloaded file.
SEE PROFILE
Copyright © 2015, National Science Teachers Association (NSTA).
Reprinted with permission from Science Scope, Vol. 39, No. 1, September 2015.
THE CONTROVERSY
OVER PLUTO
PLANET OR
ASTRONOMIC
ODDBALL?
by Douglas Llewellyn,
Sissy S. Wong,
and Irasema Ortega
These two full-frame images of Pluto and Charon were collected separately by New
Horizons during approach on July 13 and July 14, 2015. The relative reflectivity, size,
separation, and orientations of Pluto and Charon are approximated in this composite
image, and they are shown in approximate true color.
NASA-JHUAPL-SWRI
18
M
rs. Seaver poses a question to her sixth graders: “How many planets are there in our solar
system? Eight? Nine? Fourteen? More than
14?” The question seems to astound most of the students. They have just started studying the solar system
and their science book from 2006 shows nine planets:
four rocky, inner planets (Mercury, Venus, Earth, and
Mars); four gas outer giants (Jupiter, Saturn, Uranus,
and Neptune); and the farthest outer planet, and most
popular of all, Pluto.
Mrs. Seaver knows her middle school students are
naturally curious about our solar system and that this
question is a great way to introduce the new astronomy
unit. She also knows that when given the opportunity,
her students will use their creativity, imagination, and
prior knowledge to discuss the solar system, just as astronomers use their creativity, imagination, and prior
knowledge when they explore the universe.
One way for Mrs. Seaver to tap into this natural curiosity about our solar system is to have students investigate the controversy regarding the reclassification of
Pluto, as well as study scientific controversies that increase students’ knowledge about space, engage them
in the nature of science, and develop their analysis and
argumentation skills.
According to Clary and Wandersee (2013), a scientific controversy is “a legitimate and extended argument, in which scientists marshal data and evidence
to support a particular consensus on an important issue” (p. 40). There are various ways to include science
controversies and argumentation in a middle level science class; however, in this article, we have adopted
Clary and Wandersee’s Historical Controversy Case
Study (HCCS) model, in which students are provided
a controversy and given opportunities to investigate it,
engage in argumentation about it, and reach a conclusion based on sound evidence. Just as scientists need
to convince other scientists that their evidence is reliable, high quality, and relevant (Sampson, Enderle,
and Grooms 2013), it is important to include activities
in class that will foster students’ ability to use reliable
and appropriate evidence to support their claims and
conclusions. In this article, we will show how studying scientific controversies can support scientific argumentation and increased science literacy.
Scientific argumentation as fostered by
the Common Core State Standards (CCSS)
and the Next Generation Science Standards
(NGSS)
Argumentation plays a dominant role in the CCSS for
English/Language Arts (NGAC and CCSSO 2010) and
the NGSS (NGSS Lead States 2013). The CCSS reading standards for literacy in science for grades 6–8
state that, by the end of middle school, students should
be able to
•
gather relevant information from multiple print
and digital sources;
•
determine the central ideas or conclusions of a
text and provide an accurate summary of the text
distinct from prior knowledge or opinions;
•
determine the meaning of symbols, key terms,
and other domain-specific words and phrases as
they are used in a specific scientific or technical
context relevant to grades 6–8 texts and topics;
and
•
integrate quantitative or technical information
expressed in words in a text with a version of that
information expressed visually (e.g., in a chart,
diagram, model, graph, or table) (NGAC and
CCSSO 2010).
NASA-JHUAPL-SWRI
Similarly, the CCSS writing standards for literacy in
science for grades 6–8 state that by the end of middle
school, students should be able to
A view of Pluto and Charon as they would appear if placed
slightly above Earth’s surface and viewed from a great
distance.
•
write arguments focused on discipline-specific
content;
•
introduce claim(s) about a topic or issue,
acknowledge and distinguish the claim(s) from
alternate or opposing claims, and organize the
reasons and evidence logically;
•
support claim(s) with logical reasoning and
relevant, accurate data and evidence that
S e p t e m b e r 2 0 15
19
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
demonstrate an understanding of the topic or text,
using credible sources;
•
use words, phrases, and clauses to create
cohesion and clarify the relationships among
claim(s), counterclaims, reasons, and evidence;
•
provide a concluding statement or section
that follows from and supports the argument
presented; and
•
draw evidence from informational texts to support
analysis, reflection, and research (NGAC and
CCSSO 2010).
This Pluto-controversy activity supports the NGSS
(NGSS Lead States 2013) and gives students an opportunity to develop their evidence-based argumentation
skills and engage in literacy practices cited in both the
CCSS and the NGSS.
Early history of Pluto
Before starting a unit on the controversy over Pluto,
it is important that the classroom teacher have a solid
understanding of Pluto’s history. The following facts
will be helpful:
• In 1906, Percival Lowell, a wealthy Bostonian who
founded the Lowell Observatory in Flagstaff,
Arizona, in 1894, started an extensive project
in search of a possible ninth planet, which he
termed “Planet X.” Although Lowell spent many
years searching the skies, his dream of locating
Planet X evaded him.
• In 1930, Clyde Tombaugh, a farmer and amateur
astronomer from Streator, Illinois, whose job it was
to sweep the floors and clean the telescopes at the
Lowell Observatory, spent his spare time gazing at
the night sky looking for Planet X. Tombaugh took
photographs of the sky and examined differences
between two slides of the same sky by using a
machine called a blink comparator. The machine
rapidly shifted back and forth between views of
each of the two plates to create the illusion of
movement of any objects that had changed position
or appearance between the photographs. After
many years, he finally found an object shifting its
position—the elusive Planet X!
• On March 14, 1930, the name Pluto was
proposed by Venetia Burney, an 11-year-old
schoolgirl from Oxford, England. Interested
in classical mythology, she suggested the name
20
Pluto, after the god of the underworld. The
observatory liked the name because the new
planet’s sign would be PL—also the initials of
Percival Lowell.
• That same year, Walt Disney named his new
cartoon character (Mickey Mouse’s dog) Pluto.
Whether Walt named Pluto after the newly
discovered planet is still a mystery.
• In 1941, Glenn T. Seaborg named the newly
found element Plutonium after Pluto, in keeping
with the tradition of naming elements after newly
discovered planets. (Uranium is named after Uranus
and Neptunium is named after Neptune.)
• In 2005, Mike Brown from Caltech discovered Eris,
possibly the tenth planet, much larger than Pluto,
some 10 billion miles from the Sun (in the far end
of the Kuiper belt), which caused astrophysicists to
rethink the definition of a planet.
Background on Pluto
Before studying the planet/non-planet controversy,
students should research the following information to
become familiar with facts and figures about Pluto.
Pluto
• is about 6.5 billion km (4 billion mi.) from the Sun;
• is found in the Kuiper belt, an area of mixed
debris located just beyond Neptune;
• has a pinkish tint with large, dark areas;
• has a diameter of 2,414 km (1,500 mi.), which is
smaller than Earth’s Moon;
• has an orbital period equal to 248 Earth years,
with a highly elliptical orbit tipped at 17° that
crosses into Neptune’s path;
• has five known moons: Charon (the largest, with a
diameter just over half that of Pluto), Nix, Hydra,
Kerberos, and Styx;
• has a rocky, solid core with an icy surface, an
atmosphere of fog above the surface, and a
temperature estimated at -201°C (-330°F); and
• was once considered by some to be a “double
planet” because its center of mass between Pluto
and its moon, Charon, lies outside Pluto.
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
Why Pluto was reclassified as a dwarf
planet
The International Astronomical Union (IAU) determines the official names and classifications for all celestial bodies, but had not defined what characterized a
planet prior to August 24, 2006. Due to the discovery of
another celestial body, later named Eris, the IAU recognized the need to identify what defines a planet. After heated debates, the IAU agreed that a planet (1) orbits the Sun, (2) has enough mass to overcome forces
to reach hydrostatic equilibrium (nearly round) shape,
and (3) dominates the area around its orbit (IAU 2006).
Pluto met the first two requirements, but since it is not
massive enough to clear other objects away in its orbit,
Pluto did not meet the third criterion. The IAU termed
Pluto a “dwarf planet,” which is when the object fits the
first two criteria, but not the third.
It is interesting to note that the reclassification is
not considered a major change in scientific theory or
discovery, but rather a change in the rules with which
planets are classified (Robertson 2006). This situation
illustrates how science and scientific knowledge are
tentative and can be altered with new evidence or interpretations of evidence (Lederman 2007; NGSS Lead
States 2013). It also demonstrates science as a human
endeavor in which classification of our natural world
and interpretation of evidence can result in the coexistence of opposing, yet valid, points of view.
The New Horizons space mission
Launched in 2006 and traveling at 59,546 km (37,000
mi.) per hour for 1,200,571 km (746,000 mi.) a day, the
New Horizons spacecraft made its passing of Pluto in
July 2015. As the New Horizons spacecraft flies past
Pluto during the summer and fall months of 2015, it will
study Pluto’s atmosphere, surface features, structure,
and five moons. This is an extraordinary opportunity
for science teachers to design a unit of study around
Pluto and its reclassification to a dwarf planet. Readers
should also know that some of Clyde Tombaugh’s ashes are on the New Horizons spacecraft. Undoubtedly,
Clyde would have been very proud to fly by the planet
he discovered over 85 years ago.
Integrating scientific literacy and
argumentation into the Pluto controversy
The following lessons exemplify opportunities to engage middle level students in argumentation about
Pluto’s planethood. As an NGSS science and engineering practice, Engaging in Argument from Evidence
offers students an opportunity to support claims with
evidence as scientists do (NGSS Lead States 2013).
Students conduct research to investigate the history
behind the reclassification of Pluto, argue whether the
reclassification was appropriate, and reach a solution
that may result in different points of view. These lessons allow students to think critically about the importance of the NGSS crosscutting concepts of Patterns;
Scale, Proportion, and Quantity; Structure and Function; and Systems and System Models. The lessons
also incorporate the roles of classification, order, and
consistency in natural systems, which are an NGSS
connection to the nature of science (NGSS Lead States
2013). The lessons may take approximately two to four
class periods, but this is largely dependent on the inclass time allowed for research and the oral arguments
that occur during the unit.
Lesson strategy #1: Researching the
background on Pluto’s reclassification
Ask students to name objects in our solar system. On a
board that students can see, write down the objects students name, such as: the Sun, planets, moons, comets,
and asteroids. Prompt students to name the planets
and record what they know about Pluto. At this point,
some students may comment that Pluto is no longer a
planet. If not, provide a prompt about Pluto’s reclassification to initiate the discussion.
After stating that Pluto is no longer a planet, ask students about Pluto’s current classification and the reasons for the reclassification, while recording the comments for the class to see. After students have shared
their thoughts, let the class know that the reclassification of Pluto is still under contention in the scientific
community. Students will now investigate the story
behind this relatively recent change in space science.
Investigation
Divide students into groups of three or four and have
each group research the events that led to the reclassification of Pluto. Provide each group access to the
internet, books, articles, and other resources for their
research. Review with the class the ways to identify
websites as reputable and reliable sources of scientific
information. It may be a good idea to provide starting
points for students, such as the sources found in Figure 1. At the end of the unit, students will prepare an
oral presentation/argument to share the information
they find. This can include a PowerPoint presentation,
a poster, or a digital story.
As students examine the controversy, ensure that
they (a) match evidence, (b) include adequate amounts
of evidence, and (c) interpret the data appropriately.
S e p t e m b e r 2 0 15
21
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
FIGURE 1
Starting points for students
IAU
www.iau.org
www.iau.org/public/themes/pluto
NASA
www.nasa.gov
www.science.nasa.gov
www.nasa.gov/audience/forstudents/k-4/stories/what-is-pluto-k4.html
National Geographic
http://news.nationalgeographic.com/news/2006/08/060824-pluto-planet.html
http://kids.nationalgeographic.com/kids/stories/spacescience/pluto-planet
http://news.nationalgeographic.com/news/2011/08/110824-pluto-dwarf-planet-definitionnasa-iau-space-science
Johns Hopkins
University
http://jhuapl.edu
Additional video segments can be found on YouTube, PBS, and Apple TV.
In addition, make sure student claims and analysis of
data are consistent with current scientific knowledge
in a way that contributes to the class’s comprehension
of the topic at hand (Sampson, Enderle, and Grooms
2013). If needed, refocus the class on the evidence they
gathered and emphasize the importance of supporting
their claims with scientific evidence. This phase can
take as long as needed, but consider allocating a certain amount of time, such as 30 minutes.
Suggested accommodation: provide opportunities
for students to prepare their arguments in written form.
Also, allow English language learners (ELLs) to practice pronunciation and to focus on establishing a strong
argument by making clear connections between the
initial claim and the evidence (Miller, Baxter-Lauffer,
and Messina 2014). This is crucial, as ELLs have the
greatest difficulty making these links.
At the conclusion of the lesson, discuss students’
current views regarding Pluto’s reclassification. Poll
the class as to how many students changed their view
based on the evidence presented. Be sure to review
the major attributes that make up the current definition of a planet. Also, emphasize the importance of understanding crosscutting concepts such as Patterns;
Scale, Proportion, and Quantity; and Structure and
Function in this controversy.
Although Pluto is currently considered a dwarf
planet, lead a discussion with students about the tentativeness of science and the role of data interpretation and reinterpretation to foster their understanding
of the nature of science. Ask students to share other
examples that show how science is a human endeavor that reflects the culture in which is it embedded
22
(Lederman 2007). Remind students that, in science,
knowledge is not absolute, and competing ideas can
be endorsed within the scientific community.
Lesson strategy #2: The classroom as a
courtroom: Guiding a case study through
argumentation
According to Llewellyn (2014), “turning the classroom
into a courtroom can be an easy way to apply the skills
of argumentation in science. By preparing courtroom
trials on various historic and present-day opposing beliefs, teachers afford students opportunities to become
more proficient in argumentation while (1) providing
a sheltered environment in which to disagree and (2)
improving speaking and listening skills” (p. 53).
In this strategy, students are asked to take a side on
the full-fledged planet/dwarf planet controversy surrounding Pluto. Students state their position and provide supporting evidence. Then, in a courtroom-like setting, sides present their case to a “jury” of students with
one student (or the teacher) playing the role of a judge
presiding over the proceedings.
Let students know they will be engaged in a debate about whether Pluto should be reclassified as a
planet. Remind students that they must use evidence
to support their claims; this evidence can be from the
research gathered as a class or additional research the
groups conduct on the topic.
Have students prepare claims, evidence, and justifications in order to engage in argumentation. Strategically arrange students in groups of four for the initial
phase of this activity (finding evidence to support their
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
Connecting to the Next Generation Science Standards (NGSS Lead States 2013)
Standard
MS-ESS1: Earth’s Place in the Universe http://nextgenscience.org/msess1-earth-place-universe
Performance Expectation
The materials/lessons/activities outlined in this article are just one step toward reaching the performance
expectations listed below.
MS-ESS1-2. Develop and use a model to describe the role of gravity in the motions within the solar system.
MS-ESS1-3. Analyze and interpret data to determine scale properties of objects in our solar system.
Matching student task or question taken
directly from the activity
Dimension
Name or NGSS code/citation
Science and
Engineering Practice
Engaging in Argument from Evidence
Students engage in scientific argumentation
with evidence to support their view of
whether Pluto is correctly classified as a
dwarf planet or should be reclassified as a
planet in our solar system.
Disciplinary Core
Idea
ESS1.B: Earth and the Solar System
Students research Pluto’s place in the solar
system, orbital pattern around the Sun,
orbital pattern with Charon, and messiness of
orbital path.
Crosscutting
Concepts
Patterns
Scale, Proportion, and Quantity
Systems and System Models
• The solar system consists of the sun
and a collection of objects, including
planets, their moons, and asteroids
that are held in orbit around the Sun
by its gravitational pull on them.
claim). Half of the groups will argue in favor of Pluto
being reinstated as a planet, while the other half will
argue that Pluto should remain a dwarf planet. Balance
the composition of the groups to maximize participation for all students. During the next phase of the activity, students can engage in argumentation by pairing
up with a group presenting the opposite view (total of
eight students per group).
Regardless of the strategy, nonplanet advocates may
state the IAU’s definition of a planet and conclude that
Pluto is a Kuiper belt object, an oddball, or a misfit,
thus placing Pluto in a dwarf planet category. Additional points may include:
Students examine the role of patterns and
scale when classifying space objects, such
as Pluto, in our solar system.
orbits the Sun, has enough mass to overcome
forces to be spherical in shape, and dominates the
area around its orbit.
•
The IAU defined a dwarf planet as an object
that fits the same criteria as a planet, except it
does not dominate the area around its orbit. The
patterns in which objects in our solar system
revolve around the Sun, as well as the orbit of the
object, are critical in determining how objects in
the solar system are classified.
•
The IAU held a meeting on August 24, 2006, and
voted to reclassify Pluto as a dwarf planet because
its orbital pattern is highly elliptical and Pluto is
actually closer to the Sun than Neptune at times.
•
Pluto and its largest moon, Charon, orbit a
common center of gravity instead of Charon
orbiting Pluto, as Earth’s Moon orbits Earth.
•
Pluto does not dominate the area around its orbit,
• The IAU is the international organization that
determines the official names for all celestial bodies.
•
The IAU began to discuss a definition of a planet
after the discovery of Eris.
•
The IAU decided a planet is a space object that
S e p t e m b e r 2 0 15
23
NASA-JHUAPL-SWRI
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
This close-up image of a region near Pluto’s equator reveals a giant surprise: a range of youthful mountains.
and its orbit is littered with space matter.
•
In recent years, six new dwarf planets (or TransNeptunian Objects) have been discovered in
Pluto’s neighborhood of the Kuiper belt, some
five to six billion miles from the Sun.
On the other hand, Pluto-philes may state that size
doesn’t matter—despite the difference in their relative
sizes, Chihuahuas and St. Bernards are both dogs. In
spite of the IAU’s revised definition, there is a strong
emotional sentiment for Pluto remaining a planet, especially among children, and that reclassification is just
plain wrong. If you ask any school-age child to state
the order of the planets he or she would probably recite the mnemonic, “My Very Excellent Mother Just
Served Us Nine Pizzas.” Is there no place for romanticism in science anymore?
Understanding argumentation
Teachers should remind students that scientific argumentation is something that scientists do to attempt to
reach consensus about a phenomenon. Scientific argu-
24
mentation involves scientists trying to persuade others
that their evidence is valid, while in turn, other scientists challenge, assess, rebut, and reinterpret evidencebased claims. Llewellyn (2014) and Sampson, Enderle,
and Grooms (2013) provide frameworks for scientific
argumentation, describing the connection between
claims and evidence. According to these frameworks,
students should present or formulate a claim (conclusion, description, or explanation of the research question) that is supported by evidence (data, analysis of
data, and interpretation of data). An explanation of the
evidence also should be provided to spell out the concepts or ideas that informed the analysis and interpretation of the data.
Conclusion
According to the NGSS, one of the fundamental and
overarching goals of middle level science education is
to help students understand that science is a human
endeavor whereby attempts are made to explain phenomena and occurrences in the natural world based
on empirical evidence. The Pluto controversy exemplifies how scientists use various equipment and models
THE CONTROVERSY OVER PLUTO: PLANET OR ASTRONOMIC ODDBALL?
to explore the boundaries of science knowledge. It is
the quintessential case study for learning the nature of
science as well as the expression of ideas through argumentation. By studying the Pluto dispute, students
come to appreciate the work of scientists and how
science advances based on the discussions and “arguments” among scientists. More specifically to the Pluto
controversy, the nature of science highlights
•
how scientific explanations are subject to revision
and improvement in light of new evidence,
•
how the certainty and durability of science
findings varies, and
•
how science findings are frequently revised or
reinterpreted based on new evidence (NGSS Lead
States 2013).
Although science usually is based on classification
and definition, there appears to be no clear, generally
accepted definition of a planet among nonscientists.
With that lack of consensus, the debate will continue.
In the end, students learn how scientists debate issues
with evidence and alter our understanding of the natural world as well as the universe.
So whether Mrs. Seavers’s students think there are
eight, nine, 14, or more planets in our solar system, the
voyage of the New Horizons spacecraft to Pluto is certain to resurrect new debate on the demise of Pluto’s
planetary status. A fertile environment to discuss this
is the middle level science classroom. ■
References
Clary, R., and J. Wandersee. 2013. Arguing history:
Teaching historical scientific controversies to engage
students in discourse and the nature of science. The
Science Teacher 80 (5): 39–43.
IAU. 2006. Resolution B5: Definition of a planet in
the solar system. www.iau.org/static/resolutions/
Resolution_GA26-5-6.pdf.
Inman, M. 2006. Pluto not a planet, astronomers
rule. National Geographic News. http://news.
nationalgeographic.com/news/2006/08/060824-plutoplanet.html.
Lederman, N.G. 2007. Nature of science: Past, present,
and future. In Handbook of research on science
education, eds. S.K. Abell and N.G. Lederman, 831–
79. Mahwah, NJ: Lawrence Erlbaum Associates.
Llewellyn, D. 2014. Inquire within: Implementing inquiryand argument-based science standards in grades 3–8.
3rd ed. Thousand Oaks, CA: Corwin Press.
Miller, E., H. Baxter-Lauffer, and P. Messina. 2014. NGSS
for English language learners: From theory to planning
to practice. Science and Children 51 (5): 55–59.
National Governors Association Center for Best Practices
and Council of Chief State School Officers (NGAC
and CCSSO). 2010. Common core state standards.
Washington, DC: NGAC and CCSSO.
NGSS Lead States. 2013. Next Generation Science
Standards: For states, by states. Washington, DC:
National Academies Press. www.nextgenscience.org/
next-generation-science-standards.
Sampson, V., P. Enderle, and J. Grooms. 2013.
Argumentation in science education: Helping students
understand the nature of scientific argumentation so
they can meet the new science standards. The Science
Teacher 80 (5): 30–33.
Resources
Brown, M. 2010. How I killed Pluto and why it had it
coming. New York: Spiegel & Grau.
Chang, K. New York Times. 2001. Pluto’s Not a Planet?
Only in New York. January 22. www.nytimes.
com/2001/01/22/nyregion/pluto-s-not-a-planet-only-innew-york.html.
Freedman, D. 1998. When is a planet not a planet?
Arguments for and against demoting Pluto. www.
theatlantic.com/magazine/archive/1998/02/when-is-aplanet-not-a-planet/305185.
Riddle, B. 2015. Far out! Exploring the outer reaches of
our solar system, Science Scope 38 (9): 92–95.
The Daily Show with Jon Stewart (Neil deGrasse Tyson)—
http://thedailyshow.cc.com/videos/twq7rb/neildegrasse-tyson
Tyson, N. deGrasse. 2009. The Pluto files: The rise and
the fall of America’s favorite planet. New York: Norton &
Company.
Weintraub, D. 2007. Is Pluto a planet? A historical journey
through the solar system. Princeton, NJ: Princeton
University Press.
WGBH. 2010. The Pluto files: The rise and fall of America’s
favorite planet (video). Boston: WGBH. www.pbs.org/
wgbh/nova/space/pluto-files.html.
Douglas Llewellyn (dllewellyn@sjfc.edu) is an
author, consultant, and part-time professor at
St. John Fisher College in Rochester, New York.
Sissy S. Wong (sissywong@uh.edu) is an assistant professor of science education at the University of Houston in Houston, Texas. Irasema
Ortega (iortega2@uaa.alaska.edu) is an assistant
professor of science education at the University
of Alaska in Anchorage, Alaska.
S e p t e m b e r 2 0 15
View publication stats
25