Download Taylor Samantha Taylor Professor Gennifer Marconette English 102

Taylor 1
Samantha Taylor
Professor Gennifer Marconette
English 102
12 July 2016
Research Essay
Dynamic Pluto
Nearly one year ago today, the New Horizons Spacecraft completed a mission that has
been recorded in history as a triumph of engineering and the laws of physics. The probe sailed by
Pluto during July 2015 after its three-billion-mile journey over the course of nine years. A wide
array of new information was gathered during this mission on one of the most distant objects in
our solar system. Although many detailed images were captured by the probe, the age old
question still exists; Is Pluto a planet? The debate on whether or not Pluto should be considered a
planet is ongoing, and both sides consist of persuasive facts and theories. This essay will present
scientific and historic information from both sides of the debate.
During the late 1800s, an American Astronomer named Percival Lowell predicted the
existence of Pluto while searching for another unknown object deemed Planet-X. Lowell
observed delineating orbits of Uranus and Neptune and determined that Planet-X must have been
responsible (“Pluto: In Depth”). Due to such observations, he initiated the search for Planet-X,
which instead led to the discovery of Pluto. Unfortunately, Lowell died before Pluto’s official
discovery was made in 1930 and Planet X was never found. However, Lowell is responsible for
Taylor 2
opening the observatory, now known as the Lowell Observatory, that made the discovery after
his death.
A young American astronomer, Clyde Tombaugh, was hired as an observing assistant at
the Lowell Observatory in the late 1920s. Tombaugh carried out Lowell’s work to discover
Planet-X, and during the process made the official discovery of Pluto in 1930:
Within a year, after spending numerous nights at the telescope exposing photographic
plates and months tediously scanning them for signs of a planet, Tombaugh saw what he
was looking for. At around 4pm on the afternoon of 18 February 1930 Tombaugh began
comparing two plates taken in January that year showing a region in the constellation of
Gemini. As he flicked from one plate to the other, trying to see if something moved
slightly between the two (the tell-tale sign of the planet he was hunting), he spotted
something. In one part of the frame a small object flitted a few millimeters as he switched
between the two plates. Tombaugh had found his new planet (“Pluto and the Developing
Landscape of Our Solar System”).
As a result, textbooks were swiftly updated and Pluto held a firm position as the ninth planet in
our solar system for 76 years.
Not much was known about Pluto at the time of its discovery, aside from the fact that it
lived on the edge of our solar system. It was immediately deemed as the ninth planet simply due
to its existence past the eighth planet, Neptune. It was not until the late 1900s and early 2000s
that a face was put to the name. Due to Pluto’s 248-eplitical-orbit around the sun, scientists did
not have an opportunity to study this cold, distant world until 1989.
Taylor 3
The year of 1989 offered scientists and astronomers a rare window to observe Pluto
because it was closer to the sun than ever before within the last 250 years. The surface of Pluto
drastically changes depending on its orbit and how close it is from the sun:
Since its orbit is so elliptical, when Pluto is close to the sun, its surface ices sublimate,
changing directly from solid to a gas, and rise and temporarily form a thin atmosphere.
Pluto's low gravity (about six percent of Earth's) causes the atmosphere to be much more
extended in altitude than our planet's atmosphere. Pluto becomes much colder during the
part of each orbit when it is traveling far away from the sun. During this time, the bulk of
the planet's atmosphere is thought to freeze and fall as snow to the surface (“Pluto: In
Depth”).
Well after Pluto claimed its spot as the ninth planet in our solar system in 1930, the
controversy legitimately started in 1992 when two astronomers discovered the Kuiper Belt:
The Kuiper Belt is a disc-shaped region beyond Neptune that extends from about 30 to 55
astronomical units (compared to Earth which is one astronomical unit, or AU, from the
sun). This distant region is probably populated with hundreds of thousands of icy bodies
larger than 100 km (62 miles) across and an estimated trillion or more comets (“Kuiper
Belt: In Depth”).
Dave Jewitt and Jane Luu were the pair of astronomers that did not believe that the solar system
was empty beyond Pluto and devoted their careers to this theory. They began their search in
1987 and eventually discovered a new object even more distant than Pluto in 1992. This object
was cataloged as “1992 QB1” and became as the first known Kuiper Belt Object (KBO).
Taylor 4
“Confirmation of the first KBO invigorated the existing debate. And in 2000, the Hayden
Planetarium in New York became a focus for controversy when it unveiled an exhibit featuring
only eight planets. The planetarium's director Neil deGrasse Tyson would later become a vocal
figure in public discussions of Pluto's status” (Rincon). The later discoveries of the following
KBOs pushed the issue to a tipping point: Quaoar (2002), Sedna (2003) and Eris (2005). The
detection of a planet similar to the size of Pluto and orbiting the sun, Eris, required scientists to
determine if it should be considered as the tenth planet in our solar system. In light of these
discoveries, the International Astronomical Union (IAU) held the Prague General Assembly in
2006 to address the planetary status of Pluto and other KBOs.
During August of 2006, the IAU set up a committee to create a proposal for a definition
of what constitutes a planet. On the contrary, the committee also drafted a proposal to increase
the number of planets in our solar system from nine to twelve to include Pluto and its moon
Charon, Eris, and one other KBO. Both proposals were presented for voting at the Prague
General Assembly later that month. 2,700 notable scientists were invited to a ten-day conference
to discuss both proposals and conduct a vote during the general assembly on the last day, August
24th. Unfortunately, only 10% of the 2,700 that attended the conference were present for voting
on the last day.
The proposal to increase the number of planets in our solar system did not pass, with
opposition from the majority. “Commenting at the time, the IAU's president of planetary systems
science Prof Iwan Williams said: ‘By the end of the decade, we would have had 100 planets, and
I think people would have said 'my goodness, what a mess they made back in 2006’” (Rincon).
Members of the assembly agreed to implement a new classification for larger KBOs, such as
Pluto and Eris, called dwarf planets.
Taylor 5
The discussions of the general assembly resulted in the establishment of a new criteria for
identification of a planet; a planet is a celestial body that is in orbit around the sun, has sufficient
mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit. Pluto meets
the first two criteria but does not meet the last. “Clearing the neighborhood” means that an object
has obtained gravitational dominance by absorbing or expelling other objects in its orbit. Pluto
fails to meet this criterion because it shares and orbital neighborhood with other KBOs including
Eris. This factor was never taken into consideration prior to the discovery of the first KBO in
1992, which is why Pluto held its designation as a planet without question for 76 years.
Now, back to dwarf planets. Members of the general assembly established the new
classification of KBOs called dwarf planets to meet the needs of larger objects like Pluto,
Charon, and Eris. Dwarf planets are similar to planets as they are both round or nearly round, and
they both travel through space via an orbit around the sun. The defining factor is that a dwarf
planet’s orbit around the sun may contain other objects, where a planet cleared its orbit of objects
during collisions that occurred billions of years ago while the solar system was still in formation.
Since the establishment of this definition in 2006, over five more dwarf plants have been
discovered and the count is continuing to increase. Pluto’s largest moon, Charon, has also be
designated as a dwarf planet due to its size, and the two objects have become known as a doubledwarf planet system.
The dwarf planets that exist in the Kuiper Belt have been classified as a special type of
dwarf planets called trans-Neptunian objects. To make matters more complicated and add to the
diversity of Pluto’s planetary status, the dwarf planet has also been designated as a plutoid. A
plutoid is a special classification of KBO dwarf planet assigned by the IAU, which is an object in
Taylor 6
orbit beyond Neptune that is massive and round, or nearly round, in shape. A plutoid is also
commonly referred to as an icy dwarf because all trans-Neptunian objects are located within the
frigid Kuiper Belt. Some astronomers agreed that Pluto deserved a more unique classification,
such as a plutoid, as it had held the status of planet for 76 years and arguably still deserves
recognition.
Although the decision about Pluto’s planetary status was established at the IAU General
assembly in 2006, many experts are still up in arms about it. Some question the third criterion for
a planet recognized by the IAU, specifically the part about clearing the orbit around its
neighborhood. The argument presented in opposition is that Earth shares its orbit with more than
12,000 asteroids, yet, it is still considered to be a planet. Thus, some experts argue that planets
like Earth, Jupiter, and Saturn fail to meet the definition established by the IAU. “Speaking just
after the vote, Prof Alan Stern, chief scientist for the New Horizons mission, called the outcome
‘as an awful decision’ and described the new definition as ‘internally inconsistent’” (Rice). Other
experts are in disagreement due to the fact that only 10% of the 2,700 attending scientists
participated in the vote on the last day of the general assembly. Findings show that many of the
attendees did not attend the assembly the day of the vote so they could prepare for travel
arrangements out of Prague. Some experts have determined the final resolution made by the IAU
as not creditable due to the lack of attendee participation during the voting process.
Since 2006, the debate has continued via public talks, social media, on television, and in
printed material. On September 15th, 2015, a vote on the issue was conducted by three members
of the IAU’s planet definition committee, resulting in two of three in agreement that Pluto should
be classified as a planet. Due to the exhibit of eight planets at the Hayden Planetarium in 2000,
Neil deGrasse Tyson has been dubbed as one of the men who killed Pluto. However, he refuses
Taylor 7
to participate in further debates on the subject stating that, “I don’t have opinions that I require
other people to have.”
So, is Pluto a planet, dwarf planet, KBO, trans-Neptunian object, plutoid or icy dwarf?
The simple answer is yes to all five classifications. Pluto proves to be dynamic due to its
complicated history and has met, or still meets, the established criteria for all five possibilities.
“Harvard science historian Owen Gingerich, who chairs the IAU planet definition committee,
argued at a forum last month that ‘a planet is a culturally defined word that changes over time,’
and that Pluto is a planet” (Rice). The resolution of the IAU general assembly in 2006 remains in
place but is subject to change as our view of the Universe constantly evolves from discoveries,
observations, and scientific theories. At this time, no requests have been made for the IAU to
revisit the issue concerning the planetary status of Pluto.
Taylor 8
Works Cited
“Kuiper Belt: In Depth.” NASA.gov. NASA, Web. 8 Jul 2016.
“"Pluto and the Developing Landscape of Our Solar System." IAU.org. International
Astronomical Union, Web. 7 Jul 2016.
"Pluto-In Depth." NASA.gov. NASA, Web. 7 Jul 2016.
Rice, Doyle. "Wait, what? Pluto is a planet again?" USATODAY.com. USA Today, 2 Oct 2014.
Web. 7 Jul 2016.
Rincon, Paul. "Why is Pluto no longer a planet?" BBC.com. BBC News, 13 Jul 2015. Web. 7
Jul 2016.
Taylor 9
Works Consulted
"Clyde Tombaugh Discoverer of Planet Pluto." Academy of Acheivement.org. Academy of
Achievement, 1 April 2015. Web. 8 Jul 2016.
"Dwarf Planets: In Depth." NASA.gov. NASA, Web. 8 Jul 2016.
“Percival Lowell American Astronomer.” Britannica.gov. Encyclopedia Britannica, Web. 8 Jul
2016.
Wagstaff, Keith. “Neil deGrasse Tyson: New Horizons Mission to Pluto Is a Triumph.”
NBCNEWS.com. NBC News, 14 July 2015. Web. 13 Jul 2016.