Should Pluto be a Planet Prompt



For many decades, science and astronomy texts had considered Pluto to be a planet. Yet in 2006, a meeting of scientist cast Pluto out as a planet, naming it a “planetoid.”  Some saw this as altogether unjust.  This exercise is to argue that Pluto should be returned to its former status as a planet despite the definition of planet and planetoid.  In your argument, consider these things:


1.      Pluto and its moon Charon are unique as a “doublet-pair “, both being somewhat related in size.

2.      Millions of textbooks, scientific articles and printed matter exist citing Pluto as a planet.

3.      Pluto has an endearing cartoon/comic name-sake, fondly loved by children.

4.      Pluto was the first so-called planetoid to be named a planet, and, as such, its uniqueness should preserve its honor as being a planet.

5.      Perhaps, because of its history, Pluto should be an exception to the classification of planetoids.  Rather than demoting it to planetoid status, perhaps, a new unique classification should be given to Pluto.  If so, what would  you call Pluto?  - A planetary doublet, a classical planet since it existed as such in classical astronomy texts, an original planet because it was one of the original  “9” planets identified in planetary “mnemonics” memorized by school children  (in the same fashion that NASA distinguishes the original seven Mercury astronauts from the scores who were to follow), etc.                                                                        


Your assignment is to craft a 300 work, single page essay arguing for Pluto’s reinstatement as one of the nine planets of the Solar System. 


Solar System (2006)



(Bevan M. French and Stephen P. Maran, eds., "A Meeting with the Universe," NASA EP-177, U.S. Government Printing Office, 1981.)

*The previous card is an image of Pluto and its moon Charon taken by the U.S. Naval Observatory.

* Pluto is a planetary oddball, a strange world that has baffled scientists ever since it was discovered in 1930. It is not the large gas giant that one might expect to find in the outer reaches of the solar system. Instead, it is a small world, much smaller than the Earth, and in fact roughly as large as our Moon. It is probably composed of a mixture of rock and ice. It even has been suggested that Pluto is not a genuine planet, but simply a moon that somehow escaped from Neptune.

* Pluto was classified as the farthest known planet from the Sun, its mean distance almost 6 billion kilometers (almost 4 billion miles) out. It takes 248 years for Pluto to complete one orbit around the Sun, but the orbit is so elongated that it actually spends about 20 years of this time inside the orbit of Neptune. (In fact, Pluto is at times inside Neptune's orbit, and was until 1999, so that Neptune was temporarily the furthest planet from the Sun.)

* Despite Pluto's distance and the extreme difficulty of observing it, our view of the faraway dwarf planet has changed greatly in the last few years. As we have looked more carefully, Pluto has become an even smaller and brighter object than we thought it was.

* It seems to have a bright layer of frozen methane ("marsh gas," chemically CH4) on its surface. Even more surprising, reexamination of old photographs revealed that Pluto is not alone; it has a moon. Pluto seems to be about 3,000 to 3,500 kilometers (1,900 to 2,200 miles) in diameter. Pluto's moon, Charon, is large by comparison, about 1,200 to 1,500 kilometers (750 to 930 miles) in diameter.

* Pluto will hold its secrets for a long time yet. It is simply too far away for our current spacecraft to reach it in a reasonable length of time. It will be many years before any machines or humans see Pluto up close, dimly lit by a Sun so distant that it seems like just a rather bright star in the blackness of space.

* Pluto is no longer considered the last planet by virtue of the new (August 2006) definition of a planet. Planets must meet these three criteria for any celestial body to be called a planet. It must: orbit the sun; have enough mass and ''self-gravity'' to sustain a nearly round shape; and have ''cleared the neighbourhood around its orbit,'' establishing an independent path as it circles the sun. Henceforth Pluto is deemed a "dwarf planet." Tiny, mysterious Pluto is so far from the Sun that it appears only as a tiny speck of light that moves slowly against the background of the fixed stars. So inconspicuous that it was not discovered until 1930, Pluto, as a dwarf planet, is not a gas giant planet like all the others in the outer solar system. Instead it is a small, rocky world about the size of Earth's Moon. Recent (1981) of old photographs, combined with more recent observations, indicate that Pluto itself has a moon.

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