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Tuesday, April 08, 2008


This paper was done in MLA format and was relatively short for a research paper. It is the last paper for this class! Sources are included. Most of you know that Pluto is a kind of obsession with me lately! If it's one of yours too and you have a few minutes you might enjoy this! Who knows, you may even learn something new.


Composition Assigment #7

Abstract: A brief history of the former planet Pluto and explanation of why it is no longer considered one. An examination into the events surrounding the decision to remove it by the International Astronomical Union and the efforts going on to bring it back by those who disagree.


Pluto was discovered seventy-six years ago at a time when astronomers believed something was wrong with the orbits of Uranus and Neptune. These two gas giants seemed to not go around the sun as circularly as they should, which meant that another planet had to be out there disrupting their orbits. To find the troublemaker, twenty-four year-old Clyde Tombaugh made a careful survey of the sky from the Lowell Observatory in Arizona. On January 23, 1930, he spotted Pluto, a dim speck moving among the stars. (Phillips) It was quickly hailed as the ninth planet from the Sun. However, something didn’t add up, Pluto was to small to disturb the orbits of mighty Uranus and Neptune, still, it was years later before astronomers realized there was nothing wrong with their orbits. It was all a big mistake, but a lucky one for Tombaugh. Pluto became the First planet to be discovered by an American so, as is imaginable, patriotic feelings ran high in America – which helped to instate Pluto into the Solar System as a planet even faster. (Phillips)

Tombaugh considered many names for the new planet. His favorite, Pluto, was suggested by eleven year-old Venetia Burney of Oxford, England. Although many people believe that the planet was named after Mickey Mouse’s dog, which also debuted in 1930, Venetia denies this, and today it is now accepted that the dog was named after the planet - rather than the other way around. (News)

Pluto has many unique qualities, first of all, it is six times smaller than the Earth, and even smaller than seven of the solar system’s moons: the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton. Secondly, Pluto has an odd orbit. While most planets go around the sun in near circles, Pluto’s orbit looks more like that of an egg. It actually crosses inside the orbit of Neptune, making Pluto the 8th planet instead of the 9th. (Phillips) Thirdly, Pluto orbits the sun at 2.9 miles per second, or 10,140 m.p.h., the slowest of all the planets. It takes Pluto 248 years to complete its orbit. (History) However, despite the oddities of its size and orbit, Pluto’s planethood was never seriously questioned until 1992. That’s when astronomers starting finding other things in space. It turns out that Pluto’s neighborhood is cluttered with icy bodies about the size of asteroids. They orbit the Sun in a busy belt, a bit like the asteroid belt, all beyond the orbit of Neptune. Back in 1951, the great astronomer Gerard Kuiper predicted such a belt to explain where certain comets came from, so today it bears his name – the Kuiper Belt. The discovery of the Kuiper Belt, with Pluto inside it, troubled some astronomers. They wondered of Pluto could be considered a planet or just another Kuiper Belt Object. Other astronomers insisted that Pluto was both – a planet and a KBO. (Phillips) So, the debate began.

The real trouble started in 2005 when Caltech astronomer Mike Brown and colleagues found something in the Kuiper Belt even lager than Pluto. Its name is 2003 UB313 or as Brown calls it, Xena. If Pluto is a planet, they reasoned, then Xena, being larger than Pluto, must be a planet as well. That sounds perfectly reasonable, except for one thing; there could be dozens of worlds larger than Pluto hiding in dark recesses of the Kuiper Belt. Are they all planets? Does the Solar System really need dozens of planets? Some astronomers said, “Why not?” The more the merrier. With each new discovery, the Solar System becomes a livelier place, with new planets to chart and study. What better way to rouse the interest of young scientists and explorers? Other astronomers disagreed. They felt that mixing KBOs with real planets would be unscientific and confusing – like mixing apples and oranges. (Phillips)

To answer the question once and for all, the International Astronomical Union (IAU) formed a “Planet Definition Committee” consisting of historians, science writers, and professional astronomers. Their job was to craft an official definition of a planet that all astronomers could agree on and use. The committee met, argued and debated, and finally settled on a definition, which they presented to the IAU General Assembly on August 16, 2006. The definition was, “A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equililibrium shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.” (Iau) The translation is this being that if it is round and it orbits the Sun, then it’s a planet. If this simple definition had been accepted, then Pluto would have been a planet, as would Ceres, a gain asteroid the size of Texas, and Xena. The total number of planets in the Solar System would have been twelve. Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Xena, and Charon, which is a double planet. However, it was rejected. Astronomers at the General Assembly voted against it. Still, no one wanted to end the meeting without figuring out what a planet was. So the committee continues their debate for another six days. On august 24, 2006, a modified definition was proposed. “A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, and (c) has cleared the neighborhood around its orbit.” (Iau) What this means is that to be a planet, a world must have enough mass and gravity to gather itself into a ball; it must orbit the sun; and it must reign supreme in its own orbit, having “cleared the neighborhood” of other competing bodies. This definition was approved and, and just as simple, Pluto was no longer a planet. According to the IAU, the Solar System now has eight and only eight planets. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto has not “cleared the neighborhood around its orbit” A planet does this by using gravity to gobble up or fling aside competing bodies. Pluto’s gravity is to weak to clear out its part of the Kuiper Belt. The neighborhood is a mess and thus, Pluto is not a planet. Unfortunately though, the committee failed to accomplish the main goal of why they were formed, to end the debate over Pluto. In contrast now, more than ever, the debate rages on.

Many people, including many astronomers and other scientists, refused to accept the IAU’s decision. Their argument is this - first of all, the IAU’s definition of planet is not entirely self-consistent. Consider the following: Pluto itself crosses the orbit of Neptune, which means that Neptune has failed to clear its own neighborhood. Is Neptune, therefore, not a planet? In fact, taken to extremes, this logic would add up to zero planets, because no planet has completely cleared its own neighborhood of asteroids and other debris. Another point of this side is that astronomers aren’t the only one’s with an interest in this. The word “planet” is thousands of years old. People use the word on a daily basis and know what it means. It’s plain English. On the other hand, the IAU has been around for less than a century. It was founded in 1919 and now, in 2006 has a membership of about 9,000. On a startling note, less than four percent of the IAU’s members actually participated in the vote to demote Pluto. Perhaps a larger and more varied group of people should be allowed to decide. (Phillips)

The subject of Pluto being a planet has reached many people outside of the Astronomic Society and those affiliated with it. A fifth-grade teacher named Pidge Wingert and her students in Albuquerque, New Mexico say, “We think that the decision shouldn’t be left to the public but decided by the scientists who have studied the planets for years. We, as a class, disagree amongst ourselves about Pluto being a planet; we are divided 50-50.” This is an interesting view coming from 5th graders. Dr. Paul Richardson, a family doctor and amateur astronomer puts his feelings a bit more strongly, “The arguments of the IAU are irrefutable. Pluto is a big member of a group of many objects, and should never have been classified as a planet – although the reasons it was are fully understandable within their time. If school kids want a planet to call their own, they should adopt Mercury—much more exciting than sluggish Pluto from which the Sun looks like a bright star.” On the other side of the fence comes Professor Paul Rybski from the University of Wisconsin, “I favor the original IAU two-part definition of planet: roundness and Sun-orbiting.

Yes, it lets in Ceres and probably Pallas as well as Pluto and Xena…it adds new worlds to explore to our Solar System and could substantially inspire young people to study astronomy. Reducing the number of planets in the Solar System would be substantially less inspiring.” (Pluto)So what’s being done? Currently there is a petition set up with a goal of one million votes. This is the easiest and fastest way for people to get involved in this debate. As of now the results for this petition are, 19,521 for Pluto being a planet and 4,489 against Pluto being a planet. (Pluto) These numbers make it obvious that there is a long way to go for those who wish to bring Pluto back as a planet. Pluto has been removed from all new products with the Solar System theme. All planet lunchboxes, t-shirts, toys, and books no longer include Pluto. Still, one has to face the fact that it has been almost two years and the confusion amongst the general public and dismay amongst many astronomers persists. If there is one thing that the controversy over Pluto has taught us, it is that you cannot simply erase 70 years of accepted history from people’s minds.

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