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Dwarf Planet : Pluto

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How astronomers have come to conclude Pluto as a star and not a planet.

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MediaWiki. “Kuiper Belt.” Wikipedia, the free encyclopedia. 23 Oct 2009. http://en.wikipedia.org/wiki/Kuiper_belt.

Doosan encyclopedia Encyber. “William Clyde Tombaugh.” Naver 백과사전. http://100.naver.com/100.nhn?docid=155692. 1906.2.4~1997.1.17, American astronomer. P. Lowell's estimate based on data outside the orbit of Neptune and Pluto, planet of the expedition was found. That was only discovered several asteroids and galaxies outside against the under studied.

IAU. “Internatonal Astronomical Union.” IAU. http://www.iau.org. The International Astronomical Union (IAU) was founded in 1919. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. Its individual members - structured in Divisions, Commissions, Working groups and Program Groups - are professional astronomers from all over the world, at the Ph.D. level and beyond, and active in professional research and education in astronomy. Besides, the IAU collaborates with various organizations all over the world. The IAU has 10144 Individual Members in 90 countries worldwide. Of those 68 are National Members.

MediaWiki. “Eris (dwarf planet).” Wikipedia, the free encyclopedia. 23 Oct 2009. http://en.wikipedia.org/wiki/Eris_(dwarf_planet).

Our solar system is made of many celestial bodies. It consists of the Sun, eight planets, which are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune according to the distance from the Sun (the closest one �rst), and other celestials such as meteors, asteroids, comets, and etc. Our solar system is located in a galaxy called the Milky Way. �ere are three types of galaxies which are spiral, elliptical, and irregular. Our Milky Way is a spiral galaxy which is young and bright galaxy shaped like a whipping cream of a co�ee. An elliptical galaxy is an elliptical shaped galaxy that light and stars are evenly spread out. An irregular galaxy is the oldest galaxy which stars are fading and distributed at the center of the galaxy. �e eight planets in our solar system are divided into two systems, the inner system and the outer system. �e two systems are divided by the asteroid belt. �e inner system contains �rst four planets which are Mercury, Venus, Earth, and Mars. Between Mars and Jupiter, there is an asteroid belt. �e outer system is made of later four planets which are Jupiter, Saturn, Uranus, Neptune and the Kuiper belt 1. �e four planets are formed with gas and have no solid crust. �ese unique circumstances of the outer solar system make it impossible for us to land any spacecra� or a lander to investigate the planets. �e Kuiper belt is similar to the asteroid belt but as 20 times wide and 20~200 times massive. While asteroid belt is mainly composed of rock and metal, the Kuiper belt is mainly �lled with at least four dwarf planets and frozen volatiles such as methane, ammonia, and water. One of the four dwarf planets in the belt is Pluto. Pluto was discovered on Tuesday, 18, 1930 by Clyde William Tombaugh 2 by using 13-inch astrograph. It has a moon called Charon which has similar mass and size as Pluto. Pluto used to be the 9th planet from the sun in our solar system but the International Astro-nomical Union (IAU 3) took away its status in 2006. A�er Pluto’s banishment, the Interna-tional Astronomical Union created conditions to be called as a planet. Pluto was expelled because it didn’t satisfy some of the conditions. Some scientists and astronomers strongly objected to banishment of Pluto but I agree with IAU that Pluto should leave the 9 planets and join the dwarf planets in the Kuiper belt.

Pluto used to be the smallest planet and now the second largest dwarf planet a�er Eris 4 (the biggest known dwarf planet) in our solar system. Pluto’s surface area is 0.033 of the Earth’s, mass is 0.178 of our Moon’s and the volume is 0.0059 of the Earth’s. Pluto is composed of more than 98% nitrogen ice with a hint of methane and carbon monoxide. �is thick nitrogen atmo

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Korea Britannica Corp. “Hubble Space Telescope.” Daum 백과사전. http://enc.daum.net/dic100/contents.do?query1=b25h0164a.

NASA. “NASA.” NASA o�cial. 27 Oct 2009. http://www.nasa.gov/.NASA's mission is to pioneer the future in space exploration, scienti�c discovery and aeronautics research.

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sphere and current limits on telescopes make it impossible to take direct photographs of Pluto’s surface. Pluto’s atmosphere is made of nitrogen, methane, and carbon monoxide which derived from the ices on its surface. As Pluto gets further away from the Sun, its atmo-sphere freezes and falls back to the surface. On the other hand, as Pluto gets closer to the Sun, the ices on the surface sublimates into gas. Pluto has three natural satellites. �ey are known as Charon, and two smaller moons Nix, and Hydra. �e Plutonian moons are unusually close to the main celestial body in that location, as the discoverers say “Highly compact, and largely empty”. Pluto’s biggest Charon was one of the reasons that made Pluto downfall to dwarf planet. Because Charon has similar mass and size as Pluto, scientists sometimes call them ‘double dwarf planet’. Astronomers found out that Charon and Pluto always show the same faces to each other, which means Pluto revolves by itself at the same speed rate as Charon’s orbital speed. �e other two moons of Pluto was found during while Astronomers were work-ing with Hubble Space Telescope 5. �ey were o�cially named as Nix, and Hydra on June 21st, 2006 by IAU. �ese small moons orbit around Pluto at about two and three times distance of Charon. Nix and Hydra are even less known than Pluto and Charon. Sometimes Hydra shines brighter than Nix. �is may suggest that Hydra is brighter than Nix or the particular surface on Hydra makes it look brighter. Discovery of these two natural satellites made it possible for Pluto to have various ring systems. But there are no ring systems observed at present. Astrono-mers are making a prediction that the ring might be tenuous like Jupiter’s ring or tightly con�ned to less than 1,000km width which can’t be observed by the Hubble Space Telescope. �e �rst exploration on Pluto could be made with a �yby called Voyager 1. But the controllers chose to �yby near Saturn’s moon Titan which makes it impossible to �yby Pluto. �e second �yby named Voyager 2 never got far enough to observe Pluto and its known natural satellites. No serious attempts to explore Pluto had ever been made. In year 2000, NASA 6 cancelled the mission ‘Pluto Kuiper Express’ a�er intense political battle with the U.S government. But in 2003, the U.S congress granted funding on a new mission named ‘New Horizons’. �e space-cra� carried some ashes of Clyde Tombaugh, the discoverer of Pluto. �e New Horizons launched o� successfully on January 19th, 2006. It made use of Jupiter’s gravity assist and now is on closest reproach on Pluto which will be made approximately on July 14th, 2015. But the discovery of the two smaller moons, which was a�er the launching, made unforeseen di�cul-ties for New Horizons. �e discovery made it possible for other small moons to exist around Pluto. Also debris from the Kuiper belt and the small moons could collide with the cra� and make some serious damage.

7 MediaWiki. “Classical Kuiper Belt Object.” Wikipedia, the free encyclopedia. 5 Oct 2009. http://en.wikipedia.org/wiki/Classical_Kuiper_belt_object. KBO is a Kuiper belt object (KBO) that orbits beyond Neptune and is not controlled by an orbital resonance with the giant planet.

�e origin of Pluto puzzled scientists and astronomers for a long time. �ere were lots of hypotheses but none could be witnessed. �e celestial’s origin began to show up in 1992, when astronomers found small icy beyond Neptune that were similar to Pluto not only in orbit but also in size and composition. �ese celestial objects formed a belt which is now known as the Kuiper belt. �is trans-Neptunian population is believed to be the source of many short-period comets. Pluto is the largest known object in Kuiper belt. It shares features with comets; for example, the solar wind is blowing Pluto’s surface into space. If Pluto was closer to the Sun, it would develop a tail like other comets. �ough Pluto and Neptune’s moon Triton is similar to both geologically and atmospherically, Triton is not considered as a Kuiper belt object but considered as a member of linked population called scattered disc. In the early stage of the solar system’s formation, Triton was a KBO (Kuiper Belt Object) 7 . But unusually, Neptune migrated further away from the Sun and got nearer to the Kuiper belt. As it approached the belt, it pulled an object and set the object in orbit around it which now became Triton. Many scientists and astronomers agree that the unusual movement of the Neptune knocked out Pluto out of its original place and into the Kuiper belt. Astronomers think that 1:2 resonance between Jupiter and Saturn which created a gravitational push that propelled Uranus and Neptune into higher orbits and caused them to switch places. �is doubled Neptune’s distance with the Sun and ultimately changed Pluto’s location. Pluto’s downfall to a dwarf planet had several reasons. People made a lot of gossips about why it has lost its original status. So scien-tists announced a few main reasons that why Pluto has been banished. First, Pluto’s orbital eccentricity is tilted by 0.248 while other 7 planets’, except Mercury, orbital eccentricities are in the range of 0.005~0.095. �is hugely separated orbit route makes Pluto go around the Sun in elliptical path while others are orbiting in a circle. Second, Pluto is smaller than some big natural satellites of other planets. �e small mass and size makes the gravitational force of the celestial object weak. And because of the weak gravity it can’t dominate its own moons which is the third reason. �e weak gravitational force of Pluto makes it unable to be the most domi-nating celestial body in that area. And because of its small mass, size, and weak gravity, it turns in circles in place due to the in�uence of its largest moon, Charon. IAU does not emphasize the �rst two reasons because Mercury’s orbit is almost tilted strangely as Pluto and its size and mass are smaller than the natural satellites of other planets. �ese circumstances of Pluto are not the same as the planets that orbit around the sun.

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http://cruxmj.innori.com/55http://ask.nate.com/qna/view.html?n=8270211http://blog.joins.com/media/folderListSlide.

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�e term dwarf planet was spoken since 2006 when trans-Neptunian celestials’ discoveries started to increase. �e dwarf planets are o�en confused with satellites and minor planets but they are greatly di�erent. Minor planets are like an asteroid which moves in the Sun’s orbit. A minor planet, or an asteroid, is a small celestial body but bigger than meteoroids. Comets and meteors are not included in this celestial. A satellite is an asteroid or a meteoroid that got caught by a planet’s gravitational force and orbit around the planet. A dwarf planet is a trans-Neptunian celestial which doesn’t satisfy one or more conditions to be called as a planet. Likewise, Pluto doesn’t suit the circumstances of a planet. Pluto’s exert from the planets of our Solar System is still being discussed, but in my opinion it is clear that Pluto’s exile doesn’t have any reasons to be brought up as a topic for an argument. �e reason is that a dwarf planet located in the asteroid belt named Ceres is a bigger celestial body than Mars, which is the third biggest planet out of the nine planets in our Solar System, but it is categorized as a dwarf planet because its insu�cient environment and circumstances are not matched to the conditions to become a planet. �ere are some candidate celestial bodies to be classi�ed as a dwarf planet.