The dwarf planet Pluto was initially discovered in 1930 by Clyde Tombaugh and was originally classified as the ninth planet from the Sun. However, The International Astronomical Union in 2006 redefined Pluto as one of a growing family of dwarf planets. To jokingly quote Douglas Adams out of context, “This has made a lot of people very angry and been widely regarded as a bad move.” But the IAU is actually justified; closer inspection reveals why Pluto does not deserve the title of “planet.” According to popular astronomer Dr. Neil DeGrasse Tyson, “Pluto has peculiar written all over it.” First, its orbit is much more elliptical than the rest of the planets, so non-circular that it actually comes in front of Neptune’s orbit for a portion of its orbit, having only just returned to its normal position in 1999. It also lies outside the plane of the rest of the planets, rising above and below the rest of the planets and behaving generally like a comet but with a much more stable orbit. In addition, Pluto has several moons. In the early 19th century the large asteroid, dwarf planet Ceres was discovered in between Mars and Jupiter and unveiled the existence of the Asteroid belt, a sparsely populated area of small debris with about four large asteroids in it that are all just a little smaller than Pluto. Unfortunately, Ceres lost its planetary status soon after the discovery of other asteroids sharing its orbit and has been considered an asteroid ever since. Though Pluto may be the largest of its kind, it is still smaller than a total of seven moons in the solar system and its own moon system is dominated by Charon, along with four other tiny moons. To see what the actual damage is just take a peek at the new, official and exclusive definition of a planet the IAU has developed. The official definition from iau.org 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 shape and has cleared the neighborhood around its orbit,” and the IAU’s official reason for the demotion is, “Pluto now falls into the dwarf planet category on account of its size and the fact that it resides within a zone of other similarly-sized objects known as the transneptunian region.” If that definition and reason sounds lame to you then it probably is. So, next time you lament the passing of Pluto, just remember that it never really belonged in the list of planets anyways. It was just a misunderstood dwarf planet, comet, Kuiper Belt object or whatever you want to call it, so long as you do not call it a planet.
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Truth behind Pluto’s demotion
Cameron Clarke
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September 10, 2012
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