Date of Award

Spring 2019

Document Type

Term Paper


School of Unrestricted Education

Primary Advisor

Dr. Grace Veach


Nearly 100 years ago, astronomers hypothesized that a large celestial object, nicknamed “Planet X,” must be pulling two planets out of their typical heliocentric orbits. After racing to find this celestial object for decades, Clyde Tombaugh found a faint sparkling speck of light and announced that he had finally discovered Planet X. Later, Tombaugh’s discovery was named Pluto and immediately deemed the ninth planet. As technology improved, many other celestial objects were found lurking in the outer limits of the solar system leading to worldwide confusion over which were official planets. To solve the problem, the International Astronomical Union (IAU) met to create a universal definition for planets. In this meeting, the union declared that celestial objects must have heliocentric orbits, assume hydrostatic equilibriums, and clear the neighborhoods around thier orbits to be classified as a planet. Also, the IAU formed a new category of celestial objects called “dwarf planets.” While dwarf planets follow the first two criteria for planets, dwarf planets’ obits are scattered with debris unlike planets’ orbits. After carefully studying Pluto’s neighborhood, the IAU reclassified Pluto as a dwarf planet stripping it of its planetary status. Infuriated by the IAU’s decision, some people argue today that Pluto is worthy of a planetary title; however, Pluto should be categorized as a dwarf planet because the celestial object complies with the IAU’s three criteria for dwarf planets. Although those, who believe that Pluto is a planet, argue that the IAU’s third criterion for planets and dwarf planets is too ambiguous, Margot’s formula can be utilized to calculate if a celestial object has successfully cleared its neighborhood. Because Pluto’s orbit remains intercepted by celestial debris according to this formula, Pluto should be categorized as a dwarf planet.