Why Isn’t Pluto A Planet Anymore?

For decades, students from elementary school on have been taught that Pluto was a planet, one of the ten largest bodies that move in direct orbits around the sun. This was common and accepted knowledge among most astronomers as well so there was little discussion about Pluto’s status until very recently.

plutoScientists believe that Pluto is made up of rock and ice, but only enough of those materials to make it the smallest sun-orbiting object in our system. Pluto was also the planet orbiting farthest from the sun.

Now the small object that has been recognized as a planet for many years is no longer on the official list. A decision in 2006 from the International Astronomical Union changed Pluto’s designation from “planet” to “minor planet.” The orbiting body will now also be referred to as a “dwarf” planet.

According to its Web site, “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. In addition, the IAU collaborates with various organizations all over the world. The IAU has 10144 Individual Members in 90 countries worldwide. Of those countries, 68 are Members. The focal point of its activities is the IAU Secretariat, hosted by the Institut d’Astrophysique de Paris, France.”

Records of the IAU show that the discussions in 2006 were about changing what makes a planet a planet. According to new guidelines, Pluto doesn’t meet the organization’s definition. The list of planets now includes only eight orbiting bodies instead of nine.

Scientific texts and research show that the eight remaining planets have enough mass to become round due to gravity. New standards also require that the orbiting body’s gravity should be strong enough to keep items from cluttering the atmosphere around the body. This was a key during discussions that eventually reduced Pluto’s status.

Pluto is one of the small orbiting bodies in the solar system in a classification that includes asteroids and comets. Investigation into Pluto’s designation continues, with the United States space organization – National Aeronautics and Space Administration leading the study.

According to records of the meeting, there was opposition among the more than 2,000 astronomers from dozens of countries. Even this large number represented only a fraction of the astronomers on the planet.

The debate continues and some among the scientists feel that the decision will be reversed. One of the leading opponents of the change was the family of the American astronomer who found and reported Pluto about 80 years ago in Arizona. A number of other leading minds in the field joined in the opposition to reducing Pluto’s status to minor or dwarf planet.

For many observers of the skies, the Pluto question is not yet settled.

Category: Astronomy, Science

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