Why Did Scientists Downgrade Pluto from Being a Planet?

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The Solar body Pluto has been a source of battles even before they discovered it. Its long history has seen judicial rivalry, scientific errors, and the long-reigning division in the astronomical community.  Most of these conflicts revolve around why did scientists downgrade Pluto from being a planet.

During the 1990s, scientists considered Pluto as the ninth planet in our Solar system. Even though there were some discussions as to its size and mass, the scientific community supported its status.  For example, in 1930 both the  American Astronomical Society and the Royal Astronomical Society voted unanimously to name the new planet, Pluto.

However, this did not mean a time of peace. In 1919 the widow of a famous astronomer, Constance Lowell, launched a ten-year legal battle with the  Lowell Observatory. Her lawsuit crippled further studies until 1929. A year later, Clyde W. Tombaugh discovered the planet.

Why Did Scientists Downgrade Pluto from Being a Planet?


Once they confirmed the discovery of the new planet, more rivalry sprung to life. One group of scientists wanted to name the planet after  Percival Lowell, whom they believed found it first. Altogether more than a thousand suggestions bombed the the Lowell Observatory.  Among these, three recommendations were common:

  • Minerva: The panel eliminated this title since it was already used
  • Pluto:  More than 150 persons had submitted this option
  • Cronus: This suggestion had no chance since Thomas Jefferson Jackson See, a controversial astronomer with little support, promoted it.

Notably, Pluto is the name of the Roman god of the underworld but even after winning this battle, the war continued.  In 1951 another scientist, Gerard Kuiper, created a theory that a belt of smaller planet-like objects existed close to Neptune. By 1992, the discovery of a minor planet Albion would set the stage for a re-classification of Solar bodies.

New Definition of Planets Dwarfs Pluto

In 2005, the International Astronomical Union (IAU) redefined planets and established new classifications that would directly affect Pluto and other similar ‘Dwarf Planets”.  The new resolution summed up the  definition in three characteristics:

  1. The object must orbit the sun. Here Pluto fully qualifies.
  2. Its next feature demands that the body must have enough mass (be big enough) so that gravity can mold it into a sphere. Another thumbs up for our underworld guy.
  3. In addition, the object must have removed all other bodies or debris from its orbit. This is where Pluto failed.

The IAU downgraded it since Pluto shares a common orbit or the Kupler Belt with 100s of other objects.

However, the war continues. The State of California passed a resolution declaring the IAU’s ruling as  “scientific heresy”. A similar move by the New Mexico House of Representatives declared March 13, 2007, was Pluto Planet Day. In 209, the Illinois Senate followed suit.

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