The Discovery of a Dwarf Planet

Written by: Liann

In 1930, astronomer Clyde W. Tombaugh made a discovery in finding the ninth planet that was first theorized in 1905 by astronomer Percival Lowell. Lowell calculated the approximate location, however, he had no success in actually finding it.

The hunger to search for the ninth planet began when Lowell hypothesized that the unusual orbitals of Uranus and Neptune were subjected by an unknown source of gravitational pull. Having to keep his hypothesized ninth planet a secret, Lowell used his mathematical skills and his own observatory to carry out this search. He also worked with mathematician Elizabeth Williams, alongside a small team of ‘computers,’ in hopes of finding what he later called ‘Planet X’ to represent his hunting quest for the planet.

On the far side, astronomer W. H. Pickering, who previously helped Lowell set up his Arizona observatory lab, proposed the theory of the existence of a trans-neptunian object (TNO) or in other words, any object in the solar system that has an orbit beyond Neptune. He published its location in 1908, naming it the ‘Planet O.’This made Lowell escalate his own search as he saw Pickering’s research as competition, and wanted to win the race of finding a planet.

Unfortunately, Lowell passed away a year before having the chance to complete a full photographic survey of the sky with his new equipment and discoveries. His research for Planet X was then resumed in 1929 by astronomer Clyde W. Tombaugh. Given that both Lowell and Pickering laid the groundwork in search for the ninth planet, Tombaugh discovered the ninth planet on February 18, 1930. However, Lowell’s theorised location of ‘Planet X’ and Pickering’s ‘Planet O’ were in fact not the ninth planet that was found by Tombaugh.

The Planet was named Pluto, suggested randomly to Tombaugh by an 11-year-old girl, named Venetia Burney, in England. ‘‘Pluto’’ was derived from the Greek name “Plouton.” Plouton being the Roman god of the underworld. Consequently, all of Pluto’s moons, Charon, Nix, Hydra, Styx, and Kerberos, were named after the underworld mythological figures.

The orbitals of Neptune and Pluto in the Solar System

Pluto’s discovery brings up the question of whether it was the unknown source of gravitational pull that disrupted Uranus and Neptune’s orbitals. It was concluded by astronomers James Christy and Robert Harrington that Pluto and Charon, the only moon known in 1978, had enough masses to disrupt the orbitals of Uranus and Neptune. However, Pluto’s place in the solar system was removed in 2006 as it did not fully fit the criteria outlined by the International Astronomical Union (IAU). Pluto met two aspects of the criteria. One criterion being orbiting a star, which is the sun in our solar system, and the second, having enough gravitational force that makes the planet a spherical shape. The third criterion Pluto did not meet was that its gravitational force wasn’t strong enough to remove its neighbouring dusts, rocks and other objects that are in the pathway of its orbital. Located in the Kuiper belt while overlapping Neptune’s orbit, Pluto is now known as a dwarf planet.

Edited By: Gisele & Iraj

---

Bibliography:

Hoyt, William Graves. “W. H. Pickering's Planetary Predictions and the Discovery of Pluto.” Isis, vol. 67, no. 4, 1976, pp. 551–564. JSTOR, www.jstor.org/stable/230561. Accessed 9 July 2020.

Levine, Eitan. “Pluto Is a Planet Again, Sorta.” Mashable, Mashable, 2 Oct. 2014, mashable.com/2014/10/02/pluto-planet-again/.

“NASA Studies Plan to Send an Orbiter to Pluto.” EarthSky, earthsky.org/space/nasa-studies-plan-to-send-an-orbiter-to-pluto.

“Overview.” NASA, NASA, solarsystem.nasa.gov/planets/dwarf-planets/pluto/overview/#:~:text=Pluto%20is%20the%20only%20world,Observatory%20and%20it%20was%20selected.

“Percival Lowell's Quest.” The Discovery of Pluto - Percival Lowell's Quest, www.discoveryofpluto.com/pluto04.html.

“Pluto Discovered.” History.com, A&E Television Networks, 3 Mar. 2010, www.history.com/this-day-in-history/pluto-discovered.

Schindler, Kevin. “Percival Lowell's Three Early Searches for Planet X.” Astronomy.com, 14 May 2015, astronomy.com/year-of-pluto/2015/05/percival-lowells-three-early-searches-for-planet-x.

“Small Bodies Profile.” NASA, NASA, pds.jpl.nasa.gov/planets/special/smbod.htm.