Written by Michael K. (KIS'19)
Edited by Jaemin Y. (KIS'19)
━━ April 7th, 2018 ━━
Why Pluto is No Longer a Planet
Going back to the actual discovery of Pluto, Pluto was discovered by US astronomer Clyde Tombaugh in 1930. He found out that there was an unknown object in the solar system near Neptune and Uranus. How did it get its name? Surprisingly, it came from an 11-year-old girl named Venetia Burney who had interest with ancient mythology–while she was eating breakfast with her family, she just thought of the word “Pluto” which is the Roman name of Hades.
Compared to Earth, the size of Pluto is significantly small as it is even smaller than Earth’s moon. A year on Pluto is 248 Earth-years and a day lasts about 6 Earth days. Unlike Earth, Pluto has an atmosphere full of nitrogen, methane, and carbon monoxide. The weather in Pluto is completely different compared to the Earth. Obviously, Pluto is far away from the Sun which makes it very cold. It is colder than Antarctica and goes to the point where Earth’s air would freeze right away in Pluto. Pluto also orbits completely different. While most planets including Earth orbits the sun in a circle, Pluto does not orbit in a circle. Pluto’s orbit is more like an oval as it is slightly tilted.
To discover more information about Pluto, NASA decided to launch Hubble Space Telescope in 1990. This telescope, with the ability to orbit around Earth in 95 minutes, was sent to take photos of planets, stars, and galaxies. In 2015, it revealed that “Pluto’s crust could contain complex organic molecules” and that there is a fifth moon orbiting Pluto.
Until 2006, Pluto was known as the ninth planet of the solar system after Neptune. However, the astronomers started to question if Pluto was simply just part of the Kuiper Belt, the area outside of our solar system, near the orbit of Neptune. Another solar system made of ice is in the Kuiper Belt, such as Pluto, Haumea, and Makemake. As more planet-like objects were starting to be found in Kuiper Belt like Quaoar, Sedna, and Eris, the controversy started. Also, when Eris, a bit larger than Pluto, was found in 2005, astronomers started to regard Eris as the “tenth planet” of the solar system after Pluto.
To settle this huge controversy, International Astronomical Union decided to have a committee at the general assembly in Prague. Initially, everything was running smoothly and the committee was about to declare that the total number of planets in the solar system would be 12: Pluto and its moon Charon would be regarded as a twin planet and Ceres and Eris would also be known as a planet. However, this proposal became a failure when the committee came up with a “new version of a planetary definition”. According to Merriam-Webster, a planet is a “celestial body that is in orbit around the Sun, has a sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit”. Even though Pluto fits the first two rules, it has not cleared the neighborhood around its orbit, meaning that it does not have gravitational dominance nearby its orbit. This, unfortunately, is due to the fact that Pluto shares its orbit with other planet-like objects in Kuiper Belt. As a result, Pluto was demoted as a “dwarf planet” along with Ceres, Eris, and many more celestial bodies in the Kuiper Belt.
Obviously, this choice immediately brought questions with the proposed definition of a planet. People started to question the third part of the definition: a planet has cleared the neighborhood around its orbit. Even Earth shares its orbit with near asteroids and to go even further, most of the planets in our solar system would fail to meet the definition of a planet. Numerous scientists stated that the new definition was inconsistent and that only 10% of the scientists who were at the meeting were present to vote. After the voting finished, most of the people the people opposing the new definition have already left the country and couldn’t participate.
Despite the unfortunate incident of Pluto, scientists and astronomers gained some hope after discovering the “solar system’s third zone”. Jeff Moore at NASA said “ Pluto may be the star witness to the whole third zone of the solar system”. Originally, there were only two zones: the inner zone and outer zone–the inner zone was from Mercury to Mars while the outer zone was consisted of “gas planets from Jupiter to Neptune”. Thankfully, the Kuiper Belt discovery exposed the astronomers with new information about the solar system. Jeff Moore specifically referred Kuiper Belt as a “vast realm of ice worlds”. Because of this information, scientists gained confidence and are hoping to find more details with “New Horizons”, a space probe launched on January 19, 2006. Gliding through the Kuiper Belt, Pluto is simply just the beginning of the space exploration.
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Bibliography:
Dunbar, Brian. “What Is Pluto?” NASA, NASA, 21 May 2015, www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-pluto-k4.html.
Koffler, Jacob. “Pluto: 9 Facts You Need to Know.” Time, Time, 14 July 2015, www.time.com/3957053/pluto-facts/.
“Pluto.” NASA, NASA, 22 Feb. 2018, www.solarsystem.nasa.gov/planets/dwarf-planets/pluto/overview/#introduction_otp.
Rincon, Paul. “Why Is Pluto No Longer a Planet?” BBC News, BBC, 13 July 2015, www.bbc.com/news/science-environment-33462184.
Stromberg, Joseph. “How a 12-Year-Old Girl Gave Pluto Its Name.” Vox, Vox, 10 July 2015, www.vox.com/2015/7/10/8922615/pluto-name.
Wall, Mike. “Pluto Has a Fifth Moon, Hubble Telescope Reveals.” Space.com, www.space.com/16531-pluto-fifth-moon-hubble-discovery.html.
“Why Is Pluto No Longer a Planet?” Wonderopolis, www.wonderopolis.org/wonder/why-is-pluto-no-longer-a-planet.
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