7 Things You Didn’t Know About Pluto’s Astronomical Status
On August 24, 2006, Pluto was officially denounced as the ninth planet orbiting the Sun in our solar system. The International Astronomical Union (IAU) voted to retitle it as one of many dwarf planets in the Kuiper Belt. This topic of discussion caused quite a bit of controversy around the final decision. Many people who grew up learning about the Sun, which, at the time, had nine planets that orbited it, Pluto being one of them, were not pleased with Pluto’s demotion. Those who disagreed with the IAU’s decision had to accept that now only eight planets orbit our Sun.
With that being said, let’s look into some of the factors that you may not have known about that contributed to the decision of Pluto’s official demotion from a planet to a dwarf planet. Here are seven lesser-known facts about Pluto!
1. Pluto’s Name Was Given by an 11-Year-Old Girl
Pluto was discovered on February 18, 1930, by 24-year-old observatory assistant Clyde Tombaugh at the Lowell Observatory in Arizona. The name "Pluto" was suggested by Venetia Burney, an 11-year-old girl from Oxford, England. She was intrigued by the discovery and proposed the name of the Roman god of the underworld, given Pluto's distant and dark position in the solar system. Pluto's name is rooted in both astronomy and mythology.[1]
The decision was officially announced on March 24, 1930, and quickly gained acceptance. Celestial bodies are traditionally named after mythological figures, and Pluto’s name follows this tradition. Not only is the dwarf planet named after a mythological figure, but Pluto’s moon, Charon, also follows this tradition. Charon is named after the mythological demon who ferried souls to the underworld.[2]
2. Pluto Has Five Known Moons
Pluto, despite its reclassification as a dwarf planet, has five known moons. These moons—Charon, Styx, Nix, Kerberos, and Hydra—each contribute to the complex and intriguing nature of Pluto’s standing in the Kuiper Belt. All are named to follow the lead of Pluto’s name; the moon’s names are related to mythological figures, creatures, and landmarks from the underworld.
Charon (named after the mythological ferryman who carried souls across the river Acheron) was accidentally discovered by James Christy and Robert Harrington at the U.S. Naval Observatory in Flagstaff, Arizona, in 1978. They were originally attempting to refine Pluto’s orbit around the sun, but they randomly came across the moon in the process.[3] This moon, in particular, is the largest of Pluto's moons, about half the size of Pluto itself, and it orbits very closely. This relationship leads to the understanding that Pluto and Charon are a double dwarf planet system or a binary system. Its relatively large size compared to Pluto's other moons makes it a prime candidate for studying the interactions within the Pluto system.[4]
The smaller moons—Styx, Nix, Kerberos, and Hydra—were discovered more recently than Charon. Nix (named for the Greek goddess of darkness and night and mother of Charon[5]) and Hydra (named after the nine-headed serpent that Hercules fought in Greek and Roman mythology[6]) were discovered by Hal Weaver, and a large team of astronomers using the Hubble Space Telescope in 2005. Kerberos (named after the three-headed dog of Greek mythology[7]) was discovered in 2011, and Styx (named after the mythological river that separates the world of the living from the realm of the dead[8]) was found in 2012 by a large team led by Mark Showalter also using the Hubble Space Telescope. These moons are much smaller than Charon and exhibit irregular shapes. Pluto's moon system is believed to have formed after a collision between Pluto and another Kuiper Belt object early in the solar system's history. The strike broke up the materials that now rest around Pluto as all of its moons.[9]
3. Pluto is About a Fifth the Diameter of Earth
Since Pluto is so far from Earth, it took some time before Pluto’s true size and features were truly evaluated. In 2015, NASA’s New Horizons spacecraft did a close flyby of Pluto and measured 1,473 miles for the diameter of the dwarf planet, measuring less than a fifth of Earth’s diameter.[10]
Pluto has a varied landscape that includes vast plains of frozen nitrogen, towering mountains made of water ice, and a range of colorful terrain. With the close-up shot of Pluto’s features and overall structure, mountain-like peaks reached as high as 11,000 feet. For comparison, the Rocky Mountains that run through the U.S. and Canada have a maximum peak of about 15,000 feet. Some craters are as large as 162 miles in diameter, and some show signs of erosion. The plains spotted on Pluto’s surface appear to be made of frozen nitrogen gas.[11]
4. The Temperature on Pluto Cannot Sustain Life
The temperature on Pluto can be as cold as -375 to -400 degrees Fahrenheit (-226 to -240 degrees Celsius). Its surface temperature varies depending on its location and the time of day, but it remains far colder than any temperatures experienced on Earth. The thin atmosphere of Pluto, primarily composed of nitrogen, methane, and carbon monoxide, contributes to its frigid climate. At such cold temperatures, water, which is essential for living organisms, is basically solid because of these below-freezing temperatures. Pluto's interior is warmer, however, and some think there could possibly be an ocean deep inside.[12]
5. The Word “Plutoed” was Voted Word of the Year in 2006
In 2006, a unique term made headlines when the American Dialect Society selected their Word of the Year: “plutoed.” The special word emerged in response to the astronomical reclassification of Pluto, which had recently been demoted from its status as the ninth planet in our solar system to that of a "dwarf planet" by the IAU. This reclassification sparked a wave of public interest and debate, and "plutoed" quickly became an alternative term for describing a sudden or unexpected demotion or downgrade.
The concept behind "plutoed" resonated with many people because it metaphorically represented the broader human experience of facing unforeseen changes or reductions in status. Just as Pluto's status was altered, individuals and institutions alike could relate to the feeling of being unexpectedly sidelined or diminished. The term's rise was not only a reflection of a specific scientific event but also an indication of how language evolves to address new realities and societal shifts.[13]
6. Pluto’s Solar System Status Was Short-Lived
As our understanding of the solar system evolved, so did the criteria for what constitutes a planet. By the late 20th and early 21st centuries, astronomers recognized that Pluto did not fit neatly into the increasingly refined definition of a planet. This is what led the IAU to redefine the term "planet," and Pluto was reclassified as a "dwarf planet." Pluto was considered one of the nine planets in our solar system for only about 76 years. This decision was grounded in the need to distinguish between the traditional planets and other small bodies that share similar characteristics, particularly in the Kuiper Belt.[14]
7. Many Mourned the Demotion of Pluto’s Status
Many people grew up learning that Pluto was one of the nine planets that orbit the Sun in our solar system. They had space-themed bedrooms, science projects at the science fair they worked hard on, and all sorts of things from their childhood that represented the then-nine planets orbiting the Sun. Now, there are only eight, and many have expressed that they don’t like this change.
Due to some public disagreements involving this situation, people began to mourn Pluto publicly. Outside of the Smithsonian Castle in Washington D.C., there is a sidewalk model of it where people began to place flowers, notes, cards, and signs reading that they are sorry to hear of the status change, that Pluto will be missed, and how Pluto will always be a real planet to them. Many, especially those who believe Pluto was abruptly evicted from its planetary status, question the fairness and legitimacy of the IAU’s vote, arguing that only one-tenth of the 2,700 scientists who attended the conference were present for the ballot taken on its closing day in 2006.[15] However, the decision became final, prompting mourning, disappointment, and protest amongst many Pluto fans.
Whether you are a Pluto fan who mourns its lost status or agrees with the IAU's decision, you can learn more about astronomers' reasons for giving Pluto the dwarf planet title. Check out Caltech astronomer Mike Brown’s book, How I Killed Pluto and Why It Had It Coming. EarthSky also covers an interview with Mike Brown, talking more about his book and the topic of Pluto in general.
If you’re interested in getting some engaging space-related titles for your children, grandchildren, or students who want to learn more about space science, check out these titles from Carole Marsh that they will love: The Mission Possible Mystery at Space Center Houston, Science Alliance: Steven Soars into Space Science, When Kids Take Over NASA, and The Mystery at Area 51! There are even some biographies in our 1000 Readers series about fascinating famous astronomers and astronauts, such as Neil deGrasse Tyson, Dr. Mae Jemison, Nicolaus Copernicus, Neil Armstrong, and more! Head over to gallopade.com to find more titles that pique your scientific curiosity!
Sources:
[1] “Pluto: FACTS - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/facts/. Accessed 30 July 2024.
[2] Choi, Charles Q., and Scott Dutfield. “Pluto: Everything You Need to Know about the Dwarf Planet.” Space.Com, Space, 28 July 2022, www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html.
[3] “Charon - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/charon/. Accessed 12 Aug. 2024.
[4] Choi, Charles Q., and Scott Dutfield. “Pluto: Everything You Need to Know about the Dwarf Planet.” Space.Com, Space, 28 July 2022, www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html.
[5] “Nix - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/nix/. Accessed 12 Aug. 2024.
[6] “Hydra - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/hydra/. Accessed 12 Aug. 2024.
[7] “Kerberos - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/kerberos/. Accessed 12 Aug. 2024.
[8] “Styx - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/styx/. Accessed 12 Aug. 2024.
[9] “Pluto Moons: Facts - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/moons/facts/. Accessed 12 Aug. 2024.
[10] Choi, Charles Q., and Scott Dutfield. “Pluto: Everything You Need to Know About the Dwarf Planet.” Space.Com, Space, 28 July 2022, www.space.com/43-pluto-the-ninth-planet-that-was-a-dwarf.html#section-what-does-pluto-look-like.
[11] “Pluto: FACTS - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/facts/. Accessed 30 July 2024.
[12] “Pluto: FACTS - NASA Science.” NASA, NASA, science.nasa.gov/dwarf-planets/pluto/facts/. Accessed 30 July 2024.
[13] ADS. “‘Plutoed’ Voted 2006 Word of the Year - American Dialect Society.” American Dialect Society, 6 Jan. 2007, americandialect.org/plutoed_voted_2006_word_of_the_year/.
[14] ADS. “‘Plutoed’ Voted 2006 Word of the Year - American Dialect Society.” American Dialect Society, 6 Jan. 2007, americandialect.org/plutoed_voted_2006_word_of_the_year/.
[15] Klein, Christopher. “The Rise and Fall of Planet Pluto.” History.Com, A&E Television Networks, 24 Aug. 2016, www.history.com/news/the-rise-and-fall-of-planet-pluto.
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