A new research study suggests that the dwarf planet Pluto should be reclassified as a planet again. Pluto was considered to be the ninth planet in our solar system until 2006, when the International Astronomical Union (IAU) downgraded its status to dwarf planet.
Now in a new paper published in the journal Icarus, a planetary scientist at the University of Central Florida, Philip Metzger, argues that the reasons Pluto lost its planet status are not valid and that it should be reclassified as a planet again.
According to the IAU, a planet is a celestial body that “has cleared the neighborhood around its orbit,” which means the planet is the largest gravitational force in its orbit. However, since Pluto’s closest neighbor, Neptune, is quite a large planet, it influences its smaller neighbor gravitationally. Moreover, Pluto shares its orbit with frozen gases and other objects that orbit in the Kuiper belt, according to IAU researchers.
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Metzger is the lead author of the new study. He has reviewed scientific literature from the past 200 years and found only one publication from 1802 which references the requirement of classifying planets based on the orbit-clearing requirement. However, Metzger added that the 1802 publication is based on “since-disproven reasoning.” In his study, he stresses that the IAU’s definition of a planet should be reconsidered.
“It’s a sloppy definition,” he explained in a statement. “They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.”
For example, larger moons like Saturn’s Titan and Jupiter’s Europa have been considered and referred to as planets since Galileo’s time, he said.
“We now have a list of well over 100 recent examples of planetary scientists using the word ‘planet‘ in a way that violates the IAU definition, but they are doing it because it’s functionally useful,” he added. “Dynamics are not constant, they are constantly changing. So they are not the fundamental description of a body; they are just the occupation of a body at a current era.”
Metzger has a new recommendation of how planets should be classified and why Pluto should be reclassified as a planet. He believes a body should be considered a planet based on whether it is enough large for its gravity to make it spherical in shape.
“It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body,” he said.
He also noted that Pluto has an underground ocean and evidence of ancient lakes, an atmosphere consisting of multiple layers, organic compounds, and several moons.
No official proposal
According to Fox News, the IAU said there hasn’t yet been a formal call or proposal for Pluto to be reclassified as a planet.
“There is a very clear, and known, way to table motions in the IAU, which is to propose an IAU Resolution through the relevant Working Group(s) and Division. So far, no such Resolutions have been proposed,” a spokesman said in an email. “It is nevertheless good and healthy to debate these topics.”