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Pluto has been through a lot in recent years. First discovered by astronomer Clyde Tombaugh in 1930, the dwarf planet lost its planet status in 2006, when the International Astronomical Union (IAU) determined that Pluto’s orbit crossed Neptune's. Under new IAU guidelines, a planet must orbit the sun, be round due to gravity, and "clear" its orbital path, establishing itself as the dominant body in that area. Pluto met the first two requirements but not the third, resulting in its downgrade to dwarf planet.
This decision sparked ongoing debates about whether Pluto truly deserved its demotion. The latest and potentially most convincing argument comes from a paper by researchers at the University of Central Florida's Space Institute, published in the planetary science journal Icarus. Philip Metzger, the lead author, argues that no one has used the clearing-orbit criterion to define a planet since 1802. Describing the IAU’s definition as "sloppy," Metzger and his team highlight that this rule has never been applied to distinguish asteroids from planets. The paper contends that planets should not be judged by dynamic characteristics of celestial bodies that may evolve over time.
"We now have over 100 examples of planetary scientists using the term planet in ways that contradict the IAU’s definition, but they do so because it’s practically useful," Metzger said in a statement. "The definition is sloppy. They didn’t explain what ‘clearing their orbit’ actually means. If we take it literally, then there wouldn’t be any planets, because none of them clear their orbit."
Metzger argues that a planet should be defined by its size, large enough to become spherical under its own gravity, which in turn drives geological activity.
In a conversation with CNN, IAU spokesperson Lars Lindberg Christensen mentioned that there could be a proposal to reconsider Pluto's classification, though no one has yet made such a motion.
No matter Pluto's current status or potential future, to Clyde Tombaugh, it will always be a planet. Tombaugh, who never lived to see Pluto’s reclassification, passed away in 1997. In 2015, his remains, aboard the New Horizons spacecraft, entered Pluto's orbit after a nine-year journey.
