The science case for why Pluto still isn't a planet

"In 2006, with only a small fraction of the general assembly in attendance, the International Astronomical Union put forth three criteria that an object needed to meet in order to be officially defined as a planet: it must be massive enough to pull itself into hydrostatic equilibrium, it must orbit the Sun and the Sun alone, and it must 'clear its orbit.'"

"Rather than adding in additional planets such as Ceres and Eris, or accommodating the newfound population of exoplanets, this move instead changed the number of planets in the solar system by one: from 9 to 8. The big change affected Pluto most severely: stripping it of its longstanding planetary status."

"This definition remains controversial even today, both among scientists within specific subfields of astronomy and planetary science, as well as politically, as many note that this is only making news today to serve as a distraction from the ongoing catastrophic funding cuts to NASA and NSF science."

From 1929 to 2006, Pluto was considered the ninth planet in the solar system. The discovery of Charon in 1978 and numerous new celestial objects in the 1990s and 2000s prompted a reevaluation of planetary definitions. In 2006, the International Astronomical Union defined a planet based on three criteria, resulting in Pluto's reclassification as a dwarf planet. This decision remains controversial among scientists and has implications for funding in astronomy and planetary science.

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