IAU Reclassified Pluto 20 Years Ago After Eris Discovery Forced 3-Part Planet Test
Updated
Updated · CNET · Aug 24
IAU Reclassified Pluto 20 Years Ago After Eris Discovery Forced 3-Part Planet Test
3 articles · Updated · CNET · Aug 24
Summary
Twenty years after the 2006 vote, Pluto remains classified as a dwarf planet under International Astronomical Union rules that stripped it of status as the solar system’s ninth planet.
Eris’s 2005 discovery drove that decision because the Pluto-sized object forced astronomers to define what counts as a planet rather than keep expanding the list.
The IAU’s 3-part test says a planet must orbit the sun, be massive enough to become round and clear its orbital neighborhood; Pluto fails the third requirement.
David Gerdes of Case Western said any definition that restores Pluto would also pull in Eris, Sedna, Makemake and Ceres, reviving the debate over how many planets the solar system has.
The dispute still resonates in 2026, with NASA Administrator Jared Isaacman and actor William Shatner among those backing Pluto’s return to planet status.
Will the approaching 2030 centennial of Pluto's discovery trigger a scientific rebellion against the controversial rules that stripped its planetary crown?
Could Pluto's active geology and mysteriously freezing atmosphere force astronomers to finally rewrite the rules of planetary classification?
If nature ignores our labels, why are scientists still fiercely battling over Pluto's true identity twenty years after its demotion?