Overview
- The International Astronomical Union reclassified Pluto as a dwarf planet under a three-part definition in August 2006 that requires an object to orbit the Sun, be nearly round, and have “cleared the neighbourhood” of other bodies.
- New Horizons’ 2015 flyby revealed Pluto’s unexpected geology and atmosphere, a central argument used by critics who say planetary status should weigh physical traits as well as orbital dynamics.
- Critics also question the 2006 vote’s representativeness because only meeting attendees could vote, leaving fewer than five percent of the nearly 9,000 IAU members recorded as participants.
- The IAU told reporters in March 2026 that no formal work is underway to rewrite the planet definition and that any change would require extensive scientific study and approval at a future General Assembly, next scheduled for August 2027 in Rome.
- A full redefinition that drops the orbital‑clearing criterion would likely add many large Kuiper Belt objects to the planet list, forcing widespread changes to textbooks and scientific classification and complicating how astronomers name and prioritize targets.