Science Friday Should Pluto be a planet again?
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Apr 2, 2026 Dr. Amanda Bosh, executive director of the Lowell Observatory and planetary scientist who studies Pluto and Kuiper Belt objects. Alan Stern, planetary scientist and leader of the New Horizons mission who argues dwarf planets are planets. They debate the IAU’s 2006 decision, orbit-clearing and the dwarf planet label. They discuss New Horizons discoveries, Pluto’s active geology and why the debate keeps resurfacing.
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Scientists Prefer Evidence Over Voting On Planets
- Many planetary scientists reject the IAU's 2006 vote and treat Pluto as a planet based on evidence rather than politics.
- Alan Stern argues scientists form consensus by evidence, not ballots, and most now include small rounded bodies like Pluto as planets.
IAU Vote Created A Problem Instead Of A Definition
- The IAU's 2006 definition aimed to limit the number of planets, which Alan Stern calls scientifically objectionable.
- Stern compares it to not legislating the number of elements and says voting in science misleads the public.
Orbital Clearing Is The Clause That Demoted Pluto
- The IAU's specific criterion that removed Pluto was the 'cleared its orbit' requirement.
- Amanda Bosh explains Pluto shares its region and resonance with Neptune, so it fails that orbital-clearing test.