In this episode of Learn Something, we unravel the fascinating story of Pluto — its rise, fall, and the controversy that still surrounds it. Once known as the ninth planet in our solar system, Pluto captured the imagination of generations before being reclassified as a “dwarf planet” in 2006. But why did this happen, and why is the debate still ongoing?

We trace Pluto’s journey from its discovery by Clyde Tombaugh in 1930 to its demotion by the International Astronomical Union (IAU). The game-changing moment came with the discovery of other large Kuiper Belt Objects like Eris, prompting astronomers to rethink what makes a planet a planet. The IAU’s new definition required that a planet orbit the sun, be nearly round, and crucially, clear its orbital neighborhood — a criterion Pluto failed due to its crowded Kuiper Belt location.

But the story doesn’t end there. Prominent scientists like Alan Stern and Philip Metzger argue that Pluto should be a planet based on its rich geological complexity — including an atmosphere, methane glaciers, and potential subsurface oceans. They suggest planetary classification should focus more on what an object is rather than where it orbits.

We also explore how cultural sentiment, evolving science, and powerful images from NASA’s New Horizons mission have kept Pluto in the public eye. The episode dives into the broader implications of redefining planets, the politics of scientific classification, and how even historical accidents can shape what we teach and believe.

Whether Pluto is a planet, dwarf planet, or something in between, its story is a powerful example of how science evolves — and how curiosity continues to drive discovery.