It's Been 20 Years Since Astronomers Decided Pluto Isn’t a Planet
Twenty years after the International Astronomical Union reclassified Pluto as a dwarf planet, the decision remains a subject of scientific and public debate. Experts note that our evolving understanding of the solar system and improved telescopic technology continue to shape how we define celestial bodies.
Why it matters
The classification of Pluto highlights the fluid nature of scientific definitions and how public perception often conflicts with evolving astronomical taxonomy.
Pluto lost its planethood for a very specific reason. Whether or not that’s a good reason depends on who you ask.
Read full bio August 24, 2026, 4:19 pm ET
Does this look like a planet to you? NASA/JHUAPL/SwRI Named for the ancient Greek god who presides over the afterlife, Pluto is now mostly known as the planet that lost its planethood 20 years ago. In August 2006, the International Astronomical Union, an organization that names and classifies celestial bodies, voted to reclassify what was once known as the ninth planet in our solar system.
Ever since that fateful vote, Pluto has been a dwarf planet. And two decades on, it’s still a controversial decision . Earlier this year, billionaire Jared Isaacman, who now serves as NASA Administrator, voiced his support for Pluto being recognized as a planet once again. Star Trek’s William Shatner isn’t happy about it either.
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