Will Pluto become a planet again? The ongoing debate

Is Pluto a planet? Scientists and the public have debated this question since its reclassification as a dwarf planet in 2006. In this livestream, astronomer Alan Stern of NASA’s New Horizons mission joins us, alongside astronomer Mike Brown, whose discoveries played a key role in redefining the outer solar system. Watch live on Wednesday, May 13, 2026, at noon CDT (17 UTC). The debate is on. Where do you stand on Pluto? Join the livestream and drop your thoughts in the chat. EarthSky’s Deborah Byrd will host. Watch in the player above or on YouTube.

Is Pluto a planet? The ongoing debate

For decades, Pluto was known as the ninth planet in our solar system. Then, in 2006, the International Astronomical Union officially reclassified Pluto as a dwarf planet, sparking controversy around the world. For many people, the decision felt personal. Pluto had been part of classrooms, textbooks, and popular culture for generations.

Today, the debate is far from settled. Many leading planetary scientists still disagree about how planets should be defined and whether Pluto deserves to regain full planet status.

In this special livestream, we speak with astronomer Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. Stern has long argued that Pluto should still be considered a planet and believes the current definition is incomplete.

We’ll also hear the opposing perspective from astronomer Mike Brown, whose discoveries in the outer solar system helped lead to Pluto’s reclassification. Brown is often jokingly referred to as “the man who killed Pluto,” though his work fundamentally reshaped how scientists understand planetary systems.

Together, these perspectives highlight one of astronomy’s most debated questions: what is a planet?

Also watch this video with EarthSky’s Deborah Byrd and astronomer Mike Brown: ‘I killed Pluto. Now I’m searching for Planet 9.’ Watch in the player above or on YouTube.

Bottom line: Will Pluto become a planet again, or remain a dwarf planet under current definitions? Scientists still disagree nearly two decades after its reclassification.

Read more: New Horizons visited Pluto 10 years ago

Read more: Kiss and capture: A new explanation for Pluto’s largest moon