When is a planet not a planet? When it gets downgraded after 75 years, apparently. But was Pluto’s fate a mistake by the IAU, or an example of science in action? Marcos Huerta joins Antony to talk Kuiper belt objects, the New Horizons probe, and arbitrary astronomical definitions. "Pluto" Antony Johnston with Marcos Huerta Show Notes & Links Pluto "The Pluto Files" with Neil deGrasse Tyson NASA team and the "not yet explored" stamp "NASA probe passes Pluto, carrying ashes of man who discovered it" "To Planet 9 — and Beyond!" "Neptune All Night" video playlist