In 2006 the International Astronomical Union (IAU) caused consternation when it declared that Pluto was no longer a planet. Several bodies of similar size had been found in the Kuiper Belt, so the IAU created a definition that included the criterion that a planet must “clear the neighborhood around its orbit,” which Pluto does not. Pluto was reclassified as a dwarf planet, in a move which upset anyone who grew up learning about a solar system consisting of nine planets.
Now, NASA Administrator Jim Bridenstine has reignited the fierce debate over Pluto’s status by unexpectedly come out in favor of it being a planet. “Just so you know, in my view, Pluto is a planet,” Bridenstine said in a tongue in cheek clip posted to Twitter. “You can write that the NASA Administrator declared Pluto a planet once again. I’m sticking by that. It’s the way I learned it. I’m committed to it.”
Inspired by Bridenstine’s bold move against the anti-planetary-Pluto establishment, Queen guitarist and astrophysicist Brian May weighed in on Instagram. “Not that I have any authority,” May began, typically humble, “but, for what it’s worth, I strongly agree. Pluto was discovered and named as a planet a while before I was born. At that time it was generally instinctively understood that a Planet was one of a family of roughly spherical objects that orbited the Sun (rather than orbiting something else). So, to me, Pluto is a classical PLANET. End of story.”
May went on to discuss how planetary categorizations work, arguing that we could equally well call Pluto the edge of the planetary zone, and anything beyond it a Kuiper Belt Object. He also pointed out the word “planet” comes from the Greek for “wandering star,” which just goes to show how definitions change over time as our knowledge of the universe grows.
May also gave a shout out to Alan Stern, the planetary scientist who worked as Principle Investigator for the New Horizons mission to Pluto which captured stunning close-up images of the hotly debated body. Stern is known for, in addition to his scientific achievements, popularizing the nine-fingered “Pluto salute” to demonstrate his support for Pluto as a planet. If you agree with May, Bridenstine, and Stern, now you know how to show the world.