Friends, today we come together to observe the tenth anniversary of that fateful day that the International Astronomical Union delivered a one-two punch that left many of us flabbergasted. The fact that prior to that meeting, there had been no universally agreed upon definition of a planet, was a doozy of a left jab. Pluto’s demotion was the right cross that rattled our core assumptions about our environs and shattered beloved mnemonics. Suddenly, My Very Energetic Mother went from Just Serv[ing] Us Nine Pizzas, to Just Serv[ing] Us Nine. Nine what?! How does one serve “Nine”? Beyond the loss of those delicious pizzas that were the subject of many pre-lunch daydreams in elementary school, August 24th, 2006 brought us to the brink of an existential crisis: everything we knew was a lie. If Pluto’s planethood had been a lie, what else might be a total fabrication? Is water actually wet? Will paleontologists change their minds about the brontosaurus again? Is this the real life? Is this just fantasy? Are we all living in The Matrix?
Yes, friends, it was hard to accept that our solar system models painstakingly built with painted Styrofoam balls the night before they were due in our third grade science classes were now wholly inaccurate. We looked at Science and wondered what the hell was going on over there—I mean, how could there not be a standard definition of a planet? How is that something that Science looked at for centuries and decided to just wing? We looked up at the heavens and shouted, “It’s like I don’t even know you anymore!” (Well, maybe that was just me.)
In order to be defined as a planet, according to this shiny new definition, an object must orbit the sun, be massive enough to take on a spherical shape under its own gravitational force, and it must clear its orbit—either by kicking objects out of its orbit with its gravity, or by absorbing those objects into itself. While Meatloaf claims that “Two Out of Three Ain’t Bad,” the International Astronomical Union is a stickler for silly things like consistency and precision and, because it did not meet that final criterion, Pluto was shown the door.
In the throes of our solar system redefining revelation, those of us who are not intimately engaged with astronomy forgot something. Though our historical amnesia would tell us otherwise, Pluto wasn’t the first celestial body to sneak into our planetary night club with a fake ID: in 1801, over a hundred years before Pluto was even discovered, Ceres was spotted and designated a planet. As science and technology progressed, it was discovered that Ceres was simply the largest body in the asteroid belt between Mars and Jupiter and its planetary designation was stripped away as it was reclassified as an asteroid.
In spite of our sentimentality, Pluto’s redesignation is just a product of Science being science-y in the best way. Because the goal is to always advance and bring nuance to our understanding of our universe, I submit to you, dear friends, that the acceptance of a standard definition of a planet—and Pluto’s subsequent demotion—was a wonderful and necessary leap forward. The pang of loss felt at Pluto’s ejection from the club was simply growing pains. In fact, the new category in which Pluto finds itself—dwarf planets—leaves Pluto far less isolated than when it was lumped in with the planets. Ceres, Eris, Makemake, and Haumea are Pluto’s new squad.
So, really, it’s not so bad. It’s actually pretty cool. I forgive you, Science, and I hope you’ll forgive me for the things I said when I was mourning my previous worldview (and also while I was hungry; I really wanted those pizzas). And I’d like to extend a really big high five to the IAU because that new definition gave Pluto and its new squad the chance, like a phoenix rising from the ashes, to bestow us with this glorious mnemonic to remember our neighbors in the solar system: