Why Pluto Might Be A Planet Again: An Explainer

Pluto, in 2006, was booted from the list of planets, much to the objection and consternation of the general public. But as Tyrion has taught us, dwarfs have a tendency to overcome adversity, and Pluto might be back on the planetary roster. Here’s why.

Wait, why is Pluto no longer a planet?

The basic problem, at least back in 2006, was that Pluto is arguably just another lump of ice floating in what’s known as the Kuiper Belt, essentially a ring of debris on the outer edge of the galaxy. It’s not even the biggest object in that galactic space dump, actually; in 2005, Eris was discovered, and it’s bigger than Pluto. Pluto’s weird scientific history also really doesn’t help.

…Pluto has a weird scientific history?

Oh, yeah, in fact the guy who found it is arguably the Don Quixote of modern astronomy. The man who found Pluto was Percival Lowell, who spent most of his astronomy career arguing there once was, or still was, intelligent life on Mars due to canal-like structures he observed, something that was thoroughly disproven in his lifetime. He also saw features on Venus that were actually his own retina.

And, in fact, although he spent the last decade of his life searching for Pluto and his observatory ultimately found it, it later turned out that all his work proving Pluto existed was completely wrong. So when your main discoverer is a terrible scientist and a kook, it does not help you win friends when you’re a would-be planet.

So… what changed?

The Harvard-Smithsonian Center for Astrophysics recently hosted a debate about what makes a planet, which was recounted by Astrobiology Magazine. The main issue we have to consider is that we keep finding exoplanets, and that “planet” is as much a cultural definition as it is a scientific one. If we’re declaring any rock we find in another solar system a planet… why doesn’t Pluto make the cut?

Also, the panel put it to a vote, and a bunch of nerds said Pluto was totally a planet. So there’s that.

So can I start using the mnemonic I learned in grade school again?

“Mary’s violet eyes make Johnny stay up nights plenty?” I wouldn’t teach that to kids. That’s kind of gross. You know Johnny’s doing something unseemly.

Anyway, not yet. This was a mostly unofficial poll and is the result of one debate. But there were some fairly heavy-duty scientific minds on the panel and in the audience, so expect the issue to be revisited, and soon.