It’s normal to choose favourites for everything the way you’d choose your favourite ice cream, even if it’s effectively irrelevant. Favourite colour, favourite season, favourite planet. The latter, of course, is Pluto. A mysterious, frozen landscape spinning so far from here even the centre of the universe seems closer (but that is wrong, for the record.)
In 2006 the International Astronomical Union (IAU), a collection of stuffy jerks who probably don’t even like ice cream, suddenly announced that Pluto is not a planet. Why? Apart from the stuffy jerk thing, the truth is “a planet” had not been properly defined before this. I guess for the first few thousand years of stargazing it seemed obvious enough to say “big spherical thing spinning around a star” without writing that down.
So Pluto was no longer a planet, specifically because it hadn’t cleared its orbit of debris. It was a dwarf planet, which sounded a lot to me like the IAU’s way of saying “Okay guys, we know you’re going to hate this, so we’re going to keep planet in its designation anyway, because we’re tired of never being invited to parties, and we do like ice cream a little bit, well, we like frozen yogurt, that’s nearly the same thing.” And the kerfuffle settled for a decade.
This week two astronomers have announced a new ninth planet far, far beyond Pluto, at a distance of 200 to 1200 AUs (1 AU = the distance from Earth to the sun) compared to Pluto’s puny 40 AUs. Astronomers have been announcing a possible Planet X for most of my lifetime, but this time it’s more or less confirmed. And it’s exciting. Very exciting. I should be over the moon (ha!) but I find myself irrationally resistant to the hype. One of the astronomers who found this new planet is the very same who made the discovery that led to Pluto’s reclassification as a dwarf planet. He’s even quoted as saying, “Killing Pluto was fun.”
It’s normal to feel defensive on behalf of a frozen ball of dirt 6 billion kilometres away, right?