Ice, Ice Baby
Via Elizabeth Bear on Twitter, the latest in the kerfuffle regarding whether Pluto is a real planet or not.
You know, here’s the thing for me. Despite having a famously pro-Pluto daughter and also personally thinking the actual mechanics behind the Pluto demotion were a bit mean and not entirely rational, I have no problem in scientists pointing out the obvious, which is that Pluto is not at all like the other planets in the system. It’s just not: its orbit is too eccentric, its composition is too undifferentiated, and its just plain small. Just not like the other kids. Fine.
However, where the International Astronomical Union went all screwy was in deciding to name Pluto, and objects of its icy ilk as a “dwarf planet.” Yes, it’s small. But you know what, sooner or later it’s inevitable that we’re going to find a “dwarf planet” out there in the Kuiper Belt that’s larger than Mercury, which is not a “dwarf planet.” And then the IAU is just gonna look dumb.
What they should have done is this: Simply say there are different categories of planets. There are rocky (terrestrial) planets, which in our system are Mercury, Venus, Earth and Mars. There are gaseous (jovian) planets, which in our system are Jupiter, Saturn, Uranus and Neptune. And then there are icy (plutonian) planets, which in our system are Pluto and Eris and very likely whole damn bunch of other ones out there past Neptune. And then, having admitted that there is this indeed this third (non-dwarf) category of planet, the IAU could admit this: Hey, there are in fact so many damn icy planets out there that it doesn’t make sense for the average person to try to learn them all, so let’s just stick to the rock and gas planets as the ones they need to know, and appoint Pluto as the token icy planet representative that the kids learn about in school.
Now, really, how hard would that have been? I say not at all. But no, the IAU had to go demoting. Silly, silly scientists. They’re gonna regret it.