Attention, IAU. You can officially bite me.
I'm still considering Pluto a “true” planet … whatever the hell that means. Why do we need a definition of a “true” planet, anyway? It's not like the Great Maker is going to be sitting there on judgement day informing us how close we came to the “correct” definition, and what fabulous prizes we have won as a result.
<picard>There are nine planets!</picard>
Or more. You can increase the number. Let's have dozens of planets! Sedna! Ceres! Xena! Even Quahogg, or whatever the hell it is called.
But it's too late to have less than nine. You can't decrease the count without a very good reason, and I don't think this qualifies. Something like “Pluto? That's no planet; it's a SPACE STATION!” might work…
The IAU definition relies on an arbitrary distinction, so I have no issues with making my own (just as arbitrary) distinction. A body can be considered a planet if, in order of importance:
Some additional factors, which are neither definitive nor required, but do increase the qualifications, are if:
A body can be both a moon and a planet.
If it was ever widely considered a planet for a period of not less than twenty (20) years after the start of the twentieth century, it is grandfathered in until such time as the Millenium Falcon reports back that it turned out to be a giant space station after all.
I also note that the line between planets and other celestial bodies is (and probably always will be) fuzzy. The universe is a strange place, and when it comes down to it, all we are doing here is saying that we'll call one lump of matter X, but that a different lump of matter isn't really X.
Incidentally, “dwarf” is an adjective, just like “jovian” and “terrestrial”. If we are going to say that dwarf planets aren't really planets, then shall we say that the gas giants are truer planets than Earth?
I think it makes a lot more sense to say “Yeah, there's lots of planets out there. We'll teach the terrestrial and jovian planets, but as for the dwarf planets … they're obviously planets — just look at the name — but there's just too bloody many to cover them all. Except the ninth planet, Pluto. We stopped counting after that.” It'd piss a lot less people off, I think.
There is a growing controversy over the IAU's decision (not surprised in the slightest). Including the fact that only a single-digit percentage of the IAU actually participated in the vote. And, of course, this…
From BBC news:
Dr Alan Stern, who leads the US space agency's New Horizons mission to Pluto and did not vote in Prague, told BBC News: “It's an awful definition; it's sloppy science and it would never pass peer review - for two reasons.
“Firstly, it is impossible and contrived to put a dividing line between dwarf planets and planets. It's as if we declared people not people for some arbitrary reason, like 'they tend to live in groups'.
“Secondly, the actual definition is even worse, because it's inconsistent.”
One of the three criteria for planethood states that a planet must have “cleared the neighbourhood around its orbit”. The largest objects in the Solar System will either aggregate material in their path or fling it out of the way with a gravitational swipe.
Pluto was disqualified because its highly elliptical orbit overlaps with that of Neptune.
But Dr Stern pointed out that Earth, Mars, Jupiter and Neptune have also not fully cleared their orbital zones. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path.
Read the rest here