Why did the few astronomers at IAU make a bad job of defining planet and dwarf planet? Because they disregarded the rules of the English language, and disregarded a lot of other astronomers' former use of the word planet.
What the IAU decision partakers (according to rumor, a group of angry planet dynamicists intent on making a power demonstration) did wrong was:
- claiming that dwarf means having cleaned up its own orbit by a committee decision;
- claiming that a dwarf-something is not a something – normally we speak about dwarf elephants being elephants, dwarf stars being stars, dwarf crocodyles being crocodyles – but the IAU decision partakers deliberately claimed that dwarf planets aren't planets, explaining that since minor planets aren't planets, they had the right to emulate a misnomer that emerged evolutionary by initial misconceptions; so that little IAU decision partaker clique decided to disregard the whole area of linguistics, by a committee decision;
- defining planets to be bodies going in orbit around Sun, nothing else; OK, so what about those exoplanets? Disregard! OK, so what about those rogue planets? Disregard! Like kings doing grandious gestures while the lowly rabble admires? No, not at all.
My conclusion: IAU cannot be trusted with such linguistic kind of questions – the members don't have the philosophical insight to understand that the long-term success of their science, is grounded in their ability to communicate with other scientists, and the public who pays their funds. The IAU definition of planet is nil, illegal, void, rubbish, nonsense. I'll use the term "dwarf planet" (bouahahaha!) only in order to lead people away from its usage.
(Whytheh*c did I write this here?? This is an encyclopedia)
- Lol, the way I see it, if the dang thing is round and doesn't have nuclear fusion then it's a planet. But it's hard not to think of Titan or Ganymede as moons, or Ceres as an asteroid, or Eris as a KBO though. We're too used to thinking this way. These terms are overlapping subsets of "planet", some examples are large enough to be planets even though most of them aren't. I'd say a brown dwarf is not a planet though, since if fuses deuterium. Sagittarian Milky Way 22:16, 30 March 2007 (UTC)
- Hi Sagittarian Milky Way! I share that opinion, approximately, except that by my opinion, a planet is or was melted/differentiated inside. That makes Titan and Ganymedes planets, and probably Ceres and Vesta, but that's about the lower bounds. I think, when IAUers speak of "planets", they mean what I would refer to as "regular (orbit) planets". This d*rnd conscious misnomer "dwarf planet" of theirs, refers to "irregular planets". In my opinion, a moon may also be a planet, but since it is not in an orbit aroun the Sun, a moon is never a regular planet, neither would Pluto nor Eris be properly classified as regular. Said: Rursus 11:10, 19 April 2007 (UTC)
This user is not a member of IAU, and would rather cut their right arm than ever be!
- for the inner circuit! Said: Rursus 15:06, 19 April 2007 (UTC)
- Right, there's good old regular planet, and then there's "others". This kindof makes it obvious: List of solar system objects by planetary discriminant
- Informative link. Then "dwarf planet" only lacks the linguistics wellformedness. Let's say "non-regular", but using the Soter Term, in what group falls the icy equipotential moons? "Dwarf planets"? Said: Rursus 17:36, 11 May 2007 (UTC)
- Moons and objects in resonance aren't counted against the body in question. You could do an analogous thing with each planet to seperate its major moons from the minor moons say, they might need to find all the really tiny moonlets though to make an accurate determination.
- I wonder what the definition of 'the orbit it has to clear' is exactly. Is it the body's Hill Sphere drawn out into a torus? Sagittarian Milky Way 02:32, 20 May 2007 (UTC)
A moon can never be a regular planet cause it's a moon. Doi. Like the forest moon of Endor, which must be around the size of Earth.
In comparative planetology you don't have to give a care about where it is and what it does, so they're like 57 round bodies or something. That's where you get the nice graphs of all the stuff like mass vs density. With the dots colored by iciness vs rockiness, and they put a slanted line for the limit of roundness. I saw that in Sky & Telescope once. So it's remarkable that there's like a line, and Mimas is barely above that line, it's the smallest planet, and something like Pallas which is almost twice the size might not be a planet because Pallas has no ice and so is harder to squeeze. The limit of roundness is sharper once density is taken into account.