The saga continues. Nobody yet knows how many planets we have. There has been fierce argument at the International Astronomical Union. As a result, the definitions of last week have been revised. “Pluton” has been discarded as a term (partly because of the clash with a geological term, a clash which was also swiftly noted by one of Asymptotia’s readers), and the vote is very soon.
Pluto and all the loveable little bodies might now in trouble because a revision to the definition says that a planet must be the “dominant body” in its orbital zone, clearing out any little neighbours. New Scientist’s website reports that
Pluto does not qualify because its orbit crosses that of the vastly larger Neptune.
Quoting further:
Terminology is still controversial. Objects that do not quite qualify as planets – because they are big enough to be round but not big enough to dominate their neighbourhoods – might become “dwarf-planets” or planetoids.
These would include Pluto and Ceres, the largest asteroid. And the small fry of the solar system, such as asteroids, might be called small solar system bodies, or retain their current designation as minor planets.
But a supplementary resolution would at least make Pluto the prototype of a class of icy outer worlds beyond Neptune. […]
It is not clear what they would be called, however – most early suggestions were rejected by an informal show of hands. Pluton, plutoid, plutonoid and plutid seem to be out of the running, as are “Tombaugh object” and “Tombaugh planet”, which had been proposed in honour of Pluto’s discoverer, Clyde Tombaugh. “Plutonian object” was the least unpopular choice.
Just so you get a sense of what’s going on in Prague, in this post are some lovely pictures of the proceedings that I got from their website. New Scientist’s site has some video of some of the heated debate.
I have to say, they’ve got a rather grand setting, looking more like the Golden Globes, Oscars, or Emmys than a scientific conference. (Click for larger). (I wonder if they’ll have fountains of chocolate, like at the LA Times Book awards. Hmmm…..)
Here’s a shot from the middle of the discussion about the new definitions (click for larger):
Exciting stuff. Let’s see what comes of all this. As soon as I find out the vote result, I’ll let you know. More on this at the Astronomy Blog.
-cvj
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Oops, inadvertently omitted a term… “cannot expect extrasolar planets”
It troubles me that the revisions made to the IAU’s original proposal have been constrained to defining bodies in our solar system rather than being applicable universally. Surely we cannot extrasolar planets to conform to whatever we find psychologically or culturally satisfying here in our cosmic neighborhood. I’d rather wait another three years for a more functional set of guidelines than see a resolution adopted shortsightedly.
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