Pluto is a Planet

Of course, like everyone, I caught the headline this morning:

Astronomers say Pluto is not a planet – Yahoo! News

I have mixed feelings about this. On the one hand, it’s nice to see people who probably cannot even name all nine planets interested in a story about cosmology and the way we define our neighborhood in the galaxy. On the other, this entire debate to me seems to be missing the point – “planet” is hardly a technical term, which is why they can’t really figure out how to define it. However, the term “planet” does inspire children to look up in the stars, realize that there are different things out there, and most importantly realize that our entire world is really just a small little ball, whirling around in space.

How many children have been excited about the prospect of discovering the “10th planet”? I remember books from the 80s, talking about “mysterious tugs” on the orbit of Neptune, and even conjecture that “something else” might have pulled Pluto & Charon away from Neptune.

Demoting Pluto doesn’t inspire anyone. When the press dies down, in roughly a week, it’ll become an obnoxious fact – a fact that only the most annoying people will bring up every time they go to a classroom, museum, or other location that still shows all nine planets.

What they should have done, instead, is find a way to make Xena the 10th planet, leave Ceres in the asteroid belt, and highlight Charon & Pluto as a unique “double planet”. That would have been inspiring.

BTW I haven’t found any technical journal reporting detailed enough to explain to me why, if the new requirement is that a planet has “cleared its orbit”, why Neptune is a planet and Pluto isn’t… seems to me that Neptune hasn’t cleared it’s orbit either, since Pluto crosses it. The whole idea that Pluto crosses Neptune’s orbit as a reason for demotion seems specious.

5 thoughts on “Pluto is a Planet

  1. How about a compromise, borrowed from the biological discipline of taxonomy?
    We could say that _sensu latu_, or “broadly speaking,” Plato is still a planet — along with the other “dwarf planets” of the new IAU definition.
    However, only the eight “planets” of the new definition would be considered planets “strictly or narrowly speaking,” or _sensu strictu_.
    In biology, the sensu strictu/sensu latu distinction accommodates situations where a given species of mushroom, for example, might come to be defined more narrowly, like “planet” under the new IAU decision; but historical usage is still influential and merits recognition.
    Another term for the eight planets in the narrow sense that I like is “major planets,” maybe a bit more familiar and evocative than the proposed “classical planets” of what became the minority position among those who took part in the final vote.
    From an historical perspective, I like the reinstatement of Ceres as a “dwarf planet,” and in my view also a planet broadly speaking (as it was regarded when discovered in 1801); and a definition which would recognize Pluto and Charon as making up a “double planet” system.
    A diplomatic solution of this kind, letting astronomy enrich itself by borrowing a nice distinction from a sister science, would do some justice to both sides in the debate, and retain the insights gained in the process.

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