The evolutionist astronomer at the Vatican has been replaced, too.

I was always taught

"Many very early men jump sticks until noon period."

Well, I never did like the word "period" at the end, so now the mnemonic works just fine and doesn't have that dangling work that I despised anyway.

"Many very early men jump sticks until noon."

Period.

and I meant "that dangling WORD"... oh well.

Pluto got the boot because it doesn't have enough mass to maintain a spherical orbit around the sun -- its orbit interferes with that of Neptune.

Hate to be a nitpicker, but there's no such thing as a spherical orbit, or even a circular one -- they're elliptical. And all planets interfere with one another; that's how Uranus and Neptune were discovered, after all.

Yes, wahoo, but of the nine planets, only Pluto's orbit crossed that of another planet. Such a feature is common among comets, asteroids, and other objects, but until now only Pluto among planets. Of course, it's all semantics. Essentialist or typological thinking rarely aids the scientific understanding.

Speaking of "crossing" Neptune's orbit is an exaggeration as well. That's only true for a plane projection of the Solar System as seen from "above" (perpendicular to the ecliptic), something useful for textbooks but not reflective of reality. The orbits don't actually intersect.

What you mean is that sometimes Pluto is closer to the sun than Neptune is, because its orbit is further from circular than the other planets. Again, just a semantic nitpick.

I think that the definition of planet should have nothing to do with orbit and everything to do with size, mass, spherical shape, and what it's made of.

I think that the definition of planet should have nothing to do with orbit and everything to do with size, mass, spherical shape, and what it's made of.

Composition is irrelevant, spherical shape is one of the requirements, size is a function of mass, and mass itself is covered under the requirement that its heavy enough to form a sphere and clear its neighborhood (be the dominant body within its region). Clearing its neighborhood is something that Ceres and Pluto fail to do by most accepted standards.

Remember Ceres was classified as a planet until scientific instruments were powerful enough to discern the other objects in the asteroid belt. Pluto has now been found to be part of a second asteroid belt known as the Kuiper belt.

As Chuck points out this is semantics, and the IAU doesn’ have a grudge against Pluto, there became a need because suddenly they can see Sedna, 2003UB313 (Xena), Quaoar, and 2005 FY9. They aren’t really asteroids since they are round, but they don’t fit what people currently accept as a planet since they are clearly part of a cloud of other bodies. So you create a new definition so they can go about putting these objects into those categories. “Unfortunately” Pluto fits the new definition better than it fits with where the line was drawn for planet.

Somehow I think I'll be able to sleep and maybe even learn the locations of the other dwarf planets.

I threw in composition to cover all bases, as unlikely as it is that we'll discover something planet-sized quite different from the gas giants and spherical rocks we're familiar with. I sure hope we never find a comet that big...