Saturday, August 26, 2006

International Astronomical Union to Pluto: "You cold busted."

Alas, poor Pluto.

After about 75 years of being the ninth planet, everyone's favorite celestial snowball got busted down to dwarf planet status. Now we're left with Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune as official planets.

I've seen some complaints about how the old mnemonic we learned in school -- along the lines of "My Very Educated Mother Just Sent Us Nine Pizzas" is now obsolete.

I always found it easier to, I dunno, remember the actual names of the planets. I think I was a weird kid, though.

I'm not against mnemonics; they're pretty handy. I've always been partial to "Eskimos Go Bananas Drinking Fresca" over "Every Good Boy Does Fine." You can guess how long ago my music class was based on the inclusion of "Go Bananas" and "Fresca."

In old issues of "The Flash," one of the enemies -- The Rainbow Raider -- was named Roy G. Bivolo. I read about that long before I learned about Roy G. Biv representing the colors of the natural spectrum.

My friends and I came up with quite a few mnemonics in my high school science classes, most of which I'm, uh, not at liberty to share, if you know what I mean.

Am I bummed out about Pluto getting sent down to the minors? No, not really. I always thought it had a goofy name (So to speak; the cartoon dog was named after the planet, according to Wikipedia). Besides, it's going to be decades before Pluto is removed from the collective knowledge pool of the general public.

If nothing else, it will be the best-known dwarf planet, which admittedly is sort of like being the coolest nerd (so I hear), but it's something.


  1. Instead of "My Very Educated Mother Just Sent Us Nine Pizzas"

    you can use:
    "My Very Educated Mother Just Sent Us Nachos"

  2. Pluto IS a planet because unlike most objects in the Kuiper Belt, it has attained hydrostatic equilibrium, meaning it has enough self-gravity to have pulled itself into a round shape. When an object is large enough for this to happen, it becomes differentiated with core, mantle, and crust, just like Earth and the larger planets, and develops the same geological processes as the larger planets, processes that inert asteroids and most KBOs do not have.
    Not distinguishing between shapeless asteroids and objects whose composition clearly makes them planets is a disservice and is sloppy science.
    As of now, there are three other KBOs that meet this criterion and therefore should be classified as planets--Haumea, Makemake, and Eris. Only one KBO has been found to be larger than Pluto, and that is Eris.
    The IAU definition makes no linguistic sense, as it states that dwarf planets are not planets at all. That’s like saying a grizzly bear is not a bear. Second, it defines objects solely by where they are while ignoring what they are. If Earth were placed in Pluto’s orbit, by the IAU definition, it would not be a planet. That is because the further away an object is from its parent star, the more difficulty it will have in clearing its orbit.
    Significantly, this definition was adopted by only four percent of the IAU, most of whom are not planetary scientists. No absentee voting was allowed. It was done so in a highly controversial process that violated the IAU’s own bylaws, and it was immediately opposed by a petition of 300 professional astronomers saying they will not use the new definition, which they described accurately as “sloppy.” Also significant is the fact that many planetary scientists are not IAU members and therefore had no say in this matter at all.
    Many believe we should keep the term planet broad to encompass any non-self-luminous spheroidal object orbiting a star.
    We can distinguish different types of planets with subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc.
    We should be broadening, not narrowing our concept of planet as more objects are being discovered in this and other solar systems.
    In a 2000 paper, Dr. Alan Stern and Dr. Hal Levison distinguish two types of planets--the gravitationally dominant ones and the smaller ones that are not gravitationally dominant. However, they never say that objects in the latter category are not planets.
    I attended the Great Planet Debate, which actually took place in August 2008, and there was a strong consensus there that a broader, more encompassing planet definition is needed. I encourage anyone interested to listen to and view the conference proceedings at You can also read more about this issue on my blog at