Eight is Enough

I am greatly saddened to learn that Pluto's undeserved status as the ninth planet in our solar system is likely to be preserved by the International Astronomers Union. I fear that our scientists have allowed sentimentality to make this decision for them. When they spy through their telescopes at that far-flung icy chunk of rock with an overlapping orbit and a "moon" nearly as big as it is, they fail to see it for what it is: a jumped-up comet that got too big for its britches.

When Pluto was discovered in 1930 by Clyde Tombaugh, astronomers (amateur and otherwise) were wild to find and label new astronomical objects. Comet-hunters scoured the night sky, but to find a planet would be a far greater achievement. Is it any wonder that the standards for planethood were set rather low? The Oort cloud wasn't even hypothesized until two years after Pluto's discovery, so it didn't occur to these sky-watchers that big chunks of ice in far-distant orbits might not be noteworthy. They didn't begin to guess that the expanse of space beyond Neptune is brimming with comets. Should Pluto's status as one of the nearest and largest of these comets really qualify it for planethood?

The IAU's draft resolution dealing with Pluto is also the organization's first attempt (shockingly enough, considering its 87-year history) at defining what is and what is not a planet. If the resolution passes, a planet will be defined as any round object larger than 800 kilometers in diameter that orbits the sun and has a mass roughly one-12,000th that of Earth. Pluto just squeaks by, and I suspect the requirements were written with that intent.

Members of the International Astronomers Union, I implore you! Remove the veil of sentimentality from your eyes! See Pluto for what it is: an icy dwarf in trans-Neptunian orbit. When it comes to planets, eight is enough.

(Thanks to Jo for inspiring this post. We'll just have to agree to disagree.)