Thursday, August 24, 2006

Pluto no longer planet; still Mickey's dog

Ending decades of controversy, the International Astronomical Union today redefined the term "planet." Pluto, considered the most distant planet in the solar system for the past 75 years, no longer qualifies.

That makes the score Planets 8, Pluto 0.

I know that some of you are yawning "Who cares?" at this bit of news, but for those of us interested in astronomy — and I was quite the astronomy buff in my younger days (the science, not the Blue Öyster Cult song) — the demotion of Pluto is big news. Stargazers have argued for years over whether Pluto, a rogue ice ball with an elliptical orbit inhabiting the outskirts of our sun's gravitational pull, really fits the traditional view of what a planet is. Now it's official: It doesn't.

Fasten your seat belt. It's about to get astronomical up in here.

This whole imbroglio started in 1930, when astronomer Clyde Tombaugh discovered the celestial body known today as Pluto. Tombaugh's find ended more than 80 years of intensive observation by scientists searching for a ninth planet beyond the orbit of Neptune, a search spawned by irregularities in Neptune's orbit that were thought to be caused by the gravitational effects of another large body roughly Neptune's size. When Tombaugh identified the pinpoint of light he dubbed Pluto (choosing a name that began with the initials of Percival Lowell, an earlier astronomer who had devoted much of his career to the ninth planet hunt, and who founded the observatory where Tombaugh worked), the mystery appeared to have been solved.

Except... not.

As happens on occasion in science, the smart guys had messed up. Astronomers initially miscalculated the size and density of Neptune, leading them to perceive that its orbit was being affected by a huge nearby planet. Later research determined that the perceived discrepancies in Neptune's orbit were accounted for by a more accurate determination of its mass, and not by Pluto, which turned out to be a piddling little thing (about two-thirds the size of Earth's Moon) rather than another ice giant like Neptune or its neighbor Uranus. Oops.

Matters grew even more complicated in 1978, when astronomers learned that Pluto had a moon of its own, now known as Charon. Given that Charon is approximately half the size of Pluto, some scientists thought the duo should be classified as a "double planet," or that perhaps Charon should be considered a planet in its own right. (We now know that Pluto has at least two other, smaller satellites, Nix and Hydra.)

Thus, a slope became slippery. If tiny Pluto could be called a planet, and maybe Charon also, what about Ceres, the largest object in the asteroid belt that lies between Mars and Jupiter? And what about the recently discovered, but as yet officially unnamed, bodies that share Pluto's realm in the Kuiper Belt on the solar system's outskirts — objects popularly known as Xena (official designation: 2003 UB313), Sedna (90377) and Quaoar (50000)? If the International Astronomical Union had adopted one of the proposals under consideration before today, the number of solar objects called "planets" could have skyrocketed into the dozens, perhaps hundreds.

Instead, the astronomical community made the smart move: They determined that it was a mistake to have listed Pluto as a planet in the first place. Instead, Pluto is now officially a dwarf planet. The new definition of planet (of the non-dwarf variety) states that such an object must "clear the neighborhood around its orbit." In other words, objects that share relative space with numerous similar objects — as Ceres does in the asteroid belt, and as the Pluto-Charon duo does out in the solar suburbs — aren't true planets.

So, after 75 years, we're back to an eight-planet solar system, with numerous dwarf planets floating around among and beyond the Big Eight. Just imagine an octet of Snow Whites, surrounded by a horde of little Sneezys, Dopeys, and Docs.

God's in His heaven, and all's right with the universe.

What exactly this all means about the status of Goofy, however, remains unclear.


2 insisted on sticking two cents in:

Blogger Janet offered these pearls of wisdom...

It seems everyone beat me to the Pluto punch today. Do I even dare publish the post about Pluto I have floating around my brain, but have yet to write?

6:50 AM  
Blogger SwanShadow offered these pearls of wisdom...

Dare, Janet. Dare.

9:33 AM  

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