Pluto Gets Demoted

There are too many things I was taught as "fact" when I was a kid that have changed since I've been out of school. That enormous plant-eating dinosaur with the really long neck and a really small brain isn't a brontosaurus anymore, it's an apatosaurus. And what's up with the velociraptor? I saw the movie, Jurassic Park, and wondered where the velociraptors came from. We must keep finding new dead things all the time.

Now that they've messed with all the dinosaur stuff they taught me, they're moving on to the Solar System.

The AP reported today that there's been a big astronomy confab going on in Prague, Czech Republic, and they're demoting the planet Pluto.

Leading astronomers declared Thursday that Pluto is no longer a planet under historic new guidelines that downsize the solar system from nine planets to eight.

After a tumultuous week of clashing over the essence of the cosmos, the International Astronomical Union stripped Pluto of the planetary status it has held since its discovery in 1930. The new definition of what is - and isn't - a planet fills a centuries-old black hole for scientists who have labored since Copernicus without one.

That's really a startling (to me) admission that astronomers never really knew what a planet is. But now they do.

Much-maligned Pluto doesn't make the grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.

Instead, it will be reclassified in a new category of "dwarf planets," similar to what long have been termed "minor planets." The definition also lays out a third class of lesser objects that orbit the sun - "small solar system bodies," a term that will apply to numerous asteroids, comets and other natural satellites.

Is somebody going to object to the term "dwarf planets" because it's size-ist?

Another surprise (to me) was that astronomers can be hot-headed. There was another plan offered at the conference that would have broadened the definition of a planet, thus adding a couple planets to the Solar System, rather than removing one.

That [broadened definition] plan proved highly unpopular, splitting astronomers into factions and triggering days of sometimes combative debate that led to Pluto's undoing. (emphasis added)

Fascinating. But the ramifications are enormous. All those models of the Solar System--the kind with the nine little balls on heavy wire circling around the Sun's big yellow ball--and all the maps and charts and textbooks will have to be redone. Even those pictures that make you realize how small you are should probably remove Pluto.

Maybe the astronomers are in the pay of textbook publishers, who haven't had a major update in a while...