Pluto: Denied!

Pity the poor little planet that almost was, Pluto. The stellar body was only discovered less than 100 years ago... is named for the God of the underworld... and has the dubious honor of having a Disney character named after it. For years, astronomers have criticized the classification of Pluto as a planet, saying the small orbital body is little more than a cosmic straggler in Earth's solar system.

Well... at a meeting of leading astronomers in Prague to finally come to a definition of just what, exactly, constitutes a planet... they decided that Pluto wasn't, and stripped it of its planetary status for good. The historic vote by the International Astronomical Union officially shrinks Earth's neighborhood from the traditional nine planets to eight.

And what, you may ask, is so great about those "classic" planets?

According to the new definition, they are all celestial bodies that orbit a sun, have sufficient mass for their own gravity to cause the bodies to assume a nearly round shape, and their orbits do not intersect with those of neighboring planets.

It's that last point that led the ninth rock from the sun to fall from planetary grace... as Pluto's oblong orbit overlaps with Neptune's.

So as of Thursday... Pluto is now a "dwarf" planet, along with past planetoids (formerly termed "minor" planets) that meet the first two standards. Moons will still be classified as a separate category -- and most asteroids, comets and other small objects will be called "small solar-system bodies."

Got all that?

"NASA will, of course, use the new guidelines established by the International Astronomical Union," said Dr. Paul Hertz, Chief Scientist for the Science Mission Directorate at NASA Headquarters. "We will continue pursuing exploration of the most scientifically interesting objects in the solar system, regardless of how they are categorized."

That means the New Horizons probe, sent up in January on a multi-year mission to explore Pluto, will proceed on schedule...  albeit with, perhaps, a tad less glamour.

While many will lament the passing of Pluto as a planet... in the end, astronomers say, it was simpler this way... as classifying Pluto as a planet would have also allowed other celestial bodies to be termed as such -- possibly resulting in as many as 53 "new" planets.

Think of all the textbooks and encyclopedias that would have needed to be rewritten if THAT had happened... as it stands, all it will take to modify those books is a thick marker.

FMI: www.iau.org, www.nasa.gov