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"
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
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
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"
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.