Pluto – Enough Already

There’s rebellion in the ranks of amateur astronomy. Despite the IAU’s notorious demotion of Pluto in 2006, many refuse to accept the validity of their new definition. OK, when Clyde Tombaugh discovered Pluto in 1930, if he’d known what we know today about dwarf planet objects, perhaps we’d all be calling the ninth planet a “dwarf planet”. But we didn’t know anything about Eris, Quaoar or other near-planetary objects back then, and you don’t define a new class of objects based on knowledge of only one instance.

Dwarf Planets

Dwarf Planets - click image for website link

IAU Definition:

What constitutes a planet? The International Astronomical Union (IAU) developed some definitions in 2001, modified them again in 2003, and as of August 24, 2006, the IAU has come up with another definition. The IAU said in a statement that the definition for a planet is now officially known as “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape and (c) has cleared the neighborhood around its orbit.”

David Grinspoon writes, in an excellent analysis in his column “This Is Not A Planet? (Sky&Telescope March 2009):

But the IAU has no such authority. They name objects and surface features. Should they redefine categories and words, especially those with widespread cultural and historical resonance? If the IAU adopts a clearly flawed definition, nobody is under any obligation to accept it.

There it is, buried in the second sentence of the excerpt: the rebellion has swollen beyond the world of astronomy to the mass media and general public. Cutting to the chase, it’s clear few in our society really care what kind of object the IAU thinks Pluto is. It’s a planet.

Supposing the prestigious Geological Society of America came up with a new definition of “mountain”? How would that work?

Mountains (elevations above mean sea level)


Half Dome


Half Dome - click image for website link

Half Dome - click image for website link

 Half Dome is a granite dome in Yosemite National Park, located at the eastern end of Yosemite Valley — possibly Yosemite’s most familiar sight. The granite crest rises more than 4,737 ft (1,444 m) above the valley floor. This view is from Glacier Point showing Half Dome and the valley floor below.
elevation: 8,836 ft
height above valley floor: 4,737 ft


Mt. Whitney


Mt. Whitney - click image for website link

Mt. Whitney - click image for website link

 Mount Whitney is the highest summit in the contiguous United States with an elevation of 14,505 feet (4,421 m). The granite that forms Mount Whitney is part of the Sierra Nevada batholith.

Shown is the East Face as seen from Whitney Portal.

elevation: 14,505 ft


Stowe Mountain, Vermont


Stowe Mountain, Vermont - click image for web link

Stowe Mountain, Vermont - click image for website link

Stowe Mountain Resort is a ski resort in the town of Stowe, Vermont in the Northeastern United States. It comprises Mount Mansfield and Spruce Peak. Mount Mansfield, the location of the intermediate and advanced ski trails, is the tallest mountain in Vermont.

elevation: 3,719 ft
base elevation: 1,559 ft



As anyone in the IAU could tell you, any serious definition of “mountain” would have to enable us to distinguish clearly between a “mountain” and a “hill”. How could a mountain that was not as big as a rock be a mountain? Yet even awesome Half Dome isn’t a “mountain”, it’s a rock or “dome”. Compared to the really big western peaks, Half Dome rises slightly less than one mile of clean, fresh air above the Yosemite Valley floor. Mt. Whitney rises almost three miles above Death Valley, just 76 miles to the East.

New England’s Stowe Mountain isn’t even a mountain, it’s a place. Its “mountains” consist of Mount Mansfield and Spruce Peak, Mount Mansfield reaching a mere 2,160 feet above its “base” elevation. How can this place be a “mountain”?

According to Wikipedia, the Vermont division of FDR’s CCC cut the first trails on Mount Mansfield in 1933.The National Ski Patrol was based on the Mount Mansfield Ski Patrol , the oldest in the nation.

Again according to Wikipedia, “Eastern mountains were generally formed some 300 million years ago, marking the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangaea.”

The Sierras were formed in the Triassic period some 251 to 199 million years ago. An extra 100 million years accounts for a lot of erosion and the generally milder stature of the Eastern landmark peaks.

 Try this “it’s not a mountain” argument with several generations of New England skiers. They’ll tell you the same thing we’re telling the IAU. It’s a mountain, just like Pluto’s a planet. No amount of academic internecine warfare is going to change that.

Enough, already.

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2 thoughts on “Pluto – Enough Already

  1. Pingback: Pluto, Once and Future Planet | Astronomy

  2. Hello
    That critique on PLUTO\WHAT IS A MOUNTAIN? and the IAU is timely.
    We at SPACENOW.COM have managed to image Pluto and made a stunning discovery.We immediately reported to the IAU and even had a meeting with them regarding the gigantic mountain that exists there.
    Currently we are finishing both Pluto’s and Charon’s full rotation.
    Apparently, their mutual gravitational tug is responsible for these enormous surface features.Charon,as a matter of fact,has at least one gigantic mountain as well.This will soon be out on SPACENOW.

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