Imagine living on a South Pacific island and naming all aquatic life in your lagoon “fish.” But your definition was so specific it didn’t apply to whatever creatures lived in the rest of the ocean.
This is what the International Astronomical Union (IAU) did in 2006 when they passed a new definition for “planet” that demoted Pluto to a “ dwarf planet” (later dubbed “plutoid”) in a highly publicized public relations SNAFU.
According to a strict interpretation of the IAU definition of a planet we’re stuck with eight major planets in the entire galaxy. No, wait, the entire freaking universe! No more, no less. Not ever, not never.
Why? Because the IAU definition ignores the over 400 planets to date that have been found orbiting other stars. This month alone 25 new exoplanets were announced at the meeting of the American Astronomical Society in Washington D.C.
The dirty little secret is that the Pluto-antagonists needed the vote of the exoplanet research community to pass their Pluto-is-not-a-planet resolution. Therefore they steered clear of making any judgments whatsoever about anything dealing with the practical infinity of worlds around the 100 million other stars in our galaxy.
My colleague Marc Buie of the Southwest Research Institute in Boulder, Colorado –a lifelong Pluto hugger and top researcher – emphasizes that as of today, we do not have a “planet definition” that could work for objects elsewhere in the universe.
This makes the IAU’s definition of a planet meaningless and irrelevant. And it has painted its supporters into a corner.
Last week Buie and co-investigators on NASA’s New Horizons mission to Pluto meet at the Johns Hopkins Applied Physics Lab near Columbia, Maryland to plan for the brief rendezvous and flyby in July 2015. They also celebrated the halfway point on the New Horizons odyssey (actually there are several midway points this year: when the spacecraft is equidistant between Earth and Pluto, and then equidistant between the sun and Pluto).
The IAU demoted Pluto because it has not gravitationally swept out its orbit of other Kuper belt debris from the solar system’s early days. “Can it be proven that the Earth was, in fact, responsible for clearing out its orbit zone? “ Buie asks.
What’s more it will be a very long time, if ever, that we know if exoplanets lie in cluttered orbits or not. Nor will be know if exoplanets are perfectly round – another IAU prerequisite for the Planet Club membership.
What we do know is that exoplanets defy anything found in the solar system. Many have very elliptical orbits (like Pluto). Their orbital planes are tiled at odd inclinations (like Pluto). They can be made of water, molten iron, even diamonds, and some smolder at temperatures hotter than a light bulb filament.
The IAU definition puts a lower limit on planet size (Pluto has been picked on for being puny) but sidesteps the thorny question of how big a planet can be, considering we have objects around other stars that are 10 -15 time Jupiter’s mass.
The Pluto debate could have engaged the public in a spirited exploration and celebration of the diversity of other worlds in the universe. Instead, the deadly boring and pedantic IAU crowd only succeeded in making the universe a little more dull, confusing, and joyless for adults and children alike.
But that’s only if we let them. Science is not a democracy where the one with the most votes wins. The truth is the planetary community is far from a consensus on Pluto’s planethood. What's more, It is exceptionally odd for a select group of scientists to try and re-define so fundamental scientific concept as “planet” – which goes back to antiquity. Regrettably, educators that I talk to feel duty-bound to honor the IAU promulgation, despite it meaninglessness.
I’m confident that the New Horizons flyby will reinvigorate public attention on Pluto when they see detailed views of a dynamic planet with atmospheric and seasonal changes and a complex geography, as experts anticipate.
In the time it took you to read this piece, the New Horizons probe swept 1,000 miles closer to Pluto. Stay tuned.
Tags: Meetings, Pluto, Skepticism, Spaceflight
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