Pluto is a Planet
A reader with the minor but prophetic name of Zachariah penned a comment about the Ninth Planet, which I here reprint and salute:
I was so glad to hear that many of the people (including the director) of the New Horizons mission consider Pluto to be a planet. It’s always good to hear that sanity exists in some form in the government.
The IAU’s definition of what a planet is is just bad. For those who don’t know, in 2006 the International Astronomers Union (IAU) defined a planet as any body that meets the following criteria
1) is in orbit around the Sun,
2) has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3) has “cleared the neighborhood” around its orbit
This definition is bad on several points. The first criteria only applies to our solar system, meaning that according to the definition exoplanets are not planets. But lets ignore that for a minute, and just say that exoplanets aren’t planets, they’re their own thing. The first two criteria are generally accepted for our solar system.
The big problem is the 3rd criteria, as they never defined what “clear the neighborhood around the orbit” means. Does this mean that there are no smaller bodies (excluding moons) that share or cross it’s orbit? If so, then only Mercury could be called a planet. Does it mean that the planet makes up 99% of the mass of the objects in the orbit? That would exclude Earth as the Moon is about 1.5% of earths mass. What about if you have multiple bodies of roughly equal mass sharing an orbit (a Kelmperer Rosette) or a shared center of gravity (ie a double planet [odly enough, Pluto and Charon do this. So you could claim that they are our solar systems only double planet]).
The worst thing about the whole affair though is the method this definition was pushed through. It was brought up to vote as one of the last items of the last day of the annual when most of the people members of the IAU had left to catch their planes to return home. Only about 5% of the IAU members were still at the conference when the vote was brought up. They’re never brought it back up for reconsideration.
This whole thing was so poorly considered. I’m glad that not everyone in the fields of astronomy, planetary scientists or space in general don’t just march in lock step with it.
I would also like to thank our host for indulging me and letting me post the above screed.
My comment: I had not heard about the procedural irregularities (read: lawless) shenanigans of this conference. But I have been and am deeply offended on behalf of Clyde Tombaugh, who discovered a planet with meticulous scientific work, and yet one Mike Brown of Cal Tech, allegedly an astronomer — whose only contribution to the matter was a trifle of semantic logic chopping — deprived him of that glory.
No matter what definition is used to differentiate Pluto from the other fifty planets in the outer system — even assuming such a differentiation serves any scientific purpose — its status should be continued as a planet based on what lawyers call “grandfathering”.
Grandfathering is when one includes a clause exempting certain classes of people or things from the requirements of a piece of legislation or contract, in order not to diminish or adversely affect their previously established rights, privileges, or practices. If one buys a bowl of soup in a restaurant, for example, one minute before the owner announces a change in the price, the law would protect one’s right to buy the soup at the original price negotiated and agreed upon.
In the case of Pluto, maintaining continuity between science books, not to mention science fiction books, written before and after 2006, is more important, so as not to create unnecessary confusion and discord, than to maintain precision of Linnaean taxonomy.
To add insult to injury, even if continuity had to sacrificed to Linnaean clarity, that principle does not apply in a case where no clarity is present.
“Cleared the neighborhood about its orbit” …? Can we be more elastic and unclear, please? One might as well say “a planet is whatever I am pointing at when I say ‘Look! That is a planet!” ”
Pretending to demote Pluto from planet to “dwarf planet” deepens the ever deepening pit of disrepute and contempt the scientific community has been earning for itself ever since it loaned its waning prestige to crackpot political movements.
The scandal of peer-reviewed papers and articles that were never reviewed, or which contain merely rubbish, would be shocking, were the public ever to become aware of it.
Scientists with any sort of stones would have simply declared Eris to be the Tenth Planet, and so on. That outer planets are smaller is not a condition for classification.
If one wants to establish a limit on size, below which a planet is an asteroid or centaur, so be it. Draw the line at Pluto.
Since Pluto is larger than Eris, Makemake, Haumea, and Ceres, can anyone utter a non-arbitrary reason for calling him the largest of the “dwarf planets” rather than the smallest of the “planets”?
I have heard one wag saying the scientists wanted to spare the schoolboys from the need to memorize the names of fifty or so Kuiper Belt objects.
He meant is as a joke, but it points up the absurdity of the decision: it would be like declaring ‘Uranium’ not to be an element, on the grounds that it does not have a stable system of electrons, but decays over time into lead. Limiting the periodic table to Earth, Water, Fire, and Air would likewise save the memory cells of poor schoolboys. More than one hundred elements is too many!
Also, why irk the Living Fungi from Yuggoth, or any wormtongues or Palainians colonists who might be occupying that distant, frigid world?
I am waiting for the day when we make First Contact, and listen in surprise as the Vulcans or the Overlords or whoever explain that Sol has only four planets: Jupiter, Saturn, Uranus, Neptune. Everything else is classified as an asteroid.
About John C Wright
John C. Wright is a practicing philosopher, a retired attorney, newspaperman, and newspaper editor, and a published author of science fiction. Once a Houyhnhnm, he was expelled from the august ranks of purely rational beings when he fell in love; but retains an honorary title.
