Poll: Should Pluto be Re-Instated as a Planet?

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In 2006, the International Astronomical Union (IAU) decided to re-classify what constituted a planet. Firstly the candidate must orbit the Sun. Secondly, it must be spherical (none of those asteroid-potato shapes please). Thirdly, it must clear its orbital path of junk. As soon as these three planetary characteristics were specified by the IAU (who is responsible for planet-naming and astronomy nomenclature), Pluto found itself orbiting without a planetary licence and promptly got demoted to a “dwarf planet.” This decision caused two years of arguing and public outcry until the IAU dubbed any Pluto-like bodies as “Plutoids.” This move by the IAU was seen as an affront to a member of the Solar System’s ninth planet, which had over 70 years of proud history (after all, it was thought to be the mysterious Planet X at one point). So next week, the world’s leading astronomers and planetary scientists are gathering in Maryland for a conference addressing the Pluto issue, voicing their frustration at the IAU’s controvercial decision and calling the “Plutoid” classification the Solar System’s “celestial underclass”…

This Pluto debate has taken the world by storm. Generally, people are upset about Pluto being down-graded to a “dwarf planet,” and then the IAU issue an announcement that Pluto can actually have its own class of minor celestial bodies; calling this type of Kuiper Belt object a “Plutoid.” Great, at last, Pluto can be respected by calling a whole number of other small rocky bodies; Plutoids.

But as it transpired, Pluto nor the majority of the world was amused. Being a Plutoid, it seems, is a bit like saying you grew up on the wrong-side of the tracks. It isn’t a desirable title and some critics cite Plutoids as the “celestial underclass.”

So what should be done? Should Pluto be reinstated as a planet? Or should we just get used to the idea that Pluto simply doesn’t match the criteria to be a planet? All these questions are expected to be raised on Thursday at the The Great Planet Debate: Science as Process” conference at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. We’ll see what happens…

For now, have your say, I’d be interested to hear just how important Pluto is to you…

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4 responses to “Poll: Should Pluto be Re-Instated as a Planet?

  1. Here is my response when I encounter people that are angry about Pluto:

    I like to start with the following question:

    Suppose you were outside and saw this: (insert picture of a green leafy plant that is about 5 feet tall). What would you call it? Some might call it a tree, others might call it a bush. Does the name change what it is? What if scientist came up a classification for determining if something was a bush or a tree. According to wikipedia, there is not complete agreement on the definition of a tree. This is ok, because the name of something isn’t really that important.

    That is the point, Pluto is like a green leafy plant that some would say is a bush and some would say is a tree. To make things clear, scientist have created the following definition of a planet. A planet is an object that meets the following requirements:

    * Orbits the sun (this is ok for Pluto)
    * Large enough to be spherical (this is also ok for Pluto)
    * The most massive object in its neighborhood of the solar system (this is where Pluto fails).

    Pluto fails the last criteria because it is in the area of Neptune (sometimes it is even closer to the Sun than Neptune). Thus, alas, Pluto is not classified as a planet. It shall be called a dwarf planet.

  2. Pluto IS a planet because unlike most objects in the Kuiper Belt, it has attained hydrostatic equilibrium, meaning it has enough self-gravity to have pulled itself into a round shape. When an object is large enough for this to happen, it becomes differentiated with core, mantle, and crust, just like Earth and the larger planets, and develops the same geological processes as the larger planets, processes that inert asteroids and most KBOs do not have.

    Not distinguishing between shapeless asteroids and objects whose composition clearly makes them planets is a disservice and is sloppy science.

    As of now, there are three other KBOs that meet this criterion and therefore should be classified as planets—Haumea, Makemake, and Eris. Only one KBO has been found to be larger than Pluto, and that is Eris.

    The IAU definition makes no linguistic sense, as it states that dwarf planets are not planets at all. That’s like saying a grizzly bear is not a bear. Second, it defines objects solely by where they are while ignoring what they are. If Earth were placed in Pluto’s orbit, by the IAU definition, it would not be a planet. That is because the further away an object is from its parent star, the more difficulty it will have in clearing its orbit.
    Significantly, this definition was adopted by only four percent of the IAU, most of whom are not planetary scientists. No absentee voting was allowed. It was done so in a highly controversial process that violated the IAU’s own bylaws, and it was immediately opposed by a petition of 300 professional astronomers saying they will not use the new definition, which they described accurately as “sloppy.” Also significant is the fact that many planetary scientists are not IAU members and therefore had no say in this matter at all.
    Many believe we should keep the term planet broad to encompass any non-self-luminous spheroidal object orbiting a star.

    We can distinguish different types of planets with subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc.
    We should be broadening, not narrowing our concept of planet as more objects are being discovered in this and other solar systems.

    In a 2000 paper, Dr. Alan Stern and Dr. Hal Levison distinguish two types of planets—the gravitationally dominant ones and the smaller ones that are not gravitationally dominant. However, they never say that objects in the latter category are not planets.

    I attended the Great Planet Debate, which actually took place in August 2008, and there was a strong consensus there that a broader, more encompassing planet definition is needed. I encourage anyone interested to listen to and view the conference proceedings at http://gpd.jhuapl.edu/ You can also read more about this issue on my blog at http://laurele.livejournal.com

    You can find the petition of astronomers who rejected the demotion of Pluto here: http://www.ipetitions.com/petition/planetprotest/

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