Illinois Tries to Sell Pluto Full Planet Status (Or Just Give It Away)

By Andrew Grant | March 2, 2009 4:17 pm

PlutoFresh off voting to remove its ethically questionable and impeccably coiffed governor from office, the Illinois senate has moved on to more important matters: making Pluto a full planet again.

In addition to overruling the International Astronomical Union (IAU)’s demotion of the planet (at least within the state), the unanimously-approved bill also designated March 13, 2009 as “Pluto Day,” since Illinois’ own Clyde Tombaugh discovered Pluto on that date in 1930.

Pluto was downgraded to a dwarf planet in 2006, because it didn’t meet the requirement that a planet clear the area around it of debris due to its gravity. Ever since the IAU’s diss, many people—including astronomers, other state legislators, and ordinary citizens—have criticized the organization’s definition of a planet, which was formulated by only 424 of 2,412 IAU astronomers. The IAU subsequently decided to show Pluto some love by classifying it and all dwarf planets beyond Neptune’s orbit as “plutoids.”

Stay tuned on for a recap of an astronomy roundtable that included Mike Brown, whose discovery of Eris (a dwarf planet larger than Pluto) delivered Pluto’s planetary death blow.

Related content:
Bad Astronomy: Pluto’s big Hill to climb
Bad Astronomy: Sharpest image of Pluto ever taken
80beats: The Fourth Dwarf Planet Is Officially Christened: Meet “Makemake”


CATEGORIZED UNDER: Space & Aliens Therefrom
MORE ABOUT: Illinois, pluto
  • Laurel Kornfeld

    There is no “death blow” to Pluto, as this debate is still alive and well. You owe it to your readers to present experts on both sides. If you interview Mike Brown, you should also interview Alan Stern or Mark Sykes to represent the other point of view, that Pluto is a planet, a viewpoint still held by many planetary scientists.

    The Illinois Senate has way more sense than the International Astronomical Union has shown in two-and-a-half years. It’s the IAU who have acted like idiots, with one tiny group forcing a nonsensical planet definition on everyone. The truth is there is NO scientific consensus that Pluto is not a planet. The criterion requiring that a planet “clear the neighborhood of its orbit” is not only controversial; it’s so vague as to be meaningless. Only four percent of the IAU even voted on this, and the vote was driven by internal politics. A small group, most of whom are not planetary scientists, wanted to arbitrarily limit the number of planets to only the largest bodies in the solar system. They held their vote on the last day of a two-week conference with no absentee voting allowed. Their decision was immediately opposed by hundreds of professional astronomers in a formal petition led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto.

    Stern and like-minded scientists favor a broader definition of planet that includes any non-self-luminous spheroidal body orbiting a star. The spherical part is key because when objects become large enough, they are shaped by gravity, which pulls them into a round shape, rather than by chemical bonds. This is true of planets and not of shapeless asteroids and comets. And yes, it does make Ceres, Eris, Haumea, and Makemake planets as well, for a total of 13 planets in our solar system.

    Even now, many astronomers and lay people are working to overturn the IAU demotion or are ignoring it altogether. Kudos to the Illinois Senate for standing up to this closed, out of touch organization whose leadership thinks they can just issue a decree and change reality.

  • Gary B

    There is a common strategy that could resolve this controversy – at least from a political POV. In politics and law, it is common for items that pre-exist a new law to be ‘grandfathered’ in. For example, a house I am considering buying has been grandfathered in so that it can still be lived in, despite present day zoning that requires a larger lot.

    Similarly, to accommodate popular sentiment, it is quite reasonable for Pluto to be grandfathered into the class of full planets, and all others like it to be left in the class of plutoids. In fact, to my mind this makes the term ‘plutoid’ more interesting. I don’t think that is too much of a violation of scientific sensibilities. I’m sure there are equivalent situations already in science – I just can’t think of any offhand!

  • Robert Shepard

    Given that Eris is a tad bigger than Pluto, I suspect that “grandfathering” Pluto back in would also have to include Eris as “the 10th planet”. That would take us back to the informal understanding of “planet” we had prior to the IAU’s August 2006 decision.

    I certainly don’t have any problems with that, though I’m more in favor of Alan Stern’s “13 planet” model. Roundness rules!

  • Kate



    Emotional ties should have nothing to do with the scientific classification of celestial objects. Seriously, all of you grow up and stop whining. I’m talking to you, Illinois!

  • Pingback: Pluto A Planet Again… Sort Of at Fight The Hypo()

  • EOTD

    @ Gary – this is science, not politics. By that logic, water and fire should be “grandfathered in” as elements.

    The simple fact is, whether Pluto’s classification as a “planet” or as a “dwarf planet” (which , in both cases, still means it’s a planet of some kind) makes ABSOLUTELY NO DIFFERENCE TO ANYTHING THAT HAPPENS ON EARTH.

    And the people calling for its reinstatement are forgetting one important detail: Charon. Pluto’s “moon”, as it’s usually portrayed, is just over half the diameter of Pluto itself, and the barycenter of gravity of the system is ABOVE PLUTO’S SURFACE, in between the two bodies – so if you want to get technical, it is actually a double-planet called Pluto-Charon. They may be round, but the fact remains that they’re pretty different from the eight major planets.

    Face it, Pluto is very unlike the major planets, and very like the dwarf planets – and no matter what, it’s still a planet of some kind. So how about we finally let this issue die, accept that our scientific understanding of the world around us in fact DOES CHANGE every so often, and move on to something that actually matters?

  • Robert Shepard


    But that’s the rub. You and I see “dwarf planet” as an adjective (“dwarf”, meaning “small”) plus a noun, “planet”. Of course Pluto, Eris, Ceres and other like bodies are small planets. Of course they don’t dominate their orbits like Earth does, or (especially) Jupiter. Maybe it isn’t worth trying to memorize them all, and we should just stick with the biggest eight.

    What bothers a lot of people about the IAU’s August 2006 decision is that they treat “dwarf planet” as a compound noun, “dwarfplanet”. They’ve ruled that these bodies are, in fact, NOT planets at all. How can a planet not be a planet? It’s confusing. Hence all the bickering. The IAU would have been better off using the term “planetoid”.

    As for Pluto-Charon being a double (dwarf) planet, I agree. But the IAU failed to rule on the definition of “double planet” in August 2006, so that is in limbo.

    For those who haven’t seen it already, an excellent and exhaustive discussion thread covering all of the issues can be found here:

    Note that Dr. Brown has closed the thread. His conclusion is that there are two perfectly rational classification systems: the eight-planet model, and the “hydrostatic equilibrium” model (currently 13 planets, with more to come). Choosing between the two isn’t really a matter of science.

    I suspect people are going to continue to debate the matter indefinitely, whether it matters in the grand scheme of things or not. But my part in the matter here is finished.

  • Pingback: America Ignores Pluto Day Recognition March 13th | Right & Wrong Journal()

  • Dr. Robert Hamann

    Laurel- ‘Stern and like minded scientists’….LOL……The TRUTH is that there is NO SCIENTIFIC CONSENSUS on many topics that the IAU has debated and considered. The same is true for politics and history etc etc etc blah blah blah.

    1. When Pluto was first discovered it was thought to be about the same size as Earth!

    2. Gerald Kuiper himself also based his hypothesis on the Solar System’s evolution based on Pluto (once again) being the same size as Earth. Had he been right in 1951- there would not have been a Kuiper Belt as we now know it- but he was wrong.

    3. There should be 13 planets- not 8? LOL WHY NOT 14? WHY NOT 15?

    Mike Brown also discovered what came to be called Orcus. It has a moon and should also be a dwarf planet. Orcus moves in an orbit similar to that of Pluto, i.e. it completes three orbits of the Sun for every two of Neptune goes around the sun.

    Your hero Stern said on Aug 25, 2006 to the BBC; “It’s an awful definition; it’s sloppy science and it would never pass peer review”

    LMAO- Stern is clearly jealous of Mike Brown, but his words should be meant for those back in 1930!!!!!! When scientists at the Lowell Observatory announced they had spotted Pluto in 1930, they claimed it was several times larger than Earth, ensuring its prompt entry into the textbooks as the ninth planet. It later turned out to be a rock substantially smaller than the moon. They had great P.R and the press in the Uniteds States championed ‘Pluto’ during the depression- it was a great moment in American science, but it was all wrong- the ‘planet’ was in fact a rock smaller than the moon!!!!!!!!!!!!!!!

    Pluto is a member of a vast band of extremely distant rocks called the Kuiper belt that orbits the sun beyond Neptune. When you consider that fact- as well as the size of several bodies that have recently been discovered, we would end up with 15 planets! Where does it end?????

    Our moon is 1.5 times bigger when you compare it to Pluto-and Pluto is a planet? LOL

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