The Intersection

That Mean, Mean Anti-Pluto Guy

i-e9c77f01b9ae7149069f91b3719fbc9b-plutobook190.jpgKenneth Chang notes that Neil deGrasse Tyson has a new book coming out very soon: The Pluto Files. Apparently deGrasse Tyson caught a lot of hell over the years for being involved in the slighting of Pluto over at the Hayden Planetarium, long before the International Astronomical Union finished the banishment in 2006.

I’ll look forward to reading Tyson’s book, but as a Plutophile I gotta say, the plaque that the Rose Center for Earth and Space provides to explain its Pluto demotion (which I learned about thanks to Chang’s post) isn’t very impressive to me. It reads like this:

Our solar system includes four rocky (terrestrial) planets and four gas giants…Pluto’s ice-rich composition and unusual orbit set it apart from both families. But it shares these traits with the Kuiper Belt Objects, a recently discovered swarm of thousands of large icy comets orbiting just beyond Neptune.

Some astronomers regard Pluto as a Kuiper Belt Object, some call it a planet, and others think of it as both. This confusion arises because a consensus has yet to emerge on the scientific definition of “planet.”

Hmm…maybe the definition of planet isn’t solely up to modern science? Don’t history and culture count for anything?

Sheril and I just bought our “Dear Earth, You Suck: Love Pluto” t-shirts, so we’ll have more to say about all of this soon enough, including in Unscientific America. Meanwhile, read Dr. Tyson’s book, and try to remember that despite his role in the Pluto affair, he isn’t a bad person…just a little misguided.

* We apologize that comments are not currently posting. Scienceblogs is doing maintenance and The Intersection will return to normal soon.


  1. #1 Sheril R. Kirshenbaum
    January 9, 2009

    Actually, my shirt reads “Vote For Pluto” 😉

    Pluto will always be a planet to me.

  2. #2 Pluto Agnostic
    January 11, 2009

    In what sense does Pluto have history on its side?

  3. #3 andy
    January 11, 2009

    Maybe the issue of whether vaccines are safe isn’t solely up to medical science? Don’t people’s feelings count for anything?

    If you go down that road…

  4. #4 Laurel Kornfeld
    January 12, 2009

    Kudos to you for recognizing that history and culture do count here. Pluto is both a planet and a Kuiper Belt Object, as are Haumea, Makemake, and Eris. They are planets because they have attained hydrostatic equilibrium, meaning they have enough self-gravity to have pulled themselves 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.

    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.

    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 You can also read more about this issue on my blog at

    Tyson’s presentation at that debate was far more show than substance and notably, he did not answer my question.

    You can find the petition of astronomers who rejected the demotion of Pluto here:

  5. #5 Phil
    January 12, 2009

    That cover picture bothers me. I think it was originally from that IAU meeting press release. You’d think the person who pasted in the planets in could at least rotate them so the shadows don’t point at the Sun…

New comments have been temporarily disabled. Please check back soon.