The Pluto Files

While in Dallas for a few days over 4th of July at the National Federation for the Blind’s 2010 national conference, I read a short book that I think you’ll really like.  Written by my favorite living scientist, Neil deGrasse Tyson, The Pluto Files: The Rise and Fall of America’s Favorite Planet (find this book) is the story of America’s love for Pluto which reigned as most beloved planet in our night skies for 76 years.  Of course, Pluto is still the most beloved celestial object, but 4 years ago it was stripped of its planetary status.  The Pluto Files follows Pluto from discovery through demotion.

Neil with Pluto

Pluto was discovered by Clyde Tombaugh in 1930 at the Lowell Observatory.  Before it was discovered, it was predicted to exist based on Neptune’s orbit and was known as Planet X, which may be familiar to you if you are a fan of old-school Merrie Melodies cartoons.  About a year after it’s discovery and naming, the name Pluto was also given to a relatively new character in the world of Disney.

As technology advanced, scientists learned that there were other objects in our solar system that were even bigger than Pluto!  All of a sudden, a decision needed to be made: introduce these objects as full-fledged planets or give them their own class and put Pluto in there with them.

As a very public figurehead of the first mainstream exhibit to not put Pluto next to Neptune, deGrasse Tyson was soon hated by the American public who didn’t want to give up what they held as constant in their life, i.e. that there are 9 planets.  The IAU, which is in charge of naming celestial objects, eventually debated and voted on the fate of Pluto, as well as Eris (which is larger than Pluto), Ceres (which was at one time considered a planet), a few others that have been found and probably more yet-to-be-found.  The IAU came up with a definition for a planet, and Pluto didn’t fit the bill.  Instead of promoting Eris and Ceres, both, along with Pluto, were given dwarf planet status.

People protested, sent hate-mail, and refused to follow the new rule.  The Pluto Files is a great account of atmosphere at the time.  PBS aired a good companion piece, which you should watch too.  It can be viewed on PBS’s website or instantly from Netflix.

Neil deGrasse Tyson

Supplementary materials for this post are as follows:
@ScienceGoddess swoons over #sciencehottie Neil deGrasse Tyson with her video review.
Short, humorous clips from The Pluto Files.
Live action/animation of an explanation for Pluto’s demotion.
A song by popular folk-indie artist, Lisa Loeb, about 11 planets.
Neil deGrasse Tyson on Twitter and Facebook.


5 Responses

  1. Pluto IS still a planet, and it is only one opinion that a decision had to be made to define the term planet once more spherical bodies were discovered in the Kuiper Belt. Furthermore, Tyson has openly described the IAU definition as “flawed” and has distanced himself from it, admitting the debate over Pluto’s status is far from over. The IAU’s decision is not a “rule,” and the organization should not be considered to be “in charge” of naming celestial bodies. Only four percent of the IAU voted on this, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. Stern and like-minded scientists favor a broader planet definition that includes any non-self-luminous spheroidal body in orbit around a star. The spherical part is important because objects become spherical when they attain a state known as hydrostatic equilibrium, meaning they are large enough for their own gravity to pull them into a round shape. This is a characteristic of planets and not of shapeless asteroids and Kuiper Belt Objects. Pluto meets this criterion and is therefore a planet. Under this definition, our solar system has 13 planets and counting: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, and Eris. A good book you might want to read supporting Pluto’s planet status is “The Case for Pluto” by Alan Boyle.

  2. Thanks for the comment.

    How do you feel about the “clears its path” qualifier? I can guess, but I’d like to hear your thoughts regarding why that isn’t a helpful characteristic.

  3. No planet in our solar system fully “clears its path” of asteroids. Neptune does not clear its path of Pluto. This qualifier, if applied literally, could end up with our solar system having no planets! And it automatically precludes a binary system since the two objects by definition do not “clear their paths” of one another.

    Dr. Alan Stern coined the term “dwarf planet,” and he intended it to refer to small planets–objects large enough to be rounded by their own gravity but not large enough to gravitationally dominate their orbits. Gravitational dominance doesn’t mean the planet clears its orbital path of every last asteroid, just that it is the dominant object in that path. However, the important point is that Stern never intended dwarf planets to be considered not planets at all! His intention, which is the direction astronomers should take in amending the 2006 IAU vote, is that dwarf planets represent a third class of planets in addition to terrestrials and jovians. This is consistent with the use of the term “dwarf” in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. It allows these small spherical bodies to still be considered planets, just of the dwarf subcategory if they do not gravitationally dominate their orbits (i.e., orbit in a belt of other, usually smaller objects).

  4. In the book, NdGT mentioned the clearing of a path.

    He gave an example of the space debris in Earth’s orbit as accounting for less than 1% of all matter in that orbit. Whereas, in Pluto’s case the number was much higher.

    I don’t remember the exact number, but it wasn’t like 1 or 2%, it was like 25% or 75%. The specifics escape me and I’ve already returned the book to the library. 😉

    As for Neptune, my understanding is that Pluto and Neptune have yet to be close enough to bump into each other.

    As for binary planets, it stands to reason that if the center of gravity doesn’t lie entirely within either body, that the binary system itself is made up of two planets. Collectively, they clear the path. But binary planets would technically be a new term, merely made up of two bodies in orbit around one another that clear their path.

    Regarding the term “dwarf planet,” I agree. It’s a misnomer. If it’s a dwarf planet, it’s a planet–a small planet. Plutoid would have been less confusing on that issue.

    For the record, I’m not arguing Pluto’s planethood one way or the other. Pluto is Pluto regardless of what humans call it. I just think it’s an interesting debate. For now, though, I think the debate has been settled (i.e. there doesn’t seem to be any strong movement on the front some 4 years later). But I would like to welcome Ceres, Pluto, Haumea, Makemake, and Eris to the solar system as full planets if our classification of those objects changes in the near future.

  5. Actually, the debate has not been settled; it’s just that astronomers on both sides recognize it’s a stalemate and have chosen to hold off dealing with it until we have the data from New Horizons. Stern and many planetary scientists asked the IAU leadership to reopen the issue at last year’s General Assembly, and they refused. As a result, these planetary scientists en masse boycotted the General Assembly. They have stated on several occasions that they are essentially ignoring the IAU and working separately from them, at times even suggesting the formation of a new planetary science organization. Meanwhile, the issue continues to be discussed in numerous conferences and books, and that is the way the movement continues. Schools are encouraged to teach it as an ongoing debate. I’m writing a book on Pluto, but it won’t be out for a while. I suggest reading “The Case for Pluto” by Alan Boyle.

    Neptune and Pluto will never bump into each other; however, since they cross each other’s orbits, neither can be considered to have “cleared its orbit” of the other body.

    Stern and Hal Levison in 2000 wrote an article on the question of gravitational dominance and how much matter is in each planet’s orbit. I will try to find a link to that article.

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