Pluto: It’s Still Out There

My recent post on the history of Pluto got me thinking about why I’m more interested in the story of Pluto than the ongoing debate about its status. I decided to look at some of the bigger and more common issues surrounding Pluto that pop up online – Pluto bloggers, message boarders, and online societies looking to save Pluto. Their arguments vary from the scientific to the ridiculous. The original article can be found at, but I thought it would make a good complement to my last post, so I’ve reblogged the article here and added a few pro-Pluto comics that have been making their way around the internet lately. (Left, Pluto. Still at home in the solar system.)

This week, I posted an article on my blog about Pluto—its discovery, its properties, and what led to its reclassification as a dwarf planet. I didn’t think this was a controversial topic, especially since I went out of my way to present facts about the issue as straightforwardly as possible to give an overview of the whole situation. Turns out, there are there are some very opinionated bloggers and message board posters out there who aren’t shy about putting their Pluto-loving message out for the world to see. It made me wonder: What’s the big deal?

To briefly recap (and greatly simplify): In 2005, Caltech astronomer Mike Brown discovered a celestial body, Eris, orbiting much further away from the sun than Pluto; initial calculations of its apparent brightness suggested it is actually bigger than Pluto. Brown excitedly thought might have discovered a new planet—the first discovered since Pluto in 1930—but the decision on this was in the hands of the International Astronomical Union (IAU), a body of scientists that has been classifying and naming solar bodies for decades. (Pluto from Saturday Cartoons by Mike Stivers.)

Brown’s planet raised more questions than it answered. If Eris was a planet, there were other objects out there that would have to become planets, too. Ceres, an asteroid originally classified as a planet in the early 1800s, shared enough properties with Eris that it would become a planet as well. But Pluto also shared a number of qualities with Eris, which opened up the possibility that a vote against Eris’ planet status could affect Pluto.

The IAU voted at the end of the society’s 2006 meeting in Prague. Two resolutions up for vote affected Pluto: the IAU’s potential new definition of what a planet is and a vote specifically on Pluto’s status. The vote determined that planets had to meet three criteria, all based on gravity. As the IAU defined them, planets must have enough gravity to make themselves round, orbit the sun without being a satellite of another body and clear the area around it of any debris.

The vote also introduced two other classes of solar bodies. Dwarf planets must orbit the sun, must be nearly round thanks to their own gravity and must not be a satellite, but can be too weak to clear debris from their orbits. Everything else would be classified as a small solar system body. A separate vote made Pluto the prototype for this new class of dwarf planets. (Pluto at the little planets’ table. From Primordial Ooze: Astronomy Archives.)

So now our understanding of the solar system includes three types of planets—terrestrials, Jovian, and dwarf—as well as a host of smaller bodies such as Kuiper Belt and Oort Cloud objects, asteroids, and comets. I suppose strictly speaking, Pluto isn’t a planet proper anymore like Earth or Jupiter; it’s a dwarf planet, which is a class of planet, so it’s still a planet.

Despite a simple reclassification, there are masses of astronomers and lay people who want Pluto back. They want a reversal of the IAU’s vote that made Pluto a dwarf planet, and they want all the other dwarf planets, including Eris and Ceres, to be planets too! According to them, everything should be a planet!

I suppose I should side with the Pluto-lovers. I learned about Pluto in the second grade when I learned about the solar system. I even fell in love with space during that science unit; it turned out to be a pretty formative school year in my life. But even when I was seven, I could see that Pluto was literally an odd ball. It didn’t fit in with the other eight planets. The more I read about astronomy and as more objects were discovered, the more convinced I was that Pluto was one of a group of similar objects. When the IAU introduced the class of dwarf planets and placed Pluto among them, I wasn’t surprised. The decision made sense. Especially since they were still called planets, just a different class of planet. (Poor Pluto. This one’s been making the rounds on social media sites lately.)

So why are so many people up in arms about this classification? Dr. Alan Stern, principle investigator of NASA’s New Horizons mission that is currently en route to Pluto, is the strongest advocate for Pluto’s renewed planetary status. He takes issue with the IAU’s definition, calling it limiting and poor science. He’s right. The vote was made by fewer than 500 of the IAU’s 10,000 or so members and thus isn’t indicative of the majority. The definition of ‘planet’ isn’t perfect either; it creates awkward and contrived classifications in a universe that isn’t as rigid and ordered as scientists might like. He argues that every body that exhibits the qualities of a planet should be a planet.

This is where I get lost. Aren’t dwarf planets, planets? Is the descriptor ‘dwarf’ throwing people off? Maybe my lack of strong formal training in astronomy makes me unable to see the difference, but to me a planet is a planet, dwarf or otherwise, and an interesting object in the solar system will continue to be an interesting object. Classification is a little more than a convention. (It’s okay, Pluto has been popping up on t-shirs all over the internet.)

But there are more, far less scientific reasons that people want Pluto’s status renewed. Some of them border on the absurd. Popular culture, apparently, is the real victim in the whole Pluto affair.

School children in particular take issue with Pluto’s downgrade., a website devoted to educating the masses about why we need Pluto back, writes that “taking away [Pluto] will confuse and sadden children, where adding [more planets] could cause expanding wonderment.” In 2006, a man submitted an open letter to scientists in New Scientist magazine. He wanted them to bring Pluto back. His five-year-old nephew was upset over the loss of the planet. He thought it blew up.

Maybe the issue isn’t the reclassification of Pluto. Maybe it’s educators telling students, with no explanation, that Pluto isn’t a planet anymore. I haven’t looked at a grade school science book in about two decades, but I did take a walk through the children’s science section at Barns and Noble last week. Pluto isn’t gone from books, it’s right where it’s always been, orbiting just outside Neptune. The only difference is that it’s listed with the other dwarf planets. The same books also separate the terrestrial inner planets from the outer gas giants. (New science class. From the Centre for American Progress.)

There’s no reason that Pluto’s change in status means kids can’t learn about it. In fact, they should be learning that there is more than one type of planet. Let Pluto be the one that teaches future astronomer about dwarf planets. Let Pluto be a brilliant example of the ever-changing field of astronomer. Instead of focusing on the loss of Pluto from the perfect childhood, focus on it as a new teaching tool.

This argument only brings to mind images of Helen Lovejoy screaming “Won’t somebody please think of the children?!”

Astrologers are also mourning the loss of Pluto. The dwarf planet is the ruling body of all Scorpios, so anyone born between October 24 and November 22 is now without a strong celestial influence. We all know astrology is a real, totally trustworthy science. We should definitely care about this. (I’m sorry if anyone out there abides religiously by their horoscopes. This comic is from

People seem to be acting as though the IAU’s decision has flung Pluto off in to deep space to find a new home. It’s been anthropomorphized on t-shirts, and given a personality to the point where people are throwing parties for Pluto to show their support. Not Pluto-themed parties, parties for the dwarf planet.

Pluto doesn’t need to be ‘saved’. It’s still out there and it’s not going anywhere (except around the Sun really fast). If you’re a Scorpio born under Pluto, you’re still born under Pluto, and it will still dictate your life if that’s how you like to think about things. If you’re an astronomer, it’s still out there to see and measure. If you’re a planetary scientist, it’s still a relatively unknown body out there and deserves more attention. Frankly, as a dwarf planet I think Pluto becomes more interesting. It’s not a lone random rocky ice ball, it’s one of many. Learning more about Pluto potentially means learning about all the similar bodies, which just might lead to a better understanding of our solar system. (Left, Pluto and Charon as seen by the Hubble Telescope in 1990.)

Pluto’s change is in name only. It’s still totally awesome. Are we done talking about it now?


4 thoughts on “Pluto: It’s Still Out There

  1. Thank you so much for looking deeper into this issue and for quoting Dr. Stern, the person who first coined the term dwarf planet. As a blogger who actively advocates the planetary status of all dwarf planets–and who is also in the process of going into the field professionally–I appreciate your recognition that there are scientific merits in the case for dwarf planets continuing to be called planets.

    Part of the problem is the specific wording of the IAU resolution. You say: “This is where I get lost. Aren’t dwarf planets, planets? Is the descriptor ‘dwarf’ throwing people off?” The answer is, it’s the IAU claim that dwarf planets are NOT planets at all that is throwing people off. Yes, dwarf planets are planets; they are a subclass of “proper planets,” and that is the position held by those of us who favor a geophysical planet definition. “Dwarf planet” is a noun modified by an adjective. The IAU confused everyone by claiming “dwarf planet” is not the above but is a “compound noun,” something that does not exist in English grammar. This claim is the primary objection to the IAU definition, and it could easily be modified by amending the resolution.

  2. Astrologers are also mourning the loss of Pluto. The dwarf planet is the ruling body of all Scorpios, so anyone born between October 24 and November 22 is now without a strong celestial influence. We all know astrology is a real, totally trustworthy science. We should definitely care about this.

    As a historian of astrology I find this statement hilarious. From the beginnings of horoscope astrology in the fifth century BCE till its discovery in 1930 astrologers had absolutely no idea of the existence of Pluto!

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