Thanks to Bill at the Evil Eyebrow for inviting me to participate in his Plutopia! blog carnival. Or if “invite” isn’t really the appropriate word, at least throwing out a blanket invitation and letting me sign on.
So the whole point is that today is the 2nd anniversary of Pluto’s official demotion from the arbitrary astronomical classification “planet”. I’m not going to get into the pseudo-political world of why this is arbitrary or whether it’s particularly significant in any particular way, what I am going to say is:
Pluto is small.
Really freaking small.
Or at least really freaking small relative to anything else that we have come to know and love as a planet. According to NASA, Pluto is 1422 miles (2288 km) in diameter. So although I wouldn’t want to personally walk its entire 4467 mile circumference in one trip, it’s easy to fly that far without leaving this planet. In fact, in my flights to and from Australia, I traveled over three times that far (more if the trans-American legs are included). Granted, Oz is pretty far away in Earth terms, but can we really respect an astronomical body that can be circumnavigated in half a day by a commercial airliner? Mercury is now the smallest planet with a circumference of over 9500 miles (15000 km). Check out this graphical planet size comparison widget.
It’s not just that Pluto is smaller than our Moon, but because it’s 8 bajillion* miles (13 bajillion** km) away it’s absolutely ridiculously hard to see. In preparation for this post, I decided to pull up my handy free home planetarium software, HNSKY, and see if Pluto is actually visible. Not that I expected to walk outside, point to the sky and say “there’s Pluto”, but I thought there might be some remote possibility that I could capture it in a picture. It IS technically in the sky right now, not far from Jupiter in the sky (about 15 degrees to the right at the time of publication: 00:01 EDT). The problem is that (according to the software) Pluto is about magnitude 13.9. Do you have any sense for how many objects in the sky are brighter than that? No? Take a look at the picture below. It is the area around Jupiter and Pluto that you might see with the naked eye on a clear summer night with stars to magnitude 6 shown. Pluto should not be visible, but is marked with a small green dot and two lines.
One could reasonably argue that this is a better sky than most people will ever see, but it doesn’t matter, because THIS is what the sky would look like if you could see everything up to and including Pluto.
Obviously, you can see that the software has sort-of broken down for this many stars… and in fact, seems to only be displaying stars up to 11th magnitude. Click on the picture to see a larger rendering of this same piece of sky. My point is that even if you COULD see Pluto, you probably WOULDN’T see Pluto because it would be lost in the jumble of the other million objects in the sky which are brighter than it is. Which of course means that even if I could point my camera at the right piece of sky, AND get a few hundred thousand photons*** to travel from the Sun AND bounce off Pluto AND end up in my lens it would take a significant effort to determine which one of the non-black pixel dots contained Plutonian photons.
For reference, the two dimmest planets are Uranus and Neptune at approximate visual magnitudes of 5.7 and 7.8 respectively. So even though Uranus is within the range of human perception it wasn’t documented as discovered until 1781 AD. It was simply another dot lost in the background noise, and moved too slowly to appear to be changing in the sky.
So Pluto, we salute thee, even though you’re small and dim and probably deserved to not quite rank with the eight remaining Solar planets. The good news is that you seem to have plenty of siblings in this new realm of astronomical bodies.
Check out the rest of the Plutopia blog fest at the Evil Eyebrow.
August 24th, 2008 at 11:32 am
[...] status. I had invited several people to contribute to this event. Chris Schierer has remarked that Pluto is really really small and is very very hard to see. Kim Bosco tells us how Pluto was found and why Kansas is key! Lastly, Steph Sisson has composed a [...]
August 24th, 2008 at 11:45 am
Pluto isn’t dead, and in spite of the vote of 424 members of the IAU (four percent of its membership), it’s still a planet. Why? Because like the other major planets, Ceres, Eris, and Makemake, Pluto is in a state of hydrostatic equilibrium, meaning it has enough self gravity to have pulled itself into a round shape. When this happens, geological processes akin to those on Earth and the other planets start to take place–something that does not happen on shapeless, inert asteroids. According to the IAU definition, if Earth were in Pluto’s orbit it wouldn’t be a planet either–just another reason why their definition makes no sense. When New Horizons gets to Pluto in 2015, this “not a planet” nonsense is likely to go the way of New Coke.
August 24th, 2008 at 12:35 pm
Unfortunately Laurel, neither you nor I get to decide individually what “planet” means. If there is a body (other than Webster’s) that gets to decide this, I think we would agree that the IAU is probably that body. Now, popular opinion to the contrary, science is not arbitrary.
I’ve heard the “Earth wouldn’t be a planet either” argument before, and I don’t think it holds water (or ice). Frankly, Earth isn’t orbiting the sun 3.6 billion miles away (on average). If it was, it would (probably) be a nearly invisible lifeless hunk of frozen rock and ice too. I was going to calculate its apparent magnitude, but I doubt I’ll bother… given how dim Uranus and Neptune are, Earth would be pretty ignorable too. In that sense, how significant would a frozen rock called Earth (and its abnormally large moon) really be? Would some ancient culture of sentient Martians notice it? Would the Martian IAU consider it significant enough to include in the hierarchy with the ‘real planets’? Maybe there is such a planet and we just haven’t found it yet.
So back to the politics, could it be that this bias towards rocks (or gas balls) that are closer to their life-giving stars is appropriate? Shouldn’t those entities be given precedence in the astronomical pecking order?
It’s also easy to separate Pluto from a ’shapeless, inert asteroid’ when we think of the classic ‘asteroid.’ As a writer, you know that it is at the boundaries, where definitions blur and poetic license can be applied that language and discourse is most interesting. What if New Horizon’s finds that Pluto is particularly lopsided or has a big chunk taken out of it? Will that change our opinion of it? What if it’s plaid or has stripes, or a big sign that says “Don’t Panic”? If it has glowing cities and roads, you can bet it will suddenly dwarf even mighty Jupiter in significance. How arbitrary is that?
As always the dividing line between two classifications is arbitrary, not because science is, but because language is. We are perceptual beings. My orange is your red and someone else’s yellow, but we’ll probably agree that it is neither blue nor violet (unless we’re colorblind). In the end, all things tend to lie on a spectrum, but we’re trying to draw a line between red and yellow. Not because red is significantly different than yellow (electromagnetically speaking it is about a 25% change in frequency but that’s nothing compared to the total electromagnetic spectrum), but classification is important to concentrate our thinking and clarify our meaning.
Oh, next time a vote like this comes up at the IAU, maybe the other 96% ought to think about showing up.
Thanks for reading! What a great discussion!
August 24th, 2008 at 3:22 pm
Ok, but why the IAU? Surely there’s an appropriate planetary scientist organization? The IAU is much more about stars and the like than planets. It’d be like a group of marine biologists defining what limestone is. Sure, they share the same space, but not the same level of expertise.
August 24th, 2008 at 8:41 pm
I think the marine biologist – limestone analogy is a bit far fetched, but I get your drift.
I can only refer to the mission the IAU has given itself (emphasis mine):
I guess the debate may be on the ‘unambiguous’ part.
August 24th, 2008 at 8:42 pm
Sorry, quote taken from: http://www.iau.org/about/
August 24th, 2008 at 10:11 pm
Hmph. Well who died and made them god?
August 25th, 2008 at 12:04 pm
Chris, the issue of who gets to decide what a planet is is a crucial one, and I do not agree that it should be the IAU, especially since they did such a horrible job not just once but twice (in 2006 with the original planet definition and in 2008 with the “plutoids” classification). The IAU has not even entered the digital age. Only four percent voted in Prague because no electronic voting was allowed. Anyone who wasn’t in the room on the last day of a two-week conference could not vote. Kim Bosco makes a very good point that was raised at the Great Planet Debate in Laurel, MD two weeks ago. Most members of the IAU (and most who voted in Prague) are not planetary scientists but other types of astronomers. Over the last 40 years, as we have had spacecraft explore the planets up close, planetary science has diverged from general astronomy and become its own field, in many ways much more akin to geology and meteorology. Most planetary scientists are not members of the IAU, a fact raised at the Great Planet Debate. Yet who would do better at classifiying planets than those who study them? That is why there is an initiative in the works to start a new organization of planetary scientists. The IAU may claim it is the authority for designating celestial objects, but in reality, it has no mechanism to compel anyone to follow its dictates, and another group, such as one of planetary scientists, could easily make the same claims regarding planet definition.
I believe that any planet definition cannot be based solely on where an object is but must take into account what that object is. Otherwise, we have a system like the current IAU definition that is biased against planets further from the sun, which have larger orbital neighborhoods to “clear.” Stating that an object must harbor intelligent life as we know it to be considered a planet is way too anthropomorphic. Using that logic, one could conclude that Earth is the only planet in our solar system.
I agree with you that it is at the boundaries where definitions blur, but we know enough about Pluto to know that it does not fall anywhere near those boundaries. We have enough images of Pluto to know that it is round and in a state of hydrostatic equilibrium. It is cases like Vesta, where we know an impact lobbed off the south pole of a previously round object, that are at the boundaries. Of course, New Horizons will likely surprise us with its findings, but I don’t think it’s going to find that Pluto is lopsided or not round. In fact, it is far more likely that New Horizons’ findings will illustrate the presence of the same geophysical processes that occur on what we now call the “classical planets.”
August 25th, 2008 at 8:21 pm
Well, I suppose the IAU self-declared ages ago and nobody argued at the time, so it stuck.
There are very few (if any) bodies in the scientific community that have the power to ‘compel’ anyone to do anything, this is why such things are referred to as ‘conventions’ not laws.
How a body does or doesn’t include votes isn’t really the concern here, is it? Trust me I am no fan of the current US electoral system but I can’t decide to ignore it. I can make my voice heard WITHIN the system and garner support until it’s changed. OR I can go live on an island and declare my own government. Of course a whole bunch of states tried that once, and it didn’t really work out so well for them.
So yes, the so called ‘planetary scientists’ can defy the arbitrary distinctions made between categorizations, but is the rest of the scientific community likely to listen to them? Might we argue that the ‘planetary scientists’ have a vested interest in including as many objects under their purvey as possible? Is this why they’re upset?
Should we take this to the logical extreme and ask about the opinion of the plutoid scientists, I bet they’re nearly unanimous in their support for the new classification, otherwise they’re out of a job, right? If there aren’t any, then I will declare myself to be one… and yes, my convention is unanimous. Does this sound silly to you?
What if all the quartz scientists decided to break from the geologists and call their crystal of choice bauxite. Would it be ok? Would it REALLY be up to them?
Please, let’s do better than the current administration and keep our politics and turf wars out of science. What Pluto is called has ZERO bearing on what it is or what scientific discoveries can be made there. The fact that there are scientists spending their grant money having debates about the classification of a single object strikes me as a terrible waste of intellect. Why don’t we figure out how Pluto and other similar objects formed instead of debating what they’re called?
I’ll admit that the designation _may_ have some impact on what funding is available, and I’m betting that’s where the rubber really meets the road isn’t it.
August 25th, 2008 at 9:56 pm
Nobody may have argued when the IAU “self declared” ages ago, but the fact is, many people are arguing now in the wake of the huge mess the IAU has created, which has done more harm than good.
As new scientific discoveries are made, new fields of study develop that previously did not exist. Astronomy is now a very broad subject, and there is good reason to argue that planetary science has become its own specialty. This is very different from your example of quartz scientists deciding to break away from geology and create their own field based on one type of crystal. It is more akin to oceanography splitting off from geology and meteorology because the new area contains its own characteristics, properties, life forms, etc., enough to make it an entirely separate discipline. This is what is happening in astronomy now. People who study galaxies, black holes, stars of various types, cosmology, etc. do not deal with planets; their research is very specific to their areas of study.
The distinction between planetary science and general astronomy is not arbitrary. As to whether the rest of the scientific community will listen to a group of planetary scientists, the answer likely depends on individual scientists. We may well have a time when there isn’t one consensus on this issue. That is okay because we are learning so much so rapidly that much of what we know is in a state of flux and is likely to be subject to multiple reclassifications. For example, what happens if we find microbial life on Europa or Titan? How does that life get classified and by whom–biologists? Astronomers? Planetary scientists?
I believe that the process by which a body such as the IAU votes is very much a concern here. The fact that the IAU used a flawed process that ignored its own bylaws as well as the recommendations of its own subcommittee, that it made no provisions for absentee voting on such a public matter, show it to be insular, out of touch, and incompetent in creating an inclusive decision making process. In the US electoral system, we can all make our voices heard within the system. However, people who are not members of the IAU, even if their specialty is planetary science, have no means of having input into its decision-making process. The IAU is very selective in whom it admits to membership. Ironically, Clyde Tombaugh, discoverer of Pluto, would not have been eligible because he did not have a PhD, yet he was clearly one of the best astronomers of his day. Also, the IAU leadership has been very contemtuous of public reaction to its decision. They may think public sentiment does not matter, but if so, they are forgetting who funds astronomy in most countries–the taxpayers. If they keep up the condescending attitude toward public opinion, IAU members just might find their projects de-funded by governments elected by an angry public.
If you want anyone to keep politics and turf wars out of science, you should be addressing the 424 IAU members who voted in Prague. Several French astronomers openly threatened that “Pluto is going down because we don’t like American policy in the Middle East.” Anti-American sentiment loomed large in the vote because Pluto was discovered by an American and is viewed by many as an “American planet.”
A great deal of the General Assembly in Prague was a political battle between dynamicists, who define objects by where they are versus planetary scientists, who define objects by what they are. The dynamicists staged a “revolt” in the latter days of the conference, when everyone else had already left, with the specific goal of imposing their definition on the entire group. In fact, one of the leaders of this “revolt” was quoted as saying that if dwarf planets are counted as planets, his life’s work would be ruined! One could make a case that much of what happened in Prague was due to “turf wars,” which is just another reason why that vote should be overturned.
I don’t believe anyone would be out of a job based on his or her position on Pluto. And even scientists who supported the original demotion admit the IAU definition is sloppy and have almost nothing positive to say about the “plutoid” classification. There are also funding implications here. New Horizons likely would not have been funded if Pluto had been considered an asteroid. In practice, demoting Pluto consigns it to a secondary category that will be viewed as far less important and significant and therefore less likely to be studied.
Why all the attacks on planetary scientists as the ones having vested interests? One could reasonably argue this is true across the board. However, planetary scientists are interested in very specific types of objects–those in hydrostatic equilibrium and those rocky bodies that are not, namely the asteroids. They are not looking to tell astronomers who study quasars or pulsars how to define those phenomena and simply want the same courtesy in return. Shouldn’t those who spend their life studying planets be the ones to define what a planet is? And shouldn’t any group making decisions with worldwide implications be using a far more open process than the IAU is currently using?
August 26th, 2008 at 7:12 pm
Nobody’s making any attacks here! I simply stated that we have to be careful of vested interest on both sides of this debate.
In the end we seem to agree that this ‘debate’ is about hurt feelings and reputations and NOT ABOUT SCIENCE.
I think that was my point from the beginning.
August 26th, 2008 at 11:36 pm
I simply wanted to clarify that there much political motivation on the part of those who pushed for a planet definition that excludes Pluto. I agree that very little science was involved in the Prague General Assembly. However, I can speak for the event I attended two weeks ago and vouch for the fact that a great deal of scientific education and discussion took place there.
In the end, you, I, and the general public may actually be the ones to determine what the term planet means. Many scientists, educators, and members of the public have simply ignored the IAU definition. Witness the new National Geographic book titled “Eleven Planets” that includes the eight classical planets and the three dwarf planets all under the umbrella of planets. If enough people ignore the IAU definition over a long enough period of time, it will likely become irrelevant. Even the IAU acknowledges that public usage could very well render its definition meaningless.
August 27th, 2008 at 6:31 am
Make sure to see James Cronen’s discussion on classification.
Laurel: I have to admit that I’m curious, why are you so invested in this? Is this simply a “just cause to be championed” or do you have some direct personal tie with planetary science and/or Pluto? You seem to be taking this whole debate rather personally, while I admit to finding the whole “debate” rather silly. More of a media darling public interest story than a real scientific issue.
Again, thanks for the discussion. We will see if the court of public opinion wins out or if the few succeed in their “rampage” against Pluto. In the end, after humans and our naming conventions are long extinct, the rock we call Pluto will still be wobbling around the star we call “The Sun” (assuming we don’t discover it’s made of sweet crude and mine it out existence).
August 27th, 2008 at 12:05 pm
Chris, I have always had an interest in the solar system and planetary science, and since the day of the IAU vote, I’ve felt strongly that their decision was wrong on multiple levels. It’s not a matter of “taking it personally” or viewing this as simply “a cause to be championed.” As a child, I loved learning about the planets, and I want both children and adults to experience the same wonder that I did and learn about ALL of our planets, including Pluto. Today, as a writer, I believe I and other writers can provide a perspective on definitions and language that is lacking among many astronomers, especially in the IAU. And I don’t like the way the IAU operates as a closed, insular group that gives no credence or respect to public opinion. How people are educated about the solar system should not be left solely to the decision of this tiny insular, group. I tend to be passionate about everything that matters to me, and when I see something I believe is wrong, I fight it as hard as I can. I belong to an amateur astronomy club, and everyone there is passionate about some aspect of astronomy (not necessarily Pluto), and I think this is a good thing, certainly better than the preoccupation with “celebrity gossip” so prominent in our culture.
I most certainly agree with your last sentence. Pluto will outlast us all. That’s part of the fascination many of us have with these celestial objects. Their endurance long beyond any of our lives cannot help but evoke a sense of immortality and transcendence.