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An artist's impression shows Pluto with its largest moon, Charon, facing a distant sun.
Who killed Pluto? Who said it was dead? The dwarf planet is still kicking, thanks to a new book by its "killer" as well as new rounds of research that reference the icy world.
The Pluto-killer, of course, is Caltech astronomer Mike Brown -- who along with his colleagues found a world on the solar system's icy frontier that outweighed Pluto. The discovery of that bigger world, now known as Eris, set off an international debate that led to Pluto's removal from the International Astronomical Union's official list of planets in 2006.
Brown (whose Twitter handle is @plutokiller) tells the story of the planet quest and Pluto's setbacks in a book titled "How I Killed Pluto and Why It Had It Coming." But the book is as much about his own life as a scientist and a father. Brown's daughter, Lilah, was born during the very time that his biggest scientific discoveries were coming to light.
Brown told me it would have been "impossible" to tell the scientific story without including the story of Lilah's birth and babyhood. "They are so intertwined in my life that I can't help but mix them," he said. "Lilah's birth and the mere fact that she was a week earlier than I anticipated changed the way some of the astronomy happened. I couldn't tell either story without mixing the two together."
Even as the book was being written, Lilah was drawn into the Pluto drama.
"When she started being conscious of the book and the title of the book, she didn't really think much about whether Pluto should be a planet or not, but she was pretty sure that killing was bad," Brown said. "And so maybe six months ago, she became angry at me for having killed Pluto. She would tell me that killing is bad, and I shouldn't do it, and I should make Pluto come back. I should unkill Pluto."
Bob Paz
Caltech astronomer Mike Brown is the author of "How I Killed Pluto and Why It Had It Coming."
Brown said Lilah eventually reconciled herself to her father's ways. She told him to keep looking for a new planet -- and if he ever found one, would he please name it Pluto? Now that the book has finally come out, she's positively proud of her planet-killing pop. "She's no longer mad at me," Brown said. "Now she goes around and tells everybody that her daddy killed Pluto."
The 45-year-old professor said his 5-year-old daughter has done a good job of winning over her peers. "The kindergartners all think it's great," Brown said. "The parents are a little less sure what to think."
I can't help but imagine Lilah as a rebellious teenager, wearing a "Save Pluto" T-shirt just to spite her father. That might liven things up at the Brown household: Mike Brown said he feels a continuing obligation to explain why it makes the most sense to think of the solar system as having eight planets, plus smaller non-planets that just happen to include Pluto and the half-dozen or so worlds he has had a hand in discovering. After all, that's why he wrote the book.
"I would be very glad to be done with it," he said of his Pluto-killing role. "I do actually think that these issues and these questions and these conversations are profound for our solar system, so I think they're worth having. I wouldn't argue, like some people, that they don't matter ... that they're just semantics. I do think they matter profoundly. So as long as the discussion is continuing, then I think I will feel the need to be part of it."
You might think Brown would be more interested in boosting the status of the worlds he found. In the book, he tells how his wife, Diane, tried to keep him from dissing his own discoveries. And in fact, for a while he was OK with seeing Eris as "the 10th planet." But as the debate continued, Brown came around to the opinion that the solar system's list of planets had to stop at eight.
Divisions in the solar system
It's not so much that Brown defends the IAU's controversial definition of planethood. Brown said the definition was "pretty crummily written" but nevertheless ended up expressing the right concept. For Brown, the bottom line is that the eight largest things that go around the sun are in a special category for which the name "planet" should be reserved.
"Right now in the solar system, we are perhaps lucky, or perhaps it's a matter of physics ... but we have a solar system that draws a very strong line between the eight largest objects, which are in circular orbits and dominate the solar system; and everything else, the next biggest thing being Pluto or Eris, flip a coin. That division is easy to see and to make," he said.
"The funny thing that will happen is if there is something out there that someone finds that breaks that very clear division," Brown continued. "Something bigger than Mercury that is in a non-circular orbit and kicked around by the giant planets. It seems almost inevitable that something like that is out there. ... And when that object is found, it won't be a question about Pluto at that point, it will be a question of, 'OK, what is this?' It is going to be a difficult argument to say that something that's bigger than Mercury shouldn't be a planet. I'll make it, but I'm not sure I'm going to win that one."
Brown said he's still on the hunt for just that type of planet, somewhere on the very fringe of the solar system, "because there's nothing more fun than making astronomers argue all over again." He's involved in the SkyMapper project to survey the Southern Hemisphere's skies from Australia -- a celestial frontier that's not been as thoroughly explored as northern skies.
Pluto in the press
Of course, Brown doesn't have to wait until something bigger than Mercury shows up to have an argument, or at least a discussion. For some reason, Pluto and its little pals just keep coming up as topics for astronomers to talk about:
- A month ago, astronomers reported that they took a fresh set of measurements for Eris' size, and came to the conclusion that it was about the same size as Pluto or perhaps even a bit smaller. Brown noted that the comparative size "doesn't matter at all" when it comes to the dwarf planets' status in the solar system. What's more, Eris is known to be about 25 percent more massive than Pluto -- which would suggest that the two worlds have different compositions.
- In contrast, the similarities between Pluto and Eris are highlighted in an article appearing in Nature this week. The article was written by Alan Stern, a planetary scientist at the Southwest Research Institute who heads up the science team for NASA's New Horizons mission to Pluto. Stern observes that the surface composition of the two dwarf planets are "surprisingly similiar," with the abundance of nitrogen at 90 percent or more, and methane at 10 percent or less. The similarities extend as well to Triton, a moon of Neptune that is thought to have originated in the same zone that gave rise to Pluto and Eris. Stern said recent reports suggest that New Horizons' findings "will be of relevance to a broader suite of small planets common to the outer solar system."
- Just today, researchers reported in the journal Science that some of Earth's precious metals must have been left behind by a collision with a Pluto-sized celestial body 4.5 billion years ago. The lead researcher, Bill Bottke, is a colleague of Stern's at the Southwest Research Institute. "The populations that were hitting Earth, the moon and Mars were pretty top-heavy," Bottke told Space.com. "Most of the mass was in the big guys." Big guys? He's talking about Pluto-sized objects, right?
Such references demonstrate that Pluto isn't dead yet. Lilah Brown needn't have worried so much about her father's murderous ways: Pluto is still out there, secure in its orbit. Scientists (including Brown) are still fascinated by dwarf planets and seeking to learn their secrets. Regular folks are fascinated by the story of Pluto's ups and downs -- which is why people keep writing about it. That goes for Brown's book as well as my own, "The Case for Pluto," which takes up the other side of the argument.
The interest in Pluto and its kin is likely to rise even higher in 2015 -- when New Horizons is due to fly by Pluto while NASA's Dawn probe settles into orbit around another dwarf planet, Ceres in the asteroid belt. (Dawn's rendezvous with the asteroid Vesta is likely to be one of next year's astronomical highlights.)
Brown's book provides yet another opportunity to read about, think about, and talk about how we see the cosmos around us -- and whether you think Pluto is dead or alive, that's a good thing.
More about 'How I Killed Pluto and Why It Had It Coming':
- Bad Astronomy: How to settle the 'What's a Planet' debate
- On Point: The man who killed Pluto (and other space odysseys)
- Universe Today: Q&A with Mike Brown, Pluto killer
- Daily Kos: How I killed Pluto
- New York Times: When a heavenly body got the boot
- The Atlantic: Read an excerpt from 'How I Killed Pluto'
More about 'The Case for Pluto: How a Little Planet Made a Big Difference':
- 80 years of Pluto
- A Pluto pilgrimage
- Pluto maps raise new questions
- Interactive: The new solar system
- More Cosmic Log coverage of Pluto
- Read an excerpt from 'The Case for Pluto'
Correction for 2 p.m. ET Dec. 10: I think of the Southwest Research Institute so much as SwRI that I mistakenly wrote Southwest "Regional" Institute. Thanks to Brent Markus for pointing out the error.
Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter.
Leave a Comment:
I'll buy the hopefully rebellious teenager a "Save Pluto" shirt myself if she even shows the hint of wanting one. Interestingly, I have been talking to kindergartners through my astronomy club and to second graders through my nephew's class winning them over to the pro-Pluto side of the argument. My seven-year-old nephew has been busy educating his classmates that our solar system does not have only eight planets.
What Brown does not consider is that the line between the eight largest objects in our solar system (not all are in circular orbits; Mercury's is somewhat eccentric) does not mean the other spherical objects are not planets. It just means they are a different kind of planet. Similarly, terrestrials and jovians are very different. One could easily argue Earth has more in common with Pluto than with Jupiter. Jupiter has no solid surface and is composed mainly of hydrogen and helium like the Sun. It has its own "mini-solar system" going. Pluto, on the other hand, is estimated to be 75 percent rock, has a solid surface, has a nitrogen atmosphere, and has a large moon formed via giant impact just like Earth does. The line dividing the terrestrials from the jovians is just as strong as the line dividing these two from the dwarf planets. That still doesn't mean all three classes of objects are not planets.
I take issue with making Lilah so much a part of the story. Every other book I have read about Pluto, including Neil de Grasse Tyson's, has never gone off on such a tangent. Tyson discusses children in terms of the Hayden Planetarium but does not try to give special attention to his own children. This seems way too much like using a child for self-promotion.
I also have two questions for you, Alan. First, will you read my book and interview me when it comes out, provided I get it out before the world ends in 2012? :) (Just kidding with the 2012 thing.)
Also, I would like to be involved in searching for large KBOs through the SkyMapper project surveying the Southern Hemisphere's skies from Australia. Who would you recommend I contact about getting involved? This is a serious interest of mine, and if I can make use of contacts through Swinburne University in Melbourne, where I am studying astronomy, please let me know.
Well, Laurel, first I would like to point out that you yourself "use" children for your own agenda so I don't really understand why you take such issue with Brown's story. Your nephew doesn't have the knowledge that you have, he only has what he has learned in school and from you and whatever he's learned elsewhere. From the way you describe it the "winning them over" sounds more like you projecting your opinions on those kids. As adults that's pretty unavoidable and I'm too far removed from your situation to make a judgment so I will not do that. But I did want to point out that you are influencing children with your passionate opinions about Pluto, so there it is. Brown wrote a story about his experience, I've not read his book and I am wondering if you have? If you have then I will respect your opinion of taking issue with Brown's story. If you have not then why would you take issue with it? I will just assume that you have read the book and leave it at that.
Kudos on writing a book. I am curious about the subject matter, does it deal with Pluto or astronomy in anyway? If so I would probably be interested in reading it.
I don't know if you've seen this but it might help you in your endeavor to get involved in the Skymapper project. http://www.mso.anu.edu.au/~stefan/skymapper/policies.php
Culture trumps jealous definitions, that is why Brown (good job Brownie!) will be forgotten and "Pluto the planet" never will. Brown, Shut Up and go away. Go where the sun never shines before you diss more discoveries by your betters.
What's more interesting to me than the debate over the science of classifying large bodies in space as planets or not is the amazing amount of contrived affection people have for one of those bodies. Seriously consider what you are getting so worked up about...whether or not some billion mile away rock spinning around should be called a planet, dwarf planet, or otherwise. It reminds me so much of the classification of a tomato as a fruit or a vegetable.
Look at grant-2780368 for instance...he is willing to tell another person to "Shut Up" and to go where the sun doesn't shine just because someone has a difference of opinion on whether Pluto is a fruit or a vegetable. Really grant-2780368 do you love Pluto so much that you take such vile affront to it being classified slightly differently?
Doesn't this part of the discussion strike anyone else as the more interesting aspect of the topic?
No doubt about it - Pluto is a fruit.
Yes, it's an interesting phenomenon ... I do think there's some resistance to shifting your mind around a new concept. Intellectually, though, I think it's wiser to expand the concept of planets rather than contract it ... or at least keep it open. Brown says what's important is the concept rather than a legalistic definition, and on that I agree. But in his view, the word "planet" should be reserved only for the biggest and most important things in a planetary system, whereas others (including myself, but also more knowledgeable people) would go for a definition that's based on the physical characteristics of the thing at issue. Does it have differentiated layers, and geological activity, Is the surface differentiated? Does it have atmosphere and weather? It's thought that Pluto has all these things, and most likely Eris and other dwarf planets do, too. Sure, so do moons such as Titan and Enceladus. That's why they're known as planetary bodies. (Some folks get all tangled up in the moon vs. planet distinction, but I think that's pretty clear ... much clearer than the distinction between planets and, um, less differentiated celestial objects.
HaHa!! Let's make T-shirts - "Get 5 servings of Fruits and Vegetables. Eat Pluto!"
Indeed the passionfruit that goes into this debate can sometimes be fruitful, but often times it just turns rotten.
Something that happened at the same time and doesn't get much debate (probably not really much interest in talking about it) is the fact that there is the Sun, the Planets, the Dwarf Planets, and everything else is lumped together as "Small Solar System Bodies".
@Alan Boyle Just a small correction: "Southwest Regional Institute" should be "Southwest Research Institute"
@Laurel Kornfeld I think you might enjoy Dr. Brown's book more if you view it as an Autobiography of a short period of time in his life, rather than as a book about Pluto being categorized as a Dwarf Planet. Also, what's your book on?
Urk! Thanks, don't know why I wrote that!
It should be simple. Planets are spherical bodies which circle stars. Satellites are spherical bodies which circle planets. So Pluto is a planet. Yes, Pluto is small. Mercury is small compare to Jupiter. So Mercury is not a planet? Pluto even has a satellite. Pluto, you are alive. I can feel your magnetic core form here!
@Willbo-2780431 I really like your definition of planets and satellites. Its simple, concise and works without much debate!
I don't agree with Willbo's definition. What about comets?
Comets are not spherical; they are not massive enough to be pulled into a round shape by their own gravity.
And more importantly it does not work well without debate. For example, Why do satellites have to be spherical? Have you seen the large majority of moons in the solar system? Potato shaped is certainly less that spherical, but still constitutes a moon. Does Pluto's "moon" Charon really qualify as a moon or is that a binary planet system since they both orbit around a center of gravity that is outside the core of Pluto?
I agree... Satellites, as in moons, needn't be spherical. They just orbit around a larger object (that's not the sun). The idea that Charon and Pluto are double planets was one of the things that led to the demise of the definition that was initially proposed. In fact, Brown says he suspects that if the Pluto-Charon footnote weren't included, the original definition (which would have kept Pluto in the planet category and added Eris, Ceres, etc.) would have gone through.
I sseriously doubt that this "scientist" really understands what a non-accomplishment he made by helping to invent the term "dwarf planet". This is a word game, not a scientific achievement.
"Buy my book! I have an adorable daughter! I am a scientist! My daughter makes this book full of cuteness and lolz!" I question the science of a man whose "discovery" seems shaped by a non-relevant event such as the birth of his daughter. It has nothing to do with the definition of astrological entities. Get over yourself man. You discovered nothing, you just made up a word and want attention for it because you know it's controversial.
There seems to be a lot of hate directed at Brown over this issue, probably stemming from some false sentimentality over Pluto. I think we're going to discover a lot of different planets out there as our understanding increases, and we'll see planets based on physics we had not previously comprehended.
Someday, the notion that "everything is a planet" will be looked back at as a cute but simplistic way of looking at things that can only be explained to future generations as "from where they stood at the time, it made sense". Like heliocentrism.
Absolutely ... we'll be discovering a lot more about planets in other solar system. I'm sure the idea that planets have to be in solitary, circular, planar orbits won't last much longer than a decade or two. We're already finding Saturn-size planets that dance around each other in a co-orbit, or are in extremely inclined and/or eccentric orbits. It's not the notion that "everything is a planet" ... folks agree that there are millions of objects out there that aren't planets. It's just the notion that planets can be in weirder dynamical situations than some might currently think.
I am writing a book about Pluto as well, but from the opposing point of view. The book is titled The Little Planet That Would Not Die: Pluto's Story, and the reason it's completion has been delayed to 2011 is because I have been studying astronomy at the graduate level and could not do justice to both my classwork and the book at the same time, as the classwork was very demanding. I am now taking some time off to concentrate fully on the book before returning to the graduate program.
My book will address the scientific basis for Pluto's planet status as well as the strong backlash against the demotion and cultural issues in attempting to explain why Pluto matters so much to so many people. Yes, it will be about astronomy, and no, it will not center around my nephew or any individual child.
Sorry, but I'm really not interested in reading about Lilah or Brown's personal life. Had he focused solely on the astronomy, this would not be the case. I did read Neil de Grasse Tyson's book even though I disagree with his position. Significantly, even Tyson now admits the debate over planet definition is not over.
Regarding my nephew and talks to kids, I should clarify one important element. When I talk to the kids, I first explain that this is an ongoing debate, and that there is more than one right answer. Kids often don't realize that scientists can disagree because they look at the same facts differently, with neither being wrong. When I say we have more than eight planets, I explain that anyone who presents an eight-planet solar system as "fact," is really just presenting one opinion. I discuss the other view, the view that dwarf planets are planets too and that our solar system has a large number of planets, and then encourage kids to read and decide for themselves what they think the right answer is. The idea is to not have them taught only the IAU view as gospel truth with their never knowing it remains a matter of controversy.
Also, Brown did not originate the term "dwarf planet." That was done by Dr. Alan Stern back in 1991, to designate a third class of planets, bodies large enough and massive enough to be rounded by their own gravity, a state known as hydrostatic equilibrium, but not large enough to gravitationally dominate their orbits. Stern never intended for dwarf planets to not be considered planets at all. Interestingly, dwarf planets are proving the most populous of all types of planets, just as dwarf stars (which are still stars) and dwarf galaxies (which are still galaxies) are each the most numerous of their types.
mob-barley, thank you for referring me to the Skymapper project. I will definitely look into it.
I do what I can Laurel, your welcome. (I have also wondered what I can do, although I don't have a background in science, I just enjoy the topic immensely)
I do have my own opinion about how we (as a society) should teach children. I have read quite a bit about ethics and for anyone who hasn't looked into it I highly recommend reading up on the history and philosophy of ethics. Anyways, when it comes to teaching children a subject like astronomy I think it best to just reveal what's out there. They'll ask what an object is called, and as teachers we'll give it a name. The naming is truly not important, what matters, ironically, is the matter - the objects- that are out there. There is the star and there is the stuff around the star. There is really no right or wrong when it comes to "knowing" the solar system. The solar system is there to be observed, what you call it all only matters when it comes time to discuss the objects in question. And it that sense the "right" way to label things is simply the way that is accepted by the participants of the discussion. So, that brings us back to Pluto. Kids know it's out there. You could call it a fruit, a veggie, a Planet, or a dwarf planet, but you'd really be better off just calling it Pluto.
When I think about kids learning in school I think about myself learning in grade school how the solar system was made up. I remember the drawing on the chalk board, and I think about how it must be different for today's kids. Unfortunately I don't know what children are actually being taught, I don't know if the teachers draw eight planets and leave out the asteroid belt, the dwarf planets, the TNO's, etc.. But that is my one fear about this whole "naming thing". The only problems would arise if some objects get lost or forgotten when it comes time to teach kids about our solar system. We all know that the education system has flaws, and we'd be doing tomorrow's scientists a disservice to spend time teaching personal opinions as opposed to simply teaching what are the characteristics of the solar system, the names of which can be anything.
I think this quote from Richard Feynmann is quite handy to this discussion:
"You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something."
You can call Pluto a planet or a dwarf planet, the classification matters little to science. What really matters is figuring out how it works, what it's like on Pluto and the other KBOs. How did these objects come into being? With more knowledge on that we can know how our solar system formed and evolved.
Or here's a video with relatively the same quote, but with more details:
http://www.youtube.com/watch?v=05WS0WN7zMQ
The whole "Pluto can't be a planet, because if we let it be a planet do you realize how many planets we'll end up having!?" argument has never appealed to me. Just because a few scientists don't want more planets than they have fingers to count on is no excuse.
I say "let 'em all into the club!"
Amen, Liberty Watcher ... It's like saying "we can only have eight mountains in the world, because mountains have to be big and important things."
Much Agreed! I vote we call them all planets. Could someone explain to me the importance of clearing out a planet's orbital path? I don't understand why that's part of the definition.
Mr. Barley,
It is very simple - the goal was to come up with a definition that excluded Pluto (and Eris, Makemake, etc...), not one that made any kind of objective sense.
Mike Brown should have been celebrated as the greatest planet finder in history. He should have been the modern hero of solar system science. He could have been the man that inspired millions of school children to be excited about science and discovery and his story used to show our children that there is still plenty yet to be discovered in science. But he is not, why?
First let's try to understand Mike Browns lack of hubris. In the modern university system outward displays of self promotion are to be avoided at all cost. (we have some schools eliminating class rank as to not hurt anyone feelings) So don't blame Brownie for his self-depreciating viewpoint. It would be professional suicide to do anything else. Think of the egos at Caltech. Think of this peer pressure.
Couple this fact with international jealousy (If you take the logical definition of a planet "a sphere that revolves around the Sun, ...." then 1/3 of the planets would have been discovered by Americans and this fact would be inscribed into the annals of science for eternity). This was something many other petty astronomers and bigoted anti-Americans just could not stomach. Therefore, we have this ridiculous planet definition, which is the equivalent of writing a definition for a bird that is made to exclude penguins or emus.
With the frequent discovery of exosolar planets and the huge variation that exists in our galaxy, this parochial IAU definition will under the clear facts of objective science be discarded.
Anyways, my daughter teaches her students that there are 12 known planets, so she will correct Mike's daughter's unsupportable viewpoint in a few years.
If it walks and looks like a duck ....