Thursday, November 12, 2009

Alan Boyle on Pluto

This will not go away and neither will unserstanding of the situation. Below is an interview between and science journalist [msnbc] Alan Boyle.

"Underdog Planet: Why We Love Pluto"


Betsy Mason

November 11th, 2009

WIRED SCIENCE Why does the public care so much whether or not Pluto is a planet?

Boyle: Some people say it’s because of the Disney dog, that kids that grew up with Pluto the pup just have a natural affinity for Pluto the planet. And that’s definitely part of it, but I think that there’s something more to it.

Throughout most of the history of that little world, we’ve thought of it as a poor little oddball that didn’t fit in with the rest of the kids in the solar system and really needed to be protected. So to my mind it’s really not so much about the dog, but it’s about the underdog. Why is it important to scientists whether we call Pluto a planet or not?

Boyle: Some scientists will go to the barricades to make sure that it’s called a planet and other scientists will resist that idea. I think when you get right down to it, I’m not sure the name makes a lot of difference in terms of the scientific study of these planets. It’s more a question of how, for example, the general public thinks about how our cosmos is structured.

There might be a slight difference in the way projects are funded if there’s a perception that these are just cosmic leftovers and they really don’t count for much in the solar system. That might have a marginal effect on what sort of space missions are funded, what sorts of observational campaigns are taken on. I think that the scientists are really keyed in on that. And even Caltech astronomer Mike Brown, whose Twitter handle is @plutokiller, even he is fascinated with these objects that are out there. How does Pluto’s planetary status affect how the general public views the cosmos?

Boyle: I think the case of the asteroids is a good illustration of what’s going on. When people memorized the nine planets they completely forgot about this string of small bodies, the asteroids. The biggest of these, Ceres, is now a dwarf planet. Strangely enough this whole controversy has elevated the profile of Ceres at the same time that it’s made people wonder a little bit about Pluto.

We’re finding out that for all sorts of reasons, the asteroids are a pretty important element in the solar system. They could be a great source of resources in the future. They could pose a threat as we’ve seen recently with July’s “Great Black Spot” — the collision of some object with Jupiter. And just this month there was a pretty significant bolide — what people think was an asteroid came into the atmosphere over Indonesia and was one of the biggest blowups that has been observed yet.

I think you can extend some of that example of asteroids to the far zone of the solar system as well. We really need to keep that in consciousness when we’re thinking about the solar system. If you limit your understanding of the solar system to just memorizing eight or nine names, you’re really missing out. So the asteroids and the rest of the outer solar system have benefited from Pluto being demoted?

Boyle: It’s kind of like what celebrities sometimes say, that I don’t care if you speak ill or well of me, as long as you spell my name right. The fact that people are finding this interesting enough to quarrel over helps put the spotlight on those regions of the solar system that were maybe in the shadows before. And I think that having a wider view of what you call a planet really helps to 1) emphasize the diversity in the solar system, and 2) keep in mind that there are very interesting objects that could be weirder than we imagined but still can fit into the planetary tribe. How was Pluto first discovered?

Alan Boyle: There had been another planet, which came to be known as Neptune, which was found by figuring out how the gravitational interactions of all the planets came together. They figured that there had to be something extra there.

So some people thought it was the same situation as after Neptune was found: There had to be some sort of extra gravitational pull. A lot of people theorized that there had to be another planet, Planet N or Planet O, P, Q or whatever. So this guy named Percival Lowell tried to find that planet but couldn’t do it. He died in 1916, and it took a while for the Lowell Observatory, which he founded, to get back into the search.

But eventually this guy named Clyde Tombaugh, a Kansas farm boy, started the search. Tombaugh was a really interesting guy because he was a very detail-oriented young man. He undertook a very meticulous, dedicated search of the parts of the sky that were imaged by the Lowell Observatory’s telescope, and eventually he found it just by sticking with it. At first they didn’t know what it was, people started talking about the ninth planet, and the rest is history. Where did the name Pluto come from?

Boyle: There were three names that had been bandied about. One was Minerva, but people found out there was already an asteroid named Minerva. One was Cronus, but astronomers at the Lowell Observatory decided that they didn’t want to name it Cronus because an astronomer they didn’t like came up with that name, and they were afraid that the astronomer would steal the credit if they used that name.

And the third name was Pluto. There had been talk about maybe if we found another planet, we would name it Pluto, and so that was definitely on the list. The bad thing about it was that there happened to be a type of laxative water known as “Pluto Water.” And so the trustee of the Lowell Observatory thought maybe that wasn’t the right name for it.

But, on the other hand, they did have this telegram from Britain where an 11-year-old girl named Venitia Burney had suggested this name. So there was really definitely a cute factor from the beginning of Pluto’s christening. And they went with that. And then the Disney dog of course. That added to the cuteness factor. Pluto was found in 1930, so why did it take until just recently to find any of these similar things?

Boyle: The simple answer is telescopes and patience. The telescopes had to be powerful enough to find dim objects on the edge of the solar system. And it also takes a lot of patience to do the sort of thing that Clyde Tombaugh did, where you compare pictures back and forth. So really, it took a couple of patient people, David Jewitt and Jane Luu, to get the imagery of the area where these faraway objects might be found.

They also employed computers, which were coming onto the scene, and the computers could automate these sorts of tasks. That has really revolutionized the field. It’s unimaginable that people could do this sort of astronomy without having high-powered computers to help with the task. Why do scientists care so much about Pluto?

Boyle: Pluto, when you look back at it, was actually the first object of the great third zone beyond the part of the solar system that people knew about: the inner rocky planets and the outer giant planets. Clyde Tombaugh was the first to find one of these icy worlds on the very rim of the solar system, and that sparked a lot of discussion about how it got there and how solar systems are created anyway. And whether you call Pluto a planet or a dwarf planet or a sleazy ice ball, you’ve got to admit that Pluto really pioneered the exploration of that icy zone of the solar system and helped us to find the ice worlds, the rings of ice that exist in other solar systems as well.

So naturally astronomers want to find out more about this frontier, and there are a lot of interesting attributes. It could have been the place that provided the building blocks for life. It could be the last redoubt of life millions of years from now when the sun gets big and hot. There’s a lot to look at in that area of our solar system, and it sparks great questions about what’s happening in other planetary systems as well. What does it take to qualify as a planet now?

Boyle: The way the [International Astronomical Union] sees it, it’s an object that’s going around the sun and has the mass sufficient to crush it into a round shape — so-called hydrostatic equilibrium. And then you’ve got the standard that it has to have cleared out its orbital neighborhood. And that is the standard that caused all the controversy and continues to cause all the controversy.

Even people who were kind of in favor of the way the IAU decision turned out admit that that standard really needs to have some work done. It depends on how you define the neighborhood, and how you define the biggest thing in the neighborhood. Arguably, Pluto could be the biggest thing in its zone because it makes as much as 7 percent of the Kuiper Belt by mass.

Some researchers have tried to come up with a quantifiable way of defining that “clearing out the neighborhood” standard, but there is some strangeness involved in that. For instance, if you were to put Earth out where Pluto is, it would not be considered a planet. So a lot of people say that any standard that does not have an Earth-size object as a planet is not an acceptable standard. But that sparks a whole new debate over whether Earth would exist or if it’s possible for an Earth-size object to exist in that kind of environment.

That gets into the whole question of Planet X — the idea that there might be a pretty significantly massive body out in the even farther reaches of the solar system known as the Oort cloud. The folks who are trying to shore up the IAU standard argue that such a planet, even if it was as big as Earth, could not be considered a planet. They’re trying to come up with another term for that kind of body, for example calling it a scattered planet. It’s a little tricky to work out all the implications of this somewhat confusing standard. How many fellow dwarf planets does Pluto currently have?

Boyle: Right now, going by the IAU’s criterion, there are four dwarf planets in the Kuiper Belt, in that far zone of the solar system. And then you have one in the asteroid belt — that’s Ceres. So there are five in all, including Pluto. It could be that there are more. We’re using the IAU criterion here that a dwarf planet is something that is massive enough to crush the object into a round shape, but that the object is among other objects at the same orbital distance — they don’t meet the so-called clearing-out-the-neighborhood standard. What happened at the IAU meeting in Prague in 2006 that led you to name a chapter of your book “The Battle of Prague“?

Boyle: It just really demonstrates how political the scientific process can get. When you look at the deliberations that came before the general assembly and the maneuvering that came during the general assembly, it reads almost like one of these political novels where one side is trying to put forward one idea, and the other side becomes the opposition and uses the bureaucratic process to do a little bit of jujitsu and get the outcome that they wanted. Will Pluto ever be a planet again?

Boyle: The IAU, I don’t believe they have any intention of touching this issue again with a 10-AU-long pole. They don’t want to get into this again. It was so divisive and so unpleasant. I think it will be a long time before the IAU goes anywhere near trying to define a central concept in science like this again.

And then on the other side, some people might ask, ‘Why don’t the defenders of Pluto’s dignity come out and try to get it reversed by the IAU?’ And the answer is that these are the very people who say the IAU has lost their legitimacy. So it would be like someone saying that such and such a tribunal is a kangaroo court and we can’t get a fair hearing there, and then the next year coming back and trying to get something from that very same court. It just wouldn’t work. Where do you stand on Pluto’s planetary status?

Boyle: I would say that it should be considered a different kind of planet. I’m fine with calling it a dwarf planet or a minor planet or whatever. But I don’t think that it’s really the right decision to say that dwarf planets are not planets. I think that is what’s going to confuse people.

I really favor having a big tent for the planet category, and it’s OK if you have 50 or 100 or 200 or 500 planets out there. These things that are massive enough to have a round shape have lots of important characteristics that bring them together into a very broad category. The point is not so much, ‘Gee it’s in a nice round shape.” The point is that when you have that massive of an object you have differentiation, you have the potential for geologic activity. People think that there might be ice volcanoes on Charon, there happens to be an atmosphere on Pluto — these qualities are things that are central to planetary science. So I think it would be wrong to try to make this formalistic how-many-pigeon-holes-do-you-have type of decision on this very central term in planetary science. What was your gut reaction when you heard Pluto had been demoted?

Boyle: I was intrigued. One of the stories I worked on in the wake of that was, what’s this going to do to all the websites, all the textbooks, all the toys that are out there? Are people suddenly going to be selling just eight planets in their solar-system kit rather than nine?

I did think that it was kind of a done deal, that OK, the decision’s made and we’ll just kind of move on, and sure, there are problems but they’ll get ironed out as time goes on. I said so in the Cosmic Log, that no matter how you stand on it, now that the IAU has spoken, that’s gonna be something that scientists and the general public are going to have to live with. That’s when I heard from the people on the other side of the question who said it ain’t over yet. And I found that intriguing, that even though an authoritative body spoke out on this, there was still debate that continues to this day.

So that’s an interesting phenomenon in science to see that. There are parallels to other controversies, over stem cells or climate change or whatever. And it illustrates that science is not something that’s decided by a vote. It’s almost like you have a quantum state of superposition where something is a planet and is not a planet at the same time, and it takes a while for it to collapse into one state or the other.

I think it’s still a little bit up in the air. We have some uncertainty about this whole question yet. And I think that will continue at least until 2015 when the New Horizons probe goes to Pluto and people see with their own eyes what this thing, whether you call it a dwarf planet or a planet or whatever, what this thing looks like. Will Pluto’s status affect how we handle planets outside of our solar system?

Boyle: Of course there are about 400 extrasolar planets that have been found right now, and some of them are as weird as Pluto, if not weirder. There’s one planetary system where you have two planets that are about Saturn- or Jupiter-size that are stuck in the same kind of resonance that Pluto and Neptune are stuck in, and it’s fascinating to see. This is obviously a planetary system where neither planet can clear out its orbit and yet they’re both considered planets.

So it’s another argument for not trying to get too precise about how you define a planet at this point. That’s going to be a big thing going forward with Kepler and Corot and all the exoplanet searches: As we see more diversity in planets, I think that will cause us to rethink our basic concepts on this whole question of planets.

The Case for Pluto: How a Little Planet Made a Big Difference


Alan Boyle

ISBN: 978-0-470-50544-1

Excerpt from by The Case for Pluto by Alan Boyle.

"The Fight for the Ninth Planet"


Alan Boyle

November 11th, 2009


If there’s still someone out there who thinks science and politics never mix, the story behind the Battle of Prague should change your mind.

Some have cast the debate that took place in the Czech capital during the summer of 2006 as a battle against American scientists who wanted to keep the only planet discovered by an American on an unreasonably high pedestal. On the other side of the argument, there are those who suspect that the rest of the world wanted to see Pluto demoted to punish America for its unpopular foreign policy.

But we’re not talking about that kind of politics. We’re not even talking about a battle between the fans and foes of Pluto per se. Instead of thinking in terms of Republicans versus Democrats, or Plutophiles versus Plutoclasts, you have to think in terms of planetary conservatives versus liberals — or, more accurately, dynamicists versus geophysicists. The skirmishes over the definition of planethood that took place in Prague weren’t so much about poor little Pluto, but about two different ways of seeing the solar system.

One way focuses on the dynamics of a planetary system: How are things moving around, and how do those things affect one another? If a celestial body doesn’t have much of a gravitational effect on other bodies, that object is hard to detect and hard to track. If lots of celestial bodies are in similar orbits, they all tend to blur together.

Pluto may be the solar system’s brightest object beyond Neptune, as seen from Earth. It may account for as much as 7 percent of the entire mass of the Kuiper Belt, a ring-shaped region that covers more real estate than the space inside Neptune’s orbit. But because there are lots of other objects in the Kuiper Belt, dynamicists see a crowded celestial neighborhood in which Pluto doesn’t stand out.

Much of what astronomers have learned about the solar system since William Herschel’s day has come to light because of dynamical analysis. This is how Le Verrier and Adams found Neptune. It is how Clyde Tombaugh could figure out how far away Pluto was, even though he saw it as a mere speck of light. And seventy-five years later, it is how Mike Brown identified Xena, the dynamical blip that was farther away and bigger than Pluto. So you can’t really sell the dynamicists short.

Another way of looking at a celestial body would be to look at it rather than around it. What’s it made of? What kinds of geological processes are at work? Does it have a crust and a core? Is there an atmosphere, and weather? Are there volcanoes, and if so, what are they spewing out? Water? Sulfur? Methane?

Such a world doesn’t have to be a planet to be of interest. In fact, some of the most interesting worlds nowadays aren’t planets, but moons. The Saturnian moon Enceladus is just 300 miles wide, far smaller than Pluto’s diameter of 1,430 miles, but it boasts geysers that could conceivably be spewing life- laden water.

This is the province of the planetary scientists — a breed of astronomers who focus on the way a world is put together. As a rule of thumb, if it’s big enough to crush itself into a round shape due to self-gravity, it’s big enough to be a planet. If it’s not big enough to get round, it’s a failed planet, taking on the potato or peanut shape normally associated with asteroids or comets. “These objects that we call planets have shaped themselves into spheres,” said Alan Stern, the planetary scientist who worked for seventeen years to get a probe sent to Pluto.

The significance of the shape isn’t merely that a round object makes for a pretty, planetlike picture. Rather, the important thing is that such a degree of self-gravity makes it possible for a planet to have a layered composition, an active geology, perhaps even volcanic activity beneath the surface, or an atmosphere above. “It’s about the physics,” Stern said.

Stern likes to talk of a Star Trek test for planethood: “The Starship Enterprise shows up at a given body, they turn on the cameras on the bridge and they see it. Captain Kirk and Spock could look at it and they could say, ‘That’s a star, that’s a planet, that’s a comet.’ They could tell the difference.”

Roundness would provide an instant way for Mr. Spock to tell. In contrast, Stern said, having to determine whether the round thing was one object among others at the same orbital distance would force Spock to put Kirk’s question on hold: “We have to make a complete census of the solar system, feed that into a computer, and do numerical integrations to determine which objects have cleared their zone.”

For dynamicists, roundness just doesn’t cut it. If Kirk and Spock are looking at a point of light from tens of AU away, as Clyde Tombaugh did in 1930, they might not be able to tell if the object they’re looking at is round. But by closely monitoring its motion, and the motion of other bodies, they could figure out where everything fits in a planetary system — even if it takes sixty or seventy years, as in the case of Pluto and the Kuiper Belt. “We dynamicists know all about the orbits and can say what’s going on,” Brian Marsden said, “but the physical people can’t say a damn thing.”

This back-and-forth between the dynamicists and the geophysicists was what stymied the initial efforts to resolve its planet problem. Whenever the question was considered by the nineteen members of the International Astronomical Union’s Working Group on the Definition of a Planet, one faction would essentially filibuster the other. “Achieving a consensus among them was about as hard as trying to herd a group of 19 feral cats into a room with several open doors and windows,” said Alan Boss, an astronomer at the Carnegie Institution of Washington who was a member of the panel. In addition to the scientific differences, there was a cultural split as well, having more to do with language than physics: Should the planets of the solar system be a category so special that you can count their number on two hands, or would it be okay if the category was open-ended, with the potential of adding tens or hundreds or thousands of members?

For planetary conservatives, the idea of recognizing even thirty or fifty planets in the solar system was just too much. The liberals, however, were fine with having hundreds of planets. You could break that category down into subcategories: giants like Jupiter, terrestrials like Earth, and dwarfs like Pluto. And even if you had scores of planets, you wouldn’t have to force kids to memorize them all, just as you don’t force them to memorize all the world’s rivers or mountains.

All these issues — the scientific as well as the cultural considerations — were dropped into the lap of a brand-new panel set up by the IAU in preparation for the Battle of Prague. This seven-member panel included five astronomers who were familiar with the issues but not counted among the leading Plutophiles or the Plutoclasts: MIT’s Richard Binzel, the Universit é Denis Diderot’s Andr é Brahic, Junichi Watanabe from the National Astronomical Observatory of Japan, Iwan Williams from Queen Mary University of London, and the IAU’s president-elect, Catherine Cesarsky. Another member was science writer Dava Sobel, the author of Longitude, Galileo’s Daughter, and The Planets. The chairman was Owen Gingerich, an astronomer and historian who worked alongside Brian Marsden at the Harvard-Smithsonian Center for Astrophysics.

In April 2006, the committee was told to come up with a definition of planethood in time for the IAU’s triennial general assembly that August, and to keep its deliberations secret, to avoid the kind of sniping that had stymied past efforts.

Gingerich tried to avoid dwelling on the particulars of Pluto’s case. “We never asked who wanted Pluto in or out,” he said. But the ground rules favored an approach that would lean more toward the geophysicists than the dynamicists. “We wanted to avoid arbitrary cutoffs simply based on distances, periods, magnitudes, or neighboring objects,” he said.

After flurries of e-mails, the panel met in person to hash out their decision in June at the Paris Observatory, where Le Verrier had once worked to calculate Neptune’s orbit. According to Gingerich, it didn’t start out smoothly. “On the second morning several members admitted that they had not slept well, worrying that we would not be able to reach a consensus,” he reported. “But by the end of a long day, the miracle had happened: we had reached a unanimous agreement.”

The resulting definition emphasized Stern’s roundness requirement, but also distinguished between the solar system’s “classical planets” — that is, the planets identified before 1900— and the “plutons” in the Kuiper Belt. Any world that orbited the sun and had a roundish shape due to its self-gravity, a state known as hydrostatic equilibrium, would fit under the definition of a planet.

But what if the planet’s shape couldn’t be seen in detail? In that case, there was a rule of thumb based on estimated diameter and mass: Objects at least 800 kilometers wide with masses of at least 5 x 10 20 kilograms, or about 4 percent of Pluto’s mass, would be brought into the planet fold, with borderline cases decided as further observations became available. That would put Pluto as well as Xena in the pigeonhole for planets, along with the eight bigger planets and smaller Ceres, the rocky world that was hailed as a planet in 1801 but reclassified as an asteroid decades later.

And what about Charon? Pluto’s moon is nearly half as big as Pluto itself, and so, unlike every other planet, the two worlds actually orbit a common center of gravity in space, like two stars in a binary system. Some astronomers thought that would qualify Pluto and Charon as a binary-planet system, and that’s what the earlier IAU panel on planethood had suggested in a footnote to their report.

“That footnote in the previous committee’s report got stuck in without my quite realizing it,” Gingerich said. It was one of several twists in the deliberations that he would come to regret.

Another twist had to do with the hush-hush nature of the panel’s work. The IAU’s Executive Committee insisted that the resolution be kept secret until the Prague meeting began. “It worked out that keeping it secret, in effect, backfired,” Gingerich said. Word that Pluto would stay in the planetary fold leaked out a few days before the Prague meeting — and although the members of the panel thought their proposal would be widely accepted, others had grave doubts.

Boss recalled the tempests he and his colleagues had weathered during past discussions of the planethood issue. In an interview with the journal Nature , he predicted that a definition based on roundness would be met with “a long line of people waiting for the microphone to denounce it.” And he was right.

Mike Brown did it...bad Mike Brown

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