More Surprises From Pluto

by Jason Major on April 24, 2011

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Artist's illustration of Pluto's surface. Credit: NASA

Ah, Pluto. Seems every time we think we’ve got it figured out, it has a new surprise to throw at us.

First spotted in 1930 by a young Clyde Tombaugh, for 76 years it enjoyed a comfortable position as the solar system’s most distant planet. Then a controversial decision in 2006 by the International Astronomical Union, spurred by suggestions from astronomer (and self-confessed “planet-killer”) Mike Brown*, relegated Pluto to a new class of worlds called “dwarf planets”. Not quite planets and not quite asteroids, dwarf planets cannot entirely clear their orbital path with their own gravitational force and thus miss out on full planetary status. Besides immediately making a lot of science textbooks obsolete and rendering the handy mnemonic “My Very Eager Mother Just Served Us Nine Pies” irrelevant (or at least confusing), the decision angered many people around the world, both in and out of the scientific community. Pluto is a planet, they said, it always has been and always will be! Save Pluto! the schoolkids wrote in crayon to planetarium directors. The world all of a sudden realized how much people liked having Pluto as the “last” planet, and didn’t want to see it demoted by decision, especially a highly contested one.

Yet as it turns out, Pluto really may not be a planet after all.

It may be a comet.

But…that’s getting ahead of ourselves. First things first.

Discovery data showing carbon monoxide spectrum. Credit: J.S. Greaves / Joint Astronomy Centre.

Recent discoveries by a UK team of astronomers points to the presence of carbon monoxide in Pluto’s atmosphere. Yes, Pluto has an atmosphere; astronomers have known about it since 1988. At first assumed to be about 100km thick, it was later estimated to extend out about 1500km and be composed of methane gas and nitrogen. This gas would expand from the planet’s – er, dwarf planet’s – surface as it came closer to the Sun during the course of its eccentric 248-year orbit and then freeze back onto the surface as it moved further away. The new findings from the University of St Andrews team, made by observations with the James Clerk Maxwell telescope in Hawaii, identify an even thicker atmosphere containing carbon monoxide that extends over 3000 km, reaching nearly halfway to Pluto’s largest moon, Charon.

It’s possible that this carbon monoxide atmosphere may have expanded outwards from Pluto, especially in the years since 1989 when it made the closest approach to the Sun in its orbit. Surface heating (and the term “heating” is used scientifically here…remember, at around -240ºC (-400ºF) Pluto would seem anything but balmy to us!) by the Sun’s radiation would have warmed the surface and expelled these gases outwards. This also coincides with observations made by the Hubble Space Telescope over the course of four years, which revealed varying patterns of dark and light areas on Pluto’s surface – possibly caused by the thawing of frozen areas that shift and reveal lighter surface material below.

“Seeing such an example of extra-terrestrial climate-change is fascinating. This cold simple atmosphere that is strongly driven by the heat from the Sun could give us important clues to how some of the basic physics works, and act as a contrasting test-bed to help us better understand the Earth’s atmosphere.”

–  Dr. Jane Greaves, Team Leader

In fact, carbon monoxide may be the key to why Pluto even still has an atmosphere. Unlike methane, which is a greenhouse gas, carbon monoxide acts as a coolant; it may be keeping Pluto’s fragile atmosphere from heating up too much and escaping into space entirely! Over the decades and centuries that it takes for Pluto to complete a single year, the balance between these two gases must be extremely precise.

Read more about this discovery on the Royal Astronomical Society’s site.

Pluto's elliptical orbit

So here we have Pluto exhibiting an expanding atmosphere of thawing expelled gas as it gets closer to the Sun in an elliptical, eccentric orbit. (Sound familiar?) And now there’s another unusual, un-planet-like feature that’s being put on the table: Pluto may have a tail.

Actually this is an elaboration of the research results coming from the same team at the University of St Andrews. The additional element here is a tiny redshift detected in the carbon monoxide signature, indicating that it is moving away from us in an unusual way. It’s possible that this could be caused by the top layers of Pluto’s atmosphere – where the carbon monoxide resides – being blown back by the solar wind into, literally, a tail.

That sounds an awful lot, to this particular astronomy reporter anyway, like a comet.

Just saying.

Anyway, regardless of what Pluto is or isn’t, will be called or used to be called, there’s no denying that it is a fascinating little world that deserves our attention. (And it will be getting plenty of that come July 2015 when the New Horizons spacecraft swings by for a visit!) I’m sure there’s no one here who would argue that fact.

New Horizons’ upcoming visit will surely answer many questions about Pluto – whatever it is – and most likely raise even more.

 

Artist's impression of Pluto's huge atmosphere of carbon monoxide.Credit:P.A.S. Cruickshank.

The new discovery was presented by team leader Dr. Jane Greaves on Wednesday, April 20 at the National Astronomy Meeting in Wales.

Article reference: arxiv.org/abs/1104.3014: Discovery Of Carbon Monoxide In The Upper Atmosphere Of Pluto

 

*No disrespect to Mr. Brown intended…he was just performing science as he saw fit!

 

 

About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Lawrence B. Crowell April 24, 2011 at 3:20 AM

If we were to be scientifically accurate we would drop the whole concept of planet as it has been used. Planet came from wandering star, which we know they are not. Further, if we are to peel these dwarf planets off, and there are a couple of them about as big as Pluto such as Sedna, based on physical characteristics, then should terrestrial planets be consdiered the same type of object as a gas giant or jovian? The definition appears to hinge upon the idea a planet needs to gravitationally clear its orbital region. This definition is a bit uncertaint to me. We had an article recently about the horseshoe orbiting asteroid. Clearly Earth has not completely cleared its interplanetary space. Jupiter has similar objects called Trojans.

There are three types of objects, terrestrials, jovians and K-dwarfs (Kuiper belt dwarf planets — like Pluto). They all three are physically quite distinct from each other. They have different compositions, mass ranges and so forth. Maybe be we should call these objects cometoids, for comets and these dwarf planets are from the same region, likely have a similar chemistry and so forth.

LC

iantresman April 24, 2011 at 4:54 PM

LC wrote: “Planet came from wandering star, which we know they are not.”

Doesn’t that depend on your frame of reference. See “Wandering Stars: The Movements and Visibility Cycles of the Naked Eye Planets

Lawrence B. Crowell April 24, 2011 at 5:40 PM

I meant the word planet came from greek for wandering star.

LC

Torbjorn Larsson OM April 24, 2011 at 10:48 PM

FWIW, the criteria isn’t “completely cleared” but cleared, i.e. the planet dominates orbital mass. Pluto, Ceres et cetera fails that.

DrNothing April 25, 2011 at 3:50 PM

If Earth were out that far, it too would ail (per modeling) to clear it’s orbit either.**

DrNothing April 25, 2011 at 3:58 PM

LOL! I just read this and realize I seem to have had a case of reportersiezurites… I MEANT to say that if Earth were out that far, it would fail, as modeling suggests, to clear it’s orbit as well.

DrNothing April 25, 2011 at 3:55 PM

Truly this new (and arguably first) non-vague definition of the word clearly needs work, as many involved admit. And you bring up a great point that I hadn’t heard of or considered before per ‘rockies’ being considered in the same class as ‘gassies’ making comparably little sense. I say that we ape the Greeks’ treatment of the word, “Love”. Different words for different types of them, but still use the overlaying term, “Planet” to speak in generalities on the topic.

cosmic avenger April 24, 2011 at 3:41 AM

I’ve been teaching high school science for 15 years, initially I discussed Pluto and its status as a planet as a discussion of definitions and characteristics for similar and dissimilar ideas. I have always had students come up with the idea that Pluto seemed more like a comet than a planet.

VIGNESHRAJU April 24, 2011 at 4:32 AM

It is very useful to us.These discovery would also helps us to contact with extraterrestrial life in our universe.

Nexus April 24, 2011 at 6:13 AM

How?

johnnymorales April 24, 2011 at 6:21 AM

All this interest in Pluto would be better redirected at Triton which research indicates is probably a near twin of Pluto.

If we did so, not only would we learn all we need to know about Plutinos, we’d also learn a lot more about Neptune.

A 2 for 1 that somehow is completely overlooked due to the fascination with Pluto.

Sili April 24, 2011 at 10:34 PM

I think it’s more a matter of a mission to Triton having to be an orbiter. Which is far more expensive than the fly-by of Pluto, something that’s being done on a shoestring budget.

Jon April 25, 2011 at 5:38 PM

I think a Cassini like orbiter around Neptune and Uranus would be awesome in general. Let’s get landers on that thing. =D

Also, don’t planets and well, everything with an atmosphere (even a highly variable one that is seasonal) have tails of some kind? Why isn’t everything a comet?

Feenixx April 24, 2011 at 8:29 AM

Neil deGrasse Tyson has been saying all along that he reckons “Pluto is a comet” – and some people I know say that he is just “being controversial”. It seems that he does have a valid point.

So, what with both, Pluto and Charon, orbiting the centre of their combined gravity, which lies outward from the surface of either of the two: can we call it a “double comet”?

Feenixx April 24, 2011 at 8:31 AM

… or a “binary comet” – as in “binary star system”?

vagueofgodalming April 24, 2011 at 10:16 AM

It strikes me that Jane Greaves isn’t very politically aware, since her quote there plays into both the ‘it’s all natural’ and ‘climate scientists admit they don’t know any basic physics’ memes regarding climate change – nether of which I would think she believes.

David April 24, 2011 at 1:41 PM

With an atmosphere that extensive, maybe Pluto is a small gas giant with a rocky core and transparent atmosphere.

Jorge April 24, 2011 at 1:56 PM

Newsflash: Venus loses low mass gaseous molecules to space due to the effect of the solar wind. That was, in fact, how it lost most of its water. The molecules get blown away as a thin gaseous (you guessed it) tail.

Hey, look, Venus is a comet!

Dumb, huh?

Want to know what’s even dumber? Earth is a comet, for it does the exact same thing. Only our tail is thinner than venus’, because the solar wind here is not as strong and because we’re heavier. But it’s there, so the Earth is a comet. Shabam! Take that, you fools that thought the Earth was a planet! Silly, silly people…

There’s only one planet in the whole Solar System, and that’s Jupiter. The rest? Comets, comet cores, things with tails in general.

Actually, and seriously now, Jupiter itself has a tail, a huge magnetic tail filled with charged matter, measured recently by New Horizons, but I’m not sure if it also includes matter coming from the outer layers of its own atmosphere or not. Probably not: its magnetic field may be too strong for that. But all of the smaller planets lose atmosphere to space. It’s a common process, known for many years, and I find truly silly that the discovery of a similar process ocurring in Pluto would generate articles like this one. Even Mercury, which has almost no atmosphere, loses matter to space. Planets customarily show thin comet-like tails, and they don’t even have to be small. Look at HD 209458 b, aka Osiris, both larger and more massive than Jupiter, with a tail detectable from Earth!

Let’s try not to silly it up whenever the topic is Pluto, OK?

solarx2 April 24, 2011 at 2:28 PM

ok, jorg good points but the planets you speak of are not made of ice and have almost perfectly circular orbits. a comet by definition is made of something that is frozen and has an eccentric orbit that causes it to periodically suffer bouts of intense melt. also, several of the planets you mentioned have strong magnetic fields, which would disqualify them from the comet designation outright. pluto, could technically fit the definition, seems a little far-fetched to me though. we really need a good classification system that everyone agrees on.

Lawrence B. Crowell April 24, 2011 at 3:06 PM

The Earth will lose all its water in 2 billion years or less. In fact with the increased heating of the sun in about 1 to 1.5 billion years Earth will start to look more like Venus. Planets and bodies in general outgas into space.

The Jovian and Saturnian moons, and certainly those of Uranus and Neptune appear to be plutoid-like, and these may in fact be left overs from the early solar system evolution where the Kuiper belt may have extended all the way into the “frost radius.”

LC

Jorge April 24, 2011 at 4:48 PM

Well, FWIW, the more I learn about these things, the more I think the division between comets and non-comets makes no sense at all.

Because a rock is nothing but an ice of silicate gas. If you rise the temperature enough, what you get is silicate gas although, as commonly happens with the more volatile organic molecules, they tend to quickly subdivide in simpler chemical species. But the truth remains that an ice is in its essence a mineral, just like any other. If you lower the temperature enough, almost anything becomes an ice; if you rise it enough, everything turns into gas.

And all bodies are combinations of different substances that evaporate or sublimate at different temperatures. Of course, those that form at lower temperatures and/or are subject to lower temperatures during their existence, will incorporate a larger percentage of substances that turn into gas at lower temperatures than those that don’t. But there is no clear division. Even the smallest comets that drop by and sprout magnificent tails include “rocky materials” (i.e., silicates), and even Mercury has a tiny percentage of what’s commonly called volatiles. It’s all a vast continuum, as has been proven recently by those asteriods showing cometary activity and by the inert comet nuclei that have been discovered. In a very real sense, a comet is just an asteroid that wanders too close to its star. Or a planet. Or an asteroid or planet, confortably sitting in their low-e orbit, subject to the action of a star that expanded a bit too close to them.

Speaking of eccentricity, Pluto’s is only a bit larger than Mercury’s, and there are other dwarf planets with much more circular orbits. And if you go to the Extrasolar Planets Encyclopedia’s interactive catalog and order the whole shebang by eccentricity, you’ll find that about one quarter of all extrasolar planets discovered so far are more eccentric than Pluto. Not much of a divisor there.

laurele April 25, 2011 at 10:17 PM

Many giant exoplanets have orbits far more eccentric than that of Pluto. One has a very comet-like orbit around its star. Yet it makes no sense to classify them as comets. Clearly, planets can have elliptical orbits too. Pluto’s orbit is stable, unlike that of comets, which lose mass every time they come close to the Sun, eventually disintegrating altogether. Pluto never comes into the inner solar system, and it is much bigger than the largest known comets. Also, Pluto is not “made of ice,” as it is 70-75 percent rock and geologically differentiated into core, mantle, and crust just like Earth–and unlike any comet.

Jason Major April 24, 2011 at 4:25 PM

I realize that the “Comet Pluto” idea is a bit imaginative, but obviously whenever classifications are made there’s going to be a hazy zone between them. Perhaps actual planets – dwarf or not – exhibit some comet-like characteristics as well but obviously we’re not going to rethink what to call Earth, Venus, Saturn, et al….at least not anytime soon! Maybe comets would thus also be classified by a smaller, irregular size and shape, whereby Pluto would then be out of that group. But the expanding and receding atmosphere, affected as it is by solar heating and blown into a tail, as well as its origins out near the Kuiper Belt, admittedly does make one wonder what type of sub-categories “dwarf planet” status might require. Still, Mercury behaves nothing like Jupiter or Saturn yet we comfortably call each a planet, so this may end up being more an exercise in semantics than anything else. Regardless, Pluto is fascinating! While we all quibble over what’s-called-what New Horizons is quietly zipping through the blackness of space, preparing for its all-too-brief rendezvous with an enigma. We should save our assumptions until then, when undoubtedly everyone will be greeted with unexpected surprises!

Moonshine April 24, 2011 at 6:43 PM

Thankyou Jason for your input. I agree on this totally !

I hope that in a 100 years if we don’t kill ourself off first, that this same topic will be settled or continue to inspire a more intellegent refinement of the classifcation system.

RUF April 24, 2011 at 9:55 PM

K-dwarfs? Does that mean “Kuiper”? Hadn’t heard that one. I like the Jovian, Terrestial, dwarf scheme.

The exact origin of a word may have a meaning that no longer applies — but it still works. Some still say “dial 911″ though dial phones are gone, and we “tape” shows on a DVR. Just throwing that out there. I like the word planet. Doesn’t really matter what it used to mean.

One last thing — Could all icy moons like Enceladus and Europa be HUGE captured comets? Doesn’t sound to far-fetched to me (except maybe their size).

Jason Major April 24, 2011 at 11:00 PM

How about J-Planet, T-Planet, D-Planet for terms? (Sounds like nicknames from Jersey Shore…)

Torbjorn Larsson OM April 24, 2011 at 11:11 PM

Also possibly excepting their angular momentum. Captures would have roughly equal chances of being retrogrades in orbit (and possibly spin), right?

As opposed to scattered and coalesced impacts as seems predicting our and Mars moons (and even a putative recent moon impact on the later – Mars may have had at least 3 moons at the same time). And whatever process seems to have formed most of the giants moons.

But there _are_ captures too. (Say, Triton.)

So how did the giant’s moons form? Can it be used to tell between non-retrograded captures and the rest?

Anyway, IIRC composition is gradual over the planetary system (due to where ices froze out). Maybe that can be used.

Torbjorn Larsson OM April 24, 2011 at 11:13 PM

I like the word planet.

It has a certain gravitas.

[/ducks out before IVAN3MAN starts to throw planets and other pun stuff on me.]

Torbjorn Larsson OM April 24, 2011 at 11:00 PM

I was going to say something along the lines of Jorge and Jason, there is a continuum with clutter. Especially the tail characteristic in itself strikes me as silly. Mercury’s tail is 6-16 planet radii IIRC.

It is together that these things (solar heated CO atmosphere, tail; like many comets) makes a tentative impression.

Also, it does shore up support for the value of the planet criteria which is (more or less) based on orbital properties alone, regardless of the individual pathway and (most of) the internal physical characteristics of the population.

Nyx April 25, 2011 at 5:21 AM

More hints we get, more Pluto become fascinating. In 2015 Pluto will be 26 years after its perihelion (Sept. 1989, Wikipedia). The next one will be in 2237. While 2015 it’s not very late, I feel like we missed some opportunities and maybe discoveries. I still remember astronomers urging a mission, in the previous decades. But I’m happy and curious about New Horizons. I can’t wait to see what New Horizons will find there.

Andrew James April 25, 2011 at 6:45 AM

Your name is closely associated with Pluto, so I’d expect you should know all about this (or at least you muse would!).

the_alien_in_me April 25, 2011 at 10:13 AM

Ah, humans, silly as ever… of course there is a continuum in nature, be it in shapes or sizes, colours or compositions. we just can’t seem to live without putting everything into little boxes, each one with a very distinct name. ok, i won’t dispute the usefulness of such a scheme in many instances, but we should be aware that in many other occasions it just doesn’t reflect the strangeness of things in the real universe…
as for the word planet, we should keep in mind that earth also was not considered a planet, until copernicus. so, if pluto was “demoted”, can we say the earth was “promoted”? probably not, i mean, once the centre of the universe… there’s only one way, and it’s down in the scale of importance…. ;-)

Torbjorn Larsson OM April 25, 2011 at 2:57 PM

As long as we are philosophizing, well, yes, but the other side of the coin is that both graduations and classifications are useful as you note.

Also I like to ponder how we can use or impose non-linearities to make qualitative as opposed to quantitative distinctions.

For example, transistors are continuous analog devices, yet by design we can make them operate as digital devices in the discrete regime. (Maybe a bad example since the device non-linearity isn’t strictly necessary for the circuit non-linearity.) Never underestimate the power of a little bit.

Dark Gnat April 25, 2011 at 2:57 PM

The idea of classifying planets and other bodies into two or three catagories is rather silly.

Maybe we should extend the OBAFGKMLT should extend down to planets. It’s partly there, as L and T represent brown dwarfs.

Base them on mass, size and composition. Allow for a seperate catagory for rogue/ejected bodies.

Andrew James April 25, 2011 at 3:54 PM

Stars emit radiation from their surfaces or atmospheres, planets absorb more radiation than they receive emit radiation.

You also missed some of the classes. I.e. Y (<600K) [None observed so far, though exoplanet Wasp 12b could be one!] Also below M are the 'C' and 'S' classes, and above O is the W class or Wolf Rayets (as either WC or WN subclasses) P and Q are planetary nebulae and Q for novae.

If you wished to add a letter for planets, sadly all twenty-six are assigned to some spectral aspect or another I.e. E= emission lines, H=Non-polarised magnetic white dwarf, V=variable, X, Y and Z are stellar metallicities, and R to Z can be confused for variable stars.

Perhaps we can use the "Star Trek" classification of planets. I.e Memory Alpha's http://memory-alpha.org/wiki/Planetary_classification (The earth, for instance, is a M type planet!)

Andrew James April 25, 2011 at 3:58 PM

Err…. Easteritis:
Correction: “Stars emit more radiation from their surfaces or atmospheres than they receive, planets absorb more radiation from their surfaces or atmospheres than they emit.”
Now I feel better…

Jorge April 25, 2011 at 4:22 PM

Well, I don’t think it’s all that silly. In biology, earlier taxonomy (before all the genetic stuff was discovered) was based on dichotomical keys. With the vast difference that biology is inherently a historical process, wereas astronomy is much more phisics-driven (i.e., in biology what the ancestors of a given living species are play a fundamental role in determining what that species is, wereas in astronomy what a given body is, wilst also influenced by its history, is much more influenced by the phisical constraints on what it can be, given its mass and proximity to other masses and energy sources), that idea of dichotomical keys can also be used as a starting point for astronomical classification. You just have to find the criteria that minimize the inevitable grey areas.

For instance: upwards to a certain mass range, all objects will undergo fusion of deuterium in their cores; downwards they won’t; upwards we have brown dwarfs (which I much rather call “planetars” as in “intermediate objects between planets and stars”, because they are neither brown nor particularly dwarfish), downwards we have planets.

Upwards of a certain mass range, all objects will round up due to their own gravity, reaching states close to hidrostatic equilibrium; downwards, they won’t and their shape will be determined by chemical bounds, not gravity; upwards we have planets, downwards we have minor objects.

(note that these two complementary dichotomies are based on the same thing: mass. As all complementary dichotomies should be.)

And so on. We can and should use the same dichotomical approach when subcategorizing, sub-subcategorizing, etc. If we choose the basic criteria well, we can go as deep as we’d like without having to touch the upper levels. We can dichotomize the planets by the presence or absence of a superficial discontinuity, thus separating gas giants from the rest; we can dichotomize the planets by how dominant they are in their local orbital neighborhoods, thus separating belt planets from main planets; we can dichotomize those that have a superficial discontinuity by it being a liquid or a solid interface; we can dichotomize those that have a solid interface by it being made of silicates or what is commonly referred to as ices, and so on, and so forth.

Torbjorn Larsson OM April 29, 2011 at 11:20 AM

Love that comment! It’s taking something that I’ve been grasping for and really sifted out the good stuff.

And in a comprehensible way too. [Thats is right, I didn't love it _just_ because it fit my own preconceptions; or in this case, perhaps "postconceptions".]

Dark Gnat April 25, 2011 at 2:58 PM

Sorry for the typo.

Aqua April 25, 2011 at 5:52 PM

Now THAT would be a BIG comet! Is there a size limit for the largest comet possible?

Sowff April 25, 2011 at 7:08 PM

Pluto is a planet and Charon is one of its three moons. If someone also wants to call Charon a binary and secondary planet, that is fine, but it is still also a moon of Pluto. Mercury also has a tail. No comet has an atmosphere and 3 moons orbiting it, or even two moons and a binary object orbiting it. The whole comet talk thing is silly.

laurele April 25, 2011 at 10:10 PM

Having a tail is not “un-planet-like.” It turns out many planets have tails; that does not make them comets. Mercury has a long, yellow-orange tail of glowing gas, as described here: http://www.astroearth.net/planet-mercurys-tail/ . Many hot Jupiter exoplanets in close orbits around their parent stars also have tails due to outgassing. Dwarf planets are planets too; the term was created not by Mike Brown but by Dr. Alan Stern back in 1991 to indicate a third class of planets in addition to terrestrials and jovians–small planets that are large enough to be in hydrostatic equilibrium (rounded by their own gravity) but not large enough to gravitationally dominate their orbits. Stern never meant for dwarf planets to not be considered planets at all. Pluto has far more in common with the planets than with comets. Unlike comets, it is rounded by its own gravity; it has geology and weather, and it is differentiated into core, mantle and crust just like the Earth is. Comets have none of these features. And while comets are mostly ice, Pluto is estimated to be 70-75 percent rock. Brown did not “kill” Pluto; the IAU vote was done by only four percent of its members, most of whom are not planetary scientists, and it was opposed in a formal petition by hundreds of professional astronomers. Here is a link to my blog presenting the other side of this debate: http://laurelsplutoblog.blogspot.com

Jason Major April 27, 2011 at 4:50 AM

Laurel: really the main idea here is that we SHOULD question classifications, if only to open our eyes to the diversity of worlds out there. If our own little solar system can have so many grey zones, imagine what we will encounter as we explore other alien systems? Our learning begins here but it certainly won’t end here.

If a world like Mercury, so terribly near the Sun and receiving the force of the solar wind as it does, has a constant tail of plasma as it is now known to exhibit, is this the same as a comet’s tail of ejected gases and ice? It seems to be a different *sort* of tail, what’s seen on Mercury, but what’s suspected on Pluto is more akin to the sort comets have.

I’m not advocating another change in Pluto’s classification, or supporting the 2006 decision…I’m mainly saying that things don’t always fall into neat categories just because we say they are so. Why CAN’T Pluto be a giant comet? A “supercomet”, perhaps? With all we have yet to discover in our own galaxy, we can’t hold TOO dearly onto terms or we’ll miss the real show.

laurele April 29, 2011 at 5:09 AM

Questioning classifications is always a good thing. I have a problem with people who say, “the IAU has spoken” and therefore, the issue has been decided for good. When people question (regardless of which position they’re questioning), they are thinking for themselves instead of just repeating the words of someone else. Unfortunately, American education does not focus enough on teaching how to think.

Based on what is now known about Pluto, I see it as far more akin to the planets than to comets. Others can and do disagree. Maybe we will end up with an intermediate category or several intermediate categories. Earth also has a tail, so clearly there are many different kinds of tails. How can we classify some of these large exoplanets with tails when we cannot even view them directly?

I like the idea of the Star Trek planet classification system exactly because it allows for such incredible diversity. We are nowhere near having discovered all the strangeness and weird objects in our galaxy. Any classification system should assume there is much more out there that we have yet to learn.

Torbjorn Larsson OM April 29, 2011 at 11:33 AM

I have a problem with people who say, “the IAU has spoken” and therefore, the issue has been decided for good.

But we can turn that around. In biology, it _is_ the formal organizations that set classifications and wrangle out the rules, because the binary names will have to last for a long while. This pertain to “planets” too, because it was a coherent classification for a long time until observation made it unsustainable.

Also, IAU are organizationally democratic, meritocratic, or whatever. The point is that they worked up to this for a long time and then decided by their own rules. It is simply silly to say that 4 % of its members voted, since the organization is behind it. What are we supposed to do with that except, I’m sorry to say, laugh at the argument?

Dissatisfaction can change a decision. If there was a petition and it was rejected, it supports all of the above. (An organized system, a decision along the rules, a robust decision that withstood criticism.)

weeasle April 26, 2011 at 10:39 AM

Classification is important in science. Great thinkers like Einstein admitted that they were searching for an elegant way to classify the phenonena and objects in the universe. However, existence and the universe doesnt always play along with human ideals of order and rationality. To the dismay of Einstein and other great thinkers it would seem our Universe is an immense Dynamic Temporary (Temporal) system. Sometimes i believe the best we can do in science is to recognize the shades of grey rather than aim for black and white classifications.. i like the word planet too.. but i am willing to adapt it if necessary much the way we adapt words in language to describe similar but different things..

Sowff April 29, 2011 at 8:10 PM

Stripping Pluto of planethood, and especially in the highly political and biased way it was done by the IAU in Prague in 2006, is the single worst blow to science in the past 500 years. Pluto must, and will, be replanetized. Until then all reasonable people who love science and learn about the travesty that befell Pluto must fight with every ounce of intellectual energy to see that Pluto regain its proper stature in our wonderful Solar System. Why would a child chose to go into science when they learn the fate of Clyde Tombaugh’s beloved discovery? They will rightly think that once they are dead a pack of jackals will take away their accomplishments, as well. The case for Pluto’s planethood is clear and convincing. No one in their right mind can listen to the case for Pluto and think anything but that Pluto was given the shaft by a pack of jackals. The lady running the IAU session in 2006 that deplanetized Pluto, was cutting off pro-Pluto speakers and seemed to be mentally disturbed. If you ever see the video of the session, you will be outraged at her rude and clearly biased behavior. The IAU Executive Committee had it in for Pluto in 2006,and abused its power to stab Clyde Tombaugh in the back. In 2015, when the IAU meets in Honolulu for a General Assembly a month after New Horizons flies past Pluto, I hope things will be corrected. I hope to be there to protest and urge the members to vote their conscience and not succumb to threats. I know of one IAU member who was in Prague who voted against Pluto as a result of a threat to his career. This needs to be corrected.

Torbjorn Larsson OM April 29, 2011 at 9:36 PM

Hyperbole much? Naming things is a non-issue for actual science, though robust and widespread terminology is a boon.

That is why we shouldn’t revoke anything soon, even if it should turn out to be an unlucky choice. And that isn’t clear, on the contrary the new terminology suits the modern situation better.

There are worse offenders, like “law” and “theory”. Nobody seems to go after those though, and for good reason.

Jason Major May 1, 2011 at 11:12 PM

A bit excessive, although many agree on your basic standpoint. But science does have to remain flexible as new things are discovered…or else the Copernican Revolution may never have taken hold!

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