Pluto is a weird place. On average, it’s about 6 billion kilometers from the Sun, so it’s very, very cold there. It’s amazing it has an atmosphere at all… but even that is weird. Pluto’s orbit is an ellipse, and right now — even though it’s slowly pulling away from the Sun — it’s still near the point in its orbit when it’s closest to the Sun. The ever-so-slight increase in heat has warmed the solid surface, turning it into gas, pumping up Pluto’s thin air.
And now astronomers have been able to measure that atmosphere with uncanny accuracy, all the way down to the surface.
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| Artist impression of the surface of Pluto. Credit: ESO/L. Calçada |
Using the ESO’s Very Large Telescope together with a spectrometer that has extraordinary resolution — the ability to distinguish very small differences in the wavelength, or "color", of infrared light — they’ve been able to make a map of the whole atmosphere from the surface of Pluto all the way up to the top. What they’ve found in general is interesting: the atmosphere is about -170 Celsius, or 50 degrees warmer than the surface! That’s not exactly warm, of course; it’s just barely above the condensation temperature of nitrogen.
What’s really odd, though, is that the atmospheric temperature goes up with height, which is more or less the opposite of the Earth, where the temperature (in the lower atmosphere) decreases with increasing height.
In a sense, Pluto’s atmosphere is upside down. This temperature inversion is due to a process like sweating: as sweat evaporates, it cools our skin. On Pluto, the frozen gas sublimates (turns directly to gas) when warmed, removing heat from the surface. So the surface cools, and the atmosphere warms.
And there’s more: they found that by number, about 0.5% of the atmosphere is methane, a number which was previously not known. In other words, there is one methane molecule for every 199 nitrogen molecules.
This is a pretty astonishing measurement to make. Pluto is a long way off, and its atmosphere is about 1/100,000th as thick as Earth’s; it’s almost, but not quite, a vacuum. Yet there’s enough there, with the right constituents, to profoundly affect how the object behaves.
To be able to make confident measurements of such a thin soup from so far away is another testament to how advanced our science really is. Because we’re curious apes, we have reached out to an iceball 40 times farther from the Sun than we are and taken its measure.
And we’re doing even more. In 2015, the New Horizons probe will fly past Pluto and its small cadre of moons, taking close up pictures and sampling its environment. These new observations using the VLT will help scientists prepare even better for the fleeting encounter, so that we can maximize the brief time the spacecraft will be near this signpost of the outer solar system.
It’s truly incredible to think of what we can do, simply because we’re curious.
March 2nd, 2009 at 5:11 pm
Great, more ammo to the global warming denyers. “See, pluto is heating up too… It’s the same as with the Earth.” You’d think no one has ever heard of the inverse square, not to mention the elliptical orbit.
The fact that they actually MADE these measurements is pretty fantastic! Not bad for hailess apes (some more hairless than others…) who’ve only been building things for a geologic eyeblink!
March 2nd, 2009 at 5:17 pm
On Pluto, the frozen gas sublimates (turns directly to gas) when warmed, removing heat from the surface. So the surface cools, and the atmosphere warms.
I’m always reluctant to argue with scientists who are doing their work – I’m sure this does reflect their modelling. But as an explanation to the rest of us, it falls short. This process is exactly what happens on Earth: water evaporates (and in the Arctic, ice sublimes) and absorbs heat which is released when it condenses higher up. Yet we don’t usually have an inversion. There’s a missing piece to the puzzle, I’m sure, but it ain’t in the press releases.
March 2nd, 2009 at 5:17 pm
Dr. Phil Plait: “Pluto is a long way off, and it’s atmosphere is…”
Err… that should be its, not it’s.
BTW, great article, Phil.
March 2nd, 2009 at 5:26 pm
What might be the source of Pluto’s methane? (and no jokes about what the Disney dog had for dinner!) I presume we can rule out life, right?
March 2nd, 2009 at 5:39 pm
Vauge — well, the analogy breaks down in that Earth’s atmosphere isn’t composed primarily of water vapor.
March 2nd, 2009 at 5:41 pm
The New Horizons probe will give us a good look at the surface!
March 2nd, 2009 at 5:43 pm
It’s pretty exciting that we can already detect so little methane from so far away, given how we’ll want to be looking for methane on exoplanets as a bio-signature.
On the other hand, what does the presence of methane on Pluto say about the reliability of methane as a bio-signature?
March 2nd, 2009 at 5:46 pm
I am the planet eremite,
The gaunt repulsor of the light
That falls like icy rain at night.
From frigid stars and moons a-cold.
Ye have not seen a world like this -
The blank and oceanless abyss,
The nameless pit and precipice,
The mountain very bleak and old.
Yet ah – my silence murmereth!
Oh inner orbs, ye have not heard
That stillness where there is no death
Because no life hath ever stirred!
“But here God’s very name is dead!”
Wept Heaven’s mighty myriarch,
Then trembling, turned away and fled
For something gibbered in the dark!
Stanley G. Weinbaum 1937
(Unnamed poem from his book “The New Adam”, and actually written about Neptune, but I think it perfectly describes Pluto)
March 2nd, 2009 at 5:52 pm
Pluto is just a big comet isn’t it? If it was just a little closer it would have a wicked coma.
March 2nd, 2009 at 5:58 pm
Vagueofgodalming said,
Good point. Planetary Science is not my specialty.
However, my first reaction is that since Earth has that molten core thing going on, there’s a lot more heat generated from the inside that doesn’t get added into Pluto’s equation. Not to mention the proximity to the sun, the size of the earth, the density of the atmosphere, liquid water, etc.
Again, I’m not an expert.
March 2nd, 2009 at 6:00 pm
@J.D. Mack
The methane is probably from Uranus.
March 2nd, 2009 at 6:01 pm
Err. there was supposed to be a fake HTML tag on that. I’ll make it a fake BB Code tag, instead.
[/middle school humor]
March 2nd, 2009 at 6:02 pm
@ IVAN3MAN, is this your homepage: http://www.charman.co.nz/essays/grammar2.htm
March 2nd, 2009 at 6:04 pm
@ J.D. Mack
Yes, we can rule out the possiblity if life on Pluto!
March 2nd, 2009 at 6:05 pm
Nuts. Missed an “it’s”. And I went through it, too! Funny how my fingers type stuff without my thinking, and that makes it easier to make that mistake. I know the difference, and also there, they’re, and their, but they still creep in. Its creepy they’re sometimes.
March 2nd, 2009 at 6:06 pm
Correction!
‘Yes, we can rule out the possibility of life on Pluto!’
March 2nd, 2009 at 6:13 pm
I love that illustration. It’s art like that that got me into astronomy in the first place. To think that in my lifetime I might be able to see such scenes for real, albeit transmitted electronically, is amazing….but also a little depressing. What might we be able to do if we could stop wasting so much wealth figuring out how to slaughter each other? Can you hear a sigh on Pluto?
March 2nd, 2009 at 6:14 pm
That’s pretty freakin’ cool. I like the artist’s interpretation, but have to think that it would actually be a lot darker there, what with being so far from the sun and all.
March 2nd, 2009 at 6:16 pm
@uknesvuinng
HAHAHAHAHA!!! I just love middle school humor. That struck me as particularly funny after a long day staring at computer screens…
March 2nd, 2009 at 6:27 pm
Eclogite, apparently (I googled it) the sun is still bright enough to light up Pluto as depicted in the picture above.
March 2nd, 2009 at 6:40 pm
@Vagueofgodalming – Earth atmosphere cools down with the altitude because of the adiabatic effect (basicaly, air expands as it rises and this expansion is the work done at the expense of its energy i.e. temperature). I guess this mecahnizm does not work in Pluto’s thin atmosphere.
Anyway, it would be interesting to see explanation from those who know this stuff.
March 2nd, 2009 at 6:40 pm
Does “170 Celsius” mean “170 Kelvin”?
March 2nd, 2009 at 6:46 pm
Great catch, Bruce. No, it doesn’t. 170 Celsius or 170C is a temperature that is 70 degrees above the boiling point of water (100C). This article should have said 170 Kelvin, which is indeed very, very cold.
March 2nd, 2009 at 6:51 pm
Rimantas is correct. Because the atmosphere is sooooo thin, the expansion (and thus adiabatic cooling) with height is apparently negligible compared to the other heat transfer mechanisms.
March 2nd, 2009 at 6:55 pm
@Bruce: That’s a “-170 Celsius”. I’m thinking it’s not negative degrees kelvin.
March 2nd, 2009 at 7:00 pm
I’d love to have that artist’s ‘impression’ on my wall, but the picture is otherwise WRONG WRONG WRONG! Does Pluto really have a spherical moon? (Any bets on when a TV show creates a ‘moon’ that looks like Mr. Potatohead rather than a marble?) With the Plutonian atmosphere being as it is, why is the sky not black? Looking at the horizon, the brilliant white scattering suggests a high concentration of aerosols and yet at the location of the view there is much less scattering. The viewer is either on the planet or somewhere within its atmosphere because the sun has an aureole. The planet also seems to have a very high albedo (at least in the visible region), so why can’t we see the ‘dark’ side of the moon?
March 2nd, 2009 at 7:18 pm
@MadScientist – did I miss any news about Charon being non-spherical?
Also, I’d say that the nature of reflection on the rock (direct reflection, not diffuse) suggests that is in fact very dark
March 2nd, 2009 at 7:34 pm
I’m astounded that they can make such measurements (yes, I know how, but even when you do, it still boggles the mind!)
March 2nd, 2009 at 7:38 pm
Pluto is different from Earth in lacking oceans, which are the earth’s great heat reservoir, and it doesn’t have the heat absorbing surfaces that make the earth’s surface warmer than its atmosphere. Also, given Pluto’s very thin atmosphere, adiabatic expansion and cooling are probably a lot less important than on earth. Solar heating, convection and adiabatic cooling are why earth’s surface is warmer than the atmosphere. It’s why the troposphere is “tropo” (Greek for “turning”). We have a layer in our atmosphere much like Pluto. It’s called the stratosphere, because it is stratified by temperature. It’s not affected much by surface heating and so thin that adiabatic cooling doesn’t matter much. So I don’t find this discovery all that revolutionary.
March 2nd, 2009 at 7:39 pm
“Pluto’s orbit is an ellipse… ”
more elliptical than the earth’s I gather.
March 2nd, 2009 at 8:15 pm
Phil Plait:
I know what you mean, Phil. As a former proofreader, I can tell you that is the most common mistake that people make.
March 2nd, 2009 at 8:21 pm
It took me a while to notice the negative sign for the temperature is on the line above. I was thinking that if Phil thought 170C is cold I am not going on vacation with him!
March 2nd, 2009 at 8:50 pm
@Nemo,
Well, I don’t think Pluto’s atmosphere would by composed primarily of water vapour either.
March 2nd, 2009 at 8:51 pm
Drat , you’ve discovered our methane but at least (phew!) not the plutonium signature in our atmospheric composition. Firtunately its density keeps the Pl nicely below the surface with us!
Yeah our world is kinda “inside out” compared with yours but, thankyou very much its still a planet! As for “no Plutonean life” – hah! If only you knew …
Then again, probably best not, you’d just come here & invade us.
Incidentally, Charon is definitely round in our dark skies though Hydra and Nix not so much. Plus, We’re far larger than any comet and dwraf planets are every bit as much planets as dwarf stars are still stars thankyou very much!
Oh & Elwood Herring great poem – Thanks!
March 2nd, 2009 at 9:01 pm
Thank you for this! My daughter is doing a report on Pluto and this will be a great addition! Lest I forget to mention, this is really cool.
I just found this blog. It’s wonderful.
March 2nd, 2009 at 9:01 pm
@ M : (March 2nd, 2009 at 8:21 pm)
.. I was thinking that if Phil thought 170C is cold I am not going on vacation with him!
Depends what the temp is measured *in* – degrees kelvin 170 is around minus 100 degrees celscius at least!
As for fahrenheit, forget it! (Wish the USA would join the rest of the world and adopt celcius and metric, it’d make life much easier for everyone.)
Incidentally, surely being able to retain an appreciable atmosphere like this is further evidence showing that Pluto clearly *is* a planet despite the IAU’s dumb, dubious & disreputable decision otherwise.
BTW. : Is Pluto’s atmosphere bigger, smaller or about the same as Mercury’s anyone know?
March 2nd, 2009 at 9:16 pm
Oh & if folks are going to argue that Pluto would lose its atmosphere if it was as closer to the Sun then please remember that many Hot Jupiter planets such as “Osiris” (HD something or other b, an early transiting exoplanet) are also losomng their atmospheres currently too. In fact, evenVenus, I understand is losing some of itstatmosphere constantly intospace at present.
Pluto is a relatively large body esp. compared with asteroids and comets, its gravitationally rounded, it orbits the Sun directly, it has three moons one very sizeable and itself garvitationally rounded. It has its own complex geography and meteorology. Its got its own atmosphere.
Come on folks, Pluto is obviously a planet & the IAU plain got it wrong in Prague two years ago lead by a faction that hate Pluto for dubious, illogical, and politically rather than scientifically based reasons of their own.
I consider the IAU’s anti-Pluto definition to be utterly wrong, to be very bad for astronomy and think it even brings astronomers into disrepute among the wider community. The sooner they reverse their ridiculous decision and accept Pluto as a full planet the better.
March 2nd, 2009 at 9:25 pm
StevoR, I wholeheartedly second everything you’ve said. It’s obvious that the IAU got this wrong from the continued debate and ongoing efforts by both scientists and lay people to overturn the demotion. If they just reversed the part about dwarf planets not being planets, much of the problem would be solved.
As we get new information, it becomes clear that this entire planet definition debate was premature. We’ve found an exoplanet bigger than Jupiter with a comet-like orbit. We’ve found a set of exoplanets, again both gas giants, that orbit in a 3:2 resonance. The variety in these findings is only likely to become more extreme.
There has been speculation that Pluto may harbor a subsurface ocean, which could potentially host microbial life.
March 2nd, 2009 at 9:26 pm
[quote]And now astronomers have been able to measure that atmosphere with uncanny accuracy, all the way down to the surface.[/quote]
Uncanny accuracy? How could you know how accurate their measurements are?
I suspect that “accuracy” is not the right word for what you were trying to express.
March 2nd, 2009 at 9:32 pm
Correction :
Oh & if folks are going to argue that Pluto would lose its atmosphere if it was as closer to the Sun then please remember that many Hot Jupiter planets such as “Osiris” (HD something or other b, an early transiting exoplanet) are also losing their atmospheres currently too. In fact, even Venus, I understand, is losing some of its atmosphere constantly into space at present. That doesn’t stop the Hot Jupiters or Venus from being regarded as planets so it shouldn’t stop Pluto being regarded as one either.
Plus, of course Pluto’s atmosphere is NOT actually lost into space like a comets but returns to the surface as snow instead.
Pluto is a relatively large body esp. compared with asteroids and comets, Pluto is gravitationally rounded, geologically differentiated, orbits the Sun directly, has three moons one (Charon) very sizeable and itself gravitationally rounded. Pluto, our solar systems ninth planet counting outwards, has its own complex atmosphere, geography and meteorology.
Come on folks, Pluto is obviously a planet & the IAU plain got it wrong! Sooner they recognise and correct this the better.
—–
Arrrgh typos! Oh, Bad Astronomer, please, when, oh when are we going to get the ability to edit here???
Just think you can correct your “its” errors and everyone else can correct their typos and not have to keep correcting in extra posts like this one and, crikey, by Jove it’ll make life so much easier and less frustrating if we could just edit – or even at very least preview – these comments.
You wrote something ages ago about an editing ability coming here – when is it arriving? Please!
March 2nd, 2009 at 9:54 pm
@ Laurel Kornfeld saying :
StevoR, I wholeheartedly second everything you’ve said.
Thanks – much appreciated.
The IAU just need to drop the nonsensical, overly complicating, unnecessary, anti-Plutonean third criterion about “clearing orbits” – which given sun-grazing comets and asteroids NO planet technically meets anyway! That last condition for planethood & the division into “classical” and “dwarf” just doesn’t make sense.
I’d recomend they go with the first inclusive definition that was raised -an object that is :
1. non-nuclear-fusing,
2. gravitationally rounded,
3. orbiting the Sun & not another planet = a planet
Then go into the planetary categories of gas giants like Jupiter, rocky planets like Earth and icy planets like Pluto.
Now what’s wrong with that idea? Why isn’t soemthing like that idea officially adopted? Are there any IAU fans or people here to tell us that?
March 2nd, 2009 at 11:25 pm
I think the big problem Sevor is that a definition like that would add a ton of rocks to the planet list that probably don’t deserve to be planets. But i don’t care either way.
March 2nd, 2009 at 11:27 pm
I’d say that anyone who instantly dismisses the idea of life on Pluto is jumping the gun a bit. Pluto is, after all, closely gravitationally tied to a large moon; could that not be heating the interior, just like Jupiter does to its Galilean moons? Pluto could have an internal ocean that goes all the way down to the core, which would be an extremely interesting setting for life…
The methane, however, is likely to be there because the processes that would have destroyed it on warmer bodies do not work quickly enough in the Plutonian cold, and this methane is left over from when Pluto formed!
March 2nd, 2009 at 11:30 pm
[...] Blogs / Bad Astronomy « Pluto’s atmosphere is upside-down! [...]
March 3rd, 2009 at 12:22 am
Please don’t say 199 when you mean “about 200″ it gives a false impression about about precision.
Great article.
March 3rd, 2009 at 1:13 am
OG Says: “I’m astounded that they can make such measurements (yes, I know how, but even when you do, it still boggles the mind!)”
After working in the semiconductor equipment industry for a while I developed a phrase to describe it: “The more I learn about how chips are made, the more I’m convinced it can’t be done.”
In design review meetings I’d ask others at the table, “which of you are the aliens giving us this technology?” Some of them got it, some (mostly the foreign engineers) didn’t, but some just stared at the ceiling and tried to change the subject.
- Jack
March 3rd, 2009 at 1:42 am
Thanks for the responses, everyone. I see Emily L has linked to the actual paper so I’ll try to wrap my brain around that.
March 3rd, 2009 at 4:04 am
@SLC Are you out there mate? Not sure if you’ve seen already but ages ago I answered your question there about the difference between giants and supergiants on the “Wonder Twins telescope sees star’s dying gasps” thread (about the red giant T Leporis) in case your still interested.
Click on my name & scroll down to go see my lengthy answer and a summary in a nutshell on that question – plus a correction too; Arcturus radius = only 1/4 the way to Mercury’s orbit.
—
PS. Hope this doesn’t breach netiquette too badly, my apologies if so, however I’m keen to see if SLC has actually seen my answer to his question there. If anyone out there knows SLC and can let that individual know that’d be appreciated too.
March 3rd, 2009 at 5:16 am
Nice post, Phil! That “iceball” you refer to is 70% rock, with an ice shell– that’s something we discovered in the late 1980s. So fact is it’s a rocky planet–despite misimpressions to the contrary.
Alan
March 3rd, 2009 at 5:41 am
IMO, the IAU’s new definition of planets is right, except for being badly worded. I think the “cleared out its orbit” criterion should be changed to “gravitationally dominates its orbit and vicinity”. All the planets out to Neptune clearly meet this criterion – as the Moon is gravitationally bound to Earth, the Trojan asteroids are held in their orbits by the interaction of Jupiter’s gravity and that of the Sun, etc. – while Pluto, Eris and Ceres clearly don’t.
Charon most certainly IS spherical; its diameter is about half that of Pluto itself, which makes it easily big enough to be in hydrostatic equilibrium. But in a sense, it may not be strictly correct to refer to it as Pluto’s “moon” at all!
Before Pluto’s “demotion”, it and Charon were often referred to as a “binary planet”, rather than a planet and its satellite. Now, presumably, they are a “binary dwarf planet”! There is a specific, and scientifically sound, reason for this distinction. For every other combination of planet and satellite in the Solar System, the barycentre – the common centre of mass, around which both bodies revolve, is located inside the body of the parent planet. ( Yes, this does apply to the Earth and Moon; the Earth has 81 times the mass of the Moon, and their separation is only 60 Earth radii. ) But in the case of Pluto and Charon, the barycentre is located in free space between them.
March 3rd, 2009 at 7:09 am
Will the New Horizons probe literally be sampling Pluto’s environment in a chemical science?
March 3rd, 2009 at 7:16 am
2015 will be a good year for space news! That’s also the year that Dawn reaches Ceres. So we’re in for a twofer as far as Dwarf Planet knowledge goes! Weeeeeee!
March 3rd, 2009 at 7:24 am
I can’t believe someone would cite “ongoing efforts by … lay people to overturn the demotion.” Whatever positions scientists may take on the issue, these efforts by lay people are driven by nothing but ignorance, an undue reverence for the past, and an excess of binary thinking. They’re little different from creationism.
Pluto is what it is. The designation “planet” is arbitrary. You can easily draw up a set of criteria that includes Pluto, or one that excludes it. What’s harder to justify is a set that includes Pluto, the other eight “traditional” planets, and no others. But you know what? It doesn’t matter one damn bit. It doesn’t change the nature of the place, either way. All it does, is affect whether or not Pluto is on the list of “planets” to be memorized by schoolchildren — which is all this issue is, to those objecting lay people. They reduce astronomy to a list of names.
Me, I think their education should run a little deeper than that, and they should learn about as many of the major bodies of the Solar System, in as much detail, as is practical — certainly more than nine, and more than just their names. Then the designation of a particular body as a “planet”, or not, would be seen as the non-issue it really is.
March 3rd, 2009 at 8:22 am
I’ll pitch in with the naturalness, and I presume usefulness, of the new population based definition for planets. For example biology dropped the original naive trait based definitions, for god reasons:
- “It’s a fish, it has fins!”
- “But what about whales?”
Pluto is, quite obviously I think, a Kuiperian fish among others, flitting beside the planetary whale herd. (But I’m no astronomer.)
That was where my thoughts immediately went too. So I don’t see the upside-down analogy; to me it seems more of missing a (dense) layer.
March 3rd, 2009 at 9:14 am
@Greg in Austin
Earth’s core isn’t really a player, here. The heat loss through the surface of the Earth is around 0.01 W/m^2, as I recall. The solar insolation is around 1360 W/m^2. (At a normal incidence, anyway.) It’s easy to see which heat-source should dominate the atmospheric dynamics.
On the other hand, is this really that surprising? Earth’s atmosphere increases in temperature with altitude in regions. So, as I recall, do other planets’ atmospheres. In fact, Pluto’s atmosphere has got to be almost entirely thermosphere/exosphere (I should think), so this is what you’d expect, no?
March 3rd, 2009 at 10:36 am
@Nemo: I am one of the lay people leading efforts to overturn the demotion of Pluto, so let me clarify some misconceptions here. I and the people I know working on this are not driven by “ignorance, undue reverence for the past, and an excess of binary thinking.” Many of us have taken part in informative conferences with scientists, such as the Great Planet Debate at the Johns Hopkins University Applied Physics Lab in Laurel, MD last August. We have taken the time to study the issue and are working in tandem with professional astronomers and with well-educated amateur astronomers to present a case not only to undo Pluto’s demotion, but to undo the entire IAU planet definition, which is poorly written and can easily be determined to make no sense by anyone taking the time to educate themselves on this issue.
Speaking for myself and the other lay people working on this, I can say that we are not working for the adoption of a planet definition that just includes the eight classical planets plus Pluto. Instead, we seek a broad planet definition based on the central criterion of hydrostatic equilibrium as the primary differentiator between planets and non-planets. The difference among the many objects that meet this criterion, including the fact that some do not gravitationally dominate their orbits, can be noted through the use of subcategories. Again, I say, there is no problem with using the term “dwarf planets” for these smaller bodies if we undo the IAU’s ridiculous statement that dwarf planets are not planets at all.
I do not reduce astronomy to memorizing a list of names; in fact, I have stated repeatedly that memorization is of little value. It is more important for children (and adults) to understand the different types of planets and their central characteristics. And I agree that they should learn about as many objects in the solar system as possible in as much detail as possible. It’s the people who worry about memorization who have a problem with too many objects being classified as planets, with the argument that a large number is too hard to memorize.
At the same time, words matter, and I disagree that the designation–or not–of an object as a planet matters. It does matter, in terms of distinguishing clearly between two very different categories of objects–those large enough to be pulled into a round shape by their own gravity and those not large enough and therefore shaped by chemical bonds. However, that doesn’t mean the latter category shouldn’t be taught in schools; they most certainly are worth studying.
March 3rd, 2009 at 10:38 am
Oops, I meant to say I disagree with the statement that the designation–or not–of an object as a planet does NOT matter. Let’s get that editing function up and running here, please!
March 3rd, 2009 at 2:52 pm
@ Laurel:
Your argument seems to amplify Nemo’s, that what you desire is simply a binary categorization of planet system bodies.
Or is there a deeper purpose of singling out rounded bodies (necessarily of different diameters depending on material), if we now pass beyond the old purpose of designating dominant bodies? (And definitely beyond the original purpose of designating ‘wandering stars’.) The IAU purpose, as I understand it, is to move on to designate natural populations, I assume because it suits the studied objects better, as results of natural processes.
If the population designation for some reason (which needs to be clarified, IMO) isn’t palatable, wouldn’t it as the next best option make more sense singling out those bodies that are differentiated? That trait would tell you something related to the result of geophysical processes of the body, as opposed to the geometry trait which AFAIU doesn’t correlate to anything specific to formation or anything else.
March 3rd, 2009 at 10:20 pm
Well said – & great pluto blog linked to your name there Laurel Kornfeld!
This Aussie Plutophile couldn’t agree more.
Thanks for the news about the exoplanets in the 3:2 resonace Pluto-Neptune analogue too – I hadn’t heard of that one yet although I do know many exoplanets are in highly elliptical orbits that are far more comet-like than Plutos! (Incl. one that was mentioned on this blog fairly recently.)
BTW. Were y’all aware that the smallest of the pulsar planets (PSR B1257+12 e) has amass just 1/5th of Pluto’s – yet is still considered a proper planet?
Or that applying the same illogical and unecessary “orbital clearance” criteria to the recently photographed exoplanets of Fomalhaut and HR 8799 would make them technically “dwarf planets” despite having many times the mass of Jupiter?
March 4th, 2009 at 9:48 am
MadScientist,
I don’t think the art is wrong at all. Charon is somewhat larger than the asteroid Ceres, which we know had enough mass to pull itself into a sphere during it’s formation. The other two moons of Pluto… Nyx and Hydra, are far, far smaller and are probably much more like the twin moons of Mars… potato-shaped chunks of ice and rock. If the art went wrong anywhere, it’s that they portrayed Charon being a bit small in it’s apperant size… but that really depends on what the angular view is. It looks wider than your standard 50 deg, for most edisonian aspect ratios… this seems to be laid out for wide screen monitors, so it’s closer to a 16:9 panavision ratio. (The wider the angle the smaller such distant objects appear in relation to the foreground) but it seems to me that Charon would appear a bit larger.
(shrug) Artistic lisence.
March 4th, 2009 at 1:26 pm
If Pluto is ever considered a major planet again, then include Eris, approx 5% greater in diameter & 27% greater in mass than Pluto. What about MakeMake & Haumea, two other KB bodies nearly as large as Pluto?
Pluto is currently the second largest known KBO. As more is discovered about the Kuiper Belt & the possibilty of more KBOs larger than Eris, Pluto’s standing will be reduced further. Pluto is only about 16% the mass of our Moon or only abot 8% the mass of Jupiter’s Ganymede.
What I wonder about this find, is if variations globally could be mapped, i.e if Pluto has active cryovolcanism. Also could these observations be used to see if there is a transfer of gas between Pluto & Charon?
Could the same observations be carried out on the largest currently known KBO Eris?
New Horizons will answer the cryovolcanism question for sure as a large part of Pluto’s surface will be imaged at high resolution (Charon’s too).
If I understand correctly Nix will be well placed to be well seen by New Horizons & Hydra’s general shape & some surface features should be seeable by NH.
Andrew Brown 3488.
March 4th, 2009 at 2:27 pm
StevoR, exoplanets and planets aren’t the same objects, and they are detected differently. So I wouldn’t expect the definitions to overlap. (Unless we start to go there, but that is a discussion for another day.)
March 6th, 2009 at 12:27 pm
“Because we’re curious apes”…
Awwwww, we’re so cute!
March 7th, 2009 at 5:18 am
@ Torbjörn Larsson, OM said (March 4th, 2009 at 2:27 pm) :
StevoR, exoplanets and planets aren’t the same objects, and they are detected differently. So I wouldn’t expect the definitions to overlap. (Unless we start to go there, but that is a discussion for another day.)
Yeah, it probably is a discussion for another day but when we talk of gas giant exoplanets around other stars and superEarths and the quest for another planet like ours its clear that exoplanets are also planets too -just ones outside our solar system.
So exoplanets are planets – as are ice dwrafs like Pluto, Eris & even Sedna.
IMHON.
March 13th, 2009 at 9:02 am
[...] It has an atmosphere OK, if you’re a regular reader of this blog you already knew that. But it still surprises me, so maybe it surprises you too. After all, Pluto is a long, long way [...]
March 21st, 2009 at 2:08 am
[...] A surprising discovery about the atmosphere of Pluto. [...]
September 16th, 2010 at 9:21 am
Pluto really is a fascinating planet. Apparently when the thin atmosphere gets blown to the cold side of the planet the nitrogen freezes and falls to the surface as snow. When New Horizons arrives I’m sure many other surprises will be uncovered.