Time to update your moon charts for the solar system.

July 20, 2011 2:11 PM

Pluto may have been downsized in 2006, but it's still living large, moon wise: A fourth moon has been discovered orbiting the dwarf planet.
posted by Brandon Blatcher (82 comments total)

That's no moon!

Oh, wait. Yeah it is.
posted by Eideteker at 2:12 PM on July 20, 2011 [4 favorites]

Can we call it Tyrrion?
posted by Trurl at 2:14 PM on July 20, 2011 [10 favorites]

There's nowhere else to go, out that way.
posted by StickyCarpet at 2:14 PM on July 20, 2011

I'm so sick of updating my moon charts for the solar system!
posted by swift at 2:16 PM on July 20, 2011 [3 favorites]

That's no moon!

I was sort of hoping it was a teapot. No such luck, I'm afraid.
posted by The World Famous at 2:16 PM on July 20, 2011 [3 favorites]

I'm still with the state of Illinois on this one — always and forever!
posted by Conrad Cornelius o'Donald o'Dell at 2:20 PM on July 20, 2011 [2 favorites]

I bet/hope they call it Erebus.
posted by aubilenon at 2:22 PM on July 20, 2011

Pluto used to be a planet, but now it isn't; Pluto didn't used to have moons, but now it does.

Read between the lines, sheeple.

You bastards! You blew it up!
posted by Sys Rq at 2:23 PM on July 20, 2011 [6 favorites]

Orrery maintenance is just getting ridiculously expensive these days.
posted by theodolite at 2:24 PM on July 20, 2011 [18 favorites]

That third link - the Nat'l Geographic interactive - is very neat.
posted by madamjujujive at 2:24 PM on July 20, 2011

Orrery maintenance is just getting ridiculously expensive these days.

All the fat-cat lobbyist bastards over on O street, with their caviar dinners, and their gold plated astrolabes...
posted by codacorolla at 2:27 PM on July 20, 2011 [3 favorites]

The New Horizons tag is confusing, the probe doesn't have anything to do with this discovery. Hubble made it. Also - Bad Astronomer Phil Plait has a write-up posted on this discovery.
posted by IvoShandor at 2:28 PM on July 20, 2011

Pluto doesn't know the meaning of the word 'quit'.
posted by Tknophobia at 2:28 PM on July 20, 2011 [9 favorites]

"Look how many moons I have, you guys! Isn't that cool? Do you like me now...?"

*sniff*
posted by brundlefly at 2:30 PM on July 20, 2011 [7 favorites]

The New Horizons tag is confusing...

Originally I had a sentence about the craft and mission in the post, so I added tags. Then deleted the sentence, but forgot the tags. They are now deleted.
posted by Brandon Blatcher at 2:35 PM on July 20, 2011

There's an old telescope sitting in the window of the Octagon Room at the Royal Observatory in Greenwich, just begging for people to bend down and peek through it. Some awesome person has replaced the lens with a picture of Pluto.
posted by phunniemee at 2:35 PM on July 20, 2011 [1 favorite]

there could be gold.
posted by clavdivs at 2:40 PM on July 20, 2011

I was sort of hoping it was a teapot. No such luck, I'm afraid.

I haven't seen any evidence that proves it's not a teapot, so I'm just going to assume that it is.
posted by strangely stunted trees at 2:40 PM on July 20, 2011

I'm so sick of updating my moon charts for the solar system!


Better get yourself a magnetic chart then - add a triple order of green checkmark magnets for all the successful space probes and their ION DRIVE BIZZNESS.
posted by CynicalKnight at 2:46 PM on July 20, 2011 [1 favorite]

I'm envisioning a headline: DWARF PLANET PROTESTS DEMOTION; MOONS ASTRONOMY COMMUNITY
posted by never used baby shoes at 2:47 PM on July 20, 2011 [4 favorites]

Orrery maintenance is just getting ridiculously expensive these days.

Wait so what is the thing owls live in called?
posted by griphus at 3:05 PM on July 20, 2011

I was sort of hoping it was a teapot. No such luck, I'm afraid.

I haven't seen any evidence that proves it's not a teapot, so I'm just going to assume that it is.

I don't need evidence, I KNOW it's a teapot.
posted by fuq at 3:06 PM on July 20, 2011

Until we name one of these things "Pizza Planet" I refuse to be interested in space.
posted by doublehappy at 3:11 PM on July 20, 2011

Dear Pluto,

I don't know if you can read this. I want to tell you that me and my family had nothing to do with your dawngraded. I can understand that you are angry and want to get MAAD but not all of us are meen buttheads. Mom sais you had a baby moon and I hope you are not trowing her at us ---- THE BLUE PLANET because I live here and I dont want to see my mom hurt and I like to play with my friends Debi and Brian 8 year. I hope you have friends that can give you lots of hugs when you are sad becus uncle matt sais every one needs hugs.

PS Is it cold in space? my mom can nit you a sweter.

Your friend,
Foci
posted by Foci for Analysis at 3:12 PM on July 20, 2011 [3 favorites]

Goddammit, the first moon puts up with a lot, the second is usually pretty grounded, the third moon is totally spoiled, but the fourth... well the fourth moon is always a bit of a wierdo.
posted by Elmore at 3:16 PM on July 20, 2011

I got the post and intentional bad spelling and all, but when I get around to writing my sci fi novel I'm going to title it "Dawngraded."
posted by Elmore at 3:19 PM on July 20, 2011

Changed from not being to being a planet by its author
posted by Meatafoecure at 3:22 PM on July 20, 2011

How cool is it that we can see things that are 20 miles across from 3 billion miles away? That's amazing, right?
posted by gc at 3:44 PM on July 20, 2011 [2 favorites]

Pluto was downgraded, not downsized.
posted by Chocolate Pickle at 3:58 PM on July 20, 2011 [1 favorite]

Whenever my kids watch schoolhouse rock, and Interplanet Janet comes on, I have to remind them that Pluto is not classified as a planet. It is a terrible burden to bear. I am grateful they never made a moon-tune.
posted by davejay at 4:20 PM on July 20, 2011

Absolutely! And making inferences about Pluto's atmosphere by observing occulted starlight is pretty neat, too.

Welcome to the world of human knowledge, P4! Sure you were always there, but we didn't see you until now, so this is kind of like being born. I hope you have lots of interesting details that we can puzzle over when the probe gets there in four years.

One of the neatest things about our Solar System is the structure it has, even way out in the 'burbs where the sun is just a large star. Out there everything is far away from everything else and space is really empty, but Pluto has its own mini Solar System goin' on with four moons simultaneously orbiting and lots of complex orbital dynamics.
posted by Kevin Street at 4:23 PM on July 20, 2011

MELANCHOLIA
posted by hermitosis at 4:31 PM on July 20, 2011

I'm honestly kind of surprised, after hearing all about ostensible super-earths in other systems and seeing how much of our galaxy is already charted (albeit rudimentarily), that there are still satellites in this system being discovered.

Guess I figured the latter would be good and finished before moving on to the former. But I guess an object's brightness is a lot more helpful to astronomers than its distance from Earth.
posted by The Winsome Parker Lewis at 4:32 PM on July 20, 2011

[Cues up a Pluto moon tune]
posted by NMcCoy at 4:34 PM on July 20, 2011

5th zoom destination smallest planet Pluto
On which there are many beautiful sights
It has no vegetation you know
No power to illuminate dark nights.

This has been on heavy rotation for reasons unknown this week.
posted by Devils Rancher at 4:37 PM on July 20, 2011

lots of complex orbital dynamics

One of the arguments against characterizing Pluto as a planet, I think, was that the center of mass of the Pluto-Charon system actually lies outside of Pluto.
posted by Wolfdog at 4:41 PM on July 20, 2011 [1 favorite]

That first link is not about Pluto getting "downsized". It's about new observations that might mean Pluto regains its former rank of 9th-largest planet of our solar system. And yes, it is a planet, obviously.
posted by sfenders at 4:42 PM on July 20, 2011

"One of the arguments against characterizing Pluto as a planet, I think, was that the center of mass of the Pluto-Charon system actually lies outside of Pluto."

Yeah, building a theoretical model of Pluto and its moons must be really complicated. It's like this nugget of intricate detail set in a vast empty space. And no doubt there's more cool stuff happening out there in the Kuiper belt and Oort cloud that's just waiting to be discovered.
posted by Kevin Street at 4:45 PM on July 20, 2011

One of the arguments against characterizing Pluto as a planet, I think, was that the center of mass of the Pluto-Charon system actually lies outside of Pluto.

I don't think that's correct - I don't think that's part of the definition of a planet. Rather, I think that Pluto is considered not to be a planet because it has not "cleared the neighborhood" - i.e. it shares its vague orbital neighborhood (the Kuiper Belt) with a whole bunch of other objects of somewhat comparable size which are not its moons.

The center of mass being outside both Pluto and Charon would mean that they're a binary dwarf planet system as opposed to a dwarf planet system (or, if they had cleared the Kuiper Belt, a binary planet system as opposed to a planet system).

I don't think that this "binary" stuff is an official definition, as "planet" is, but in any case, I'm pretty sure it's not part of the official definition of "planet".
posted by Flunkie at 4:53 PM on July 20, 2011

I think it's cool that one of the moons is named Nix.
posted by Guy_Inamonkeysuit at 5:00 PM on July 20, 2011

New moon
You thought that you were alone
Without another to love
Around your mother Pluto
posted by bwg at 5:01 PM on July 20, 2011

One of the arguments against characterizing Pluto as a planet, I think, was that the center of mass of the Pluto-Charon system actually lies outside of Pluto.

Does this mean that you would fall off (or at least could jump off) the surface of pluto and towards the gravitational centre if you were on the wrong side of the planet? That'd make for an interesting atmospheric cycle.
posted by dng at 5:02 PM on July 20, 2011 [2 favorites]

At the time, coming up with the "definition of a planet" was precisely the issue! There was not a formal definition; it was just kind of tacit that everyone knew what a planet was. Then the discovery of more large Kuiper belt objects forced the question because, if Pluto qualified, then a lot of other things apparently would, too, so there was a spectre of going from a tidy nine-planet picture with a handy mnemonic to possibly a hundreds-of-planets picture. There were a lot of proposed explanations for what "planet" should mean, many of them quite contrived to satisfy one particular viewpoint or another, and there was not, at any point, any sort of consensus about the matter.
posted by Wolfdog at 5:04 PM on July 20, 2011 [1 favorite]

I've probably just spent too long playing Mario Galaxy.
posted by dng at 5:05 PM on July 20, 2011 [1 favorite]

An Incantation for the Restoration and Repair of Eternal Planethood.
posted by scruss at 6:17 PM on July 20, 2011

We can talk about "metals" without obsessing over whether silicon and arsenic are metallic; we can talk about "continents" without obsessing about Greenland or whether North and South America count individually; we can also talk about planets without having to obsess over Pluto. We now know that there's nothing special about this category; we know that the nine planets are not necessarily distinguished by size or composition; but it's still a convenient way to refer to the big primary satellites close to our sun, even though Pluto isn't very big or very close.
posted by Joe in Australia at 6:26 PM on July 20, 2011

I say we call it Vogon.
posted by Mister_A at 6:50 PM on July 20, 2011

Joe in Australia, I'm actually supportive of your general argument that the word "planet" does not need a scientific definition attached to it, but your specifics show exactly what some people believe, not unreasonably, to be the problem:

the nine planets (...) a convenient way to refer to the big primary satellites close to our sun, even though Pluto isn't very big or very close.

If you say that (1) there are nine planets, (2) Pluto is one of those nine, and (3) a planet is a big primary satellite close to our sun, then you're excluding a big primary satellite that is closer to our sun than Pluto is, and at least one -- and quite possibly many -- primary satellites close to our sun bigger than Pluto.
posted by Flunkie at 6:55 PM on July 20, 2011

And, perhaps I should add, this is seen by some as a "problem" not merely due to nitpicking or whatever; rather, it's due to the fact that it leads people to make a significantly erroneous assumption about reality - that Pluto is somehow special in a way that other objects are not.
posted by Flunkie at 7:00 PM on July 20, 2011 [1 favorite]

H.P. Lovecraft imagined multiple moons circling Pluto. Oh, well. Only room on the new moon for tiny terrifying eldritch cities.
posted by Kronos_to_Earth at 7:23 PM on July 20, 2011

With an estimated diameter of 8 to 21 miles, P4 is the smallest of Pluto's four moons, the U.S. space agency said in a statement. ... "I find it remarkable that Hubble's cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles (5 billion km)," said Mark Showalter of the SETI Institute in Mountain View, California, who led this observing program with Hubble.

I knew it was a powerful telescope, but I don't think I've fully appreciated just how powerful it is until now.
posted by Marisa Stole the Precious Thing at 8:21 PM on July 20, 2011 [2 favorites]

The NASA twitter account referred to Pluto as a "dwarf planet" when they announced this. I like to think there are a bunch of disgruntled astronomers over there who rebel by sneaking calling it a planet whenever they can. And then they sit there in their lab coats and giggle and quietly high-five each other when they meet up in their astronomer clubs and whatnot. God, I hope that really happens.
posted by Dormant Gorilla at 8:26 PM on July 20, 2011

No, sorry Dormant Gorilla, "dwarf planet" is the official designation for Pluto (and various other objects). The definition was decided at the same time that the definition for "planet" was decided.
posted by Flunkie at 8:34 PM on July 20, 2011

Why does everyone always have to ruin my dreams.
posted by Dormant Gorilla at 8:53 PM on July 20, 2011

Whatevs. I'm over the Pluti is/is not a planet thing now. All I want is for the IAU to get on the ball and name SOMETHING out there Yuggoth. Hopefully one of the people in charge of picking names for P4 is a Lovecraft fan.
posted by KingEdRa at 9:26 PM on July 20, 2011

Can't we please, at last, name this Yuggoth?
posted by SPrintF at 9:28 PM on July 20, 2011

Oh, hey, KingEdRa. Great minds... y'know?
posted by SPrintF at 9:29 PM on July 20, 2011

I think Jonathan Coulton needs to update "I'm Your Moon" to a "I'm Your Moons" polyamorous situation.
posted by jenfullmoon at 9:34 PM on July 20, 2011

@ SPrint: I think Kronos_to_Earth beat us both to it. Just proof that the stars are finally right ...
posted by KingEdRa at 10:27 PM on July 20, 2011

Flunkie, I'm not saying that "a planet is a big primary satellite blah blah". I'm saying that there are nine planets, including Pluto. It's an enumeration, not a description, and it was settled when we started calling Pluto a planet. This enumeration is useful both for historical reasons and also because we sometimes want to talk about "the big primary satellites close to our sun". The term "planet" is a convenient shorthand for this idea even though the meanings of "big" and "close" are not well-defined.
posted by Joe in Australia at 11:04 PM on July 20, 2011

Flunkie, I'm not saying that "a planet is a big primary satellite blah blah"

What? I was quoting you. You said that the word "planet" is "a convenient way to refer to the big primary satellites close to our sun".

The problem with that is not that "the meanings of 'big' and 'close' are not well-defined". The problem is that if you say that there are nine and Pluto is one of them, then the meanings of "big" and "close" are nonsensical.
posted by Flunkie at 5:31 AM on July 21, 2011

The problem is that if you say that there are nine and Pluto is one of them, then the meanings of "big" and "close" are nonsensical.

Maybe a bit silly, but not entirely nonsensical. Pluto may yet turn out to be the largest of the dwarf planets, and it would not be inconsistent to define a "planet" to be anything that looks like a planet and is the size of Pluto or larger. In which case you'd have either 9 or possibly 10. It's a stupidly arbitrary way to define things, but it still makes more sense to me than saying that "dwarf planet" is not actually, as the name would imply, a type of "planet".
posted by sfenders at 6:24 AM on July 21, 2011

Maybe a bit silly, but not entirely nonsensical. Pluto may yet turn out to be the largest of the dwarf planets

Are you claiming that Eris is not larger than Pluto?
posted by Flunkie at 7:07 AM on July 21, 2011

Flunkie: "Are you claiming that Eris is not larger than Pluto?"

The latest estimate actually puts Eris at only 10km larger than Pluto, or about 0.05%. I agree that Pluto should definitely not be a planet. Also, "dwarf planet" is probably the stupidest term ever invented.

Coincidentally, I just created a a venn diagram indicating the relationships between all of the sub-classes of minor planets. You're welcome.
posted by Plutor at 8:34 AM on July 21, 2011 [2 favorites]

The latest estimate actually puts Eris at only 10km larger than Pluto

Which is "bigger". But more significantly, it's significantly more massive than Pluto (something like 28%). Also, incidentally, there are parts of its orbit that are closer to the sun than parts of Pluto's orbit.

That's why I'm saying it's "nonsensical". It's actually fine with me if people want to say that Pluto is a planet. It's even fine with me if they want to say that Pluto is a planet and Eris is not a planet. What I find silly is when people say that Pluto is a planet, Eris is not a planet, and the planets are the big primary satellites close to the sun.

Taking his "Greenland" example: Let's say that people from the east coast of Greenland knew about Greenland, Iceland and Europe, and that they referred to them as "the three continents", being the three "big land masses". Then one day an explorer decides to go west, and discovers North America. Everybody agrees that North America is there. Everybody agrees that it's bigger than Greenland or Iceland (they aren't yet sure about its size relative to Europe).

It's fine if they want to continue saying "there are three continents: Greenland, Iceland, and Europe".

It's also fine if they want to continue saying "continents are the big land masses".

What's silly is if they want to continue saying both. It's not a matter of "big" being loosely defined; it's a matter of there being no possible good definition for "big".
posted by Flunkie at 9:31 AM on July 21, 2011

Does this mean that you would fall off (or at least could jump off) the surface of pluto and towards the gravitational centre if you were on the wrong side of the planet? That'd make for an interesting atmospheric cycle.

Sadly, no. That point isn't the center of mass, it's the inner Lagrangian point, which is closer to Charon.

Also:

The International Astronomical Union's definition of planets and dwarf planets:

(1) A "planet" [1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

posted by BrashTech at 9:33 AM on July 21, 2011

Really, the size of Eris, compared to Pluto or not, is completely beside the point. Ceres is the largest asteroid by about 40% (952km vs Pallas's 544km). But to argue that it's a "planet" for any meaningful definition of the word is silly.

But I guess your point is that if people wanted to define planets emotionally or historically (meaning Pluto is in and Eris was out) that would be fine by you. Which is a perfectly tenable point of view. I don't personally agree, considering that for about half of the 19th century, several of the largest asteroids were considered planets.
posted by Plutor at 9:38 AM on July 21, 2011

Really, the size of Eris, compared to Pluto or not, is completely beside the point.

Then I don't understand what you think my point is.

Ceres is the largest asteroid by about 40% (952km vs Pallas's 544km). But to argue that it's a "planet" for any meaningful definition of the word is silly.

I'm not sure what that has to do with the comparative sizes of Pluto and Eris, but in any case, I don't really think that's true: Again, I am of the opinion that "planet" doesn't need a scientific definition, but if it's going to have one, something like...

1. Not a star
2. Not a moon
3. Massive enough to be spheroid due to its own gravity

... would be a "meaningful definition", and Ceres would fit it. So would Pluto and Eris.

In fact, I think it would be more than a "meaningful" definition; I think it would be a reasonable definition (obviously if made more exacting with definitions of "star" and "moon" and specificity for fringe cases like potential double planets and such). And actually, I think it would even be more reasonable than the current mess of a definition.

But I guess your point is that if people wanted to define planets emotionally or historically (meaning Pluto is in and Eris was out) that would be fine by you.

Yes, that's right. I am not against having the word "planet" be nonscientific in meaning. Nor, I should probably add, am I against simultaneously having a scientific term meaning the same thing as the current scientific definition of "planet".
posted by Flunkie at 10:09 AM on July 21, 2011

Flunkie: "something like... ... would be a "meaningful definition", and Ceres would fit it. So would Pluto and Eris."

The problem is that, although it's a scientific definition, it tells us nothing about stuff around stars. It's not a meaningful astronomical definition, just a physical one. It says something about physics and geology that isn't really that super interesting. There's something very obviously different between Ceres and Pluto and Eris on the one hand, and the Earth and Mercury and Jupiter on the other hand, and it's not just size. You could define planet as "things with oak trees on them" and that would be a specific and meaningful definition in some sense, but in another sense, it doesn't matter to astronomers.

"Massive enough to be spheroid due to its own gravity" is doubly problematic as a planetary definition because it's such a low bar. It would very likely give us 20 planets (or more -- Michael Brown says he thinks as many as 200). Schools and school children would revolt even worse than when we kicked Pluto out of the gang.
posted by Plutor at 10:58 AM on July 21, 2011

It is so damn hard to type Pluto instead of Plutor. Stupid muscle memory.
posted by Plutor at 11:10 AM on July 21, 2011

It says something about physics and geology that isn't really that super interesting.

I find it interesting. So does the IAU, apparently, as it is one of the prime requirements for both planethood and dwarf planethood.

There's something very obviously different between Ceres and Pluto and Eris on the one hand, and the Earth and Mercury and Jupiter on the other hand, and it's not just size.

And what is that? If you're referring to the "cleared their neighborhoods" stuff, first of all, that's just size too (merely a larger cutoff). Second of all, and probably more importantly, perhaps I should be more clear about my opinion:

I think it would be better to have definitions for "planets" and "major planets", with the former being a superset of the latter, than to have definitions for "planets" and "dwarf planets", with the two being unrelated. If it's interesting that something has cleared its neighborhood -- and I agree that it probably is -- then that's potentially a good candidate characteristic for being a "major planet".

As for 20 planets or 200, and what school children think, I really don't care. Reality is reality; if we choose to define "planet" such that reality says there are 200 of them, then there are 200 planets. And if school children want to continue saying there are 9, that's fine with me too, as long as they are taught to understand that the meaning of "planet" in science is different than the meaning of "planet" in popular culture. Just like they're taught (outside of the more conservative areas of our country) that "theory" and "theory" are different.
posted by Flunkie at 11:27 AM on July 21, 2011

Which, I should probably add, leads me to my actual ultimate opinion that the IAU should've probably just left "planet" undefined as a scientific term, and come up with new words for scientific use for whatever groupings they find interesting.
posted by Flunkie at 11:31 AM on July 21, 2011

Flunkie: "I think it would be better to have definitions for "planets" and "major planets", with the former being a superset of the latter, than to have definitions for "planets" and "dwarf planets", with the two being unrelated. If it's interesting that something has cleared its neighborhood -- and I agree that it probably is -- then that's potentially a good candidate characteristic for being a "major planet"."

On this, we can agree.

Flunkie: "the IAU should've probably just left "planet" undefined as a scientific term, and come up with new words for scientific use for whatever groupings they find interesting."

Er.. uh.. woo. Wow. Never really considered that one.
posted by Plutor at 12:37 PM on July 21, 2011

Flunkie: Are you claiming that Eris is not larger than Pluto?

I was accepting the claim made in the first link that they're not yet sure if it's larger, yeah. When I did a web search what I got was this which says the same in more detail.

Plutor: There's something very obviously different between Ceres and Pluto and Eris on the one hand, and the Earth and Mercury and Jupiter on the other hand, and it's not just size.

It isn't obvious that those groups are any more obviously different than are the Earth, Pluto, and Mercury on the one hand, and Jupiter and Saturn on the other; also not just size.
posted by sfenders at 1:02 PM on July 21, 2011

Sfenders, I almost made that point myself, but I didn't want to muddy the waters. At this moment, my opinion is that there should be three sub-classes of planets:

Terrestrial planets: Mercury, Venus, Earth, Mars
Gas giant planets: Jupiter, Saturn, Uranus, Neptune
Dwarf planets: Ceres, Eris, Pluto, Makemake, Haumea, etc.
posted by Plutor at 5:33 PM on July 21, 2011

Funny tweet from Jonathan Coulton on this subject.
posted by Flunkie at 6:58 PM on July 21, 2011

There's no lower limit on moon size. S/2011 P 1 is estimated to be 13-34km in diameter. Jupiter, on the other hand, has 48 moons that are smaller than 10km. Saturn has 36. Where they draw the line between moons and objects like Saturn's A-ring moonlets is kind of fuzzy. But since it's a "smaller" question than "what is a planet?", I don't think they really give it much thought. I bet you didn't even know that Jupiter and Saturn had more than 120 moons between the two of them.
posted by Plutor at 7:05 PM on July 21, 2011

Jeez, Plutor. I bet you didn't even know it's a joke.
posted by Flunkie at 7:14 PM on July 21, 2011

Are you sure it's a joke? Lots of people feel passionately that some Wrong was committed to Pluto. It's possible that JoCo doesn't actually feel that way and he's poking fun at those people, but I don't really know for certain.

And now that I think about it, "planet" is the only astronomical word I can think of that has such a rigid (no pun intended) definition. Where's the line between a large gas giant and a small brown dwarf? At how many stars does a globular star cluster become an elliptical galaxy?
posted by Plutor at 4:54 AM on July 22, 2011

Plutor, I don't know how strongly he feels about it if at all, but jokes can be made even by people who feel passionately about what they're joking about. And yes, I'm pretty sure that was a joke.

But the point of my comment was less "he's joking" and more "You 'bet I don't even know'? WTF is this, seventh grade?" At this point, though, I'll just assume that that was an unfortunate turn of phrase that you didn't intend the way it sounds to me - that being a weirdly aggressive, out of the blue, confrontational no I'm not stupid you're stupid kind of thing.
posted by Flunkie at 5:54 AM on July 22, 2011

I'm sorry that my comment was aggressive and confrontational; it wasn't intended that way. I knew the two planets had lots of moons, but I wouldn't have guessed nearly that many. I was trying to make the point that what defines a moon isn't really that important simply because moons are less prominent in the minds of even people who are well-informed about the solar system. I feel the IAU's focus on making planetness so defined is a direct result of non-astronomers caring so deeply.
posted by Plutor at 8:31 AM on July 22, 2011

I'm sorry that my comment was aggressive and confrontational; it wasn't intended that way.

No problem. Thanks.
posted by Flunkie at 10:35 AM on July 22, 2011