Hubble finds Pluto's 5th "moon"

[Christopher]

^Exactly. The choice of which borders to emphasize was made for cultural reasons. If Indians had become the great navigators and globally pervasive culture that made the maps everyone ended up using, then maybe India would be counted as a separate continent and Europe wouldn't. But since Europeans made the maps, they wanted to define themselves as separate from Asia.

And the Ural Mountains weren't the originally defined border between Europe and Asia; that convention is only about 150 years old at most. For much of history the border was placed further west by European mapmakers. But Russian/Soviet cartographers insisted on shifting the border to the east because they wanted Russia to be seen as part of Europe.

And there's no really good geological reason for why (most of) Turkey and the Arabian Peninsula are called part of Asia while countries directly north of Turkey are called part of Europe. That's just geopolitics.


Anyway, on your other point, I've never understood the notion that there's some reason to "feel sorry" for Pluto just because its definition was refined, or that becoming a dwarf planet was a "demotion." Before, Pluto was the last and least of the planets, an afterthought in a category that few astronomers seriously thought it belonged in. Now, it's the original and archetypal member of a whole new category of objects, the champion of its weight class. It's no longer a leftover that astronomers are awkward about, but the stepping stone to an exciting new period of discovery. That's a step up, not a step down.

 

[RoJoHen]

Really, if simplicity were the prime concern, then we would've long since dropped the conceit that Europe is a distinct continent and just gone with six instead of seven.

There was a thread here a while back where I learned that some countries actually do teach six continents. I don't remember exactly who it was, but they were taught that North America and South America are actually part of the same continent, simply called "America." They had never heard of them being separate before.

 

[gturner]

As an aside, why do they think this is Pluto's fifth moon and not its third or seventh? Do astronomers really think they discover moons in the correct numerical order?

*pokes at astronomers*

 

[Timewalker]

^But that would exclude most of the moons in the Solar System. Besides, some moons are large enough to be called planets if they weren't in orbit of larger bodies. So if you're going to call planetlike bodies moons, there's no reason not to call asteroidlike bodies moons too.

As long as it's a chunk of some kind of rock that isn't a comet and orbits a planet (or Kuiper Belt Object), it's a moon. The shape doesn't matter for this purpose. After all, Phobos and Deimos have been considered Mars' moons for a long time - are we suddenly going to get "shapist" about it?

Yeah, I think the IAU definition is very flawed due to the politics behind it. I like the dwarf planet category, but it makes no sense to say a dwarf planet isn't a planet, given that a dwarf star is still a star, a dwarf galaxy is still a galaxy, etc. (A dwarf kiss is still a kiss?)

As I've pointed out many times before, it wasn't about politics as much as it was educational expedience. Grade school teachers -- most of whom find astronomy HORRIBLY boring -- have a hard enough time just teaching the names of the major planets. Adding pluto as a planet meant also recognizing Ceres and god knows what else might be lurking out there in the kuiper belt. THe IAU figured it would be easier to restrict "planet" to mean the eight major planets that school kids will learn about and "dwarf planet" to be in a separate category altogether.

That's ridiculous. I grew up learning that there are 9 planets. While I didn't start learning the names of the other moons until I took astronomy in junior high and did a LOT of extra reading because the course material was so light, I didn't find it hard to remember the names of the Jovian satellites (thank you, Isaac Asimov!). Granted, I don't know all of their names, but at least I know the major ones for the major planets. And I'm perfectly aware that Ceres is in the asteroid belt. If kids can be expected to memorize the names of 50 states and their capitals, surely they can memorize more than 8 planets!

Anyway, on your other point, I've never understood the notion that there's some reason to "feel sorry" for Pluto just because its definition was refined, or that becoming a dwarf planet was a "demotion." Before, Pluto was the last and least of the planets, an afterthought in a category that few astronomers seriously thought it belonged in. Now, it's the original and archetypal member of a whole new category of objects, the champion of its weight class. It's no longer a leftover that astronomers are awkward about, but the stepping stone to an exciting new period of discovery. That's a step up, not a step down.

Pluto is little and really far away, and we can't even see it without a telescope. It just seems like a terribly lonely part of the Solar System...

(yes, I'm sentimental - I even cried after reading Murmurs of Earth. Deal with it.)

 

[rhubarbodendron]

Before, Pluto was the last and least of the planets, an afterthought in a category that few astronomers seriously thought it belonged in. Now, it's the original and archetypal member of a whole new category of objects, the champion of its weight class. It's no longer a leftover that astronomers are awkward about, but the stepping stone to an exciting new period of discovery. That's a step up, not a step down.

Right you are! Thanks for the reminder. Normally I'm a positive thinker myself but atm I have quite some stress (impending move, threatening to cost me almost all my savings and as many nerves) which makes me more of a whiner right now.

Timewalker, this is merely a hypothetic question, but would a comet that got caught by a planet be reclassified as a moon?

 

[Timewalker]

Timewalker, this is merely a hypothetic question, but would a comet that got caught by a planet be reclassified as a moon?

Yes, if I remember my reading correctly, some of Jupiter's and Saturn's moons are ex-comets that came too close and got captured.

Grade school teachers -- most of whom find astronomy HORRIBLY boring -- have a hard enough time just teaching the names of the major planets.

This is not the fault of the students - it's the fault of the teachers. The first degree I went for in college was a B.Ed. in Elementary Education. When I did my first-year practicum, the class was a mixed one of Grades 3-4. The teacher asked me which class I'd like to teach on my own (she'd be sitting at the back, observing), and I asked which units she intended to teach in science. Any astronomy? She said she hadn't planned on any astronomy at all! So I said I'd like to do that - I already had loads of books and posters and stuff at home.

So I did an abbreviated unit on astronomy. And I ran right into the "Alberta is a bible belt, and even though public schools are supposed to be religion-free, this class isn't (morning prayer was mandatory, even for an atheist student teacher)" problem. One of the kids asked me where the universe came from... and dammitall! For the sake of a GRADE in my practicum, I didn't dare tell the truth, but had to fudge some stupid sit-on-the-fence explanation for fear of what might happen if one of the kids went home and said, "the student teacher said the Bible's wrong, Dad..."

At least years later, when I gave astronomy lectures at the local nature center, I didn't need to worry about anybody's hurt religious feelings.

 

[Kolrad]

Pluto is a slacker; if it had cleared its neighborhood of debris like a big planet, we wouldn't be having this discussion.

:P

 

[iguana_tonante]

Anyway, on your other point, I've never understood the notion that there's some reason to "feel sorry" for Pluto just because its definition was refined, or that becoming a dwarf planet was a "demotion."

Honestly, I've never understood the notion how anybody could "feel sorry" for Pluto, as it is just a ball of rock and ice and I suspect it doesn't care much one way or the other.

If tomorrow botanists will come out redefining that pines are actually herbs instead of trees because that would fit better new genetic data, or simply for classification purposes, I wouldn't care one iota. I am befuddled why people who don't care (or know) much about astronomy or planetology feel so strongly about Pluto, and need to make a fuss over it.

 

[Christopher]

Pluto is little and really far away, and we can't even see it without a telescope. It just seems like a terribly lonely part of the Solar System...

Are you kidding? "Lonely?" See, this is the problem. People keep making the mistake of thinking that the renaming is about Pluto alone, but it isn't. The reason Pluto's status changed to dwarf planet is because we've discovered over the past couple of decades that it is very, very far from being alone. Pluto is the first-known member of the Kuiper Belt, a belt of minor planets beyond Neptune that includes multiple dwarf planets and is much larger and more densely populated than the so-called Main Asteroid Belt, as much as 200 times as massive. There are now over a thousand known Kuiper Belt objects and it's believed there are tens of thousands of large ones yet to be found. It's estimated that the Belt could contain as many as 200 dwarf planets, with potentially thousands more in the scattered disk beyond the Belt. And that's why Pluto's status was changed. Astronomers never really liked calling it a planet, but they never had a better category for it. Discovering all these other dwarf planets finally gave us a better category, a place where Pluto actually belonged.

So far from being "lonely," Pluto is a resident of the most richly populated region of the entire Solar System, a region that we're only just beginning to chart and that could contain quite a few surprises. The idea that Pluto's domain is an empty, quiet backwater is 20 years out of date. It's probably the most exciting part of the Solar System right now from a planetary astronomer's point of view.

 

[CorporalCaptain]

I am befuddled why people who don't care (or know) much about astronomy or planetology feel so strongly about Pluto, and need to make a fuss over it.

I suspect it's because the recategorization contradicts what they were taught in school; in conjunction with the aging process it's just another nail in the coffin, yet another sign of their increasing obsolescence and of the young taking over. Hence the emotional reaction against it.

 

[B.J.]

As an aside, why do they think this is Pluto's fifth moon and not its third or seventh? Do astronomers really think they discover moons in the correct numerical order?

*pokes at astronomers*

I know you're being facetious, but just in case anyone didn't know, this 5th discovered moon is actually 2nd closest to Pluto (so far!).

So I did an abbreviated unit on astronomy. And I ran right into the "Alberta is a bible belt, and even though public schools are supposed to be religion-free, this class isn't (morning prayer was mandatory, even for an atheist student teacher)" problem. One of the kids asked me where the universe came from... and dammitall! For the sake of a GRADE in my practicum, I didn't dare tell the truth, but had to fudge some stupid sit-on-the-fence explanation for fear of what might happen if one of the kids went home and said, "the student teacher said the Bible's wrong, Dad..."

Odd. I grew up in what has been called the bible belt in the US, and I've never seen this problem myself. Maybe it's more prevalent in the extremely rural parts, but teachers don't have any problems talking about the big bang, etc. My kids are going to Catholic school, and even they teach all that stuff.

 

[Crazy Eddie]

As I've pointed out many times before, it wasn't about politics as much as it was educational expedience. Grade school teachers -- most of whom find astronomy HORRIBLY boring -- have a hard enough time just teaching the names of the major planets. Adding pluto as a planet meant also recognizing Ceres and god knows what else might be lurking out there in the kuiper belt. THe IAU figured it would be easier to restrict "planet" to mean the eight major planets that school kids will learn about and "dwarf planet" to be in a separate category altogether.

If that's true (and I've never heard it before, so I'd also like to know your source), that sure sounds like politics to me -- doing something because it suits some agenda or public-relations consideration rather than because of the science.

Politics is about people, and since nobody actually LIVES on Pluto I don't think it's accurate to say it's a political decision. It's more of a PR move than anything else.

What alot of people don't seem to understand is that the IAU is composed of the same kind of people who think that one of the most important reasons to have a manned space program is to "inspire a new generation of students to become engineers and astronauts." It's a very weird kind of mindset, but it's one in which overly-complicated lesson plans in a 3rd grade classroom is a really big deal.

It also needs to be understood that the definitions we're discussing -- planets, dwarf planets, moons -- are the simplistic labels they teach to school children and older students who won't be studying astronomy in any real depth. Most of the bodies of the solar system fall into about twenty other categories that, depending on their context, are a hell of a lot more relevant.

To put that another way: demoting pluto to a dwarf planet makes a difference only as far as a third-grader's understanding of astronomy. If they changed its definition so that Pluto was no longer a trans-neptunium object (discovered something unusual about its orbit?) THAT might actually mean something.

I don't think so. The only actually arbitrary boundary between continents is the one between Europe and Asia

I've been told by a surprising number of people that a lot of Spanish language geology texts -- especially in Central America -- teach a world divided into six continents, with north and south America being the same continent (sometimes described as sub-continents, depending on the source). I've also seen textbooks that teach it with eight continents, India being the 8th.

Really, if simplicity were the prime concern, then we would've long since dropped the conceit that Europe is a distinct continent and just gone with six instead of seven.

Simplicity isn't a concern where the continents are concerned, that is pretty much arbitrary and depends on worldview.

That wasn't the point I was making vis a vis pluto, though, considering -- once again -- nobody actually LIVES on pluto.

 

[Crazy Eddie]

That's ridiculous. I grew up learning that there are 9 planets.

Yep. 9 is easy to remember. More importantly, it's easy for grade school teachers who don't care about astronomy to teach.

In the IAU, it really came down to this: given its circumstances, if Pluto is a planet, then so is Sedna. If Sedna is a planet, then so is a potentially huge number of Kuiper belt objects we're about to discover with a new generation of telescopes. Worse yet, if the Kuiper Belt objects are planets, then so is Ceres, and possibly even Vesta.

14 planets? Not so easy to remember. Especially when half the teachers in America still have to use a mnemonic device just to remember their names. So, they decided, it's easier to take all the new "sorta planets" they had found/were about to find and put them in a separate chapter called "Dwarf planets" which could be written to contain everything scientists currently know about them (thus it will be a VERY SHORT chapter).

If kids can be expected to memorize the names of 50 states and their capitals...

Are they?

Because between my two oldest kids and most of their friends, I doubt any of them could name more than six of them without using google.

 

[Christopher]

Politics is about people, and since nobody actually LIVES on Pluto I don't think it's accurate to say it's a political decision. It's more of a PR move than anything else.

What a completely bizarre and disingenuous way of responding. Obviously the people we're talking about are the people who chose the definition and the people who would use it. It was a political decision because it wasn't a scientific decision, because it wasn't about the facts and the relationships between objects but on the basis of what would be expedient or convenient for certain people.

14 planets? Not so easy to remember. Especially when half the teachers in America still have to use a mnemonic device just to remember their names. So, they decided, it's easier to take all the new "sorta planets" they had found/were about to find and put them in a separate chapter called "Dwarf planets" which could be written to contain everything scientists currently know about them (thus it will be a VERY SHORT chapter).

Still, the scientific community could categorize planets into major and dwarf categories, or giant, midsize, and dwarf categories, and schoolbooks and teachers could just say "The major planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, and there are a lot of minor planets too, like Ceres in the Asteroid Belt and Pluto in the Kuiper Belt."

Actually, of course, the IAU definition isn't binding on any scientists; they don't have to use it at all. Heck, many scientists had already decided Pluto wasn't a planet long before the IAU got involved. And in scientific parlance, things like asteroids and KBOs are already known as "minor planets."

If I were teaching Solar-System astronomy, I'd teach it by region:

"First there's the inner system, which has the mid-sized rocky planets, Mercury, Venus, Earth, and Mars. This part of the system has the least amount of water and gas, since the heat of the Sun evaporated most of it, though the bigger planets were able to hold onto some of it.

"The outer boundary of the inner system is the Main Asteroid Belt, which has rocky bodies closer in and bodies that are a mix of rock and ice further out. The main body in the Asteroid Belt is the dwarf planet Ceres.

"The middle system has the giant planets, Jupiter, Saturn, Uranus, and Neptune, and their many moons and rings. Since they're farther from the Sun, they have a lot more hydrogen and ice, so the planets can be much bigger.

"The outer bountary of the middle system is the Kuiper Belt, made up of hundreds of thousands of small icy bodies which sometimes fall inward and become comets. The main body in the Kuiper Belt is the dwarf planet Pluto.

"The outer system is everything beyond the Kuiper Belt, including many dwarf planets and icy minor planets. It stretches out nearly a light-year to the Oort Cloud, a vast spherical cloud of cometary bodies which is the outermost region of the Solar System. We're only just starting to discover what's in the outer system, and it may even include a new planet or two."

I think if you broke it down into regions like that, it would be easier to remember. Maybe you could even teach each region as a grouping of four similar bodies:

Inner system: Mercury, Venus, Earth, Mars
Main Belt: Ceres, Vesta, Pallas, Juno
Middle system: Jupiter, Saturn, Uranus, Neptune
Kuiper Belt: Pluto, Haumea, Makemake, [whatever 2007 OR10 is named]
Outer system: Eris, Sedna, [whatever else may be discovered]

Okay, that's not a perfect system, but I think the way our Solar System is arranged lets us neatly break the major planets down into two groups of four, and if you can nest levels of organization like that, and associate groups by their physical and orbital similarities, it might make them easier to memorize -- as well as being more accurate and informative than just lumping terrestrial and giant planets into a single grouping. Really, we should treat giant, terrestrial, and dwarf planets as three distinct classes rather than two.

If kids can be expected to memorize the names of 50 states and their capitals...

Are they?

Because between my two oldest kids and most of their friends, I doubt any of them could name more than six of them without using google.

I never had to memorize the capitals, but I still remember this earworm of a teaching song I learned in grade school for the state names in alphabetical order. I just looked it up online and it's called "Fifty Nifty United States," and I can inflict it on you courtesy of YouTube (though their version's a bit different from the one I learned). To this day, when I need to run through the state names in my memory, I do so with that song in the back of my mind.

 

[Timewalker]

So I did an abbreviated unit on astronomy. And I ran right into the "Alberta is a bible belt, and even though public schools are supposed to be religion-free, this class isn't (morning prayer was mandatory, even for an atheist student teacher)" problem. One of the kids asked me where the universe came from... and dammitall! For the sake of a GRADE in my practicum, I didn't dare tell the truth, but had to fudge some stupid sit-on-the-fence explanation for fear of what might happen if one of the kids went home and said, "the student teacher said the Bible's wrong, Dad..."

Odd. I grew up in what has been called the bible belt in the US, and I've never seen this problem myself. Maybe it's more prevalent in the extremely rural parts, but teachers don't have any problems talking about the big bang, etc. My kids are going to Catholic school, and even they teach all that stuff.

This did not happen in an "extremely rural" area. I live in the third-most populated area of the province. The thing is, our province has been governed by a right-wing party for OVER 70 YEARS. The premier before this one allowed legislation to be enacted that said parents could pull their kids out of science classes at the first mere hint of evolution being discussed, and health classes that dared to go into sex education that the parents didn't want their kids to hear.

Our public school system is supposed to be religion-neutral, but there are individual teachers who cross the lines. My Grade 1 teachers made us pray and say grace at lunchtime. My high school English teacher assigned us reading out of The Jerusalem Bible and we knew that when it came to poetry interpretation, we'd better come up with some kind of religious slant, or risk a lower mark. It confounded my teacher to have to deal with an openly-atheist, Star Trek & science fiction-loving student who rejected religion (this was in the late 1970s).

I'd hoped to leave all that nonsense behind when I got to college, but noooOOOOooooo... I wound up student-teaching in a public school where the regular teacher had the kids pray every morning, and she told me I HAD to participate. I felt like I was back in Grade 1, resentful and telling myself, "You can make me stand, but you can't make me say the words or believe this stuff." It's too bad this was before Canada's Charter of Rights and Freedoms was enacted; I'd have had a valid case of her violating my Charter rights.

And then my sociology teacher turned out to be Mormon, and tried to convert me after I scored in the negatives on a survey that asked how important religion was in my daily life. I could have reported him for that; some of the students said I should have. But I gave him the benefit of the doubt since he never tried to coerce me by hinting that my grade was at risk.

That's ridiculous. I grew up learning that there are 9 planets.

Yep. 9 is easy to remember. More importantly, it's easy for grade school teachers who don't care about astronomy to teach.

In the IAU, it really came down to this: given its circumstances, if Pluto is a planet, then so is Sedna. If Sedna is a planet, then so is a potentially huge number of Kuiper belt objects we're about to discover with a new generation of telescopes. Worse yet, if the Kuiper Belt objects are planets, then so is Ceres, and possibly even Vesta.

14 planets? Not so easy to remember. Especially when half the teachers in America still have to use a mnemonic device just to remember their names. So, they decided, it's easier to take all the new "sorta planets" they had found/were about to find and put them in a separate chapter called "Dwarf planets" which could be written to contain everything scientists currently know about them (thus it will be a VERY SHORT chapter).

Having had a teacher dock me marks for capitalizing Earth in a paragraph I wrote about the planets (it was news to her that Earth is a planet, just like Saturn), I understand that there are some really ignorant teachers. But what mnemonic would they use to memorize the planets' names?

If kids can be expected to memorize the names of 50 states and their capitals...

Are they?

Because between my two oldest kids and most of their friends, I doubt any of them could name more than six of them without using google.

Are you American? If so... yikes. In my geography classes, we were expected to know the Canadian provinces/capitals, the US states, and a hefty chunk of the countries of the world. In my college geography classes, we were expected to know countries, major bodies of water, and ocean currents. Mind you, the instructor informed us that he would never ask us to label the East Australia Current on an exam because it would be too easy - "Unless you do not know where Australia is!" Maybe it's time to bring back "Where in the World is Carmen Sandiego?" on TV. Even as an adult, I loved that show.

 

[RoJoHen]

Maybe it's time to bring back "Where in the World is Carmen Sandiego?" on TV. Even as an adult, I loved that show.

I do feel like that's how I learned the majority of my geography.

 

[Timewalker]

Maybe it's time to bring back "Where in the World is Carmen Sandiego?" on TV. Even as an adult, I loved that show.

I do feel like that's how I learned the majority of my geography.

Who cares how you learn it, as long as it works? And it certainly didn't hurt that those Rockapella guys were cute!

 

[USS Fardell]

As an aside, why do they think this is Pluto's fifth moon and not its third or seventh? Do astronomers really think they discover moons in the correct numerical order?

*pokes at astronomers*

True: The Galiliean moons of Jupiter are numbered 1 through to four (Io I, Europa II, Ganymede III, Callisto IV). Then when a fifth moon was discovered it was labled as the fifth despite it having an orbit within that of Io (Amalthea V).

 

[Christopher]

As a rule, exoplanets are lettered in the order of discovery; the first one found is b (since the star itself is A), then c, d, e, etc., regardless of their relative orbital positions.

 

[Crazy Eddie]

Politics is about people, and since nobody actually LIVES on Pluto I don't think it's accurate to say it's a political decision. It's more of a PR move than anything else.

What a completely bizarre and disingenuous way of responding. Obviously the people we're talking about are the people who chose the definition and the people who would use it. It was a political decision because it wasn't a scientific decision, because it wasn't about the facts and the relationships between objects but on the basis of what would be expedient or convenient for certain people.

It's convenient and expedient for EVERYONE, not merely for certain people. No living person has invested enough of anything in Pluto -- let alone in the definition of "planet" -- to be inconvenienced by this definition.

Politics would be if there was actually a faction of scientists whose interests in some way depended on the fact that Pluto is one of the major planets in the solar system, or if there was a colonial movement that would find it hard to get investors if they had to keep explaining to people why a dwarf planet was as interesting as a regular planet, and so on. IOW, politics implies the favoring of one group of interests at the expense of others.

In this case there is literally NOTHING riding on Pluto's status; the IAU could just as easily declare it an "Kuiper Enigma Body" or something; it doesn't change anything for the of people who study astronomy professionally.

Still, the scientific community could categorize planets into major and dwarf categories, or giant, midsize, and dwarf categories, and schoolbooks and teachers could just say "The major planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, and there are a lot of minor planets too, like Ceres in the Asteroid Belt and Pluto in the Kuiper Belt."

Which is exactly what they do. Why did you assume otherwise?

Actually, of course, the IAU definition isn't binding on any scientists; they don't have to use it at all.

They DON'T use it at all. I repeat: this definition was meant to make things easier for school teachers and children. Which, I'm pretty sure, excludes professional astronomers and astrophysicists.

If kids can be expected to memorize the names of 50 states and their capitals...

Are they?

Because between my two oldest kids and most of their friends, I doubt any of them could name more than six of them without using google.

I never had to memorize the capitals, but I still remember this earworm of a teaching song I learned in grade school for the state names in alphabetical order.

I remember the song, but I still can't remember all the state names all the time. Never knew the capitals either.