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August 24, 2006

Dwarf Planets

Yes, I heard. Yes, I told Athena, whose response, after asking for and receiving permission to use a very mild curse word, was: "Pluto's been demoted? That's crap!"

How do I feel about it? Seriously? Snarky rivalries with other science fiction writers who will undoubtedly be unbearably gloaty when I see them later tonight notwithstanding, I think it's fine. The IAU has created a new class of planet to recognize Pluto and its ilk ("dwarf planets"). Inasmuch as I've advocated classifying Pluto and its ilk as such, I can hardly complain when the IAU agrees with me on that matter. Now, what will be interesting is what the IAU will do when someone discovers one of these "dwarf planets" which actually does meet its official criteria for planetary status. Personally I don't doubt there are objects out there orbiting the sun massive enough to "sweep the lane" but which are fundamentally slushy balls of ice. Will someone try to add new restrictions to the definition to keep it out of the club? We'll have to see if the Pluto-hayta types rise again, with their ice-ist agenda.

Does this mean Pluto will now fade from cultural memory? We'll find out, but I'll say this much about it -- I'll be revising The Rough Guide to the Universe over the next year; in the previous edition of the book, I lumped in Pluto with Uranus and Neptune. In the revised book, I expect I'll be adding a new chapter: "Pluto and the dwarf planets." That's a bit of a promotion, I'd say. Personally, I think Pluto will be around for a while.

Now, back to the convention. See you all next Monday.

Posted by john at August 24, 2006 11:59 AM

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diddidit | August 24, 2006 12:39 PM

2003 UB313 can kick Pluto's ass.


Gabriel Malor | August 24, 2006 01:04 PM

Hey, I don't get something. If Pluto isn't a planet because it crosses Neptune's orbit, doesn't that mean that Neptune can't be a planet either?

I'm sure such an obvious point has been dealt with, but according to the report:

Much-maligned Pluto doesn't make the grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.

Jeff R. | August 24, 2006 01:23 PM

I was wondering the same thing about Neptune.

Also, does that mean that in 4,000,000 AD, when the other definition would turn the Earth and Moon into a double planet, instead the Earth merely ceases to be a planet? Not the most common 'end-of-the-world' scenario, that.

(Ditto if someone should spot a pair of Jupiter-sized objects orbitting one another with a barycenter between them around some distant star. Neither one actually a planet?)

R Sitze | August 24, 2006 01:26 PM

Speaking as the "step grand-son in-law" of Clyde Tombaugh (it's not really as complicated as it sounds) I have to say that the demotion is a bit disappointing, but not surprising.

One of the oddities about the wording of the ruling is the use of the word "Sun" instead of "Star." I suppose this means that only celestial bodies that meet the criteria and are in our own solar system can be planets. Does the way the ruling is phrased mean that planets can only exist here? Do we need a new term for planet-like bodies in orbit around other stars?

SladeJ | August 24, 2006 01:35 PM

I'm not sure why this is relevant, since when Pluto crosses Neptune's orbit, they're not exactly in close proximity, and since their orbits are in a 3:2 resonance, that's not going to change (barring interaction with some other massive body). By my standards, BOTH of them have "cleared the neihborhood" around their orbits. At any rate, I have to agree, if this is the cause for Pluto's demotion, Neptune should be on the chopping block as well.

Garth | August 24, 2006 02:09 PM

This paper should help clear up what "clearing the neighborhood around the orbit" means:


Personally I think they should just use that and not bother with roundness.

And I agree that it's very strange that they used "Sun" instead of star.

Carol Elaine | August 24, 2006 02:17 PM

Okay, Westerfeld, how much does it take to bribe the IAU?

Quite a pithy young lady, that Athena.

Bruce Adelsohn | August 24, 2006 02:23 PM

Probably the right call, scientifically (although, as with SCOTUS decisions that are stated not to be precedents, this decision was ruled local only, and not a galactic definition). But I'll still call it a planet out of habit, I think.

Hey, I still say "brontosaurus", okay? :-)

Gwen | August 24, 2006 02:26 PM

So Pluto's out because it's less massive than something it crosses the orbit of? And Neptune is in because it's more than five magnitudes of order more massive than Pluto?
So what'll happen when we have a Pluto-Charon-like double-planet thing going around some star out there *without* a Neptune-like party-pooper to outsize them both? Will we have to revise the definition again to decide which of the two gets to be a planet, or will we say that neither is?
I'm getting tired of the "oh darn, we just found a lot of Pluto-like planets out there, we better redefine 'planet' so we don't have to keep changing the textbook every time we found a new one" argument; even Scott Westerfield (rightly) makes fun of the idea that textbook-making should be the first concern of astronomers. Finding a lot of Earth-like objects in our solar system wouldn't have made us redefine planet, so I think it's just plain Pluto-hating (hayting, right?) that fuels all this, rather than pragmatic concerns.
And that CNN guy should be fed to a stuffed Cthulhu monster; he called 2003 UB 313 "2004 UB 313" the first time he said it. What's up with that? Can't be bothered to even get the year of discovery right?

James Nicoll | August 24, 2006 02:32 PM

"in the previous edition of the book, I lumped in Pluto with Uranus and Neptune."

Aside from distance from the sun, in what way are the two ice giants like Pluto?

Jeff R. | August 24, 2006 02:32 PM

Okay; so, having read the full article, Neptune and Terra are safe. The definition still falls apart if you find a large double planet with a close mass ratio in some system...

Chang | August 24, 2006 03:11 PM

When we demote a planet to a dwarf planet, we let the terrorists win.

Why not rename 2003 UB313 "Al Qaeda Wonderworld"?

Steve Brady | August 24, 2006 03:30 PM

You must unlearn what you have learned!

We'll have to see if the Pluto-hayta types rise again, with their ice-ist agenda.

Hey, I love ice! It just has its place, that's all. In my beverages.

Why not rename 2003 UB313 "Al Qaeda Wonderworld"?

Think they'd agree to move there if we did so?

rayyy | August 24, 2006 09:12 PM

Ha! They're obviously "activist" astronomers.

Clearmoon | August 24, 2006 10:39 PM

Steve Brady:

"You must unlearn what you have learned!"

Thank you, Steve... The true heart of this matter. Why do we find change so difficult to accept? This thinking only holds humanity back. Bear in mind, "scientists" once were convinced that "here there be dragons", and that the f-ing Earth was flat, among other fine determinations.

I think it's safe to say, if Pluto ever "crossed" Neptune's orbit at the wrong time, this debate would cease entirely.

In other words: Give it up, ball-of-not-cool-enough-to-be-a-comet lovers! The price of progress and human understanding is, you have to admit what you (and I) learned was WRONG - (or at least not completely right)... just like many other accepted "truths" in history.

Nothing at all wrong with that, as long as we learn from our error and grow by it.

Annalee Flower Horne | August 24, 2006 11:18 PM

"We love you plu-uto... oh yes we dooo! We love you plu-uto... we must be tru-ue... when they demote you, we're blue! Oh Pluto, we love you!"

I feel a V for Vendetta parody coming on: Pluto Prevails!

I've discussed this with the other residents of my hall, and they agree: "Pluto for Planet! Because A Bunch Of Humanities Majors Can't Be Wrong!"
Apparantly only about 300 of the 2,500 astronomers at the conference bothered to vote about the pluto issue. Let that be a lesson to fellow Plutophants about the dangers of not voting for the Hugos (that comparison made sense in my head... honest).

Carol Elaine | August 25, 2006 01:53 AM


In other words: Give it up, ball-of-not-cool-enough-to-be-a-comet lovers!

You'll pry Planet Pluto out of my cold dead hands!

I'll be alive, but my hands will be cold and dead because, well, Pluto's around -380 freaking degrees F, for Cthulhu's sake. But still...

Nikitta | August 25, 2006 05:46 AM

Hey! I like the term "dwarf planet"!

From now on, I will imagine pluto as an icy world inhabited by dwarves who happily carve their glorious kingdom into the rock. Maybe with the occasional orc or similar they can bash, so they won't get too bored.

I like that mental image. Don't confuse me with facts!

Buck | August 25, 2006 08:38 AM

How soon until the International Little People's Association, or some such group, complains about the term "dwarf planet" and its connotation of being 'less than' other planets?

Which brings to mind when the albino rights groups were complaining about the chalky characters in the last "Matrix" movies, only to become chagrined to find out they were meant to be ghosts and not albinos...

Tripp | August 25, 2006 09:06 AM


Why do we find change so difficult to accept?

That is easy for you to say. Now I've got to drive to Illinois, rummage through my parent's attic encountering who knows what, dig out my 6th grade science fair project on the solar system, edit the report and relabel the paper mache Pluto!

The report was typed out, so I'll probably have to retype the whole thing, meaning I'll have to dig out the typewriter, too.

So yeah, this change bothers me because of all the extra work I'm going to have to do! You kids with all your electronic on-line easily changed media have it easy.

Jon | August 25, 2006 11:32 AM

Of all the reports of the demotion of Pluto, this just has to be the strangest:

Luke | August 25, 2006 11:48 AM

Gwen: "So what'll happen when we have a Pluto-Charon-like double-planet thing going around some star out there *without* a Neptune-like party-pooper to outsize them both? Will we have to revise the definition again to decide which of the two gets to be a planet, or will we say that neither is?"

If by pluto-charon pair you mean really like pluto and charon, then it would be a double-planet.

If they are not near each other, then you will need to keep in mind that cleanliness does not imply absence of everything; it just means order. Neptune has brought Pluto into a 3:2 period relationship with it. If the pair were Pluto and Charon, then Pluto would be bringing Charon into a 3:2 relationship with it.

There are other possibilities which are clearer: are they in a Lagrange relationship? Then one must be substantially heavier for it to be stable, that could be the planet. On the other hand, it would initially seem that you could have a Jupiter with an Earth in its leading lagrange point. For whatever reason, this hasn't happened in this solar system despite about 14 chances for it to occur, so it seems that this is prohibited, at least to some extent. Probably because getting into a Lagrange point is just as hard as getting out of one, and there is no strong scattering center to work with like with a planet.

Doug Triplett | August 25, 2006 03:05 PM

In keeping with Jeff's comment above and considering all the changes being made in astrological terms, should we consider NOT calling this planet Earth anymore? Should we use the classic term of Terra? This would allow the term earth to refer to the ground on any planet and not just here or use "groundquake" (which sounds dumb) on other planets. Perhaps we should always refer to our star as Sol instead of the Sun.

Of course this raises concerns with other terms. As what is human gets redefined, (artificial intellegence, colonies on other planets, (possibly genetic uplift of animals) should we not call ourselves humans anymore? Should we simply be Terrans?

I know that as Science Fiction fans you will all have many opinions about this. What do you say?

Steve Buchheit | August 25, 2006 03:21 PM

Terrans would be highly inaccurate, as any animal (or plant) from Terra would be a "Terran."

PixelFish | August 25, 2006 03:44 PM

I see I wasn't the only one to go, "Hey, doesn't that disqualify Neptune too???" Or at least wonder how a planet can clear its orbit entirely?

Jon Marcus | August 25, 2006 03:51 PM

Doug, there haven't been any astrological changes:


"I'm going to continue using it," said Wall Street's best-known astrologer, Arch Crawford, who has studied the effect of the planets on the Dow Jones Industrial Average. ``They can stick it where the sun don't shine,"

Astrologers pretty much seem to have decided to ignore astronomers on everything. Why should Pluto be any different.

Gabriel Malor | August 25, 2006 03:52 PM

Here's an interesting report on "Pluto backlash." My favorite part:

Stern said like-minded astronomers had begun a petition to get Pluto reinstated. Car bumper stickers compelling motorists to "Honk if Pluto is still a planet" have gone on sale over the internet and e-mails circulating about the decision have been describing the IAU as the "Irrelevant Astronomical Union".

Eric | August 26, 2006 03:52 PM

Has no one thought about what this does to the old mnemonic? Must it now be changed to:

My Very Educated Mother Just Served Us Nothing...?

Not only do we lose Pluto as a planet, but our children will have to recite a depressing paean to maternal neglect and childhood abandonment.

I'm trying to think of a substitute mnemonic involving my mother and unionized ninjas, but my heart's not in it. I'd rather continue to call Pluto a planet and to Hell with the IAU.

Annalee Flower Horne | August 26, 2006 07:48 PM

Eric, I think we're going with nectarines.

Or at least that's the one that I made up for the previous comment thread.

Primate | August 26, 2006 10:48 PM

Heh. Choosing "dwarf planet" as the term of choice means the anti-pluto crowd has lost the war, even if they managed to get it temporarily bumped from the list of "real planets" of our solar system. I don't know of any astronomers who look at the categories for stars and conclude that a white dwarf doesn't belong on that list. Sticking planet directly into the name of our tiniest planets just puts the planets into a scale of small, medium, and super-size. The public is used to classifying objects like that without changing their underlying concept that all three are milkshakes.

And speaking of chocolate, vanilla, and strawberry, I have to admit I'm still confused why some have argued that being mostly ice reduces Pluto to an oversized comet. By that logic, the terristial planets (iron-nickle) are just oversized asteroids, while the jovians (hydrogen-helium) are failed stars.

Matt McIrvin | August 27, 2006 11:02 AM

Well, asteroids have also been called "minor planets" ever since the first four discovered were demoted from planet status, and they haven't regained it (though Ceres just came awfully close).

Scott | August 28, 2006 10:17 AM

"Pluto's been demoted? That's crap!" should be on a t-shirt!

Eric | August 28, 2006 03:45 PM

"Pluto's been demoted? That's crap!" should be on a t-shirt!

I'd buy it!

daniel | August 31, 2006 12:26 PM

dwarf planet, gas planet, rocky planet in my book thier the same thing pluto is still being called a planet

Mark | September 1, 2006 02:16 PM

All non "Pluto-hayta types" should take a look at these 2 articles:

Kind of sounds like Pluto could be making a comeback.

paige | September 8, 2006 05:29 PM

well its good news for me i mean i have been saying it since i was 12. honestly do you know of any other planet that orbits another. if you look at he paths during certain times pluto was the 8th not the 9 th planet. honestly what took them so long.

daniel | September 8, 2006 07:43 PM

sorry dude but pluto doesn't orbit anything but the sun

April Ways | September 25, 2006 11:43 AM

I like pluto why dose it have be a dwarf planet

daniel | September 26, 2006 11:15 PM

i just read on another site that they are expecting to find some of these dwarf ice planets to be the size of earth

daniel | September 26, 2006 11:17 PM

also don't forget that the earth has gone around the sun 4 billion times

where as the planet pluto has only gone around 40 million times

Jonathan | September 27, 2006 12:35 AM

Heh heh, he said "lumped in Pluto with Uranus".

nicky | September 27, 2006 04:33 PM

[deleted because just looking at the stupidity encoded within made my brain hurt -- JS]

Jonathan | September 27, 2006 11:04 PM

Wow, and my lame beavis and butthead remark makes it past the Scalzi filter... so considering, it must of been a REALLY really stupid remark. And now I'm curious... how retarded can a comment actually BE on this topic? Which thread rule did it violate?

Bill | November 15, 2006 09:55 AM

wtf are you talking about?

is it like dungeons and dragons stuff or like stuff about the actual dwarf planets?

John Scalzi | November 15, 2006 10:04 AM

Uh, Bill, did you actually read the entry? It's pretty clear we're talking about Pluto, et al.

Vic | December 13, 2006 05:59 PM

I dont know what to say.

I like Pluto... I guess


Anonymous | December 13, 2006 06:01 PM

i likedy face

CRaig | January 31, 2007 05:36 PM

Pluto not a planet? If Pluto isn't a planet than scientists should stop looking for others. Clarly Pluto should be a planet because if it isn't Neptune isn't actually a planet either. Because Pluto and Neptune switch distances from the sun. Scientists though of that. Pluto has it's moon so let it be a planet. Mercury and Venus don't have moons.

Amy Cannon | April 8, 2007 05:16 PM

hiyah i like the word dwarf it reminds me of snow white for a reason anyway i'm making a l
paper mache of pluto i need some ideas people!

yoyo | May 11, 2007 04:44 AM

hey i am just a year 8 girl and and yea Pluto is cool but why are you all making a big fuss over a name come on ! when there is better things in life looking after are own Planet earth dose that ring a bell

yoyo | May 11, 2007 04:53 AM

i like Planets and yea Pluto's dead but it is not like i dont like it any more i know more about Pluto now been dwarf Planet then i did befor when it was just a Planet so i dont know what all this fuss is about a name

maryann | May 18, 2007 02:45 PM

HI!!!!!!!!!!!!!!!! :)

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