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Can We Call Pluto and Charon a 'Binary Planet' Yet?

timothy posted about 3 months ago | from the complex-gyrations dept.

Space 115

astroengine writes The debate as to whether Pluto is a planet or a dwarf planet rumbles on, but in a new animation of the small world, one can't help but imagine another definition for Pluto. As NASA's New Horizons spacecraft continues its epic journey into the outer solar system, its Kuiper Belt target is becoming brighter and more defined. Seen through the mission's Long Range Reconnaissance Imager (LORRI) camera, this new set of observations clearly shows Pluto and its biggest moon Charon locked in a tight orbital dance separated by only 11,200 miles. (Compared with the Earth-moon orbital separation of around 240,000 miles, you can see how compact the Pluto-Charon system really is.) Both bodies are shown to be orbiting a common point — the "barycenter" is located well above Pluto's surface prompting a new debate on whether or not Pluto and Charon should be redefined as a "binary planet".

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Admit it. (4, Funny)

Anonymous Coward | about 3 months ago | (#47634033)

You're just trying to troll Neil Tyson for the hilarity that ensues.

Re:Admit it. (2)

Anonymous Coward | about 3 months ago | (#47634093)

And xkcd, and a Psych movie if there ever is one. (You can't entirely hate a TV show where "You heard about Pluto?" is used as a pick-up line.)

Re:Admit it. (0)

Anonymous Coward | about 3 months ago | (#47637351)

I've heard it both ways.

Re:Admit it. (1)

frovingslosh (582462) | about 3 months ago | (#47634391)

Agreed. My first thought was that this article is just trying to bait Neil deGrasse Galactus into another fight.

Re:Admit it. (0)

Anonymous Coward | about 3 months ago | (#47636391)

If we call Pluto and Charon a "binary planet" then we have to call every pair of asteroids that orbit each other a "binary planet". This is just another attempt by the backward luddites who can't let go of the fact that Pluto was NEVER a real planet to falsely make it out to be something grander than it really is.

Obligatory JC (1)

DexterIsADog (2954149) | about 3 months ago | (#47636733)

"They invented a reason,
That's why it stings,
They don't think that you matter,
Because you don't have pretty rings."
-Jonathan Coulton

Pluto's a dog. what's Goofy? (5, Informative)

turkeydance (1266624) | about 3 months ago | (#47634035)

seriously....call Pluto what it is...ClickBait.

Re:Pluto's a dog. what's Goofy? (3, Insightful)

TWX (665546) | about 3 months ago | (#47634059)

Heh. I'm happy for the IAU to take its sweet time on this. In the already small impact that space science has on daily life, the definition of a particular pair of bodies that themselves don't care a whit what people about 35AU is just about completely meaningless.

Re:Pluto's a dog. what's Goofy? (0)

Anonymous Coward | about 3 months ago | (#47634085)

Oh.... Oh.. .Neil is gonna kick your asss.....so bad.....

He's gonna argue and make you seem sooooo stupid!

You are toast dude!

Mass Relay (0)

Anonymous Coward | about 3 months ago | (#47634067)

We should launch an expedition to reactivate the Charon mass relay.

July 2015 (1)

Myria (562655) | about 3 months ago | (#47635883)

Well, Earth has an unmanned expeditionary mission that will take pictures of Charon in July 2015 =^-^=

Outrageous discrimination! (5, Funny)

mi (197448) | about 3 months ago | (#47634075)

The debate as to whether Pluto is a planet or a dwarf planet rumbles

What's with this "dwarf" nonsense — and big planetarism [slashdot.org] ? We demand equal gravity for all planets [thepeoplescube.com] !

Poor Pluto (0)

Anonymous Coward | about 3 months ago | (#47634299)

Can everyone please just LEAVE PLUTO ALONE.

Re:Outrageous discrimination! (1)

Jane Q. Public (1010737) | about 3 months ago | (#47635831)

What's with this "dwarf" nonsense â" and big planetarism? We demand equal gravity for all planets!

Why? We don't grant equal gravity to all arguments. Discrimination! :)

I think we should grant equal comedy to all arguments. They everybody would "lighten up" and have a good time.

Re:Outrageous discrimination! (1)

Jane Q. Public (1010737) | about 3 months ago | (#47635839)

s/They/Then

And we should also grant equal comedy to all planets. Even before Charon was named I voted for "Goofy".

Re:Outrageous discrimination! (1)

Tablizer (95088) | about 3 months ago | (#47636009)

But we need more trickle-down gravity until the sun bursts forth and spreads the wealth to the poor Kuiper ghettos, as the job creating nova the sun could be if not for the strangulating socialist regulation of the speed of light stuck at c.

This is a really fucking stupid "debate". (0, Troll)

Anonymous Coward | about 3 months ago | (#47634077)

I can't believe that this is still an issue. Guess what? IT DOESN'T FUCKING MATTER! This sort of pathetic taxonomic squabble is pointless, and just takes time and attention away from investigating real astronomical phenomenon and making real discoveries.

It's like those people who claim that JavaScript is a good programming language. There's nothing to debate. JavaScript is total, indisputable shit. It's a pointless argument to get into, because those claiming that JavaScript is good have already lost.

Astronomers and other scientists, please focus on furthering our knowledge of the universe. Don't waste time with stupid arguments over irrelevant issues like this.

Re:This is a really fucking stupid "debate". (0)

Anonymous Coward | about 3 months ago | (#47634403)

Maybe YOU shouldn't waste YOUR time posting such drivel...

Re:This is a really fucking stupid "debate". (0)

Anonymous Coward | about 3 months ago | (#47634771)

We waste more time closing threads that are contaminated with this kind of shit, so he actually does raise a valid point. You, on the other hand, do not.

Re:This is a really fucking stupid "debate". (1)

ihtoit (3393327) | about 3 months ago | (#47636307)

pedant point: Javascript isn't a programming language, the clue is in the name: it's a SCRIPTING language.

Re:This is a really fucking stupid "debate". (1)

gnupun (752725) | about 3 months ago | (#47636831)

Diameter, in km

Mercury ... 4,880
Venus ..... 12,104
Earth ..... 12,756
Mars ...... 6,794
Jupiter ... 142,984
Saturn ... 120,536
Uranus ... 51,118
Neptune ... 49,532
Pluto ....... 2,222

Pluto's diameter is half the diameter of Mercury. Should we also consider Mercury a dwarf planet? Can the Earth be considered to be in the same league as Jupiter/Saturn as they have 10 times the diameter of Earth?

Re:This is a really fucking stupid "debate". (1)

kasperd (592156) | about 3 months ago | (#47637507)

Can the Earth be considered to be in the same league as Jupiter/Saturn

They are not considered to be in the same league. The classes are: Gas giants, terrestrial planets, dwarf planets.

Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634099)

The Earth-Moon barycenter is very nearly outside of Earth itself (it's about 0.75 Earth radii from Earth's center), so let's not get too high on our horses...

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634117)

Well, if these Jupitarians have their way, Earth will be reclassified as a dwarf planet any day now.

Re:Self-awareness (4, Insightful)

Smauler (915644) | about 3 months ago | (#47636581)

Interestingly, Jupiter is the only planet which has it's barycenter with the sun outside of the sun.

The definition of whether something orbits something else, or whether it is a binary system is pretty arbitrary. It would be nice and neat if we could say that if the barycenter is inside the larger body, the smaller body is orbiting the larger, but that would mean that Jupiter would not be orbiting the sun.

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634379)

75-percent is not what I'd call "very nearly"

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634499)

In that case, can I have 75% of all your money?

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634817)

How about you drink 75% of a 40 gallon drum of Hydrochloric acid?

Re:Self-awareness (1)

khallow (566160) | about 3 months ago | (#47634941)

I wouldn't mind having what's left over from "very nearly" a billion dollars.

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634971)

In that case, can I have 75% of all your money?

Can I have all but 75% of yours? No one said that 75% wasn't significant. We said that it wasn't "nearly all". If it was "nearly all", then you'd be happy enough to spend the remainder on something.

Re:Self-awareness (1)

ihtoit (3393327) | about 3 months ago | (#47636313)

why yes, you can have a quarter of a penny, since that's all I have.

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634905)

Give it a few million years and it will be.

Re:Self-awareness (2)

Noah Haders (3621429) | about 3 months ago | (#47634645)

the best question:

The moon is currently 239,000 miles away, and the barycenter is at 0.75 Earth radii from Earth's center. If the barycenter was at the earth's surface, how close would the moon be?

For the purpose of this calculation assume the earth is a uniform sphere with a mass of 5.97x10^24 kg and a diameter of the earth is 7,900 miles, and the moon is a uniform sphere with a mass of 0.0123 earths and a diameter of 2,160 miles.

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634819)

You are just trying to get /. to do your astro homework for you...

Re:Self-awareness (1)

bondsbw (888959) | about 3 months ago | (#47634849)

320,000 miles

Re:Self-awareness (2)

bondsbw (888959) | about 3 months ago | (#47634883)

BTW, I actually did the full calculations and accounted for the radius of earth/moon in the distance. But according to the equation for calculating barycentric coordinates [wikipedia.org] , the distance of the barycenter from the center of the primary is linearly proportional to the distance of the centers of mass of the two bodies... so a pretty close estimate would have been (1 / 0.75) * 239,000 miles.

Re:Self-awareness (1)

Noah Haders (3621429) | about 3 months ago | (#47635861)

huh I had assumed that the barycenter would move to the surface as the moon got closer, but thinking about it more I see that you're right it would need to move further away.

a couple Qs if you don't mind, because you obv know a lot about this. so I guess if the barycenter is not in the middle of earth, then the earth wobbles as the moon goes around. Is this what causes tides, it's essentially the sloshing of the ocean as the earth wobbles? I always knew that "the moon causes tides", but I never understood the mechanism.

I guess a second question would be, is there a certain distance at which the moon would escape earth's gravity? I wonder what it is, esp compared to the current distance away? would it be 2x, or 10% or 10x?

greatly appreciate your thoughts, I don't know much about this.

Re:Self-awareness (1)

bondsbw (888959) | about 3 months ago | (#47636259)

a couple Qs if you don't mind, because you obv know a lot about this.

I'm just a guy who was interested enough to Google and throw together some calculations.

so I guess if the barycenter is not in the middle of earth, then the earth wobbles as the moon goes around. Is this what causes tides, it's essentially the sloshing of the ocean as the earth wobbles? I always knew that "the moon causes tides", but I never understood the mechanism.

The gravitational forces between the earth and moon are major components of tides. However the barycenter doesn't seem to contribute directly. Moving the earth and moon farther apart (and thus moving the barycenter further away from the center of the earth) actually causes the tides to become weaker. This actually happens regularly as the moon gets closer and then farther from the earth in its orbit (the moon's orbit is not perfectly circular, but slightly elliptical). When the moon is at its closest, the tides are barely higher, and at its furthest the tides are barely lower.

I guess a second question would be, is there a certain distance at which the moon would escape earth's gravity? I wonder what it is, esp compared to the current distance away? would it be 2x, or 10% or 10x?

Gravity accelerates two objects toward one another, based on their mass and their distance. It works the same whether the two objects are initially moving toward each other or away from each other (away from each other, we usually call "decelerating", but there's no difference in the math).

Escape [wikipedia.org] technically occurs when the two objects are moving away from each other, but the deceleration due to gravity will never be enough to overcome their initial velocity at their initial distance from each other. Gravity diminishes as the objects move farther apart, which results in less deceleration over time. In the case of escape, the velocity will never reach zero.

The answer is "yes"... assuming the moon magically appeared at that new farther distance but traveling at the same velocity as it is currently. According to the Wikipedia link on escape velocity:

The escape velocity at a given height is (square root of 2) times the speed in a circular orbit at the same height

Also, the orbital velocity of an object decreases as its distance increases. So increasing the distance of the moon would decrease how fast it would need to be going to stay in orbit.

But remember that the orbital distance suddenly increased but the orbital velocity did not change...

Let's say the moon is orbiting at distance R with orbital velocity V. Thus, all we need to do is figure out at what new distance R2 the new orbital velocity V2 = V * (1 / square root of 2).

This page contains the formula we need. [wikipedia.org] Solving for r, r is proportional to 1/(v^2). So R2 is proportional to 1 / (V2^2), and substituting the equation above we find that R2 is proportional to 2 / (V^2), which equals 2 * (1/V^2), which equals 2 * R. R2 = 2*R.

Thus the answer is "2 times the original orbital distance, 478,000 miles".

Re:Self-awareness (1)

Noah Haders (3621429) | about 3 months ago | (#47637107)

thanks you're cool! I hope the moon never slows down to the point it crashes into earth. that would suck!

Re:Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47637399)

It won't crash into Earth. The moon is ever so slowly leaving us.

You can read more in this article from the BBC [bbc.co.uk] .

Re:Self-awareness (1)

bondsbw (888959) | about 3 months ago | (#47637751)

In retrospect I don't like how I phrased this:

Thus, all we need to do is figure out at what new distance R2 the new orbital velocity V2 = V * (1 / square root of 2).

Change it to the following:

Thus, all we need to do is figure out at what new distance R2 the original orbital velocity V = V2 * (square root of 2), where V2 is the velocity of a circular orbit at distance R2.

Re:Self-awareness (1)

Smauler (915644) | about 3 months ago | (#47636589)

if the barycenter is not in the middle of earth, then the earth wobbles as the moon goes around.

The barycenter for any two objects is never the middle of either. It's always somewhere on a line directly between the two centres of mass. Every individual satellite that humanity has launched makes the earth wobble a little bit (albeit a miniscule amount).

Re: Self-awareness (0)

Anonymous Coward | about 3 months ago | (#47634689)

The barycenter of the Jupiter-Sun binary is above the surface of the sun.

Re:Self-awareness (1)

bondsbw (888959) | about 3 months ago | (#47634803)

Defining it based on barycenter will lead to curious outcomes. What if the barycenter moves into and out from the planet (such as with multiple moons)?

And what if Pluto had a second moon, equal in mass and distance as Charon but always on the exact opposite side (L3)? The barycenter would be at the center of Pluto, but why does this change cause Pluto to become a "real" planet?

Questions like this really reveal the definitions. (1)

robbak (775424) | about 3 months ago | (#47636331)

The answer is simple - that Lagrange point is not stable, so the moon would not remain there. Each moon would be pulled from that point by the other's gravity, until they either collide or one or both items are thrown from their orbits.

So as a planet cannot have two moons that orbit opposite each other, the concept of a binary planet with a definition based on the location of its barycenter is valid. But we'd first want to see one - Pluto/Charon is a poor example, as Pluto is considerably larger and heavier than Charon, so 'Planet/moon system' defines it better. If we start to find real binary planet systems outside of our solar system and stat characterizing them, then we will be able to know what sorts of systems happen and how they form, and maybe then we will find that Pluto/Charon belongs as an outlier there. But that's for a future time.

Re:Questions like this really reveal the definitio (1)

bondsbw (888959) | about 3 months ago | (#47637627)

Agreed, that one is a bit far fetched. It's a many-body problem and all it takes is a bit of eccentricity or pull from other moons, planets, and the sun to destabilize.

But back to the first question, what if the barycenter moves in and out of the planet due to multiple moons? This would be akin to the solar system [youtube.com] , where the barycenter moves in and out of the sun. I don't know if we could easily call it a ternary planet, quaternary planet, etc.

I think I prefer Isaac Asimov's tug-of-war definition [wikipedia.org] of a binary planet. It would be considered a binary planet if the smaller body has a concave orbit around the sun; in other words, the two are both primarily orbiting the sun and just happen to be close to each other. This would, however, define the earth/moon system as a binary planet and Pluto/Charon would be a planet/moon.

Re:Questions like this really reveal the definitio (1)

bondsbw (888959) | about 3 months ago | (#47637703)

Another reason I don't care for the barycentric approach is because it depends so highly on the radius of the larger body. What if the barycenter of the moon were right above the surface but well within the atmosphere? What about a gas giant where the definition of the radius is a bit fuzzier?

Re:Self-awareness (1)

Will.Woodhull (1038600) | about 3 months ago | (#47636011)

The Earth-Moon barycenter is very nearly outside of Earth itself (it's about 0.75 Earth radii from Earth's center), so let's not get too high on our horses...

And the Earth - Moon should be classified as a binary planet. They are in such an intimate dancing orbit with each other that neither one can be adequately described without refering to the other.

This is more than a semantic squabble. Any exoplanet that is likely to support life as we know it must not only be in the Goldilocks zone, it must also have a companion close enough to create tides (and tide pools, and generally act as a celestial stirring rod).

Re:Self-awareness (1)

russotto (537200) | about 3 months ago | (#47637141)

The Earth-Moon barycenter is very nearly outside of Earth itself (it's about 0.75 Earth radii from Earth's center), so let's not get too high on our horses...

That's no moon! (Ask David Weber)

Binary yes, planet no. (4, Insightful)

Henriok (6762) | about 3 months ago | (#47634121)

The arguments for demoting Pluto from its planetary status still holds. And hardly anyone objects to Pluto and Charon together as a binary system. But this "new" insight does not promote Pluto/Charon to planetary status. Binary dwarf planet, binary kuiper belt object, binary plutoid. Absolutely. Binary planet? No.

Re:Binary yes, planet no. (0)

Anonymous Coward | about 3 months ago | (#47634521)

How about binary planetoid?

Re:Binary yes, planet no. (3, Insightful)

jonfr (888673) | about 3 months ago | (#47634895)

Anything that is a sphere and orbits a star is a planet. Asteroids don't have sphere shape. Same goes for comets. The reason for the name "dwarf planets" is that of naming issue. There are more than 100 planet object out there, most of them smaller than planet Mercury.

Haumea is a planet, but is minor elongated due it's rapid orbital period.

http://en.wikipedia.org/wiki/H... [wikipedia.org]

List of other dwarf planets.

http://solarsystem.nasa.gov/pl... [nasa.gov]

Then there is a chance of Earth size planets (both above and below in size and mass) in the outer region of our solar system that have not yet been discovered. At least there are clues about them today, even if they have so far not yet been found. It is my guess they are going to be found, given time and advances in technology that allows for better detection of outer orbital planets in our solar system.

http://www.space.com/7728-eart... [space.com]
http://www.theguardian.com/sci... [theguardian.com]

There is a lot out there that we don't have no clue about and there are discoveries to be made (if the funding holds).

Re:Binary yes, planet no. (0)

Anonymous Coward | about 3 months ago | (#47635425)

The Earth is not a sphere, it only approximates one.

Re:Binary yes, planet no. (1)

Mal-2 (675116) | about 3 months ago | (#47635679)

Anything that is a sphere and orbits a star is a planet. Asteroids don't have sphere shape. Same goes for comets.

Ceres and Vesta are nearly spherical, yet are asteroids. Do they get counted as planets too? (They used to be.)

You're right that the definition was tailored to keep the number of defined "planets" within reason. There was no way to include Pluto in this category and NOT include Eris, Haumea, Makemake, etc., so the definition was tailored to exclude them. It also happens to exclude Ceres and Vesta, though it wouldn't be a huge problem if they were considered planets (as they are the only two members of their class).

Re:Binary yes, planet no. (1)

Anonymous Coward | about 3 months ago | (#47636005)

Ceres is a dwarf planet. Same reasons as Pluto.

Re:Binary yes, planet no. (2)

Jonny Midnight (3779763) | about 3 months ago | (#47636273)

Sorry, but wrong. One of the qualifications to be named as a planet is that the object has cleared its orbit, something Pluto has not done.

Re:Binary yes, planet no. (1)

ihtoit (3393327) | about 3 months ago | (#47636323)

neither has Jupiter. Zing.

Re:Binary yes, planet no. (1)

Urkki (668283) | about 3 months ago | (#47636623)

neither has Jupiter. Zing.

"Cleared its orbit" means, the planet controls everything which shares or crosses orbit with it. This may mean the usual moons, but also oribtal resonance (such as the Pluto-Neptune resonance) and minor bodies oribiting the Lagrange points of the planet (Trojans at L4/L5) instead of the planet itself like the usual moons.

Re:Binary yes, planet no. (0)

Anonymous Coward | about 3 months ago | (#47636691)

Wahtcha talking about Willis? Jupiter has cleared it's orbit and petty much every other planet's orbit as well.

Re:Binary yes, planet no. (1)

ihtoit (3393327) | about 3 months ago | (#47636321)

I think the IAU new definition of a planet includes the condition that it has cleared its orbital track of any other significant debris. Pluto hasn't, it has at least seven satellites and there are many other unconnected bodies sharing the same orbit (last I heard at least twelve, of significant size, at various and seemingly random angular separations)... ironically, this would disqualify Jupiter as well, since it is preceded and followed in its orbit by two clouds of debris (Trojan asteroids) which are located at or near the Lagrange points.

Re:Binary yes, planet no. (0)

Anonymous Coward | about 3 months ago | (#47636151)

Calling Pluto/Charon a binary planetoid should be enough for everybody.

Pluto is a Planet (1, Insightful)

sexconker (1179573) | about 3 months ago | (#47634127)

Pluto is a planet. The definition of a planet is arbitrary, and always will be.
Trying to forcefully change the definition after it's already in use is fucking retarded and does nothing but cause confusion.

For other instances of dipshits trying to hijack language and make it worse, see "non-flammable" and the dipshits who insist that a kilobyte is 1000 bytes.

Re:Pluto is a Planet (-1, Troll)

retchdog (1319261) | about 3 months ago | (#47634177)

christ you're an unusually stupid fuck.

anyway, please tell me what's wrong with nonflammable. this ought to be entertaining.

Re:Pluto is a Planet (1)

sexconker (1179573) | about 2 months ago | (#47638379)

"Inflammable" means shit is capable of bursting into flames.
"Non-inflammable" means it isn't (easily).
"Nonflammable" was created by an asshat who wanted to remove confusion (which didn't exist).
"Flammable" was then created to be the opposite of the new fake opposite.

"Inflammable" is derived from the Latin inflammare, which means able to be set on fire. This is the correct usage.
"Nonflammable" is derived from "non" + "flammare", meaning to set on fire, + "able". This is completely fucking incorrect usage.

Re:Pluto is a Planet (0)

Anonymous Coward | about 3 months ago | (#47634203)

"I think I know what the A in NASA stands for." Jerry Smith

Re:Pluto is a Planet (1)

The Evil Atheist (2484676) | about 3 months ago | (#47635239)

There was no definition of planet, that was the point. Dictionary definitions don't count, because the dictionary definition would include asteroids, comets, the sun and moons. If you want those included in the planet category, go study Indo-European astrology.

Re:Pluto is a Planet (1)

wonkey_monkey (2592601) | about 3 months ago | (#47635285)

Pluto is a planet. The definition of a planet is arbitrary, and always will be.

What makes your arbitrary definition of "planet" - one that allows you to declare without qualification that it is a planet - better than the IAU's?

Trying to forcefully change the definition after it's already in use is fucking retarded and does nothing but cause confusion.

Not when the old definition is itself revealed to be "fucking retarded" (technical term, is that?) and causes more confusion once more data becomes available.

see "non-flammable"

Did you mean "inflammable"?

and the dipshits who insist that a kilobyte is 1000 bytes.

What, like the dipshits at the the International Organization for Standardization? Just because you don't like it, doesn't make everyone else unquestionably wrong.

Re:Pluto is a Planet (1)

retchdog (1319261) | about 3 months ago | (#47635533)

I'm totally baffled about the "non-flammable" thing. I think sex_conker just likes being confused because the alternative is too difficult for him.

Re:Pluto is a Planet (1)

Beck_Neard (3612467) | about 3 months ago | (#47635401)

If you want to call Pluto a planet, you'll have to call Eris, Haumea, Makemake, Ceres, and a whole bunch of others planets too.

Keep in mind that Ceres is spherical, orbits a star, and was known for 200 years but was NOT considered a planet during this time.

Language can be arbitrary, sure. But why insist on it being self-contradictory?

What debate? (5, Informative)

glwtta (532858) | about 3 months ago | (#47634193)

Planet and Dwarf Planet are arbitrary labels defined by the IAU.

How can you "debate" about that?

Re:What debate? (2)

khallow (566160) | about 3 months ago | (#47634877)

The debate comes in that those arbitrary labels can be changed to other arbitrary labels.

Re:What debate? (1)

glwtta (532858) | about 3 months ago | (#47635467)

That's what 'arbitrary' means.

Re:What debate? (1)

retchdog (1319261) | about 3 months ago | (#47635501)

I know! It's the best kind of debate: having no substantial meaning at all, it can last forever as an excuse for people to insult and trump one another. It's a perfect Slashdot article; we need more of these.

Re:What debate? (1)

Urkki (668283) | about 3 months ago | (#47636649)

Planet and Dwarf Planet are arbitrary labels defined by the IAU.
How can you "debate" about that?

Well, they're not really arbitrary. There are at least three points you can argue about:

1. Argue to change the definition (actual written words), which determines which is which and what isn't either.

2. Argue about interpretation of the defintion. Though, if this succeeds, then it makes the definition ambiguous, and the classification of border cases does become arbitrary.

3. Argue about the chosen terms "planet" and "dwarf planet". For example I'm personally not too happy having "dwarf planets" which are not a subclass of "planets", it's a bit unintuitive to me.

This is pretty damn silly (3, Interesting)

glwtta (532858) | about 3 months ago | (#47634225)

This mission will put a new spotlight on Pluto and its âoedwarf planetâ status, potentially highlighting its current classification as a woefully inadequate description of such a dynamic and interesting binary system.

Ok, so it's a "binary dwarf planet" - can we tone down the prose now?

Sure, why not (0)

Anonymous Coward | about 3 months ago | (#47634229)

I have binary testicles!

Re:Sure, why not (0)

Anonymous Coward | about 3 months ago | (#47634925)

on your chin

No... absolutely (0)

Anonymous Coward | about 3 months ago | (#47634245)

Pluto is a dog planet.

So the Sun/Jupiter system as well? (2)

philotag (557239) | about 3 months ago | (#47634347)

The barycenter of the Sun and Jupiter is above the surface of the sun, does that mean we'd have to reclassify our solar system as a binary star system now? http://spaceplace.nasa.gov/bar... [nasa.gov]

Re:So the Sun/Jupiter system as well? (1, Troll)

jklovanc (1603149) | about 3 months ago | (#47634815)

No, because Jupiter is not a star. It is the same reason that Pluto/Charon is not a binary planet as neither of them is a planet.

Re:So the Sun/Jupiter system as well? (0)

Anonymous Coward | about 3 months ago | (#47634965)

Not until Jupiter gets a few hundred quin-trillion more units of mass. (where units of mass are greater than tons, but less than its own).

Then it'll be able to sustain fusion and count as a star.

Still askew (1)

Anonymous Coward | about 3 months ago | (#47634505)

Unless Pluto (and Charon) shifted orbit into the planetary plane, nothing has changed and any desire to call it a planet is just sentimentality.

I guess now we know... (0)

Anonymous Coward | about 3 months ago | (#47634507)

what the 'A' in NASA stands for...

pluto doesn't care (1)

TheRecklessWanderer (929556) | about 3 months ago | (#47634537)

Pluto doesn't care what you call it. It's going to be around when you are dust in the wind. Oh and I don't care either.

Re:pluto doesn't care (0)

Anonymous Coward | about 3 months ago | (#47634773)

Well, then I'll teach Pluto not to care.

By blowing it the fuck up.

Re:pluto doesn't care (1)

confused one (671304) | about 3 months ago | (#47634929)

Great. First you blow up Pluto, just to prove a point... then pieces of it come raining inward toward our planet. Next thing we know, we're going the way of the dinosaurs because you had to show off.

Re:pluto doesn't care (1)

ihtoit (3393327) | about 3 months ago | (#47636339)

it's all fun and games until someone blows up a planet.

miles? (1)

umghhh (965931) | about 3 months ago | (#47634647)

what is that? Why not furlongs or Manhattans?

There's only one Binary Planet here -- Earth/Luna (-1)

Anonymous Coward | about 3 months ago | (#47634687)

Earth/Luna is a binary planet by the criteria. Most significantly, Luna's orbit is never convex with respect to the Sun.

Re:There's only one Binary Planet here -- Earth/Lu (2)

khallow (566160) | about 3 months ago | (#47634901)

Earth/Luna is a binary planet by the criteria.

It's not. The center of gravity [infoplease.com] is under Earth's surface.

Most significantly, Luna's orbit is never convex with respect to the Sun.

The Moon's orbit is convex [nus.edu.sg] .

No we can't (1)

Mister Liberty (769145) | about 3 months ago | (#47634993)

No phone lines yet. Sorry.

NASA says: (0)

Anonymous Coward | about 3 months ago | (#47635175)

" Pluto and Charon are sometimes referred to as a double dwarf planet system."

Betteridge says (1)

Livius (318358) | about 3 months ago | (#47635457)

No.

Self determination (1)

rossdee (243626) | about 3 months ago | (#47635487)

I suppor tthe right of the people of Pluto to decide their own destiny, and not be ruled by any arbitrary group of people on some other planet.
Freedom for the Plutocrats

Who will care... (0)

Anonymous Coward | about 3 months ago | (#47635517)

Out of all the people who bitch and complain about Pluto, how many will even pretend to care when New Horizons gets there next year?

Pluto is not a planet, nor is the Pluto-Charon system a double planet. Being a cluster of Kuiper belt objects, the Pluto system is a Kuiper Cluster.

AHEM... (2)

Unknown74 (3041957) | about 3 months ago | (#47635519)

Uh, folks, Pluto actually has FOUR moons... Charon: Discovered in 1978, this small moon is almost half the size of Pluto. ... Nix and Hydra: These small moons were found in 2005 by a Hubble Space Telescope team studying the Pluto system. Kerberos: Discovered in 2011, this tiny moon is located between the orbits of Nix and Hydra. ...and it just keeps on thumbing it nose at the dwarfists, and now, the binarists. But tell me, how is a FIVE body system a BINARY system? Hmmmmm?

OOOps! (4, Informative)

Unknown74 (3041957) | about 3 months ago | (#47635553)

My mistake...Pluto has FIVE moons. Charon: Discovered in 1978, this small moon is almost half the size of Pluto. It is so big Pluto and Charon are sometimes referred to as a double planet system. Nix and Hydra: These small moons were found in 2005 by a Hubble Space Telescope team studying the Pluto system. Kerberos: Discovered in 2011, this tiny moon is located between the orbits of Nix and Hydra. Styx: Discovered in 2012, this little moon was found by a team of scientists search for potential hazards to the New Horizons spacecraft flyby in 2015. may the 'little planet that could' keep right on thumbing it nose at everybody!

Re:OOOps! (2, Funny)

Anonymous Coward | about 3 months ago | (#47636107)

Among the moons of Pluto are... wait, I'll come in again.

F = GM1M2 / R^2 (0)

Anonymous Coward | about 3 months ago | (#47635661)

The earth and moon do the same dance but with a different mass ratio. Students just get pointed off track when the discussion turns from physics to human nomenclature.

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