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NASA's Hubble Discovers Another Moon Around Pluto

CmdrTaco posted more than 2 years ago | from the spinning-round-and-round dept.

NASA 208

thebchuckster writes "Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite – temporarily designated P4 — was uncovered in a Hubble survey searching for rings around the dwarf planet. The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km)."

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That's no .... (-1)

Anonymous Coward | more than 2 years ago | (#36824992)

The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km).

That's no space station! It's to small!

Ha! You thought I was going to say something else, didn't ya?

Re:That's no .... (-1)

Anonymous Coward | more than 2 years ago | (#36825200)

The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km).

That's no space station! It's to small!

Ha! You thought I was going to say something else, didn't ya?

That's not your penis! It's too small! Oh wait you're an Apple fanboi. Nevermind. That's normal for you. Clearly you are the catcher not the pitcher.

Planet (1, Insightful)

Baloroth (2370816) | more than 2 years ago | (#36825006)

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy planet Pluto.

There, FTFY :)

More seriously, when did they find the second and third moons? I honestly don't remember ever hearing about them, last I knew Pluto just had Charon. Must be really out of the loop on this.

Re:Planet (2, Insightful)

adamjcoon (1583361) | more than 2 years ago | (#36825094)

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy rock Pluto.

There.. FTFY ;o)

Re:Planet (3, Interesting)

EvanED (569694) | more than 2 years ago | (#36825138)

Depending on how you count, it may be more accurate to say "rocky ice". By volume, Pluto has more ice than rock. (By mass, it is indeed an icy rock.)

Re:Planet (4, Funny)

Normal Dan (1053064) | more than 2 years ago | (#36825248)

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy rocky thing we call Pluto.

There... FTFY :D

Re:Planet (2)

formfeed (703859) | more than 2 years ago | (#36825798)

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy rocky thing we call Pluto.

There... FTFY :D

Astronomers using the Hubble Space Telescope discovered a fourth dwarf moon orbiting the icy dwarf planet Pluto.

There... FTFY :D :D

-Actually, would it be a dwarf moon, or a dwarf-planet moon? Or -in this case- both?

Re:Planet (2, Insightful)

EvanED (569694) | more than 2 years ago | (#36825112)

If you count Pluto as a planet, do you count Eris as a planet? (It's bigger than Pluto.) What about Sedna? (Smaller, but not by a whole lot.)

Wikipedia says Nix and Hydra were discovered in 2005 (also by the Hubble team, apparently) and named in 2006.

Re:Planet (0)

Anonymous Coward | more than 2 years ago | (#36825250)

There is no clear difference between what is a planet and what is not, that's why all this crazy war is going on. We've had too many casualties on both sides, so I say this: let's toss a coin and let that decide if Pluto is a planet or not. Anything smaller is not a planet, anything bigger is a planet. Problem solved.

Re:Planet (2)

qzjul (944600) | more than 2 years ago | (#36825388)

Well, the current definition of being spherical and clearing its local neighbourhood (and being in orbit of the star, not another planet), is a pretty good one I think anyway.

Re:Planet (2, Insightful)

d3ac0n (715594) | more than 2 years ago | (#36825796)

Not only that, but as a definition it is empirical and not subjective, like the various "size" based definitions are.

Planet: Any body which has all of the following properties:
1. It's mass has compressed it into a spherical shape.
2. It's primary orbit is around a star
3. It has cleared it's orbit of all other bodies that aren't satellites of itself, Lagrange point bodies, or "twin" satellites of similar mass that it stably co-orbits with where the co-orbital point exists outside either body.

Note the last part there. Not everyone includes this. I include it as it not only allows BOTH Pluto and Charon to be counted as planets, but also takes into account any new extra-solar co-orbiters we may discover in the future.

I mean, wouldn't it be embarrassing to leave that last part out, and then down the road discover a "double earth" planet system orbiting another star and not be able to categorize either earth-sized body as a planet?

Now, if you INSIST on having a "planet / proto-planet" dichotomy, I could accept a fourth definitional point:

4. Must have a gravitational force large enough to hold an atmosphere outside of any solar wind stripping influence.

This addition would still include Pluto, although it might exclude Charon as it has no known atmosphere. However it's lack of atmosphere could also be due to the extreme cold and the fact that most of it's ices are water ices, thus largely non-volatile at those temperatures and unable to "gas off" and create an atmosphere.

Lastly, I have also seen some scientists want to include a 5th definitional point:

5. Has a differentiated structure.

Not sure how Pluto and Charon would stack up against that criterion.

Re:Planet (1)

Dyolf Knip (165446) | more than 2 years ago | (#36825998)

> 3. It has cleared it's orbit of all other bodies that aren't satellites of itself, Lagrange point bodies, or "twin" satellites of similar mass that it stably co-orbits with where the co-orbital point exists outside either body.

Wouldn't this definition preclude a Kemplerer Rosette? Sure, they don't occur in nature, and are in fact quite unstable without active stationkeeping, but if you put (to pick a number at random) 5 Earth-sized planets equally spaced in the same orbit, be kinda silly to declare them non-planets as a result.

Re:Planet (1)

d3ac0n (715594) | more than 2 years ago | (#36826160)

You missed the "Stable" part of the definition. Any body not in a stable orbit, regardless of size, would not be considered a "planet".

Yes, it may seem silly, but a randomly wandering body, regardless of size, shouldn't be called a planet. I think "Planetoid" or "dark body" would be more accurate, although we may need to come up with a new word.

However the size alone should not be the definitional point as size-based parameters are constantly subject to revision, and are thus unreliable.

Re:Planet (1)

dkleinsc (563838) | more than 2 years ago | (#36826130)

I include it as it not only allows BOTH Pluto and Charon to be counted as planets, but also takes into account any new extra-solar co-orbiters we may discover in the future.

Except that they haven't in fact cleared their orbit of all other bodies that aren't satellites - with the discovery of the Kuiper Belt, Pluto started looking a lot more like Ceres than it did like Mercury.

Re:Planet (1)

d3ac0n (715594) | more than 2 years ago | (#36826194)

Haven't they? I was under the impression that they orbited near the edge of the Kuiper belt, but that their orbit was actually clear of other Kuiper belt objects.

Re:Planet (1)

kimvette (919543) | more than 2 years ago | (#36826186)

4. Must have a gravitational force large enough to hold an atmosphere outside of any solar wind stripping influence.

On that point, Pluto is more of a planet than Mercury.

Re:Planet (1)

d3ac0n (715594) | more than 2 years ago | (#36826250)

Well, Mercury certainly COULD hold an atmosphere, but it's orbit is so close to Sol that the solar wind strips it.

If Pluto were closer it wouldn't have an atmosphere either. That's why the "outside the solar wind stripping influence" part of the definitional point.

Re:Planet (1)

MozeeToby (1163751) | more than 2 years ago | (#36826332)

Your definition comes very close to having the moon declared a planet. Although at present the barycenter is below the surface of the Earth, the moon is constantly moving away from the Earth. The day will come when, by your definition, the moon will suddenly and instantly be elevated to planet-hood even though nothing obvious has changed.

Not that that makes your definition wrong of course, just pointing it out.

The argument of what is and isn't a planet is older than people realize; Isaac Asimov suggested a system where the body with the largest gravitational influence would determine if something is a planet or not. Titan is influenced by Jupiter 380 times more than it is influenced by the sun, so it is clearly a moon of Jupiter. Interestingly, the moon is influenced by the earth only 0.46 times as much as it is influenced by the sun, making the moon a planet by Asimov's definition.

Re:Planet (1)

MozeeToby (1163751) | more than 2 years ago | (#36825508)

It amounts to people having a holy war over where blue ends and purple begins. It's arbitrary. They needed a definition and it was generally felt that a definition that kept the number of planets to a reasonable number was in everyone's interest. The reason the definition was changed was because modern theory predicts dozens or even hundreds of Pluto-like objects in the outer solar system, which was thought to be an unreasonable number of bodies to be labeled as planets.

IMO, what they should have done was create a super-category 'planets', which would include the 100+ objects in the outer solar system, and at least 3 subcategories (terrestrial, gas, and dwarf) that are more specific. I think there's an argument to be made that Mercury has more in common with Eris than it does with Jupiter for instance, but then I'm not an astronomer.

I bet a German answers this (1)

Hognoxious (631665) | more than 2 years ago | (#36826312)

Anything smaller is not a planet, anything bigger is a planet. Problem solved.

I really hope you aren't a coder on anything that matters.

See, you've left the case where something is exactly the same size as Pluto undefined.

Still, what are the odds of it happening? Can anyone name anything that could be on a dwarflist of things potentially the exact same size as Pluto?

Re:Planet (2)

Cochonou (576531) | more than 2 years ago | (#36825272)

Eris might not be that big after all [space.com] . The first estimation of its size were made according to its mass, but it seems that this dwarf planet could have a higher density than Pluto.

Re:Planet (1)

EvanED (569694) | more than 2 years ago | (#36825580)

Interesting, I didn't know that.

(That being said, I'm not convinced that mass isn't what should be used for the "bigger/smaller" measure in the first place.)

Re:Planet (1)

N0Man74 (1620447) | more than 2 years ago | (#36825764)

That's interesting, but that then brings up another question. Should you qualify what is or isn't a planet based on it's size, or it's mass?

To a real estate agent, size is pretty important, but I would think that mass would be more important to an astronomer.

Re:Planet (1)

d3ac0n (715594) | more than 2 years ago | (#36826396)

i think the sensible answer is "neither".

Whether you base it around "X" size or "X" mass, the problem is that "X" is inherently non-empirical and subject to change, thus inappropriate as a definition.

The only "mass" related definition that would be empirical would be "Mass large enough to compress it into a sphere." It's empirical enough that you can actually chart it.

Combined with other definitional points such as the ones mentioned in my earlier post, you can have a totally empirical definition of a planet that makes sense and prevents us from having an insane number of planets in our system.

Re:Planet (0)

Anonymous Coward | more than 2 years ago | (#36825292)

In which way is little people not people?
How small do a human need to be to not be a human?

Re:Planet (1)

DigiShaman (671371) | more than 2 years ago | (#36825350)

If you have a large object locked in a stable orbit around a star, and it too has a moon; to me that qualifies as a planet. Give Pluto back its former title please.

Re:Planet (5, Informative)

Canazza (1428553) | more than 2 years ago | (#36825420)

Pluto and Charon orbit around a non-fixed barycenter that is actually outside of both Pluto and Charon. Pluto/Charon is really a binary Dwarf Planet with 3 moons. Which, honestly, is fucking awesome.

Re:Planet (2)

Nadaka (224565) | more than 2 years ago | (#36825552)

All orbiting objects orbit around a non-fixed barycenter. The only factors determining if that center is inside or outside one of the planets is the ratio of masses of an object pair, the distance between them and the radius of the more massive object.

Re:Planet (1)

Canazza (1428553) | more than 2 years ago | (#36825658)

I meant inside a fixed object. (IE, the moons Barycenter is inside the Earth, until such time as it floats far enough away in a few millenia)

Re:Planet (4, Insightful)

careysub (976506) | more than 2 years ago | (#36825664)

Pluto and Charon orbit around a non-fixed barycenter that is actually outside of both Pluto and Charon. Pluto/Charon is really a binary Dwarf Planet with 3 moons. Which, honestly, is fucking awesome.

Absolutely! Further more its physical and orbital characteristics clearly associate it with the recently discovered Kuiper Belt Objects. It is should not be viewed as a "pathetic little planet wannabe" but as the King of the KBOs (Eris would be the Queen).

Re:Planet (1)

d3ac0n (715594) | more than 2 years ago | (#36826050)

(Eris would be the Queen)

Don't tell Charon that. She's been hanging with Pluto a long time. Also, she's an icy bitch.

Re:Planet (1)

John Bresnahan (638668) | more than 2 years ago | (#36825452)

If you have a large object locked in a stable orbit around a star, and it too has a moon; to me that qualifies as a planet.

Using this criteria, there are hundreds, if not thousands of such "planets". Wikipedia [wikipedia.org]

Re:Planet (1)

fyngyrz (762201) | more than 2 years ago | (#36825456)

  • If an object exists or existed in the past as a stand-alone fusion reaction, it's a star.
  • If a space-going object was assembled using tools, it's a spacecraft. Otherwise,
  • If an object has its own orbit about its star, and it has enough mass to overcome any other structure it might have had and has pulled itself into a sphere or oblate spheroid, it's a planet.
  • If an object has its own orbit about its star, and cannot pull itself into a sphere or oblate spheroid...
    • then if it's primarily rocky, stony or metallic, it's an asteroid
    • else if it's primarily gassy or icy, it's a comet
  • If an object orbits a planet, it's a moon, irrespective of shape.
  • If an object doesn't orbit a star and isn't under power or in a directed trajectory, it's a rogue [planet, asteroid, comet, spacecraft].

So: Pluto is a planet. Eris and Sedna are both probably planets, but we don't actually know if they have rounded themselves as yet -- they're pretty far out there. So it is possible one or both are asteroids.

Re:Planet (1)

arth1 (260657) | more than 2 years ago | (#36826270)

If an object orbits a planet, it's a moon, irrespective of shape.

So the space station is a moon? And the hammer they dropped up there? And Saturn's rings are moons too?

I would be good with a definition of moon that requires a spherical shape and long-term stable orbits. That would exclude Mars' satellites, which is fine with me. They're just captured asteroids in decaying orbits.

Re:Planet (-1)

Anonymous Coward | more than 2 years ago | (#36825496)

If you count Pluto as a planet, do you count Eris as a planet? (It's bigger than Pluto.)

No because we don't give a shit about that. Now go away.

Re:Planet (1)

Artifakt (700173) | more than 2 years ago | (#36826350)

But if you stop counting Pluto as a planet, and then you discover another Kuiper Belt object that's not only bigger than Eris but as big or bigger than Mercury, do you make it a planet, or do you take Mercury off the list?
          Right now, the IAU definition of planet is deliberately limited to our own solar system, just so it doesn't apply to situations extra-solar astronomers have actually already found, or are very likely to find in the next few years (How do you determine what 'clears an orbit' in a young solar system where there's still lots of small stuff everywhere?). There's still a fair chance we will find something else in our own system that the definition either calls a planet or some sort of ambiguous case (If the albedo is average for an icy rock, then it's not a planet but if there's something darker on the surface, maybe it is...).
          What has usually happened to complex, multi-part, legalistic definitions in the sciences? People tried to define every element on the periodic table as either a reactive element or an inert, 'noble' gas. Was there a move to take Xenon off the noble gas list when someone managed to get it to combine with fluorine under high enough pressures? Biologists had a big checklist for what constituted life - with sub-definitions of eating, excreting, reproducing, etc. When they first found viruses that could only reproduce by hijacking a cells reproductive copying systems, there was debate over whether viruses were truly alive - did anyone float a new, more complex definition of what counted as reproduction and demand that everything now fall squarely on one side or the other of the line they had drawn? Did they redraw the line again for Prions?

Re:Planet (1)

operagost (62405) | more than 2 years ago | (#36825340)

So the current satellite scorecard looks like this:

Smallest planets: Mars, 2; Mercury, 0
Biggest "dwarf" planets: Pluto, 4; Ceres: 0

Re:Planet (0)

Anonymous Coward | more than 2 years ago | (#36825952)

The number of satellites has nothing to do with whether a body is classified as a planet or not.

Re:Planet (1)

tommy2tone (2357022) | more than 2 years ago | (#36825732)

More seriously, when did they find the second and third moons? I honestly don't remember ever hearing about them, last I knew Pluto just had Charon.

2005, Hubble found them.

Pluto's Moons (1)

Bloodwine77 (913355) | more than 2 years ago | (#36825016)

Poor Pluto, they can take away your planetary designation but you will always have your moons!

As for Hubble, I am quite happy with its continued usefulness and success. Hopefully it never loses its funding (at least not until there is a suitable replacement).

Re:Pluto's Moons (1)

Gideon Wells (1412675) | more than 2 years ago | (#36825150)

You know, I used to feel bad for Pluto. Poor, alone out there except for Charon. Then they demoted Pluto and ever since it seems like all Pluto can do is try to bling itself out more and more for attention. Maybe the right decision was made. Between Saturn and its rings, Earth with its fancy smancy life, Uranus and Venus with their hipster rational anomalies... I just don't think we can take another attention seeeker.

Re:Pluto's Moons (3, Insightful)

Ellis D. Tripp (755736) | more than 2 years ago | (#36825280)

Hubble will eventually degrade in performance just as it has in the past. Gyros and batteries wear out, electronics get glitchy, etc.

Unfortunately, when it starts to happen again, there won't be anything we can do about it. Without the shuttle, another service mission is impossible. And with Hubble's successor (JWST) hanging by a fraying budgetary thread, there likely will be no replacing it with an improved telescope, either.

We as a country have given up on science, unless it makes immediate profits for megacorporations or helps the military kill people more efficiently in foreign lands.

Re:Pluto's Moons (4, Insightful)

the gnat (153162) | more than 2 years ago | (#36825498)

Unfortunately, when it starts to happen again, there won't be anything we can do about it. Without the shuttle, another service mission is impossible. And with Hubble's successor (JWST) hanging by a fraying budgetary thread, there likely will be no replacing it with an improved telescope, either.

This has been repeated a number of times, but launching an entirely new Hubble into high orbit (without a shuttle, that is) would be substantially cheaper than maintaining the shuttle program in order to service the existing scope. I hope JWST pulls through, but I don't think NASA should get a blank check from the taxpayers.

We as a country have given up on science, unless it makes immediate profits for megacorporations or helps the military kill people more efficiently in foreign lands.

I'm not a fan of our budget priorities for the last decade, but I can understand why Congress is viewing JWST skeptically. The telescope isn't even supposed to launch until 2017 at the earliest and it's already billions of dollars over budget. Sure, this is a fraction of what we're flushing down the toilet in futile wars, but we're already stuck in those, and they're much more difficult to pull out of than a project that's still in the planning stages.

Except for servicing Hubble - a dubious justification - the shuttle was a terribly inefficient use of money for the science that came out of the program. As far as scientific funding in general is concerned, NASA continues to do great work with remote probes and will be sending another rover to Mars soon. The NIH and NSF managed to avoid major funding cuts in a year when most federal agencies got hit hard, and the DOE Office of Science, which was slated for a huge cut, also survived mostly intact. Speaking as a scientist involved with many of these agencies, I'm thrilled with the outcome.

Re:Pluto's Moons (1)

vlm (69642) | more than 2 years ago | (#36825560)

We as a country have given up on science, unless it makes immediate profits for megacorporations

I'm not thinking Hubble was manufactured by schoolchildren or launched by a volunteer group.

That's the mystifying part. You'd think there's just as much room for corruption in the aerospace contracting field as the banking field, but apparently fraud is easier in the banking industry. Since they (as in the big bankers) are not going to let us fix the banking system, the solution would seem to be, make the aerospace industry as corrupt, or more corrupt, than the banking industry.

I'm sure we could set up some system of multiple tiers of commissioned sales people, maybe a derivatives market, a couple corrupt safety ratings companies... If it doesn't work, 1) banking system doesn't either and no one cares 2) "space is hard" apologists.

Re:Pluto's Moons (1)

Grishnakh (216268) | more than 2 years ago | (#36825606)

We as a country have given up on science, unless it makes immediate profits for megacorporations or helps the military kill people more efficiently in foreign lands.

What's more disappointing is that the other industrialized countries haven't taken this torch and run with it. Europe has at least 50% more population than the USA, and a larger economy (and it appears, stronger, despite the problems in Greece). While obviously no one country there can match the US in size and economic power, combined they easily can. They really should be doing more in the scientific realm. Their work in high-energy physics is good, but I don't see them doing that much in space.

Everyone else needs to stop looking to the USA to be the leader and do everything for them, and start doing things themselves. The USA is falling apart due to lack of education, apathy, and above all, extreme corruption. All these other nations need to stop whining about that, and start working to establish a new world order, to borrow a phrase, where the USA is not the sole superpower, but where groups of other nations lead, both economically and morally.

Re:Pluto's Moons (1)

tverbeek (457094) | more than 2 years ago | (#36825618)

"Gyros and batteries wear out"

That certainly explains the discomfort I felt last night after eating a week-old Greek pita sandwich and a couple of AAs I found in my desk drawer.

That's not a moon... (0)

Anonymous Coward | more than 2 years ago | (#36825034)

That's a Mass Relay.

Pluto it not a planet (1)

VincenzoRomano (881055) | more than 2 years ago | (#36825044)

it's just an icy something.

Re:Pluto it not a planet (1)

JabberWokky (19442) | more than 2 years ago | (#36825160)

Actually, it is (along with Eris, Makemake, Ceres, Quaoar and many others, mostly with technical identifiers) properly termed a dwarf planet. Not a planet, a dwarf planet. So the article is actually quite correct.

Obligatory (0)

Anonymous Coward | more than 2 years ago | (#36825086)

"That's no moon....."

Let's lobby for a new standard (5, Funny)

Anonymous Coward | more than 2 years ago | (#36825088)

Four moons means it gets to be called a planet.

Re:Let's lobby for a new standard (1)

alta (1263) | more than 2 years ago | (#36825214)

not sure who modded you down, but I was thinking the same thing.

I spent my entire childhood thinking pluto was a planet. To me it will always be a planet. Even my 9yo was originally taught it was a planet. Where's the love? Seriously, after 76 years, NOW you're going to choose to call it a 'dwarf planet'? I think not.

If you have enough gravity to have something orbiting you, then you get to be a planet.

There's got to be an 'in soviet russia' joke here, I'm just not sure what it is yet.

Re:Let's lobby for a new standard (1)

AlecC (512609) | more than 2 years ago | (#36825290)

In which case you must add Eris, Makemake, Ceres, Quaoar, Vesta and probably others to the list. Vesta even has a man-made satellite orbiting it now. The list of planets will be open and ever extending, and there will be an insoluble argument about where you draw the line between planets and asteroids,

Re:Let's lobby for a new standard (1)

alta (1263) | more than 2 years ago | (#36825612)

You make it too complicated. Here are the criteria:
1. It is not on fire (sun)
2. It has something not man made orbiting it.
3. It was discovered before 1931
4. It's larger than the smallest listed in #2 (this will pick up mercury which otherwise would have failed my tests.

Or, lets make it even easier.
A planet is any one of MVEMJSUNP...

Re:Let's lobby for a new standard (1)

vlm (69642) | more than 2 years ago | (#36825656)

The list of planets will be open and ever extending,

Not likely. Eventually its all found. Like arguing we must redefine australia as an island, or else we'll have trillions of "continents" in the ocean. Eventually you find them all. For example, we are not likely to find any new planets within the orbit of Mars.

and there will be an insoluble argument about where you draw the line between planets and asteroids,

Easy Peasy. Does it crush itself under its own mass to an almost spherical shape? Theoretical compression stress at the core due to gravity exceeds stress limit of the rock? Then its a planet. An asteroid is a smaller lump of rock that isn't heavy enough to "round" itself under its own mass.

In an era where every kid gets a participation trophy I'm mystified at the hate toward Pluto, what does it hurt if it gets socially promoted to planet grade?

Re:Let's lobby for a new standard (1)

macson_g (1551397) | more than 2 years ago | (#36825602)

If you have enough gravity to have something orbiting you, then you get to be a planet.

So my wife's middle name should be 'Planet' then...

Re:Let's lobby for a new standard (0)

vlm (69642) | more than 2 years ago | (#36825760)

Uranus's moons joke arriving in 5... 4... 3... 2... 1... "I always knew goatse was a scientific curiosity, but thought it was a biological one, not astronomical."

(was that any good?)

Re:Let's lobby for a new standard (1)

EvanED (569694) | more than 2 years ago | (#36825744)

My own feeling as a non-astronomer but who has done a small amount of reading on the Pluto classification is that it is very difficult to come up with a definition of "planet" that does all of the following:
1. Includes Pluto
2. Excludes enough stuff to start giving our system well over a dozen planets
3. Doesn't include some arbitrary measurement that is pretty much specifically designed to do #1 and #2. (What I mean by "arbitrary" is something like "is at least 2000km in radius where if I say "why did you pick 2000?" you don't have an answer other than "well, it was a nice round number". Something like "has enough mass to become a near-sphere" has a physical meaning, and I'm okay with.)

Pluto has enough really weird characteristics (as compared to the other 8, or even as compared to Eris) that it seems to me that a separate category is pretty well-merited.

Re:Let's lobby for a new standard (2)

sconeu (64226) | more than 2 years ago | (#36826238)

NOW you're going to choose to call it a 'dwarf planet'?

Please. Pluto prefers the term "Gravitationally Challenged Planet"

Re:Let's lobby for a new standard (1)

Grishnakh (216268) | more than 2 years ago | (#36825644)

There's tons of tiny asteroids with their own, even smaller, moons. Are we going to call those planets too? Do we need to have schoolchildren remember the names of hundreds of moon-bearing asteroids, I mean planets?

Re:Let's lobby for a new standard (1)

vlm (69642) | more than 2 years ago | (#36825814)

Do we need to have schoolchildren remember the names of hundreds of moon-bearing asteroids, I mean planets?

We're already at 53 planets. Whats one more?

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

The good news is the names are pretty easy. Whats the planet orbiting between Kepler-11 B and Kepler-11 D? Oh let me guess it's Kepler-11 C.

Re:Let's lobby for a new standard (1)

mrchaotica (681592) | more than 2 years ago | (#36826166)

The good news is the names are pretty easy. Whats the planet orbiting between Kepler-11 B and Kepler-11 D? Oh let me guess it's Kepler-11 C.

What happens when they find a new planet between them? Rename everything farther away, leading to questions like "did you mean the object named Kepler-11 C before [date], or the object named that after [date]?"

Interstate exit numbers suffered this same issue every time a new exit was built, by the way, which is why they all got renumbered after the corresponding mile markers a decade or so ago.

Re:Let's lobby for a new standard (1)

arth1 (260657) | more than 2 years ago | (#36826038)

Let's be consistent:
Only satellites that have been pulled into a spherical shape by their mass and have cleared their orbit around the planet should be called "moons". The rest are obviously "dwarf moons".

As for what we should call a satellite that orbits a satellite, I vote for "Zappa".

Re:Let's lobby for a new standard (1)

camperdave (969942) | more than 2 years ago | (#36826402)

So where does that leave Mars? Phobos and Diemos ain't exactly the roundest rocks in the cosmos.

Funding (1)

ISoldat53 (977164) | more than 2 years ago | (#36825782)

In this time of austerity the funding for the agency that supported de-listing Pluto as a planet probably needs a second look.

That's no moon.. (0)

Anonymous Coward | more than 2 years ago | (#36825136)

Its a space station

Queue the Pluto vs. Planet diatribes (1)

sl4shd0rk (755837) | more than 2 years ago | (#36825180)

Get over it. We have a better understanding of the Cosmos now without blurry images from a couple pieces of polished glass. Think of it as an advancement in our scientific horizons.

Re:Queue the Pluto vs. Planet diatribes (1)

geoffrobinson (109879) | more than 2 years ago | (#36825284)

Both sides need to calm down.

If I want Pluto to be a planet and I have inconsistent standards for my definition (which has to be somewhat arbitrary anyway), who cares?

Re:Queue the Pluto vs. Planet diatribes (2)

MozeeToby (1163751) | more than 2 years ago | (#36825640)

I assume you mean "if I have consistent standards..." since that seems to be the most common argument.

It boils down to how many planets do you want to have in the solar system. Most honest attempts at a scientific definition that includes Pluto also include a handful of other known bodies. That's fine, 8 planets, 9 planets, 14 planets... who cares right? The problem is that modern theory predicts dozens of Pluto-like bodies in the outer solar system, and having 70+ planets listed is seen as extremely awkward, especially when only a handful of them would be scientifically interesting as individual bodies (as opposed to a class of bodies like the predicted objects in the outer Oort cloud would be).

Obligatory Star Wars reference (0)

shoehornjob (1632387) | more than 2 years ago | (#36825196)

"That's no moon. It's a space station." I'm amazed no one has posted it yet.

It's too big to be a space station. (0)

Anonymous Coward | more than 2 years ago | (#36825384)

It's too big to be a space station.

Re:Obligatory Star Wars reference (0)

Anonymous Coward | more than 2 years ago | (#36825444)

"That's no moon. It's a space station." I'm amazed no one has posted it yet.

Tiny little space station though...it is barely bigger than a super star destroyer! Maybe it was a proof of concept...

Re:Obligatory Star Wars reference (1)

steelfood (895457) | more than 2 years ago | (#36825454)

We'll find out when Pluto is suddenly replaced by an asteroid field, or when this new moon suddenly disappears.

Re:Obligatory Star Wars reference (1)

pluther (647209) | more than 2 years ago | (#36825514)

It's not a space station either. It's an anchoring point for the Charon Mass Relay.

Rebel Scum! (1)

DarthVain (724186) | more than 2 years ago | (#36826316)

Pluto is really just the debris remains of the Rebel Base Alderann.

Never again will these terrorists plague our fair and just empire!

That's no moon! (0)

Anonymous Coward | more than 2 years ago | (#36825208)

...estimated diameter of 8 to 21 miles...

That's a space station!

Pluto should still be a planet (0)

Anonymous Coward | more than 2 years ago | (#36825244)

It's spherical, it has its own moons. One definition of a planet used to be that it had enough gravity to pull itself spherical.

Planethood is an arbitrary definition. If we carry the argument to its logical ridiculous conclusion, we could change the definition such that Earth, Mars, Venus and Mercury don't qualify as planets.

Bring back Pluto I say.

Technically... (0)

Anonymous Coward | more than 2 years ago | (#36825434)

...on Pluto, they're called "fleas".

Bad definition for planet (1)

JackCroww (733340) | more than 2 years ago | (#36825438)

What I've always found peculiar regarding the definition used to demote Pluto is that by that very definition, Neptune should be a non-planet as well, seeing as it hasn't "cleared" it's orbital path either.

Re:Bad definition for planet (2)

Fred Ferrigno (122319) | more than 2 years ago | (#36825990)

If you calculate the ratio of the mass of the object to the mass of all the other objects in the same orbit, there is a vast difference between the planets and the dwarf planets. The eight planets have ratios on the order of 10^4 through 10^6, meaning they are much, much more massive than everything else in their orbit combined. The dwarf planets, including Pluto, all have ratios less than one.

Re:Bad definition for planet (1)

JackCroww (733340) | more than 2 years ago | (#36826196)

But ratios aren't in the definition. From the wikipedia article: "...a planet is a body that orbits the Sun, is massive enough for its own gravity to make it round, and has 'cleared its neighbourhood' of smaller objects around its orbit." These three criteria define a planet and Pluto definitely meets the first two. As for the last, Pluto's perihelion is inside Neptune's orbit, thus (in my humble opinion) still clutters Neptune's orbital neighborhood. I think the definition should have been chosen so as to expand the number of planets in the Solar System, possibly sparking a renewed interest in astronomy/space for the younger generations. Instead, the definition comes off as picayune and close-minded.

Mass relay... (3, Insightful)

alendit (1454311) | more than 2 years ago | (#36825856)

I thought there'd be more Mass Effect jokes. Jeeze, people, it's 2011, get over Star Wars!

Re:Mass relay... (0)

Anonymous Coward | more than 2 years ago | (#36826324)

I wish I had mod points.

Pluto has not cleared it's orbit. Not a planet. (0)

Anonymous Coward | more than 2 years ago | (#36826190)

It shares its own orbital neighborhood with countless KBOs.

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