I think that we should definitely come up with a definition of a planet and whatever that is should be made to include Pluto, since it has always been one. Just accept that Pluto is a planet and move on. After your definition is complete, that will determine if UB313 is our 10th planet or not.

Well, The tenth planet repeatedly confirmed, yet this is knowledge the Sumerians knew. A multitude of facts being "validated" in the latter 20th century and now in the 21st. The kupier belt, pluto, neptune, And Now the 10 planet(or according to Zechariah Sitchin the 12th planet) Nibiru. It holds A Name already, Nibiru. I for one insist it keep its original name.

If i may, i wish to ask its position in the solar system, Estimated or(calculated) Orbital time and distance.

Isn't "Whopper" a bit of puffery, given that it is smaller than six of our solar system's moons?

How about including the addition of the word "spherical" to the definition of the word "planet" to differentiate from the irregular-shaped objects (i.e., asteroids and Kuiper Belt objects) that tend not to be spherical?

DEF OF PLANET: A nonluminous spherical celestial body (not a comet or asteroid and larger than both) that revolves around a star, such as the sun.

I haven't yet read the other coments, and not that scientists haven't likely thought of this, but why not just call UB313 a member of a "secondary system" or "sub-planetary group" or something of the like. Especially since there are so many other bodies considered to exist, and even yet to be discovered, as part of the Kuiper Belt. Seems sensible to me. That way we can make UB313 official, and it doesn't interfere with our concept of our historical planetary system.

I suggest that the new planet (2003 UB-313) be named after Xena, the warrior princess!

I agree with Mike Brown that if Pluto is a planet then so UB313 should be too, especially now the size has been decisively confirmed as substantially larger. Some want the Pluto-like big KBOs to not be planets because they've formed as precursors to "real" planets, but didn't finish their accretion. This is overly model dependent - according to some models Uranus and Neptune are aborted cores of gas giants like Jupiter and Saturn. Should they be barred from planet status too?

If we want a physical cut-off line then the suggested 2,000 km diameter seems reasonable as it comfortably includes all the known asteroids and trans-neptunian planetoids smaller than Pluto.

If there are more objects out beyond Pluto that are bigger than we have to start rethinking what is a planet and what is a satellite or moon.

I suggest that the definition of a planet be any object orbiting the Sun that has a magnitude of 14 or brighter. So, if a hobbyist's telescope can see it, it is a planet.

When I am healthy again I'm going to update my blog at iamnathan.com with my opinion. Pluto IS a planet, and so is UB313 because it's larger. To me it doesn't matter if they strip Pluto of its rank as a planet, it will always be a planet. You don't give an honor to someone and then strip it away because they're small.

i would hate it if plutowas stripped of the title of being a planet because i as well as everyone else growing up learned about the planets and that included pluto and think it would be weird if we said it was not a planet so i really hope it continues to remain a planet.

I think that Pluto is already known as a planet and anything equal in size or bigger should also be called a planet. The size of Pluto is the limit for objects orbiting the sun to be called planets.

Interesting, and it makes me wonder how many more lie beyond. As technology increases our ability to "see" I am certain that there are many more suprises ahead.

I think it should be a planet. If pluto is a planet then y not this one. If we close our minds to the possibility that we don't know everything in the universe, then what would be the point of peering into it?

I reckon that any object big enough to gravitationally form a sphere and orbit its star should be called a planet.

It's too bad so much time was spent trying to define what a planet is. And then not coming up with an answer. I don't see a problem; in fact I think if it has been determined that UB-313 is orbiting our sun, then it should be considered to be a planet. And leave Pluto alone; it's paid its dues and should be allowed to retain its planet status.

I have thought for almost two decades that Triton must have been a binary object with something of about equal mass to have explained it's capture by Neptune. The difference between the energy of a flyby orbit at the same altitude as it's present one is about the same as Triton's weight in high explosives. Two body capture is nearly impossible, but a three body capture is a cinch.

The momentum lost by Triton would go into 2003 UB313 and result in a much hihger orbit, explaining 2003 UB313's very distant aphelion.

I have done done extensive modeling of this on GravitySimulator, a commercially available program.

One thing that I have noticed is that this scenario does not explain 2003 UB313's orbital inclination of 44 degrees. Even when the simulation is set up to get maximum inclination, the most that can be gotten is about 30 degrees. I believe there is a larger object which has perturbed 2003 UB313 into it's present inclination. I have done models of this, too. The mass of such an object needs to approach 13 Jupiter masses.

Such an object could also have transferred 2004 XR190, which fortunately has a name, Buffy, into it's observed circular orbit around the Sun.

I believe Triton, Pluto, 2003 UB313, and 2003 EL61 formed in the Sun/Neptune Lagrange points L4 and L5. In fact, I think objects formed in ALL L4 and L5 points throughout the solar system, including the moons of teh giant planets. Very few of these objects stayed in the Lagrange point, however. Most crashed onto the second mass of the Lagrangian three body systems (actually, since objects formed at BOTH Lagrange points, they are four body systems and are inherently unstable).

There are several examples of such Lagrange objects which subsequently crashed onto the second sized object of the system. The most visually striking of these is found on Uranus' moon, Miranda:

http://en.wikipedia.org/wiki/Image:Miranda.jpg

Notice the features at the two o'clock and eight o'clock positions. That is where the Lagrangians crashed at low velocity, the escape velocity of Miranda. They don't look like conventional craters because the velocity was too low. Notice the feature in the center of the photograph which was squeezed out between the Lagrange masses.

There are other examples, for instance, Asgard and Valhalla craters on Callisto, Caloris basin on Mercury, and I believe Saturn's moon Titan, which I believe was once two separate objects which collided in Saturn orbit.

I think whatever perturbed 2003 UB313 should be diligently searched for. This object is probably what is responsible for the cutoff or edge of the Kuiper belt at about 47 AU. It has been noted that the dust discs of other stars have a similar cutoff.

Such an object could have been perturbed from a more circular orbit at any time in the history of the Solar system and there is a chance it could create comet showers, which would be a civil defense matter.

Thank you very much,

Michael C. Emmert

I am very disappointed with the IAU.

Yet, I understand there is a revolution underway. The scientific communauty needs to acknowledge that the "essence" of a Planet is too be massive enough to be round-shaped. Historically, the astronomers used to study planets movements in the sky only. Now that the technology is so advanced, the scientific communauty needs to stick to simple rules.
This mighty new "space object" deserves more than being called a "KBU". As a planet, it will attract enough attention from the public to justify massive space exploration programs to explore it.

Sailom

What's all the fuss about?
Why not let any virtually spherical object that orbits a star be a planet. The pedantic can then subdivide them as they please. After all, it's highly unlikely that any creature from earth will ever touch the thing.
David

I too am disappointed with the IAU, inasmuch as they had more than enough time to sort out the larger issues involved here. This says something about the IAU, doesn't it?! Of course Brown is entitled to be “impatient” if all the IAU panel could do is twiddle its thumbs and order out for pizza.

"’I'd prefer to keep Pluto as a planet, for historical reasons,’ says Bertoldi.” Someone else (Brown?) pointed out several months ago that Pluto is “culturally” a planet. I agree, and its importance shouldn’t be underestimated in the debate over whether Pluto is a planet or a KBO. Makes sense, as it is now firmly embedded in, dare I say, our collective Global culture. That’s powerful stuff. Never mind most Americans think of “Pluto” only as an animated pet. Why force a reclassification of Pluto? It’s been accepted as a planet since discovery. Leave it alone!

Moreover, who says we're not permitted to find more planets in our Solar System?!? Just because we’re now removed quite a bit temporally from previous planet discoveries, science continues to advance and new discoveries are made. Hey, it happens.

So it’s nice that there's a Kuiper Belt, with KBOs that share certain traits very different from those found in planets closer to the sun, but that doesn’t tie our hands with respect to future discovery.

Quite obviously, there are other planet-like objects with planet-like characteristics lurking out there to be discovered. Yes, yes, they may be way off the plane of the ecliptic, but so what? I would agree, on the other hand, with those who say that in the context of distance, the Kuiper Belt is fair game but the Oort Cloud isn’t. We have to draw the line somewhere, and Pluto’s original classification as a planet puts us in what has only been known for a few decades as “The Kuiper Belt.” Fair enough.

The traditional protocols for naming planets are all well and good, but there’s no reason we can’t assign contemporaneous monikers like “Xena & Danielle” to the two objects in question, as many have suggested. Has science lost its sense of humor? If memory serves me, Pluto’s moon, Charon, was named by its discoverer for his wife, “Sharon.”

Xena & Danielle forever!

The International Astronomical Union (IAU) is still arguing over the definition of a planet - iamgine that. Now that 2003 UB313 has been discovered, now there are four new “planets” waiting to be affirmed as planets. Among them are Sedna, Quaoar and 2004 DW.
Meanwhile, every kid in America and all their science teachers are as confused as the IAU. Now - to teach there are nine planets orbiting around the sun is officially garbage. But how many are there? Are there now 13 as the numbers would suggest? Why is the IAU arguing and failing to reach consensus on how to identify a planet? And what is the cause of all this babble? Now – astonishingly – for the first time in the civilized history of man – no one on earth knows how many planets we can see because no one can agree on the definition of a planet.
Let me suggest a fix here. Pick a number guys, and then let’s move on. Perhaps the IAU needs to enlist a class of fifth graders to help them make up their collective minds.

The obvious name seems to me to be Proserpina: Pluto's wife and in Roman myth the dominant one of the pair.

I understand that there are a bunch of astronomers from Jupiter, Saturn, Uranus & Neptune that are pushing to get that puny water planet reclassified.

Going from earlier comments I suppose I should, on average, lambast the IAU for being incapable of squaring the circle (using only a straight edge and compasses), and then go on to promote a homebrew concoction of Velikovski, L.Ron Hubbard and the physics of my personal universe after finding some particularly good hashish. But no, I'm going to lambast a totally different aspect of the problem.
The issue seems to be that finding a definition of "planet" to match simple physical parameters of orbiting lumps of rock is difficult, and that UB313 must be defined as a "planet" to be given a name that is sufficiently euphonious to encourage astrologers, poets, and the like. Surely this is ass-backwards? What is needed is for someone to come up with a series of nice words that rhyme with UB313, so that poets can work their nefarious arts on them, and the astrologers can expose themselves to more ridicule.

As we should all know, we declare moon(s) are the one who circles around a planet, and the planets are the one who circles around the Sun. So lets ask our selves, does UB313 actually circles around the Sun? Does UB313 have any moons? If it does, than should we declare UB313 as a planet? Think about it.

I understand IAU's dilemma, because there's no simple solution to the problem.

There are roughly two opposite ways. The inclusive one is, like Peter above has said, to "reckon that any object big enough to gravitationally form a sphere and orbit its star should be called a planet". But this means that the biggest asteroids (Ceres, Palas, Juno, Vesta) should also be "promoted" to planets, together with Sedna, Quaoar, 2003 UB313 and 2004 DW. And the number of planets would raise continuously as more KBOs will be discovered in the future, what wouldn't be any practical at all in the long term. (Lets just imagine our grandchildren having to memorize several tens of planets at school!)

The exclusive way is to choose several criteria other than espherical shape and orbit around the Sun (arbitrary minimum diameter, maximum orbital excentricity and maximum orbital inclination relative to the eclyptic, for example), what could definitely restrict the number of planets. But this restrictions either would "demote" Pluto from its planet condition, what would find cultural objections, or would left the definition of planet still open enough to be applied to bodies like 2003 UB313.

I personally tend to favor a very restrictive solution, one that would limit the number of planets to eight, excluding Pluto. I think objectivity, simplicity, clarity and precision are far more important in Natural Sciences, specially in Astronomy, than movable and mutable cultural traditions. Copernic, Kepler and Galileo had enough courage to abandon traditional concepts about the Universe historically far more established than the planetness of Pluto, in face of their discoveries. We should follow them in this comparatively small question.

I think that we have to define "What is a planet" in terms of size, not neccessary the same size as pluto. But we have to accept pluto for historical reasons. Congratulations to all those who discovered B313 (XENA) our 10th planet or not.

From what I've read it seems that UB313 is larger than Pluto, despite the difficulties in measurements. Both appear to have same surface composition. I think that if IAU keeps Pluto classified as a Planet it should carefully study this possible new entry based in objective criteria. Science concepts don't last forever.

Isn't this a similar problem in many types of science? We start off with a limited sampling of nature that results in a bimodal distribution. Then, as we sample more and more, we realize the two peaks are not as separate as we initially thought. Since humans have this need to label things and organize them in nice neat bins, this inevitably leads to a problem when two formerly separate things must now be merged, or a "useful" cutoff point established. Has this sort of problem ever been dealt with in a systematic way in any science?

And now for something completely different: how about figuring out what a planet is for, what purpose it serves and then deciding based on that.

Perhaps Titan is a planet as well as a moon? Perhaps Mercury is not a planet? If eccentric orbits disqualify, then we lose Pluto along with the known comets. Is this a good thing or a bad?

What will we do if we discover a truly massive comet, say, one 10,000km across? (Scoff, if you feel the need, but UB313 is 3000+km across, so how large can KBOs really be? Do we have anything experimentally verifiable with which to set limits?) Is it a planet, albeit a wayward one?

Or postulate a very large (say, 2500km dia) comet that blips around Jupiter and takes up a permanent, independent orbit somewhere towards the asteroid belt? The tail's regular interactions with Jupiter's magnetosphere should make Saturn's rings look boring. Is the newly stabilised visitor now a planet, or not?

Articulating a well-defined role for planets rather than trying to pick arbitrary size limits should make decisions like that very straightforward.

Any definition of planet that requires them to be orbiting stars would rule out the so-called "rogue planets" which flit about between stars. One of the theories for Hot Jupiter formation predicts that there should be a lot of these. It also, of course, opens up the debate about how one defines "star".

A small numner of binary star system probably have sufficiently different masses for planets to be able to have orbits about the L4 and L5 points that are stable. Here too the planets don't really orbit a star (or stars).

I see this issue like this:
1.- We can distinguish a new era of Astronomy from the 90's. The huge whealth of information is changing all we understand about Universe and more locally, our Solar System.
Conclusion: we can keep the planet nomination for Pluto.
Historic reasons.
2.- The discovering of Kuiper Belt Objects(KBO) is just begining. The more we discover the more we see Pluto as KBO.
Conclusion: Not be hurried to fight to classify planet or KBO. Sorry for Mr. Brown.
3.- I think it's not a good idea to get constricted to black v/s white definition. I see the real Solar System like a continuum.
Conclusion: It must be designed a matrix that takes in account masses, distances, orbit specs, shape spheric or not, single/double/triple object, all type of resonances, etc.
Doing so would be easy to see the discussion planet/KBO is kiding.
I agree the IAU Board delay the nominations and addresses the matrix construction.
Athos Robinson

Several folks in this blog have asked for a definition of a planet. Well, here is mine.

Planet: Any material body that exhibits ALL of the following characteristics.

1. Too small to fuse Deuterium under self-gravity.

2. Spherical under self-gravity in the absence of an annual freeze-thaw cycle (as modified by rotational effects and recent impact history).

3. Uniformly differentiated (as modified by rotational effects and recent impact history).

4. Any baricenter is outside any co-orbital, non-stellar object.

All values shall permit of small non-uniformities. Earth is a planet even though the surface layer (oceans and continents) is not uniformly differentiated, but if the crust is included to a deeper depth it becomes more so.

The first defines the high end. Bigger equals star. The second two define the low end. Smaller equals asteroid, KBO, etc. The fourth distinguishes between a planet and a moon.

This definition does not require that a planet orbit a star. Rogue interstellar planets are permitted.

Some folks want to include a "must uniquely inhabit an orbit", characteristic, but I don't agree. A planet is a planet even if it is one of a double planet or an artificially created rosette. If, in some distant future, we decide it wise to park Earth in the L5 point of the Sun-Jupiter pair, would it stop being a planet? I don't think so.

I believe that in order for any body orbiting the Sun to be considered a planet, it must have at least one moon. In saying that, I'll explain that I've finished a paper proving that Mercury is actually moon to Venus. So, no matter how many planets there ends up being, we must start counting with Venus.

So will Nibiru will ever be found? I believe the technology is still limited but in a matter of years we will see more and more bigger objects, eventually planets.

(calling or not calling them planets doesn't alter anything in my opinion...).

I think we should DEFINETLY have a 10th planet!!!!

Hi
But we have to accept pluto for historical reasons. Congratulations to all those who discovered B313 (XENA) our 10th planet or not.

The traditional protocols for naming planets are all well and good, but there’s no reason we can’t assign contemporaneous monikers like “Xena & Danielle” to the two objects in question, as many have suggested. Has science lost its sense of humor? If memory serves me, Pluto’s moon, Charon, was named by its discoverer for his wife, “Sharon.”

Now we have only eight planets ;)
Do you belive that B313 (XENA) will be approved as our next planet?

do you have more pictures or where I can find them?

I think we should DEFINETLY have a 10th planet!!!!

I understand that there are a bunch of astronomers from Jupiter, Saturn, Uranus & Neptune that are pushing to get that puny water planet reclassified.

I think that we have to define "What is a planet" in terms of size, not neccessary the same size as pluto. But we have to accept pluto for historical reasons. Congratulations to all those who discovered B313 (XENA) our 10th planet or not.

Some want the Pluto-like big KBOs to not be planets because they've formed as precursors to "real" planets, but didn't finish their accretion.