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banquo's_bumble_puppy
2004-Mar-15, 02:25 PM
Sedna: Planet or not?

Iain Lambert
2004-Mar-15, 02:27 PM
Nope. All evidence so far indicates its substantially similiar to Pluto. And I'm in the "Pluto isn't one either" camp.

Madcat
2004-Mar-15, 02:30 PM
If it is a planet, it needs a better name than Sedna. Has to be Roman. :)

I say Janus, if it turns out to be the farthest planet. Gatekeeper and all. Cerberus might work too, but that's not really a god.

Spacewriter
2004-Mar-15, 02:36 PM
What's wrong with Sedna?

Grand Vizier
2004-Mar-15, 02:40 PM
If it is a planet, it needs a better name than Sedna. Has to be Roman. :)

I say Janus, if it turns out to be the farthest planet. Gatekeeper and all. Cerberus might work too, but that's not really a god.

Agreed with the Roman thing. But how can we know if it is the furthest planet? I'd play safe and call it Proserpine, which holds over the goddess theme and is what SF authors traditionally used to call the 10th planet (not Persephone, by the way - that's Greek).

Thanks for the poll, BBP, but think I'll wait for the presscon before voting - should have all the facts...

snabald
2004-Mar-15, 02:48 PM
I voted "Needs more study" it seems they don't know exactly how large it is. It could be a small highly reflective body or a large (as is larger than Pluto) non-reflective body.

Grand Vizier
2004-Mar-15, 02:52 PM
I voted "Needs more study" it seems they don't know exactly how large it is. It could be a small highly reflective body or a large (as is larger than Pluto) non-reflective body.

Indeed. And space.com now has it as .75 Pluto diameters. I think I would only vote for planetary status if it was larger than Pluto (and then I'd want a Roman name).

http://www.space.com/scienceastronomy/new_object_040315.html

But I don't think it's the size that counts here. It seems to be unusually red, and other sources are claiming it is an Oort Cloud object...

Anthrage
2004-Mar-15, 03:22 PM
My suggestion for dealing with this problem is laid out here (http://www.badastronomy.com/phpBB/viewtopic.php?p=223576&highlight=#223576). Basically, I think it's time for new terminology, and not redefinition of the existing family of planets. Distance, not size, in my opinion, should be the defining variable.

etLux
2004-Mar-15, 04:08 PM
I object to them naming this newly discovered orbiting body "Sedna".

This sort of high-handed behavior always annoys me. Where do they get off choosing the name of this thing? My taxes paid the freight to discover it, so I should certainly have a say in the matter.

I therefore take my citizen's right to name the object I paid to find.

Henceforth, "Sedna" shall be know as...

Planet Federal Express

The Bad Astronomer
2004-Mar-15, 04:48 PM
Using distance to define planet won't work, because it's arbitrary. What we have now is arbitrary. So it's really no change.

I have a lot of thoughts about this, and someday I will write them all down, but it'll be 3000 or so. :o But basically, we cannot define what a planet is without making, somewhere, an arbitrary line in the sand. The Universe is under no obligation to fall into our nice, neat little categorical boxes. The real Universe is a continuum.

Ut
2004-Mar-15, 05:12 PM
But the lines, no matter how arbitrary, have been drawn. It's just that no one knows where.

A comet is not a planet. Nor is an asteroid.
A planet is not a brown dwarf.
A brown dwarf is not a star (this one's quite a bit less arbitrary, and shows a distinctly non-seamless transition)

Really, they're all just bodies in space. They're all essentially the same sort of thing, made out of the same sort of stuff. But we've made the decision to separate the little boys from the big boys, and the boys from the men.

Grand Vizier
2004-Mar-15, 05:22 PM
A planet is not a brown dwarf.
A brown dwarf is not a star (this one's quite a bit less arbitrary, and shows a distinctly non-seamless transition)


Yeah - it's at the upper range of mass that the planet/non-planet distinction becomes a bit more meaningful, I'd have thought. It just becomes too pompous saying 'self-luminous nuclear-fusion-powered bodies' - as against everything else. Might as well say planet/brown dwarf/star...

But... Is a high-mass brown dwarf that is burning deuterium temporarily a star while it's doing that thang? There are problems even at this end of the spectrum...

Fin

Eroica
2004-Mar-15, 05:57 PM
What Iain Lambert just said. 8)

Grand Vizier
2004-Mar-15, 06:20 PM
OK - just voted no. Official release now in at:

http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/release.shtml

Nevertheless... 'Second reddest object in the solar system' and first Oort Cloud object. May not be a tenth planet - but it's a hell of a story...

Andromeda321
2004-Mar-15, 07:04 PM
I don't know why, but I kinda think it would be a good idea to rename Mercury, Venus, Earth, Mars, and Pluto as asteroids and reserve the term "planet" for gaseous bodies that never reached stellar fusion. Or maybe just get rid of the term planet altogether and call everything an asteroid so we wouldn't have all these definition problems anymore. :wink:
In all honesty though, I'm waiting for a bit of follow-up data on this thing. I also think it's further evidence to show that it's rather likely we'll find something even bigger then Pluto in the future. That's when the REAL ruckus will start up.

mario
2004-Mar-15, 07:18 PM
I think we're all avoiding the real issue here: what's going to happen to "My Very Excellent Mother Just Served Us Nine Pizzas"? It worked so well for remembering the order of planets in elementary school, and even had the number 9 for the number of planets!

Also, this has gotta be bad news for Pluto. Furthest planet from the Sun? Smallest planet in the solar system? Longest solar orbit? We have a new reigning champion, and strong physical evidence for the Oort Cloud to boot.

Russ
2004-Mar-15, 07:31 PM
My vote was "Needs More Study". I can't remember how many times something like this has been discovered and reclassified after they found out it was something other than what they originally thought. :roll:

Two of my favorites are: "We've found the edge of the universe!" and "We have determined how old the universe is!" Both of these have changed about a dozen times since I started keeping track in about 1965. :roll: :lol:

Ut
2004-Mar-15, 07:38 PM
I think we're all avoiding the real issue here: what's going to happen to "My Very Excellent Mother Just Served Us Nine Pizzas"? It worked so well for remembering the order of planets in elementary school, and even had the number 9 for the number of planets!

My Very Excellent Mother Juse Served Us Nine Pizza Subs.

Happy?

I voted "More Study", but now side with "No." With Pluto in dispute, anything smaller than it is simply out of the question. I'm one for maintaining Pluto's planetary status for historical reasons. Evidense of the Oort cloud, though, is exciting.

Grand Vizier
2004-Mar-15, 08:09 PM
I voted "More Study", but now side with "No." With Pluto in dispute, anything smaller than it is simply out of the question.

I agree. Simple view:

1.0001 X Pluto diameter - 10th planet
0.9999 X Pluto diameter - sorry - wait for the next one...

It is to do with history, teaching (importance of mnemonics noted) and other cultural baggage - but not a scientific question, really.

mario
2004-Mar-15, 08:37 PM
We need to come up with some sort of clear-cut definition as to what makes something a 'planet', as opposed to an asteroid or other large celestial body. As Mr. Plait noted, we may have to simply resort to arbitrarily defining some minimum for planethood, but can't we think of something better than the object's diameter?

I guess a good first step towards attempting to define a planet would be to figure out exactly what separates it from, say, an asteroid. I've been wracking my brain trying to figure out just what separates the two, but I'm currently at a loss. Any thoughts?

SciFi Chick
2004-Mar-15, 09:17 PM
Do asteroids have cores? I mean, that puts places like Earth and Mars in a different category from asteroids, doesn't it?

Grand Vizier
2004-Mar-15, 09:20 PM
I guess a good first step towards attempting to define a planet would be to figure out exactly what separates it from, say, an asteroid. I've been wracking my brain trying to figure out just what separates the two, but I'm currently at a loss. Any thoughts?

Not sphericity, for sure - Ceres, at least, will be a spherical body. Frankly, there is no such hard and fast *scientific* distinction that I can think of.

Muddy waters indeed. Leaving the definition of 'planet' out, what distinguishes asteroids from comets? Right now, it is theorised that some asteroids, particularly those with eccentric orbits, may actually be burnt-out comets (boiled down to their silicates, sort of).

So, if this is true, a comet may become an asteroid (assuming we define a comet as being predominantly icy) - so at what ice/non-ice ratio does it cross the line between asteroid and comet?

Sorry - my point is just what the BA said earlier - you can only draw a line in the sand (though you can always redraw the line in the light of new evidence). You are always going to get what I'd call 'border conditions' - it's a consequence of how we use language.

The important thing is that we continue to come up with good testable hypotheses about broad classes of objects. But we have objects that crossover - brown dwarfs that fuse deuterium (hence they are sort of stars, for a while), planets on the edge of brown dwarf status, comets that become asteroids etc etc...

I think we should be relieved that the universe cannot be conveniently pigeonholed - the fun is in all this complexity...

Swift
2004-Mar-15, 09:21 PM
I'm not sure I actually understand this big debate about what is a planet? Do the inhabitants of Pluto get an extra vote in the Solar System Senate if Pluto is a planet? :) Either there is something different in the astro-physics of what makes a planet versus something else, or it's an arbritary distinction based on drawing a boundary across some scale (diameter, mass, how eliptical the orbit is, etc.).

Somehow in my mind asteroids are a different thing, even though there are some "double" asteroids (two oribiting a center of gravity). The inner rocky bodies (Mercury, Venus, Earth, Mars) and the large gas giants (Jupiter, Saturn, Uranus, Neptune) seem to fit everyone's definition of a planet.

The questionable ones are the medium sized, ice (?) bodies like Pluto (maybe a couple of hundred to a couple of thousand km diameter). Is it believed that they all formed in a similar manner and just ended up in different orbits? In that case, whether they are a planet or not seems based on orbit, which IMHO is not a good measure. But if Pluto, the Kupier objects and the Ort objects formed differently or have different structures/compositions, then they are truely different bodies, whether they are planets or not.

mario
2004-Mar-15, 09:31 PM
The weird thing is, I think of things like Pluto, Jupiter, or Terra, and I just know that these are planets. But I don't know why they're planets! And I look at an asteroid and say "Yep, that's an asteroid. No mistaking that for a planet, no sir." But just what am I seeing that allows me to make this distinction? I would attribute this to some form of pareidolia, but I've never mistaken a photo of a celestial body for Vladimir Lenin.

Maksutov
2004-Mar-15, 10:02 PM
Well, in industry, there is usually a standards organization that is responsible for terms and definitions within the particular field of endeavor over which they have authority.

It would seem here the IAU would be the standards organization.
A search of their website showed the following to be their current position on this matter:


THE STATUS OF PLUTO: A CLARIFICATION
IAU Press Release 01/99
February 3, 1999:

FOR IMMEDIATE RELEASE

Recent news reports have given much attention to what was believed to be an initiative by the International Astronomical Union (IAU) to change the status of Pluto as the ninth planet in the solar system. Unfortunately, some of these reports have been based on incomplete or misleading information regarding the subject of the discussion and the decision making procedures of the Union.

The IAU regrets that inaccurate reports appear to have caused widespread public concern, and issues the following corrections and clarifications:


No proposal to change the status of Pluto as the ninth planet in the solar system has been made by any Division, Commission or Working Group of the IAU responsible for solar system science. Accordingly, no such initiative has been considered by the Officers or Executive Committee, who set the policy of the IAU itself.


Lately, a substantial number of smaller objects have been discovered in the outer solar system, beyond Neptune, with orbits and possibly other properties similar to those of Pluto. It has been proposed to assign Pluto a number in a technical catalogue or list of such Trans-Neptunian Objects (TNOs) so that observations and computations concerning these objects can be conveniently collated. This process was explicitly designed to not change Pluto's status as a planet.
A Working Group under the IAU Division of Planetary Systems Sciences is conducting a technical debate on a possible numbering system for TNOs. Ways to classify planets by physical characteristics are also under consideration. These discussions are continuing and will take some time. The Small Bodies Names Committee of the Division has, however, decided against assigning any Minor Planet number to Pluto.


From time to time, the IAU takes decisions and makes recommendations on issues concerning astronomical matters affecting other sciences or the public. Such decisions and recommendations are not enforceable by national or international law, but are accepted because they are rational and effective when applied in practice. It is therefore the policy of the IAU that its recommendations should rest on well-established scientific facts and be backed by a broad consensus in the community concerned. A decision on the status of Pluto that did not conform to this policy would have been ineffective and therefore meaningless. Suggestions that this was about to happen are based on incomplete understanding of the above.

The mission of the IAU is to promote scientific progress in astronomy. An important part of this mission is to provide a forum for debate of scientific issues with an international dimension. This should not be interpreted to imply that the outcome of such discussions may become official IAU policy without due verification that the above criteria are met: The policy and decisions of the IAU are formulated by its responsible bodies after full deliberation in the international scientific community.
Johannes Andersen General Secretary, IAU

For more information, contact the Secretariat or the Division President, Mikhail Ya Marov, Keldysh Inst Applied Maths, Moscow, Russia.

************************************************** ***********
The International Astronomical Union (IAU), founded in 1919, is the international non-governmental organization uniting professional astronomers all over the world. It currently has 61 Member States and over 8,300 Individual Members in 83 countries. Its scientific activities are coordinated by 11 Divisions and 40 Commissions spanning the entire field of astronomy. The IAU is integrated in the international scientific community through its membership of the International Council for Science (ICSU) and represents astronomy in committees of the UN and other international organizations. The permanent IAU Secretariat is located in Paris, France. (see below).

************************************************** ***********

IAU/UAI Secretariat
Institut d'Astrophysique Tel: +33 1 4325 8358
98bis, Bld. Arago Fax: +33 1 4325 2616
F - 75014 Paris E-Mail: iau@iap.fr
France WWW: http://www.iau.org


************************************************** ***********
>>>
What's obviously missing, and may be in need of some immediate IAU work, is a definition or standard for what constitutes a planet.

TheGalaxyTrio
2004-Mar-16, 12:20 AM
But basically, we cannot define what a planet is without making, somewhere, an arbitrary line in the sand.

At last! A challenge to which I am up.

What an odd sentence...

Anyway, since you all can't come up with a line, I will.

An object is a planet if its diameter is greater than 857.3 miles.

There. Now we can all move on. :)

Anthrage
2004-Mar-16, 12:59 AM
Phil -
Using distance to define planet won't work, because it's arbitrary. What we have now is arbitrary. So it's really no change.

Exactly as I said, of course distance would be arbitrary. However, it would represent a change, in that it would establish a definite and forseeably inviolate criteria. The odds of us being faced with an object that is larger than pluto, and which spends the majority of it's time within pluto's orbit is unlikely. It would ensure the issue of 'what is a planet' - at least in the context of our solar system - is put to rest however. Anything further away and smaller tha pluto cannot be a planet - period. I myself somewhat enjoy the irony of going from pluto being on the chopping block, to being the executioner. ;)

Although that does bring up an interesting point - if we use a relative definition, it cannot be applied logically elsewhere; to other solar systems. True, this may not be as pressing an issue as the one we face now, but it is a reality.

In any case, perhaps because the details were in another thread linked from this one, no-one has commented on my proposal. Am I the only one who sees the need for new terminology, and a new and and secure-by-nature definition of what constitutes a planet in our solar system? This issue will not go away, and will only become more of a problem. :)

It is more about simplicity and history, education and clarity than anything else. Whatever criteria we establish will be arbitrary. Most things are. I think consistency, especially in this context, is more important.

In any case, aside from the question of pluto and this new body are, or what classification should be used, does anyone thing a firm and final judgment needs to be made on this issue, and if so, do you think it will be made now, before the discoveries continue?

Grand Vizier
2004-Mar-16, 01:29 AM
In any case, aside from the question of pluto and this new body are, or what classification should be used, does anyone thing a firm and final judgment needs to be made on this issue, and if so, do you think it will be made now, before the discoveries continue?

I do understand your point, but I think that obsolete categories (because this is what this is about) should simply be left to wither on the vine - eventually they just become redundant and ignored. No need for any big dramatic declarations. It's about language, not science.

I do not think that anyone will lay down the law either - the IAU is the only authority who might, and they have abdicated the responsibility (can't blame them).

So it's down to people like us bickering about it. And, of course, the media. :)

Superluminal
2004-Mar-16, 01:33 AM
All this talk of what should be considered a planet gives me a headache. We can come up with a complicated classification system. (Pluto is a class IDSEta type planet, Icy, Distant, Small, Elliptcal orbit, thin atmosphere, more headaches.) #-o

Just try and keep it simple. Would you call an Earth like planet orbiting a Jovian type planet a planet or a moon? I would think that you would call it an Earth like moon, so that people would know you are talking about a planet that is not orbiting its sun independantly, but orbiting another planet.

Jupiter has a rocky core about the size of Earth. How deep and thick would the atmosphere of a planet have to be to be called a Jovian planet and not a terrestrial planet?

I have an old astronomy book that lists Plutos diameter as 7,500 miles. So it's easy to see why it was classed as a planet. Pluto has been demoted enough. I agree, anything Pluto sized or larger is a planet.

Anthrage
2004-Mar-16, 01:45 AM
Grand Vizier -
No need for any big dramatic declarations. It's about language, not science.

Exactly, it is about language, not science. We all know how badly the media misrepresents and confuses things, there are enough people out there who's knowledge base is questionable without their being more confused by this issue and it's discussion. And it will be discussed, as it is now, and as it will be every time an object of this kind is found, as it always is. Unless someone makes a strong and clear judgment, the public will do what it usually does in such cases - and that won't be good for anyone. :)

JohnOwens
2004-Mar-16, 02:23 AM
Perhaps we should set up one of those websites like those "Am I hot or not?" ones? Call it "Am I a planet or not?". :lol: :wink:

Grand Vizier
2004-Mar-16, 02:43 AM
[...] Unless someone makes a strong and clear judgment, the public will do what it usually does in such cases - and that won't be good for anyone. :)

With respect, Anthrage, I think you're taking the issue a little too seriously? :)

It's not about the ethics of euthanasia or worries about teenage sex, alcohol use and drug abuse - it's about a tiny niggling semantic problem to do with small planetary objects on the very edge of the Solar System. The world will not be destroyed overnight if we just leave the whole issue warm and fuzzy...

Manchurian Taikonaut
2004-Mar-16, 02:52 AM
SEDNA

Some are saying the correct term is now "Planetoid" too big to be a kupier belt object or Asteroid

and too small to be a planet ( smaller than pluto )

Xbalanque
2004-Mar-16, 02:59 AM
Still, it seems clear that as we continue to discover new objects in our solar system, and as we begin to discover those in other solar systems, we are going to need to develop some sort of new, or at least amended, classification scheme. I don't see this as a bad thing. Rather, it speaks volumes about how much we've learned about the universe since the days when planets were simply wanderers.

Anthrage
2004-Mar-16, 03:02 AM
Grand Vizier - My thanks for your sarcasm, but I do not think one must elevate this issue to one of seriousness, such as the ethics of euthanasia or worries about teenage sex, alcohol use and drug abuse...or the world being destroyed overnight...in order to discuss it, or to believe it is one that needs to be addressed.

It may not be of interest to everyone, but it is to many, and it should be treated as such. Call me crazy, but I like to think that anything that will be part of a lesson plan or found in a textbook should be clear and consistent...

As for your suggestion, when I take something too seriously, it will be sufficiently obvious, and more than one person's opinion which considers it so. [-(


Xbalanque - Exactly. And the sooner we decide upon these things, the better. By the time they become of more practical importance, when we are interacting with these bodies, the designations will be established, having been in use for a considerable period of time.


Manchurian - Planetoid was my suggestion as well, in the other thread - perhaps with modifiers that are relative to it's primary orbital environment. Kuiper Planetoid, Oort Planetoid etc.


Such a term may also help counter the hysteria-drumming attempts of some out there preaching doom about the 10th planet. It may seem simplistic, but the emotional and psychological reaction to a word like 'planetoid' is inherently 'soft', as it conjures up images of something small/smaller, as well as derivative, and I think, less threatening sounding. Of course, if you attach words like 'incoming' and 'in danger of impact', well, you could call it a nerfel and people would get hysterical. :)

The dictionary definition of the -oid suffix is:

-oid
suff.

1. Resembling; having the appearance of; related to: acanthoid.
2. One that resembles something specified or has a specified quality: humanoid.

Also:

<jargon> (from "android") A suffix used as in mainstream
English to indicate a poor imitation, a counterfeit, or some
otherwise slightly bogus resemblance...

Sounds good to me.

mario
2004-Mar-16, 07:24 AM
OK, I think I found something that we can apply to the current model (a.k.a. our solar system):

http://www.space.com/scienceastronomy/planet_denitions_030227.html

In particular, this caught my eye:


Basri would like to accommodate Pluto and those who can't fathom its demotion. He proposes that the murky lower limit for planet-hood get set at a diameter of about 435 miles (700 kilometers). That's roughly the bulk needed to allow gravity to shape an object into a sphere, depending on density. Smaller objects -- both asteroids and comets -- tend to look like potatoes or bell peppers.

This would seem to be a scientifically sound basis of definition. Under this model, Pluto keeps its planethood, and several others would join the ranks: Ixion, Quaoar, Varuna, Ceres, and the newcomer Sedna. I could live with fourteen planets, even though it throws the mnemonic devices completely out the window... well, if someone can tell me the order of these fourteen planetoids, I'll figure something out.

Eroica
2004-Mar-16, 08:21 AM
I say Janus, if it turns out to be the farthest planet. Gatekeeper and all. Cerberus might work too, but that's not really a god.
... I'd play safe and call it Proserpine, which holds over the goddess theme and is what SF authors traditionally used to call the 10th planet (not Persephone, by the way - that's Greek)
Before you start naming it, you should check out the names that have already been assigned to asteroids:

Minor Planets (http://www.fourmilab.ch/yoursky/catalogues/asteroid_names.html)

Persephone, Proserpina and Cerberus have been taken. But Janus is still available.

Eroica
2004-Mar-16, 08:36 AM
But basically, we cannot define what a planet is without making, somewhere, an arbitrary line in the sand.
I disagree. One fundamental difference between the eight "main" planets and the rest of the Solar System (including Pluto) is the way in which they formed. According to Ask the Astronomer (http://www.astronomycafe.net/qadir/q1275.html), even the inner terrestrial worlds were once gas giants; but the ferocious Solar wind during the Sun's early T Tauri phase blew them away! Ergo, Pluto is not a planet.

AK
2004-Mar-16, 10:09 AM
Persephone, Proserpina and Cerberus have been taken. But Janus is still available.

Except Janus (http://www.nineplanets.org/janus.html) is already a moon of Saturn.

Grand Vizier
2004-Mar-16, 10:41 AM
[quote=Grand Vizier]
Minor Planets (http://www.fourmilab.ch/yoursky/catalogues/asteroid_names.html)

Persephone, Proserpina and Cerberus have been taken. But Janus is still available.

It's already been pointed out that Janus is a moon of Saturn. But actually duplication is no obstacle - it's already occurred.

Check these asteroids:

85 Io
38 Leda (also Jupiter XIII)
53 Calypso (also Saturn XIV)

...and many more. It's kind of an unfortunate way of doing things, but understandable, given that 19th-century asteroid discoverers mined Roman mythology extensively and we are left with their namings (85 Io was found in 1865).

So I still say Proserpine for Planet 10 (when it comes up) to honour old SF tradition. Janus is actually pretty good, but does the IAU allow duplication between moons and Oort-/Kuiperoids?

milli360
2004-Mar-16, 11:07 AM
This would seem to be a scientifically sound basis of definition. Under this model, Pluto keeps its planethood, and several others would join the ranks: Ixion, Quaoar, Varuna, Ceres, and the newcomer Sedna. I could live with fourteen planets, even though it throws the mnemonic devices completely out the window... well, if someone can tell me the order of these fourteen planetoids, I'll figure something out.
Fourteen? What about 23 (http://www.badastronomy.com/phpBB/viewtopic.php?p=34053&highlight=ceres#34053)? :)


But basically, we cannot define what a planet is without making, somewhere, an arbitrary line in the sand.
I disagree. One fundamental difference between the eight "main" planets and the rest of the Solar System (including Pluto) is the way in which they formed. According to Ask the Astronomer (http://www.astronomycafe.net/qadir/q1275.html), even the inner terrestrial worlds were once gas giants; but the ferocious Solar wind during the Sun's early T Tauri phase blew them away! Ergo, Pluto is not a planet.
How do you imagine the others formed? :)

TriangleMan
2004-Mar-16, 11:54 AM
Persephone, Proserpina and Cerberus have been taken. But Janus is still available.

I vote for its name to be Tartarus, it goes well with it being beyond Pluto. :)

milli360
2004-Mar-16, 11:58 AM
I vote for its name to be Tartarus, it goes well with it being beyond Pluto.
At first, I thought Sedna was kinda goofy.

She's the goddess of the sea, right?

Grand Vizier
2004-Mar-16, 12:03 PM
I vote for its name to be Tartarus, it goes well with it being beyond Pluto. :)

Sisyphus would also be a good name for an object with such an eccentric orbit (Rolling a big stone all the way up a steep hill only to have it roll down again and again? For hill read 'gravity well'.)

TriangleMan
2004-Mar-16, 12:16 PM
At first, I thought Sedna was kinda goofy.
She's the goddess of the sea, right?
Yes, in Inuit (http://www.hvgb.net/~sedna/homepage.html) mythology.

Eroica
2004-Mar-16, 12:28 PM
How do you imagine the others formed? :)
I have no idea, but I got this in an email yesterday from David Moore, chairperson of Astronomy Ireland and editor of Astronomy & Space:

There was a move a few years ago (reported in our magazine) to relegate Pluto to the Edgeworth-Kuiper Belt of asteroids (a belt of minor planets found beyond the orbit of Neptune, and first
proposed by the Irish astronomer Kenneth Edgeworth in 1943). The International Astronomical Union decided against this and Pluto is officially a planet, but it seems certain it did not form by the same method that the 8 major planets did and it really belongs to the EK belt. [emphasis edded]

milli360
2004-Mar-16, 01:12 PM
How do you imagine the others formed?
I have no idea, but I got this in an email yesterday from David Moore
In order to use this as a basis for distinguishing between planets and non-planets, we'll have to be more specific though.

Did our moon form in the same fashion as the planets? Would it be a planet then? If it did not, then we're still in trouble--clearly, if Pluto were the size of the moon, we would not be arguing whether it was a planet. Everyone would agree that it was a planet. I mean, there have been a lot of people suggesting that the Earth and moon system is a double planet even. And then there are the icy moons of similar size.

Jim
2004-Mar-16, 01:31 PM
I agree we need a better - and more substantial - definition of what is a planet. Any definition we do develop should include Pluto, but doesn't necessarily have to; Pluto can be grandfathered in.

But, Sedna is not a "planet."

BTW, have we already forgotten Quaoar?

Eroica
2004-Mar-16, 05:38 PM
Did our moon form in the same fashion as the planets? Would it be a planet then?In the case of binaries and multiple systems, the largest member (in this case, the Earth) would be considered a planet, and the rest its satellites. 8)

Of course, that still leaves the rocky asteroids to take care of. :-k

mario
2004-Mar-16, 05:44 PM
This would seem to be a scientifically sound basis of definition. Under this model, Pluto keeps its planethood, and several others would join the ranks: Ixion, Quaoar, Varuna, Ceres, and the newcomer Sedna. I could live with fourteen planets, even though it throws the mnemonic devices completely out the window... well, if someone can tell me the order of these fourteen planetoids, I'll figure something out.
Fourteen? What about 23 (http://www.badastronomy.com/phpBB/viewtopic.php?p=34053&highlight=ceres#34053)? :)

Well, that figure also includes the moons that meet the size criteria, but I imagine another requirement would be that it be orbiting a star. A body orbiting another planet would be a satellite, regardless of size. Granted, this isn't the best method of nomenclature, but I don't think we'll ever come up with something satisfactory until we do away completely with the vague "planet" term, and start labeling objects by their composition and cosmogony. So Pluto would be an icy Kuiper Belt Object, or something.

informant
2004-Mar-16, 08:18 PM
In the case of binaries and multiple systems, the largest member (in this case, the Earth) would be considered a planet, and the rest its satellites. 8)

Of course, that still leaves the rocky asteroids to take care of. :-k
We're trying to reconcile two incompatible criteria: size and relation with respect to other celestial bodies. Any object can be a "satellite" of another, no matter how large. Even a star. The term "satellite" describes how an object relates to others.
I think we need another criterium, independent of an object's relation to others, that describes only its size and formation.

Edoltc
2004-Mar-16, 08:56 PM
I was thinking in "Diana" or "Minerva" in other thread but they are already taken. Now I think ERIS would be the best name, since apparently she allready throw the apple of discord on the astronomy comunity. Anyway I still think that Sedna has a very sad story. (http://www.hvgb.net/~sedna/story.html)

tracer
2004-Mar-18, 02:56 AM
If it is a planet, it needs a better name than Sedna. Has to be Roman. :)
I hate to burst your bubble here, but "Uranus" isn't a Roman name either. (It's Greek.)

And last I heard, "Earth" was a rather Germanic name. ;)

Odinoneeye
2004-Mar-18, 05:34 AM
I say call it a planet.

I've been waiting for decades for them to discover a new one and it's about damn time!

I would also like to stick with a roman name. Persephone is a good one, however there are so many major female dieties with no representation. Juno, Diana, Vestia.

informant
2004-Mar-18, 09:07 AM
If it is a planet, it needs a better name than Sedna. Has to be Roman. :)
I hate to burst your bubble here, but "Uranus" isn't a Roman name either. (It's Greek.)
It's Greek and Roman. (Uranus in Latin, Ouranos in Greek; they are similar, but the names of the planets are always derived from the Latin version.) Anyway, I think Madcat's main point was that it should be a name from the Greco-Roman pantheon. I agree.


And last I heard, "Earth" was a rather Germanic name. ;)
Earth, the Moon and the Sun are exceptions, understandably.

Kaptain K
2004-Mar-18, 09:29 AM
Terra or Tellus?

Xbalanque
2004-Mar-18, 09:40 AM
Earth, the Moon and the Sun are exceptions, understandably.

And all mind-numbingly obvious. That's like naming your pet dog, Dog.

We get stuck with "the Sun" while some alien out there gets Betelgeuse.

:-?

(Please don't nitpick this post, i.e., the odds that Betelgeuse would have a planet that would support life, and the odds that they would, in fact, refer to their sun as Betelgeuse. :) )

informant
2004-Mar-18, 09:54 AM
(Bad pun alert!)
You could say we call 'em as we see 'em. 8)

Sparks
2004-Mar-18, 10:03 AM
Forgive me for asking the apparently contraversial question, but why does the name have to be from the Greco-Roman pantheon? Is there some obscure rule from the IAU that says "well, we don't actually have a definition for exactly what a planet is, but you have to name them after hellenic gods".
I mean, *points at stars*, they're not named after hellenic figures, are they?

Personally, I like the name Sedna. It seems to fit. The name of a god, but not one of the usual gods, for a rock noone can decide is a planet or not.

Xbalanque
2004-Mar-18, 10:12 AM
Forgive me for asking the apparently contraversial question, but why does the name have to be from the Greco-Roman pantheon? Is there some obscure rule from the IAU that says "well, we don't actually have a definition for exactly what a planet is, but you have to name them after hellenic gods".
I mean, *points at stars*, they're not named after hellenic figures, are they?

Personally, I like the name Sedna. It seems to fit. The name of a god, but not one of the usual gods, for a rock noone can decide is a planet or not.

There's a whole lot of myths out there to choose from. I have no problem with getting away from the Greco-Romans. My only gripe with Sedna is that it's only one vowel removed from the Kia Sedona. But then again, we do name cars from these same myths, don't we?

Sparks
2004-Mar-18, 10:35 AM
My only gripe with Sedna is that it's only one vowel removed from the Kia Sedona.
The which now?

informant
2004-Mar-18, 10:38 AM
Forgive me for asking the apparently contraversial question, but why does the name have to be from the Greco-Roman pantheon?
Tradition and coherence.
Not all objects (http://www.badastronomy.com/phpBB/viewtopic.php?t=2388&highlight=quaoar) in the solar system are named after figures from the Greco-Roman mythology. For instance, Kuiper Belt Objects are not. However, all planets except Earth are.

JohnOwens
2004-Mar-18, 10:40 AM
There's a whole lot of myths out there to choose from. I have no problem with getting away from the Greco-Romans. My only gripe with Sedna is that it's only one vowel removed from the Kia Sedona. But then again, we do name cars from these same myths, don't we?

Well, there's the Saturn, the Mercury, the Merkur, the Skorpio, the Aries (sp?), probably more. So, what's your point again? :wink:

Sparks
2004-Mar-18, 10:42 AM
For instance, Kuiper Belt Objects are not. However, all planets except Earth are.
But Sedna's a KBO, not a planet - so wouldn't it be less coherent to name it as if it were a planet?

informant
2004-Mar-18, 10:45 AM
Possibly a KBO, or an Oort Cloud object.
My point was that if/when it is declared a planet, it should be given a name from the Greco-Roman pantheon. Until then, I think Sedna is fine.

Kaptain K
2004-Mar-18, 03:39 PM
My only gripe with Sedna is that it's only one vowel removed from the Kia Sedona.
The which now?
Kia - Korean car company
Sedona - SUV (sport utility vehicle), Named for a town in Arizona, USA

Grand Vizier
2004-Mar-18, 05:00 PM
Forgive me for asking the apparently contraversial question, but why does the name have to be from the Greco-Roman pantheon? Is there some obscure rule from the IAU that says "well, we don't actually have a definition for exactly what a planet is, but you have to name them after hellenic gods".

One reason, I think is that then you can apply the truly bizarre unwritten rule that all words pertaining to the planet must be derived from Greek, while the planet's name is Latin.

I do think this is (rightly, in my opinion) falling into disuse. I've noticed that the geologists working on the Mars missions are just referred to as geologists, not areologists. And it seems increasingly common to refer to 'pericentre' or 'apocentre' rather than 'pericynthion' or 'apocynthion' (except in the case of Earth and the Sun). The Moon is a total minefield here, it's not just a case of Greek/Latin - it's identified with several different deities, so we have 'pericynthion', or 'perilune' depending on your preferences, but the study is 'selenology'.

Venus, of course, is a total mess, with 'Venusian', 'venerean' (avoiding the embarrassing use of 'venereal') and 'cytherean'. (And would Pluto studies be 'hadeology'?)

Anyway, it spoils that game calling something Sedna - no Greek derivative.

[Edited to include the Sun]

mario
2004-Mar-18, 05:33 PM
Not all objects in the solar system are named after figures from the Greco-Roman mythology. For instance, Kuiper Belt Objects are not. However, all planets except Earth are.

Meh, I prefer the Latin names for Earth, Moon and Sun anyway (Terra, Luna and Sol, respectively). Though it would be nice if our planet was called something other than "dirt".

milli360
2004-Mar-18, 05:46 PM
Though it would be nice if our planet was called something other than "dirt".
What's wrong with dirt? Besides, that's backwards. If our planet were called Li Rotunde Supremi, the stuff under your fingernails would be called rotun.

mario
2004-Mar-18, 05:56 PM
*reads "From The Li Rotunde Supremi To The Moon"*

*sings "Li Rotunde Supremi Angel"*

*washes his inexcusably rotundy car*

Eroica
2004-Mar-18, 06:00 PM
... Li Rotunde Supremi ...
Is she related to La Stupenda, (http://www.cygnet.co.uk/thedame/) by any chance? :D

hedin
2004-Mar-18, 07:59 PM
Madcat said "If it is a planet, it needs a better name than Sedna. Has to be Roman."

I ask why? Is Inuit mythology in any way inferior to roman? And if so I detest that viewpoint on the basis of me being a Faroese native, seeing that I have many friends from Greenland. I have never thought of their way of looking on the world as being inferior to people of another race or creed.

Taibak
2004-Mar-18, 09:48 PM
I'm going to have to agree with 'Needs More Study.'

If Sedna turns out to be a Kuiper Belt object, I would say it's not a planet.

If Sedna turns out to be an Oort Cloud object, I would say it's not a planet.

If it turns out to have the same composition as a typical comet, I would say it's not a planet.

If it's none of those, it may very well be a planet *if* it's considered big enough. Along these lines, anyone know how big it is compared to, say, Ceres or Quaoar?

milli360
2004-Mar-18, 10:18 PM
Along these lines, anyone know how big it is compared to, say, Ceres or Quaoar?
Apparently, there are a couple lines of evidence that both say it is intermediate between Quaoar and Pluto.

LynnF1
2004-Apr-16, 08:39 PM
Hi! Newbie here - pls be gentle!

I'm reckoning it to be a planet - I accept the test of (more or less)spherical-ness due to mass; as well, it's orbiting the "major player" in the solar system.