It's official: IAU says Pluto is a "plutoid"

[JonathanN]

Good morning all,

Well, it's official. The International Astronomical Union has declared that objects like Pluto and Eris are henceforth to be known as "plutoids".

This'll put the cat amongst the pigeons . . . sorry, I meant plutinos amongst the asteroids.

Details at www.spaceinfo.com.au/iau20080612.html (http://www.spaceinfo.com.au/iau20080612.html)

Regards,

Jonathan


Jonathan Nally
Editor
SpaceInfo.com.au
www.spaceinfo.com.au (http://www.spaceinfo.com.au)

[renormalised]

How imaginative can you get.....plutoid. Must've taken all of 100 days for them to figure that one out:rolleyes::einstein:

They should've given the naming rights to a bunch of primary school kids. At least they would've come up with something a bit more interesting and imaginative!!!:rolleyes::D

[madtuna]

Just thank your lucky stars Pluto wasn't originally named after some mythical god named Hemmer..else we'd be in a real pickle trying to rename the damn thing about now!

[renormalised]

There wouldn't be enough cream in every pharmacy on this planet to sooth that one!!!:P:D

[bojan]

:rofl::rofl::rofl::rofl::rofl::rofl :

[Ian Robinson]

I don't care what that say it will be called , as far as I'm concerned it was and remains , a planet.

The guys in that committee need to get onto more important issues.

[Geoff45]

Well, once upon a time the sun and the moon were regarded as planets--the word means "wanderer". The earth, being thought of as the centre of the universe wasn't a planet. I'm sure after Galileo came along there were still people who remained true to the idea that the sun and the moon were planets, no matter what they were called.

Definitions may change in the light of new knowledge.

[[1ponders]]

:rofl: :lol: :rofl:

[stephend]

Usually when some group wants to change the language there's some obvious political ambition behind it. You see it all the time. It can be annoying coz it's transparent manipulation but people fall for it.

In this case I can't see any covert motive, can you? Except of course that people on committees like to make sensational decisions. It's called attention seeking and even kids do it.

Pluto is about 5% as massive as Venus but it is fully half as big in terms of diameter. It's kind of spherical and it goes 'round the sun and even has its own moons - sounds like a planet to me.

IAU's definition is that a planet must clear the space around its orbit. I don't think this is a very clever definition coz how do you define "clear"?

[renormalised]

Precisely. By their definition, Jupiter isn't a planet. It most certainly hasn't cleared its orbit of debris.....how, then, do they explain the trojan asteroids in its orbit??. Nor has Mars, or Earth. So, where do we start??

This was originally a rushed decision, made by a small number of astronomers at the IAU conference after most of the delegates went home.

It should be changed.

[Ric]

I really think that the IAU boffins need to get their Tascos out and get into some visual observing, I really think that they have lost touch with everything.

Cheers

[okiscopey]

Extracts from: http://news.bbc.co.uk/2/hi/science/nature/7449735.stm

"Plutoid" is the word of the moment for astronomers.

It is the new classification that has been sanctioned for the object that was formerly known as the "ninth planet".

It is nearly two years since the International Astronomical Union (IAU) stripped Pluto of its former status as a "proper" planet.

Now an IAU committee, meeting in Oslo, has suggested that small, nearly spherical objects orbiting beyond Neptune should carry the "plutoid" tag.

As astronomy's official nomenclature organisation, the IAU must approve all new names and classifications.

Its decision at the 2006 General Assembly to demote Pluto from "planet" to "dwarf planet" caused an international furore.

(etc)

Ceres will not be considered a plutoid because of its position in the asteroid belt between Mars and Jupiter.

The classification will not placate those incensed by Pluto's demotion.

Alan Stern, a former Nasa space sciences chief and principal investigator on a mission to Pluto, was scathing in his condemnation of the IAU.

"It's just some people in a smoke-filled room who dreamed it up," he told the Associated Press. "Plutoids or haemorrhoids, whatever they call it. This is irrelevant."

[stephend]

I think you are suggesting the whole thing needs to be renormalised?!

One perspective that might help is to imagine that Pluto's orbit was between Venus's and Earth's. If that were so, is it conceivable that someone would say "Venus is a planet and so is Earth but Pluto is not"?

Another: Compare and contrast Jupiter and Earth. Are they similar in size? No. Are they similar in make-up? No. Then what do they have in common that puts them in the same "planet" category?
1) They both formed from material in sol's original accretionary disk
2) They are both egregiously big

Point (1) applies to just about everything, from long-orbit comets to asteroids. So it comes down to size.

So how do you decide whether a planet-like object is big enough to warrant calling it a planet? If there are no objective criteria, I suggest a specialist committe is not qualified to say. It becomes a "common sense" thing and you need to cast a very wide net to get a feeling of what the common sense of a thing is.

[madtuna]

So will Ceres remain a dwarf planet or will they reclassify it too?

[Dog Star]

I grew up being taught that Pluto was a planet. The decision to re classify it as a dwarf planet was not personally welcomed by me but after seeing diagrams of its orbit around the Sun as compared to the other planets, i felt compelled to admit that there was indeed something "different" about Pluto. I have in fact been trying to get used to the idea of referring to it as a dwarf planet. What I will NOT do, by God, is call it a "plutoid"!

[JonathanN]

Like others, I have a sentimental attachment to historical ideas about Pluto.

But I'm not upset by the new 'plutoid' description. It is no different to referring to Mercury, Venus, Earth and Mars as 'terrestrial planets', or Jupiter, Saturn, Uranus and Neptune as 'gas giants'. (And yes, I know there are finer distinctions regarding the gas giants, eg. 'ice giants'.)

It's just a description. :-)

Cheers,

Jonathan


Jonathan Nally
Editor
SpaceInfo.com.au
www.spaceinfo.com.au

[renormalised]

It might be a description, Jonathan, bit it's an awfully lame one!!!. Would you call the giant planets "Jovoids" or "Giantoids" or the terrestrial planets "Earthoids" or "Rockoids".....I don't think so:eyepop:

I think the guys who suggested this name for Pluto type objects were "dumboids":P:D

[Trido]

Listen to the Astronomy 161 podcast if you're so confused/unwilling to acknowledge the fact that Pluto is not a planet. It speaks at length on the differences.

Also, Astronomy is a science. Science is about challenging what you believe in and not being dogmatic. That is why Religion and Science can never peacefully coexist.

EDIT: Although Plutoid? Really dodgy IMO. I thought Dwarf Planet was fine.

[stephend]

If it isn't a planet, then obviously we can't call it a "dwarf planet".

I don't think anyone in this debate is being "dogmatic". Rather, some are challenging the criteria promoted by a certain subset of scientists.

Rather than invoking the great god "Astronomy 161 podcast", how about some actual dialectic?

By the way, science and religion very often co-exist peacefully, most notably, perhaps, in the intellect of Isaac Newton.

[Dog Star]

What a wonderfully succinct reply, Stephend.:thumbsup:
Seems to me that this debate (Status of Pluto) has a slight bias toward nomenclature as opposed to actual science, but I'll cheerfully admit that I'm a gob****e.;)

[Trido]

Next time I won't even bother.

[luvmybourbon]

We could call pluto a "claytons planet" planet when it not really a planet!
:lol:

[renormalised]

You'd be surprised at the number of astronomers who don't take any notice of what the IAU said about this matter. When you consider it was only voted upon by 250 or so delegates to the IAU Conference, and there's over 10000 professional astronomers worldwide, many of whom disagreed with the ruling, it was a bit much for the IAU to go and pronounce their decision.

Quite frankly, I think their criteria for the decision make no sense. On the basis of what they used, you could say there are no planets in the Solar System, because none of the planets fit the criteria.

Look at it this way... if they found a chunk of rock and ice out there as large as the Earth (which is always on the cards), what would you call that?? A Plutoid??!!!........hardly. That would be ridiculous. It'd be a planet, pure and simple.

[TrevorW]

Oh drats how do you think Mickey, Donald and Goofy are going to feel about this.

;)

[stephend]

That's more than I would have thought. Where does that figure come from?

Things like this aren't usually decided by a vote; you'd expect it to be thrashed out at length in journals. Maybe it was?

[renormalised]

Came from a press release of the IAU's about their decision. Nope, the whole shebang was done at the conference. They had 3 discussion panels and the usual side discussions, but that was where it was done. Then, after most of the guys went home, it was put to the vote, with about 250-300 delegates who were left there voting on it. There may have been references to changing Pluto's status in some journal papers, but no real knock em down, thrash it out discussion.

[Geoff45]

If Pluto's orbit was between Venus and Earth, it might be a planet, if Ceres was between Venus and Earth it might be a planet and if my auntie had balls she would be my uncle.
A small object that is the major body in its neighbourhood obviously is different from a small body that is one of many similar objects in similar orbits.

By the way, why is nobody getting uptight about the fact that Eris (http://www.gps.caltech.edu/~mbrown/planetlila/)is not a planet. It's bigger than Pluto and it has a satellite, so if people want to include Pluto, then they also have to include Eris, or is there some "logic" which gets around this?

[Trido]

Logic does not come into this situation. There are those that passionately believe that Pluto is a planet and those that agree that it is too different to fall under the same category.

[stephend]

Actually, if my hypothetical near-Earth-orbit Pluto enjoying the classification "planet" was moved out to Pluto's present orbit, it would be, by definition, exactly the same. Its neighbourhood changes, granted.


I think it's just that Eris was discovered recently, while Pluto has been around all of our lifetimes. You're right, the logic is the same.

The discovery of Eris and a couple of other planets or plutoids of similar size has raised the spectre of a possible endless series of smaller and smaller planets, which has produced a cold sweat on many a brilliant brow. But necessity, the mother of invention, bless her, borrowing from taxation departments, has come up with the answer: a cut-off point.

Of course, to put a kilogram figure to it might sound pompous and arbitrary, so mass has been re-defined as "ability to clear one's neighbourhood" (not something we should aspire to).

The folly of this seems to me three-fold:
1) You'd never get a dinosaur to vote for it, nor any human who has an inkling of how likely we are to be smashed by one of the thousands of near-earth-orbit asteroids constantly whizzing past our neat, cleared corner of space.
2) IAU is careful to say their definition does not apply outside the solar system. That's because when we find planets orbiting other stars we haven't got a clue how clear their neighbourhoods are. Unfortunately, the same applies to the outer reaches of the solar system.
3) Clearing your neighbourhood takes time. Thus if we accept the definition, all we can say is that Pluto is presently not a planet, but may be when it has done some more clearing. This will at least amuse the angels.

These disputes arouse a herd instinct in all of us. They can descend into pure emotion. I object to the word logic being held up and waved like a talisman by either side. If you have a view, work it out, then write it out.

[Geoff45]

I think one of the main problems in the IAU definition of a planet is the one that refers to "clearing the neighbourhood". Quite obviously, no planet has completely cleared its neghbourhood. That's partly why we see meteors. Even mighty Jupiter has the Trojan asteroids in its orbit. However, the situation with the first eight planets out from the sun is quite clearly different to the situation in the Asteroid belt, which is what I think the IAU were trying to capture. The problem is where do you draw the line? This is what I think needs to be clarified.
The situation beyond the orbit of Neptune is again different but similar to the asteroid belt and so IMO the objects there are distinguished from the currently recognised 8 planets and so deserve to be classed differently.

As for plutoids--it makes sense. In fact, more sense than asteroid: asteroid (star-like), plutoid (pluto-like). It may even sound natural in 20 years time.
Geoff

[skeltz]

What !!!..i thought pluto was a cartoon character:P:P

[Chrissyo]

I think the idea is that the Trojan asteroids exist where they exist because of Jupiter. Similarly with other 'trojan asteroids' around other planets, corkscrew asteroids, etc.

It seems to me that there is a fair distinction between the asteroid belt/Kuiper belt (where Ceres and Pluto/Eris are found respectively) and the sample of other objects that can be found interacting with the planets.

"Having cleared its orbit" isn't a very clear definition, but I think it does make sense.

:shrug:

[Trido]

I think the clearing its orbit thing refers to the bombardment that the planets underwent during its early evolution. These still occur because there is always junk coming into and out of the inner solar system, but no where near to the extent that it used to. When you look at close by objects, dating has put heavily cratered areas in the vacinity of several billion years of age whereas the less cratered areas generally show that geology or other unusual things have renewed the surface of the object.