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haku
17-08-2006, 01:05
When Pluto was discovered in 1930, it was thought to be a one of kind anomaly, a small icy planetoid lost in the outer regions of the solar system. One common theory to explain its existence was that Pluto may have been a satellite of Neptune that had gone rogue. For those reasons (small size, possibly an escaped satellite), many scientists at the time thought that Pluto should not be considered a planet, but a majority of astronomers decided otherwise and Pluto became officially the 9th planet.

At the end of the 20th century with the invention of more powerful instruments, astronomers realized that Pluto was absolutely not an 'anomaly', it was discovered that Pluto is actually part of what is called the Kuiper Belt, a large ring of thousands of objects orbitting the outer regions of the solar system. In recent years, several planetoids totally similar to Pluto (though smaller) have been discovered in the Kuiper Belt, starting the debate on whether those new objects should be considered planets or not.
Finally, last year, a new Kuiper Belt object named 2003 UB313 was discovered. This one being significantly bigger than Pluto, the number of planets in the solar system had to be revised, it was impossible to keep Pluto (officially part of the Kuiper Belt) as a planet while not giving the status to a similar bigger object.

The IAU (International Astronomical Union) is currently meeting in Prague and will officialize the new definition of 'planet'. The definition has been made as simple as possible:

The part of "IAU Resolution 5 for GA-XXVI" that describes the planet definition, states "A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."

According to that new definition, the Solar System will now have 12 planets, the 3 new ones are:
Ceres, an object in the Asteroid Belt between Mars and Jupiter.
Charon, originally considered a satellite of Pluto but now regarded as forming a twin planet with Pluto.
2003 UB313, which is obviously a temporary designation, what is to become the 12th planet will receive an official name probably later this year.

Picture of the new Solar System. (http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601a.html)
Picture of the 3 new planets. (http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601b.html)

Full IAU press release. (http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html)

All scientists agree that many more objects fitting the new definition of planet will be discovered in the Kuiper Belt in coming years, so the Solar System will likely expand to 20 or 30 planets.

It is to be noted that the 'classical' 8 bigger planets are considered a special class of 'major planets', Pluto on the other hand is grouped with the other Kuiper Belt planets. So to make it simple, the general public can consider that there are 8 [major] planets (that won't change), and 4 minor planets which will be joined by many others in the coming years as the Kuiper Belt is being explored.

the unforgiven
17-08-2006, 01:16
awesome news !!

Charon, originally considered a satellite of Pluto but now regarded as forming a twin planet with Pluto.
Charon like the finnish goth-metal band? woooow

it's amazing to know that we live at the same era of the discovery of new planets in our solar system

haku
17-08-2006, 01:25
Charon like the finnish goth-metal band?Charon like the Greek-Roman god (http://www.gods-heros-myth.com/godpages/charon.html), but i'm guessing that band got its name from that same god. :)

It's always been customary to name planets afer Greek-Roman gods, the modern IAU hasn't changed that, the new planet 2003 UB313 will also be named after a Greek-Roman god.

thegurgi
17-08-2006, 01:47
Wow, this is just... WOW... it shows how something you always thought you knew was correct can change in an instant... charon is a Planet on par with Mercury, Venus and Earth..and not a moon... quite an upgrade eh?

wow...this turns my world Topsy Turvey... the Planets was one of those Static peices of info that didn't change... and now it has.

I'm glad to see Ceres reaching full planet status, Ceres was such an under-rated goddess

QueenBee
17-08-2006, 02:40
Oh my, what a surprise :D It's like when people realized the earth isn't flat!

nishershevone
17-08-2006, 07:01
it's a great news really...can you tell me who are the founders of those new planets? and what will happen if earth will fall...where do you think we will go...?

haku
17-08-2006, 13:41
Wow, this is just... WOW...Yeah, this is pretty exciting. :D I've been following this debate since they realized that 2003 UB313 was actually bigger than Pluto, i knew it would force the IAU to revise the planet classification, astronomers had been in a deadlock over what is or is not a planet for far too long.
I'm glad they've taken the simple approach: 'anything perfectly spherical that orbits a star is a planet', simple, clear, and efficient. And it's about time we had an official definition of planet since we are currently discovering many planets orbiting neighboring stars as well.

can you tell me who are the founders of those new planets?Ceres (http://en.wikipedia.org/wiki/1_Ceres) was discovered by Piazzi in 1801, it was first considered a planet, but when they realized how small it was, they downgraded it to asteroid. Under the new IAU definition, Ceres will regain planet status.
Charon (http://en.wikipedia.org/wiki/Charon_%28moon%29) was discovered by Christy in 1978, it was first considered a satelitte of Pluto but later observation showed that Charon is not a satellite. A satelite is an object that orbits another object, the center of mass being located within the orbited object; but Charon does not orbit Pluto, Charon and Pluto orbit each other around a center of mass located in space between the two of them, the IAU now considers this to be a binary planet.
2003 UB313 (http://en.wikipedia.org/wiki/2003_UB313) was discovered by Brown, Trujillo and Rabinowitz in 2003, this one is brand new and is to become the 12th planet.

what will happen if earth will fall...where do you think we will go...?I'm not sure what you mean by that, when Earth will be destroyed? Well, the Sun still has 4 billion years of life, that's plenty of time for humanity to develop interstellar ships.
Warp/hyper drive allowing us to travel faster than light will probably be invented in a century or two, and we won't even have to explore space blindly to look for terralike planets, astronomers are confident that in a few decades new powerful telescopes will allow us to directly observe small planets in the neighboring star systems. We will discover terralike planets long before we actually have the technology to go there, and when we do, we'll know exactly where to go to found new colonies.


Also, i personnaly think that the terraformation of Venus is possible, which would give us a second habitable planet right in our Solar System. Many people also think that Mars could be terraformed, but i think Venus is a more likely candidate, it's almost the same size as Earth (Mars is much smaller) and it has an atmosphere we can work with (Mars almost has none).
Picture of what a terraformed Venus (http://en.wikipedia.org/wiki/Image:TerraformedVenus.jpg) would look like. :D

mulder
17-08-2006, 16:55
Just to note, this has not actually been agreed yet. The vote will take place on 24 August.

See the IAU website here (http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html)

If the resolution is passed, I will be slightly sad, as the IAU will then give 2003 UB313 a "proper" name, rather than leaving it with the unofficial name of Xena (http://mikes-images.co.uk/scans/xenascans/pages/xena_mq_2011n.htm) (which they would probably do if it was not considered a planet). Still, whatever they call it, I will always call it Planet Xena and it's satellite Gabrielle (http://mikes-images.co.uk/scans/gabscans/pages/gabrielle_mq_2035n2.htm) :)

Argos
17-08-2006, 19:24
What IAU does now is, simply stupid. The definition that everything that has a round form will be a planet is absolutely ridiculous. From planetogenesis we have a good view what's a planet and what not. We have the rocky inner planets (4 of them) and a ring of rocky debris (Asteroids), which are not called planets, and gaseous outer planets (4 of them) and at least one ring of icy debris from the formation of the outer planets. That Pluto was supposed to be a planet too, was an error of the astronomers who, until the middle of the seventies believed that Pluto is as large as the earth.
If this proposal will be accepted we will have an inflation of 'planets' and nobody will know the correct number of them.
Let's see what we have today. In the Asteroid belt there is Ceres and with Pallas and Vesta (diameter over 500 km) two additional bodies which are on the verge of being 'planets' in this definition. Objects of the Kuiper belt would need no more than 400 km. The already known 1000 km circus of objects there is Pluto, Charon, Sedna, Quaoar, Ixion, Varuna, 2003 UB313, 2003 EL61, 2006 FY9, 2004 DW and I won't continue with all the others larger than 400 km.

Warp/hyper drive allowing us to travel faster than light will probably be invented in a century or two...
There are only two problems to be solved:
1. If you reach light velocity you create your own Black hole, so you will be crushed to singularity.
2. If you are beyond light velocity you have left our universe, because it is defined and restricted by light velocity.

...astronomers are confident that in a few decades new powerful telescopes will allow us to directly observe small planets in the neighboring star systems.
If you want a picture of an earth like planet in good resolution, let's say 1000 x 1000 pixels you need only a telescope with a mirror of more than thousand kilometers.

Also, i personnaly think that the terraformation of Venus is possible, which would give us a second habitable planet right in our Solar System.
Here we have a little problem too. Venus has no water. Keeping in mind earth history, even the water content of the earth is very low for maintaining a stable climate. So, all you need is, take a water satellite like Tethys from the Saturn system, carry that thing to Venus, let it explode and pour the debris over Venus.

Good luck with your future plans, haku!

dradeel
17-08-2006, 19:56
There are only two problems to be solved:
1. If you reach light velocity you create your own Black hole, so you will be crushed to singularity.
2. If you are beyond light velocity you have left our universe, because it is defined and restricted by light velocity.
Also, the energy needed to put the given ship in the speed of light will probably take all the energy in the universe. There's a bigger chance we'll discover teleportation or that there are actually leap-holes in the universe so that we can "jump" from one place to another. But that's not very likely either. Hehe.
I will always call it Planet Xena
Aaah, yes. The good ol' Planet X. :D They should definetaly keep that name either way. It suits both gamers and tv-people. Hehehe. *Thinks back on the days of NES and the game Galaxy 5000*

Rachel
17-08-2006, 20:34
Am I the only one who has absolutely no interest in space? :laugh:

mulder
17-08-2006, 20:55
There are only two problems to be solved:
1. If you reach light velocity you create your own Black hole, so you will be crushed to singularity.
2. If you are beyond light velocity you have left our universe, because it is defined and restricted by light velocity.


There is also the slight problem of getting to the speed of light in the first place, as shown in this quote from here (http://en.wikipedia.org/wiki/Faster-than-light)

To accelerate an object of non-zero rest mass to c would require infinite time with any finite acceleration, or infinite acceleration for a finite amount of time.

Either way, such acceleration requires infinite energy. Going beyond the speed of light in a homogeneous space would hence require more than infinite energy, which is not a sensible notion.

As for terraforming Venus, good luck. At the moment, Venus has a surface temperature of 400 degrees C, a surface pressure 90 times that of Earth, and clouds consisting mainly of sulfur dioxide and sulfuric acid droplets. The surface also melts and reforms every 100 million years.

Not my ideal retirement home :D

haku
17-08-2006, 21:22
And there was a time when people were saying that escaping Earth's gravity will never be possible because it would require more energy than it was possible to produce… And there was a time when people were saying that going faster than the speed of sound will never be possible because no material would ever be strong enough to resist to the shock wave… And there was a time when people were saying that building an heavier than air flying machine will never be possible because anything heavier than air can't fly… And there was a time when people were saying that travelling above 100km/h will never be possible because human organs would be crushed by the air pressure…

At any given time in human history there are always people who say that this or that will never be possible, and yet it becomes possible a few centuries later. It's because those people try to imagine a future technology within the box of what is known at their time, they do not make a leap of imagination, fortunately there are also people who think out of the box, elaborate new theories, and make scientific breakthroughs, rendering possible what was thought impossible.

I am convinced that it will be possible one day to build a faster-than-light ship, i am also convinced that such a ship won't rely on anything known today, it will use materials that haven't been invented yet and will rely on scientific principles that haven't even been theorized yet. I am confident that sience will make major breakthroughs in the way we understand matter, energy, and time and the way they are interraleted, and those discoveries that have yet to be made will render faster-than-light travel possible. And there will be a time, be it in 100, 500, or 1000 years, where the statement that faster-than-light travel is impossible will look as ridiculous as the statement that anything heavier than air can't fly looks ridiculous to us today.

forre
17-08-2006, 21:24
There are only two problems to be solved:
1. If you reach light velocity you create your own Black hole, so you will be crushed to singularity.
2. If you are beyond light velocity you have left our universe, because it is defined and restricted by light velocity.
Yep, the modern physics states such. Modern physics doesn't even know a complete structure of the Universe. They are still arguing on cosmic Constanta, spiral models and god-knows-what. The main problem of the hyper speeds will be friction. Not generally but since density of material is higher than density of light particles, it could be a problem.

On the other hand, I personally don't care if they class the found bodies as planets or as asteroids. They are still there and worth to be studied.

Argos
17-08-2006, 21:29
At the moment, Venus has a surface temperature of 400 degrees C, a surface pressure 90 times that of Earth, and clouds consisting mainly of sulfur dioxide and sulfuric acid droplets. The surface also melts and reforms every 100 million years.

Not my ideal retirement home :D
Don't be so negative. There is a simple way to alter the situation there. It's the same principle as with the transformation of burnt lime to limestone. First apply water to the surface, all Magnesia and Calcium oxide change to hydroxides. These can bind carbon dioxide, you get limestone and the water is set free. When all CO2 is consumed you have only about 3 bar and after some time quite acceptable temperatures. The water vapor will wash out the sulfuric components and deposit them as gypsum. Easy task, if you get enough water there!

At any given time in human history there are always people who say that this or that will never be possible, and yet it becomes possible a few centuries later.
Don't get me wrong here, I don't say it's impossible, but I'm quite convinced that the problems are so huge that ther will be a very loooooooong time, that any of these problems can be solved, if ever.

freddie
17-08-2006, 21:41
Gah. What a mess. The Kuiper Belt ha always looked fishy to me and it made Pluto's reign as a stand alone outer planet on shakey grounds. Fact is most scientists suspected there's a high possibility of bigger shaped objects beyond Pluto for a long time but didn't want to deal with technicalities. If you ask me there's an easy solution to this - since we're redifining the definitions lets do a thorough job at it - only objects that pass a certain diameter can be considered planets, while others remain planetoids. That would prevent the needless inflation of known planets as we discover the Kuiper Belt further. My personal preference is to just keep the status quo and have 9 planets which we all know and love. There are thousands of annomalies in astronimy, this could be jsut another one.

I really don't believe we'll ever develop warp/hyper-drives or anything of the nature since the law of nature telling us that light-speed is unachievable seems extremely firm. Mathematics pretty much proved it's a brick wall. And those worm-holes bending space...yeah sure they exist. But they're not exactly hallways through which you can just waltz through. In order to curve the time-space constant you have to apply ridiculous amounts of energy - we're talking millions of millions °C coupled with endless Nms pressure - any functioning worm-hole out there would therefore be pretty hostile to it's "users": a space ship would enter it and emerge on the other side completely annihilated in the form of basic particles - not even atoms, but rather electrons and quarks.

About Venus: eventhough it's Earth's cousin (smaller than Earth by just a few hundred kilometres in diameter) it can't be mankind's final destination, even if it did have water. Simply because it's even closer to the sun than we are (which accounts for most of it's woes today), so when the sun explands into a giant supernova a few billion years from now it's entire orbit will be swallowed up along with Mercury's. So Earth (and possibly Mars) will still be our springboard towards teh stars.

haku
17-08-2006, 23:26
since we're redifining the definitions lets do a thorough job at it - only objects that pass a certain diameter can be considered planets, while others remain planetoids.
The problem is that such a limit would be totally arbitrary and would lead to endless debate. Don't get me wrong, personally i was in favor of the 4-class proposal, 1 class for the 4 terrestrial planets, 1 class for the 4 jovian planets, 1 class for the Asteroid Belt objects, and 1 class for the Kuiper Belt objects, in that proposal Pluto was downgraded to a Kuiper belt object. Unfortunately there were not many astromomers who supported that idea.

There was a proposal with a fixed diameter limit, that limit was 2000km, which didn't solve anything since 2003 UB313 is well over the limit, and several other Kuiper Belt objects of similar or even bigger size will probably be discovered. And setting a higher limit was unpopular among astronomers since that would have meant downgrading Pluto.

You'll notice though that in the proposal that is most likely to be adopted, the IAU makes a difference between 'major planets' and 'pluton planets' (Pluto being obviously part of the latter), and from what i've read, astronomers are also starting to use the term 'dwarf planets' for anything smaller than the 8 classical planets.
So in a way, it's a 2-class system that is being created, 1 class for bigger planets alone on their orbits, and 1 class for smaller planets belonging to debris belts.
So like i said in my first post, the general public who always want simple things can consider that there are only 8 (major) planets, plus a 'certain number' of dwarf planets that will keep growing in the coming years, which is not such a problem since the general public doesn't really care for smaller planets.

This Wikipedia page (http://en.wikipedia.org/wiki/Pluton_%28astronomy%29) explains how planets will be categorized… In any case, it is clear that the 8 major planets are set apart, and that Pluto is moved to a subcategory that will likely contain tens of dwarf planets.

mulder
18-08-2006, 16:56
I agree the "two class" system is most likely to be adopted. It's fairly simple, even for those who have no interest, and the only drawback is downgrading Pluto to "pluton" or "dwarf planet". But I guess everyone will get over that in due course.

Argos I'm not being negative, just realistic :) Anyway, by the time mankind develops a suitable method of terrforming Venus, they'll be able to reach other planets that won't need terraforming, so the whole thing will be moot. Although I think it would be easier to terraform Mars.

haku While it's true that many things have been deemed impossible, only to become reality later, the problem with FTL flight is that it has been shown to be mathematically impossible, which is a whole different thing. You would need a fundamental change in physics, or the discovery of a whole new branch of physics to bring it about. I'm not saying fast travel to other planets and solar systems is impossible, just that it's going to need something very different to get us there. In the meantime, we have to be looking at generation ships if we want to move to other worlds.

the unforgiven
18-08-2006, 18:09
I read on a french forum that they want to call 2003 UB313 --> Xena !!
woooow it's so funny :p like the old tv show LOL

what do you think about that name?

haku
18-08-2006, 18:22
I read on a french forum that they want to call 2003 UB313 --> Xena !!No, Xena is a temporary nickname given to the planet by the discoverers, but it won't be the final one, planets must be named after a Greek/Roman deity. :)

Argos
18-08-2006, 21:05
No, Xena is a temporary nickname given to the planet by the discoverers, but it won't be the final one, planets must be named after a Greek/Roman deity. :)
Not quite correct!

Summary of Guidelines (pre-2003)

* Discoverers have the privilege to propose names for ten years after numbering. Beyond that point, others may propose names.
* Names must be pronounceable, preferably expressible as a single word, and no more than 16 characters in length.
* Individuals or events principally known for political or military activities are unsuitable until 100 years after the death of the individual or the occurrence of the event.
* Names of pet animals are discouraged.
* Minor planets in certain dynamical groups should be named within more restrictive guidelines. For example,
o Trojan asteroids (those that librate in 1:1 resonance with Jupiter) are named for heroes of the Trojan War (Greeks at L4 and Trojans at L5).
o Trans-Jovian planets crossing or approaching the orbit of a giant planet but not in a stabilizing resonance are named for centaurs
o Objects crossing or approaching the orbit of Neptune and in stabilizing resonances other than 1:1 are given mythological names associated with the underworld.
o Objects sufficiently outside Neptune's orbit that orbital stability is reasonably assured for a substantial fraction of the lifetime of the solar system are given mythological names associated with creation.
o Objects that approach or cross Earth's orbit are given mythological names.
* Any decision of the CSBN with which a proposer disagrees may be appealed by the proposer. Since the CSBN now reports to Division III, that appeal should be addressed, by electronic mail or by letter, to the president of Division III, for action by the membership at the following General Assembly.
* The CSBN may choose to act on its own in naming a minor planet and has traditionally done so in each case in which the number is an integral number of thousands.

Mary-sheccid
18-08-2006, 21:23
wow°!
:cool:


xena? the war´s princess? lol! i love it! :D
a new planet! we go to choose the planet´s name!

i choose MARY!:)

Is the name of the god´s mother (Jesucristo) i like it? what do your think?

WE PROPOSE OTHERS?

thegurgi
18-08-2006, 21:46
I personally think they should name it Vesta or Juno (keeping with the Roman 12 theme, well... other than Saturn and Uranus). Ooo, maybe Juventas

haku
18-08-2006, 22:44
I personally think they should name it Vesta or JunoUnfortunately those names have already been attributed, here's the official list of all the named objects (http://cfa-www.harvard.edu/iau/lists/MPNames.html) in the Solar System (except planets and satellites).
One of my favorites has to be Marsupilami, haha. :p

mulder
18-08-2006, 23:08
Xena was indeed used as a code name by the discoverers, who were fans of the show, but they have not submitted it as a proposed name.

Lucy Lawless and Renee O'Connor were both told about the code names back in October 2005 and were thrilled. Lucy's reaction was:

Everytime Sam Raimi hassles my husband, Rob Tapert, about loving making television so much I say, "Aww gee, Sam, is there a planet named Superman? I DON'T THINK SO!!!!" I rang Mike Brown at Cal Tech today to thank him for this senseless act of beauty. Fancy naming a planet and her moon after your characters?! That is just craazy! Renee was at my house yesterday and Sam too and we were all just in disbelief. I had heard 'Xena' was the unofficial name, but didn't dare hope it would stick. God bless us all. That's just CRAAAZY!!!

haku
18-08-2006, 23:35
Xena would be accepted as the name of a minor object actually as it's not been used already, but no way the IAU would accept it for a pluton. :p

There's also a Mr Spock in that list of minor objects, excellent. :gigi:


I was also reading that astronomers estimate that 53 of the currently known Kuiper Belt objects are big enough to be spherical and therefore granted planet status, and they're expecting to find at least 50 more, so we should get over 100 plutons in the near future.
The more the better actually in my opinion, with a whole lot of plutons, it will be easier to forget about Pluto and Charon which will only become unremarkable objects in a very numerous class of objects, that will only emphasize the remarkable nature of the 8 major planets.
I can see encyclopedias in a few years having sections for each of the 8 major planets, and then a section for the 100 or so plutons.

mulder
19-08-2006, 10:43
Yep, from a purely selfish point of view, I would prefer it if the IAU decided there were 8 planets and everything else was not a planet. That way we would get to keep Xena :D

The winners in all this are going to be book printers. They'll be doing reprints every year to update the latest plutons and raking in the cash from schools and the scientific community :rolleyes:

simon
21-08-2006, 00:28
Pluto may yet lose its planet status:

http://www.newscientistspace.com/article/dn9797-pluto-may-yet-lose-planet-status.html

I hope the rival motion defeats the official IAU proposal. I don't want to have at least 53 planets by the end of next year. People should accept that calling Pluto a planet in the first place was a mistake, it's just a biggish Kuiper Belt Object.

The whole idea of defining a planet as being round seems particularly absurd to me when 2003EL61 ("Santa"), which is the next largest known KBO after 2003UB313 ("Xena") and Pluto, three-quarters the size of them, is cigar-shaped because it rotates once every four hours. Would 2003EL61 be a planet or not? The IAU won't say, they want to put it on a watch list. Won't it be crazy if they decide it's not a planet, but 43 smaller objects are planets? But if they decide it is a planet, that would make the new 'planets are round' rule a bit meaningless.

Yep, from a purely selfish point of view, I would prefer it if the IAU decided there were 8 planets and everything else was not a planet. That way we would get to keep Xena :D

There's no chance Xena will be the official name. The discoverers have already submitted a name to the IAU, which is awaiting a final decision on 2003UB313's official status. They were told off by the IAU for revealing the name Sedna for an earlier discovery.

haku
21-08-2006, 14:19
Pluto may yet lose its planet status:

http://www.newscientistspace.com/article/dn9797-pluto-may-yet-lose-planet-status.htmlThat's an interesting counter proposal.

All i'm hoping at this point is that Pluto will be finally put in the right class, either we have 8 planets, or we have 50, but 9 is ridiculous as there's no reason to single out Pluto like that.

simon
21-08-2006, 19:32
The IAU is now going to break the two rival proposals down and vote on each part, in an attempt to create a compromise:

http://www.newscientistspace.com/article/dn9811-planet-vote-to-draw-from-rival-definitions.html

The alternative proposal is given here:

http://www.space.com/scienceastronomy/060819_new_proposal.html

The alternative proposal still creates a class of 'dwarf planets', but it distinguishes them from planets, which are "by far the largest object in its local population". It doesn't call trans-Neptunian dwarf planets 'plutons' (the word is already used by geologists for something completely different) and it keeps Charon a moon.

The IAU top brass seem to have recognised that the name 'pluton' and making Charon not a moon are very unpopular and I suppose they hope to save Pluto's status as a planet by separating off those aspects of the offiicial proposal.

I hope the alternative proposal is passed, but even the concept of 'dwarf planets' is flawed because whether an object is a spheroid or irregular depends on the material it is made of as well as its size, so smaller objects made of ice can be dwarf planets, but larger and much more massive objects made of rock won't be. See the table in this article:

http://en.wikipedia.org/wiki/Definition_of_planet

haku
21-08-2006, 19:57
^ Thanks for the articles.

And LOL, i was not aware that English speakers find the word 'pluton' so ridiculous and laughable… It's how Pluto is called in French :laugh:

simon
22-08-2006, 21:29
Big news! Astronomers are now leaning towards just eight planets:

http://www.newscientistspace.com/article/dn9818-astronomers-lean-toward-eight-planets.html

LOL, i was not aware that English speakers find the word 'pluton' so ridiculous and laughable… It's how Pluto is called in French :laugh:

I thought the main objection was that 'pluton' was a term in geology, rather than that people found the name laughable. There are already 'plutinos' - objects that have a similar orbit to Pluto - and 'cubewanos' - objects in the main Kuiper Belt which unlike Pluto don't have orbits in resonance with Neptune, after the first discovered, 1992QB1. I think cubewano is a slightly ridiculous name. But the latest from Prague is that the names pluton, plutoid, plutonoid and plutid have all been rejected. 'Plutonian object' met with less opposition, which does suggest a preference for formality among the IAU members.

haku
22-08-2006, 22:31
Big news! Astronomers are now leaning towards just eight planets:

http://www.newscientistspace.com/article/dn9818-astronomers-lean-toward-eight-planets.html
Thanks for the article.

This is pretty exciting news, the new proposal seems fine to me, 8 planets and dwarf planets or planetoids for the other smaller spheroids, i think that works well and is easily understandable by everybody. Hopefully this proposal will pass.
As for creating a special class of Plutonian objects, it seems a bit redundant with Kuiper Belt objects but why not, if this is what it takes to put Pluto where it belongs, it's really not a problem.

simon
23-08-2006, 12:07
There's more on what happened at the IAU meeting yesterday in this morning's New York Times (requires regstration):

http://www.nytimes.com/2006/08/23/science/space/23pluto.html

It seems pretty definite that Pluto is a goner as a planet. The NYT suggests that 'plutonians' is now the favoured name for trans-Neptunian objects. It's less of a mouthful than 'Plutonian objects'. It will be a bit confusing that an object can be a plutonian without being a plutino, but the term KBO is clunky, so plutonian would be better.

Although I was critical of the 'dwarf planet' definition, I think there is a need for an intermediate category, smaller than planets, but bigger than mere asteroids. Pluto used to be the only one, but now there are quite a number. It's also become apparent that Ceres, the biggest asteroid between Mars and Jupiter, is big enough to have some planet-like characteristics (it's spherical and has distinct layers, possibly even a water ocean beneath its surface like Europa and Enceladus) and I agree it should have a distinct status. The difficulty is drawing a boundary that seems consistent in how it treats bodies made of different materials. But Saturn's moon Enceladus shows the problem. It's only 500km across, slightly smaller than Pallas and Vesta, which aren't even properly round, yet it's nothing like the other small objects in the solar system. The body it most resembles is Europa, which is 3000km in diameter, and it has some similarities with Triton and possibly Xena, which are both also much bigger. Some objects act much more grown up than others the same size.

simon
24-08-2006, 15:33
The IAU assembly has just finished voting - Pluto is no longer a planet.

They created a new category of dwarf planets including Pluto. Pluto and the other dwarf planets aren't planets - there are just the eight planets out to Neptune. Pluto is the prototype of a new category of trans-Neptunian dwarf planets, but the proposal that they be called 'Plutonian objects' was narrowly defeated. The IAU executive will come up with a new proposal for what to call them.

mulder
24-08-2006, 15:35
Pluto has lost it's status as a planet. The IAU has adopted a resolution to retain the 8 classical planets and reclassify Pluto as a dwarf planet.

http://news.bbc.co.uk/1/hi/world/5282440.stm

As all fans have known for years, Xena is a god killer and this proves it :)

Edit: damn, beaten to it by 2 minutes.

The IAU resolutions and planetary definitions can be found here (http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html).

haku
24-08-2006, 16:13
Thanks for the great news guys! :D Wow, considering the proposal we started with last week, i really didn't think we would end up with *less* planets, this is great, i'm very glad Pluto was finally put in the right category.
The creation of a 2-class system with planets and dwarf planets was definitely the best decision, but again, when i read the first IAU proposal last week, i really didn't think that this would be the final results.
This is great! *goes for a drink to celebrate*

dradeel
24-08-2006, 16:17
Wow, considering the proposal we started with last week, i really didn't think we would end up with *less* planets
I was actually guessing this would be the outcome of it. It was honestly the best and easiest solution. And it was something that should've been done from the beginning of :)

freddie
24-08-2006, 18:17
Bah. Too bad. I thought nostalgia would win them over.

Actually one might say now that Mercury is a dwarf planet as well - I'm sure there are many planet like objects in the kuiper's belt which are bigger than Mercury & Pluto combined.

haku
24-08-2006, 18:38
Actually one might say now that Mercury is a dwarf planet as well - I'm sure there are many planet like objects in the kuiper's belt which are bigger than Mercury & Pluto combined.
Possible, but the planet definition requires that a planet must have cleared its orbit of other objects, and Kuiper Belt objects no matter how big they are have obviously failed to do so since they are part of a *belt*, Mercury on the other hand is alone on its orbit.

fanoff
24-08-2006, 18:46
there shouldnt be something like that according to me.im not talking about its scientific statement but i think little kids have been taught that there are 9 planets and its hard to get this info out of their minds.anyway its good to know that!!:D

simon
25-08-2006, 00:59
Bah. Too bad. I thought nostalgia would win them over.

Actually one might say now that Mercury is a dwarf planet as well - I'm sure there are many planet like objects in the kuiper's belt which are bigger than Mercury & Pluto combined.


Aside from the definitional point Haku made about being the dominant body in its region of space, Mercury is a lot bigger than Pluto or Xena. It's over twice the diameter, eight times the volume and 25 times the mass. Mars is only about 40% wider than Mercury and twice the mass. Two moons in the solar system - Ganymede and Titan - are slightly bigger than Mercury, but they have less than half the mass. Mercury is a more substantial object than any of the moons in the solar system. Pluto is smaller and less massive than all seven big satellites in the solar system - Ganymede, Titan, Callisto, Io, the Moon, Europa and Triton. Pluto has one-sixth the mass of our Moon.

It's unlikely that there's anything else much bigger than Xena in the Kuiper Belt - Mike Brown's surveyed most of the sky now and anything bigger would have to be in an even more inclined orbit than Xena.

There may be Earth or Mars sized planets much further out than the Kuiper Belt. There are two theories of planet formation. One, the disc instability theory, says that the giant planets formed very quickly out of instabilities in the disc of gas that surrounded the Sun as the solar system formed. It says there should be no big objects beyond Neptune. The other, the oligarchic theory, says that there were about 60 objects that formed and then collided together to create the planets we know. But in computer simulations several Mars to Earth-sized objects have near-misses with Jupiter and get thrown by its gravity into very distant and wild orbits. Neptune and Pluto are about five billion kilometres from the Sun. Sedna is about fifteen billion kilometres from the Sun (100 times as far as the Earth, or 100 Astronomical Units) and its orbit takes it out to about 150 billion kilometres (1000 AU). It's predicted that these planets, if they exist, will be somewhere between 1000 AU and 10 000 AU. Current telescopes can't find them, but there are plans to build an 8.4 metre telescope to scan the sky for them. If they exist, they'll be real planets, not minnows like Pluto. Maybe there are only 8 planets in the solar system, but maybe there will turn out to be twice as many - real planets. We'll be glad we didn't proclaim planet 9 to planet 90 to be tiny ice balls.

haku
26-08-2006, 02:19
Actually one might say now that Mercury is a dwarf planet as well - I'm sure there are many planet like objects in the kuiper's belt which are bigger than Mercury & Pluto combined.
Michael Brown, discoverer of 2003 UB313 and supporter of the 8-planet proposal, has published a clear explanation on his web site (http://www.gps.caltech.edu/~mbrown/) (click on The eight planets: an explanation).
It is to be noted that if the original IAU proposal had passed, Michael Brown would have become the discoverer of 15 planets (and probably more as his work is not done), so the man is to be applauded for putting science before his personal glory.
However, he is now the discoverer of the biggest dwarf planet, and he hopes that 2003 UB313 will *at long last* gets its final name very soon now that the planet definition has been revised.

freddie
26-08-2006, 12:32
It's unlikely that there's anything else much bigger than Xena in the Kuiper Belt - Mike Brown's surveyed most of the sky now and anything bigger would have to be in an even more inclined orbit than Xena.

Which still IS possible. What if there are a whole bunch of planetoid objects the size of Mercury or above under all kinds of weird orbital angles. Will that all for a yet another redefinition of the solar system as we know it? I just want something more permanent, if we're already redefining things.

There's also a question of other large onjects that might be found BEYOND the Kuiper Belt. Surely the gravitational pull of the sun extends far beyond what we know now as our solar system.

simon
26-08-2006, 15:13
It's very unlikely that anything as big as Mercury exists in the Kuiper Belt because it would be eight times bigger than Triton, Xena and Pluto (Triton is Neptune's largest moon, but it's a captured KBO, slightly larger than Xena and Pluto). There certainly aren't going to be 'a whole bunch' of them that all happen to be at the celestial poles at this point in their super-inclined orbits. The fact that the three largest KBOs found even after most of the sky has been surveyed are all about the same size actually suggests that the biggest that objects formed in that region could grow to was about that size, just like there are physical reasons why Ganymede and Titan are as big as icy moons can grow.

Read Michael Brown's explanation that Haku pointed a link to. It would be a nonsense to classify Pluto and Xena, let alone dozens of smaller objects, as planets when they're just the largest members of a population of small bodies. Mercury is much bigger and it's not much smaller than Mars. It isn't part of a population of small objects like they are, it's the smallest of the big objects. Mercury is 25 times more massive than Xena and Pluto. It's several times more massive than the entire Kuiper Belt. It's the obvious place to draw the line. If something as massive as Mercury is found in Kuiper Belt, it should be a planet, but I'd bet money that one won't be. What's your problem?

I'd already discussed the possibility of finding big, planet-sized objects beyond the Kuiper Belt. They may exist and if they do they should be recognised as planets.

freddie
26-08-2006, 20:58
Read Michael Brown's explanation that Haku pointed a link to. It would be a nonsense to classify Pluto and Xena, let alone dozens of smaller objects, as planets when they're just the largest members of a population of small bodies. Mercury is much bigger and it's not much smaller than Mars. It isn't part of a population of small objects like they are, it's the smallest of the big objects. Mercury is 25 times more massive than Xena and Pluto. It's several times more massive than the entire Kuiper Belt. It's the obvious place to draw the line. If something as massive as Mercury is found in Kuiper Belt, it should be a planet, but I'd bet money that one won't be. What's your problem?
Hihi. I love your enormous conviction about a topic that's not yet completely explored. At least not up to an extent when one could claim something for certain like you seem to be. Tell you what... if they find something Mercury-size in Kuipers Belt you're buying me beer. :p

simon
26-08-2006, 23:59
I'll take that bet for the Kuiper Belt because I'm pretty confident Mike Brown would have found anything that big by now, but not for the Scattered Disc beyond it. There could easily be something big lurking out there that's too dim to have been seen yet.

simon
14-09-2006, 19:48
Xena has been given an official name by the IAU, to replace the nickname honouring the character played by Lucy Lawless. Mike Brown proposed and the IAU accepted the name Eris, after the Greek goddess of discord. He's called the name 'too perfect to resist', since his discovery sparked so much discord. The moon Gabrielle has been renamed Dysnomia after Eris's daughter, the spirit of lawlessness. So the actress no longer has a dwarf planet named after her character, but she does have a moon commemorating herself. :coctail:

http://www.nytimes.com/2006/09/14/science/15xenacnd.html?hp&ex=1158292800&en=04dd12ab6ceec087&ei=5094&partner=homepage

http://www.newscientistspace.com/article/dn10081-former-tenth-planet-named-for-goddess-of-discord.html