Talk:Planet/Archive 4

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Archive 3 Archive 4 Archive 5

New section: Composition

Is this necessary, or the "Internal differentiation section" covers the topic enough? Nergaal (talk) 10:06, 31 January 2008 (UTC)

It would be quite a long section. It would have to address the varying compositions of the terrestrials, gas giants and ice giants in our Solar System and the varying compositions of the numerous extrasolar planets found to date (hot jupiters, water planets etc.) Serendipodous 10:35, 31 January 2008 (UTC)

Slight mistake

The article now reads that "according to Ptolemy" the seven planets were the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. But in fact Ptolemy did not consider the Sun and Moon planets. His Almagest clearly separates the Sun and the Moon from "the planets". EDIT: rephrased the line to make it less ambiguous, but the main issue is not yet resolved. Serendipodous 12:29, 5 February 2008 (UTC)


The following need disambig:
Randomblue (talk) 16:43, 9 February 2008 (UTC)

First two fixed. Hemisphere's a problem, because none of the more specific articles actually mention hemisphere in the context described in the article, so there isn't much point in linking it, unless someone wants to create an article that deals with the topic. Serendipodous 18:24, 9 February 2008 (UTC)

Chthonian planets

Just a small question here; I know almost nothing about the topic, and am slightly confused. In "Extrasolar planets" various types of planets are discussed, and in the last sentence of the second paragraph Chthonian planets are mentioned: "There is also a class of hot Jupiters... the Chthonian planets." But the article Chthonian planet states that this is only a hypothetical class of objects and that currently no such planets are known. What I mean, maybe the sentence here should be reworded to "There may also exist a class of hot Jupiters.." (or something like it), for clarity? Or perhaps the article on Chthonian planets is wrong? --Jashiin (talk) 11:32, 13 February 2008 (UTC)

I think you're right there. Well spotted. Serendipodous 11:58, 13 February 2008 (UTC)

The extrasolar planets section was massively outdated (I don't think anyone had bothered to change it in two years), so it really needed a makeover. I've done a cursory update, but if anyone wants to have a go, they're welcome. Serendipodous 14:26, 13 February 2008 (UTC)

New Planet needs article?

Planet GJ 436T discovered Wed. April 9. (talk) 09:42, 10 April 2008 (UTC)

I don't know where they're getting that "smallest planet" malarkey from; the smallest planet ever found is smaller than Mercury, orbits a pulsar and was found in 1992. Still, belongs in the article. Serendipodous 19:25, 10 April 2008 (UTC)


Is there currently any system for classifying planets? Masterof148 (talk) 01:17, 18 April 2008 (UTC)

There are many informal classifications for planets, such as gas giant, ice giant, terrestrial, super-Earth, hot Jupiter and hot Neptune, but nothing cast-iron. Serendipodous 05:20, 18 April 2008 (UTC)

Ironic Remark

I quote an ironic remark that is currently placed in the article: "In the 6th century BC, the Babylonians had a far more advanced astronomical knowledge than the Greeks, and had a theory of the planets long before the ancient Greeks understood what the planets were." This is clearly an ironic comment towards the Greeks and should be removed unless you want similar comments to be made from Greeks towards western astronomers that came 2000 years after Greek astronomy. I dont see why he should make such a comparison, and if he is making it why there is not a similar comparison made for other civilizations. And in any case, the author of the above ironic comment did not clarify in detail the 'great' understanding of the Babylonians. And of course the same author cannot give us one name of babylonian astronomer or one babylonian serious scientific astronomical treatise, except of tablet with observations. Observations were made from all ancient civilizations. However, there is a tremendous gap between observations and advanced scientific work. Permit me to remind you that the ancient Greek scientific literature is far more extensive than the Babylonian observations from a plethora of famous astronomers. May I also point out that the astronomic scientific work done by the ancient Greeks is far more advanced than that of the Babylonians without the Greeks having any more advanced technology. To point out only a few of pure scientific works of the Greeks would take many books. Kassos (talk) 23:13, 21 April 2008 (UTC)

Well, the statement is true; whether it is ironic or not is a matter of opinion. I certainly didn't intend it that way. The comparison is made because modern western planetary theory is derived from the Greeks, and the Greeks obtained their planetary theory from the Babylonians. Serendipodous 06:14, 22 April 2008 (UTC)
It is not a matter of opinion. It is clearly ironic. It is clumsy, childish, uncivilised and provocative. Certainly not the kind of way someone with your English would put words. Furthermore,what you call the truth is a matter of debate. Although you could state it otherwise, even so you could not be precise because most of the Greek astronomic work is ORIGINAL as you know and did not copy 'theories', which again you cannot name because they were not stated explicitly in any scientific treatise. Moreover, if this is how you perceive truth I suggest you put the same comments for the western astronomers of renaissance. Also, the irony is within the irony in this case because the Greek ancient civilization was much more advanced than the Babylonian in all respects, not just astronomy, and if you want ironies from us we have a lot for your 'great' civilzation. Kassos (talk) 13:14, 22 April 2008 (UTC)
Greek astronomical knowledge did eventually eclipse that of the Babylonians, but not for 500 years. In the 6th century BC, the Babylonians had a far more advanced planetary theory than the Greeks. That fact is borne out by historical evidence. At the time the Babylonians were compiling tables of the motions of Venus, the Greeks still believed Venus was two stars, the evening star and the morning star. There is no record that the Greeks were aware of the planets before the arrival of Babylonian astronomy into their territory. It could be made clearer, and if it makes you feel better I can also neutralise the language a bit. Since no one actually proved heliocentrism until the 19th century, I don't really treat the Renaissance astronomers any more favourably. Copernicus had just as much evidence for his heliocentric views as Aristarchus did. It just so happens that for him, the idea caught on. Galileo did manage to find some evidence, but not enough to sway the Church. Serendipodous 16:19, 22 April 2008 (UTC)
Thank you for the altering the lines but that is not good enough. There are still mistakes. I quote:

"the Babylonians had a highly advanced level of astronomical knowledge, and had a theory of the planets long before the ancient Greeks." 1) the Babylonians did not have highly advanced astronomy, 2) Just because they observed venus before the Greeks does not make their astronomy any better, 3) the Greek astronomy that followed was the first advanced scientific astronomic work of this world and was much more advanced than that of the babylonians. 4)"long before the Greeks" That does not make any sense (and is still ironic)because the Greek astronomic work was original as it was based on geometry. 5) They way you put it is read like the Greek astronomy that followed was inferior, whereas it was superior. 6)You make it noteworthy to mention the Babylonian tablet, but what about all the Greek books, not just the almagest. I'm talking about countless books. Afterall, Newton used Greek geometric propositions in his Principia extensively to prove his gravitational theory. This IS reference. Not the one you are noting that the Greeks had referenced. Anyway, I will end this discussion here. I dont expect you to change anything. Write anything you like. There are other major errors in the article: 1) the sumerian origin of writing (false), 2) the Babylonian origin of greek gods (false), 3) The indoeuropean theory (false).

All these are just theories that have prevailed but not proven. The unfortunate thing is these theories and their inventors are being referenced all the time. There are some of those inventors whose intenions are not very fair and noble and anyone who knows the history of those theories will understand. There are many anti-Hellenic theories going around by various people of known semitic ethnicity and other ethnicities and their intentions are known. By this I dont include you personally. I just believe you have the wrong references. I see a gap of basic history facts between us so I will go no further. Also, the term civilization is very relative and I treat the term 'sumerian civilization' or 'medieval europe civilization' or 'early USA civilization' very skeptically.

Kind regards. (talk) 18:54, 22 April 2008 (UTC)

"the Babylonians had a highly advanced level of astronomical knowledge, and had a theory of the planets long before the ancient Greeks." 1) the Babylonians did not have highly advanced astronomy,

  • Yes they did. Particularly for the time. Serendipodous 19:24, 22 April 2008 (UTC)

2) Just because they observed venus before the Greeks does not make their astronomy any better,

  • It was better, at that time, because, again, at that time, the Greeks did not recognise what Venus was. Serendipodous 19:24, 22 April 2008 (UTC)

3) the Greek astronomy that followed was the first advanced scientific astronomic work of this world and was much more advanced than that of the babylonians.

4)"long before the Greeks" That does not make any sense (and is still ironic)because the Greek astronomic work was original as it was based on geometry.

  • For God's sake, the Greeks took their astronomy from the Babylonians, and then improved upon it using geometric calculations. Changed "long" to "centuries." Serendipodous 19:24, 22 April 2008 (UTC)

5) They way you put it is read like the Greek astronomy that followed was inferior, whereas it was superior.

  • No it doesn't. Read the following paragraph. Serendipodous 19:24, 22 April 2008 (UTC)

6)You make it noteworthy to mention the Babylonian tablet, but what about all the Greek books, not just the almagest. I'm talking about countless books. Afterall, Newton used Greek geometric propositions in his Principia extensively to prove his gravitational theory. This IS reference. Not the one you are noting that the Greeks had referenced.

  • All centuries later, which is already mentioned. Serendipodous 19:24, 22 April 2008 (UTC)

Anyway, I will end this discussion here. I dont expect you to change anything. Write anything you like. There are other major errors in the article: 1) the sumerian origin of writing (false),

  • You're going to need some pretty cast-iron proof to tell me that the Sumerians weren't the first civilisation to use writing. Serendipodous 19:28, 22 April 2008 (UTC)

2) the Babylonian origin of greek gods (false),

  • This article makes no such claim, only that the Greeks gave the planets names from their gods that loosely corresponded to the Babylonian gods. Serendipodous 19:24, 22 April 2008 (UTC)

3) The indoeuropean theory (false).

  • The Indo-European theory is hardly anti-Hellenic. And since it is backed up by 250 years of scholarship, and you've backed up your rebuttal with, well, nothing, I don't really think I can help you there. Serendipodous 19:31, 22 April 2008 (UTC)

All these are just theories that have prevailed but not proven. The unfortunate thing is these theories and their inventors are being referenced all the time. There are some of those inventors whose intenions are not very fair and noble and anyone who knows the history of those theories will understand. There are many anti-Hellenic theories going around by various people of known semitic ethnicity and other ethnicities and their intentions are known.

  • Ah. So you attempt to redress anti-Hellenism by employing anti-Semitism. Great. Serendipodous 19:45, 22 April 2008 (UTC)

By this I dont include you personally.

  • I'm flattered. (That was ironic) Serendipodous 19:45, 22 April 2008 (UTC)

I just believe you have the wrong references. I see a gap of basic history facts between us so I will go no further.

  • I have no idea which histories you're reading, but I think they've been rather selective. The works I use were recommended to me by historians of science. Serendipodous 19:45, 22 April 2008 (UTC)

Also, the term civilization is very relative and I treat the term 'sumerian civilization' or 'medieval europe civilization' or 'early USA civilization' very skeptically.

  • Civilisation means "building and living in cities". That's it. The Sumerians built cities, so they were a civilisation. Serendipodous 19:45, 22 April 2008 (UTC)

Kind regards. (talk) 18:54, 22 April 2008 (UTC)

Look, I'll take your concerns under advisement but I'm not about to start turning this article into a paean to the perfection of Greek civilisation just to appease your wounded national pride. The fact is that, as far as we can tell, the Greeks had no idea the planets existed until they received that information from the Babylonians. That doesn't take anything away from the Greeks; the Bible doesn't mention the planets either. This article is about planets. Not about astronomy. I will address your issues as far as I can but I will not distort the facts to suit your feelings. Serendipodous 19:24, 22 April 2008 (UTC)

What is wrong with the present version of the article? Nergaal (talk) 20:38, 22 April 2008 (UTC)

Basically, this guy thinks it isn't pro-Greek enough. Serendipodous 20:45, 22 April 2008 (UTC)

Heliocentric theory

There is mistake in the article that says that the ancients only proposed the geocentric theory. Of course,this is not true. The Heliocentric center was proposed by Aristarchus, not Coppernicus. Aristarchus was an astronomer who attemped among other thing to measure the size and distances of the moon and sun. He was therefore a pure scientific astronomer, not a philosopher and certainly not a mere observer. Kassos (talk) 23:13, 21 April 2008 (UTC)

So should the thoughts and beliefs of an entire civilisation be discounted because of the speculations of one man? That seems a bit imbalanced. EDIT: OK; added a qualification to the line "it was believed" to account for the occasional dissenters. Serendipodous 06:15, 22 April 2008 (UTC)
That man is not just anybody. He was an astronomer and was author of many books with original scientific astonomical work much more advanced that that of Babylonians. If you want to be precise, you should take that into account. We are not talking about an unknown here. I hope you understand that. You changed it to "it was believed". I'm sure you can do better than that for a man whose works are known and respected throughout the world. The Greeks were the first to propose the Helicentric system, and yes it took one man. As Copernicus was only one man. Therefore you should change the line: "In ancient Greece as well as in ancient China, ancient Babylon and indeed all pre-modern civilisations,[7][8] it was almost universally believed that Earth was in the centre of the Universe and that all the "planets" circled the Earth." and put that only babylonians and chinese believed on the geocentric system whereas the ancient greeks were the first to propose the heliocentric system. Be precise please, don't avoid Greek contribution on purpose. I'm sure if it was a babylonian proposing the heliocentric system you would have mentionted him first line in the article. Kassos (talk) 13:14, 22 April 2008 (UTC)
The idea that the "ancient Greeks" as a whole proposed the heliocentric system is just ludicrous. Aristarchus's ideas obviously had little or no effect on the wider philosophical community, for the simple reason that, when the collective astronomical knowledge of the ancient Greeks was compiled by Ptolemy 300 years later, his views are ignored, and indeed, discounted (I'm speaking from experience here; I've read the Almagest). He is notable mainly because he had a hunch which, 2000 years later, turned out to be right. Serendipodous 16:19, 22 April 2008 (UTC)
No,i'm not saying the Greeks as a whole, and that's not the point. I simply believe that since the Babylonians did not prove anything as well, and since they adopted the geocentric theory, it would be fair to mention a Greek astronomer (not philosopher) who 'speculated' the Heliocentric theory for the first time. Also, whether or not Aristarchus' ideas were accepted does not mean that he did not 'propose' the Heliocentric theory. Therefore, if you are going to mention Copernicus, then you should also mention Aristarchus who happened to measure the distances and sizes of moon and sun with whatever accuracy using CORRECT paralax geometric methods for the first time in the world. Thank you. Kind regards. (talk) 18:54, 22 April 2008 (UTC)
Plenty of other people also preceded Copernicus in suggesting heliocentrism. These individuals are not relevant to the wider historical context because they were abberations. Copernicus does not deserve credit for coming up with heliocentrism, sure, but the fact of the matter is that it was Copernicus's idea that caught on. All the others faded away. And really, it wasn't until Galileo, Kepler and Newton that the heliocentric model met with wide acceptance. So no, I don't see this as relevant. Serendipodous 19:11, 22 April 2008 (UTC)


I believe the Greek etymology of the word 'Planet' although it is mentioned in the article, it is mentioned mid-way through the article. This is not appropriate, as the etymology should come first in any article, and it certainly does so in all the other wikipedia articles. Kassos (talk) 23:13, 21 April 2008 (UTC)

It isn't mentioned in the lead; it is, however, mentioned directly below it. I don't see the point of mentioning it twice. Serendipodous 06:17, 22 April 2008 (UTC)
Sorry but I fail to see the rationale behind placing the etymology first in this or any article, unless it is of particular importance to the article. Certainly such a requirement is not listed in the Wikipedia:Manual of Style, and the etymology is not exactly the most important element in an article of this nature. In fact my preference would be to put the etymology near the end, or move it to the wiktionary where it belongs.—RJH (talk) 20:05, 22 April 2008 (UTC)
When someone write an article about a name-word-term-place then the etymology is the first most important thing. For some other cases, etymology is not applicable or appropriate, i agree. But not in all cases. When you write an article about astronomy, astrology, philosophy, galaxy, telescope, biology, geography, geology, geometry, theatre, tragedy, comedy, mathematics, democracy, artistocracy, oligarchy, politics and so on, then the etymology is the first most important thing to mention, otherwise you miss the whole point. What's the point of teaching your children about philosophy if you haven't told them first what the word means? What's the point of teaching your children about astronomy without telling them what the word means? What is the point of doing a course in history 101 and not knowing where the words 'history', 'museum' and 'archaeology' and 'neolithic' come from? What's the point of going to drama school without knowing what the words 'theatre', 'amphitheatre', 'drama' 'comedy' tragedy' 'chorus' 'lyrics' mean? Do you find these things unimportant RJH? Do you want to produce half-educated half-illiterate people? What's the point of writing an article about Acropolis, Neapolis(Italy), Tripolis (Libya), Philadephia (many places), Sozopolis (Bulgaria), Atlantic, Arctic, Antarctic, Amazon without telling the etymology of these names? What is the point on writing an article about 'Europe' or 'Asia' without explaining the origin and etymology of these words. As far as the article about planet is concerned, it may be arguable where to place the etymology. However I would prefer it is placed first because it has an interesting meaning. I understand why some people (and i dont mean serendipodous) would like not to include at all the etymology of important terms-names-places. The reason being that most of them have Greek origin and it would not be politically correct for the rest of the world having to face a Greek etymology all the time. Furthermore, the same people would like to avoid the etymology of those words-names-places-terms because they reveal the Greek origin of those things and the Greek historical places currently under foreign occupation. Therefore, for the sake of 'political correctness' we should not tell the whole truth because it will upset some people. For the sake of YOUR 'political correctness' we should not educate people and we should sacrifice truth and history. And when did the Wiki manual become the bible of conduct RJH? If you want to burry the etymology to wiktionary go ahead but that will not help anything. Would you like to be one of those people who goes to a pathologist, ofthamologist, gynaecologist, otorinolaringologist without knowing what it means? Would you like to read the 'Genesis' without knowing what the name means? Why should we not mention the etymology of those things RJH? Why write an article on Alexander the Great or Aristotle and miss out the etymology of the names? Is there a political reason behind this? RJH the etymology of a word is the First most important thing whether or not i has a Greek or Latin or whatever origin. What you do in this article is your choice and I dont care. I just wrote this as an answer to RJH. (talk) 17:26, 23 April 2008 (UTC)
I agree with you that we need to concentrate on the "planet" means. However, the modern meaning of "planet" is (roughly) "large object that orbits a star", and the article does concentrate on this meaning. The etymology of the word might be interesting, but it is not important. Bluap (talk) 18:36, 23 April 2008 (UTC)
Hmm, a lengthy rant. Let's see...
  • "What's the point of going to drama school without knowing what the words 'theatre', 'amphitheatre', 'drama' 'comedy' tragedy' 'chorus' 'lyrics' mean? Do you find these things unimportant RJH?"
    • There is a difference between meaning and etymology. I can certainly understand the meaning of a word without needing to know its history.
  • What's the point of writing an article about Acropolis, Neapolis(Italy), Tripolis (Libya), Philadephia (many places), Sozopolis (Bulgaria), Atlantic, Arctic, Antarctic, Amazon without telling the etymology of these names?
    • I believe that an article on all of those subjects would do just fine without a history of the word. In fact, I have read a fair amount on several of those subjects without needing to know the history of their names, thank you.
  • However I would prefer it is placed first because it has an interesting meaning.
    • Not everybody has your priorities. I would prefer to learn about the place first and then, if I'm still interested, read about why it was named. The latter just isn't as important to everybody else.
  • Would you like to be one of those people who goes to a pathologist, ofthamologist, gynaecologist, otorinolaringologist without knowing what it means?
    • Again you are confusing meaning with etymology. I can understand the meaning of a word without knowing it's history.
See the etymology article. It tells me the meaning in the first sentence without even mentioning the origin of the word "etymology". Bah. &c.—RJH (talk) 14:36, 25 April 2008 (UTC)

Shouldn't the opening be "a body that orbits a Sun"?

Names in Arabic and Hebrew

I would like to include the names for the planets in Arabic and Hebrew, but I haven't been able to trace the mythological/other origins for the names. Serendipodous 19:40, 16 May 2008 (UTC)

artist's impression?

We have actual photographs of planets - would one of those not make more sense as the primary picture for the article than an artist's impression? "this is what a planet looks like" rather than "this is what some planet might or might not look like" —Preceding unsigned comment added by (talk) 13:28, 15 July 2008 (UTC)

True, but planets are so varied in their appearance that no one picture can do the concept justice. I kinda like the fact that the opening image is of a generic planet without any specific traits marking it out, but that's just me. Serendipodous 13:45, 15 July 2008 (UTC)
Not to mention that gas giants have the highest known numbers thanks to recent exoplanet discoveries. Though smaller planets, like smaller stars, should be more common type. (Unless there is a common trend for gas giants to aggressively migrate and remove dynamically weak bodies.) -- Kheider (talk) 19:02, 15 July 2008 (UTC)
"True, but planets are so varied in their appearance that no one picture can do the concept justice." I think this is irrelevant to the question of whether a painting or an actual photograph of a real planet should be's still just one picture. "I kinda like the fact that the opening image is of a generic planet without any specific traits marking it out, but that's just me." From that artist's picture, you can find many specific traits: 1) It has an atmosphere. 2) It has moderate cloud cover. 3) It is rather hot, given how its night-time side glows with a dull red color.
So the question remains: Why not put a photo of an actual planet there? How about Neptune?
Neptune.jpg Wbrameld (talk) 16:14, 24 August 2008 (UTC)
... Or Pluto! :P There aren't enough planets with photos that any one can be considered "Typical". It would be like a picture of Ringo Star an an article called "Beatle". Algr (talk) 18:51, 24 August 2008 (UTC)
The lead picture need not be representative of all planets just as the lead picture for building is not representative of all buildings. And since there are plenty of actual photographs of planets available, one of them should be used. The image of pluto Wbrameld suggests above would do nicely. -Neitherday (talk) 06:23, 3 December 2008 (UTC)
Pluto would be a bad choice for two reasons. One it is not classified as a planet since it is not large enough to be dynamically active, and two we do not have any good pictures of it. The picture we are using is decent, but perhaps if anything, we should also have a picture of a rocky body like Mars or Mercury to go with it? -- Kheider (talk) 14:27, 3 December 2008 (UTC)
That's what I get for editing too late at night. Wbrameld suggested the image of Neptune, which is what I meant to say. -Neitherday (talk) 14:32, 3 December 2008 (UTC)


Might it benefit the article if we were to somehow able to find a way to put the table of contents on the right side of the page? Emesee (talk) 02:03, 24 August 2008 (UTC)

Religious claims

This article, like a number of ones on religious subjects, casually drops claims that religious statemsnts no longer hold or are no longer believed. Imagine the following similar statement in the Astronomer article:

Astronomers were once believed to produced intelligently designed theories about nature and cosmology. Today, however, we regard the utterances of astronomers, like all human utterances, as the product of natural biological and biochemical processes including neurons, muscles, and vocal cords. Accordingly, utterances by scientists are explained in natureal, mechanical terms, and are no longer explained as having a cosmological connection or as having reference to any cosmology.

If a natural frame of reference or explanation is truly believed to refute communications medium status of frame of reference, then scientific communication has a self-reference problem, because the sounds and paper-marks scientists use to communicate thoughts also don't have to be explained in terms of media for communicating thoughts, and can also be explained in purely natural terms without needing to refer to or posit the existence of any thought behind them or of their having any media or emmissary role. (See Eliminative materialism). If a mechanical explanation refutes a media explanation, this is as true for scientific media as for any other kind. Accordingly, the fact that something can be explained in mechanical terms simply doesn't refute a claim of its also being a medium for some kind of communication. The existence of science, as currently understood, depends on belief in the existence (and hence the possibility of existence) of communications and communications media. It assumes that mechanical explanation and communications medium status can co-exist and that claims about the existence of a mechanism to describe an object's composition or behavior do not refute claims that it also serves as a medium that can be "read" to discern a "message" about something not related to its internal structure. Accordingly, claims contrary to these assumptions should not be casually dropped in science articles. Best, --Shirahadasha (talk) 18:42, 24 August 2008 (UTC)

I don't think that anyone believes that the planets are gods anymore... Serendipodous 07:06, 27 August 2008 (UTC)

Worst Featured Article in Years

This article is very poorly written for a featured article.

For example, "The planets were originally seen as divine, emissaries of the Gods," Is so incredibly biased for a single culture. It should read "The planets were seen by many early Human cultures as divine." And then elaborate that cultures might seem them as Gods, messengers, omens, or signs from the Gods. Whatever, but this article is pretty stupid the way it is. Wikipedia should really do better with such an important article, but one can't expect much from a destroyed project. —Preceding unsigned comment added by TheConstructiveVandal (talkcontribs) 20:49, 24 August 2008 (UTC)

Nah, I have seen worse :) But I agree that the paragraph that you mention would have been better left out entirely from this article. For one thing, the opening paragraphs are supposed to summarize the text below, and I do not see that here. It makes the entire article harder to get into, and I do not see that it serves any purpose. The rest of the article is not bad at all. DanielDemaret (talk) 21:20, 24 August 2008 (UTC)
I'm a bit confused. There is a mythology section that deals with the issue of the planets as gods or as sacred to the gods. How should it be referred to in the lead? Serendipodous 07:08, 27 August 2008 (UTC)
A few other problems with the opening part. One could read into the text that Copernicus and Galileo were the first to suggest a heliocentric world view, which is false. When I read it, I even thought I could infer from the text that Galileo invented the telescope, which is not entirely accurate. On top of that, does this summarize the article? DanielDemaret (talk) 21:26, 24 August 2008 (UTC)
I've had a go at rewriting it slightly. Serendipodous 07:08, 27 August 2008 (UTC)

About the term planet, or about the thing itself?

The disambiguation line at the top states that the article is about the astronomical term "planet". Isn't the article mainly about the concept of planet or about planets themselves? Only a few sentences are about the term. I'd make the change, but it seems to be locked. Nesbit (talk) 23:25, 26 August 2008 (UTC)

You're right. It should be "object." Sheesh. This page has gone through a lot of changes in the last few weeks that I wasn't aware of. Serendipodous 07:09, 27 August 2008 (UTC)


The sentence "After Copernicus suggested that the planets orbited the Sun, this view was supported by Galileo with the use of the telescope" appears. Two false impressions are given. Pythagoras and others were putting forward opinions similar to those of Copernicus much earlier. Galileo was supporting Copernicus from about 1595, before the telescope came in. —Preceding unsigned comment added by (talk) 09:05, 4 September 2008 (UTC) Galileo first used the telescope in 1609. —Preceding unsigned comment added by (talk) 09:09, 4 September 2008 (UTC)

OK. The only way I can make it work is to remove mention of Copernicus, but there you go. Serendipodous 09:41, 4 September 2008 (UTC)

Extrasolar planets

"Since 1992, through the discovery of hundreds of extrasolar planets (planets around other stars), scientists are beginning to observe similar features throughout the Milky Way Galaxy."

These "features" refer to hydrology, volcanism, plate tectonics, and the like. I don't believe any of these are observable on extrasolar planets using current technology. --Bowlhover (talk) 00:27, 7 September 2008 (UTC)

More Planets

Heard on a local AM radio station this; "In school they taught us there were 9 planets.....well now there's 13." Any source on this? Any names of the new 5 planets (8 [excluding Pluto] + 5 new ones) (talk) 01:53, 21 September 2008 (UTC)

There are now 8 planets and 5 dwarf planets (the 5th of which, Haumea, was recently identified) for a total of 13 in the solar system, as this article mentions. —Alex (ASHill | talk | contribs) 02:33, 21 September 2008 (UTC)

Planets in other galaxies

What about them? Theres a ton! Shouldnt their at least be a list instead of a Redirect?? RoyalMate1 22:04, 27 September 2008 (UTC)

Never mind, I found a few but it was somewhat hard to find. RoyalMate1 22:09, 27 September 2008 (UTC)


The article still implies or says explicitly that Galileo was using the telescope in the 16th. century. —Preceding unsigned comment added by (talk) 12:53, 17 October 2008 (UTC)

Yes. Careless flub. Thanks for spotting it. Serendipodous 12:57, 17 October 2008 (UTC)

Please edit

Hi, I can't edit the page as I don't have an accout. Near the bottom, close to the links, you will find a reference to Michael Jackson that is fairly out of place. Please remove. (talk) 17:02, 20 October 2008 (UTC)

Well spotted! :-) Serendipodous 17:04, 20 October 2008 (UTC)

rotation direction

do all the planets rotate in same direction and all the planets are in same plane, if so what is the cause for it. —Preceding unsigned comment added by (talk) 07:07, 12 December 2008 (UTC)

All the planets orbit the Sun in the same direction, and all planets orbit within roughly the same plane, with slight deviations. Not all planets spin in the same direction; Venus rotates in the opposite direction from the other planets. Attempts to explain the origin of the Solar System had to try and explain both why the planets move in the same direction and why they travel in the same plane. The one hypothesis that did offer an explanation for both these facts was the nebular hypothesis, which said that the Solar System began as a spinning cloud that shrank inwards until, like a pizza tossed into the air, it started to flatten out. Eventually it formed into a large ball of gas in the middle and a disc of material in orbit around it. The planets formed from this disc of material. Serendipodous 09:56, 12 December 2008 (UTC)

Dominance of IAU Definition of Planet in Article

For the record, I do not use the IAU definition of planet, as I think it is flawed. But that is not why I am bringing this to attention.

In the lead section of the article, the IAU definiton of planet is (wisely) stated as being defined by the IAU, and carries the correct connotation of there being no overwhelming consensus. However, in the rest of the article, and especially in the lead picture, the word "planet" is used only as defined by the IAU. This carries the connotation of overwhelming consensus, which is false.

In compliance with the Neutral Point of View Policy, I ask that a note be put at the top of the article stating along the lines of "the word 'planet' used in this article is the definition of planet adopted by the IAU". Since Wikipedia in almost every article espouses the NPOV policy, I assume that the policy should be applied to this article as well. If not applied to this article, this is effectively an endorsement of the IAU definition by Wikipedia.

Patricius Augustus (talk) 02:30, 17 January 2009 (UTC)

Scientific terms are given definitions by the scientists that use them. The IAU, being the most encompassing group of astronomers in the world, has the ability to define what planet means in astronomy. An encyclopedia article dealing with planets in an astronomical sense therefore should use that definition. This is not a question of point of view, but of terminology. The term is defined and then is used in that sense. To define the term one way and then use it another would make no sense. Khajidha (talk) 06:11, 17 January 2009 (UTC)
I would hardly consider a vote of 430 out of 10000 astronomers represenative of the astronomical community. All that I ask is a notice in the article which states that the IAU definition is used in the article, so there can be no confusion or controvesy about it.

Patricius Augustus (talk) 11:15, 17 January 2009 (UTC)

First, the article makes it perfectly clear from the start that it uses the IAU definition. Second, there is no other definition of planet, so there is no need for controversy. Finally, whatever your feelings about how the IAU definition was arrived at, it is still the official scientific definition of a planet, and a scientific article should reflect this. Serendipodous 12:24, 17 January 2009 (UTC)
However it was arrived at and regardless of how many people voted, this definition was OFFICIALLY promulgated by the IAU. It is the ONLY definition with any official backing from the scientific community. Therefore, it is the definition used here.Khajidha (talk) 23:41, 17 January 2009 (UTC)
Serendipodous and Khajidha, I ask that you do not conflate the IAU with the scientific community. The IAU may have a different view on some things than the majority of astronomers, so do not go around saying that the IAU has absolute power over science. It does not. It is merely an organization of astronomers.
Secondly, there may not be any one "competing" definition of planet with the IAU, but there is conteroversy and backlash against it, in both the astronomical community and the public. I do concede that it is the official IAU definition of planet, because the IAU is an organization with a beauracracy. The perception that the IAU has absolute power over science and can do whatever it wants worries me, and instills fear over the future of astronomy.
Back on topic, all that I asked in the first place is making it clear in the article that the word "planet" as used in the article is the IAU definition of the word, and stating that it does not have universal acceptance among astronomers, which is already mostly taken care of in the lead section.
This conforms to the neutral point of view policy. An excerpt from the article detaling it: "All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources."
I simply state that this article must comply with the NPOV policy, and not have a bias towards the IAU, and ensure that all the significant views are represented in the article.
I ask that all editors of this article keep this in mind. Patricius Augustus (talk) 16:39, 18 January 2009 (UTC)
So far, Patricius, you are the only person on this board who has pushed a point of view. You also show little understanding of the IAU and its authority. The IAU is the final arbiter on matters of astronomical nomenclature. It has to be. Science cannot work unless everyone understands when they read one another's papers that they are discussing the same thing. One botanist in Argentina has to take as read that another botanist in Morocco is using the same definition of "berry" as every other botanist worldwide, or experiments could not be repeated. To this end, the International Botanical Congress has an official definition of "berry" that is used among botanists, which has nothing to do with the traditional definition of "berry" that we're used to. Avocados and bananas are berries according to the IBC, but raspberries and blackberries are not. That happens all the time. The IAU is astronomy's agreed body for establishing definitions, ergo it is the only authority with any say in the matter. Other astronomers may use a different definition of "planet", but if they publish a paper using their own personal definition, they risk creating confusion with others using the established definition. Serendipodous 17:40, 18 January 2009 (UTC)
Just to clarify, what Serendipodous has stated means that there are NO other "significant views" from the scientific community. In the IAU article here on Wikipedia for example, the IAU is defined as the internationally recognized authority for assigning designations to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them . Khajidha (talk) 20:58, 19 January 2009 (UTC)
It is a significant view among astronomers, albeit a minority, that the IAU definition is scientifically flawed. However, both of you seem to not recognize that fact, and violate Wikipedia's own policy on representing other significant views, and not pushing a particular point of view (in this case the IAU, et. al.). Just because I disagree with and often do not submit to the IAU does not mean that I have little understanding of it.

I consider this discussion finished, since it accomplished nothing. Patricius Augustus (talk) 13:02, 20 January 2009 (UTC)

Edit to Top of Article

I have edited the top of the article to redirect readers interested in discussion of the definition of planet to Definition of Planet, since there is more in-depth analysis at that article.—Preceding unsigned comment added by Patricius Augustus (talkcontribs)

This article already links to it several times, but Ok. I'm surprised you didn't see it before, since it answers most of your concerns. BTW, I wrote most of it myself; ironic since you accused me of deliberately burying the controversy. Serendipodous 17:11, 30 January 2009 (UTC)

hot Jupiters vs. gas giants

when it says "Among extrasolar planets, axial tilts are not known for certain, though most hot Jupiters are believed to possess negligible to no axial tilt, as a result of their proximity to their stars" should it say gas giants as hot Jupiters seems to be confusing Confront (talk) 01:08, 7 March 2009 (UTC)

hot Jupiters are defined in the extrasolar planets section. Serendipodous 17:54, 9 March 2009 (UTC) it is considered improper to re-word other people's quotes. Hot Jupiter is a nickname for gas giants that orbit so close to their host star that they act like a "hot jupiter" would. It does not mean that our Jupiter is hot. -- Kheider (talk) 19:32, 19 May 2009 (UTC)

Days of Week

Somewhere in this article, possibly near the Hellenic world part of the History section, it should be mentioned that the names of the days of the week are taken from the list of the visible planetary spheres taken in order of brightness.

Intro vs History?

I know this article is great and has been reworked to death, so I will leave this suggestion here without making the change myself. I think that the 3rd paragraph of the introduction would be better placed at the start of the History section. The intro is overly long (the ToC is below the fold) and that paragraph is easily relocatable without disrupting the article's flow. - Frankie (talk) 16:23, 17 March 2009 (UTC)

That paragraph also covers planetary attributes and extrasolar planets. the intro is basically a runthough of the topics in the article. Serendipodous 18:19, 18 March 2009 (UTC)

Uranus has retrograde rotation

The statement that Uranus can be considered to have prograde rotation is false. Even if you consider tilt of 82 degrees in the other direction rather than the conventional 98 degrees it still has retrograde rotation relative to the direction of its orbit. Zbayz (talk) 13:31, 20 August 2009 (UTC)

The article does not state the Uranus has pro or retrograde rotations. It only states that it's rotation is clockwise or counter-clockwise depending on the definition of the north pole, which is true. Ruslik_Zero 13:45, 20 August 2009 (UTC)
All rotating objects could be said to rotate clockwise or anti-clockwise depending on how you define their north poles. In that regard there is nothing special about Uranus. Zbayz (talk) 14:02, 20 August 2009 (UTC)
How about this wording then which keeps the clockwise/aniclockwise info but also includes the point I was making about retrograde to its orbit.:
"the exceptions being Venus and Uranus which rotate clockwise (although because of Uranus's extreme axial tilt there are differing conventions on which of its pole to call the north pole and therefore whether it is rotating clockwise or anti-clockwise around its north pole. However regardless of which convention is used, Uranus is rotating in the opposite direction to its orbit.)" Zbayz (talk) 14:21, 20 August 2009 (UTC)
This is better. Ruslik_Zero 11:31, 22 August 2009 (UTC)

Is this article too long?

100 k is pretty long. Is this article OK? Serendipodous 20:51, 23 November 2009 (UTC)

It is a vital article so I would be inclined to be ok with having it longer. Plus, trimming would be possible only in the history section, but that is pretty essential to remain here. Nergaal (talk) 00:20, 21 December 2009 (UTC)


When Jupiter was named, did they know it was the biggest one, or is that just a coincidence? Did they call Neptune that because they saw it was blue and looked like the ocean? They could see Mars was red, so that makes sense. I guess I was looking for why they got the names they did.--Neptunerover (talk) 01:01, 21 December 2009 (UTC)

Neptune may have been named for its colour; not sure, but it is visible through a telescope. Jupiter appears brighter than Mars to the naked eye, even though it's year is six times longer. So the Babylonians (who first named the stars after gods) may have given it pride of place. But no, they didn't know it was the biggest. Serendipodous 01:54, 21 December 2009 (UTC)
Jupiter would have been special because it would have been the brightest "star" in the sky that could stay up all night. Venus is brighter but is never far from the Sun. So at best Venus is only visible for a couple hours after sunset or a couple hours before sunrise. Venus always near the Sun may have seemed like the Suns subordinate love slave. :) So when they named Jupiter I suspect it was meant to be "special". -- Kheider (talk) 06:01, 21 December 2009 (UTC)
Also, Venus wasn't always recognized as a single planet. Maybe had s.t. to do w recognizing Jupiter as the greatest planet, back before the Latin names were assigned? kwami (talk) 06:29, 21 December 2009 (UTC)

Definition wrong?

Assuming the definition of celestial body is correct, the definition of a planet "A planet (...) is a celestial body..." must be wrong, since Earth is named as planet, but is not a celestial body. —Preceding unsigned comment added by (talk) 20:03, 29 December 2009 (UTC)

Edit: The IAU website uses celestial body, too, but I found no definition of a CB. It seems to follow that the CB's definition is wrong, then. —Preceding unsigned comment added by (talk) 22:33, 29 December 2009 (UTC)

I have added a "Citation Needed" template to the definition of Celestial Bodies in Astronomical object. If no one can find a citation, say by Feb 2010, I would suggest that someone revise the definition of Celestial Bodies and Celestial Objects to make them identical to Astronomical object. --RoyGoldsmith (talk) 16:02, 1 January 2010 (UTC)

Wiktionary gives the following definition for "celestial body": (astronomy, astrology) A natural object which is located outside of Earth's atmosphere, such as the Moon, the Sun, an asteroid, planet, or star. The same definition is also found here: Besides, the word "celestial" literally means "heavenly" or "in the heavens" so it naturally doesn't include earth. Seems IAU was a bit sloppy in their definitions here... --Mirage GSM (talk) 12:17, 19 May 2010 (UTC)

Americanization Effort to Commence

WP:ENGVAR#Consistency within articles agrees that the article needs to be consistent in its use of national varieties of English. The guideline that seems right to use here is WP:RETAIN. Whichever variety of English the article originally used should be the standard with which we are consistent. In this edit, an American spelling establishes the use of a national variety of English for this article. (Although the original author misspelled the word, recognized, so maybe we should misspell every word in this article?) I will take on the responsibility of copy editing this article as well as updating the language presently. Friedlad (talk) 05:58, 9 January 2010 (UTC)

There are several problems with your statement above. First of all, the use of "-ize" is not exclusive to US English, being commonly accepted in British English as well. If you read through our articles on the differences between Amerian and British spelling and Oxford spelling, as well as the OED article "Are spellings like 'privatize' and 'organize' Americanisms?", you'll see that the use of "-ize" in British English dates back to the 1600s. That alone would be proof enough to dispel any thought of "Americanizing" the article, and the subject matter could certainly also be argued as deferring to international standards rather than those of one particular country. Furthermore, random version sampling (using the first versions in January and July) show that the article has used international spellings such as "centre" and "kilometre" since at least 2004. Please do not change it merely for the sake of personal preference, as that does not benefit the project. --Ckatzchatspy 21:48, 9 January 2010 (UTC)
Maybe try more than just a random sampling because the retain standard is whichever was used first. Perhaps I misjudged the original use but intended to find the first use of a nationalized spelling.
Friedlad (talk) 20:29, 10 January 2010 (UTC)
WP:RETAIN says "If an article has evolved using predominantly one variety, the whole article should conform to that variety, unless there are reasons for changing it based on strong national ties to the topic.". Given that the article demonstrates use of British English for the past six years, we can safely interpret that it has evolved that way. Furthermore, and more significantly, even if you were to discover evidence of American spelling prior to that, there are no demonstrated reasons for (or possible benefits from) changing it at this point in time. --Ckatzchatspy 06:41, 11 January 2010 (UTC)

Planets come from the Greek lanugage —Preceding unsigned comment added by (talk) 21:00, 20 January 2010 (UTC)

Ranging from the size of gas giants to that of terrestrial planets

Crude size comparison of PSR B1257+12 A with Earth

PSR B1257+12 A is suspected of being less massive than the Earth. Is it proper to call it a larger terrestrial planet? What is large? -- Kheider (talk) 19:52, 26 January 2010 (UTC)

Who said "larger". Ah, I see. Fixed. AldaronT/C 20:01, 26 January 2010 (UTC)
I just reinstated again (before reading this discussion), based on the claim in the article
"COROT-Exo-7b, a planet with a diameter estimated at around 1.7 times that of Earth, (making it the smallest super-Earth yet measured)"
But it seems you're right, so I'll remove the "larger" again. But the above quote should also be corrected then. --Roentgenium111 (talk) 18:40, 4 May 2010 (UTC)

history additions

The additions of India and Islamic world to the history section are all well and good, but they don't really have anything to do with the section topic. The section is about the changing meaning of the word "planet", not a random list of "who-did-what-firsts". Such-and-such an Indian and/or Arabic astronomer may have predated Copernicus or Kepler in coming up with an idea that is now accepted as correct, and that is all very nice and lovely, but it doesn't say anything about what the Indians or Arabs in general believed about the planets. Serendipodous 20:42, 4 March 2010 (UTC)

Celestial body

I've just had an interesting discussion elsewhere, with someone citing that since the 2006 IAU definition begins "A celestial body that is...", Earth is no longer a planet either because by definition Celestial bodies/objects (as opposed to Astronomical bodies/objects) specifically exclude the earth (which cannot appear in its own sky/the heavens, the term is geocentric). I can't find any source to contradict this position, and several websites appear to agree that a celestial body is 'anything except the earth', therefore I find myself wonder if it is therefore true... (talk) 10:25, 5 March 2010 (UTC)

Since celestial means "pertaining to the sky or visible heaven", I do not see a real problem. -- Kheider (talk) 18:31, 5 March 2010 (UTC)
"Universe Today" would disagree ("By definition a celestial body is any natural body outside of the Earth's atmosphere."), as would "Wiktionary" ("(astronomy, astrology) A natural object which is located outside of Earth's atmosphere"), also "Wordnet (Princeton)" ("heavenly body (natural objects visible in the sky)"), also "'s Space/Astronomy glossary"("natural objects that can be seen in our sky"). Astronomy magazine's glossary "doesn't even have it listed". Most astronomy glossaries I can find online don't list the term, which doesn't seem very 'scientific'... The word Celestial etymologically comes from Latin, and "means Heaven or Sky", in clear contrast to 'earth'. (talk) 23:12, 8 March 2010 (UTC)
Celestial is an adjective. Common sense tells us that the Earth is to be included. The Earth is a planet, even if it is only a celestial body when viewed from another objects "sky". The IAU makes it very clear that the Earth is to be included. ==> "(1) The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune." To truly claim the Earth is not a planet would be about as strange as claiming that the Sun is still a true planet. -- Kheider (talk) 06:05, 9 March 2010 (UTC)

I've given up on this article

If every source that I can locate says that the Greeks got the names of the planets from the Babylonians, but one source supplied does not, (I suppose that the exact concordance between the gods' names is purely coincidental) then we're not going to resolve this without contacting an antiquarian scholar. So this article now contradicts itself, and there's nothing I can do about it. Over the last few weeks, nearly every ethnic group on planet Earth has planted its flag on this article. I don't care who got what idea from whom; I just want this article to reflect GLOBAL scholarly consensus, not the consensus of rabid nationalists, whatever their nation. Serendipodous 16:50, 3 April 2010 (UTC)

I have removed the offending text, since you are correct that it is a minority view. Are there any other specific issues? Athenean (talk) 17:49, 3 April 2010 (UTC)
Thank you, that was very kind of you. :) There are other issues but they're not immediately solvable. Serendipodous 18:01, 3 April 2010 (UTC)

Needs Graphic of Smallest Dwarf Planets Up to Largest Exo-planets Along with Categories (All in one comparative graphic)

From Ceres-sizes dwarf planets up to a Brown Dwarf (really just short of being a star. (talk) 03:43, 16 May 2010 (UTC)

That wouldn't be easy to read. We have a List of extrasolar planets already.Serendipodous 04:56, 16 May 2010 (UTC)
The smallest (currently official) dwarf planet is Ceres (~900km), but dwarf planet could easily come in the size of ~400km (or smaller). The largest puffy planets have bloated atmospheres because they are very close to the host star and as a result are ~1.7x the diameter of Jupiter. Jupiter is ~140,000km in diameter so the largest are about ~230,000km in diameter (give or take). This could easily make the largest planets 600x the diameter of the smallest dwarfs. -- Kheider (talk) 07:36, 16 May 2010 (UTC)

Why does a planet spin?

I looked on this article for an answer to this question, but I couldn't find it. If the process of planetary accretion is completely random, then a naive intuition might suggest that the resulting body would have no net angular momentum. Hence, why does every planet spin? I think I know one or more possible answers as to why, but I'd like to see it presented in the article. Thank you. :-) —RJH (talk) 15:47, 20 May 2010 (UTC)

I inserted some text.—RJH (talk) 15:51, 21 May 2010 (UTC)

Confusing wording on extrasolar planet/sub-brown dwarf distinction

A sentence concerning the distinction between planets and sub-brown dwarfs, implies some contradiction and caused me initial confusion.

The following is the article content regarding extrasolar planet definitions and sub-brown dwarfs:

"Extrasolar planet definition
In 2003, The International Astronomical Union (IAU) Working Group on Extrasolar Planets made a position statement on the definition of a planet that incorporated the following working definition, mostly focused upon the boundary between planets and brown dwarves:[2]
1.Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 times the mass of Jupiter for objects with the same isotopic abundance as the Sun[39]) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass and size required for an extrasolar object to be considered a planet should be the same as that used in the Solar System.
2.Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed or where they are located.
3.Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate).
This definition has since been widely used by astronomers when publishing discoveries of exoplanets in academic journals.[40] Although temporary, it remains an effective working definition until a more permanent one is formally adopted. However, it does not address the dispute over the lower mass limit,[41] and so it steered clear of the controversy regarding objects within the Solar System. This definition also makes no comment on the status of planets orbiting brown dwarfs such as 2M1207b. A sub-brown dwarf is a planet-mass object that formed through cloud-collapse rather than accretion. The distinction between a sub-brown dwarf and a planet is unclear; astronomers are divided into two camps as whether to consider the formation process of a planet as part of its division in classification."

The last couple sentences are the problem. The last sentence is commenting, from a stellar and planetary evolution point of view, on whether formation processes should be included as part of the definitions. However, it is positioned immediately after sentences pointing out the deficiencies of the definitions. This context makes the sentence read as if its saying the definitions are unclear on the planet/sub-brown dwarf distinction. The definitions are in fact quite clear on this distinction.

I am inclined to reword this slightly. Perhaps simply move the last two sentence out of the paragraph where they can stand on their own. They don't really fit anyway. Any other suggestions? I will edit this afterwhile unless someone points out I'm misunderstanding something here.Racerx11 (talk) 07:11, 5 September 2010 (UTC)

The comments are unsourced, but appear to be referring to this discovery. Perhaps working the source into the article would help clarify matters. Serendipodous 08:34, 5 September 2010 (UTC)

I've changed the word "unclear" to "not universally agreed upon" and clarified what it is that they are in disagreement about, i.e. "One definition of a sub-brown dwarf is a planet-mass object that formed through cloud-collapse rather than accretion. This formation distinction between a sub-brown dwarf and a planet is not universally agreed upon". and added a reason why there isn't agreement: "One reason for the dissent is that oftentimes it may not be possible to determine the formation process: for example an accretion-formed planet around a star may get ejected from the system to become free-floating, and likewise a cloud-collapse-formed sub-brown dwarf formed on its own in a star cluster may get captured into orbit around a star." (talk) 16:28, 5 September 2010 (UTC)

very good. Much better I think. thanksRacerx11 (talk) 01:32, 6 September 2010 (UTC)

Deuterium-burning planets?

This article asserts at several points that the ability to fuse deuterium is the distinction between planets and brown dwarfs. Unfortunately this violates NPOV: there is an alternative viewpoint which has a significant number of adherents that the upper limit of the planetary mass domain should not be set by capability for fusion, but rather the object's formation history. A couple of references for example:

From Baraffe et al. (2008):

Guided by the results of Mordasini et al. (2008), we have considered a 25 MJ planet with a 100 M core. Independently of the composition of the core material (water or rock), deuterium-fusion ignition does occur in the layers above the core and deuterium is completely depleted in the convective H/He envelope after ∼ 10 Myr. The same conclusion holds for a core mass of several 100 M . These results highlight the utter confusion provided by a definition of a planet based on the deuterium-burning limit.

From Lee et al. (2009):

From a theoretical argument based upon mass, brown dwarfs (BDs) should be born with masses between the least massive stars of ∼75 MJup and the most massive planets of ∼13 MJup (Burrows et al. 2001). However, observational results (Grether & Lineweaver 2006; Udry & Santos 2007) indicate that the BD and planet populations overlap in the 10-20 MJup interval so it is not possible to differentiate between low-mass BDs and high-mass giant planets from measured masses alone.

In any case, the deuterium burning limit is also metallicity dependent, so giving the value of 13 Jupiter masses is misleading (a recent arXiv paper on this topic is available here). Icalanise (talk) 20:36, 18 September 2010 (UTC)

Presumably the above quote that says there is an overlap between planets and brown dwarfs means there is an overlap in the mass range between objects orbiting stars and objects formed on their own. Now that being the case the overlap range is actually much wider than 10-20. There is no upper limit that says an object is too massive to be orbiting a star, and there are objects formed on their own that are smaller than 10Mj. (talk) 08:36, 19 September 2010 (UTC)

The lowest-mass example I can find is: the paper Dusty Disks at Bottom of IMF describes a candidate 3 Mj object ( an isolated planetary-mass object IPMO). (talk) 08:53, 19 September 2010 (UTC)

Without checking references, I pretty much thought anything 8-13 Mj was in the grey area of planet/brown dwarf. It wouldn't be much of a shocker to see the upper limit could extend to 20-25 Mj. Some models suggest Saturn's core (9.7ME) may be more massive than Jupiter's (8.3ME). Pluto is in the grey area of being a planet except that we have an IAU rule that says it is not. :) -- Kheider (talk) 11:55, 19 September 2010 (UTC)

planets in the universe

Interesting theory, there's just no actual evidence to support the idea of planets in other galaxies. What evidence is there for other solar systems with planets outside of our own? (talk) 19:26, 1 January 2011 (UTC)

Plenty. See: List of extrasolar planets. Serendipodous 19:38, 1 January 2011 (UTC)
I'm aware there's a list of planets (however did not know the list was generated so recently, only as of 1995), the question is what is the evidence for these planets listed. What's the strongest evidence for any one in particular? (talk) 23:20, 1 January 2011 (UTC)
See: Extrasolar planet. Serendipodous 23:29, 1 January 2011 (UTC)
Okay, from that link "The vast majority have been detected through radial velocity observations and other indirect methods rather than actual imaging." Then there's a b/w depiction from these indirect methods. The critics of 'big bang' theory reason the planets did not cool down slowly. Also, Robert Gentry has shown the planets did not cool down slowly by examining the baserock granites. If this is true then planets do not form as claimed. If they do not form as claimed there may be no other planets. But, we have this indirect image. If only we could independently verify it. We'll find out some day. (talk) 05:34, 2 January 2011 (UTC)
The planets around HR 8799 have been confirmed via infrared direct imaging since the star is only ~100 light years away. -- Kheider (talk) 09:32, 2 January 2011 (UTC)
Indeed. This system was also imaged by coronagraph. See also, Fomalhaut b, which was coronagraphically detected in visible light by the HST. If dear old Hubble can do it, we should probably expect to see many more direct images from more specialised future planet finding missions. Several brown dwarfy things have been spotted in infrared as well. MrAngy (talk) 10:51, 3 February 2011 (UTC)

satellite security

Jupiter has the most secured satellites (63) in the solar system.

What does 'secured' mean? Verified? Unlikely to be torn from Jupiter's embrace? (If the latter, in contrast to what?) Something else? —Tamfang (talk) 10:10, 19 January 2011 (UTC)

It was added in this diff. Seems to be referring to known moons, even those moons without official names yet. HumphreyW (talk) 11:17, 19 January 2011 (UTC)

Revision of the article

I have used this article as basis for a general revision of the Portuguese version. In spite of its high quality, I was able to find some minor flaws, which I cannot correct because the article is under protection. How can these corrections be done? Claudio M Souza (talk) 20:42, 27 February 2011 (UTC)

Just tell me what the problem is. Or edit for four days. Serendipodous 20:42, 27 February 2011 (UTC)

OK, here are the comments I have:

1) Introductory text, paragraph that starts with " The planets were thought by Ptolemy…":

In the phrase: "As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some share such features as…": for the sake of coherence, it should read "the planets rotated … and some shared…"

2) Chapter History, paragraph that starts with " In ancient times, astronomers noted…":

In the phrase: "… and the apparently common sense perception that the Earth was solid and stable, and that it is not moving but at rest.": again for coherence, it should read "that it was not moving…"

3) Chapter India:

In the phrase: " Ayrabhata's followers were particularly strong…": the name is misspelled, the correct is Aryabhata.

4) Chapter Medieval Muslim astronomy:

The text "…which was later identified as the transit of Mercury and Venus by the Maragha astronomer Qotb al-Din Shirazi in the 13th century." must be followed by "However, Ibn Bajjah could not observe a transit of Venus, as none occurred in his lifetime.", as is mentioned in the article "Transit of Venus".

5) Chapter European Renaissance, paragraph that starts with "Thus the Earth became included …":

This case requires some research. In the phrase "…the terms "planet" and "satellite" were used interchangeably – although the latter would gradually become more prevalent…", it seems to me that the more prevalent was "planet" (the former), and not "satellite" (the latter), but I have no access to the reference. I hope the experts in the subject can clarify this point.

6) Chapter 21st Century, title of the box:

"Planets from 2006 to presente". Word mispelled: "present" ("presente" is Portuguese!)

7) Chapter Mythology and naming, first paragraph:

The phrase " The Greeks also made each planet sacred to one of their pantheon of gods…" should be revised, for "pantheon" is the collective noun for gods. I suggest: "…sacred to one among their pantheon of gods…"

8) In the same chapter and paragraph:

In the phrase: "Phosphorus was ruled by Aphrodite…", substitute the name for "Phosphoros, as is spelled before, in the same paragraph.

9) Same chapter, paragraph started with " Some Romans, following a belief possibly originating…":

In the phrase: " after the Nundinal cycle was rejected – and still preserved many modern languages.", correct for "…still preserved in many modern languages."

10) Same chapter, paragraph started with " Since Earth was only generally accepted…":

This paragraph shows two theories for the origin of the name "earth", one saying it comes from ancient Anglo-Saxon word "erda" and the other from the ancient Germanic word "ertho". Maybe both are correct and there is a link between both ancient words, but the text is confusing. In my translation I simply abandoned the first theory and I suggest you do the same in the English version.

11) Chapter Formation, paragraph that starts with " When the protostar has grown such…":

The phrase: " Meanwhile, protoplanets that have avoided collisions may become… either dwarf planets or small Solar System bodies." is not coherent with the objective of the chapter, which deals with the formation processes of planets in any star system, not only in our Solar System. I suggest to write "…either dwarf planets or small bodies" and include a reference in "small bodies" addressing to "Small solar system body".

12) Chapter Atmosphere, paragraph that starts with " Hot Jupiters have been shown…":

The name of the planet "HD 189733b" is lacking a space: "HD 189733 b".

13) Chapter Magnetosphere, paragraph that starts with " In 2004, a team of astronomers in Hawaii…":

In the phrase " which appeared to be creating a sunspot on the surface of its parent star", I think "sunspot" should be changed into "spot", for it is dealing with a star other than the Sun.

That's it. I appreciate your help in case you accept to perform these corrections in the article.Claudio M Souza (talk) 03:17, 28 February 2011 (UTC)

Thanks for vetting this; this article has been heavily fiddled with and I shouldn't have left it to rot. Not sure about the planet/satellite history; will look into it. I reworked the "earth" paragraphs so they made more sense. I think I'll leave "sunspot" though- the correct generic term is "starspot", but I can't expect lay readers to know what it means. Serendipodous 15:17, 1 March 2011 (UTC)

A minor note

Section Formation:

It is not known with certainty how planets are formed. The prevailing theory is that they are formed during the collapse of a nebula into a thin disk of gas and dust.

But AFAIK, there is no surviving alternative to the "nebular theory", the latest alternative was the deceased Jeans theory of a near stellar passage. The "nebular theory" has however numerous variants, the current ones usually involving protoplanets and possibly "oligarchs" in various time stages, the only thing in common between them being that they all presume an original disc formed solar nebula. Rursus dixit. (mbork3!) 17:37, 6 March 2011 (UTC)

Wrong caption/image

The first image in this article shows 2 big planets in the background labelled as Uranus (left) and Neptune (right). But 'Neptune' looks a lot like Jupiter. From other images of Neptune, the planet is supposed to appear bright blue. ќמшמφטтгמtorque 12:12, 12 March 2011 (UTC)

I'm an amateur here, but will try to answer: Jupiter isn't blue, Neptune is. Its blue tint depends on the observing instrument (see Neptune). Its atmosphere in the picture is fake, as admitted in the image description and here. Materialscientist (talk) 12:33, 12 March 2011 (UTC)
Ok, thanks for the answer. I thought there was an error or something because the atmosphere of Neptune really looks like Jupiter's atmosphere to me and because it looks nothing like any of the images we have in the Neptune article. ќמшמφטтгמtorque 14:10, 12 March 2011 (UTC)
Indeed, so the question remains whether that simulated atmosphere is appropriate for the image. Materialscientist (talk) 14:15, 12 March 2011 (UTC)
It looks to me like pictures taken with a color filter (perhaps in ultraviolet), in which case the blue tint is misleading. — Isn't Neptune bigger than Uranus? —Tamfang (talk) 21:11, 12 March 2011 (UTC)
Neptune and Uranus are roughly the same size, but Neptune is more massive, so it is denser. Serendipodous 21:13, 12 March 2011 (UTC)
Technically Uranus (due to lower mass and density) has the larger diameter. As for the activity in the atmosphere of Neptune: It is referenced to a fictional map by Don Davis located at NASA Solar System Simulator (as Materialscientist pointed out above). I do not see why Neptune could not be that active on rare occasions. I also think the Voyager flyby of Uranus probably caught Uranus at an unusually low activity level. -- Kheider (talk) 21:28, 12 March 2011 (UTC)

The pictures at the top of the page

They show several non-planetary objects, so why are those being used? (talk) 21:33, 17 April 2011 (UTC)

Regarding this Nature article ...

See here. They don't satisfy the definition of a planet in the lead of this article ... but I presume people will come here looking for information on these objects. Is there an official term for these objects? Do we have an article on them? And if yes, should we mention them in the lead of this article? Cheers, Ben (talk) 15:16, 19 May 2011 (UTC)

Oops, I read beyond the extrasolar planets section and found rogue planet. Any chance we can mention this in the lead of this article in the same paragraph as we mention extrasolar planets? Cheers, Ben (talk) 15:20, 19 May 2011 (UTC)
Technically no, since a planet must orbit a star, and therefore a "rogue planet" cannot be a planet. Serendipodous 15:22, 19 May 2011 (UTC)
Also planet like objects such as our moon, or Saturn's Titan, are not planets because the orbit a planet. By definition a planet must orbit a star. -- Kheider (talk) 16:10, 19 May 2011 (UTC)
Right, but I still believe people will come to this article looking for information on rogue planets. This article has a section on that topic, which is great, but perhaps we can mention them briefly in the lead too (which is consistent with WP:LEAD due to the existence of that rogue planet section in this article) to help guide these readers. Does this seem reasonable? Cheers, Ben (talk) 22:00, 19 May 2011 (UTC)
How abput a disambig link at the top {{for| ... see rogue planet.}}}--Salix (talk): 23:39, 19 May 2011 (UTC)

Does this article need an overhaul?

I'm particularly interested in redrafting the history section; the article's lead contains references to Galileo and Kepler, which don't get elaborated on in the history section, and the history section contains several unsourced statements. Serendipodous 18:46, 2 June 2011 (UTC)


The formal IAU def belongs in a section on definitions, but not in the first line of the lede, or perhaps even in the lede at all. Brown makes a this point in How I Killed Pluto: astronomy is not based on definitions, it's based on concepts. There is no formal definition of a star, or a moon, or a galaxy. The current IAU definition of a planet is merely a way to disqualify Pluto, because people want to make it an exception to the concept of a planet that disqualified Ceres etc. That is, he sees the definition as an attempt to explain the concept. He says, "The concept of a planet—in the eight-planet solar system—is equally simple to state. A planet is one of a number of bodies that dominates a planetary system." IMO he's right, and we should say something more along these lines in the lede. — kwami (talk) 07:06, 21 August 2011 (UTC)

The problem is that that definition is fairly vague, and in trying to make it more specific, we'll just end up restating the IAU definition anyway. Serendipodous 07:32, 21 August 2011 (UTC)
But... how does Brown define a planetary system? Cheers, Greenodd (talk) 08:13, 21 August 2011 (UTC)
Correct, we cannot use his wording. It wasn't intended for the lede of an encyclopedia article. I think his approach is that everyone knows what it means without getting legalistic about it. There's the gas giants, the terrestrials, and then a bunch of other stuff: the asteroid and Kuiper belts, comets, etc. The first two groups are lumped together under 'planet', the rest are 'minor planets' and comets / DP's and SSSB's / subplanets and debris. I think we can come up with something which is not as bureaucratic as the IAU def. I dunno, maybe s.t. like,
A planet is any of a number of bodies that dominate the material orbiting a star
By implication, that would exclude another star, though maybe we would need to say that explicitly. It would also avoid the problem of Jupiter not being a planet because it doesn't orbit the Sun—the rational the IAU had used to declare Charon a planet. But y'all can probably come up with something more elegant.
For Brown, Sedna is not a planet, and it wouldn't be even if we knew there was nothing else out there and that it had 'cleared its orbit', but by the legalistic def it would be one. — kwami (talk) 03:42, 22 August 2011 (UTC)
There are rogue planets, too. I would rather think in terms of planets having an atmosphere. Cheers, Greenodd (talk) 10:14, 22 August 2011 (UTC)
Mercury does not have an atmosphere so you are back to a techincal definition that says a planet must clear its region of similar sized objects. -- Kheider (talk) 10:23, 22 August 2011 (UTC)
It's thin, but Mercury does have an atmosphere. That said, my thought was that 'could have' suffices. Greenodd (talk) 11:42, 22 August 2011 (UTC)


The first sentence of the second paragraph of the section called Babylon states:

"The Sumerians, predecessors of the Babylonians who are considered as one of the first civilizations and are credited with the invention of writing, had identified at least Venus by 1500 BC.[16]"

This sentence about the Sumerians identifying Venus by 1500 BC seems inaccurate. According to the article referenced, the Sumerian period ended in 2300 BC, and 1500 BC was in the Middle Babylonian period. The referenced article also makes the following statement, which seems contrary to the idea that the Sumerians had identified Venus:

"Writing was invented by Sumerians ca 3200 BC. Cuneiform1 tablets of Sumerian period give us very interesting material but unfortunately no astronomical or astrological texts."

In addition, the sentence mistakenly uses a relative clause ("who are considered...") to incorrectly identify the Babylonians as one of the first civilization as well as being credited with the invention of writing. Although that identification belongs to the Sumerians, it is, in fact, irrelevant regarding the topic. (talk) 07:20, 12 December 2011 (UTC)