Talk:Solar System

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Solar wind speed

Heliopause Solar wind speed should be 400 km/h not 40,000 km/h --Suslik666 (talk) 21:39, 26 February 2009 (UTC)

Source? Actually, it's 40,000 kilometers per second. Serendi^podous 21:48, 26 February 2009 (UTC)

Sorry about the "km/h". I ment "km/s". I looked many different articles about solar wind. As a result i became very confused. I still am very confused, because you just told me that it is 40000 km/s. Now lets look Reference 56. I dont understand most of that "thing". There is a graph where one can read v(r) [ms^(-1)] 4*10^(-7) ms^(-1) at 100 AU which really is 40000 km/s. Now There is also a sentence in there "Assuming a solar wind proton density of about 5 [cm^(−3)] and a solar wind speed in the order of 4*10^7 [cm*s^(−1)] photoionisation is a 10–15% effect with respect to the charge exchange and the above approximation of a solar-distance-independent, spectral EUV-flux only plays a minor role." [cm] in text, [m] on graph! 4*10^7 [cm s^(−1)]= 400000 m/s = 400 km/s. There is another sentence in that text. "The radially symmetric outflow of the unperturbed solar wind flow is described with a bulk velocity of 400 km/s, a proton temperature of 105 K and a proton density of 5 cm^(−3) at the orbit of the earth." Maybe these things got mixed up and as a result of this 40000 km/s was entered instead of 400 km/s. There is another way of looking at this. My english is weak. I dont understand that reference page, im not that good in physics. Those things there could be 100% correct. After googling "solar wind speed" i found out that the speed of solar wind should be in the range of 300-800 km/s. Average speed would be ~400 km/s. Speed of light is ~300000 km/s. 40000 km/s would seem a bit too high? What part of this i cant understand? I hope someone would explain it to me. Suslik666 (talk) 01:57, 27 February 2009 (UTC)

I think you may be right. I'll swap it. Serendi^podous 10:16, 27 February 2009 (UTC)

Solar_wind#Emission mentions 400 km/s (at the Earth orbit) to 750 km/s Ref: On the sources of fast and slow solar wind -- Kheider (talk) 16:56, 27 February 2009 (UTC)

Aren't There STILL Nine Planets?

There has been lots of "unofficial" talk about whether or not the Moon, supposedly Earth's "satellite", is actually a major planet in its own right. When you read the present definition of planet, recently changed by the International Astronomical Union (IAU), you find that this new definition does NOT exclude our Moon.

So I would like to propose a discussion on this topic. Isaac Asimov, before he died, wrote science books on the Moon, and he came up with several reasons why the Moon ought to be thought of as more than just a satellite of Earth. Asimov proved (well, to me anyway) that the Moon is a full-fledged planet in its own right.

You can read more about this fairly controversial subject at the "official" website of... The Planet Moon. This website is dedicated to Isaac Asimov.

Whether or not you read the above website, your opinion about this topic would be very interesting to hear. So let's us talk about whether or not the "Solar System" still has NINE planets, or just eight.

Paine Ellsworth (talk) 13:22, 1 March 2009 (UTC)

A Wikipedia talk page is NOT a place for discussion, please go to another website if you want to talk about whether the moon is a planet or not. Williamrmck (talk) 13:35, 1 March 2009 (UTC)

A Wikipedia talk page is not a place for a discussion about whether or not the moon is a planet. But it is a place for a discussion of how we should edit Wikipedia's articles for their information about whether or not the moon is a planet. - Shaheenjim (talk) 14:41, 1 March 2009 (UTC)

But it's not Wikipedia's job to advocate alternative hypotheses, especially hypotheses advocated by people pushing their own websites. And anyway, that particular controversy is discussed perfectly adequately over at Definition of planet. Serendi^podous 14:59, 1 March 2009 (UTC)

Advocate hypotheses, no. Educate people about hypotheses, yes. As evidenced by the fact that, as you said, Wikipedia already covers it on another article. - Shaheenjim (talk) 15:25, 1 March 2009 (UTC)

To echo Serendipodous, these pages are not here to debate alternate theories. No disrespect to Paine, but the web site represents his/her personal theories, and has not demonstrated that it meets the requirements of WP:RS, WP:N, or WP:V. We cannot use it as a reference for changes to text based on established verifiable material. (As such, I have had to revert the changes to Moon.) --Ckatz^chat_spy 20:36, 1 March 2009 (UTC)

I do remember saying that the Moon-as-planet issue is controversial. However, I did not ask the question to become embroiled in any kind of debate over validity. I am asking, "Aren't there still nine planets?" because by the new definition, that can be found on the Definition of planet page, the Moon is clearly NOT excluded. So by definition, then, the IAU has included the Moon as a planet. And this fact should be clearly noted in ANY appropriate Wiki article on the Moon. --Paine (talk) 23:13, 1 March 2009 (UTC)

And now I feel responsible for other issues revealed above, to wit...

1) Williamrmck admonishes that a talk page is NOT a place for discussion? A "TALK" page is NOT a place for "DISCUSSION"? Please, someone! What is wrong with this picture? Never mind, because I do get the point. I did not ask this question specifically to discuss whether or not the Moon is a planet. I asked the question because when I read the presently accepted IAU definition of "planet", I see nothing in it that excludes the Moon. And I want to discuss whether or not it is appropriate to include this FACT on any Wikipedia page that is Moon-informative.

A talk page is for discussing how to improve articles, not for discussing issues raised by articles. Serendi^podous 09:10, 2 March 2009 (UTC)

2) Serendi^podous, I'm not asking Wikipedia to advocate or not advocate ANY hypothesis. No encyclopedia should do that. What I am asking is for Wikipedia to bring to attention the obvious fact that the IAU definition of "planet" does NOT exclude the Moon. As for pushing my own website, I am sorry if that's what you think. I did not want to discuss here whether or not the Moon is a planet, so I opened that discussion topic on my talk page, and I included the reference so people would be informed of Asimov's and my reasons for considering the Moon to be a planet. I fully recognize that this talk page is supposed to be about appropriate content only, such as noting that the IAU definition of a planet does not exclude the Moon.

Not true. Resolution 5a section 2d specifically excludes satellites from consideration. And for now, despite the opinions of Dr. Asimov, who is given ample voice over at Definition of planet, the Moon is still a satellite. Serendi^podous 09:10, 2 March 2009 (UTC)

3) Ckatz^chat_spy, in case you hadn't gotten back to my talk page yet, I want you to know that I have altered the links to exclude any bad references. As a Wikinewbie, I will try to get myself up to snuff as quickly as possible. Thank you for your kind post to my talk page explaining what I had done wrong. As for removing my site as a reference on the Moon page, don't give it another thought. At first, I felt rather honored, however it did seem a little unusual. At any rate, thank you for your help and comments. And thank you all! --Paine (talk) 01:47, 2 March 2009 (UTC)

My (Kheider's) observations

1. It is not really a NPOV since it reads biased (IMHO).
2. Phobos and Deimos are considered captured asteroids, so the usage of "true satellite" is iffy. Nereid has been heavily perturbed by the capture of Triton.
3. Does not cover the very important Giant impact hypothesis.
4. The moon did a bad job of dominating the Earth (So only 8 planets under the current IAU definition; the moon would be at best a dwarf planet).

But I do agree about one thing, if they bring Pluto back as a planet I hope the seven moons larger than Pluto get fair treatment. -- Kheider (talk) 02:13, 2 March 2009 (UTC)

(re: 1) On this point we agree. I intend to improve it over time.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  14:45, 23 April 2009 (UTC)

(re: 2) Actually, Phobos and Deimos both have near-circular orbits almost precisely on Mars' equatorial plane. This pretty much shatters the "captured asteroid" hypothesis. They are far more likely to have been formed along with Mars from the beginning, so they must be "true satellites" under Asimov's definition.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  02:25, 23 April 2009 (UTC)

I am glad your opinion shatters professional opinions. ESA (and others) still think the moons might be a result of capture or a large surface impact on Mars. It is always dangerous to make assumptions. -- Kheider (talk) 04:42, 23 April 2009 (UTC)

Agreed. And while there are astronomers who favor the captured asteroid hypothesis, none of them like the odds of any planet capturing objects that "fall" into near-circular orbits almost precisely on the planet's equatorial plane. It is in fact quite a stretchy assumption to call Phobos and Deimos captured asteroids. Astronomers as a rule will acknowledge that there is much more to the Solar System than we as yet know.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  05:37, 23 April 2009 (UTC)

No one claims that anything fell into a circler orbit. Circler orbits take time to evolve. *If* there was ever a debris field around Mars it would have been easier to make the orbits of Phobos and Deimos less eccentric. -- Kheider (talk) 20:47, 23 April 2009 (UTC)

(re: 3) I'd like to mention in passing that, while the GIH is "very important" and is the most widely accepted explanation for the origin of the Moon, and while computer models do yield its possibility, those models also show the high odds against due to the near-circular orbit of the Moon and its orbit's very near proximity to the ecliptic.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  14:41, 23 April 2009 (UTC)

(re: 4) This is at best a subjective judgement. The Earth and Moon have dominated each other quite well, actually. And if you'll compare the definitions of planet and dwarf planet, you'll find that the Moon fits the planet definition.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  14:41, 23 April 2009 (UTC)

You are giving the moon too much credit as an object that formed in orbit around the Earth. The moon is currently inclined 6.5° to the invariable plane of the solar system. (The Earth is inclined 1.57°) The moon has a mass of 7E22 and Earth has a mass of 6E24, thus the moon is basically submissive to the Earth. The moon is not yet tidally locked to the Earth, but it has been working towards it for 4 billion years. Triton is likely a captured dwarf planet and it has a circler orbit. The gas giants migrated (Nice model) and they have basically circler orbits. -- Kheider (talk) 20:47, 23 April 2009 (UTC)

You misunderstand– I did not say that the Moon formed in orbit around the Earth. I said that the Earth and Moon are both in a binary-planet orbit around the Sun. The Earth/Moon barycenter orbits the Sun in an elliptical path, while the Earth and Moon orbit the Sun in "scalloped" patterns. This fact leads to the possibility that the Moon formed in its own orbit around the Sun that was very near Earth's orbit. At some point very early in the formation of the Solar System, the slower object is overtaken by the faster object and the Earth and Moon "capture" each other. Then they go into their mutual binary-planet orbit that we see today.

The Moon's inclinations to the ecliptic and to the invariable plane are excellent considerations. If the Moon were truly a satellite of Earth, it would orbit squarely on Earth's equatorial plane. Instead, it orbits only 5 degrees off the ecliptic and, as you say, 6.5 degrees off the IP. And this is how one would expect a planet to orbit rather than a satellite. (Mercury orbits the Sun even farther off the ecliptic than the Moon, about 7 degrees.)

Not sure what you mean by saying the Moon is not tidal-locked to Earth? It has been so for eons. If you're referring to the librations, then yes, the tidal locking is not "perfect". But the Moon is definitely "locked in" tidally to the Earth, and if the Sun had more than 5-7.5 billion years left to shine, Earth would eventually become tidal-locked to the Moon.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  15:42, 24 April 2009 (UTC)

Interesting that you should mention the deeply controversial dwarf-planet Pluto. I lobbied to get this classification change mainly to help the Solar System astronomers who were analyzing the tons of data on TNOs. Speed of collating all that data was tremendously improved by the reclassification of Pluto. The upcoming IAU meetings should prove to be fascinating! full of debate on this issue!  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  15:55, 24 April 2009 (UTC)

The IAU resolution

The IAU resolution adopting the definition explicitly lists the 8 planets. Peter jackson (talk) 11:03, 30 March 2009 (UTC)

And yet the definition itself is not worded such that it excludes the Moon from being a planet.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  02:25, 23 April 2009 (UTC)

Mars' Rotational Momentum Anomaly

Since the Martian satellites were mentioned, I wonder how appropriate (or not) would it be to mention the rotational velocity anomaly? I.e., when the Martian day is compared with Earth's day one finds that they're about the same, right around 24 hours. Now, Earth's day has been lengthened over the eons by the close proximity of an enormous object, the Moon. Since neither Phobos nor Deimos are nearly as large as the Moon, and since the day on Mars has lengthened at about the same rate as the day on Earth, the question arises as to what caused Mars to slow its rotation over the eons?  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  02:25, 23 April 2009 (UTC)

Interesting point; not really relevant to this article. Might be a good addition to Tidal acceleration, assuming you could find the right sources to back it up. Serendi^podous 13:06, 23 April 2009 (UTC)

As far as I know, I'm out of luck on the backup sources on this issue. It probably constitutes original research, for I've never seen anything written about it. Astronomers make the logical assumption that the isochronous rotation rates (near the bottom of that page) of the asteroids and the spin rates of the outer planets mean that the inner planets also rotated much faster 4 billion years ago. As you know, the tidal action between Earth and Moon resulted in a transfer of angular momentum from Earth to Moon. And the two main results were the Moon's proximity growing farther away and the Earth's spin rate slowing. Mercury and Venus are probably undergoing a tidal-locking process with the Sun. Astronomers seem to think that Mercury is already locked in a weird 3:2 relationship, but I think that if the Mercurial spin is studied more closely, we'll find that it is changing, that Mercury is slowly headed for a 1:1 tidal lock. Venus, which presently rotates in a direction opposite to most other planets, also probably has a changing spin rate, as the locking process causes it to oscillate past the 1:1 lock point a few times. Earth is close enough to the Sun for there to be a possible tidal-locking effect with the Sun, but by far the thing that's slowed Earth's rotation to 24 hours was the proximity of the Moon. I've never seen anything in print about it, but I've always questioned what might have caused Mars to slow its rotation so dramatically. Certainly not the Sun for Mars is too far away for the Sun's tidal effect to have caused that much slowing. Certainly not Phobos and Deimos, for they are way too small to have slowed Mars' rotation that dramatically. And yet, there it is, our mysterious red neighbor Mars. It's spin rate is actually a tad slower than Earth's. So what in the name of "heaven" could have robbed it of its initial angular momentum? Perhaps a series of collisions? I don't know.  ^{.`</sup>^) Paine<sup>diss`cuss} (^^`.  14:17, 23 April 2009 (UTC)

Distances to Planets

Hi there guys,

It seems that the distances from the Sun to the planets represent the main aspect of scale of our star system. Therefore, I think you could say that the "size" of the Solar system is based on these measurements. As such, I think this data is worthy of mention at the start of the article : ) What do you think?

InternetMeme (talk) 11:03, 17 March 2009 (UTC)

After a cursory glance, I've noticed that there is no indication of the size of the Solar system in the opening section. I'd say that the size and shape of an object are two of the most basic aspects that need to be described in the first section of any encyclopedia article.

Also, astronomical units are not much use to any ordinary person. "giga" has become a fairly well known prefix, due largely to computer storage capacity measurements, and "metre" is a worldwide unit used everywhere apart from a couple of third-world countries and the US : )

InternetMeme (talk) 11:22, 17 March 2009 (UTC)

The Solar System has no single, fixed size. It depends on how you define it. If you mean, "the bits we've mapped," then it goes out to about 80 AU. If you mean, "the region of space dominated by the solar wind," then that's about 120 AU, and if you mean, "the region of space dominated by the Sun's gravity", then you're talking about around 200,000 AU. Either way, simply listing the distances to the planets and those arbitrary objects we now call dwarf planets will not give anyone a good idea of the dimensions of the Solar System. As for AU, it is the established unit for interplanetary measurement and it would be unnecessarily confusing for Wikipedia to use anything else, since all credible sources use it. The term is defined at the bottom of the page. Serendi^podous 13:22, 17 March 2009 (UTC)

Since this is a general article for the masses, we would need to stay away from gm and use km... -- Kheider (talk) 14:43, 17 March 2009 (UTC)

I think that although Astronomical Units are a reasonable unit for use in specialised astronomical publications, I think they're not a great unit to use in a general purpose encyclopedia aimed at the masses; the masses view units like that as kind of sci-fi space jargon, and they don't really take it in. And sure you can define the unit at the bottom of the page, but that still won't give people any idea of the scale of planetary distances. For example, the distance from Earth to Venus is roughly 2,000 times the distance from China to the US. That's easy to work out when you use kilometres. InternetMeme (talk) 10:50, 19 March 2009 (UTC)

It gives people a far better idea than battering them over the head with hundreds, thousands, millions and billions. At least AUs are simple; do you think people would prefer to count the zeroes at the end of 5000000000 km? In astronomy, oblique measurements are used all the time. Take light years. Most people probably don't even know what a light year is, let alone its value in km. Telling them that Alpha Centauri is 4.5 light years away has no more or less meaning than saying it's 25 trillion miles away; a number as ponderous as counting the grains of sand on a beach. These numbers are so far out of human experience that there really is no way to express them in ways they will grasp. Not even astronomers can do that. Besides, the AU is used not only in this article but in every Solar System-related article on this site. The change you are advocating would require massive work for little (and dubious) gain. Serendi^podous 13:38, 19 March 2009 (UTC)

I agree that most people view AUs as sci-fi space jargon. But this whole article is like sci-fi space jargon. So it's appropriate. - Shaheenjim (talk) 21:47, 19 March 2009 (UTC)

In regards to the Solar system having no fixed size: Well, I guess that's technically true, there are many different aspects of matter and energy distribution that could be regarded as the size of the Solar system. But I think that when most ordinary people envisage the Solar system, they think of the picture at the start of this article (which presumably represents this article's visual definition of the solar system). Therefore I think it's a good idea to give some scale to the visualisation.

Also, the list of the planets in this article is ordered by their distance from the Sun. It would seem fitting, then, to state what those distances actually are. InternetMeme (talk) 15:36, 17 March 2009 (UTC)

That picture isn't a picture of the Solar System; it's just a picture of the planets and dwarf planets with their sizes to scale. I would love to have a decent image of the Solar System to use, but none are available. Serendi^podous 15:47, 17 March 2009 (UTC)

Yeah, what I'd really like is a picture that indicates the relative orbital distances to scale, which would lessen the need to list the distances in the article. It's worth pointing out that the second paragraph states that the Oort cloud spans a distance of roughly a thousand times that of the main planetary region, without actually saying what the distance span of the main planetary region is. The relative meaninglessness of that statement is a good example of why some kind of scale indication is neccessary. InternetMeme (talk) 16:22, 17 March 2009 (UTC)

There is a picture of the orbits to scale; it's in the structure section. Serendi^podous 18:16, 17 March 2009 (UTC)

Might as well list all of those distances. And I agree that we should use AUs for distance. - Shaheenjim (talk) 22:01, 17 March 2009 (UTC)

Whatever happened to this? InternetMeme, you changed them away from kilometers, which hurts the size comparison by having different units, but also confuses people who use the long scale. That's not the issue, though - why were they not listed in AU to begin with, as per this conversation? ~ Amory 16:07, 20 April 2009 (UTC) —Preceding unsigned comment added by Amorymeltzer (talk • contribs)

I've restored the "km" version. --Ckatz^chat_spy 19:55, 20 April 2009 (UTC)

pls add IW link

[[wuu:太阳系]]

Solar system basic

The article Solar system basic, a fork of Solar System with a simplified writing style in line with the Simple Wikipedia, was created yesterday by HarryAlffa. I have nominated it for deletion both as a content fork and as something that is more suited to simple:Solar System. The AfD discussion can be found here if you are interested. --Ckatz^chat_spy 08:29, 21 April 2009 (UTC)

Lead needs to be rewritten

Pursuant to the FAR for this article, I believe the lead needs to be rewritten. In its current state, I don't think the article is a "concise overview of the entire article", rather it's a fairly simplistic list-like summary of what's what in the Solar System. In addition, given the size of the article (79 KB), there's definitely room to have a much lengthier and more comprehensive lead. Perhaps we could have a few sentences devoted to the Sun, a few to the Inner Solar System, a few to the Outer Solar System, etc etc. Nishkid64 _{(Make articles, not wikidrama)} 16:59, 23 April 2009 (UTC)

As the re-written lead has many of the same characteristics, I've copied over the lead from Solar system basic, which is a good start.HarryAlffa (talk) 14:54, 24 April 2009 (UTC)

See http://en.wikipedia.org/wiki/Wikipedia:Featured_article_review/Solar_System/archive1#Solar_System for discussion on the new, expanded lead. —Preceding unsigned comment added by HarryAlffa (talk • contribs) 17:26, 24 April 2009 (UTC)

Comment First, per the observations of several other editors, we should centralize this discussion at Talk:Solar System. Second, I have restored yesterday's version, and would ask that any changes to the lead be hashed out on a talk page first, and only applied after consensus is reached. Solar System is a core article, one of the most important ones in the "Astronomy" section, and we cannot have the lead going back-and-forth. Fair enough? (I was going to post a copy of the revised version here, but instead thought you could decide which revised version you wanted to start from.) --Ckatz^chat_spy 18:17, 24 April 2009 (UTC)