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On this page it says the sun will be a red giant in 5 billion years, but on the red giant page, it says 6 billion. Does anyone know so we can have consistand info? Jaderaid 12:36, 20 March 2006 (UTC)
I don't see anywhere in the article about how long the sun will last and its eventual fate. From some sources, I heard it's 5 billions years. Please include this information. Thank you. -- 141.213.196.250 03:42, 3 April 2006 (UTC)
Somebody keeps snipping that out. There used to be a "future of the sun" section.
this is amazing how hot can be one star.still over years looks impossible. —The preceding unsigned comment was added by Pentagonshark666 ( talk • contribs) 19:18, April 6, 2006 (UTC) how hot is the sun in degrees?
The Sun's surface is about 9,900°F and its core is about 10 to 22.5 million°F. Football (sport) 10:02, 19 May 2006 (UTC)
The surface of the sun has got an average temperature of 6000 degrees Celsius, while the core's temperature lies around 15 million degreess Celsius. 10.20, 4 August,2006, Lady Stardust
Just out of curiousity, has anyone ever measured the ambient temperature of Hell? Arch O. La Grigory Deepdelver 17:30, 5 September 2006 (UTC)
Our article states that it is 4.6 billion years old. Other sources such as [1] and this [2]. What is the basis of our claim? Capitalistroadster 07:06, 7 April 2006 (UTC)
Is it true that our Sun is the brightest star to be seen from one light year away? In other words, it's much much much brighter than all other stars in the greater neighbourhood? -- Sonjaaa 06:05, 20 April 2006 (UTC)
Since the Sun is about 4 billion years old and the Earth is 4.6 billion years old how has the Earth been around?
I'm not sure if this was already mentioned but the sun indirectly supports all known life on the planet yet the introductory paragraph states almost. Can this be changed?
"... causing aurorae, known as aurorae borealis in the northern hemisphere and aurorae australis in the southern hemisphere."
It's probably not a matter of great importance, but the plural of "aurora borealis" should be "aurorae boreales". Likewise for the southern variant ("australes"). However, it may seem pedantic to make the change, since the plural form is probably much less familiar than the singular. Also, I am not completely certain whether the adjective does not refer to another word instead of "aurora" (for instance "pole" or "hemisphere"), so I may be wrong anyway. -- Iblardi 16:28, 4 June 2006 (UTC)
There's a woefully ungrammatical sentence in the very first paragraph. I don't know enough about the topic to infer what was actually meant, but could someone more informed fix it up? Soo 17:23, 12 July 2006 (UTC)
The section on the Sun's magnetic field mentions that "All matter in the Sun is in the form of gas and plasma due to its high temperatures." I though that the material in the Sun was 100% ionized, so the amount of gas is trivial? -- Iantresman 19:50, 12 July 2006 (UTC)
Property | Plasma | Gas |
State | 99.99% | Trace |
Fusion | Yes | No |
EM emmission | Yes | No |
Magnetic field | Yes | No |
Magnetic reconnection | Yes | No |
MHD | Yes | No |
X-rays | Yes | No |
Electric currents | Yes | No |
Convection | Yes | Yes |
Some corrections:
As seems to happen frequently between us, Ian, I'm not quite sure what you're driving at. If you want the wording "...plasma (an ionized gas)" rather than "...gas and plasma", I don't see that as a problem. zowie 15:13, 13 July 2006 (UTC)
In the core of the sun it is so hot and such an high pressure, that it occours plasma. And what plasma really is, is free electrons and hydrogen (or helium)ions. Because of the heat and pressure has the hydrogen (or helium) molecules split up. That happens when the thermic energy conquers the connecting powers of two different electric loaded particles. But teoreticly seen I think one could call it hydrogen and helium plasma, even if it isn't physically right. 11.04, 4 August, 2006, by Lady Stardust
Please let me know if this has already been addressed, but the sun is central to a great deal of human culture, religion, etc. This article seems exclusively science-based and fails to address the importance that people attribute to the sun for cultural or other reasons. Is this addressed anywhere on Wikipedia? FunnyYetTasty 14:44, 13 July 2006 (UTC)
See also earlier Talk:Sun/Archive 01#Missing culture. For the religious aspects there already is the solar deity article (which could use some more prominent linking here however). For the fiction and other culture I think a separate sun in art and literature should be started. Femto 20:28, 13 July 2006 (UTC)
Why the second person? Who is "our"? So much for neutrality! savidan (talk) (e@) 17:22, 17 July 2006 (UTC)
Why are people cutting vast chunks out of this article [3]? What good does it do to remove that information from this article? I'm sure you could reproduce it elsewhere without removing it from a featured article. 62.249.214.195 14:25, 27 July 2006 (UTC)
Could anyone put more on history of human scientific understanding of the sun? Like history of attempts at measuring its distance from the earth.
I'm not sure if this is the most relevant place to post this (and please feel free to move it if it isn't), but in the section, "Development of Modern Scientific Understanding", the last paragraph states: "Finally, in 1957, a paper titled Synthesis of the Elements in Stars[28] was published that demonstrated convincingly that most of the elements in the universe had been created by nuclear reactions inside stars like the Sun."
Now I'm certainly no astronomer, but, by mass, doesn't Hydrogen (by far) comprise "most" of the elements in the universe? Further, virtually by definition, Hydrogen isn't created "by nuclear reactions inside stars". As such, should there be some distinction made in the article to show that in this reference "most" doesn't mean by mass but rather (I assume) by % of elements on the periodic table? 216.240.7.149 00:58, 29 October 2006 (UTC)
The accuracy with which we know the mass of the sun is limited by the accuracy with which we know the gravitational constant - we know GM_sun to about eight decimal places from observing the planets. Perhaps this is worth mentioning, and giving this number? (Or the mass of the sun in geometrized units) -- Andrew 20:31, 30 July 2006 (UTC)
Anyone mind if I remove the image with this caption: "Artist's conception of the remains of artificial structures on the Earth after the Sun enters its red giant phase and swells to roughly 100 times its current size."? Tony 07:38, 3 August 2006 (UTC)
How many people use Kelvin in every day usage? The temeperature should include Farenheit and Celsius. Dudtz 8/3/06 8:19 PM EST
Just subtract 273 from a kelvin and you get Celsius, it's pretty simple and Kelvin is the norm with planets -- Dulberf 04:44, 4 August 2006 (UTC)
That still does not help people who don't use Kelvin and Celsius. Dudtz 8/5/06 5:32 PM EST
Why not have the temperature in Farenheit? Dudtz 9/12/06 8:05 PM EST
By the way, guys and gals, its kelvins, lower case. Read the article. Urhixidur 03:16, 18 September 2006 (UTC)
Worldtraveller- Your personal attacks are really not cool. A British orthographic imperialist made a guideline-violating change here [4]. I corrected it, and fixed a few other things to make the article have a uniform spelling style. That's what the guidelines call for. I'm not pushing U.S. spelling. I'm pushing wikipedia guidelines. Other people are pushing U.K. spellings. But that seems not to bother you. If you want the British Empire to take over the world again, or enjoy attacking people for trying to improve wikipedia articles, please go elsewhere. -- Justice for All 02:16, 14 August 2006 (UTC)
"The Sun is the star at the center of Earth's solar system, but that's not important right now."
This is a weird way to open the article, don't you think?
I updated the mass of the sun and the equivalent number of Earths according to Measurement of Newton’s Constant Using a Torsion Balance with Angular Acceleration Feedback (Physical Review Letters; Vol. 85, Num. 14; 2 Oct. 2000) by Jens H. Gundlach and Stephen M. Merkowitz of the Department of Physics, Nuclear Physics Laboratory, University of Washington, Seattle, Washington 98195. They produced the most precise measurement of “Big G” yet with a value of 6.674 215(92) × 10–11 m3 kg–1 s–2. This allowed them to calculate the mass of the sun (1.988 435(27) × 1030 kg) and the mass of the Earth (5.972 245(82) × 1024 kg), and the equivalent number of Earths (332,946). Greg L 01:27, 24 August 2006 (UTC)
My physicist uncle suggested there may be a black hole at the center of the sun. Personnally I find this a plausible argument since the definition of black hole is something so massive that light cannot escape it. —The preceding unsigned comment was added by 164.107.166.152 ( talk • contribs) .
The density/gravity at the suns core is not high enough for a black hole -- Nbound 04:56, 2 September 2006 (UTC)
How can massless light not escape a black hole? Dudtz 9/12/06 8:11 PM EST
Has any man-made object ever made contact with the sun? I know it would never make it there, it would just burn up, but I am curious. -- Cngodles 15:54, 8 September 2006 (UTC)
The infobox was just changed to read ! align="left" | Surface temperature | 5785 K
This implies a precision of measurment to the degree. 5780 would imply +/- 5 degrees or so. I rather doubt we have measurements to the degree. Do we know a tolerance for this? RJFJR 17:42, 12 September 2006 (UTC)
The article states the solar luminosity is 3.9E28 lm (39,000 Ylm), which translates to about 3,100 Y cd (since the Sun radiates into 4π sr). This source states the solar illumination at Earth's equator at high noon is about 1000 lx. Using a 1 m² surface, we can compute it subtends a solid angle of about 1.787E-22 sr (using 1 AU distance), so the Sun's equivalent point luminosity is 5.6E24 cd (5.6 Ycd). The discrepancy is a factor of 554!
Which is right?
Urhixidur 02:28, 18 September 2006 (UTC)
This source states a V-magnitude zero star outside Earth's atmosphere puts out 2.54E-6 lx. The atmosphere transmits 82% in the visual, i.e. it dims 0.2 magnitudes. Since the Sun's V magnitude is -26.8, we're talking a 27.0 magnitude difference, hence the Sun is about 160 klx at ground level. This yields in turn a luminosity of about 900 Ycd. The discrepancy shrinks to a factor of 3.5.
The same source also gives a Mv=0 star outside Earth's atmosphere as = 2.45E29 cd. Since the Sun's Mv = 4.8, (5.0 on the ground), we have Sun = 2,450 Ycd.
Urhixidur 02:42, 18 September 2006 (UTC)
Yet another stab at it: the solar surface luminosity is given by this source as 2E9 nits (cd/m²); multiplying by the apparent disc (πr², not a bad approximation since there is little limb darkening), we get 3044 Ycd. Times 82% atmospheric transparency, about 2500 Ycd.
Clearly the very first source is wrong.
Urhixidur 03:02, 18 September 2006 (UTC)
Further update: various Sun luminances are bandied about:
The Sun's photospheric surface area being almost exactly 6×1018 m², the values above yield luminous intensities ranging between 5500 and 18 000 Ycd. I prefer to trust http://astro.kent.ac.uk/mds/507/ph507lecnote06-week1.doc, inasmuch as it takes into account the V filter's response curve. One can always argue the V filter is less sensitive than the human eye by a factor of between 1.8 and 6 times, in order to reconcile the figure with the luminances quoted above. The V luminance of the Sun is 0.484 Gcd/m², for comparison purposes.
Urhixidur 15:54, 18 September 2006 (UTC)
Zowie is quite right; I tend to share his "physicist's snobism" about the utter irrelevance of the human observer. But Wikipedia nevertheless has a responsibility to answer a child's question of « How bright is the Sun? ».
Searching the NASA ADS for a reliable value of the solar luminance or luminous intensity, I found M. Menat (1980), Atmospheric phenomena before and during sunset, Applied Optics, Vol. 19, (Oct. 15, 1980), pp. 3458-3468, which gives in figure 8 the apparent solar luminance during sunset/sunrise. The text states « the maximal average luminance of the Sun is about 1.5×109 cd/m² », which matches the mid-range value quoted earlier of 1.6 Gcd/m². Figure 9 is instructive, showing the zenithal spectral luminance peaking at 550 nm, which happens to be the monochromatic candela definition.
Menat, for the visibility function (equation 45), refers us back to:
Urhixidur 17:12, 18 September 2006 (UTC)
Going back to http://astro.kent.ac.uk/mds/507/ph507lecnote06-week1.doc, it turns out the « One star, Mv=0 outside Earth's atmosphere = 2.45×1029 cd » line is wrong by a factor of ten, and should read 2.45×1030 cd. This can be verified by looking a the other values quoted « 1 mv=0 star outside Earth's atmosphere = 2.54E-6 lux » and « 1 mv=0 star per sq degree outside Earth's atmosphere = 0.84E-2 cd/m² » and their conversions (into stilbs and phots). These are all cross-consistent. Plus, using the 2.54 µlx figure and scaling it to the Sun's apparent magnitude of -26.8, we do get 133 klx outside the atmosphere (109 klx inside), which matches the widely quoted maximum sunshine of 100 klx. Turning to luminance, we see the Sun puts out 3.75E+28 lm (which also matches the 100 lm/W value), corresponding to 6.16 Glm/m².
Turning to Menat's figure of 1.5 Gcd/m², it seems too weak by a factor of about 1/2. The Sun is a near-perfect Lambertian radiator, and therefore the illumination predicted by Menat's figure is 1.5 Gcd/m² × 1 Em² (a Lambertian sphere's flux is 2/3 πr² -see [8]) × 44.68 ysr (a square metre at 1 AU) ÷ 1 m² = 68 klx (×82% for the atmosphere = 55.8 klx). There's probably an error on my part here, can anyone spot it?
Urhixidur 19:45, 29 September 2006 (UTC)
Is there any particular order that is generally used for external links? If so, where can we find the guidelines? Rylan42 01:59, 24 September 2006 (UTC)
I've added some bits on the dangers of observing the Sun. I have laid it on a bit thick, but I think that is appropriate in this case. Man with two legs 10:41, 25 September 2006 (UTC)
For anyone watching here, I just redirected "The Sun" (i.e., with the definite article) to this page but expect to get reverted again. I'm surprised every day on the Wiki, but this was absolutely astounding. Any comments on that redirect talk page welcome. Marskell 23:22, 28 September 2006 (UTC)
I got rid of the "artist's conception" image because (A) it doesn't really focus on the Sun, (B) it is misleading. There is no reason to suppose that artificial structures will survive the intense heating from the red giant phase of the Sun's "life". Without some back-of-the-envelope justification, at least, for the presence of cracked mud and non-burned telegraph poles, the picture is misleading and worse than useless in this context. (Don't get me wrong, I think it's kind of cool -- just not appropriate here). Please discuss here before adding it back in. zowie 07:08, 14 October 2006 (UTC)
??? Zabrak 02:38, 28 October 2006 (UTC)
Copied from User talk:Howcheng:
The Dutch Wikipedia-page includes a table on solar evolution. I don't know how reliable it is scientifically, but it has some sources listed: http://nl.wikipedia.org/wiki/Zon Iblardi 19:24, 29 October 2006 (UTC)
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
On this page it says the sun will be a red giant in 5 billion years, but on the red giant page, it says 6 billion. Does anyone know so we can have consistand info? Jaderaid 12:36, 20 March 2006 (UTC)
I don't see anywhere in the article about how long the sun will last and its eventual fate. From some sources, I heard it's 5 billions years. Please include this information. Thank you. -- 141.213.196.250 03:42, 3 April 2006 (UTC)
Somebody keeps snipping that out. There used to be a "future of the sun" section.
this is amazing how hot can be one star.still over years looks impossible. —The preceding unsigned comment was added by Pentagonshark666 ( talk • contribs) 19:18, April 6, 2006 (UTC) how hot is the sun in degrees?
The Sun's surface is about 9,900°F and its core is about 10 to 22.5 million°F. Football (sport) 10:02, 19 May 2006 (UTC)
The surface of the sun has got an average temperature of 6000 degrees Celsius, while the core's temperature lies around 15 million degreess Celsius. 10.20, 4 August,2006, Lady Stardust
Just out of curiousity, has anyone ever measured the ambient temperature of Hell? Arch O. La Grigory Deepdelver 17:30, 5 September 2006 (UTC)
Our article states that it is 4.6 billion years old. Other sources such as [1] and this [2]. What is the basis of our claim? Capitalistroadster 07:06, 7 April 2006 (UTC)
Is it true that our Sun is the brightest star to be seen from one light year away? In other words, it's much much much brighter than all other stars in the greater neighbourhood? -- Sonjaaa 06:05, 20 April 2006 (UTC)
Since the Sun is about 4 billion years old and the Earth is 4.6 billion years old how has the Earth been around?
I'm not sure if this was already mentioned but the sun indirectly supports all known life on the planet yet the introductory paragraph states almost. Can this be changed?
"... causing aurorae, known as aurorae borealis in the northern hemisphere and aurorae australis in the southern hemisphere."
It's probably not a matter of great importance, but the plural of "aurora borealis" should be "aurorae boreales". Likewise for the southern variant ("australes"). However, it may seem pedantic to make the change, since the plural form is probably much less familiar than the singular. Also, I am not completely certain whether the adjective does not refer to another word instead of "aurora" (for instance "pole" or "hemisphere"), so I may be wrong anyway. -- Iblardi 16:28, 4 June 2006 (UTC)
There's a woefully ungrammatical sentence in the very first paragraph. I don't know enough about the topic to infer what was actually meant, but could someone more informed fix it up? Soo 17:23, 12 July 2006 (UTC)
The section on the Sun's magnetic field mentions that "All matter in the Sun is in the form of gas and plasma due to its high temperatures." I though that the material in the Sun was 100% ionized, so the amount of gas is trivial? -- Iantresman 19:50, 12 July 2006 (UTC)
Property | Plasma | Gas |
State | 99.99% | Trace |
Fusion | Yes | No |
EM emmission | Yes | No |
Magnetic field | Yes | No |
Magnetic reconnection | Yes | No |
MHD | Yes | No |
X-rays | Yes | No |
Electric currents | Yes | No |
Convection | Yes | Yes |
Some corrections:
As seems to happen frequently between us, Ian, I'm not quite sure what you're driving at. If you want the wording "...plasma (an ionized gas)" rather than "...gas and plasma", I don't see that as a problem. zowie 15:13, 13 July 2006 (UTC)
In the core of the sun it is so hot and such an high pressure, that it occours plasma. And what plasma really is, is free electrons and hydrogen (or helium)ions. Because of the heat and pressure has the hydrogen (or helium) molecules split up. That happens when the thermic energy conquers the connecting powers of two different electric loaded particles. But teoreticly seen I think one could call it hydrogen and helium plasma, even if it isn't physically right. 11.04, 4 August, 2006, by Lady Stardust
Please let me know if this has already been addressed, but the sun is central to a great deal of human culture, religion, etc. This article seems exclusively science-based and fails to address the importance that people attribute to the sun for cultural or other reasons. Is this addressed anywhere on Wikipedia? FunnyYetTasty 14:44, 13 July 2006 (UTC)
See also earlier Talk:Sun/Archive 01#Missing culture. For the religious aspects there already is the solar deity article (which could use some more prominent linking here however). For the fiction and other culture I think a separate sun in art and literature should be started. Femto 20:28, 13 July 2006 (UTC)
Why the second person? Who is "our"? So much for neutrality! savidan (talk) (e@) 17:22, 17 July 2006 (UTC)
Why are people cutting vast chunks out of this article [3]? What good does it do to remove that information from this article? I'm sure you could reproduce it elsewhere without removing it from a featured article. 62.249.214.195 14:25, 27 July 2006 (UTC)
Could anyone put more on history of human scientific understanding of the sun? Like history of attempts at measuring its distance from the earth.
I'm not sure if this is the most relevant place to post this (and please feel free to move it if it isn't), but in the section, "Development of Modern Scientific Understanding", the last paragraph states: "Finally, in 1957, a paper titled Synthesis of the Elements in Stars[28] was published that demonstrated convincingly that most of the elements in the universe had been created by nuclear reactions inside stars like the Sun."
Now I'm certainly no astronomer, but, by mass, doesn't Hydrogen (by far) comprise "most" of the elements in the universe? Further, virtually by definition, Hydrogen isn't created "by nuclear reactions inside stars". As such, should there be some distinction made in the article to show that in this reference "most" doesn't mean by mass but rather (I assume) by % of elements on the periodic table? 216.240.7.149 00:58, 29 October 2006 (UTC)
The accuracy with which we know the mass of the sun is limited by the accuracy with which we know the gravitational constant - we know GM_sun to about eight decimal places from observing the planets. Perhaps this is worth mentioning, and giving this number? (Or the mass of the sun in geometrized units) -- Andrew 20:31, 30 July 2006 (UTC)
Anyone mind if I remove the image with this caption: "Artist's conception of the remains of artificial structures on the Earth after the Sun enters its red giant phase and swells to roughly 100 times its current size."? Tony 07:38, 3 August 2006 (UTC)
How many people use Kelvin in every day usage? The temeperature should include Farenheit and Celsius. Dudtz 8/3/06 8:19 PM EST
Just subtract 273 from a kelvin and you get Celsius, it's pretty simple and Kelvin is the norm with planets -- Dulberf 04:44, 4 August 2006 (UTC)
That still does not help people who don't use Kelvin and Celsius. Dudtz 8/5/06 5:32 PM EST
Why not have the temperature in Farenheit? Dudtz 9/12/06 8:05 PM EST
By the way, guys and gals, its kelvins, lower case. Read the article. Urhixidur 03:16, 18 September 2006 (UTC)
Worldtraveller- Your personal attacks are really not cool. A British orthographic imperialist made a guideline-violating change here [4]. I corrected it, and fixed a few other things to make the article have a uniform spelling style. That's what the guidelines call for. I'm not pushing U.S. spelling. I'm pushing wikipedia guidelines. Other people are pushing U.K. spellings. But that seems not to bother you. If you want the British Empire to take over the world again, or enjoy attacking people for trying to improve wikipedia articles, please go elsewhere. -- Justice for All 02:16, 14 August 2006 (UTC)
"The Sun is the star at the center of Earth's solar system, but that's not important right now."
This is a weird way to open the article, don't you think?
I updated the mass of the sun and the equivalent number of Earths according to Measurement of Newton’s Constant Using a Torsion Balance with Angular Acceleration Feedback (Physical Review Letters; Vol. 85, Num. 14; 2 Oct. 2000) by Jens H. Gundlach and Stephen M. Merkowitz of the Department of Physics, Nuclear Physics Laboratory, University of Washington, Seattle, Washington 98195. They produced the most precise measurement of “Big G” yet with a value of 6.674 215(92) × 10–11 m3 kg–1 s–2. This allowed them to calculate the mass of the sun (1.988 435(27) × 1030 kg) and the mass of the Earth (5.972 245(82) × 1024 kg), and the equivalent number of Earths (332,946). Greg L 01:27, 24 August 2006 (UTC)
My physicist uncle suggested there may be a black hole at the center of the sun. Personnally I find this a plausible argument since the definition of black hole is something so massive that light cannot escape it. —The preceding unsigned comment was added by 164.107.166.152 ( talk • contribs) .
The density/gravity at the suns core is not high enough for a black hole -- Nbound 04:56, 2 September 2006 (UTC)
How can massless light not escape a black hole? Dudtz 9/12/06 8:11 PM EST
Has any man-made object ever made contact with the sun? I know it would never make it there, it would just burn up, but I am curious. -- Cngodles 15:54, 8 September 2006 (UTC)
The infobox was just changed to read ! align="left" | Surface temperature | 5785 K
This implies a precision of measurment to the degree. 5780 would imply +/- 5 degrees or so. I rather doubt we have measurements to the degree. Do we know a tolerance for this? RJFJR 17:42, 12 September 2006 (UTC)
The article states the solar luminosity is 3.9E28 lm (39,000 Ylm), which translates to about 3,100 Y cd (since the Sun radiates into 4π sr). This source states the solar illumination at Earth's equator at high noon is about 1000 lx. Using a 1 m² surface, we can compute it subtends a solid angle of about 1.787E-22 sr (using 1 AU distance), so the Sun's equivalent point luminosity is 5.6E24 cd (5.6 Ycd). The discrepancy is a factor of 554!
Which is right?
Urhixidur 02:28, 18 September 2006 (UTC)
This source states a V-magnitude zero star outside Earth's atmosphere puts out 2.54E-6 lx. The atmosphere transmits 82% in the visual, i.e. it dims 0.2 magnitudes. Since the Sun's V magnitude is -26.8, we're talking a 27.0 magnitude difference, hence the Sun is about 160 klx at ground level. This yields in turn a luminosity of about 900 Ycd. The discrepancy shrinks to a factor of 3.5.
The same source also gives a Mv=0 star outside Earth's atmosphere as = 2.45E29 cd. Since the Sun's Mv = 4.8, (5.0 on the ground), we have Sun = 2,450 Ycd.
Urhixidur 02:42, 18 September 2006 (UTC)
Yet another stab at it: the solar surface luminosity is given by this source as 2E9 nits (cd/m²); multiplying by the apparent disc (πr², not a bad approximation since there is little limb darkening), we get 3044 Ycd. Times 82% atmospheric transparency, about 2500 Ycd.
Clearly the very first source is wrong.
Urhixidur 03:02, 18 September 2006 (UTC)
Further update: various Sun luminances are bandied about:
The Sun's photospheric surface area being almost exactly 6×1018 m², the values above yield luminous intensities ranging between 5500 and 18 000 Ycd. I prefer to trust http://astro.kent.ac.uk/mds/507/ph507lecnote06-week1.doc, inasmuch as it takes into account the V filter's response curve. One can always argue the V filter is less sensitive than the human eye by a factor of between 1.8 and 6 times, in order to reconcile the figure with the luminances quoted above. The V luminance of the Sun is 0.484 Gcd/m², for comparison purposes.
Urhixidur 15:54, 18 September 2006 (UTC)
Zowie is quite right; I tend to share his "physicist's snobism" about the utter irrelevance of the human observer. But Wikipedia nevertheless has a responsibility to answer a child's question of « How bright is the Sun? ».
Searching the NASA ADS for a reliable value of the solar luminance or luminous intensity, I found M. Menat (1980), Atmospheric phenomena before and during sunset, Applied Optics, Vol. 19, (Oct. 15, 1980), pp. 3458-3468, which gives in figure 8 the apparent solar luminance during sunset/sunrise. The text states « the maximal average luminance of the Sun is about 1.5×109 cd/m² », which matches the mid-range value quoted earlier of 1.6 Gcd/m². Figure 9 is instructive, showing the zenithal spectral luminance peaking at 550 nm, which happens to be the monochromatic candela definition.
Menat, for the visibility function (equation 45), refers us back to:
Urhixidur 17:12, 18 September 2006 (UTC)
Going back to http://astro.kent.ac.uk/mds/507/ph507lecnote06-week1.doc, it turns out the « One star, Mv=0 outside Earth's atmosphere = 2.45×1029 cd » line is wrong by a factor of ten, and should read 2.45×1030 cd. This can be verified by looking a the other values quoted « 1 mv=0 star outside Earth's atmosphere = 2.54E-6 lux » and « 1 mv=0 star per sq degree outside Earth's atmosphere = 0.84E-2 cd/m² » and their conversions (into stilbs and phots). These are all cross-consistent. Plus, using the 2.54 µlx figure and scaling it to the Sun's apparent magnitude of -26.8, we do get 133 klx outside the atmosphere (109 klx inside), which matches the widely quoted maximum sunshine of 100 klx. Turning to luminance, we see the Sun puts out 3.75E+28 lm (which also matches the 100 lm/W value), corresponding to 6.16 Glm/m².
Turning to Menat's figure of 1.5 Gcd/m², it seems too weak by a factor of about 1/2. The Sun is a near-perfect Lambertian radiator, and therefore the illumination predicted by Menat's figure is 1.5 Gcd/m² × 1 Em² (a Lambertian sphere's flux is 2/3 πr² -see [8]) × 44.68 ysr (a square metre at 1 AU) ÷ 1 m² = 68 klx (×82% for the atmosphere = 55.8 klx). There's probably an error on my part here, can anyone spot it?
Urhixidur 19:45, 29 September 2006 (UTC)
Is there any particular order that is generally used for external links? If so, where can we find the guidelines? Rylan42 01:59, 24 September 2006 (UTC)
I've added some bits on the dangers of observing the Sun. I have laid it on a bit thick, but I think that is appropriate in this case. Man with two legs 10:41, 25 September 2006 (UTC)
For anyone watching here, I just redirected "The Sun" (i.e., with the definite article) to this page but expect to get reverted again. I'm surprised every day on the Wiki, but this was absolutely astounding. Any comments on that redirect talk page welcome. Marskell 23:22, 28 September 2006 (UTC)
I got rid of the "artist's conception" image because (A) it doesn't really focus on the Sun, (B) it is misleading. There is no reason to suppose that artificial structures will survive the intense heating from the red giant phase of the Sun's "life". Without some back-of-the-envelope justification, at least, for the presence of cracked mud and non-burned telegraph poles, the picture is misleading and worse than useless in this context. (Don't get me wrong, I think it's kind of cool -- just not appropriate here). Please discuss here before adding it back in. zowie 07:08, 14 October 2006 (UTC)
??? Zabrak 02:38, 28 October 2006 (UTC)
Copied from User talk:Howcheng:
The Dutch Wikipedia-page includes a table on solar evolution. I don't know how reliable it is scientifically, but it has some sources listed: http://nl.wikipedia.org/wiki/Zon Iblardi 19:24, 29 October 2006 (UTC)