TO "the Sun will become sufficiently large to engulf "

Birthgiverofthesun (
talk) 21:26, 27 August 2017 (UTC)

41.109.142.126 (
talk) 11:28, 13 September 2018 (UTC)

Suggested infobox images
Sun Sun as seen in visible light. Sun as seen in ultraviolet light (wavelength of 30.4 nm). Observation data Mean distance from Earth [etc]

VQuakr ( talk) 20:21, 4 February 2019 (UTC)

@ VQuakr:, @ Aldebarium:

• But still, shouldn't we answer a reader's question 'if I were to go into space, and look (indirectly) in the direction of the sun with my naked eyes, what would I see?'? Canopus, Alpha Centauri and Alcyone (star) have a visible light photo as their infobox image.
• The misconception is widely held enough that if one google for an image of the word 'sun,' about half of the images that show up are the UV photographs, and that NASA uses the UV photo as the top photo for this page. Other pages include this. Wikipedia, being an encyclopedia, ought to correct this misconception and not create any new one.
• If we use two images, is it better to stack them or put them side-by-side?

VarunSoon ( talk) 00:23, 5 February 2019 (UTC)

The visible light image that was in the infobox originally is pretty much what you would actually see, if you could view the Sun safely. For example if you use eclipse glasses to look at the Sun safely, or a telescope with a solar filter, that's what you will see: the Solar photosphere, sometimes with sunspots. The image you chose of the Sun as seen from space shows a bright glare because the Sun itself is completely saturated in the image, and there's a lot of scattered light and lens flare from the camera optics, which make it impossible to see the Sun's actual shape in that picture: instead all you see is the glare and scattered light from the camera optics, surrounding a totally saturated bright core. The misconception (if there is one at all) is a misconception that the Sun's appearance in visible light has rays and lens flare coming out of it. That stuff is not part of the Sun, that's just what the camera optics are doing. Aldebarium ( talk) 00:42, 5 February 2019 (UTC)

The version with the status quo image, [1], shows a white sun. It is accurate to what you would see either from space or from earth looking at the sun in the visible spectrum. An image of lens flare is not a better choice for the lead image per MOS:IMAGERELEVANCE. If we want two images, I think they looked better stacked vertically. VQuakr ( talk) 04:27, 5 February 2019 (UTC)

I want two images per your suggestion (the filtered one and the UV one placed below it). I want the misconception perpetuated by the UV photos to be dispelled. I want people to be able to visit this article and come out realizing that the the depiction of stars in the films Guardian of the Galaxy and Passengers was as inaccurate as the asteroid field in The Empire Strikes Back. I think the UV photos are used over the filtered visible light photos by NASA because of aesthetic reason. VarunSoon ( talk) 05:11, 5 February 2019 (UTC)

@ Aldebarium: Do we have a consensus here (at least among us three) about the infobox image(s)? My current position is for the status quo filtered one on top and the UV one below it (for the purpose of correcting the widely held misconception about what stars look like). VarunSoon ( talk) 05:30, 6 February 2019 (UTC)

That seems reasonable to me. It will definitely be good to include the UV image in the article. I don't have a strong opinion as to whether it should be in the infobox or somewhere else in the article, but I do agree that it will be useful and informative to include it somewhere. Aldebarium ( talk) 05:44, 7 February 2019 (UTC)

The article appears to say that the proportion of helium in the sun has fallen despite the fusion of hydrogen into helium in the sun.

From the Composition section of the Sun page:

"The Sun is composed primarily of the chemical elements hydrogen and helium. At this time in the Sun's life, they account for 74.9% and 23.8% of the mass of the Sun in the photosphere, respectively. ... Originally it would have contained about 71.1% hydrogen, 27.4% helium, and 1.5% heavier elements ... Since the Sun formed, the main fusion process has involved fusing hydrogen into helium."

Careful reading and a comment on the Talk page suggest that the second number refers to the total mass of the sun, and the first to the composition of the photosphere, however this is not immediately obvious. Ideally, comparable figures would be added that both refer to either the total mass, or the photosphere. That would give readers an idea of the changes over time. If these numbers aren't available then the text could be reworded to highlight the change of context.

Slewins ( talk) 11:12, 8 February 2019 (UTC)

Some helium has settled to the center over the Sun's lifetime. This accounts for the decreasing abundance in the photosphere. Ruslik_ Zero 13:33, 28 March 2019 (UTC)

In the "Name and etymology" section:

 "A mean Earth solar day is approximately 24 hours, whereas a mean Martian 'sol' is 24 hours, 39 minutes, and 35.244 seconds.[26]"

- really? We know the precise length of a Martian 'sol' but not that of the Earth's 'solar day'? Aside from the variance in literal terms ('sol' vs 'solar day'), why is one value so precise and the other so vague? --> 10 points for Entertainment Value. 99.4.120.135 ( talk) 17:44, 24 April 2019 (UTC)

I deleted the offending sentence, which is (after all) not relevant to the Sun itself, or to its etymology. The prior sentence about planetary astronomers using "sol" for a planetary day serves the same purpose. zowie ( talk) 18:35, 24 April 2019 (UTC)

Thank you. 99.4.120.135 ( talk) 20:05, 25 April 2019 (UTC)

A boomerang-like (or other shape) man-made meteorite built of a material which will melt relatively slowly (as it enters the sun) (... due to magnetic repulsion "?") will stir fresher gas to expand sun's lifespan. (of course that's impossible, or insanely expensive) — Preceding unsigned comment added by 2A02:587:4108:9200:201A:AE39:BE0D:2B3B ( talk) 20:16, 29 April 2019 (UTC)

the sun has circled the galaxy 19.9 times — Preceding unsigned comment added by Wikimaster5678 ( talk • contribs) 01:37, 3 May 2019 (UTC)

To be a little pedantic, the Sun does not strictly 'circle the galaxy', it follows an elliptical orbit within the galaxy around the galactic centre (or a point which itself orbits the centre), perturbed by local variations in mass density - this is discussed in the Orbit in Milky Way section, which also says "It takes the Solar System about 225–250 million years to complete one orbit through the Milky Way (a galactic year), so it is thought to have completed 20–25 orbits during the lifetime of the Sun." Was there something about that which you think needs changing, for which you have a reliable source? -- Begoon 06:28, 3 May 2019 (UTC)

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The sun surface temperature is not 5,778 but 5,772. ( NASA Official Number ) 94.241.227.0 ( talk) 21:00, 16 April 2019 (UTC)

 Not done. A few degrees at that scale is meaningless. – Deacon Vorbis ( carbon •  videos) 21:35, 16 April 2019 (UTC)

 Done — Ruyter ( talk • edits) 08:42, 4 May 2019 (UTC)

Can I add the {{ Starbox begin}}? Because the custom {{ Infobox}} is harder to edit than other infoboxes.

—Yours sincerely, Soumyabrata 16:35, 8 July 2019 (UTC)

How did our Sun catch fire in the first place? Can someone help me out here with an answer to this? Where did the initial ignition come from?

5.150.92.82 ( talk) 09:32, 2 August 2019 (UTC)

It didn't "catch fire": see the section Sun#Formation. Vsmith ( talk) 12:01, 2 August 2019 (UTC)

The section you refer to doesn't say how it started burning. 5.150.92.82 ( talk) 09:27, 5 August 2019 (UTC)

The section begins to explain and then links to Stellar nucleosynthesis, which goes into more depth. Solar core seems another good article for the topic. A good question though, and it should be explained in better terms. Randy Kryn ( talk) 09:35, 5 August 2019 (UTC)

Should the article make reference to the adopted nominal surface effective temperature of 5772  K? It isn't a physical property as such, just a number to be used when quoting or calculating the properties of other objects in units of solar temperature, but it is intended to closely match the actual mean effective temperature. Lithopsian ( talk) 14:00, 18 August 2019 (UTC)

Yes, that seems like the right thing to do. The infobox lists 5778 K with a reference to the NASA Sun fact sheet web page but that fact sheet currently lists 5772 K as the value of effective temperature, so it would be best to update the article to be consistent with the best current data. Aldebarium ( talk) 16:50, 29 August 2019 (UTC)

Nashhinton has correctly found a website that uses the Latin name for the Sun (after I challenged the addition). I still think that the word Sol is not a common name for the Sun in English except in Science Fiction. The OED entry says that Sol is used for the Sun personified. What does anyone else think? Dbfirs 16:14, 25 September 2019 (UTC)

Sol is commonly used by astronomers. Source: am an astronomer. Zowie ( talk) 17:49, 25 September 2019 (UTC)

From my experience, the Sun is by far the most common name, but Sol is used when in reference to other stars. It is not restricted to Science Fiction, but when thinking in terms of WP:COMMONNAME, the Sun is by far the most common. Jeb³ _{Talk at me here} 17:52, 25 September 2019 (UTC)

WP:COMMONNAME is part of a guideline on article titles and it not relevant here. VQuakr ( talk) 17:04, 26 November 2019 (UTC)

If it's commonly used by astronomers, we should be able to cite astronomical publications using it. As it stands, there are no such citations so I have removed it from the introduction. Brattice ( talk) 13:29, 26 November 2019 (UTC)

Should be included as an alternate name for the subject as discussed at WP:OTHERNAMES. No source needed per WP:BLUE. It could also be footnoted if there was consensus for at per MOS:ALTNAME. VQuakr ( talk) 17:04, 26 November 2019 (UTC)

"The Sun will spend a total of approximately 10 billion years as a main-sequence star". In the next section it says "it will exit the main sequence in approximately 5 billion years". — Preceding unsigned comment added by 47.72.13.67 ( talk) 22:36, 7 December 2019 (UTC)

Both are correct. The Sun will spend about 10 billion years as a main-sequence star, but about 4.6 billion of those years have already passed. Double sharp ( talk) 16:00, 8 December 2019 (UTC)

“Other stars with the same value of {\displaystyle X+V/(2B)} have take* [taken] the same amount of time to go around the galaxy as the sun and thus remain in the same general vicinity as the Sun.” Davidleci ( talk) 23:37, 14 January 2020 (UTC)

 Done Thanks. Changed it to "have to take". byteflush _Talk 20:11, 15 January 2020 (UTC)

The fusion reaction of hydrogen to helium is propagated by Gamma radiation. This means that the reaction front propagates at the speed of light. Therefore all of the available hydrogen will be converted to Helium in an uncontrolled catastrophic event as soon as the reaction is started. Clearly this cannot involve the whole of the solar core, but can only be a tiny part of it. Calculations indicate that if the reaction occurs every eleven, or so Earth years, then the available hydrogen, under reactive conditions, would occupy a volume of about 60km radius. Thus the reaction would be completed in about 200 microseconds. The reaction would totally destroy the 'reactor', and it would then require some time for the 'reactor' to be re-assembled under gravity. Eleven years seems to be a reasonable time for this to happen. Averaged out over eleven years, the amount of hydrogen converted to helium will be in good agreement with what has already been presented here, but since the reaction time, compared to the repetition period is so tiny, like 6.3 x 10^(-12), it is not surprising that the reaction neutrinos have never been detected.Dave at 168 12:28, 24 February 2020 (UTC) — Preceding unsigned comment added by Daveat168 ( talk • contribs)

First para/sentence of this section:

Various authors have considered the existence of a gradient in the isotopic compositions of solar and planetary noble gases,[65] e.g. correlations between isotopic compositions of neon and xenon in the Sun and on the planets.[66]

So they've considered something about noble gasses; but what correlations are there between what compositions? This both mock-acadamicese ('have considered') and free of any information about what was being considered.

Para 2 then tells us that some unexplained process (fractionation) in the Sun accounts for this. Good, now we know: something unexplained accounts for something unexplained. I am enriched! ghytred talk 12:35, 18 July 2020 (UTC)

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In Section 5.1 Core:

Please change "about the same rate of power production as takes place"

to "about the same rate of energy production as takes place"

Thanks 108.32.48.151 ( talk) 05:50, 19 August 2020 (UTC)

Replaced with "power density". Ruslik_ Zero 07:04, 19 August 2020 (UTC)

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The peak of the spectrum of the sun is dependent on the independent variable that is being plotted; it is different between wavelength and frequency. With respect to wavelength, it peaks in the green, but with respect to frequency it peaks in the infrared. This is not of physical consquence but is a mathematical property. Please remove or correct the text. See: https://wtamu.edu/~cbaird/sq/2013/07/03/what-is-the-color-of-the-sun/ for an illustration, and https://arxiv.org/pdf/1109.3822.pdf and http://www.phys.ufl.edu/~hagen/phz4710/readings/AJPSofferLynch.pdf for more technical explanations.

Suggested removing "When measuring all the photons emitted, the Sun is emitting more photons in the green portion of the spectrum than any other." or replacing with "The association of the peak of the spectrum of the Sun with the colour of the Sun is misleading, and the peak of the spectrum depends on measurement with respect to wavelength or frequency."

with appropriate citations above. 2001:8003:C995:6200:B0D3:A97F:F72C:9727 ( talk) 04:40, 5 September 2020 (UTC)

I corrected that statement. Ruslik_ Zero 14:58, 5 September 2020 (UTC)

The mission was scheduled in the mid of 2020 , but due to the pandemic it has been pushed to January 2022. Hiremath Prajwal ( talk) 14:29, 10 September 2020 (UTC)

"Its diameter is about 1.39 million kilometers (864,000 miles)..." should be changed.

The number in parentheses should be 864 million miles.

˜˜˜˜ John Longville

I disagree. The conversion in the article seems to be correct. As 1 mile = 1.609 km, the Sun's diameter converts as 1.39e6 / 1.609 = 863890 (~864,000). Stardust canopy ( talk) 10:54, 27 September 2020 (UTC)

The article states that 100 times the mass of Earth has been converted into energy over the lifetime of the sun, which is 0.03% of the sun's total mass. That math is correct, but the 100 times the mass of Earth is wrong. The result should be ~4%.

The energy released from the pp-chain is 26.72MeV, so the energy release per hydrogen atom is ~6.7MeV. The solar luminosity is ~2.4e39 MeV/s. So roughly 3.6e38 hydrogen atoms are burned every second. Each hydrogen atom is ~1.7e-24g, so roughly 6e14 grams are burned every second. The sun is ~1.4e17 seconds old. So roughly 8.4e31 grams of mass have been converted into energy (14,000 earth masses). This is ~0.042 of the solar mass, so ~4%.

If you prefer random internet sources, see: https://cosmicopia.gsfc.nasa.gov/qa_sun.html#consume. — Preceding unsigned comment added by 132.235.76.238 ( talk) 14:03, 29 September 2020 (UTC)

That source misstates the mass of the Earth as 1.35E24 kg, the correct value is 5.97E24 kg. More importantly, loss of hydrogen is not the same as mass loss. The process produces helium. Paradoctor ( talk) 16:42, 29 September 2020 (UTC)

Your back-of-the-envelope calculations are unclear. In particular "4%" is not an answer to anything? 4% of what? The sun has certainly not lost 4% of its mass to radiation. A handy rule of thumb is that approximately the mass of Saturn has been radiated away by the sun since it was formed, that's nearly 100 times the mass of the Earth and roughly 0.03% of the Sun's current mass. I suspect the step you've missed (see WP:OR) is that of your 600 million tons of hydrogen "burned" every second, less than 1% is actually converted to energy. Total mass converted to energy per second is around 5 million tons, not 600 million as you state. Divide everything from there on by a little over 100 and you are there. It helps to lay out your working much more clearly, then you'd probably have seen that yourself. Lithopsian ( talk) 17:29, 29 September 2020 (UTC)

/info/en/?search=Sun#Photons_and_neutrinos

Wouldn't there also be some Compton scattering of photons as they make their way from the core to the surface? And I assume the absorption is done by nuclei. Betaneptune ( talk) 09:57, 22 November 2020 (UTC)

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"which is about the same power density as in body of a reptile or inside a compost pile." this just needs to be removed/reworded, etc. The source doesn't seem to say anything about a reptile at all and the grammar also seems off in that sentence.-- 222.109.164.154 ( talk) 01:09, 26 December 2020 (UTC)

 Done Removed the reptile part. – robertsky ( talk) 05:55, 3 January 2021 (UTC)

"Viewed from a vantage point above its north pole, the Sun rotates counterclockwise around its axis of spin.[d][43]"

This is not very illuminating. If the north/south poles are defined in terms of rotation (as I believe they are on Venus), then this is a tautology. I think it would be more telling to say which way the Sun rotates from the vantage point of e.g. Earth's north pole. 93.136.8.9 ( talk) 06:19, 29 November 2020 (UTC)

Prograde. Sagittarian Milky Way ( talk) 06:32, 29 November 2020 (UTC)

What is prograde in this context? Clockwise or counterclockwise? 93.136.8.9 ( talk) 07:46, 29 November 2020 (UTC)

Normal, unlike Venus and Uranus the freak planets (which still orbit prograde like the others) Sagittarian Milky Way ( talk) 08:11, 29 November 2020 (UTC)

That still tells the reader nothing if he doesn't know what "prograde" and "normal" means. Is that clockwise or counterclockwise from Earth's north pole (or south pole if you're so inclined). You could also add to the article something like "The Sun's north pole is pointed roughly in the [ same / opposite ] direction as the Earth's north pole", that would also clear this up. 93.136.168.152 ( talk) 01:11, 30 November 2020 (UTC)

The infobox says Declination

of North pole +63.87° 63° 52' North which is the direction of Earth's 63.87th parallel of Northern latitude, the place on Earth where up is parallel to up at the Sun's North Pole is always on this latitude but Earth spins so it circumnavigates the latitude. Sagittarian Milky Way ( talk) 09:08, 2 December 2020 (UTC)

So, viewed from the Earth's north pole, the Sun rotates counterclockwise, if I got it right? That's surely worth including in the article. 93.136.110.156 ( talk) 10:28, 4 December 2020 (UTC)

Yes. If you'd look down upon the solar system from a faraway vantage point far in the north, most things would be spinning and orbiting counter-clockwise. Venus and Uranus (and most of its moons) are weirdos. Also notable is Triton, Neptune's largest moon, which orbits the wrong way around and, similar to our moon, always faces its planet the same way. I agree that the way it's currently phrased in the article is unhelpful, since at least some definitions of what ‘north pole’ means would render it a tautology, although the footnote helps. — Preceding unsigned comment added by 77.61.180.106 ( talk) 15:08, 24 December 2020 (UTC)

Venus from being hit by an object that stopped its rotation and slightly reversed it and Uranus from being hit by an object that knocked it on its side and slightly more. Both billions of years ago. Sagittarian Milky Way ( talk) 06:13, 3 January 2021 (UTC)

From the article:

The Sun's color is white, with a CIE color-space index near (0.3, 0.3), when viewed from space or when the Sun is high in the sky, and the Solar radiance per wavelength peaks in the green portion of the spectrum.

I checked both references given and neither of them corroborates this statement. I also think that the references given aren't good references for this kind of thing, they're both pop-science-y articles apparently aimed at little kids. It should be possible to find a textbook reference with perhaps a few, hopefully recent, scientific articles to back it up.

Incidentally, I also think it's more vague than it needs to be. ‘Near (0.3, 0.3)’? How near? The notation implies that the colour could be off by .05 in both the x and y direction. Well, at x=.25 the colour is distinctly cyan, at x=.35 the colour is pink, at y=.25 it's light purple and at y=.35 pale green. By the way, if the colour is (.3, .3) exactly, I think most people would consider that just a bit on the purple side.

Of course the Land effect implies that no matter the (x, y) it will eventually be perceived as white if you're out there on your spacewalk for long enough, so I think the whole question of whether the sun is or isn't white is in some sense meaningless.

Another question the article doesn't answer: is the colour constant across the disk? — Preceding unsigned comment added by 77.61.180.106 ( talk) 12:26, 24 December 2020 (UTC)

Another question: how dominant is the blackbody component of the sun's radiation? At 5772 K the colour should be about (.3287, .3397) and according to an online conversion tool that would look like this:

 ● 

Cheers. — Preceding unsigned comment added by 77.61.180.106 ( talk) 14:01, 24 December 2020 (UTC)

Is not constant, the photosphere is a milliradius shell, not a surface, at the center you have the most direct path to the bottom and the color is more like that of the photosphere bottom gas than any other part of the disk. Still has some contribution from the photosphere top gas of course. Sagittarian Milky Way ( talk) 06:08, 3 January 2021 (UTC)

I thought that might be the case. I wonder if it's possible to dig up some papers on the subject. — Preceding unsigned comment added by 77.61.180.106 ( talk) 02:25, 5 January 2021 (UTC)

This phenomenon is called limb darkening. Sagittarian Milky Way ( talk) 03:31, 5 January 2021 (UTC)

From the tachocline subsection:

Presently, it is hypothesized (see Solar dynamo) that a magnetic dynamo within this layer generates the Sun’s magnetic field.

And from the magnetic field subsection:

At solar-cycle maximum, the external poloidal dipolar magnetic field is near its dynamo-cycle minimum strength, but an internal toroidal quadrupolar field, generated through differential rotation within the tachocline, is near its maximum strength.

Recently, however, radio observations of fully convective stars have shown that they possess a solar cycle despite lacking a tachocline. Their activity levels fit the same dependence on rotation rate as partly convective stars like our Sun as well. The most likely explanation for this is that either the dynamos of fully convective stars operate the same as those found in partly convective stars (which would mean that tachoclines aren't essential for solar dynamos) or that fully convective stars generate a purely turbulent dynamo that exhibits a rotation-activity relationship very similar to that in partly convective stars. ^{[1] [2] [3]}

The tachocline and solar dynamo articles already make reference to this, so perhaps it would be unnecessary to add it here. I think it should be considered nonetheless.

CoronalMassAffection ( talk) 09:29, 20 February 2021 (UTC)

From the article:

The Sun's color is white, with a CIE color-space index near (0.3, 0.3), when viewed from space or when the Sun is high in the sky, and the Solar radiance per wavelength peaks in the green portion of the spectrum.

I checked both references given and neither of them corroborates this statement. I also think that the references given aren't good references for this kind of thing, they're both pop-science-y articles apparently aimed at little kids. It should be possible to find a textbook reference with perhaps a few, hopefully recent, scientific articles to back it up.

Incidentally, I also think it's more vague than it needs to be. ‘Near (0.3, 0.3)’? How near? The notation implies that the colour could be off by .05 in both the x and y direction. Well, at x=.25 the colour is distinctly cyan, at x=.35 the colour is pink, at y=.25 it's light purple and at y=.35 pale green. By the way, if the colour is (.3, .3) exactly, I think most people would consider that just a bit on the purple side.

Of course the Land effect implies that no matter the (x, y) it will eventually be perceived as white if you're out there on your spacewalk for long enough, so I think the whole question of whether the sun is or isn't white is in some sense meaningless.

Another question the article doesn't answer: is the colour constant across the disk? — Preceding unsigned comment added by 77.61.180.106 ( talk) 12:26, 24 December 2020 (UTC)

Another question: how dominant is the blackbody component of the sun's radiation? At 5772 K the colour should be about (.3287, .3397) and according to an online conversion tool that would look like this:

 ● 

Cheers. — Preceding unsigned comment added by 77.61.180.106 ( talk) 14:01, 24 December 2020 (UTC)

Is not constant, the photosphere is a milliradius shell, not a surface, at the center you have the most direct path to the bottom and the color is more like that of the photosphere bottom gas than any other part of the disk. Still has some contribution from the photosphere top gas of course. Sagittarian Milky Way ( talk) 06:08, 3 January 2021 (UTC)

I thought that might be the case. I wonder if it's possible to dig up some papers on the subject. — Preceding unsigned comment added by 77.61.180.106 ( talk) 02:25, 5 January 2021 (UTC)

This phenomenon is called limb darkening. Sagittarian Milky Way ( talk) 03:31, 5 January 2021 (UTC)

From the tachocline subsection:

Presently, it is hypothesized (see Solar dynamo) that a magnetic dynamo within this layer generates the Sun’s magnetic field.

And from the magnetic field subsection:

At solar-cycle maximum, the external poloidal dipolar magnetic field is near its dynamo-cycle minimum strength, but an internal toroidal quadrupolar field, generated through differential rotation within the tachocline, is near its maximum strength.

Recently, however, radio observations of fully convective stars have shown that they possess a solar cycle despite lacking a tachocline. Their activity levels fit the same dependence on rotation rate as partly convective stars like our Sun as well. The most likely explanation for this is that either the dynamos of fully convective stars operate the same as those found in partly convective stars (which would mean that tachoclines aren't essential for solar dynamos) or that fully convective stars generate a purely turbulent dynamo that exhibits a rotation-activity relationship very similar to that in partly convective stars. ^{[1] [2] [3]}

The tachocline and solar dynamo articles already make reference to this, so perhaps it would be unnecessary to add it here. I think it should be considered nonetheless.

CoronalMassAffection ( talk) 09:29, 20 February 2021 (UTC)

Not proven fact but grand guesses that you know are grand guesses but have written as if it's a proven fact

2601:189:C381:5A60:5186:9603:8E65:8781 ( talk) 17:05, 8 March 2021 (UTC)

Science is more reliable than you think. Also it doesn't use the word proof, it uses law or theory which does not mean what a layman means when he says "I have a theory", the science word for that would merely be scientific hypothesis at best (like a detective's lead) or nonsense at worst. Sagittarian Milky Way ( talk) 17:40, 8 March 2021 (UTC)

Does the sun move? contrary to the believe that the sun is stationary, the sun move at a very tremendous speed towards a black hole. Towards a great centrifugal force of unimaginable proportions. It drags all the members of the solar system with gravitational force as it speed away The direction it move is called "anickany" since it's none of the directions of the compass as we know them.

It's for this reason that the universe seem to be expanding 105.48.130.102 ( talk) 17:35, 16 March 2021 (UTC)

Got a citation for that? Also, anything specific you're asking us to change in this article? (i.e. please change X sentence to Y sentence) – Novem Linguae ( talk) 18:44, 16 March 2021 (UTC)

What is the temperature of the solar corona? This article doesn't seem to know. As of today, 03-26-2021, the summary statistics at the right top panel of the page claim it's about 5 million Kelvin, the section titled "Coronal heating problem" says it's between 1 and 2 million Kelvin. That's a non-trivial discrepancy. — Preceding unsigned comment added by Kaimiddleton ( talk • contribs) 18:20, 26 March 2021 (UTC)

The atmosphere section discusses that (with a reference); it varies from about 1 to 20 million K. Depends where in the corona you're talking about. —Alex ( Ashill | talk | contribs) 19:18, 26 March 2021 (UTC)

A question on the Science Reference Desk asked about an apparent error in this article, specifically in § After core hydrogen exhaustion:

According to a 2008 model, Earth's orbit is shrinking due to tidal forces (and, eventually, drag from the lower chromosphere), so that it will be engulfed by the Sun near the tip of the red giant branch phase, 3.8 and 1 million years after Mercury and Venus have respectively had the same fate.

Relevant edit history:

User:rolf h nelson / 18:45, 20 February 2016: Correctly (but perhaps confusingly) worded to indicate that the Earth orbit shrinkage is during the Sun's giant phase.

User:JorisvS / 20:54, 20 February 2016: A copy edit; reworded for clarity, but inadvertently states that the Earth's orbit is currently shrinking.

User:U-95 / 12:57, 18 December 2016: More information added, bringing the sentence to its current form.

I've repaired the sentence as follows:

According to a 2008 model, Earth's orbit will have initially expanded significantly due to the Sun's loss of mass as a red giant, but will later start shrinking due to tidal forces (and, eventually, drag from the lower chromosphere) so that it is engulfed by the Sun during the tip of the red-giant branch phase, 3.8 and 1 million years after Mercury and Venus have respectively suffered the same fate.

The relevant reference is: Schröder, K.-P.; Connon Smith, R. (2008). "Distant future of the Sun and Earth revisited". Monthly Notices of the Royal Astronomical Society. 386 (1): 155–163. arXiv.

Some questions for the subject matter experts here:

• Is this primary reference (name=schroder) overused in this article? It is currently cited six times.
• Is its 2008 conclusion regarding Earth's eventual fate now widely accepted, or does our sentence still need to be prefaced, "According to a 2008 model"?

-- ToE 12:11, 2 April 2021 (UTC)

Thanks for cleaning that up. You are absolutely right in fixing the tense error (and too bad it sat there for five years uncorrected). I don't think that ref is overused; from when I read it carefully (which was a decade ago), I recall it being quite good, and there's not a lot of literature on the future of the Solar System because it's basically untestable (though we understand quite well how the Sun will involve, since it's a typical star and we do have quite good observational constraints on stellar evolution models). Similarly, off the top of my head and a quick check of the citations of the Schroeder paper, I don't think there's enough literature on the topic to really say that that model is accepted or not accepted. Therefore, I think saying "according to a 2008 model" is good; it's still worth citing because it's good and interesting, but because it's only one study, that caveat seems appropriate. There might be some more recent understanding because we know so much more about planets around other stars now that we did in 2008; if I find something that expands on the 2008 paper, I'll add it. —Alex ( Ashill | talk | contribs) 02:07, 3 April 2021 (UTC)

Thanks! -- ToE 16:22, 3 April 2021 (UTC)

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The following sentence has a typo:

The Sun's cure fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result.

It should read:

The Sun's core fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result. 98.113.248.232 ( talk) 19:28, 5 April 2021 (UTC)

 Done Ruslik_ Zero 20:13, 5 April 2021 (UTC)

Is it just me, or is the following explanation potentially inaccurate, misleading, or at the very least in need of a citation?

The Sun is gradually becoming hotter during its time on the main sequence, because the helium atoms in the core occupy less volume than the hydrogen atoms that were fused. The core is therefore shrinking, allowing the outer layers of the Sun to move closer to the center and experience a stronger gravitational force, according to the inverse-square law. This stronger force increases the pressure on the core, which is resisted by a gradual increase in the rate at which fusion occurs.

While I'm a physicist, I'm not an astrophysicist, but I'm not sure this is the ideal explanation.

• It's probably better to say that the sun is becoming more luminous during its time on the main sequence. This increase in luminosity is primarily due to an increase in its radius than its effective blackbody temperature, as the figure shown illustrates. The core is definitely increasing in temperature, though, although the explanation isn't clear.
• As the sun is expanding during this time, the outer layers (e.g. photosphere and atmosphere) are moving further from the center, not closer.
• The inverse-square law does not hold inside the sun, because the mass enclosed by a sphere at the given distance decreases under the shell theorem. Indeed, a uniform sphere (true, this does not apply to the sun) will see a decrease in the gravitational force because the inverse-square law loses out to the cubic dependence of the enclosed mass. Therefore moving "closer to the center" to "experience a stronger gravitational force" is not an ideal explanation of gravitational contraction.
• I believe the pressure inside the core actually decreases, although it is fair to say that further decrease is resisted by the increasing temperature and fusion rate.

I know it is difficult to convey the changes in hydrostatic equilibrium as the sun ages, but I feel this would be better if focused on the change in mean molecular weight under the ideal gas law. As the fusion process turns 8 particles (4 protons, 4 electrons) into 3 (1 helium nucleus, 2 electrons), there will be a decrease in the number of particles and hence an increase in the mean molecular weight.

${\displaystyle P={\frac {\rho N_{\text{A}}k_{\text{B}}T}{\mu }}}$

An increase in μ means either a decrease in P or an in increase in density or temperature in the core. Ultimately all three occur in a more complex shift in the equilibrium, but it may be fair to explain it as a drop in pressure, leading to a core contraction and increase in density, rate of fusion and temperature. StuartH ( talk) 15:17, 4 April 2021 (UTC)

The explanation in the virial theorem article may be useful.

As stars on the main sequence convert hydrogen into helium in their cores, the mean molecular weight of the core increases and it must contract to maintain enough pressure to supports its own weight. This contraction decreases its potential energy and, the virial theorem states, increases its thermal energy. The core temperature increases even as energy is lost, effectively a negative specific heat.

The reference to gravitational potential here is preferable to gravitational force as it is now, and it is more clear how the accumulation of helium ultimately leads to a hotter core. StuartH ( talk) 03:06, 5 April 2021 (UTC)

What is the effect of fuel dilution and opacity change? Sagittarian Milky Way ( talk) 17:20, 5 April 2021 (UTC)

From memory as an undergrad, fuel dilution is compensated for by increased temperature and opacity is more of an issue in later phases but I'm going to embarrass myself in front of the astro experts if I speak as an authority on that. StuartH ( talk) 02:27, 6 April 2021 (UTC)

I edited the section per this suggestion, using a standard undergraduate astrophysics textbook as a reference (which in turn is mostly based on Bahcall et al 2001). Indeed, it is really the change in mean molecular weight and the resulting decrease in pressure (all else being equal) that leads to the increased luminosity. The increase in luminosity is about half due to the increase in surface area and half due to the increase in surface temperature (that factor of T^4 means even a small increase in temperature is enormous); I made explicit that it is really four different things that increase (core temperature, surface temperature, radius, and luminosity). (@ StuartH: your explanation is more or less verbatim what the textbook says; I actually wrote the revised sentences in the article referring to the textbook, not your comment, but the result is the same.) —Alex ( Ashill | talk | contribs) 21:14, 5 April 2021 (UTC)

Thanks! Your edit was more or less what I was getting at. I came to the page with the future of the sun in mind (where the surface temperature is more stable and eventually drops), so didn't consider Stefan-Boltzmann law but on reflection the surface temperature changes are noteworthy. StuartH ( talk) 02:13, 6 April 2021 (UTC)

Actually, while we're at it, I think the next section needs some reference to hydrogen shell-burning in the subgiant and RGB phases. At the moment, there's reference to the core being exhausted but it's unclear why the luminosity then increases and I can see readers scratching their head wondering about that. It may be as simple as appending something along the lines of "as fusion of hydrogen continues in a shell around the helium core" to "Once the core hydrogen is exhausted in 5.4 billion years, the Sun will expand into a subgiant phase and slowly double in size over about half a billion years". The included reference already mentions this transition to hydrogen shell-burning. StuartH ( talk) 02:23, 6 April 2021 (UTC)

Indeed. I just updated it to make the point that contraction in the core leads to increased luminosity which drives the RGB evolution. (Someone should definitely look over what I added; it might be too high-level.)

Note that I also removed the claim that the luminosity of the Sun will double and it will be as bright on Earth as it is on Venus today by the end of the main sequence phase. I didn't see that explicitly cited, and the refs I'm following say the final main sequence luminosity will be about 1.35 solar luminosities, not close to double the present-day luminosity (but close to double the zero-age main sequence luminosity, which may be where the mistake came from). —Alex ( Ashill | talk | contribs) 03:40, 6 April 2021 (UTC)

I see that factor of two increase in the Sun's luminosity from now until the end of the main sequence life comes from this paper by Ribas, whose Figure 1 is essentially reproduced in the article ( File:Solar evolution (English).svg). I'm not sure why the discrepancy between that evolution model and the Bahcall et al one, which is roughly contemporaneous with the underlying models cited in Ribas. I think for Wikipedia, a recent secondary or tertiary source (textbook) trumps a conference proceeding or the primary research literature, but someone (possibly future me) should check this. —Alex ( Ashill | talk | contribs) 04:04, 6 April 2021 (UTC)

The article says:

The Sun's color is white, with a [[CIE 1931 color space|CIE]] color-space index near (0.3, 0.3), when viewed from space or when the Sun is high in the sky, and the Solar radiance per wavelength peaks in the green portion of the spectrum.<sup><ref>{{cite news |url=http://www.universetoday.com/18689/color-of-the-sun/ |title=What Color is the Sun? |work=Universe Today|access-date=23 May 2016}}</ref><ref>{{cite web |url=http://solar-center.stanford.edu/SID/activities/GreenSun.html |title=What Color is the Sun? |publisher=[[Stanford University|Stanford]] Solar Center|access-date=23 May 2016}}</ref>

However, the chart at Sunlight § Spectral composition of sunlight at Earth's surface, if I read it correctly, indicates a peak in the yellow (570–590 nm) rather than green (495–570 nm) portion. Am I missing something? -- Florian Blaschke ( talk) 01:58, 15 April 2021 (UTC)

The green is in space, as explicitly stated in the reference (perhaps could be slightly clearer in this article). That Wikipedia article is at the Earth's surface, with the impact of the atmosphere (which always makes the Sun appear redder; how much redder depends on elevation). —Alex ( Ashill | talk | contribs) 06:18, 15 April 2021 (UTC)

Hello! This is to let editors know that the featured picture File:Sun poster.svg, which is used in this article, has been selected as the English Wikipedia's picture of the day (POTD) for May 5, 2021. A preview of the POTD is displayed below and can be edited at Template:POTD/2021-05-05. For the greater benefit of readers, any potential improvements or maintenance that could benefit the quality of this article should be done before its scheduled appearance on the Main Page. If you have any concerns, please place a message at Wikipedia talk:Picture of the day. Thank you! Cwmhiraeth ( talk) 09:48, 21 April 2021 (UTC)

The Sun.. is indeed infact a Stone.. A Diamond.. that harnesses and releases energy....... ~Mâťťhęw Ğøųłđêñ Gnostic~Høłý-Mąñ ( talk) 22:28, 3 May 2021 (UTC)

Please provide a citation from a reliable source so that others can verify this. With or without one however, I'm certain this isn't true given the Sun has been shown to be a sphere of plasma (see the composition section) and therefore cannot be a stone or a diamond. CoronalMassAffection ( talk) 20:44, 4 May 2021 (UTC)

Get it? - 2600:1700:DD4:B50:B10F:CE25:2439:F9E9 ( talk) 00:58, 5 May 2021 (UTC)