Talk:Sun

Unsafe conclusion in Motion and location

Under the subtitle "Motion in the Solar System"

There is an unsupported conclusion with an orphan reference. To wit: "[…] The orbits of the inner planets, including of the Earth, are similarly displaced by the same gravitational forces, so the movement of the Sun has little effect on the relative positions of the Earth and the Sun or on solar irradiance on the Earth as a function of time.[140] […]"

Checking footnote 140 reveals:

Retraction of: Scientific Reports 10.1038/s41598-019-45584-3, published online 24 June 2019 The Editors have retracted this Article. After publication, concerns were raised regarding the interpretation of how the Earth-Sun distance changes over time and that some of the assumptions on which analyses presented in the Article are based are incorrect.The analyses presented in the section entitled “Effects of SIM on a temperature in the terrestrial hemispheres” are based on the assumption that the orbits of the Earth and the Sun about the Solar System barycenter are uncorrelated, so that the Earth-Sun distance changes by an amount comparable to the Sun-barycenter distance. Post-publication peer review has shown that this assumption is inaccurate because the motions of the Earth and the Sun are primarily due to Jupiter and the other giant planets, which accelerate the Earth and the Sun in nearly the same direction, and thereby generate highly-correlated motions in the Earth and Sun. Current ephemeris calculations [1,2] show that the Earth-Sun distance varies over a timescale of a few centuries by substantially less than the amount reported in this article. As a result the Editors no longer have confidence in the conclusions presented. S. I. Zharkov agrees with the retraction. V. V. Zharkova, E. Popova, and S. J. Shepherd disagree with the retraction.

[1] Folkner, W. M., Williams, J. G., Boggs, D. H., Park, R.S. & Kuchynka, P. The Planetary and Lunar Ephemerides DE430 and DE431. "The Interplanetary Network Progress Report", Volume 42–196, February 15, 2014.

[2] JPL Horizons on-line solar system data. Horizons System

Reference: Retraction Note: Oscillations of the baseline of solar magnetic field and solar irradiance on a millennial timescale

What is the actual solar (effective) temperature?

The article gives several conflicting values:

1. 5772 K in the infobox
2. 5777 K in the second paragraph of the Sun#Photosphere section
3. 5778 K in the Sun#Sunlight_and_neutrinos section
4. 5772 K (again) in the Sun#Main_sequence section.

Now, of course, all these values are clearly well within any reasonable error margin of each other, but it's sloppy editing to give three different values. I suggest the above (and other numbers, ) be normalised to the nominal values from IAU 2015 Resolution B3 (i.e. Table 1 in Andrej Prša et al 2016 AJ 152 41, DOI: 10.3847/0004-6256/152/2/41; the pre-print of which is already cited as Ref no. 12). 69.165.195.198 (talk) 22:07, 24 July 2024 (UTC)

Excellent thanks. In one case I edit the value away in the process of cleaning up some refs. Johnjbarton (talk) 01:36, 25 July 2024 (UTC)

Hmm... Now that I have read the reference again I am not so sure. The "nominal values" in that publication serve a specific purpose:

• "These nominal values should be understood as conversion factors only—chosen to be close to the current commonly accepted estimates (see Table 1)—not as the true solar properties."

So for example, (as I understand this sentence), the temperature is really a value derived from a formula using measured luminosity and radius, not a "true" experimentally measured temperature. Johnjbarton (talk) 01:57, 25 July 2024 (UTC)

As you doubtlessly know, we can't just stick a thermometer into the solar photosphere, and there aren't too many different ways to measure things when the object in question is a sphere of very hot hydrogen at an astronomical distance... As far as I know, applying Stefan-Boltzmann (as described in the IAU resolution paper and here) is the usual method to get the solar effective temperature. The nominal value (being close to the "commonly accepted estimates") is probably as close to a "true" value as we can get, unless someone decides to re-do the necessary experimental measures with currently available instruments. 69.165.195.198 (talk) 11:51, 25 July 2024 (UTC)

Indeed. But the description in the paper of these "nominal values" is very puzzling. What does "commonly accepted values" even mean? "conversion factors only"? "true solar properties"? Bizarre choice of words for what should have been "based on our review, these are the most accurate values of these properties at this time."

But I agree this seems to be the best we can do. Johnjbarton (talk) 16:49, 25 July 2024 (UTC)

Too much on one ref outdated ref?

This one ref from 1977 with 22 citations is used 7 times in the article.

• Abhyankar, K. D. (1977). "A Survey of the Solar Atmospheric Models". Bulletin of the Astronomical Society of India. 5: 40–44. Bibcode:1977BASI....5...40A. Archived from the original on 12 May 2020. Retrieved 12 July 2009.

It seems to me that something like

• Mullan, D. J. (2009). Physics of the Sun: A First Course. United States: CRC Press.

would be much better as a source. Johnjbarton (talk) 01:30, 25 July 2024 (UTC)

Equatorial Radius

Isn't it kind of misleading to put meters as the equatorial radius unit because you would expect the unit to be kilometers instead. PeanutbutterCat6Meow (talk) 14:54, 7 August 2024 (UTC)

Also I noticed that the surface area is in square kilometers instead of square meters which you would expect if radius is in meters. PeanutbutterCat6Meow (talk) 15:26, 7 August 2024 (UTC)

I don't know which unit one should "expect". With the metric system, in any case, conversion is trivial (10^8 m = 10^5 km; 10^12 km^2 = 10^18 m^2). For what it is worth, the units are the same as in the given sources, which have (resp.) the radius in meters and the surface area in kilometers. 69.165.195.198 (talk) 22:47, 9 August 2024 (UTC)

"The Sun" or "Sun"?

Why do we call "The Sun" and not just simply called "Sun", like other stars names (Spica, Arcturus, Vega, etc) that don't have "The" word accompanying them? 2001:1388:1B8E:BBB1:9CBC:C8B4:1DCC:4732 (talk) 18:17, 11 August 2024 (UTC)

Once outside the Sun's surface, neutrinos and photons travel at the speed of light.

To me this figure label makes no sense. Neutrinos are believed to have a mass, so if special relativity is right, they cannot travel at speed of light. On the other hand photons should always travel at speed of light, regardless if the photon is in the sun or outside. The speed of light and especially time progression in the sun might be different from the normal value on earth and the mean free path is short, but photons should still travel with speed of light. 80.135.118.117 (talk) 16:23, 19 September 2024 (UTC)

For what it's worth, this is referring to the diagram in the "Sunlight and neutrinos" section. The diagram isn't particularly interesting, is imprecise, and the caption is obscure. The fourth paragraph of that section explains what the caption refers to, but is a factoid largely irrelevant outside supernova explosion studies. Tarl N. (discuss) 22:41, 19 September 2024 (UTC)

Source of Energy

In the introduction, without citation, there is a claim that The Sun is by far the most important source of energy for planet Earth. What does this mean? It does not relate to kilocalories or kilojoules or calories, clearly. Does it provide the greatest amount of solar power, literally, to animals and machines that store or use it? Or is it that the total volume of photosynthesis energy for plants exceeds animal and plant calorie consumption? Or do solar effects create weather systems, waves etc with overriding kinetic energy? Etc etc. An explanation of 'energy' or a citation is required. Or else this is genuinely vague beyond comprehension. Texluh1138 (talk) 23:41, 2 October 2024 (UTC)

@Texluh1138 In general, per MOS:LEAD the intro paragraphs don't need citations if the article supports the content with verifiable refs and the topic is not controversial. The actual sentence is:

• It is by far the most important source of energy for life on Earth.

which in my opinion cannot be controversial. Note "life on Earth".

This is supported by the ref in the "General characteristics" section.

• The energy of this sunlight supports almost all life on Earth by photosynthesis,("The Sun's Energy: An Essential Part of the Earth System". Center for Science Education. Retrieved 24 May 2024.) and drives Earth's climate and weather.("The Sun's Influence on Climate". Princeton University Press. 23 June 2015. Retrieved 24 May 2024.)

Johnjbarton (talk) 23:51, 2 October 2024 (UTC)