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I read an article by NASA in which the following assertion was made:

The sun, in fact, emits light in all colors, but since yellow is the brightest wavelength from the sun, that is the color we see with our naked eye

Now, as a photographer, I was always taught that the light from the sun was brightest in GREEN and that is why green is the color to which our eyes are most sensitive. In fact, if we look at the spectrum of the sun:

solar spectrum

As we can see from this graph, the most intense light from the sun is not yellow, it is green. So, is NASA just wrong or what? Why does the sun appear yellow?

Qmechanic
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Ambrose Swasey
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http://solar-center.stanford.edu/SID/activities/GreenSun.html A link from Stanford which details what tfb commented. They Sun is not yellow, does not even look yellow except under certain conditions. It is full visible spectrum and is white if you choose to directly look at it in unfiltered and damage your eyes.

dlb
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    Uh, ok, then why did NASA say it is "yellow" (see quoted text)? Are they wrong? That is what the question is. – Ambrose Swasey Aug 31 '17 at 17:57
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    I think they are wrong: first of all it's not actually yellow, and secondly what your eyes or a camera see can be only vaguely related to what the spectrum is, especially for very bright sources. –  Aug 31 '17 at 18:07
  • I have done some more research. The sun is yellow. It is a G class star. G class stars are yellow. So your assertion that the sun is not yellow is incorrect. White stars are A class stars. – Ambrose Swasey Aug 31 '17 at 18:26
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    @AmbroseSwasey To put it gently, your research is flawed. The Sun is a Yellow Dwarf star. That is a classification, not a color. The color is white. Your linked article from NASA clearly states the Sun spectrum is white. It then gives reasons it appears yellow in photographs. Photographic appearance is not physical reality. NASA is not wrong, your reading of their article is. – dlb Aug 31 '17 at 18:47
  • When you're talking about the color of a light source (as opposed to a reflective surface), the meaning of "white" is highly subjective. I can turn on a "warm white" lamp in one room of my house, and if you ask anybody inside the room to name the color of the light, they will say, "white". I can do the same with a "daylight spectrum" lamp in another room and get the same answer. But if you stand outside the house in the dark, and look at the two windows, you would say that the first window was distinctly yellow, and that the second window was distinctly blue. – Solomon Slow Aug 31 '17 at 18:50
  • @dlb The "physical reality" is that not only the sun, but all G class stars appear yellow to the human eye, that is why they are called yellow stars. If you look at stars similar to sun such as Procyon A or Pollux in a telescope, you can clearly see that they are yellow. – Ambrose Swasey Aug 31 '17 at 18:56
  • @AmbroseSwasey Doing a Google search of "Is the Sun white or yellow" is a simple task which will give you many reliable sources that clearly state the Sun emits full visible spectrum and is white. I sited one on those. If you do not care to do that simple search and accept well known sources like Stanford Univeristy solar research center, then clearly you are posting a question for the sake of argument so moving one. – dlb Aug 31 '17 at 20:17
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Using some of the links in the comments and other research I have figured out the answer to the question.

The answer is that the apparent color for any source of light is due to the addition of the component light that makes up the spectrum for that source.

In the case of the Sun, it emits most strongly in the green-yellow-red part of the spectrum. If green is added to red, it produces yellow. The sun generates other colors as well, but they are overpowered by the energy of the green-red parts of the spectrum.

If we examine the spectral diagram from the question above, we can see that the area under the curve in the green-to-red sector is much larger than the area under the curve for the blue-violet parts of the spectrum. Therefore, it is the green-red part of the spectrum that is generating the net color.

Ambrose Swasey
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