I know it's a simple question, but even I progressed in astronomy, I always had this question. So, I know the Sun, in the MK classification system, it's G2: yellow. But I also know the sun, in visible spectrum, is white! But when I search for NASA photos of Sun in this spectrum, I find some photos with the Sun being yellow, and others white, with some of them being even orange! What is happening here? Is something incorrect?
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$\begingroup$ The "colour" of the Sun depends what you are looking at it with. A photo alone tells you nothing. $\endgroup$– ProfRobCommented Dec 1, 2022 at 16:00
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1$\begingroup$ Related: What's the rationale behind the false colours in solar observation photographs? $\endgroup$– David HammenCommented Dec 2, 2022 at 0:05
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1$\begingroup$ Unfortunately, a lot of the links in the one answer to the above linked question are broken, and I cannot find where they have been moved, nor can I find them on archive.org. That answer needs patching. Doggone internet! $\endgroup$– David HammenCommented Dec 2, 2022 at 0:11
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2 Answers
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Although the emission peak of light in the solar spectrum is more or less in the yellow-green part of the visible spectrum, it also emits a lot of red and blue light, and about the same quantity. Suppose you combine all the colors (talking about light), then you basically see white.
If you see NASA images of the sun, they are false color images, you could make them look whatever color you like, but they do not represent what the eyes would really see.
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$\begingroup$ Yeah, you are right. When a star is too red, it would still emits some green and little blue, so it would look orange. The sun is white just because it emits more or less the same blue and red light. $\endgroup$ Commented Dec 1, 2022 at 17:45
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5$\begingroup$ The Sun is white because that is what white is defined to be. The Sun is not "white" in terms of the engineering defintion of equal power at all frequencies. $\endgroup$– ProfRobCommented Dec 1, 2022 at 17:53
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$\begingroup$ So, you both agree or disagree? $\endgroup$ Commented Dec 1, 2022 at 23:08
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$\begingroup$ en.wikipedia.org/wiki/White_point I gave up trying to understand color decades ago, but as far as I can tell, "white" is whatever we say it is at the moment. $\endgroup$– uhohCommented Dec 4, 2022 at 3:07
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$\begingroup$ Of course, there is probably a strict definition of what is white, and it is also a cultural thing, but we can all agree when something is more or less white. This is not defined in terms of what the Sun looks like, but by what we perceive. The thing is that the Sun is just more or less white, and the colors we see in images is just false color. Are there more orange/red stars as seen by the eye? Yes. Is the Sun orange to the human eye? No (significantly). $\endgroup$ Commented Dec 5, 2022 at 16:43
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The sun is a star that emits energy in form of heat and light due to incandescence and nuclear fusion.
In this emission spectrum, we can see, there is a considerable amount of all visible colors being emitted so the light will appear as white to us from space.
But when observed from Earth due to Rayleigh scattering and the presence of these bluish colors being more than reddish ones the bluish colors are easily scattered giving the sky a blue color, now the light reaching us from the sun has more yellow-reddish colors, and that's why the sun seems yellow to us when observed from the ground. The colours of stars as per MK system is what the observer might observe without any optical aid, ie the light has been filtered in the atmosphere before reaching the observer.
The yellow sun in outer space is generally an edited image of the Sun.
This is the true color photo of the Sun.
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$\begingroup$ Could you please add a caption/source for the last image? $\endgroup$ Commented Dec 8, 2022 at 13:23
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$\begingroup$ You should probably include this information in your answer. $\endgroup$ Commented Dec 8, 2022 at 20:14