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This question is really about the color of the sun. But NOT about its color at sunrise or sunset.

When I search for the color of the sun, I find dozens of articles, including many on SE, stating that the color of the sun is white (and it's just getting a little yellowish because of Rayleigh scattering). That matches our everyday experience, where we see the sun as a slightly yellowish white (except for at sunrise/sunset, which is out of the scope of this question).

But in most pictures of the sun from NASA and the like, the color of the sun is orange.

So I thought that maybe is the orange color on those pictures just an artistic effect, and not representing reality (but why are they doing it?). This article of the Washington Post also says something like that:

A picture of the sun taken in visible light was processed to make it appear orange

But when I saw the total solar eclipse last Monday (4/8/2024), I saw the solar prominence having an orange color (however, the pictures on the web are showing it as being pink). And according to the pictures from NASA it looks like a solar prominence has the same color as the sun has. Also, even Baily's Beads which are really part of the sun, have an orange color.

Also, there are some articles claiming that the sun is really green, like the one previously cited from the Washington Post which says:

“The sun would appear green if your eye could handle looking at it,” said W. Dean Pesnell, project scientist of NASA’s Solar Dynamics Observatory.

But some strongly disagree, see https://bigthink.com/starts-with-a-bang/what-color-is-the-sun/. So my question is mainly whether it's white or orange.

So what color is the sun really? (Again, ignoring sunrise/sunset) And how does everything I mentioned fall in place?

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    $\begingroup$ I actually saw unaided, an orange dot or bubble on the edge of the eclipse which puzzled me a great deal at the time. Later when I saw the NASA pics, I realized that it corresponded with the largest prominence. $\endgroup$ Apr 11 at 16:45
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    $\begingroup$ I saw a deep ruby-red prominence. I was wearing good, polarized sunglasses, though. They tend to make red more visible (and beautiful). $\endgroup$
    – JimmyJames
    Apr 12 at 20:15
  • $\begingroup$ I've heard previously that the sun appears yellow from earth because the atmosphere scatters the higher-frequency light from the sun (hence the sky appearing blue) and lets the lower-frequency light shine straight through. But then I heard that the sun is classed as a yellow dwarf. Which would appear to be saying it actually is yellow, but I've just read that this is an informal term and a misnomer. $\endgroup$
    – Stewart
    Apr 14 at 22:41
  • $\begingroup$ @Stewart I guess that by labeling stars with colors they include atmospheric scattering. $\endgroup$
    – George Lee
    Apr 15 at 23:29

4 Answers 4

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There are several things going on here.

  1. Structures that are seen in emission off the photospheric limb of the Sun - know as prominences - are emitting a lot of light at the specific wavelength of the Balmer H$\alpha$ line at 656 nm and these tend to appear "pink-ish" (when the Sun is completely obscured by the Moon), which is a mixture od direct red light from the prominence and white light scattered into our line of sight by the prominence material.

  2. Sunlight as a whole is "white". That is, when you put the solar spectral flux (as it would be above the atmosphere) onto a colour chart it sits in the white part. Yes, there is a slight amount of scattering when the Sun is at a high elevation but that has only a slight yellowing effect.

  3. The comment above applies to the Sun as a whole. When you look (don't look at the Sun) at the Sun with a camera it is clear that the photospheric disc is not uniformly bright - it suffers from limb darkening. This happens because nearer the limb of the Sun we see to lesser depths in the photosphere and, because the temperature increases as we move into the photosphere, it means the photons we receive from near the limb arise from plasma at a lower temperature. A lower temperature plasma is less bright and hence limb-darkening. However, a lower temperature plasma also has a spectrum that differs from the total spectrum of the Sun - it is indeed "oranger" than the total spectrum. To put it another way - the limb darkening effect appears stronger for blue light than for red. So, in this sense, when you see parts of the Sun close to the limb they should appear to be "oranger" than the centre of the disc.

  4. Whether any of this is actually detectable without precision measurements (see Neckel & Labs 1994, who measure the effect I discuss in #3) is unlikely. A direct view of sunlight from the photospheric disc is too bright for the eye to discern colour properly (don't try) and photographs do not necessarily give an accurate representation of colour and may have been post-processed/colourised for public consumption.

  5. The Sun's spectrum peaks at green wavelengths, but it would never appear green because your eyes have receptors that are sensitive to a broad range of wavelengths and the sunlight stimulates those receptors by having a spectrum that spans the full range of wavelengths in the visible spectrum. For something to appear green you would need to filter out most of the red and blue light either side.

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  • $\begingroup$ The idea that the sun is green seems like obvious bunk to me. Go out at noon with a blank sheet of white paper. What color does it appear to be? It's not green. $\endgroup$
    – JimmyJames
    Apr 12 at 20:18
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    $\begingroup$ @JimmyJames, that's not a reliable test - human colour perception is very good at normalising scenes, compensating for non-white illumination. The only useful description of the Sun's colour is a spectrometer plot. $\endgroup$ Apr 13 at 14:37
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    $\begingroup$ @TobySpeight Because of the evolutionary history of land-animal vision, with sunlight and daylight as the primary light sources for at least tens of millions of years, it makes sense to me to say that direct sunlight is defined to be white. $\endgroup$
    – zwol
    Apr 14 at 16:30
  • $\begingroup$ @TobySpeight 'White' isn't a color and I specifically referred to how it would appear. The quote also states: "sun would appear green" [emphasis mine] to a person. Pedantic fail. $\endgroup$
    – JimmyJames
    Apr 15 at 14:08
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The surface of the sun is (roughly) a black body emitter. It emits light over a wide band from the ultraviolet to the infrared. When we see this light it appears "white". Its actually hard to see this colour, the sun is just too bright, but if you look at the moon, you'll see the colour of the reflected sunlight, and it is white. Of course you could do the same thing with a piece of white paper, but with the moon you can see how the colour changes close to the horizon.

The sun is (kind of) a black body, because it is quite dense. But the gas in solar prominences is very thin and rarefied. Such gas glows in specific wavelengths as a result of particular energy levels of electrons. This is why neon lamps are red (etc) The hydrogen in a solar prominence will glow at a particular line called the Hα line, which is red/orange, and can appear "pink" against the corona. This colour is present in the face of the sun, but it is swamped by the black body emissions.

The "orange" pictures you see are often taken at ultraviolet wavelengths. They are coloured "orange" to make them look like we expect the sun to look: like "flames".

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And according to the pictures from NASA it looks like a solar prominence has the same color as the sun.

Note the photo you've linked here is taken in UV, not visible light. The prominence and the upper atmosphere of the sun (chromosphere) appear to be very similar. But the color of "the sun" is more dominated by lower layers (the photosphere)

So what color is the sun really?

The sun emits a spectrum of EM radiation, a lot in visible wavelengths. We can characterize the spectrum and there's no ambiguity of that.

Our entire visual processing system does lots of manipulation on the received radiation to turn that into a perception, with color being part of the perception. There's no unambiguous response to "what color is the sun". I would disagree with idea that the color is green. We don't generally characterize object's color as the peak wavelength. The entire (visible) spectrum is processed and delivers a color value.

Not explicitly asked in your question is "why does the sun look white (or maybe yellow), but the prominence looks pink or orange"?

The upper layer of the sun (and the prominences) are optically thin. They are emitting red light from hydrogen emission, but are usually overwhelmed by the more continuous spectrum from the deeper photosphere. During the eclipse when the photosphere is obscured, the colors from the hydrogen emission are visible.

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The camera might be looking in the reddish-orange 656nm H-alpha emission line, but probably the telescope's solar filter is just orange instead of neutral-density. I had a solar filter that made the sun look green.

Don't decide from random pix. Look at an astronomy site for a photo that tells what filter was used. Filter colours are standardized, so you can tell if it's ND.

This is the eclipse through an ND (true colour) filter. Pink is H-emission:

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