Is it yellow because from Earth it usually looks yellow to us? Or is it white because the sun gives off all wavelengths of light (white light)? Or is it some other color?
In: Planetary Science
It’s white. Consider the fact that all that blue light coming from the sky is also from the sun. When you look at the sky, you are seeing sunlight.
Short answer is, yes.
Our sun emits light, in all it’s wonderful spectrum. Our misuse of the term “visible spectrum” is humanity’s incapability to think outside our species. So, saying the sun has a color would deny the existence of the rest of the spectrum.
I will leave it to someone else to go into great detail to what a colorblind individual would perceive.
Every star has an average peak wavelength which we can say is it’s “color”. Every star also emits a broad range of energy (light) across many wavelengths.
The sun’s peak is in 480-500nm range which is blueish-greenish. But that is peak! On Earth, we perceive this color as yellowish as it is filtered through our Nitrogen atmosphere and makes the sky look blue! (yellow+blue=green as every child knows)
But because it emits many spectra, we see it as white with our eyes. It also glows in the infrared and ultraviolet (which we cant see). It glows in XRays and microwaves and many other ranges we cant see without instruments.
In astronomy, stars are classified by their peak because that indicates mass and many other derived factors like age too.
Its all colours or white, its a near perfect black body source, and emits a wide range of radiation, including all of the visible spectrum. For visible light, it produced mostly a green light, but not enough in comparison to others to skew how it would look.
Unfiltered, if we could safely look at it without burning our eyes, it would be white. The light emitted from the sun is absurdly bright and emits waves in the full spectrum that human eyes can see and then some. So if you chose to momentarily stare directly at the sun (don’t) it would appear white in the moment before it permanently burned your retina. The sun in the full sky isnt truly yellow. That’s sort of just the color used for cartoons and drawings. It’s white. As it gets lower in the sky to the point it’s safe to look at it begins to appear a yellowish color at sunset is because some of the highest frequency of light wave are being filtered out by the much longer span of atmosphere it’s passing through to reach your eyes.
Short answer, white.
To some extent, everything is white. The light we see from our sun is from something called “black body radiation”. It’s a fancy way of saying that when things get hot, they start glowing. Fun fact, this is what we’re talking about when we talk about light “temperature”. A 4000K light has the same spectrum as a piece of matter heated to 4000 Kelvin.
The weird thing is that they glow in the entire electromagnetic spectrum. They start emitting everything from radio waves, to gamma waves, every wavelength between them and every wavelength beyond them. That includes the entire visible spectrum. Lower frequencies have less energy and are emitted more. Higher frequencies have more energy and are emitted less.
The other weird thing is that the amounts of each wavelength have nothing at all to do with the type of element that’s getting hot. It’s entirely a question of how hot it is. The hotter it is, the more EM radiation is released at each wavelength.
We can only see a little bit of that radiation. It needs to be in the visible spectrum and it needs to be bright enough. A cold lump of steel emits so little of any radiation that it looks black (unless you have an other light source). As it gets hotter, the reds are the first wavelengths to get strong enough to see. As it continues to get hotter, you’ll see more and more of the higher wavelengths and that makes it look more orange and then yellow. Eventually you see so many of all the visible wavelengths that it just looks white.
There are variations between whites though. Hotter stars look “bluer” that is, they have more light visible at shorter wavelengths. Cooler stars look “redder”, for the opposite reason.
Then there’s an other weirdness. Some of the gasses in the atmosphere absorb very specific wavelengths and re-emit them at longer wavelengths. If you look at a star with a spectroscope (basically a box with a prism and a very clear screen) you can see black bands of missing light. Those are the wavelengths absorbed by certain gasses. So it’s not “truly” white, since we’re missing a few wavelengths. It’s pretty useful since we can use it to analyze the atmospheres of stars.
It is not yellow. It is white.
Near sunset, or when the sky is hazy, the blue end of the spectrum is scattered away to varying degrees, leaving it looking more yellow or even red. That’s because of [Rayleigh scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering) for the most part, and others will give you an explanation for that.
The true spectrum of the sun from outer space is approximately a [black body radiation](https://en.wikipedia.org/wiki/Black-body_radiation) spectrum, with some deviations (because the outer opaque region of the sun isn’t of uniform temperature, and there are [absorption lines](https://en.wikipedia.org/wiki/Fraunhofer_lines) associated with hydrogen and helium, as well as some other elements.
But that’s not relevant. The sun is *by definition* white, because our eyes and brains evolved to see during the daytime, and so whatever the spectrum of the sun during daytime is *defines* white. It’s the default pattern of illumination for things that humans see.
We don’t think of the sun as white, because it is too bright to look at directly — which is good: There’s never any need to, and it means that our eyes can be sensitive to darker illumination without needing to be shielded sufficiently to look directly at the sun. The only time it’s dim enough to look at directly is when there is a lot of atmospheric scattering in the way — precisely what makes it look yellow or even red at sunset or on very hazy days.
But if you were to look at the sun on a clear day through a sufficiently dark neutral-density filter, it would just look white, because it defines, biologically and socially and developmentally, what we understand to be white.
In space it would be a tiny bit bluer.
How i would explain it to a kid:
Shine a red/green/yellow light on some what paper. What do you see? Paper looks red/green/yellow. It shows what colour is shining on it.
Take the same piece of paper outside in the middle of the day. What colour does it look now? White. The sun is shining white light.
I would then show them the same light with a prism. You can then see all the colours are contained in that white light.
The colour of the sun depends on the atmospheric conditions and time of day. For example, on a clear sunny morning the sun will appear orange-red because the blue (shorter) wavelengths of the solar spectrum will scatter more, thus less of them will make it into your eye directly from the sun. If the sun is directly above you an a clear day, it will appear white/lightly-yellow, as blue, green, and red wavelengths would more or less be at similar intensity once superimposed with our eyes’ spectral response, which actually weighs heavily toward green wavelengths. All of the atmospheric conditions in between the sunrise and the sun being directly above will cause the colour of the sun to appear different at various times of the day.
Anyone that says they know what color a star is, is misinformed at best, lying at worst.
What we humans see, here in earth’s atmosphere, is not accurate. Saying starlight is white is also partially wrong, as it contains all wavelengths of electromagnetic spectrum, something we humans only see about 4% of.
Starlight is full spectrum light, at max intensity, our eyes, and most of our optical sensors, get washed out in high intensity light, so things become white. When we look at things through other lenses or wavelengths, like xray, nearferred, violet, ultraviolet etc… we see stars as many different colors.
For a five year old, the best explanation is starlight is too bright to define a color, and the earth’s atmosphere absorbs some light making it appear more yellow to our eyes.
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