Why is the sun yellow, when the peak wavelength is green, almost blue?

Question

Wein's displacement law says the peak wavelength is:
2900/5600 = 0.518 um = 518 nm (this is very green, see the table below)

I'm not convinced that it's due to atmospheric Rayleigh scattering, because the astronauts don't see a green sun do they?

I suppose it must be that sunlight has more red and orange than blue and violet, etc., so our eyes interpret this as yellow.

So if the "cones" in our eyes are essentially R-G-B, then, if G is stimulated, but R is more stimulated than B, does this appear yellow?

thanks.

color, wavelength interval
---------------------------------
red ~ 630–700 nm
orange ~ 590–630 nm
yellow ~ 560–590 nm
green ~ 490–560 nm
blue ~ 450–490 nm
violet ~ 400–450 nm

Answer 1

To a reasonable approximation, the sun's light has a black body spectrum. Such a spectrum is extremely broad. If it were perfectly flat, it would be purely white in color. Since the sun's light observed from space peaks in the mid visible, the sun appears pretty much white there because of the spectrum's breadth.

The atmosphere, however, preferentially scatters blue light away from the line of sight, shifting the sun's "color temperature" lower by an amount that depends on how high it is in the sky (which determines how far it travels through the air). "color temperature" is the temperature of a true black body (not filtered by the atmosphere) that looks the same color to the human eye. The sun's typical color temperature is about 5000K, considerably cooler than the 5600 K you use in your formula. This gives the sun a yellower or (near the horizon) a red color.

Answer 2

This Site Might Help You.

RE:
Why is the sun yellow, when the peak wavelength is green, almost blue?
Wein's displacement law says the peak wavelength is:
2900/5600 = 0.518 um = 518 nm (this is very green, see the table below)

I'm not convinced that it's due to atmospheric Rayleigh scattering, because the astronauts don't see a green sun do they?

I suppose it must be that...

Answer 3

Is The Sun Green

Answer 4

sun yellow peak wavelength green blue

Answer 5

Wein's displacement law refers to blackbody radiators, and the sun is _not_ a pure blackbody radiator. Some of the color also comes from gas that is absorbing and reemitting light, or even becoming plasma. Hydrogen, for example, produces red as one of its brighter colors. Because the gases are _very_ hot, some atoms move away from us and some towards us all the time, which "spreads" out the spectral lines as well.

The equation for blackbody radiators is a good approximation for stars, but other factors make it somewhat inaccurate.

Answer 6

I totally don't have an answer! I just wanted to see what other people answered!

What a question!

(You hurt my brain too early in the morning ... need more coffee ... then I might read that website you were referred to! )

Answer 7

You have written and phrased your question very well. Instead of retyping, read this website:

http://www-istp.gsfc.nasa.gov/stargaze/Sun4spec.htm