Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the actual colour of the Sun?

  1. Apr 20, 2012 #1
    Hello, I've recently been trying to find out what colour the sun is, but I've had no luck.

    If you take a look at this picture:

    http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/plank_e_sun.html

    You can see that the maximum wavelength is in the green section. If so, shouldn't we see the sun as being green? Not a yellowish-whitish colour? Does the sun appear yellowish/white because the blue parts of the sunlight gets scattered as it travels through our atmosphere? Leaving yellow as the maximum wavelength when our eyes detect the light?
     
  2. jcsd
  3. Apr 20, 2012 #2

    mathman

    User Avatar
    Science Advisor
    Gold Member

    Although the max may be at green, all other colors are present, so the mix is white. The yellow appearance is as you described - blue light scattering in the atmosphere. The effect is even more pronounced at sunrise or sunset (sun appears more orange), since the path through the atmosphere is longer.
     
  4. Apr 22, 2012 #3

    Bobbywhy

    User Avatar
    Gold Member

    The color of the sun is just what you see when you look at it with your eyes. But DO NOT LOOK DIRECTLY AT THE SUN! You would damage your retinas permanently. You can easily find the true color of the sun with a prism. Hold it in the sunlight and move it around until you see a rainbow. Put a white card or paper in that place and see the sum total of the sun's colors.

    Note: if your prism is of poor optical quality, the colors will not be exactly true. One example of this is if you used a quartz crystal you'd not see any red, but you would see a beautiful pink band.
     
  5. Apr 27, 2012 #4
    to be blunt about it, we have a green sun.

    forget the whole "its absorbing these colors and rejecting this one" topic. if you were able to see the sun from a farther distance with nothing to distort our view of the sun, our eyes would see green. the "white" portion of it has more to do with its brightness. hold an LED flashlight right in front of your eye and it wont look blue, itll look white.

    i really dont recommend you hold an led flashlight into your eyes, just using an every day example
     
  6. Apr 27, 2012 #5
    the sun isn't absorbing or reflecting any light, it's just emitting it. Stars can be modeled faaairly well as blackbodies. Meaning that they emit the entire electromagnetic spectrum. The intensity of each wavelength of light is not the same, though, and it depends on the temperature of the object. A blackbody with the temperature of the sun has a maximum in the "green" part of the spectrum, but it also emits light at other wavelengths.

    Since green is right in the middle, basically, and the curve of intensity vs. wavelength is a big symmetrical hump, the sun emits *all* wavelengths of visible light and thus appears white to our eyes.
     
  7. Apr 27, 2012 #6

    Dotini

    User Avatar
    Gold Member

  8. Apr 27, 2012 #7

    Drakkith

    User Avatar

    Staff: Mentor

    This is incorrect. The Sun appears white no matter what intensity it is. The key is that your eyes compare the 3 different color channels relative to each other. Reducing the intensity of the Sun by 10,000x still gives you the same spectrum, as each color is being reduced in intensity by 10,000x also. As an example, we can see stars similar in appearance to the Sun in telescopes. These stars are not green or yellow, they are white.

    The LED flashlight probably emits enough light that all 3 color channels get overwhelmed and it appears white because of this.

    Edit: Another example. I went to do some solar observing a few weeks ago at a local science place, the Sci-Port they call it, and one of the things they had was a little device with a small lens in it that focused light onto a piece of white paper. The Sun was projected onto this paper and we could see it right there. Given that the paper was white, any color would have reflected off to our eyes. The Sun still appeared white.
     
    Last edited: Apr 27, 2012
  9. Apr 28, 2012 #8
    I'd add to this excellent answer with: https://en.wikipedia.org/wiki/Hertzsprung–Russell_diagram, and point out that color is just a label we apply to particular wavelengths of light that our eyes are equipped to register.

    I'd say we're closer to blind than we are being able to see the "actual color" of anything, given how narrow our ability to detect the electromagnetic spectrum is.

    Oh, another good example of this: http://sdo.gsfc.nasa.gov/

    We can't see most of the wavelengths visible to the SDO, but we can represent the information with false-color representations. These are necessary due to our limited faculty for observing light.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook