What color is the sun?

[Admin]

You probably learned this at school.

What color is the sun? : Read more

 

[Helio]

It's stunning to see brilliant people make such misleading statements, and it is a common occurrence when it comes to the Sun's color - my favorite topic, though this topic is more an accident than otherwise.

So, I will parse it, if you don't mind my pedantry, admittedly.

"So essentially, if we're trying to figure out what color the sun is, we need to dissect the sun's rays here on Earth and quantify them. "

But is the "color of the Sun" that which we see under our atmosphere, or are we going to call its color that which we would see from observing the Sun from above our atmosphere (with neutral filters to put it in the normal photopic range)?

It should be defined as seen from above our atmosphere, which can be determined quantitatively from terrestrial spectral irradiance data by adjusting for the known extinctions due to our atmosphere, but its unclear if that is his "quantitative" direction, which is the question. [Better yet, we have hundreds of these taken from spacecraft like SOHO and the SDO.]

It's often stated that the Sun is white because it emits all the colors of the visible spectrum. But those who make this claim know better than to use that argument because they know that all stars emit all the colors, even red stars.

Fortunately, the article addresses the importance of whether or not one color is stronger than the others...

'Critically, though, these frequencies aren't present in precisely the same amount, it's just that the variances aren't significant enough to be meaningful. "The color components of sunlight are so close enough to being present in equal amounts that it is much more correct to say that the sun is white than to say it is yellow, orange, or any other single, pure color," Baird said. '

[my underline]

His claim is both false and true, ironically. First, to present the frequency (or wavelength) distribution as being equal is patently false....



Notice how uneven the intensity is for each wavelength (frequency). The most intense band is in the blue colors.

But this profile fits essentially every star in the universe, (see Planck distribution) since stars emit close to that of black bodies. The peak wavelength, however, will vary with star type (ie temperature). Red stars have peaks, not surprisingly, in the red.

But, on the other hand, he is right. This is because the eye works by responding to photons, so it is really a story about the distribution of photons of different wavelengths that our color cones and rods "see" that produce a color result.

But wavelength energy and photon energy aren't 1 to 1. Photons that give us a blue color result require almost twice the energy of the far "red" photons. This has the effect of cutting that blue peak down to the level of the red band, and other colors.

Here is the better presentation that is found by plotting the photon flux density distribution.



The profile, as somewhat suggested in the article, is relatively even. So this is where he would be correct with his claim of an even distribution. I would call it flat as a pancake.

[These results, btw, are for the Sun as seen in space.]

There is a little more irony if you look for a peak in that photon distribution -- it's yellow?
But this peak is not really a peak but a pimple.

 

[Helio]

BTW, if you talk to him again, tell him the Heliochromologists wants to say "Gig 'em" to Don Corona.