It’s yellow, right?

Well, it appears yellow most of the time because of our atmosphere. But it’s not really yellow.

Photons of light from across the visible spectrum reach the Earth’s atmosphere. But more energetic (and shorter wavelength) photons are scattered away by particles in the atmosphere. So we don’t see blue and violet colors from the Sun as they’re scattered across the sky.

(This is also why the sky is blue, by the way.)

Particles with longer wavelengths, yellow, orange and red (the longest) have a better chance of making it through the atmosphere without being scattered. For most of the day the Sun’s light is passing through enough of the atmosphere such that the yellow region of the spectrum is most represented.

However, at midday, the Sun’s photos are going through the least amount of atmosphere, so it has a slightly blueish tint. And at sunset, of course, its photons are traveling through the maximum amount of atmosphere relative to your eyes, so only the reddish photons make it through.

Anyway, I write all of this to say two things. One: the Sun is actually white — the emission of all wavelengths of visible light, without absorption.For more on this, Fraser Cain has a nice article at Universe Today.

And two, NASA’s Solar Dynamics Observatory can observe a variety of wavelengths of light invisible to the naked eye, and then converts the wavelengths into an image humans can see. See them in this glorious video:

According to NASA, here’s how to interpret the colors above:

Yellow light of 5800 Angstroms, for example, generally emanates from material of about 10,000 degrees F (5700 degrees C), which represents the surface of the sun. Extreme ultraviolet light of 94 Angstroms, which is typically colorized in green in SDO images, comes from atoms that are about 11 million degrees F (6,300,000 degrees C) and is a good wavelength for looking at solar flares, which can reach such high temperatures By examining pictures of the sun in a variety of wavelengths — as is done not only by SDO, but also by NASA’s Interface Region Imaging Spectrograph, NASA’s Solar Terrestrial Relations Observatory and the European Space Agency/NASA Solar and Heliospheric Observatory — scientists can track how particles and heat move through the sun’s atmosphere.

It goes without saying, of course, that the energy from the Sun is the source of life for nearly ever organism on Earth, including you and me.