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
I have an astronomy degree, and teach physics. The Sun is, essentially, white. If you take a look at the percentage of photons radiated from the Sun as a function of wavelength, the highest percentage are those around 500 nm, which is perceived as green to the human eye. However, the Sun also emits plenty (Although fewer) photons in various other wavelengths, in a distribution roughly approximated by that of a blackbody radiator with the same surface temp of the Sun (Google “Sun blackbody spectrum,” it will show you a decent model of it).
Because sunlight not only emits green, but also comparable amounts of surrounding wavelengths of light, these all blend together when registered by the human eye. Our eyes register a relatively spread out distribution of these wavelengths as “White,” and so that’s what the Sun appears to be for us.
Hotter stars shift more towards blue, and cooler stars towards red. The yellow/orange appearance of the Sun during the morning/evening is because that white sunlight is traveling through a thicker column of air before reaching an observer. Blue light scatters more readily than red light in Earth’s atmosphere, so the blue light is “Filtered” during sunrise/sunset, giving them their distinctive hues. The effect that causes this is known as Rayleigh scattering, if you want to learn more.
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