What color is the sky?

dsisk559

Hi I'm writing a story and I need to figure out what color the sky is on a planet orbiting Zeta Tucanae that has close to the same atmosphere as earth.

just so you know Zeta Tucanae's Spectrum is F9V and Color Index is 0.576

It would be great if you can tell me how to find the color myself, or direct me to something that will, that way I won't have to bug you guys in the future.

Thanks alot,
Dan

tiny-tim

Hi Dan! Welcome to PF!

F9 is only two grades hotter than the Sun (the Sun is G2, and it goes F9, G1, G2, …), so the intrinsic light will be pretty similar.

But the sky colour really depends on the thickness of the atmosphere, and whatever's suspended in the atmosphere.

The Sun's light is actually white, but Earth's atmosphere is so thick that diffraction makes the sky blue and direct sunlight yellow.

(btw, I've never really understood why the Moon doesn't also look yellow, on that basis

)

On Mars, the sky is red, but that's only because of all the red dust in it.

tiny-tim

From http://en.wikipedia.org/wiki/Rayleig...from_molecules …

The strong wavelength dependence of the scattering (~λ⁻⁴) means that blue light is scattered much more readily than red light. In the atmosphere, this results in blue wavelengths being scattered to a greater extent than longer (red) wavelengths, and so one sees blue light coming from all regions of the sky. Direct radiation (by definition) is coming directly from the Sun. Rayleigh scattering is a good approximation to the manner in which light scattering occurs within various media for which scattering particles have a small size parameter.

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