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What would be the colours of the sky at different points of the day if the sun was a blue star? This is assuming that our earth is at a similar distance away from the surface of the blue sun as it is from the white sun. And this distance causes the same amount of scattering.

Also, what would the colour of the sun be at different points of time in the day? I assume the noon sun wouldn't be the same white anymore?


EDIT: I understand that our perception of colour and its linguistics might change. But the sake of this question (and my curiosity), let's just assume that this is being observed by a human that has the same colour perception and linguistics as we do.

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  • $\begingroup$ What kind of blue do you mean? The answer here might be useful. $\endgroup$
    – Ruslan
    Commented Apr 11, 2022 at 19:57
  • $\begingroup$ @Ruslan I hadn't given that much thought before. But for the sake of this question let's say 7400K, 1 bar star at 85-degree elevation $\endgroup$
    – Amabilia
    Commented Apr 11, 2022 at 20:12
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    $\begingroup$ Our perception of colours wouldn't be the same probably... ;) $\endgroup$
    – kricheli
    Commented Apr 11, 2022 at 20:28
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    $\begingroup$ BTW, blue stars are very luminous. Your planet needs to have a much bigger orbit than 1 AU. $\endgroup$
    – PM 2Ring
    Commented Apr 12, 2022 at 2:49

3 Answers 3

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Short answer: yet more blueish. ;-)

Long answer: colour perception is highly subjective, and so is colour linguistics. What kind of answer do you expect? If you are satisfied with a spectrum, then just take Planck's law and mask it with the scattering spectrum of your choice. If you want to see what you would get, take the image manipulation program of your choice (gimp?, photoshop?...) and shift the color of an image by about 2400 K. If you are more of an experimental guy/gal, see if you can find an LED light with a color temperature of 7400 K, and shine it on the still life of your choice.

Colloguially speaking, the results will be far from interesting. It's just Planck, nothing more. As to the LED experiment, expect something like the cheapest chinese LED spotlight from 2010.

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  • $\begingroup$ Thanks for the reply! Will try those out $\endgroup$
    – Amabilia
    Commented Apr 11, 2022 at 20:55
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I guess by blue you mean a Plnck spectrum peaking at blue light. Rayleigh scattering will affect the shorter wavelengths, violet in this case, so the sky color will have an excess of violet.

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You would see negligible amounts of change in the sky's color. The sun emits all colors of the visual spectrum, giving everything its color from your perspective. If the sun were to suddenly turn blue (Assuming we wouldn't die from the heat of a now blue sun immediately) the sky would look a little more blueshifted, but other than that, almost nothing would change.

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