I’m creating an Earth-like world where the inhabitants and visitors to the planet see the planet’s sun as blue in color. I think that the best way to achieve this result is via atmospheric light filtering. The atmosphere would scatter and absorb the longer wavelength red light from the planets sun, resulting in the sun appearing to be blue. In 2021 in Beijing, a sandstorm turned the sky yellowish, and the sun blue. (Linked to an article about it at the bottom). If I want to achieve this result on my Earth-like planet, would I have to have a perpetual, global sand storm to achieve this result, or could particles be suspended higher up in the atmosphere to achieve this result without needing perpetual sand storms? I need a scientific explanation for why the particles stay suspended in the atmosphere.

Some limitations:

  • The atmosphere must be hospitable to Earth-life (or any life form that lives on Earth). It can’t be harmful or detrimental to these forms of life.
  • Because the atmosphere must be hospitable to Earth-life, the atmosphere’s composition should be similar to Earth’s.
  • I don’t want an all-desert planet. I want to have trees, and forests, and other environments similar to Earth.
  • The apparent color of the sun is due to atmospheric filtration. I’ve ruled out using a blue star due to too high of levels of UV light which would be harmful.


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    $\begingroup$ Note that the sun itself is so bright that it burns out any sense of color, so we perceive and photograph a pure white disk surrounded by a blue glow that fades to yellow and orange, but a sufficiently robust photo sensor pointed straight at it would report that the direct light was redder than the sun's natural color, not bluer, and the objects lit up by sunlight would look redder, not bluer, too. $\endgroup$
    – g s
    Apr 29, 2023 at 3:47

1 Answer 1


First off, do you need a scientific explanation for a blue sun? How far could you go with just "The sun is blue" and moving on? If you are after a scientific explanation to explore the possible side effects, those would likely have to be non-Earth-like effects on biology. On that note, here we go:

This answer has a pretty good idea: https://worldbuilding.stackexchange.com/a/30072/94677. They suggest 1 micron wide particles. Most atmospheric gases have are around .0001 to .001 microns wides. At the 1 micron level we need stuff like smoke, fumes, or very fine dust, but these would all likely have other tints. Interestingly viruses and small bacteria are about the perfect size, so you could have an atmosphere constantly infected with some virus (an interesting idea for story and worldbuilding).

Edit: Dust is heavier than air and thus slowly falls over time and can be washed out due to rain. At around the 1 micron level, just having a consistent breeze would probably be enough to keep things moving and particles suspended. You probably won't have a strong effect around the equator where winds just aren't very strong but many other places could be engineered to have consistent wind. The harder part would probably be avoiding rain, though you could just have the particles be replenished at a sufficient rate to offset this. To get the particles up there in the first place, almost anything could work: volcanic activity, sand storms, some kind of plant spores, etc. If it kicks up dust and keeps down rain, it'd probably work.

  • $\begingroup$ I saw that answer you linked, but that only partially answers my question. In my question, I already mentioned particles suspended in the atmosphere. What I’m trying to find out is how to get the particles suspended in the atmosphere, and how to keep them there? Would this require a perpetual storm, or could this happen otherwise? $\endgroup$
    – Kal Madda
    Apr 29, 2023 at 11:48
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    $\begingroup$ @KalMadda I see, I think I was slightly unclear on what exactly you were looking for and have updated my answer $\endgroup$
    – grepgrok
    Apr 29, 2023 at 16:38
  • $\begingroup$ Thank you for the answer! Sorry if I didn’t clarify my question well enough originally. $\endgroup$
    – Kal Madda
    Apr 29, 2023 at 17:05

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