Violet astronomy. The Astrophysical Journal 2 : Retrieved Annals of the Cape Observatory 10 : Astronomy Letters 38 5 : October September Monthly Notices of the Royal Astronomical Society 2 : — Royal Observatory Bulletin November Astronomy Letters 32 11 : — March July The Astronomical Journal 1 : — January Evidence for an onset of the solar-type dynamo". Astronomy and Astrophysics 3 : — The Astrophysical Journal Supplement 1 : — Morse; Nicholas R.
Collins; Theodore R. Gull August But if stars have peaks in the ultraviolet spectrum that has wavelength little shorter than violet. Why don't we see those stars purple? The coldest stars appear red, as you mention, because the black body spectral peak is low enough that there isn't much at all in the green-to-violet range.
Purple and green star exists. For example, a blue supergiant star can have its surface temperature to K, which peaks at purple in the blackbody spectrum. However, our eyes are more sensitive to blue than purple, and the contrast between blue and purple in the spectrum is insignificant, therefore we see blue.
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Viewed times. If stars have peaks in the infrarad spectrum that has wavelength little longer than red. Enough speed, and the peak would sit in the violet band of the spectrum. A back of the envelope calc. A cooler longer wavelength star would need a greater approach speed. Seen from behind, the star would appear red shifted. To appear violet, the star doesn't have to be coming straight at the observer.
But, what if it is headed right at you? That gorgeous lavender you see in pictures of massive stars and the nebulae around them is hydrogen. The Balmer alpha line Hydrogen alpha photos of the sun, for instance, are true-color pictures. But the Balmer delta line The physics to understand what I just said is in Wikipedia, so I won't bother to explain.
On a world in a starburst galaxy, you could be close enough to something like the Tarantula Nebula or 30 Doradus to see that glowing hydrogen with the naked eye.
A number of kinds of star are actually colored ultraviolet. Only a small part of the light they emit is reddish enough for us to see. Central stars of planetary nebulae, for example, are usually hotter than K, which we see as blue-white. If you could shift such a star's spectrum until its peak emission was near nm, like hydrogen's Balmer epsilon, you would see those stars as distinctly blue, probably with some purple thrown in.
Assuming human eyes. Our own world has creatures which see well into the ultraviolet. A solar system where an abundance of Arcanite asteroids near the center of of the system would allow the introduction of potassium sulfide into the outer shell of the sun and be expelled as a burst of violet plasma.
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