Are stars different colors?

Stars come in an extremely wide range of colors! Our universe provides everything from bright blue supergiant stars, to deep magenta dwarf stars, to bright red-orange giant stars, to our own yellow-green star and everything in between.

There are two ways to think about the color of a star. First, there’s the color of light that the star produces the most of. Each star produces a broad variety of colors of light, but there is always a peak in that range - one color will always be produced more often relative to the rest. This is usually the color that astronomers use when they are talking about a given star - this particular color can be useful to find out other things about the star, like the temperature on the surface.

However, this ‘most commonly produced color’ is not always the color it would appear if you were to sit at a telescope and look at it directly, or if you could zoom around in a spaceship and look at it up close. This difference is due to the way that our eyes process light. If the star were only producing light at the “most commonly produced” wavelength, then our eyes would mostly register a color that matches that wavelength. But when more than one color of light is coming at us, our eyes effectively take an average of all the colors of light that the eyeball is sensitive to.

For instance, if you look at the sun (carefully), it appears white to our eyes. ‘White’ light is simply how our eyeballs process the mixture of the rainbow of colors produced by the sun. The red, orange, yellow, green, and blues blend together to make white, even though there’s more ‘yellow-green’ being produced than any other color. You can see all the colors produced by the sun in a rainbow - but since each color is split into a different part of the sky, your eye no longer has to average the colors coming in, and you can spot the yellows and greens.

It’s a very interesting feature of our eyeballs and the range of colors produced that means we will not see stars that look “green” to us. We can spot yellow stars, red stars, and blue stars, but when stars produce green light more frequently than any other color, our eye averages the colors together and makes white. It will do this over a pretty broad range of most commonly produced colors, until there’s either enough extra blue light to give the white light a blue tint, or enough red that our eyes process the light as yellow or orange.

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