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Thursday, August 21, 2008

The color of stars

Phil Plait (Bad Astronomy) explains why there are no green stars. The short version:

[T]he only way to see a star as being green is for it to be only emitting green light. But as you can see from the graph above [showing the broad spectrum of emitted light], that’s pretty much impossible. Any star emitting mostly green will be putting out lots of red and blue as well, making the star look white. Changing the star’s temperature will make it look orange, or yellow, or red, or blue, but you just can’t get green. Our eyes simply won’t see it that way.

That’s why there are no green stars. The colors emitted by stars together with how our eyes [and brains] see those colors pretty much guarantees it.

For those who are really interested, Matt Springer (Built on Facts) explains the Stefan-Boltzmann distribution, which provides a reasonable approximation for the intensity of a given wavelength of light given a star's temperature.

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