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Astro Quiz 19: No Green Stars?

Question #19 – Why are there no green stars?

Answer:

Well, there are green stars! At least there are stars that radiate the wavelength of light that we see as green. In fact, our Sun is a yellow/green star.

The problem with green is that its wavelength is right in the middle of perceptible light. Think of a rainbow – green is right in the middle. Its wavelength is not too short and not too long. Green is right in the center of the arc.

Since stars emit lots of different light at many different wavelengths, the human eye sees all these colors together as white light. If the star is very hot and emits a lot of blue light, we see blue, not green. If the star is on the cooler side, we see orange or red. The human eye simply does not separate out the green from all the other colors.

The green star image below is a false-color photo of our Sun taken by NASA's STEREO satellite, taken at extreme ultraviolet wavelengths. False color images show the Sun's atmospheres at a range of different temperatures, which allows scientists to focus on different features of the Sun. Green color photos show features at 2.7 million °F.

For more information, please read "Why are there no green stars?" on the BadAstronomy blog at Discover.com


Photo credit: NASA

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