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The Question

(Submitted April 08, 1997)

I have looked in and read many great books on astronomy but never found an answer to this question: Do green stars exist? If they don't why don't they? Is it theoretically possible to have a green star? And if they do exist how would they be classified(main sequence,supergiant,etc.)?

The Answer

Yes, stars of every color in the rainbow exist. In fact a star's color tells us something very important about it -- its temperature.

The visible spectrum goes as: Red, Orange, Yellow, Green, Blue and Violet with a red photon having less energy than Blue. So, blue stars are hot and red stars are cool (cool for stars that is).

The reason that people do not often mention green stars is simply that green is in the middle of the visible spectrum. Therefore a star that gives off a plurality of its light in the green (similar to our Sun), also gives off lots of red, orange, yellow, blue and violet light. When we see this mixture of colors it usually appears white or yellow.

Sincerely,

Jonathan Keohane
-- for Imagine the Universe!

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