Why no green stars?

Have you ever looked up at the night sky and admired the colors of the stars?  Most stars appear white because they’re too dim to trigger your perception of color, but a few bright stars are bluish, yellowish, orangeish, and reddish! Go outside yourself on the next clear night (a rarity in Seattle, I know, I know…) and check it out!  Or, next time you come to one of our planetarium shows, pay attention to the stellar colors on the dome above you.  The sky is pretty colorful if you know what to look for.

ImageWhy do stars have different colors?  It turns out the color is determined by the star’s temperature.  You’re probably used to thinking of red as a warm color and blue as a cold color, but stellar temperatures work the opposite way: blue stars are the hottest stars and red stars are the coolest stars (though of course still VERY hot!).  So, we’ve got blue, yellow, orange, and red stars, but what about green stars?  Turns out there are no green stars!  Why?  Check out UW Astronomy grad student Eddie Schwieterman’s blog posts for the answer:  No Green Stars part I, and No Green Stars (and no violet stars) part 2.  Then go impress your family and friends with your new knowledge!



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