As we have seen, the stars of Orion span a wide range of colors and therefore spectral classes, from huge blue B-class stars such as Rigel, through medium yellow G-class stars such as Chi 1 Orionis, to an M-class red supergiant, Betelgeuse. A star’s color tells us about its temperature; blue stars such as Rigel are hot, red stars such as Betelgeuse are cool. The stars in Orion vary in luminosity as well. For a star on the main sequence, its luminosity tells us about its mass; bright stars are massive, while dim stars are not. Once we understand the story told to us by a star’s light, we can readily explain why all of the stars we see shining in the night sky, including those in the constellation of Orion, look so different from one another.

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