Stars are classified by the spectral properties of their light. They are sorted into seven letter classes, from hottest to coolest: O, B, A, F, G, K, and M. Astronomers add another number and Roman numeral to categorize the star even more specifically, taking into account its size, brightness, and how close it is to the next letter in the classifying system. Our sun, for example, is a G2V star.
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Written by Curiosity Staff August 6, 2015
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