When you gaze at the night sky, it's obvious that the various stars are different; some shine more brightly than others, and some have noticeable colors. Scientists classify stars according to these two characteristics, but they do it with sensitive instruments that provide much more detail than stargazers—even ones with powerful telescopes—could ever manage to discern. In other words, scientists classify stars according to their luminosity and temperature, as determined by spectral analysi
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