Extrinsic Variables

Sometimes, a star whose luminosity is steady appears to vary because of variable external factors that affect how much light reaches us from the star. Extrinsic variability is really only apparent variability, meaning that the object itself is not getting brighter or fainter overall, but its brightness appears to be changing because the object's orientation to us is changing, or some other object is intervening along our line of sight to the object.

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