Why might a star that is intrinsically very luminous appear faint when viewed from Earth?

Answer

It is located extremely far away, spreading its energy thin.

Apparent brightness is the result of the star's intrinsic luminosity diminished by vast intervening distance; immense distance can spread the energy output so thinly that even a giant star appears faint.

Why might a star that is intrinsically very luminous appear faint when viewed from Earth?

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Why Would The Size Of A Star Affect Its Luminosity? - Physics Frontier

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