Astronomy & Space
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Apparent Brightness

Observed brightness from luminosity and distance.

Formula

b=L4πd2b = \frac{L}{4\pi d^2}

Variables

LLuminosity
dDistance

Example

Move a star twice as far away and it appears one-quarter as bright.

Did You Know?

Brightness falls off with the square of distance — double the distance, one quarter the light.

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