Astronomy & Space
Advanced

Apparent Brightness

Observed flux from a source at distance d.

Formula

b=L4πd2b = \frac{L}{4\pi d^2}

Variables

LLuminosity
dDistance

Example

Inverse-square dimming

Did You Know?

Starlight dims with the inverse square of distance, so a star twice as far appears four times fainter.

brightness

Share this formula

More in Astronomy & Space

View all

Escape Velocity

Intermediate

Minimum speed to escape a body's gravity.

Orbital Velocity

Intermediate

Speed of a circular orbit.

Kepler's Third Law

Advanced

Relates orbital period to semi-major axis.

Schwarzschild Radius

Advanced

Event horizon radius of a black hole.

Hubble's Law

Advanced

Recession velocity of galaxies with distance.

Stefan–Boltzmann Law

Advanced

Luminosity of a star from radius and temperature.