How do Astronomers Use Brightness to Determine Distance?

Astronomers use brightness as a tool to measure distances through methods such as standard candles and parallax. Standard candles, like Cepheid variables and Type Ia supernovae, have known intrinsic luminosities, allowing their distance to be calculated based on their apparent brightness. Parallax involves measuring the apparent shift in the position of a nearby star against the background of more distant stars as Earth orbits the Sun.