Leavitt Law

Leavitt Law, also known as the period-luminosity relation, states that certain variable stars called Cepheid variables have a direct link between how long they take to brighten and dim (their period) and their true brightness (luminosity). Essentially, by measuring the period of a Cepheid’s brightness cycle, astronomers can determine how luminous it is. Comparing this to how bright it appears from Earth allows them to calculate how far away the star is. This relationship makes Cepheids vital for measuring distances across the universe, helping us understand cosmic scales.