https://en.wikipedia.org/wiki/Supernova_Cosmology_Project
https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Standard_candles
Standard candles
Almost all astronomical objects used as physical distance indicators belong to a class that has a known brightness. By comparing this known luminosity to an object's observed brightness, the distance to the object can be computed using the inverse-square law. These objects of known brightness are termed standard candles, coined by Henrietta Swan Leavitt.[13]
