[benjoffe]

A lot of research in astronomy is conducted to figure out how bright certain objects are, one classic example is "Cepheid variable" stars, these pulsate at a rate correlating with their brightness.

You're right in that there is sometimes debate about whether the "standard candles" as they're referred to are as bright as we expect, see: https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Problem...