When one asks, “Which is the brightest star in the night sky?” they tend to refer to the star that appears brightest to the ...

Cepheid variables are a type of star that undergo regular pulsations. The length of a Cepheid’s pulsations is always related to its intrinsic, or absolute, brightness in a simple way: The longer its ...

Hubble proved Andromeda is a separate galaxy by identifying a Cepheid variable star within it. Cepheid variables have a period-luminosity relationship: longer period means greater brightness. Knowing ...