Question

A Cephied is a star that belongs to a class of yellow supergiant pulsating stars; these stars vary periodically in brightness, and the relationship between their periods and ________ is useful in deriving distances to them

Answer 1

Luminosities

Thanks to this relationship between period and luminosity, a Cepheid provide a practical and accurate method to evaluate their absolute magnitude. Once this is known, it is possible to know the distance of the Cepheid, calculating the difference with respect to the apparent magnitude.