Cepheid Variables in NGC 5584

Cepheid variables can be sorted by their period of variability: how long it takes to return to the same brightness. The relationship between period intrinsic brightnessof the star is very important because it allows astronomers to determine the distance to the host galaxy, as long as they can measure a star's apparent brightness. Place your cursor over the below titles to see three groups of Cepheids of short (less than 30 days), medium (between 30 and 60 days), and long (more than 60 days) period for NGC 5584.