Variable Stars

Sometimes a star will change luminosity not due to an eclipse, but due to some sort of physical characteristic. These are called variable stars or variables . These changes in brightness can range from 1/1000 of a magnitude to 20 magnitudes over a period of a fraction of a second to many years. Over 150,000 variables are known, and many others are suspected to be variables.

There are two major classes of variable stars: Pulsating Variables and Cataclysmic Variables Pulsating variable stars swell and shrink, which affects the star’s brightness. One important class of pulsating variable stars is the Cepheid Variables .

This Hubble image shows RS Puppis, a type of variable star known as a Cepheid variable. As variable stars go, Cepheids have comparatively long periods— RS Puppis, for example, varies in brightness by almost a factor of five every 40 or so days. RS Puppis is unusual; this variable star is shrouded by thick, dark clouds of dust enabling a phenomenon known as a light echo to be shown with stunning clarity. These Hubble observations show the ethereal object embedded in its dusty environment, set against a dark sky filled with background galaxies.
Public Domain | Image courtesy of NASA.